Ni, Pd, Pt, and Ru complexes of phosphine-borate ligands

The species Cy(2)PHC(6)F(4)BF(C(6)F(5))(2) reacts with Pt(PPh(3))(4) to yield the new product cis-(PPh(3))(2)PtH(Cy(2)PC(6)F(4)BF(C(6)F(5))(2)) 1 via oxidative addition of the P-H bond of the phosphonium borate to Pt(0). The corresponding reaction with Pd(PPh(3))(4) affords the Pd analogue of 1, namely, cis-(PPh(3))(2)PdH(Cy(2)PC(6)F(4)BF(C(6)F(5))(2)) 3; while modification of the phosphonium borate gave the salt [(PPh(3))(3)PtH][(tBu(2)PC(6)F(4)BF(C(6)F(5))(2))] 2. Alternatively initial deprotonation of the phosphonium borate gave [tBu(3)PH][Cy(2)PC(6)F(4)BF(C(6)F(5))(2)] 4, [SIMesH][Cy(2)PC(6)F(4)BF(C(6)F(5))(2)] 5 which reacted with NiCl(2)(DME) yielding [BaseH](2)[trans-Cl(2)Ni(Cy(2)PC(6)F(4)BF(C(6)F(5))(2))(2)] (Base = tBu(3)P 6, SIMes 7) or with PdCl(2)(PhCN)(2) to give [BaseH](2)[trans-Cl(2)Pd(Cy(2)PC(6)F(4)BF(C(6)F(5))(2))(2)] (Base = tBu(3)P 8, SIMes 9). While [C(10)H(6)N(2)(Me)(4)H][tBu(2)PC(6)F(4)BF(C(6)F(5))(2)] 10 was also prepared. A third strategy for formation of a metal complex of anionic phosphine-borate derivatives was demonstrated in the reaction of (COD)PtMe(2) with the neutral phosphine-borane Mes(2)PC(6)F(4)B(C(6)F(5))(2) affording (COD)PtMe(Mes(2)PC(6)F(4)BMe(C(6)F(5))(2)) 11. Extension of this reactivity to tBu(2)PH(CH(2))(4)OB(C(6)F(5))(3)) was demonstrated in the reaction with Pt(PPh(3))(4) which yielded cis-(PPh(3))(2)PtH(tBu(2)P(CH(2))(4)OB(C(6)F(5))(3)) 12, while the reaction of [SIMesH][tBu(2)P(CH(2))(4)OB(C(6)F(5))(3)] 13 with NiCl(2)(DME) and PdCl(2)(PhCN)(2) afforded the complexes [SIMesH](2)[trans-Cl(2)Ni(tBu(2)PC(4)H(8)OB(C(6)F(5))(3))(2)] 14 and [SIMesH](2)[trans-PdCl(2)(tBu(2)P(CH(2))(4)OB(C(6)F(5))(3))(2)] 15, respectively, analogous to those prepared with 4 and 5. Finally, the reaction of 7 and 13with [(p-cymene)RuCl(2)](2) proceeds to give the new orange products [SIMesH][(p-cymene)RuCl(2)(Cy(2)PC(6)F(4)BF(C(6)F(5))(2))] 16 and [SIMesH][(p-cymene)RuCl(2)(tBu(2)P(CH(2))(4)OB(C(6)F(5))(3))] 17, respectively. Crystal structures of 1, 6, 10, 11, 12, and 16 are reported.     

Reactivity of the 16e (p-cymene)Ru half-sandwich complex containing a chelating 1,2-dicarba-closo-dodecaborane-1,2-dithiolate ligand towards diynes

The reactions of the 16e half-sandwich complex (p-cymene)Ru(S(2)C(2)B(10)H(10)) (Ru16e) with 1,4-diethynylbenzene (L1), 3',6-diethynyl-1,1'-binaphthyl-2,7'-diyl diacetate (L2), 2-bromo-5-ethynylthiophene (L3) and 2,5-diethynylthiophene (L4) lead to 18e mononuclear complexes (p-cymene)Ru(S(2)C(2)B(10)H(9))(H(2)CCPhC≡CH) (1), (p-cymene)Ru(S(2)C(2)B(10)H(9))[H(2)CC(C(24)H(16)O(4))C≡CH] (2), (p-cymene)Ru(S(2)C(2)B(10)H(9)) [H(2)CC(C(4)H(2)S)Br] (3) and (p-cymene)Ru(S(2)C(2)B(10)H(9)) [H(2)CC(C(4)H(2)S)C≡CH] (4), respectively. In all of them, metal-induced B-H activation has occurred, which leads to a stable Ru-B bond, and the structures take a cisoid arrangement. Only in the case of L4, the binuclear complexes [(p-cymene)Ru(S(2)C(2)B(10)H(9))](2)[H(2)CC(C(4)H(2)S)CCH(2)] (5a and 5b) are observed, which are conformational isomers generated by the differing orientations of the p-cymene unit. 4 can be readily converted to the complex (p-cymene)Ru(S(2)C(2)B(10)H(9))[H(2)CC(C(4)H(2)S)COCH(3)] (6) in the presence of silica and H(2)O. All of these products 1-6 were characterized by NMR, IR, elemental analysis and mass spectrometry. The structures of 1, 3, and 5a were also determined by single-crystal X-ray diffraction analysis.     

Solid state coordination chemistry: one-, two-, and three-dimensional materials constructed from molybdophosphonate subunits linked through binuclear copper tetra-2-pyridylpyrazine groups

The hydrothermal reactions of MoO(3), an appropriate Cu(II) source, tetra-2-pyridylpyrazine (tpypyz), and phosphoric acid and/or an organophosphonate yielded a series of organic-inorganic hybrid materials of the copper-molybdophosphonate family. A common feature of the structures is the entrainment within the extended architectures of chemically robust [Mo(5)O(15)(O(3)PR)(2)](4)(-) clusters as molecular building blocks. The cluster is a characteristic feature of the one-dimensional materials [[Cu(2)(tpypyz)(H(2)O)(3)]Mo(5)O(15)(HPO(4))(O(3)PCH(2)CO(2)H)].H(2)O (1.H(2)O) and [[Cu(2)(tpypyz)(H(2)O)]Mo(5)O(15)(O(3)PC(6)H(5))(2)].2H(2)O (2.2H(2)O), the two-dimensional network [[Cu(2)(tpypyz)(H(2)O)(3)]Mo(5)O(15)(HPO(4))(2)].2H(2)O (5.2H(2)O) and the three-dimensional frameworks [[Cu(2)(tpypyz)(H(2)O)(2)]Mo(5)O(15)[O(3)P(CH(2))(n)()PO(3)]].xH(2)O [n = 3, x = 2.25 (6.2.25H(2)O); n = 4, x = 0.33 (7.0.33H(2)O)]. In the case of methylenediphosphonate as the phosphorus component, the unique chelating nature of the ligand precludes formation of the pentamolybdate core, resulting in the chain structures [[Cu(2)(tpypyz)(H(2)O)]Mo(3)O(8) (HO(3)PCH(2)PO(3))(2)].8H(2)O (3.8H(2)O) and [[Cu(2)(tpypyz)(H(2)O)](2)(Mo(3)O(8))(2)(O(3)PCH(2)PO(3))(3)].16.9H(2)O (4.16.9H(2)O). For structures 1-7, the secondary metal-ligand building block is the binuclear [Cu(2)(tpypyz)(H(2)O)(x)](4+) cluster. There is considerable structural versatility as a result of the variability in the number of attachment sites at the phosphomolybdate clusters, the coordination geometry of the Cu(II), which may be four-, five-, or six-coordinate, the extent of aqua ligation, and the participation of phosphate oxygen atoms as well as molybdate oxo groups in bonding to the copper sites. Crystal data: 1.H(2)O, C(26)H(28)N(6)Cu(2)Mo(5)O(28)P(2), monoclinic C2/c, a = 42.497(2) A, b = 10.7421(4) A, c = 20.5617(8) A, beta = 117.178(1) degrees, V = 8350.1(5) A(3), Z = 8; 2.2H(2)O, C(36)H(32)N(6)Cu(2)Mo(5)O(24)P(2), monoclinic P2(1)/c, a = 11.2478(7) A, b = 19.513(1) A, c = 21.063(1) A, beta = 93.608(1) degrees, V = 4613.7(5) A(3), Z = 4; 3.8H(2)O, C(26)H(40)N(6)Cu(2)Mo(3)O(29)P(4), monoclinic C2/c, a = 32.580(2) A, b = 17.8676(9) A, c = 15.9612(8) A, beta = 104.430(1) degrees, V = 8993.3(8) A(3), Z = 8; 4.16.9H(2)O, C(51)H(71.75)Cu(4)Mo(6)N(12)O(51)P(6), monoclinic P2(1)/c, a = 27.929(3) A, b = 12.892(2) A, c = 22.763(3) A, beta = 90.367(2) degrees, V = 8195.7(2) A(3), Z = 4;( )()5.2H(2)O, C(24)H(28)N(6)Cu(2)Mo(5)O(28)P(2), monoclinic P2(1)/n, a = 11.3222(4) A, b = 18.7673(7) A, c = 19.4124(7) A, beta = 98.819(1) degrees, V = 4076.1(3) A(3), Z = 4; 6.2.25H(2)O, C(27)H(28.5)N(6)Cu(2)Mo(5)O(24.25)P(2), monoclinic C2/c, a = 12.8366(5) A, b = 18.4221(8) A, c = 34.326(1) A, beta = 100.546(1) degrees, V = 7980.1(6) A(3), Z = 8; 7.(1)/(3)H(2)O, C(28)H(28.7)N(6)Cu(2)Mo(5)O(23.3)P(2), monoclinic C2/c, a = 12.577(1) A, b = 18.336(1) A, c = 36.476(3) A, beta = 91.929(2) degrees, V = 8407.3 A(3), Z = 8.     

How large is the static electric (hyper)polarizability anisotropy in HXeI?

An extensive conventional ab initio and density functional theory investigation reveals that HXeI is a polar molecule with large multipole moments and highly anisotropic (hyper)polarizability. At the CCSD(T) level of theory our best values for the mean (hyper)polarizability are alphae(2)a(0) (2)E(h) (-1)=101.46, betae(3)a(0) (3)E(h) (-2)=-850.7, and gammae(4)a(0) (4)E(h) (-3)=18.7x10(3). The corresponding anisotropies are Deltaalphae(2)a(0) (2)E(h) (-1)=119.66, Deltabetae(3)a(0) (3)E(h) (-2)=-2518.7, Delta(1)gammae(4)a(0) (4)E(h) (-3)=-249.1x10(3), and Delta(2)gammae(4)a(0) (4)E(h) (-3)=-99.6x10(3). The longitudinal components of the (hyper)polarizability are dominant. Our value for the anisotropy of the dipole polarizability is considerably larger than the recent empirical estimate of 22.9 e(2)a(0) (2)E(h) (-1) [N. H. Nahler et al., J. Chem. Phys. 119, 224 (2003)]. The results of the insertion of Xe into HI are quantified by the calculation of the differential (hyper)polarizability at the MP2 level of theory: alpha(diff) identical withalpha(HXeI)-alpha(HI)-alpha(Xe)=36.29 e(2)a(0) (2)E(h) (-1) and gamma(diff) identical with gamma(HXeI)-gamma(HI)-gamma(Xe)=18.1x10(3) e(4)a(0) (4)E(h) (-3).     

Regioselective functionalization of iminophosphoranes through Pd-mediated C-H bond activation: C-C and C-X bond formation

The orthopalladation of iminophosphoranes [R(3)P=N-C(10)H(7)-1] (R(3) = Ph(3) 1, p-Tol(3) 2, PhMe(2) 3, Ph(2)Me 4, N-C(10)H(7)-1 = 1-naphthyl) has been studied. It occurs regioselectively at the aryl ring bonded to the P atom in 1 and 2, giving endo-[Pd(μ-Cl)(C(6)H(4)-(PPh(2=N-1-C(10)H(7))-2)-κ-C,N](2) (5) or endo-[Pd(μ-Cl)(C(6)H(3)-(P(p-Tol)(2)=N-C(10)H(7)-1)-2-Me-5)-κ-C,N](2) (6), while in 3 the 1-naphthyl group is metallated instead, giving exo-[Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7). In the case of 4, orthopalladation at room temperature affords the kinetic exo isomer [Pd(μ-Cl)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (11exo), while a mixture of 11exo and the thermodynamic endo isomer [Pd(μ-Cl)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (11endo) is obtained in refluxing toluene. The heating in toluene of the acetate bridge dimer [Pd(μ-OAc)(C(10)H(6)-(N=PPh(2)Me)-8)-κ-C,N](2) (13exo) promotes the facile transformation of the exo isomer into the endo isomer [Pd(μ-OAc)(C(6)H(4)-(PPhMe=N-C(10)H(7)-1)-2)-κ-C,N](2) (13endo), confirming that the exo isomers are formed under kinetic control. Reactions of the orthometallated complexes have led to functionalized molecules. The stoichiometric reactions of the orthometallated complexes [Pd(μ-Cl)(C(10)H(6)-(N=PPhMe(2))-8)-κ-C,N](2) (7), [Pd(μ-Cl)(C(6)H(4)-(PPh(2)[=NPh)-2)](2) (17) and [Pd(μ-Cl)(C(6)H(3)-(C(O)N=PPh(3))-2-OMe-4)](2) (18) with I(2) or with CO results in the synthesis of the ortho-halogenated compounds [PhMe(2)P=N-C(10)H(6)-I-8] (19), [I-C(6)H(4)-(PPh(2)=NPh)-2] (21) and [Ph(3)P=NC(O)C(6)H(3)-I-2-OMe-5] (23) or the heterocycles [C(10)H(6)-(N=PPhMe(2))-1-(C(O))-8]Cl (20), [C(6)H(5)-(N=PPh(2)-C(6)H(4)-C(O)-2]ClO(4) (22) and [C(6)H(3)-(C(O)-1,2-N-PPh(3))-OMe-4]Cl (24).     

Kinetic and donor stabilization of organotellurenyl iodides and azides

The first tellurium compounds containing the extremely bulky tris(phenyldimethylsilyl)methyl (Tpsi) and 2,6-bis(2,4,6-triisopropylphenyl)phenyl (2,6-Trip(2)C(6)H(3)) moieties have been synthesized and isolated. Careful oxidation of the tellurolate TpsiTeLi (1) resulted in the formation of the crowded ditellane (TpsiTe)(2) (2), and iodination of 2 gave the alkanetellurenyl iodide TpsiTeI (3). In a similar fashion, the terphenyl-substituted ditellane (2,6-Trip(2)C(6)H(3)Te)(2) (9) and the arenetellurenyl iodide 2,6-Trip(2)C(6)H(3)TeI (10) were prepared. Reaction of the iodides TpsiTeI (3) and 2,6-Trip(2)C(6)H(3)TeI (10), as well as TripTeI, MesTeI (Trip = 2,4,6-triisopropylphenyl, Mes = 2,4,6-tri-tert-butylphenyl), and the donor-stabilized 2-Me(2)NCH(2)C(6)H(4)TeI, with AgN(3) resulted in the formation and isolation of the corresponding tellurenyl azides TpsiTeN(3) (4), TripTeN(3) (7), MesTeN(3) (8), 2,6-Trip(2)C(6)H(3)TeN(3) (11), and 2-Me(2)NCH(2)C(6)H(4)TeN(3) (12). Furthermore, the corresponding tris(ethyldimethylsilyl)methyl-containing (Tesi) tellurium compounds (TesiTe)(2), TesiTeI (5), and TesiTeN(3) (6) have been prepared but could not be isolated in pure form. The crystal structures of TpsiTeLi (1), (TpsiTe)(2) (2), TpsiTeN(3) (4), 2,6-Trip(2)C(6)H(3)TeI (10), 2,6-Trip(2)C(6)H(3)TeN(3) (11), and 2-Me(2)NCH(2)C(6)H(4)TeN(3) (12) have been determined by X-ray diffraction. Additionally, computational studies of the molecules for which experimental structural data were available were performed.     

Atmospheric chemistry of two biodiesel model compounds: methyl propionate and ethyl acetate

The atmospheric chemistry of two C(4)H(8)O(2) isomers (methyl propionate and ethyl acetate) was investigated. With relative rate techniques in 980 mbar of air at 293 K the following rate constants were determined: k(C(2)H(5)C(O)OCH(3) + Cl) = (1.57 ± 0.23) × 10(-11), k(C(2)H(5)C(O)OCH(3) + OH) = (9.25 ± 1.27) × 10(-13), k(CH(3)C(O)OC(2)H(5) + Cl) = (1.76 ± 0.22) × 10(-11), and k(CH(3)C(O)OC(2)H(5) + OH) = (1.54 ± 0.22) × 10(-12) cm(3) molecule(-1) s(-1). The chlorine atom initiated oxidation of methyl propionate in 930 mbar of N(2)/O(2) diluent (with, and without, NO(x)) gave methyl pyruvate, propionic acid, acetaldehyde, formic acid, and formaldehyde as products. In experiments conducted in N(2) diluent the formation of CH(3)CHClC(O)OCH(3) and CH(3)CCl(2)C(O)OCH(3) was observed. From the observed product yields we conclude that the branching ratios for reaction of chlorine atoms with the CH(3)-, -CH(2)-, and -OCH(3) groups are <49 ± 9%, 42 ± 7%, and >9 ± 2%, respectively. The chlorine atom initiated oxidation of ethyl acetate in N(2)/O(2) diluent gave acetic acid, acetic acid anhydride, acetic formic anhydride, formaldehyde, and, in the presence of NO(x), PAN. From the yield of these products we conclude that at least 41 ± 6% of the reaction of chlorine atoms with ethyl acetate occurs at the -CH(2)- group. The rate constants and branching ratios for reactions of OH radicals with methyl propionate and ethyl acetate were investigated theoretically using transition state theory. The stationary points along the oxidation pathways were optimized at the CCSD(T)/cc-pVTZ//BHandHLYP/aug-cc-pVTZ level of theory. The reaction of OH radicals with ethyl acetate was computed to occur essentially exclusively (～99%) at the -CH(2)- group. In contrast, both methyl groups and the -CH(2)- group contribute appreciably in the reaction of OH with methyl propionate. Decomposition via the α-ester rearrangement (to give C(2)H(5)C(O)OH and a HCO radical) and reaction with O(2) (to give CH(3)CH(2)C(O)OC(O)H) are competing atmospheric fates of the alkoxy radical CH(3)CH(2)C(O)OCH(2)O. Chemical activation of CH(3)CH(2)C(O)OCH(2)O radicals formed in the reaction of the corresponding peroxy radical with NO favors the α-ester rearrangement.     

Nucleophilic di- and tetrafluorination of dicarbonyl compounds

Reactions of various diketo compounds with Deoxofluor [(CH(3)OCH(2)CH(2))(2)NSF(3)] have been investigated. When reacted with Deoxofluor, alpha-diketones, R(1)COCOR(2) (R(1) = R(2) = Ph; R(1) = R(2) = 4-Me-C(6)H(4); R(1) = Ph, R(2) = Me; R(1) = Me, R(2) = Et) (1a-d) formed difluoro derivatives (2a-d) in the presence of a catalytic amount of HF and/or tetrafluoro (3a-d) products depending on the reaction conditions and stoichiometry used. Reactions of beta-diketones, R(3)COCH(2)COR(4) (R(3) = R(4) = Ph; R(3) = R(4) = Me; R(3) = Me, R(4) = Ph) (4e-g), with Deoxofluor in the presence of a catalytic amount of HF led to the formation of difluoroalkenones as a mixture of E (5e-g) and Z (6e-g) isomers in good yield. Reaction of other diones, R(5)CO-X-COR(6) (R(5) = R(6) = Ph, X = -CH=CH-; R(5) = R(6) = Me, X = -C(6)H(4)C(6)H(4)-; R(5) = R(6) = Ph, X = -CH(2)CH(2)CH(2)-; R(5) = R(6) = Me, X = -CH(2)CH(2)-) (7h-k) with Deoxofluor produced mainly difluoro products (8h-k) with low yields of tertrafluoro derivatives (9h-k). Acyclic alpha-keto amides react poorly to give the corresponding difluoro derivatives, whereas cyclic alpha-keto amides (10l-p) react smoothly under very mild conditions to produce the corresponding difluoro products (11l-p) in >88% isolated yield.     

Deviation between the chemistry of Ce(IV) and Pu(IV) and routes to ordered and disordered heterobimetallic 4f/5f and 5f/5f phosphonates

The heterobimetallic actinide compound UO(2)Ce(H(2)O)[C(6)H(4)(PO(3)H)(2)](2)·H(2)O was prepared via the hydrothermal reaction of U(VI) and Ce(IV) in the presence of 1,2-phenylenediphosphonic acid. We demonstrate that this is a kinetic product that is not stable with respect to decomposition to the monometallic compounds. Similar reactions have been explored with U(VI) and Ce(III), resulting in the oxidation of Ce(III) to Ce(IV) and the formation of the Ce(IV) phosphonate, Ce[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O, UO(2)Ce(H(2)O)[C(6)H(4)(PO(3)H)(2)](2)·H(2)O, and UO(2)[C(6)H(4)(PO(3)H)(2)](H(2)O)·H(2)O. In comparison, the reaction of U(VI) with Np(VI) only yields Np[C(6)H(4)(PO(3)H)(2)](2)·2H(2)O and aqueous U(VI), whereas the reaction of U(VI) with Pu(VI) yields the disordered U(VI)/Pu(VI) compound, (U(0.9)Pu(0.1))O(2)[C(6)H(4)(PO(3)H)(2)](H(2)O)·H(2)O, and the Pu(IV) phosphonate, Pu[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O. The reactions of Ce(IV) with Np(VI) yield disordered heterobimetallic phosphonates with both M[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O (M = Ce, Np) and M[C(6)H(4)(PO(3)H)(2)](2)·2H(2)O (M = Ce, Np) structures, as well as the Ce(IV) phosphonate Ce[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O. Ce(IV) reacts with Pu(IV) to yield the Pu(VI) compound, PuO(2)[C(6)H(4)(PO(3)H)(2)](H(2)O)·3H(2)O, and a disordered heterobimetallic Pu(IV)/Ce(IV) compound with the M[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O (M = Ce, Pu) structure. Mixtures of Np(VI) and Pu(VI) yield disordered heterobimetallic Np(IV)/Pu(IV) phosphonates with both the An[C(6)H(4)(PO(3)H)(PO(3)H(2))][C(6)H(4)(PO(3)H)(PO(3))]·2H(2)O (M = Np, Pu) and An[C(6)H(4)(PO(3)H)(2)](2)·2H(2)O (M = Np, Pu) formulas.     

Energetics of cresols and of methylphenoxyl radicals

Combustion calorimetry studies were used to determine the standard molar enthalpies of formation of o-, m-, and p-cresols, at 298.15 K, in the condensed state as Delta(f)H(m) degrees (o-CH(3)C(6)H(4)OH,cr) = -204.2 +/- 2.7 kJ.mol(-1), Delta(f)H(m) degrees (m-CH(3)C(6)H(4)OH,l) = -196.6 +/- 2.1 kJ.mol(-1), and Delta(f)H(m) degrees (p-CH(3)C(6)H(4)OH,cr) = -202.2 +/- 3.0 kJ.mol(-1). Calvet drop calorimetric measurements led to the following enthalpy of sublimation and vaporization values at 298.15 K: Delta(sub)H(m) degrees (o-CH(3)C(6)H(4)OH) = 73.74 +/- 0.46 kJ.mol(-1), Delta(vap)H(m) degrees (m-CH(3)C(6)H(4)OH) = 64.96 +/- 0.69 kJ.mol(-1), and Delta(sub)H(m) degrees (p-CH(3)C(6)H(4)OH) = 73.13 +/- 0.56 kJ.mol(-1). From the obtained Delta(f)H(m) degrees (l/cr) and Delta(vap)H(m) degrees /Delta(sub)H(m) degrees values, it was possible to derive Delta(f)H(m) degrees (o-CH(3)C(6)H(4)OH,g) = -130.5 +/- 2.7 kJ.mol(-1), Delta(f)H(m) degrees (m-CH(3)C(6)H(4)OH,g) = -131.6 +/- 2.2 kJ.mol(-1), and Delta(f)H(m) degrees (p-CH(3)C(6)H(4)OH,g) = -129.1 +/- 3.1 kJ.mol(-1). These values, together with the enthalpies of isodesmic and isogyric gas-phase reactions predicted by the B3LYP/cc-pVDZ, B3LYP/cc-pVTZ, B3P86/cc-pVDZ, B3P86/cc-pVTZ, MPW1PW91/cc-pVTZ, CBS-QB3, and CCSD/cc-pVDZ//B3LYP/cc-pVTZ methods, were used to obtain the differences between the enthalpy of formation of the phenoxyl radical and the enthalpies of formation of the three methylphenoxyl radicals: Delta(f)H(m) degrees (C(6)H(5)O*,g) - Delta(f)H(m) degrees (o-CH(3)C(6)H(4)O*,g) = 42.2 +/- 2.8 kJ.mol(-1), Delta(f)H(m) degrees (C(6)H(5)O*,g) - Delta(f)H(m) degrees (m-CH(3)C(6)H(4)O*,g) = 36.1 +/- 2.4 kJ.mol(-1), and Delta(f)H(m) degrees (C(6)H(5)O*,g) - Delta(f)H(m) degrees (p-CH(3)C(6)H(4)O*,g) = 38.6 +/- 3.2 kJ.mol(-1). The corresponding differences in O-H bond dissociation enthalpies were also derived as DH degrees (C(6)H(5)O-H) - DH degrees (o-CH(3)C(6)H(4)O-H) = 8.1 +/- 4.0 kJ.mol(-1), DH degrees (C(6)H(5)O-H) - DH degrees (m-CH(3)C(6)H(4)O-H) = 0.9 +/- 3.4 kJ.mol(-1), and DH degrees (C(6)H(5)O-H) - DH degrees (p-CH(3)C(6)H(4)O-H) = 5.9 +/- 4.5 kJ.mol(-1). Based on the differences in Gibbs energies of formation obtained from the enthalpic data mentioned above and from published or calculated entropy values, it is concluded that the relative stability of the cresols varies according to p-cresol < m-cresol < o-cresol, and that of the radicals follows the trend m-methylphenoxyl < p-methylphenoxyl < o-methylphenoxyl. It is also found that these tendencies are enthalpically controlled.     

(Salen)tin complexes: syntheses, characterization, crystal structures, and catalytic activity in the formation of propylene carbonate from CO(2) and propylene oxide

A series of (salen)tin(II) and (salen)tin(IV) complexes was synthesized. The (salen)tin(IV) complexes, (salen)SnX(2) (X = Br and I), were prepared in good yields via the direct oxidation reaction of (salen)tin(II) complexes with Br(2) or I(2). (Salen)SnX(2) successfully underwent the anion-exchange reaction with AgOTf (OTf = trifluoromethanesulfonate) to form (salen)Sn(OTf)(2) and (salen)Sn(X)(OTf) (X = Br). The (salen)Sn(OTf)(2) complex was easily converted to any of the dihalide (salen)SnX(2) compounds using halide salts. All complexes were fully characterized by (1)H NMR spectroscopy, mass spectrometry, and elemental analysis, while some were characterized by (13)C, (19)F, and (119)Sn NMR spectroscopy. Several crystal structures of (salen)tin(II) and (salen)tin(IV) were also determined. Finally, both (salen)tin(II) and (salen)tin(IV) complexes were shown to efficiently catalyze the formation of propylene carbonate from propylene oxide and CO(2). Of the series, (3,3',5,5'-Br(4)-salen)SnBr(2), 3i, was found to be the most effective catalyst (TOF = 524 h(-)(1)).     

Mono-, di-, and tricoordinated phosphorus attached to a N-N unit: an experimental and theoretical study

N,N',N'-[Tris(trimethylsilyl)]hydrazino-diphenylphosphane, (TMS)2 N-(TMS)N-PPh2 (1), and N,N',N'-[tris(trimethylsilyl)]hydrazino-phenyl(chloro)phosphane, (TMS)2 N-(TMS)N-P(Cl)Ph2 (2), were obtained in the reaction of bis-[lithium-tris(trimethylsilyl)hydrazide] with Ph(n)PCl(3 - n) (n = 1, 2). The structure and bonding of both species are discussed on the basis of experimentally observed (X-ray, Raman, NMR, and MS) and theoretically obtained data (B3LYP/6-31G(d,p), NBO analysis). Oxidation with sulfur and selenium results in the formation of (TMS)2 N-(TMS)N-P(S)Ph2 (4), (TMS)2 N-(TMS)N-P(Se)Ph2 (5), (TMS)2 N-(TMS)N-P(S)Ph(Cl) (6), and (TMS)2 N-(TMS)N-P(Se)Ph(Cl) (7). Moreover, the thermal decomposition of N,N',N'-[tris(trimethylsilyl)]hydrazine-dichlorophosphane, (TMS)2 N-(TMS)N-PCl2 (3) and the reaction with magnesium have been investigated. The formation and molecular structure of the novel MgCl2(THF)2 x 2Mg[(TMS)NP(O)2 N(TMS)2](THF) (8) salt containing the hitherto unknown (TMS)NP(O)2 N(TMS)2(2-) anion are discussed. DFT calculations (B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d,p)) are used to evaluate the bonding, ground-state structures, and energy landscape for the different isomers of 3: the thermodynamics and kinetics of the successive elimination of chlorotrimethylsilane (TMS-Cl) resulting in the formation of covalent azide analogues such as TMS-PNN or TMS-NNP.     

Coordination Chemistry of 2,2'-Dipyridyl Diselenide: X-ray Crystal Structures of PySeSePy, [Zn(PySeSePy)Cl(2)], [(PySeSePy)Hg(C(6)F(5))(2)], [Mo(SePy)(2)(CO)(3)], [W(SePy)(2)(CO)(3)], and [Fe(SePy)(2)(CO)(2)] (PySeSePy = C(5)H(4)NSeSeC(5)H(4)N; SePy = [C(5)H(4)N(2-Se)-N,Se])

The coordination chemistry of 2,2'-dipyridyl diselenide (PySeSePy) (2) (C(10)H(8)N(2)Se(2)) has been investigated and its crystal structure has been determined (monoclinic, P2(1)/c, a = 10.129(2) ?, b = 5.7332(12) ?, c = 19.173(3) ?, beta = 101.493(8) degrees, Z = 4). In metal complexes the ligand was found to coordinate in three different modes, as also confirmed by X-ray structure determination. N,N'-coordination was found in the zinc complex [Zn(PySeSePy)Cl(2)] (3) (C(10)H(8)Cl(2)N(2)Se(2)Zn, triclinic, P&onemacr;, a = 7.9430(10) ?, b = 8.147(2) ?, c = 11.999(2) ?, alpha = 93.685(10) degrees, beta = 107.763(10) degrees, gamma = 115.440(10) degrees, Z = 2) and Se,Se'-coordination in the adduct of the ligand with bis(pentafluorophenyl)mercury(II) [PySeSePyHg(C(6)F(5))(2)] (5) (C(10)H(8)F(10)HgN(2)Se(2), monoclinic, P2(1)/n, a = 7.7325(10) ?, b = 5.9974(14) ?, c = 25.573, beta = 98.037(10) degrees, Z = 2), which however displays only weak interactions between selenium and mercury. The reaction of the ligand with norbornadiene carbonyl complexes of molybdenum and tungsten leads to reductive cleavage of the selenium-selenium bond with oxidation of the metal center and concomitant addition of the resulting selenolate to the metal carbonyl fragment. Thus the 7-coordinate complexes [Mo(SePy)(2)(CO)(3)] (6) (C(13)H(8)MoN(2)O(3)Se(2), monoclinic, P2(1)/n, a = 9.319(3) ?, b = 12.886(5) ?, c = 13.231(6) ?, beta = 109.23(3) degrees, Z = 4) and [W(SePy)(2)(CO)(3)] (7) (C(13)H(8)N(2)O(3)Se(2)W, monoclinic, P2(1)/n, a = 9.303(2) ?, b = 12.853(2) ?, c = 13.232(2) ?, beta = 109.270(10) degrees, Z = 4) were obtained. The same N,Se-coordination pattern emerges from the reaction of [Fe(2)(CO)(9)] with (2) leading to [Fe(SePy)(2)(CO)(2)] (8) (C(12)H(8)FeN(2)O(2)Se(2), monoclinic, P&onemacr;, a = 8.6691(14) ?, b = 12.443(2) ?, c = 14.085(2) ?, alpha = 105.811(10) degrees, beta = 107.533(8) degrees, gamma = 92.075(10) degrees, Z = 4).     

Multifunctional Ligands. Phosphinimine-Substituted Cyanofluoroaromatics Including X-ray Molecular Structures of Three Representative Ligands 4,6-(CN)(2)C(6)F(2)-1,3-(N=PPh(3))(2), 4,6-(CN)(2)C(6)F(2)-1,3-(N=PPh(2)Me)(2) and 4,6-(CN)(2)C(6)F(2)-1-(N=PPh(3))-3-(N=PPh(2)Me). Formation of Rhodium(I) Complexes

Reaction of 1,3-dicyanotetrafluorobenzene with 2 equiv of (trimethylsilyl)iminophosphoranes gave the disubstituted derivatives 4,6-(CN)(2)C(6)F(2)-1,3-AB: 1, A = B = (N=PPh(3)); 2, A = B = (N=PPh(2)Me); and 3, A = (N=PPh(3)), B = (N=PPh(2)Me). Monosubstituted compounds of the type 2,4-(CN)(2)C(6)F(3)-1-A; notably 4, A = (N=PPh(3)), and 5, A = (N=PPh(2)Me), were readily obtained by reaction of 1 molar equiv of the silylated iminophosphorane with the cyanofluoro aromatic. Substitution of the fluorine para to the CN group(s) occurs in all cases. Reactions of 1,2- and 1,4-dicyanotetrafluorobenzene with (trimethylsilyl)iminophosphoranes gave only monosubstituted derivatives 3,4-(CN)(2)C(6)F(3)-1-A (6, A = (N=PPh(3)), and 7, A = (N=PPh(2)Me)) and 2,5-(CN)(2)C(6)F(3)-1-A (8, A = (N=PPh(3)), and 9, A = (N=PPh(2)Me)), respectively, as the result of electronic deactivation of the second substitutional point. 1, 4,6-(CN)(2)C(6)F(2)-1,3-(N=PPh(3)), 2, 4,6-(CN)(2)C(6)F(2)-1,3-(N=PPh(2)Me)(2), and 3, 4,6-(CN)(2)C(6)F(2)-1-(N=PPh(3))-3-(N=PPh(2)Me) have been structurally characterized. For 1 (at 21 degrees C), monoclinic, C2/(c) (No. 15), a = 15.289(2) ?, b = 10.196(1) ?, c = 23.491(6) ?, beta = 91.63(2) degrees, V = 3660(2) ?(3), and Z = 4. The P=N bond length is 1.579(2) ? and the P(V)-N-C(phenyl) angle is 134.0(2) degrees. For 2, (at 21 degrees C) monoclinic, C2/(c) (No. 15), a = 18.694(2) ?, b = 8.576(1) ?, c = 40.084(4) ?, beta = 94.00(1) degrees, V = 6411(2) ?(3), and Z = 8. The P(1)=N(1) bond length is 1.570(4) ?, the P(2)=N(2) bond length is 1.589(3) ?, the P(1)-N(1)-C(14) angle is 131.6(3) degrees, and the P(2)-N(2)-C(16) angle is 131.3(3) degrees. For 3, (at -80 degrees C) monoclinic, P2(1)/c (No. 14), a = 9.210(1) ?, b = 18.113(2) ?, c = 20.015(2) ?, beta = 100.07(1) degrees, V = 3287(2) ?(3), and Z = 4. The P(1)=N(1) bond length (PPh(3) group) is 1.567(4) ?, the P(2)=N(2) bond length (PPh(2)Me group) is 1.581(5) ?, the P(1)-N(1)-C(1) angle is 140.4(4) degrees, and the P(2)-N(2)-C(3) angle is 129.4(4) degrees. These new multifunctional chelating ligands readily react with [Rh(cod)Cl](2) and AgClO(4) to give cationic Rh(I) complexes in which the imine and/or the nitrile groups are coordinated to the Rh center.     

Unimolecular rate constants for HX or DX elimination (X = F, Cl) from chemically activated CF3CH2CH2Cl, C2H5CH2Cl, and C2D5CH2Cl: threshold energies for HF and HCl elimination

Vibrationally activated CF(3)CH(2)CH(2)Cl molecules were prepared with 94 kcal mol(-1) of vibrational energy by the combination of CF(3)CH(2) and CH(2)Cl radicals and with 101 kcal mol(-1) of energy by the combination of CF(3) and CH(2)CH(2)Cl radicals at room temperature. The unimolecular rate constants for elimination of HCl from CF(3)CH(2)CH(2)Cl were 1.2 x 10(7) and 0.24 x 10(7) s(-1) with 101 and 94 kcal mol(-1), respectively. The product branching ratio, k(HCl)/k(HF), was 80 +/- 25. Activated CH(3)CH(2)CH(2)Cl and CD(3)CD(2)CH(2)Cl molecules with 90 kcal mol(-1) of energy were prepared by recombination of C(2)H(5) (or C(2)D(5)) radicals with CH(2)Cl radicals. The unimolecular rate constant for HCl elimination was 8.7 x 10(7) s(-1), and the kinetic isotope effect was 4.0. Unified transition-state models obtained from density-functional theory calculations, with treatment of torsions as hindered internal rotors for the molecules and the transition states, were employed in the calculation of the RRKM rate constants for CF(3)CH(2)CH(2)Cl and CH(3)CH(2)CH(2)Cl. Fitting the calculated rate constants from RRKM theory to the experimental values provided threshold energies, E(0), of 58 and 71 kcal mol(-1) for the elimination of HCl or HF, respectively, from CF(3)CH(2)CH(2)Cl and 54 kcal mol(-1) for HCl elimination from CH(3)CH(2)CH(2)Cl. Using the hindered-rotor model, threshold energies for HF elimination also were reassigned from previously published chemical activation data for CF(3)CH(2)CH(3,) CF(3)CH(2)CF(3), CH(3)CH(2)CH(2)F, CH(3)CHFCH(3), and CH(3)CF(2)CH(3). In an appendix, the method used to assign threshold energies was tested and verified using the combined thermal and chemical activation data for C(2)H(5)Cl, C(2)H(5)F, and CH(3)CF(3).     

Thermal activation of hydrocarbon C-H bonds initiated by a tungsten allyl complex

Gentle thermolysis of the allyl complex, CpW(NO)(CH(2)CMe(3))(eta(3)-H(2)CCHCMe(2)) (1), at 50 degrees C in neat hydrocarbon solutions results in the loss of neopentane and the generation of transient intermediates that subsequently activate solvent C-H bonds. Thus, thermal reactions of 1 with tetramethylsilane, mesitylene, and benzene effect single C-H activations and lead to the exclusive formation of CpW(NO)(CH(2)SiMe(3))(eta(3)-H(2)CCHCMe(2)) (2), CpW(NO)(CH(2)C(6)H(3)-3,5-Me(2))(eta(3)-H(2)CCHCMe(2)) (3), and CpW(NO)(C(6)H(5))(eta(3)-H(2)CCHCMe(2)) (4), respectively. The products of reactions of 1 with other methyl-substituted arenes indicate an inherent preference of the system for the activation of stronger arene sp(2) C-H bonds. For example, C-H bond activation of p-xylene leads to the formation of CpW(NO)(CH(2)C(6)H(4)-4-Me)(eta(3)-H(2)CCHCMe(2)) (5) (26%) and CpW(NO)(C(6)H(3)-2,5-Me(2))(eta(3)-H(2)CCHCMe(2)) (6) (74%). Mechanistic and labeling studies indicate that the transient C-H-activating intermediates are the allene complex, CpW(NO)(eta(2)-H(2)C=C=CMe(2)) (A), and the eta(2)-diene complex, CpW(NO)(eta(2)-H(2)C=CHC(Me)=CH(2)) (B). Intermediates A and B react with cyclohexene to form CpW(NO)(eta(3)-CH(2)C(2-cyclohexenyl)CMe(2))(H) (18) and CpW(NO)(eta(3)-CH(2)CHC)(Me)CH(2)C(beta)H(C(4)H(8))C(alpha)H (19), respectively, and intermediate A can be isolated as its PMe(3) adduct, CpW(NO)(PMe(3))(eta(2)-H(2)C=C=CMe(2)) (20). Interestingly, thermal reaction of 1 with 2,3-dimethylbut-2-ene results in the formation of a species that undergoes eta(3) --> eta(1) isomerization of the dimethylallyl ligand following the initial C-H bond-activating step to yield CpW(NO)(eta(3)-CMe(2)CMeCH(2))(eta(1)-CH(2)CHCMe(2)) (21). Thermolyses of 1 in alkane solvents afford allyl hydride complexes resulting from three successive C-H bond-activation reactions. For instance, 1 in cyclohexane converts to CpW(NO)(eta(3)-C(6)H(9))(H) (22) with dimethylpropylcyclohexane being formed as a byproduct, and in methylcyclohexane it forms the two isomeric complexes, CpW(NO)(eta(3)-C(7)H(11))(H) (23a,b). All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2, 3, 4, 18, 19, 20, and 21 have been established by X-ray crystallographic analyses.     

Structure, stability, and spectra of C9H3, C11H3, and C13H3 radicals

Density functional theory has been used to investigate the geometries, vibrational frequencies, rotational constants, and dipole moments of the C(9)H(3), C(11)H(3), and C(13)H(3) radicals. Vertical electronic transition energies of C(9)H(3), C(11)H(3), and C(13)H(3) are calculated by the time-dependent density functional theory. Present results show that the most stable arrangements of C(9)H(3), C(11)H(3), and C(13)H(3) are H(2)C(9)H, H(2)C(11)H, and H(2)C(13)H with a C(2v) symmetry, respectively. Such lowest-energy isomers have an obvious single and triple bond alternation carbon chain. Their isomers HC(4)(HC)C(4)H, HC(4)[C(C(2)H)]C(4)H, and C(C(4)H)(3) are predicted to have vibrational frequencies and vertical excitation energies in good agreement with experimental observations. HC(4)(HC)C(4)H, HC(4)[C(C(2)H)]C(4)H, and C(C(4)H)(3) have similar trigonal structure, which gives rise to the remarkably similar spectroscopic features as obtained experimentally. On the basis of present calculations, the isomers HC(4)(HC)C(4)H, HC(4)[C(C(2)H)]C(4)H, and C(C(4)H)(3) of C(9)H(3), C(11)H(3), and C(13)H(3) radicals are most likely the carriers of the observed spectra.     

Syntheses, crystal structures, and magnetic properties of the oxalato-bridged mixed-valence complexes (FeII(bpm)3]2[FeIII2(ox)5].8H2O and FeII(bpm)3Na(H2O)2Fe(ox)(3).4H2O (bpm = 2,2'-bipyrimidine)

The preparation and crystal structures of two oxalato-bridged FeII-FeIII mixed-valence compounds, [FeII(bpm)3]2[FeIII2(ox)5].8H2O (1) and FeII(bpm)3Na(H2O)2FeIII(ox)(3).4H2O (2) (bpm = 2,2'-bipyrimidine; ox = oxalate dianion) are reported here. Complex 1 crystallizes in the triclinic system, space group P1, with a = 10.998(2) A, b = 13.073(3) A, c = 13.308(3) A, alpha = 101.95(2) degrees, beta = 109.20(2) degrees, gamma = 99.89(2) degrees, and Z = 1. Complex 2 crystallizes in the monoclinic system, space group P2(1)/c, with a = 12.609(2) A, b = 19.670(5) A, c = 15.843(3) A, beta = 99.46(1) degrees, and Z = 4. The structure of complex 1 consists of centrosymmetric oxalato-bridged dinuclear high-spin iron(III) [Fe2(ox)5]2- anions, tris-chelated low-spin iron(II) [Fe(bpm)3]2+ cations, and lattice water molecules. The iron atoms are hexacoordinated: six oxygen atoms (iron(III)) from two bidentate and one bisbidentate oxalato ligands and six nitrogen atoms (iron(II)) from three bidentate bpm groups. The Fe(III)-O(ox) and Fe(II)-N(bpm) bond distances vary in the ranges 1.967(3)-2.099(3) and 1.967(4)-1.995(3) A, respectively. The iron(III)-iron(III) separation across the bridging oxalato is 5.449(2) A, whereas the shortest intermolecular iron(III)-iron(II) distance is 6.841(2) A. The structure of complex 2 consists of neutral heterotrinuclear Fe(bpm)2Na(H2O)2Fe(ox)3 units and water molecules of crystallization. The tris-chelated low-spin iron(II) ([Fe(bpm)3]2+) and high-spin iron(III) ([Fe(ox)3]3-) entities act as bidentate ligands (through two bpm-nitrogen and two oxalato-oxygen atoms, respectively) toward the univalent sodium cation, yielding the trinuclear (bpm)2Fe(II)-bpm-Na(I)-ox-Fe(III)(ox)2 complex. Two cis-coordinated water molecules complete the distorted octahedral surrounding of the sodium atom. The ranges of the Fe(II)-N(bpm) and Fe(III)-O(ox) bond distances [1.968(6)-1.993(5) and 1.992(6)-2.024(6) A, respectively] compare well with those observed in 1. The Na-N(bpm) bond lengths (2.548(7) and 2.677(7) A) are longer than those of Na-O(ox) (2.514(7) and 2.380(7) A) and Na-O(water) (2.334(15) and 2.356(12) A). The intramolecular Fe(II)...Fe(III) separation is 6.763(2) A, whereas the shortest intermolecular Fe(II)...Fe(II) and Fe(III)...Fe(III) distances are 8.152(2) and 8.992(2) A, respectively. Magnetic susceptibility measurements in the temperature range 2.0-290 K for 1 reveal that the high-spin iron(III) ions are antiferromagnetically coupled (J = -6.6 cm-1, the Hamiltonian being defined as H = -JS1.S2). The magnitude of the antiferromagnetic coupling through the bridging oxalato in the magneto-structurally characterized family of formula [M2(ox)5](2m-10)+ (M = Fe(III) (1), Cr(III), and Ni(II)) is analyzed and discussed by means of a simple orbital model.     

Model Investigations for Vanadium-Protein Interactions. Synthetic, Structural, and Physical Studies of Vanadium(III) and Oxovanadium(IV/V) Complexes with Amidate Ligands

Reaction of the amide ligand N-[2-((2-pyridylmethylene)amino)phenyl]pyridine-2-carboxamide (Hcapca) with VCl(3) affords the compound trans-[VCl(2)(capca)] (1), the first example of a vanadium(III) complex containing a vanadium-deprotonated amide nitrogen bond, while reaction of bis(pentane-2,4-dionato)oxovanadium(IV) with the related ligands N-[2-((2-phenolylmethylene)amino)phenyl]pyridine-2-carboxamide (H(2)phepca), 1-(2-hydroxybenzamido)-2-(2-pyridinecarboxamido)benzene (H(3)hypyb), and 1,2-bis(2-hydroxybenzamido)benzene (H(4)hybeb) yields the complexes [VO(phepca)] (2), Na[VO(hypyb)].2CH(3)OH (4.2CH(3)OH), and Na(2)[VO(hybeb)].3CH(3)OH (5.3CH(3)OH) respectively. The preparation of the complex {N-[2-((2-thiophenoylmethylene)amino)phenyl]pyridine-2-carboxamido}oxovanadium(IV) (3) has been achieved by reaction of N-(2-aminophenyl)pyridine-2-carboxamide and 2-mercaptobenzaldehyde with [VO(CH(3)COO)(2)](x)(). Oxidation of complex 5.3CH(3)OH with silver nitrate gives its vanadium(V) analogue (8.CH(3)OH), which is readily converted to its corresponding tetraethylammonium salt (10.CH(2)Cl(2)) by a reaction with Et(4)NCl. The crystal structures of the octahedral 1.CH(3)CN, and the square-pyramidal complexes 3, 4.CH(3)CN, 5.2CH(3)OH, and 10 were demonstrated by X-ray diffraction analysis. Crystal data are as follows: 1.CH(3)CN, C(18)H(13)Cl(2)N(4)OV.CH(3)CN M(r) = 464.23, monoclinic, P2(1)/n, a = 10.5991(7) ?, b = 13.9981(7) ?, c = 14.4021(7) ?, beta = 98.649(2)(o), V = 2112.5(3) A(3), Z = 4, R = 0.0323, and R(w) 0.0335; 3, C(19)H(13)N(3)O(2)SV, M(r) = 398.34, monoclinic, P2(1)/n, a = 12.1108(10) ?, b = 19.4439(18) ?, c = 7.2351(7) ?, beta = 103.012(3) degrees, V = 1660.0(4) ?(3), Z = 4, R = 0.0355, and R(w) = 0.0376; 4.CH(3)CN, C(19)H(12)N(3)O(4)VNa.CH(3)CN, M(r) = 461.31, monoclinic, P2(1)/c, a = 11.528(1) ?, b = 11.209(1) ?, c = 16.512(2) ?, beta = 103.928(4)(o), V = 2071.0(5) ?(3), Z = 4, R = 0.0649, and R(w) = 0.0806; 5.2CH(3)OH, C(20)H(10)N(2)O(5)VNa(2).2CH(3)OH, M(r) = 519.31, triclinic, P1, a = 12.839(1) ?, b = 8.334(1) ?, c = 12.201(1) ?, alpha = 106.492(2) degrees, beta = 105.408(2) degrees, gamma = 73.465(2) degrees, V = 1175.6(3) ?(3), Z = 2, R = 0.0894, and R(w) = 0.1043; 10, C(28)H(32)N(3)O(5)V M(r) = 541.52, monoclinic, P2(1)/c, a = 11.711(3) ?, b = 18.554(5) ?, c = 12.335(3) ?, beta = 95.947(9) degrees, V = 2666(2) ?(3), Z = 4, R = 0.0904, and R(w) = 0.0879. In addition to the synthesis and crystallographic studies, we report the optical, infrared, magnetic, and electrochemical properties of these complexes. Electron paramagnetic resonance [of oxovanadium(IV) species] and (1)H, (13)C{(1)H}, and (51)V nuclear magnetic resonance [of oxovanadium(V) complex] properties are reported as well. This study represents the first systematic study of vanadium(III), V(IV)O(2+), and V(V)O(3+) species containing a vanadium-deprotonated amide nitrogen bond.     

Syntheses and structural characterizations of endo-eta(1)-, exo-eta(1)-, eta(4)-, eta(5)-, and eta(6)-metallaphosphamonocarbaborane complexes derived from a versatile new polyborane ligand: exo-6-R-arachno-6,7-PCB(8)H(12)

Deprotonation of the phosphamonocarbaborane, exo-6-R-arachno-6,7-PCB(8)H(12) (R = Ph 1a or Me 1b), yields exo-6-R-arachno-6,7-PCB(8)H(11)(-), which when reacted with appropriate transition-metal reagents affords new metallaphosphamonocarbaborane complexes in which the metals adopt endo-eta(1), exo-eta(1), eta(4), eta(5), or eta(6) coordination geometries bonded to the formal R-arachno-PCB(8)H(11)(-), R-arachno-PCB(8)H(10)(2-), R-arachno-PCB(8)H(9)(3-), or R-nido-PCB(8)H(9)(-) ligands. The reaction of exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11)(-) (1a-) with Mn(CO)(5)Br generated the eta(1)-sigma product exo-6-[Mn(CO)(5)]-endo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11) (2) having the [Mn(CO)(5)] fragment in the thermodynamically favored exo position at the P6 cage atom. On the other hand, reaction of 1a- with (eta(5)-C(5)H(5))Fe(CO)(2)I resulted in the formation of two products, an eta(1)-sigma complex endo-6-[(eta(5)-C(5)H(5))Fe(CO)(2)]-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11) (3) having the (eta(5)-C(5)H(5))Fe(CO)(2) fragment attached at the endo-P6 position and an eta(6)-closo complex, 1-(eta(5)-C(5)H(5))-2-(C(6)H(5))-closo-1,2,3-FePCB(8)H(9) (4a). Rearrangement of the endo-compound 3 to its exo-isomer 5 was observed upon photolysis of 3. Synthesis of the methyl analogue of 4a, 1-(eta(5)-C(5)H(5))-2-CH(3)-closo-1,2,3-FePCB(8)H(9) (4b), along with a double-insertion product, 1-CH(3)-2,3-(eta(5)-C(5)H(5))(2)-2,3,1,7-Fe(2)PCB(8)H(9) (6), containing two iron atoms eta(5)-coordinated to a formal R-arachno-PCB(8)H(9)(3-), was achieved by reaction of exo-6-CH(3)-arachno-6,7-PCB(8)H(11)(-) (1b-) with FeCl(2) and Na(+)C(5)H(5)(-). Complexes 4a and 4b can be considered ferrocene analogues, in which an Fe(II) is sandwiched between C(5)H(5)(-) and 6-R-nido-6,9-PCB(8)H(9)(-) anions. Reaction of exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11)(-) (1a-) with cis-dichlorobis(triphenylphosphine)platinum (II) afforded two compounds, an eta(1)-sigma complex with the metal fragment again in the endo-P6 position, endo-6-[cis-(Ph(3)P)(2)PtCl]-exo-6-(C(6)H(5))-arachno-6,7-PCB(8)H(11) (7) and an eta(4)-complex, 7-(C(6)H(5))-11-(Ph(3)P)(2)-nido-11,7,8-PtPCB(8)H(10) (8) containing the formal R-arachno-PCB(8)H(10)(2)(-) anion. The structures of compounds 2, 3, 4a, 4b, 6, 7, and 8 were crystallographically confirmed.