Synthesis and characterization of half-sandwich N-heterocyclic carbene complexes of cobalt and rhodium

A series of novel half-sandwich M(I) and M(III) complexes (M = Co, Rh) bearing the N-heterocyclic carbene ligand 1,3-dimesitylimidazol-2-ylidene (IMes) have been prepared and characterized. Thus, (eta5-C(5)R(5))M(IMes)(C(2)H(4))(M = Co, Rh; R = H, Me) were obtained from the corresponding bis(ethene) complexes (eta5-C(5)R(5))M(C(2)H(4))(2), except for CpRh(IMes)(C(2)H(4)) which was prepared via the novel 16-electron Rh(I) compound Rh(IMes)(C(2)H(4))(2)Cl. The carbonyl compounds (eta5-C(5)R(5))Co(IMes)(CO)(R = H, Me) were synthesized by thermal CO substitution of (eta5-C(5)R(5))Co(CO)(2). A diamagnetic, apparently 16-electron Co(III) compound [CpCo(IMes)I](+)[I(3)(-)] was obtained from CpCo(IMes)(CO) and I(2). Finally, Co(III) and Rh(III) complexes CpCo(IMes)Me(2) and Cp*Rh(IMes)Me(2) were prepared by methylation of [CpCo(IMes)I](+)[I(3)(-)], and ligand exchange at Cp*Rh(Me(2)SO)Me(2), respectively. The molecular structures of CpCo(IMes)(CO), CpRh(IMes)(C(2)H(4)), Cp*Rh(IMes)(C(2)H(4)), and Cp*Rh(IMes)Me(2) were determined by single crystal X-ray diffraction. Steric and electronic factors imposed by the strongly donating and sterically demanding IMes ligand are discussed on the basis of X-ray crystallographic, NMR, and IR spectroscopic analyses. Very poor correlations are found between values for (1)J(Rh-C(carbene)) and dRh-C(carbene) data for Rh(i) N,N-heterocyclic carbene complexes including literature data and this work.     

Palladium complexes of a phosphorus ylide with two stabilizing groups: synthesis, structure, and DFT study of the bonding modes

The phosphorus ylide ligand [Ph3P=C(CO2Me)C(=NPh)CO2Me] (L1) has been prepared and fully characterized by spectroscopic, crystallographic, and density functional theory (DFT) methods (B3LYP level). The reactivity of L1 toward several cationic Pd(II) and Pt(II) precursors, with two vacant coordination sites, has been studied. The reaction of [M(C/\X)(THF)2]ClO4 with L1 (1:1 molar ratio) gives [M(C/\X)(L1)]ClO4 [M = Pd, C/\X = C6H4CH2NMe2 (1), S-C6H4C(H)MeNMe2 (2), CH2-8-C9H6N (3), C6H4-2-NC5H4 (4), o-CH2C6H4P(o-tol)2 (6), eta3-C3H5 (7); M = Pt, C/\X = o-CH2C6H4P(o-tol)2 (5); M(C/\X) = Pd(C6F5)(SC4H8) (8), PdCl2 (9)]. In complexes 1-9, the ligand L1 bonds systematically to the metal center through the iminic N and the carbonyl O of the stabilizing CO2Me group, as is evident from the NMR data and from the X-ray structure of 3. Ligand L1 can also be orthopalladated by reaction with Pd(OAc)2 and LiCl, giving the dinuclear derivative [Pd(mu-Cl)(C6H4-2-PPh2=C(CO2Me)C(CO2Me)=NPh)]2 (10). The X-ray crystal structure of 10 is also reported. In none of the prepared complexes 1-10 was the C(alpha) atom found to be bonded to the metal center. DFT calculations and Bader analysis were performed on ylide L1 and complex 9 and its congeners in order to assess the preference of the six-membered N,O metallacycle over the four-membered C,N and five-membered C,O rings. The presence of two stabilizing groups at the ylidic C causes a reduction of its bonding capabilities. The increasing strength of the Pd-C, Pd-O, and Pd-N bonds along with other subtle effects are responsible for the relative stabilities of the different bonding modes.     

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).     

过渡金属氢化物和聚集双键化合物反应的研究——Ⅴ.Cp_2MH_2(M=Zr,Hf)与RNCS(R=n-Bu,c-C_6H_(11),C_6H_5,2-C_(10)H_7)、CS_2的反应

本文研究了Cp_2ZrH_2与CS_2、RNCS(R=n-Bu,c-C_6H_11,C_6H_5,2-C_(10)H_7)和Cp_2HfH_2与c-C_6H_(11)NCS的反应,探讨了在这类新型脱硫反应中锆氢与铪氢配合物化学反应性能上的差异.从以上反应中分别得到两个硫桥同核双金属配合物(Cp_2MS)_2(1,M=Zr;2,M=Hf)和有机铪配合物Cp_2Hf[SC(H)NR]_2(3,R=c-C_6H_(11)).产物结构由元素分析、IR、~1H和~(13)C NMR及MS谱分析鉴定,产物1的晶体结构由X光四圆衍射方法测定,有机产物X=CH_2和CH_3X(H)(X=S,NR)由GC-MS谱分析测定.     

Preparation of highly fluorinated cyclopropanes and ring-opening reactions with halogens

Various highly fluorinated cyclopropanes 1 were prepared by reaction of the appropriate fluorinated olefins with hexafluoropropylene oxide (HFPO) at 180 degrees C. The fluorinated nitrile 1e was converted to the triazine derivatives 2a and 2b by catalysis with Ag(2)O and NH(3)/(CF(3)CO)(2)O, respectively. The fluorinated cyclopropanes reacted with halogens at elevated temperatures to provide the first useful, general synthesis of 1,3-dihalopolyfluoropropanes. At 150-240 degrees C, hexafluorocyclopropane and halogens X(2) produce XCF(2)CF(2)CF(2)X (X = Cl, Br, I) in 50-80% isolated yields. Pentafluorocyclopropanes c-C(3)F(5)Y [Y = Cl, OCF(3), OC(3)F(7) and OCF(2)CF(CF(3))OCF(2)CF(2)Z; Z = SO(2)F, CN, CO(2)Me] react regiospecifically at 150 degrees C to give XCF(2)CF(2)CFXY, c-C(3)F(5)Br reacts regioselectively with Br(2) to give a 16.7:1 mixture of BrCF(2)CF(2)CFBr(2):BrCF(2)CFBrCF(2)Br, whereas c-C(3)F(5)H reacts unselectively with I(2) to produce a statistical 2:1 mixture of ICF(2)CF(2)CFHI:ICF(2)CFHCF(2)I. Tri- and di(pentafluorocyclopropyl) derivatives 2 also undergo ring-opening reaction with halogens to give 16 and 17. Upon treatment of tetrafluorocyclopropanes 1j, 1k, and 1l with Br(2) or I(2), ring opening occurred exclusively at substituted carbons to give XCF(2)CF(2)CXY(2). Thermolysis of the ring-opened product ICF(2)CF(2)CFIOR(F) at 240 degrees C gave R(F)I and ICF(2)CF(2)COF in high yields.     

Syntheses of 1-alkyl-1,2,4-triazoles and the formation of quaternary 1-alkyl-4-polyfluoroalkyl-1,2,4-triazolium salts leading to ionic liquids

1,2,4-triazole was alkylated (alkyl = methyl, butyl, heptyl, decyl) at N-1 in >90% isolated yields. The resulting 1-alkyl triazoles were quaternized at N-4 in >98% isolated yields using fluorinated alkyl halides with >98% isolated yields, under neat reaction conditions at 100-120 degrees C to form N1-CH(3)-N4-(CH(2))(2)C(m)F(2)(m)(+ 1)-triazolium (Taz) iodide (m = 1, 6), N1-C(4)H(9)-N4-(CH(2))(2)C(m)F(2)(m)(+ 1)-Taz iodide (m = 1, 4, 6), N1-C(7)H(15)-N4-(CH(2))(2)C(m)F(2)(m)(+ 1)-Taz iodide (m = 1, 4, 6), N1-C(10)H(21)-N4-(CH(2))(2)C(m)F(2)(m)(+1)-Taz iodide (m = 1, 4), and N1-C(n)H(2)(n )(+ 1)-N4-(CH(2))(2)F-Taz bromide (n = 4, 7, 10). Single-crystal X-ray analyses confirmed the structure of [1-CH(3)-4-CH(2)CH(2)CF(3)-Taz](+)I(-). It crystallized in the orthorhombic space group Pccn, and the unit cell dimensions were a = 13.8289(9) A, b = 17.3603(11) A, c = 9.0587(6) A (alpha = beta = gamma = 90 degrees ). Metathesis of these polyfluoroalkyl-substituted triazolium halides with other salts led to the formation of quaternary compounds, some of which comprise ionic liquids, namely, [R(R(f))-Taz](+)Y(-) (Y = NTf(2), BF(4), PF(6), and OTf), in good isolated yields without the need for further purification: N1-CH(3)-N4-(CH(2))(2)C(m)F(2)(m)( +) (1)-Taz Y (m = 1, 6; Y = NTf(2)), N1-C(4)H(9)-N4-(CH(2))(2)C(m)F(2)(m)(+ 1)-Taz Y (m = 1, 4, 6; Y = NTf(2)), N1- C(7)H(15)-N4-(CH(2))(2)C(m)F(2)(m)(+ 1)-Taz Y (m = 1, 4, 6; Y = NTf(2)), N1-C(10)H(21)-N4-(CH(2))(2)C(m)F(2)(m)(+1)-Taz Y (n = 1, 4; Y = NTf(2)), N1-C(n)H(2)(n )(+ 1)-N4-(CH(2))(2)F-Taz Y (n = 7, 10; Y = NTf(2)), N1-C(10)H(21)-N4-(CH(2))(2)F-TazY (Y = OTf), N1-C(7)H(15)-N4-(CH(2))(2)F-TazY (Y = BF(4)), N1-C(4)H(9)-N4-(CH(2))(2)C(m)F(2)(m) (+ 1)-Taz Y (m = 4, 6; Y = PF(6)), N1-C(7)H(15)-N4-(CH(2))(2)C(4)F(9)-Taz Y (Y = PF(6)), N1-C(4)H(9)-N4-(CH(2))(2)C(m)F(2)(m)(+ 1)-Taz Y (m = 4, 6; Y = OTf). All new compounds were characterized by (1)H, (19)F, and (13)C NMR and MS spectra and elemental analyses. T(g)s and T(m)s of ionic liquids were determined by DSC.     

M...HNR interactions in imino-bound diaryltriazene complexes: structure and fluxionality

The nominally square-planar coordination of the d(8) complexes [MClL(1)L(2)(p-XC(6)H(4)NNNHC(6)H(4)X-p)](M = Rh, L(1)= L(2)= CO, X = H, Me, Et or F; M = Ir, L(1)= L(2)= CO, X = Me; M = Pd or Pt, L(1)= Cl, L(2)= PPh(3), X = Me; M = Pd, L(1)L(2)=eta(3)-C(3)H(5), X = Me), with the triazene N-bonded via the imine group, is supplemented by an axial M...H-N interaction involving the terminal amino group.     

Cyclodiphosphazanes with hemilabile ponytails: synthesis, transition metal chemistry (Ru(II), Rh(I), Pd(II), Pt(II)), and crystal and molecular structures of mononuclear (Pd(II), Rh(I)) and bi- and tetranuclear rhodium(I) complexes

Cyclodiphosphazanes having hemilabile ponytails such as cis-[(t)()BuNP(OC(6)H(4)OMe-o)](2) (2), cis-[(t)()BuNP(OCH(2)CH(2)OMe)](2) (3), cis-[(t)BuNP(OCH(2)CH(2)SMe)](2) (4), and cis-[(t)BuNP(OCH(2)CH(2)NMe(2))](2) (5) were synthesized by reacting cis-[(t)()BuNPCl](2) (1) with corresponding nucleophiles. The reaction of 2 with [M(COD)Cl(2)] afforded cis-[MCl(2)(2)(2)] derivatives (M = Pd (6), Pt (7)), whereas, with [Pd(NCPh)(2)Cl(2)], trans-[MCl(2)(2)(2)] (8) was obtained. The reaction of 2 with [Pd(PEt(3))Cl(2)](2), [{Ru(eta(6)-p-cymene)Cl(2)](2), and [M(COD)Cl](2) (M = Rh, Ir) afforded mononuclear complexes of Pd(II) (9), Ru(II) (11), Rh(I) (12), and Ir(I) (13) irrespective of the stoichiometry of the reactants and the reaction condition. In the above complexes the cyclodiphosphazane acts as a monodentate ligand. The reaction of 2 with [PdCl(eta(3)-C(3)H(5))](2) afforded binuclear complex [(PdCl(eta(3)-C(3)H(5)))(2){((t)BuNP(OC(6)H(4)OMe-o))(2)-kappaP}] (10). The reaction of ligand 3 with [Rh(CO)(2)Cl](2) in 1:1 ratio in CH(3)CN under reflux condition afforded tetranuclear rhodium(I) metallamacrocycle (14), whereas the ligands 4 and 5 afforded bischelated binuclear complexes 15 and 16, respectively. The crystal structures of 8, 9, 12, 14, and 16 are reported.     

Rhodium/iridium-titanium azaheterometallocubanes

Treatment of [[Ti(eta5-C5Me5)(mu-NH)]3(mu3-N)] (1) with the diolefin complexes [[MCl(cod)]2] (M = Rh, Ir; cod = 1,5-cyclooctadiene) in toluene afforded the ionic complexes [M-(cod)(mu3-NH)3Ti3(eta5-C5Me5)3(mu3-N)]Cl [M = Rh (2), Ir (3)]. Reaction of complexes 2 and 3 with [Ag(BPh4)] in dichloromethane leads to anion metathesis and formation of the analogous ionic derivatives [M(cod)(mu3-NH)3Ti3-(eta5-C5Me5)3(mu3-N)][BPh4] [M = Rh (4), Ir (5)]. An X-ray crystal structure determination for 5 reveals a cube-type core [IrTi3N4] for the cationic fragment, in which 1 coordinates in a tripodal fashion to the iridium atom. Reaction of the diolefin complexes [[MCl(cod))2] (M = Rh, Ir) and [[RhCl(C2H4)2]2] with the lithium derivative [[Li(mu3-NH)2(mu3-N)-Ti3(eta5-C5Me5)3(mu3-N)]2] x C7H8 (6 C7H8) in toluene gave the neutral cube-type complexes [M(cod)(mu-NH)2(mu3-N)Ti3-(eta5-C5Me5)3(mu3-N)] [M = Rh (7), Ir (8)] and [Rh(C2H4)2(mu3-NH)2(mu3-N)Ti3(eta5-C5Me5)3(mu3-N)] (9), respectively. Density functional theory calculations have been carried out on the ionic and neutral azaheterometallocubane complexes to understand their electronic structures.     

Intramolecular alkyl phosphine dehydrogenation in cationic rhodium complexes of tris(cyclopentylphosphine)

[Rh(nbd)(PCyp(3))(2)][BAr(F) (4)] (1) [nbd = norbornadiene, Ar(F) = C(6)H(3)(CF(3))(2), PCyp(3) = tris(cyclopentylphosphine)] spontaneously undergoes dehydrogenation of each PCyp(3) ligand in CH(2)Cl(2) solution to form an equilibrium mixture of cis-[Rh{PCyp(2)(eta(2)-C(5)H(7))}(2)][BAr(F) (4)] (2 a) and trans-[Rh{PCyp(2)(eta(2)-C(5)H(7))}(2)][BAr(F) (4)] (2 b), which have hybrid phosphine-alkene ligands. In this reaction nbd acts as a sequential acceptor of hydrogen to eventually give norbornane. Complex 2 b is distorted in the solid-state away from square planar. DFT calculations have been used to rationalise this distortion. Addition of H(2) to 2 a/b hydrogenates the phosphine-alkene ligand and forms the bisdihydrogen/dihydride complex [Rh(PCyp(3))(2)(H)(2)(eta(2)-H(2))(2)][BAr(F) (4)] (5) which has been identified spectroscopically. Addition of the hydrogen acceptor tert-butylethene (tbe) to 5 eventually regenerates 2 a/b, passing through an intermediate which has undergone dehydrogenation of only one PCyp(3) ligand, which can be trapped by addition of MeCN to form trans-[Rh{PCyp(2)(eta(2)-C(5)H(7))}(PCyp(3))(NCMe)][BAr(F) (4)] (6). Dehydrogenation of a PCyp(3) ligand also occurs on addition of Na[BAr(F) (4)] to [RhCl(nbd)(PCyp(3))] in presence of arene (benzene, fluorobenzene) to give [Rh(eta(6)-C(6)H(5)X){PCyp(2)(eta(2)-C(5)H(7))}][BAr(F) (4)] (7: X = F, 8: X = H). The related complex [Rh(nbd){PCyp(2)(eta(2)-C(5)H(7))}][BAr(F) (4)] 9 is also reported. Rapid ( approximately 5 minutes) acceptorless dehydrogenation occurs on treatment of [RhCl(dppe)(PCyp(3))] with Na[BAr(F) (4)] to give [Rh(dppe){PCyp(2)(eta(2)-C(5)H(7))}][BAr(F) (4)] (10), which reacts with H(2) to afford the dihydride/dihydrogen complex [Rh(dppe)(PCyp(3))(H)(2)(eta(2)-H(2))][BAr(F) (4)] (11). Competition experiments using the new mixed alkyl phosphine ligand PCy(2)(Cyp) show that [RhCl(nbd){PCy(2)(Cyp)}] undergoes dehydrogenation exclusively at the cyclopentyl group to give [Rh(eta(6)-C(6)H(5)X){PCy(2)(eta(2)-C(5)H(7))}][BAr(F) (4)] (17: X = F, 18: X = H). The underlying reasons behind this preference have been probed using DFT calculations. All the complexes have been characterised by multinuclear NMR spectroscopy, and for 2 a/b, 4, 6, 7, 8, 9 and 17 also by single crystal X-ray diffraction.     

Structures of tetrafluorocyclopropene, hexafluorocyclobutene, octafluorocyclopentene and related perfluoroalkene radical anions revealed by electron spin resonance spectroscopic and computational studies

Isotropic and anisotropic ESR spectra were observed for the radical anions of hexafluorocyclobutene (c-C(4)F(6)(-)), octafluorocyclopentene (c-C(5)F(8)(-)) and perfluoro-2-butene (CF(3)CF=CFCF(3)(-)) in gamma-irradiated plastically crystalline neopentane, tetramethylsilane (TMS) and TMS-d(12) matrices, or the rigid 2-methyltetrahydrofuran (MTHF) matrix. The isotropic spectra of c-C(4)F(6)(-) and c-C(5)F(8)(-) are characterized by three different sets of pairs of (19)F nuclei with the isotropic hyperfine (hf) splittings of 15.2 (2F), 6.5 (2F), 1.1 (2F) mT for c-C(4)F(6)(-) and 14.7 (2F), 7.4 (2F), 1.0 (2F) mT for c-C(5)F(8)(-). By comparison with the results of ab initio quantum chemical computations, the large triplet (19)F hf splittings of ca. 15 mT are assigned to the two fluorines attached to the C=C bond. The UHF, B3LYP and MP2 computations predict that the geometrical structures of the perfluoroalkenes are strongly distorted by one-electron reduction to form their radical anions; c-C(3)F(4)(-): C(2) symmetry ((2)A state) <-- C(2)(v) ((1)A(1)), c-C(4)F(6)(-): C(1) ((2)A) <-- C(2)(v) ((1)A(1)) and c-C(5)F(8)(-): C(1) ((2)A) <-- C(s) ((1)A'). The structural distortion arises from a mixing of the pi* and higher-lying sigma* orbitals at the C=C carbons similar to that previously found for CF(2)=CF(2)(-) with a C(2)(h) distortion. The isotropic (19)F hf splittings computed with the B3LYP method with 6-311+G(2df,p) basis set for the geometry optimized by the UHF and/or MP2 methods are within 6% error of the experimental values. The experimental anisotropic spectra of c-C(4)F(6)(-), c-C(5)F(8)(-) and CF(2)=CF(2)(-) were satisfactorily reproduced by the ESR spectral simulation method using the computed hf principal values and orientation of (19)F nuclei. In addition, the electronic excitation energies and oscillator strengths for the CF(2)=CF(2)(-), c-C(3)F(4)(-), c-C(4)F(6)(-) and c-C(5)F(8)(-) radical anions were computed for the first time by TD-DFT methods.     

Allylic C-H bond activation and functionalization mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) compounds

Allylic C-H bond oxidative addition reactions, mediated by tris(oxazolinyl)borato rhodium(I) and iridium(I) species, provide the first step in a hydrocarbon functionalization sequence. The bond activation products To(M)MH(η(3)-C(8)H(13)) (M = Rh (1), Ir (2)), To(M)MH(η(3)-C(3)H(5)) (M = Rh (3), Ir (4)), and To(M)RhH(η(3)-C(3)H(4)Ph) (5) (To(M) = tris(4,4-dimethyl-2-oxazolinyl)phenylborate) are synthesized by reaction of Tl[To(M)] and the corresponding metal olefin chloride dimers. Characterization of these group 9 allyl hydride complexes includes (1)H-(15)N heteronuclear correlation NMR experiments that reveal through-metal magnetization transfer between metal hydride and the trans-coordinated oxazoline nitrogen. Furthermore, the oxazoline (15)N NMR chemical shifts are affected by the trans ligand, with the resonances for the group trans to hydride typically downfield of those trans to η(3)-allyl and tosylamide. These group 9 oxazolinylborate compounds have been studied to develop approaches for allylic functionalization. However, this possibility is generally limited by the tendency of the allyl hydride compounds to undergo olefin reductive elimination. Reductive elimination products are formed upon addition of ligands such as CO and CN(t)Bu. Also, To(M)RhH(η(3)-C(8)H(13)) and acetic acid react to give To(M)RhH(κ(2)-O(2)CMe) (8) and cyclooctene. In contrast, treatment of To(M)RhH(η(3)-C(3)H(5)) with TsN(3) (Ts = SO(2)C(6)H(4)Me) gives the complex To(M)Rh(η(3)-C(3)H(5))NHTs (10). Interestingly, the reaction of To(M)RhH(η(3)-C(8)H(13)) and TsN(3) yields To(M)Rh(NHTs)(H)OH(2) (11) and 1,3-cyclooctadiene viaβ-hydride elimination and Rh-H bond amination. Ligand-induced reductive elimination of To(M)Rh(η(3)-C(3)H(5))NHTs provides HN(CH(2)CH=CH(2))Ts; these steps combine to give a propene C-H activation/functionalization sequence.     

Synthesis and characterisation of transition metal halide complexes of the xylyl-distibine, 1,2-bis(dimethylstibanylmethyl)benzene

Complexes of the title ligand with Cu(I), Ag(I), Au(I), Pd(II), Pt(II), Rh(III), and rare examples with Ni(II) and Co(III) have been prepared and characterised by analysis, IR, UV-vis, 1H, 63Cu and 59Co NMR spectroscopy and ES+ mass spectrometry as appropriate. The structures of [Cu[1,2-C6H4(CH2SbMe2)2]2]BF4, [PtCl2[1,2-C6H4(CH2SbMe2)2]], [M[1,2-C6H4(CH2SbMe2)2]2][PF6]2 (M = Pd or Pt), and [NiI[1,2-C6H4(CH2SbMe2)2]2]ClO4 have been determined, and the varying chelate bite and conformations of the xylyl backbone in these structures are discussed. Despite the unfavourable seven-membered chelate ring and the large soft antimony donors, 1,2-C6H4(CH2SbMe2)2 proves to be a surprisingly good ligand for late transition metals in medium oxidation states.     

Synthesis and Characterization of Linked Clusters Capped by Alkylidyne

1 INTRODUCTION Constructing higher nuclearity clusters with well-defined dimensions and structures provide a rather active field of chemistry with potential applications in areas including nanotechnology, molecular recognition and catalysis[1~4]. A continuing effort has been directed toward developing a better methodology for systematic synthesis of supracluster compounds through molecular design [5,6]. On the basis of extensive investigation on the metal exchange reaction in cluster com…     

Molecular nitrides containing group 4 and 5 metals: single and double azatitanocubanes

Treatment of [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) with the imido complexes [Ti(NAr)Cl(2)(py)(3)] (Ar=2,4,6-C(6)H(2)Me(3)) and [Ti(NtBu)Cl(2)(py)(3)] in toluene affords the single azatitanocubanes [[Cl(2)(ArN)Ti]( micro(3)-NH)(3)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (2.C(7)H(8)) and [[Cl(2)Ti](micro(3)-N)(2)(micro(3)-NH)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (3), respectively. Similar reactions of complex 1 with the niobium and tantalum imido derivatives [[M(NtBu)(NHtBu)Cl(2)(NH(2)tBu)](2)] (M=Nb, Ta) in toluene give the single azaheterometallocubanes [[Cl(2)(tBuN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]] (M=Nb (4), Ta (5)), both complexes react with 2,4,6-trimethylaniline to yield the analogous species [[Cl(2)(ArN)M](micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]].(C(7)H(8)) (Ar=2,4,6-C(6)H(2)Me(3), M=Nb (6.C(7)H(8)), Ta (7.C(7)H(8))). Also the azaheterodicubanes [M[micro(3)-N)(2)(micro(3)-NH)](2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2C(7)H(8) [M=Ti (8.2C(7)H(8)), Zr (9.2C(7)H(8))], and [M[(micro(3)-N)(5)(micro(3)-NH)][Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)](2)].2 C(7)H(8) (Nb (10.2C(7)H(8)), Ta (11.2C(7)H(8))) were prepared from 1 and the homoleptic dimethylamido complex [M(NMe(2))(x)] (x=4, M=Ti, Zr; x=5, M=Nb, Ta) in toluene at 150 degrees C. X-ray crystal structure determinations were performed for 6 and 10, which revealed a cube- and double-cube-type core, respectively. For complexes 2 and 4-7 we observed and studied by DNMR a rotation or trigonal-twist of the organometallic ligands [[Ti(eta(5)-C(5)Me(5))(micro-NH)](3)(micro(3)-N)] (1) and [(micro(3)-N)(micro(3)-NH)(2)[Ti(3)(eta(5)-C(5)Me(5))(3)(micro(3)-N)]](1-). Density functional theory calculations were carried out on model complexes of 2, 3, and 8 to establish and understand their structures.     

Preparation of benzyne complexes of group 10 metals by intramolecular suzuki coupling of ortho-metalated phenylboronic esters: molecular structure of the first benzyne-palladium(0) complex

A series of nickel(II) and palladium(II) aryl complexes substituted in the ortho position of the aromatic ring by a (pinacolato)boronic ester group, [MBr[o-C(6)H(4)B(pin)]L(2)] (M = Ni, L(2) = 2PPh(3) (2a), 2PCy(3) (2b), 2PEt(3) (2c), dcpe (2d), dppe (2e), and dppb (2f); M = Pd, L(2) = 2PPh(3) (3a), 2PCy(3) (3b), and dcpe (3d)), has been prepared. Many of these complexes react readily with KO(t)Bu to form the corresponding benzyne complexes [M(eta(2)-C(6)H(4))L(2)] (M = Ni, L(2) = 2PPh(3) (4a), 2PCy(3) (4b), 2PEt(3) (4c), dcpe (4d); M = Pd, L(2) = 2PCy(3) (5b)). This reaction can be regarded as an intramolecular version of a Suzuki cross-coupling reaction, the driving force for which may be the steric interaction between the boronic ester group and the phosphine ligands present in the precursors 2 and 3. Complex 3d also reacts with KO(t)Bu, but in this case disproportionation of the initially formed eta(2)-C(6)H(4) complex (5d) leads to a 1:1 mixture of a novel dinuclear palladium(I) complex, [(dcpe)Pd(mu(2)-C(6)H(4))Pd(dcpe)] (6), and a 2,2'-biphenyldiyl complex, [Pd(2,2'-C(6)H(4)C(6)H(4))(dcpe)] (7d). Complexes 2a, 3b, 3d, 4b, 5b, 6, and 7d have been structurally characterized by X-ray diffraction; complex 5b is the first example of an isolated benzyne-palladium(0) species.     

New palladium-catalyzed cross-coupling routes to carbon functionalized metallatricarbadecaboranes

A general method for the synthesis of cage-carbon-functionalized cyclopentadienyl iron and cyclopentadienyl ruthenium tricarbadecaboranyl complexes has been developed that employs palladium-catalyzed Sonogashira, Heck, and Stille cross-coupling reactions directed at a cage-carbon haloaryl substituent. The key Li(+)[6-(p-XC(6)H(4))-nido-5,6,9-C(3)B(7)H(9)(-)] (X = I (1), Br (2), Cl (3)) haloaryl-tricarbadecaboranyl anionic ligands were synthesized in high yields via the reaction of the arachno-4,6-C(2)B(7)H(12)(-) anion with the corresponding p-halobenzonitriles (p-XC(6)H(4)-CN). The reactions of the salts 1-3 with (η(5)-C(5)H(5))Fe(CO)(2)I and (η(5)-C(5)H(5))Ru(CH(3)CN)(3)PF(6) were then used to produce the haloaryl complexes 1-(η(5)-C(5)H(5))-2-(p-XC(6)H(4))-closo-1,2,3,4-MC(3)B(7)H(9) (M = Fe, X = I (4), Br (5), Cl (6) and M = Ru, X = I (7), Br (8), Cl (9)). The sonication-promoted Sonogashira coupling reactions of 4 with terminal alkynes catalyzed by Pd(dppf)(2)Cl(2)/CuI yielded the alkynyl-linked derivatives 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = (PhC≡C)- (10), (CH(3)CH(2)C(O)OCH(2)C≡C)- (11), ((η(5)-C(5)H(5))Fe(η(5)-C(5)H(4)C≡C))- (12)). Heck reactions of 4 with terminal alkenes catalyzed by Pd(OAc)(2) yielded the alkene-functionalized products 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = (PhCH(2)CH═CH)- (13), (CH(3)(CH(2))(2)CH═CH)- (14)), while the Stille cross-coupling reactions of 4 with organotin compounds catalyzed by Pd(PPh(3))(2)Cl(2) afforded the complexes 1-(η(5)-C(5)H(5))-2-p-RC(6)H(4)-closo-1,2,3,4-FeC(3)B(7)H(9) (R = Ph- (15), (CH(2)═CH)- (16), (CH(2)═CHCH(2))- (17)). These reactions thus provide facile and systematic access to a wide variety of new types of functionalized metallatricarbadecaboranyl complexes with substituents needed for potential metallocene-like biomedical and/or optoelectronic applications.     

On the prospects of polynuclear complexes with acetylenedithiolate bridging units

The generation of polynuclear complexes with one, two, or four acetylenedithiolate bridging units via the isolation of eta2-alkyne complexes of acetylenedithiolate K[Tp'M(CO)(L)(C2S2)] (Tp'=hydrotris(3,5-dimethylpyrazolyl)borate, M=W, L=CO (K-3a), M=Mo, L=CNC6H3Me2 (K-3b)) is reported. The strong electronic cooperation of Ru and W in the heterobimetallic complexes [(eta5-C5H5)(PPh3)Ru(3a)] (4a) and [(eta5-C5H5)(Me2C6H3NC)Ru(3a)] (4b) has been elucidated by correlation of the NMR, IR, UV-vis, and EPR-spectroscopic properties of the redox couples 4a/4a+ and 4b/4b+ with results from density functional calculations. Treatment of M(II) (M=Ni, Pd, Pt) with K-3a and K-3b afforded the homoleptic bis complexes [M(3a)2] (M=Ni (5a), Pd (5b), Pt (5c)), and [M(3b)2] (M=Pd (6a) and Pt (6b)), in which the metalla-acetylendithiolates exclusively serve as S,S'-chelate ligands. The vibrational and electronic spectra as well as the cyclic voltammetry behavior of all the complexes are compared. The structural analogy of 5a/5b/5c and 6a/6b with dithiolene complexes is only partly reflected in the electronic structures. The very intense visible absorptions involve essential d orbital contributions of the central metal, while the redox activity is primarily attributed to the alkyne complex moiety. Accordingly, stoichiometric reduction of 5a/5b/5c yields paramagnetic complex anions with electron-rich alkyne complex moieties being indistinguishable in the IR time scale. K-3a forms with Cu(I) the octanuclear cluster [Cu(3a)]4 (7) exhibiting a Cu4(S2C2)4W4 core. The nonchelating bridging mode of the metalla-acetylenedithiolate 3a- in 7 is recognized by a high-field shift of the alkyne carbon atoms in the 13C NMR spectrum. X-ray diffraction studies of K[Tp'(CO)(Me3CNC)Mo(eta2-C2S2)] (K-3c), 4b, 6a, 6b, and 7 are included. Comparison of the molecular structures of K-3c and 7 on the one hand with 4b and 6a/6b on the other reveals that the small bend-back angles in the latter are a direct consequence of the chelate ring formation.     

Palladacyclic complexes bearing CNN-type ligands as catalysts in the Heck reaction

Preparations of novel unsymmetrical, tridentate nitrogen ligand precursors, PhN=C(CMe2)(NPh)C=N(CH2)2NMe2(1) and PhN=C(CMe2)(NPh)C=N(CH2)Py (2), are described. Treatment of 1 with 1 molar equiv. (COD)PdCl2 in the presence of NEt3 or with 1 molar equiv. Pd(OAc)2 affords orthometallated palladium(II) complexes, [PhN=C(CMe2)(N-eta1-Ph)C=N(CH2)2NMe2]PdX (X=Cl (3); X=OAc (4)), respectively. Compound can be yielded via the reaction of with an excess of LiCl in methanol. Treatment of with 1 molar equiv. of (COD)PdCl2, Pd(OAc)2 or Pd(TFA)2 affords orthometallated palladium(II) complexes, [PhN=C(CMe2)(N-eta1-Ph)C=NCH2Py]PdX (X=Cl (5); X=OAc (6); X=TFA (7)), respectively. The crystal and molecular structures are reported for compounds 2, 3, 5 and 6. The application of these novel palladacyclic complexes to the Heck reaction with aryl halide substrates was examined.     

Syntheses and structures of heterometallic clusters by the reaction of o-carboranyl cobaltadichalcogenolato complexes

Metalladichalcogenolate cluster complexes [Cp'Co{E(2)C(2)(B(10)H(10))}]{Co2(CO)5} [Cp' = eta5-C5H5, E = S(3a), E = Se(3b); Cp' = eta5-C5(CH3)5, E = S(4a), E = Se(4b)], {CpCo[E(2)C(2)(B(10)H(10))]}(2)Mo(CO)2] [E = S(5a), Se(5b)], Cp*Co(micro2-CO)Mo(CO)(py)2[E(2)C(2)(B(10)H(10))] [E = S(6a), Se(6b)], Cp*Co[E(2)C(2)(B(10)H(10))]Mo(CO)2[E(2)C(2)(B(10)H(10))] [E = S(7a), Se(7b)], (Cp'Co[E(2)C(2)(B(10)H(10))]W(CO)2 [E(2)C(2)(B(10)H(10))] [Cp' = eta5-C5H5, E = S(8a), E = Se(8b); Cp' = eta5-C5(CH3)5, E = S(9a), E = Se(9b)], {CpCo[E(2)C(2)(B(10)H(10))]}(2)Ni [E = S(10a), Se(10b)] and 3,4-(PhCN(4)S)-3,1,2-[PhCN(4)SCo(Cp)S(2)]-3,1,2-CoC(2)B(9)H(8) 12 were synthesized by the reaction of [Cp'CoE(2)C(2)(B(10)H(10))] [Cp' = eta5-C5H5, E = S(1a), E = Se(1b); Cp' = eta5-C5(CH3)5, E = S(2a), E = Se(2b)] with Co2(CO)8, M(CO)3(py)3 (M = Mo, W), Ni(COD)2, [Rh(COD)Cl]2, and LiSCN4Ph respectively. Their spectrum analyses and crystal structures were investigated. In this series of multinuclear complexes, 3a,b and 4a,b contain a closed Co3 triangular geometry, while in complexes 5a-7b three different structures were obtained, the tungsten-cobalt mixed-metal complexes have only the binuclear structure, and the nickel-cobalt complexes were obtained in the trinuclear form. A novel structure was found in metallacarborane complex 12, with a B-S bond formed at the B(7) site. The molecular structures of 4a, 5a, 6a, 7b, 9a, 9b, 10a and 12 have been determined by X-ray crystallography.