Differing reactivities of (trimpsi)M(CO)(2)(NO) complexes [M = V,Nb, Ta; trimpsi = (t)BuSi(CH(2)PMe(2))(3)] with halogens and halogen sources

Treatment of (trimpsi)V(CO)(2)(NO) (trimpsi = (t)BuSi(CH(2)PMe(2))(3)) with 1 equiv of PhICl(2) or C(2)Cl(6) or 2 equiv of AgCl affords (trimpsi)V(NO)Cl(2) (1) in moderate yields. Likewise, (trimpsi)V(NO)Br(2) (2) and (trimpsi)V(NO)I(2) (3) are formed by the reactions of (trimpsi)V(CO)(2)(NO) with Br(2) and I(2), respectively. The complexes (trimpsi)M(NO)I(2)(PMe(3)) (M = Nb, 4; Ta, 5) can be isolated in moderate to low yields when the (trimpsi)M(CO)(2)(NO) compounds are sequentially treated with 1 equiv of I(2) and excess PMe(3). The reaction of (trimpsi)V(CO)(2)(NO) with 2 equiv of ClNO forms 1 in low yield, but the reactions of (trimpsi)M(CO)(2)(NO) (M = Nb, Ta) with 1 equiv of ClNO generate (trimpsi)M(NO)(2)Cl (M = Nb, 6; Ta, 7). Complexes 6 and 7 are thermally unstable and decompose quickly at room temperature; consequently, they have been characterized solely by IR and (31)P[(1)H] NMR spectroscopies. All other new complexes have been fully characterized by standard methods, and the solid-state molecular structures of 1.3CH(2)Cl(2), 4.(3/4)CH(2)Cl(2), and 5.THF have been established by single-crystal X-ray diffraction analyses. A convenient method of generating Cl(15)NO has also been developed during the course of these investigations.     

Bridging nitrate groups in [Mn(4)O(3)(NO(3))(O(2)CMe)(3)(R(2)dbm)(3)] (R = H, Et) and [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)): acidolysis routes to tetranuclear manganese carboxylate complexes

New synthesis procedures are described to tetranuclear manganese carboxylate complexes containing the [Mn(4)O(2)](8+) or [Mn(4)O(3)X](6+) (X(-) = MeCO(2)(-), F(-), Cl(-), Br(-), NO(3)(-)) core. These involve acidolysis reactions of [Mn(4)O(3)(O(2)CMe)(4)(dbm)(3)] (1; dbm is the anion of dibenzoylmethane) or [Mn(4)O(2)(O(2)CEt)(6)(dbm)(2)] (8) with HX (X(-) = F(-), Cl(-), Br(-), NO(3)(-)); high-yield routes to 1 and 8 are also described. The X(-) = NO(3)(-) complexes [Mn(4)O(3)(NO(3))(O(2)CR)(3)(R'(2)dbm)(3)] (R = Me, R' = H (6); R = Me, R' = Et (7); R = Et, R' = H (12)) represent the first synthesis of the [Mn(4)O(3)(NO(3))](6+) core, which contains an unusual eta(1):mu(3)-NO(3)(-) group. Treatment of known [Mn(4)O(2)(O(2)CEt)(7)(bpy)(2)](ClO(4)) with HNO(3) gives [Mn(4)O(2)(NO(3))(O(2)CEt)(6)(bpy)(2)](ClO(4)) (15) containing a eta(1):eta(1):mu-NO(3)(-) group bridging the two body Mn(III) ions of the [Mn(4)O(2)](8+) butterfly core. Complex 7 x 4CH(2)Cl(2) crystallizes in space group P2(1)2(1)2(1) with (at -168 degrees C) a = 21.110(3) A, b = 22.183(3) A, c = 15.958(2) A, Z = 4, and V = 7472.4(3) A(3). Complex 15 x (3)/(2)CH(2)Cl(2) crystallizes in space group P2(1)/c with (at -165 degrees C) a = 26.025(4) A, b = 13.488(2) A, c = 32.102(6) A, beta = 97.27(1) degrees, Z = 8, and V = 11178(5) A(3). Complex 7 contains a [Mn(4)(mu(3)-O)(3)(mu(3)-NO(3))](6+) core (3Mn(III), Mn(IV)) as seen for previous [Mn(4)O(3)X](6+) complexes. Complex 15 contains a butterfly [Mn(4)(mu(3)-O)(2)](8+) core. (1)H NMR spectra have been recorded for all complexes reported in this work and the various resonances assigned. All complexes retain their structural integrity on dissolution in chloroform and dichloromethane. Magnetic susceptibility (chi(M)) data were collected on 12 in the 5-300 K range in a 10.0 kG (1 T) field. Fitting of the data to the theoretical chi(M) vs T expression appropriate for a [Mn(4)O(3)X](6+) complex of C(3)(v)() symmetry gave J(34) = -23.9 cm(-)(1), J(33) = 4.9 cm(-)(1), and g = 1.98, where J(34) and J(33) refer to the Mn(III)Mn(IV) and Mn(III)Mn(III) pairwise exchange interactions, respectively. The ground state of the molecule is S = 9/2, as found previously for other [Mn(4)O(3)X](6+) complexes. This was confirmed by magnetization data collected at various fields and temperatures. Fitting of the data gave S = 9/2, D = -0.45 cm(-1), and g = 1.96, where D is the axial zero-field splitting parameter.     

Nitrosyl-Metallkoordinationsverbindungen. VI. Synthese und Eigenschaften von Cobalt- und Eisenkomplexen des Typs M(S,S)(P,P)NO

Nitrosyl Metal Coordination Compounds. VI. Syntheses and Properties of Cobalt and Iron Complexes of the Type M(S,S)(P,P)NO Penta-coordinated neutral complexes of the composition M(S,S)(P,P)NO, with M = Co, Fe; S,S = malonitrildithiolate (mnt), P,P = tetraphenylethylenediphosphine (diphos), and triphenylphosphine (PPh₃) have been synthesized and investigated by means of molecular weights measurement, IR, UV/VIS, and ESCA spectroscopy as well as magnetic measurements. Square pyramidale and trigonal bipyramidale structures are discussed.     

A comparison of the influences of alkoxide and thiolate ligands on the electronic structure and reactivity of molybdenum(3+) and tungsten(3+) complexes. preparation and structures of M(2)(O(T)Bu)(2)(S(t)Bu)(4), [Mo(S(t)Bu)(3)(NO)](2), and W(S(t)Bu)(3)(NO)(py)

M(2)(O(t)Bu)(6) compounds (M = Mo, W) react in hydrocarbon solvents with an excess of (t)BuSH to give M(2)(O(t)Bu)(2)(S(t)Bu)(4), red, air- and temperature-sensitive compounds. (1)H NMR studies reveal the equilibrium M(2)(O(t)Bu)(6) + 4(t)BuSH <==> M(2)(O(t)Bu)(2)(S(t)Bu)(4) + 4(t)BuOH proceeds to the right slowly at 22 degrees C. The intermediates M(2)(O(t)Bu)(4)(S(t)Bu)(2), M(2)(O(t)Bu)(3)(S(t)Bu)(3), and M(2)(O(t)Bu)(5)(S(t)Bu) have been detected. The equilibrium constants show the M-O(t)Bu bonds to be enthalpically favored over the M-S(t)Bu bonds. In contrast to the M(2)(O(t)Bu)(6) compounds, M(2)(O(t)Bu)(2)(S(t)Bu)(4) compounds are inert with respect to the addition of CO, CO(2), ethyne, (t)BuC triple bond CH, MeC triple bond N, and PhC triple bond N. Addition of an excess of (t)BuSH to a hydrocarbon solution of W(2)(O(t)Bu)(6)(mu-CO) leads to the rapid expulsion of CO and subsequent formation of W(2)(O(t)Bu)(2)(S(t)Bu)(4). Addition of an excess of (t)BuSH to hydrocarbon solutions of [Mo(O(t)Bu)(3)(NO)](2) and W(O(t)Bu)(3)(NO)(py) gives the structurally related compounds [Mo(S(t)Bu)(3)(NO)](2) and W(S(t)Bu)(3)(NO)(py), with linear M-N-O moieties and five-coordinate metal atoms. The values of nu(NO) are higher in the related thiolate compounds than in their alkoxide counterparts. The bonding in the model compounds M(2)(EH)(6), M(2)(OH)(2)(EH)(4), (HE)(3)M triple bond CMe, and W(EH)(3)(NO)(NH(3)) and the fragments M(EH)(3), where M = Mo or W and E = O or S, has been examined by DFT B3LYP calculations employing various basis sets including polarization functions for O and S and two different core potentials, LANL2 and relativistic CEP. BLYP calculations were done with ZORA relativistic terms using ADF 2000. The calculations, irrespective of the method used, indicate that the M-O bonds are more ionic than the M-S bonds and that E ppi to M dpi bonding is more important for E = O. The latter raises the M-M pi orbital energies by ca. 1 eV for M(2)(OH)(6) relative to M(2)(SH)(6). For M(EH)(3) fragments, the metal d(xz)(),d(yz)() orbitals are destabilized by OH ppi bonding, and in W(EH)(3)(NO)(NH(3)) the O ppi to M dpi donation enhances W dpi to NO pi* back-bonding. Estimates of the bond strengths for the M triple bond M in M(2)(EH)(6) compounds and M triple bond C in (EH)(3)M triple bond CMe have been obtained. The stronger pi donation of the alkoxide ligands is proposed to enhance back-bonding to the pi* orbitals of alkynes and nitriles and facilitate their reductive cleavage, a reaction that is not observed for their thiolate counterpart.     

Synthesis, characterization, and reactivity of [Ru(bpy)(CH3CN)3(NO2)]PF6, a synthon for [Ru(bpy)(L3)NO2] complexes

We report a high yield, two-step synthesis of fac-[Ru(bpy)(CH3CN)3NO2]PF6 from the known complex [(p-cym)Ru(bpy)Cl]PF6 (p-cym = eta(6)-p-cymene). [(p-cym)Ru(bpy)NO2]PF6 is prepared by reacting [(p-cymene)Ru(bpy)Cl]PF6 with AgNO3/KNO2 or AgNO2. The 15NO2 analogue is prepared using K15NO2. Displacement of p-cymene from [(p-cym)Ru(bpy)NO2]PF6 by acetonitrile gives [Ru(bpy)(CH3CN)3NO2]PF6. The new complexes [(p-cym)Ru(bpy)NO2]PF6 and fac-[Ru(bpy)(CH3CN)3NO2]PF6 have been fully characterized by 1H and 15N NMR, IR, elemental analysis, and single-crystal structure determination. Reaction of [Ru(bpy)(CH3CN)3NO2]PF6 with the appropriate ligands gives the new complexes [Ru(bpy)(Tp)NO2] (Tp = HB(pz)3-, pz = 1-pyrazolyl), [Ru(bpy)(Tpm)NO2]PF6 (Tpm = HC(pz)3), and the previously prepared [Ru(bpy)(trpy)NO2]PF6 (trpy = 2,2',6',2' '-terpyridine). Reaction of the nitro complexes with HPF6 gives the new nitrosyl complexes [Ru(bpy)TpNO][PF6]2 and [Ru(bpy)(Tpm)NO][PF6]3. All complexes were prepared with 15N-labeled nitro or nitrosyl groups. The nitro and nitrosyl complexes were characterized by 1H and 15N NMR and IR spectroscopy, elemental analysis, cyclic voltammetry, and single-crystal structure determination for [Ru(bpy)TpNO][PF6]2. For the nitro complexes, a linear correlation is observed between the nitro 15N NMR chemical shift and 1/nu(asym), where nu(asym) is the asymmetric stretching frequency of the nitro group.     

Substituent effects on nitrosyl iron corrole complexes Fe(Ar3C)(NO)

A series of nitrosyl tris(5,10,15-aryl)corrolate complexes of iron(III) Fe(Ar3C)(NO) with different substituents on the aryl groups have been prepared, and certain spectroscopic and reaction properties were compared. The cyclic voltammetric analysis of the various Fe(Ar3C)(NO) complexes demonstrated that both the one-electron oxidation and one-electron reduction potentials respond in systematic and nearly identical trends relative to the electron-donor properties of the substituents. A similar pattern was seen in the nitrosyl stretching frequency, nu(NO), which modestly decreased with the stronger donor substituents. Flash photolysis of Fe(Ar3C)(NO) solutions in toluene leads to NO dissociation followed by rapid [NO]-dependent decay of the transients formed (presumably Fe(Ar3C)) to regenerate the original spectra. As was seen in an earlier flash photolysis study of Fe(TNPC)(NO) (TNPC3- = 5,10,15-tris(4-nitro-phenyl)corrolate; Joseph, C.; Ford, P. C. J. Am. Chem. Soc. 2005, 127, 6737-6743), the second-order rate constants, k(NO), are all much faster ((1-9) x 10(8) M(-1) s(-1) at 298 K) than those for analogous iron(III) complexes of porphyrins. However, on a more microscopic level there is no obvious pattern in these rates with respect to the donor properties of the aryl ring substituents. The high reactivity of the ferric triarylcorrolates with NO data is interpreted in terms of the strongly electron-donating character of the Ar3C3- ligand and the quartet electronic configuration of the Fe(Ar3C) intermediate.     

Reactivity of 2-pyridinecarboxylic esters with cadmium(II) halides: study of (113)Cd NMR solid state spectra and crystal structures of hexacoordinated complexes [CdI(2)(C(5)H(4)NCOOMe)(2)] and [CdI(2)(C(5)H(4)NCOOPr(n))(2)

The series of complexes [CdX(2)(C(5)H(4)NCOOR)] (X = Cl or Br; R = Me, Et, Pr(n)() or Pr(i)()) and [CdX(2)(C(5)H(4)NCOOR)(2)] (X = I; R = Me, Et, Pr(n)(), or Pr(i)()) have been obtained by the addition reaction of esters of 2-pyridinecarboxylic acid to cadmium(II) halides. X-ray crystal structures of two complexes [CdI(2)(C(5)H(4)NCOOR)(2)], R = Me (10) and R = Pr(n)() (12), have been determined. In both cases, the structure consists of discrete neutral monomeric units where the cadmium atom has a distorted octahedral coordination with CdI(2)N(2)O(2) core, two halides being in cis disposition. Structural information is compared with that deduced from (113)Cd CPMAS NMR experiments. Chemical shift anisotropies are discussed in terms of distortions produced in cadmium octahedra. The orientation of the principal axes of (113)Cd shielding tensor is also analyzed and related to the disposition of ligands in the structures of two analyzed compounds.     

配合物[Ln(C6H5COO)2(NO3)(Bipy)]2的合成及表征

镧系含杂环胺三元配合物的研究从六十年代至今已进行了大量探索 ,但四元配合物的研究一直不多 ,并且由于联吡啶 (Ｂｉｐｙ)的配位能力相对较弱 ,有关其四元配合物的研究报道更为少见[1～ 3] 。我们探索合成了 [Ｌｎ(Ｃ6 Ｈ5ＣＯＯ) 2 (ＮＯ3)(Ｂｉｐｙ) ]2 ,且在合成过程中首次观察到了热力学与动力学竞争的现象。1　实验部分1 1　试剂和仪器稀土氧化物纯度超过 99.99% (上海跃龙有色金属有限公司 ) ,其余试剂均为分析纯。ＣａｒｌｏＥｒｂａ 1 1 0 6型元素分析仪 ;ＤＤＳ 1 1Ａ型电导率仪 (1 .0× 1 0 -3ｍｏｌ·Ｌ-1ＤＭＦ) ;日本岛津 47…     

Co(x)Cu(1-x)(DDOP)(OH2)(NO3)](NO3): hydrogen bond-driven distortion of cobalt(II) by solid solution 'network mismatch'

Late-first row transition metal nitrate complexes of the tetradentate N-donor ligand cis-3,5-bis[(2-pyridinyleneamino]-trans-hydroxycyclohexane (DDOP) adopt a mono-cationic [M(DDOP)(H(2)O)(NO(3))](+) structure (M = Co, 1; Cu, 2; Zn, 3) in which the DDOP ligand occupies the equatorial plane. The complexes are essentially isostructural and isomorphous, allowing the Co(II) and Cu(II) complexes to co-crystallize in mixed-metal solid solutions with the formula [Co(x)Cu(1-x)(DDOP)(NO(3))(H(2)O)](NO(3)), where x = 0.4 (4), 0.1 (5), and 0.7 (6). For 4, structural and magnetochemical analysis indicate that the geometry of the octahedral Co(II) complex distorts to match that of the dominant Jahn-Teller distorted Cu(II) center. Magnetic susceptibility data of octahedral Co(II) are sensitive to ligand geometry distortions and have been analyzed accordingly, comparing 4 to the reference systems 1 and 2. Bond valence calculations have been used to estimate the relative stabilities of the six hydrogen bonded networks, suggesting that the stretching of the Co(II) coordination sphere 4 in is assisted by adoption of the most stable hydrogen bonded network; but that in 6 this is overcome by a higher loading of Co. This family of complexes therefore represent predictable metal-based tectons which can help probe the influence of secondary non-covalent interactions over metal coordination geometries and properties.     

The Dinitramide Anion, N(NO(2))(2)(-)

The infrared and Raman spectra of the NH(4)(+), K(+), and Cs(+) salts of N(NO(2))(2)(-) in the solid state and in solution have been measured and are assigned with the help of ab initio calculations at the HF/6-31G and MP2/6-31+G levels of theory. In agreement with the variations observed in the crystal structures, the vibrational spectra of the N(NO(2))(2)(-) anion are also strongly influenced by the counterions and the physical state. Whereas the ab initio calculations for the free N(NO(2))(2)(-) ion indicate a minimum energy structure of C(2) symmetry, Raman polarization measurements on solutions of the N(NO(2))(2)(-) anion suggest point group C(1) (i.e., no symmetry). This is attributed to the very small (<3 kcal/mol) N-NO(2) rotational barrier in N(NO(2))(2)(-) which allows for easy deformation.     

Variable pi-bonding in iron(II) porphyrinates with nitrite, CO, and tert-butyl isocyanide: characterization of [Fe(TpivPP)(NO2)(CO)]-

The addition of the strongly pi-bonding ligands CO or tert-butyl isocyanide to the low-spin five-coordinate iron(II) nitrite species [Fe(TpivPP)(NO2)]- (TpivPP = picket fence porphyrin) gives two new six-coordinate species [Fe(TpivPP)(NO2)(CO)]- and [Fe(TpivPP)(NO2)(t-BuNC)]-. These species have been characterized by single-crystal structure determinations and by UV-vis, IR, and M?ssbauer spectroscopies. All evidence shows that in the mixed-ligand iron(II) porphyrin species, [Fe(TpivPP)(NO2)(CO)]-, the two trans, pi-accepting ligands CO and nitrite compete for pi density. The CO ligand however dominates the bonding. The Fe-N(NO2) bond lengths for the two independent anions in the unit cell at 2.006(4) and 2.009(4) A are lengthened compared to other nitrite species with either no trans ligands or non-pi-accepting trans ligands to nitrite. The Fe-C(CO) bond lengths are 1.782(4) A and 1.789(5) A for the two anions. The two Fe-C-O angles at 175.5(4) and 177.5(4) degrees are essentially linear in both anions. The quadrupole splitting for [Fe(TpivPP)(NO2)(CO)]- was determined to be 0.32 mm/s, and the isomer shift was 0.18 mm/s at room temperature in zero applied field. Both of the M?ssbauer parameters are much smaller than those found for six-coordinate low-spin iron(II) porphyrinates with neutral nitrogen-donating ligands as well as iron(II) nitro complexes. However, the M?ssbauer parameters are typical of other six-coordinate CO porphyrinates signifying that CO is the more dominant ligand. The CO stretching frequency of 1974 cm(-1) is shifted only slightly to higher energy compared to six-coordinate CO complexes with neutral nitrogen-donor ligands trans to CO. Crystal data for [K(222)][Fe(TpivPP)(NO2)(CO)].1/2C6H5Cl: monoclinic, space group P2(1)/c, Z = 8, a = 33.548(6) A, b = 18.8172(15) A, c = 27.187(2) A, beta = 95.240(7) degrees, V = 17091(4) A3.     

Na(23)K(9)Tl(15.3): An Unusual Zintl Compound Containing Apparent Tl(5)(7)(-), Tl(4)(8)(-), Tl(3)(7)(-), and Tl(5)(-) Anions

Reaction of the neat elements in tantalum containers at 400 degrees C and then 150 degrees C gives the pure title phase. X-ray crystallography shows that the hexagonal structure (P6(3)/mmc, Z = 2, a = 11.235(1) ?, b = 30.133(5) ?) contains relatively high symmetry clusters Tl(5)(7)(-) (D(3)(h)()), Tl(4)(8)(-) (C(3)(v)(), approximately T(d)), and the new Tl(3)(7)(-) (D(infinity)(h)()) plus Tl(5)(-), the last two disordered over the same elongated site in 1:2 proportions. Cation solvation of these anions is tight and specific, providing good Coulombic trapping of weakly bound electrons on the isolated cluster anions. The observed disorder makes the compound structurally a Zintl phase with a closed shell electron count. EHMO calculations on the novel Tl(3)(7)(-) reveal some bonding similarities with the isoelectronic CO(2), with two good sigma(s,p) bonding and two weakly bonding pi MO's. The Tl-Tl bond lengths therein (3.14 ?) are evidently consistent with multiple bonding. The weak temperature-independent paramagnetism and metallic conductivity (rho(293) approximately 90 &mgr;Omega.cm) of the phase are discussed.     

Synthesis,characterization, and solution redox properties of (trimpsi)M(CO)(2)(NO) complexes [M = V,Nb, Ta; trimpsi = (t)BuSi(CH(2)PMe(2))(3)

Treatment of [Et(4)N][M(CO)(6)] (M = Nb, Ta) with I(2) in DME at -78 degrees C produces solutions of the bimetallic anions [M(2micro-I)(3)(CO)(8)](-). Addition of the tripodal phosphine (t)BuSi(CH(2)PMe(2))(3) (trimpsi) followed by refluxing affords (trimpsi)M(CO)(3)I [M = Nb (1), Ta (2)], which are isolable in good yields as air-stable, orange-red microcrystalline solids. Reduction of these complexes with 2 equiv of Na/Hg, followed by treatment with Diazald in THF, results in the formation of (trimpsi)M(CO)(2)(NO) [M = Nb (3), Ta (4)] in high isolated yields. The congeneric vanadium complex, (trimpsi)V(CO)(2)(NO) (5), can be prepared by reacting [Et(4)N][V(CO)(6)] with [NO][BF(4)] in CH(2)Cl(2) to form V(CO)(5)(NO). These solutions are treated with 1 equiv of trimpsi to obtain (eta(2)-trimpsi)V(CO)(3)(NO). Refluxing orange THF solutions of this material affords 5 in moderate yields. Reaction of (trimpsi)VCl(3)(THF) (6) with 4 equiv of sodium naphthalenide in THF in the presence of excess CO provides [Et(4)N][(trimpsi)V(CO)(3)] (7), (trimpsi)V(CO)(3)H, and [(trimpsi)V(micro-Cl)(3)V(trimpsi)][(eta(2)-trimpsi)V(CO)(4)].3THF ([8][9].3THF). All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2.(1)/(2)THF, 3-5, and [8][9].3THF have been established by X-ray diffraction analyses. The solution redox properties of 3-5 have also been investigated by cyclic voltammetry. Cyclic voltammograms of 3 and 4 both exhibit an irreversible oxidation feature in CH(2)Cl(2) (E(p,a) = -0.71 V at 0.5 V/s for 3, while E(p,a) = -0.55 V at 0.5 V/s for 4), while cyclic voltammograms of 5 in CH(2)Cl(2) show a reversible oxidation feature (E(1/2) = -0.74 V) followed by an irreversible feature (0.61 V at 0.5 V/s). The reversible feature corresponds to the formation of the 17e cation [(trimpsi)V(CO)(2)(NO)](+) ([5](+)()), and the irreversible feature likely involves the oxidation of [5](+)() to an unstable 16e dication. Treatment of 5 with [Cp(2)Fe][BF(4)] in CH(2)Cl(2) generates [5][BF(4)], which slowly decomposes once formed. Nevertheless, [5][BF(4)] has been characterized by IR and ESR spectroscopies.     

Reactivity of the hydrido/nitrosyl radical MHCl(NO)(CO)(P(i)Pr(3))(2), M = Ru, Os

The reaction of equimolar NO with the 16 electron molecule RuHCl(CO)L(2) (L = P(i)Pr(3)) proceeds, via a radical adduct RuHCl(CO)(NO) L(2), onward to form RuCl(NO)(CO)L(2) (X-ray structure determination) and RuHCl(HNO)(CO)L(2), in a 1:1 mole ratio. The HNO ligand, bound by N and trans to hydride, is rapidly degraded by excess NO. The osmium complex behaves analogously, but the adduct has a higher formation constant, permitting determination of its IR spectrum; both MHCl(CO)(NO)L(2) radicals are characterized by EPR spectroscopy, and DFT calculations on the Ru system show it to have a "half-bent" Ru-N-O unit with the spin density mainly on nitrogen. DFT (PBE) energies rule out certain possible mechanistic steps for forming the two products. A survey of the literature leads to the hypothesis that NO should generally be considered as a (neutral) Lewis base (2-electron donor) when it binds to a 16 electron complex which is resistant to oxidation or reduction, and that the resulting N-centered radical has a M-N-O angle of approximately 140 degrees, which distinguishes it from NO(-) (bent at <140 degrees ) and from NO(+) (>170 degrees ).     

Synthesis and structure of W(eta(2)-mp)(2)(CO)(3) (mp = monoanion of 2-mercaptopyridine) and its reactions with 2,2'-pyridine disulfide and/or NO to yield W(eta(2)-mp)(4), W(eta(2)-mp)(2)(NO)(2), and W(eta(2)-mp)(3)(NO)

Oxidative addition of the sulfur-sulfur bond of 2,2'-pyridine disulfide (C(5)H(4)NS-SC(5)H(4)N) with L(3)W(CO)(3) [L = pyridine, (1)/(3)CHPT; CHPT = cycloheptatriene] in methylene chloride solution yields the seven-coordinate W(II) thiolate complex W(eta(2)-mp)(2)(CO)(3) (mp = monoanion of 2-mercaptopyridine). This complex undergoes slow further oxidative addition with additional pyridine disulfide, yielding W(eta(2)- mp)(4). Reaction of W(eta(2)-mp)(2)(CO)(3) with NO results in quantitative formation of the six-coordinate W(0) complex W(eta(2)-mp)(2)(NO)(2). Reaction of W(eta(2)-mp)(2)(CO)(3) with NO in the presence of added pyridine disulfide yields the seven-coordinate W(II) nitrosyl complex W(eta(2)-mp)(3)(NO) as well as W(eta(2)-mp)(2)(NO)(2) and trace amounts of W(eta(2)-mp)(4). The complex W(eta(2)-mp)(3)(NO) is formed during the course of the reaction and not by reaction of W(eta(2)-mp)(4) or W(eta(2)-mp)(2)(NO)(2) with NO under these conditions. The crystal structures of W(eta(2)- mp)(2)(CO)(3), W(eta(2)-mp)(2)(NO)(2), and W(eta(2)-mp)(3)(NO) are reported.     

Monoanionic {Mn(NO)}5 and dianionic {Mn(NO)}6 thiolatonitrosylmanganese complexes: [(NO)Mn(L)2]- and [(NO)Mn(L)2]2- (LH2 = 1,2-benzenedithiol and toluene-3,4-dithiol)

The reaction of MnBr(2) and [PPN](2)[S,S-C(6)H(3)-R] (1:2 molar ratio) in THF yielded [(THF)Mn(S,S-C(6)H(3)-R)(2)](-) [R = H (1a), Me (1b); THF = tetrahydrofuran]. Formation of the dimeric [Mn(S,S-C(6)H(3)-R)(2)](2)(2-) [R = H (2a), Me (2b)] was presumed to compensate for the electron-deficient Mn(III) core via two thiolate bridges upon dissolution of complexes 1a and 1b in CH(2)Cl(2). Complex 2a displays antiferromagnetic coupling interaction between two Mn(III) centers (J = -52 cm(-1)), with the effective magnetic moment (mu(eff)) increasing from 0.85 mu(B) at 2.0 K to 4.86 mu(B) at 300 K. The dianionic manganese(II) thiolate complexes [Mn(S,S-C(6)H(3)-R)(2)](2-) [R = H (3a), Me (3b)] were isolated upon the addition of [BH(4)](-) into complexes 1a and 1b or complexes 2a and 2b, respectively. The anionic mononuclear {Mn(NO)}(5) thiolatonitrosylmanganese complexes [(NO)Mn(S,S-C(6)H(3)-R)(2)](-) [R = H (4a), Me (4b)] were obtained from the reaction of NO(g) with the anionic complexes 1a and 1b, respectively, and the subsequent reduction of complexes 4a and 4b yielded the mononuclear {Mn(NO)}(6) [(NO)Mn(S,S-C(6)H(3)-R)(2)](2-) [R = H (5a), Me (5b)]. X-ray structural data, magnetic susceptibility measurement, and magnetic fitting results imply that the electronic structure of complex 4a is best described as a resonance hybrid of [(L)(L)Mn(III)(NO(*))](-) and [(L)(L(*))Mn(III)(NO(-))](-) (L = 1,2-benzenedithiolate) electronic arrangements in a square-pyramidal ligand field. The lower IR v(NO) stretching frequency of complex 5a, compared to that of complex 4a (shifting from 1729 cm(-1) in 4a to 1651 cm(-1) in 5a), supports that one-electron reduction occurs in the {(L)(L(*))Mn(III)} core upon reduction of complex 4a.     

The coordination chemistry of selenophosphite ligands. Synthesis and characterization of heterometallic tetranuclear clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)) (M = Cu, Ag; R = (n)Pr, (i)Pr) and [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, Br)

A neutral selenium donor ligand, [CpFe(CO)(2)P(Se)(OR)(2)] is used for the construction of Cu(I) and Ag(I) complexes with a well-defined coordination environment. Four clusters [M{CpFe(CO)(2)P(Se)(OR)(2)}(3)](PF(6)), (where M = Cu, R = (n)Pr, ; R = (i)Pr, and M = Ag, R = (n)Pr, ; R = (i)Pr, ) are isolated from the reaction of [M(CH(3)CN)(4)(PF(6))] (where M = Cu or Ag) and [CpFe(CO)(2)P(Se)(OR)(2)] in a molar ratio of 1 : 3 in acetonitrile at 0 degrees C. The reaction of [CpFe(CO)(2)P(Se)(O(i)Pr)(2)] with cuprous halides in acetone produce two mixed-metal, Cu(I)(2)Fe(II)(2) clusters, [Cu(mu-X) {CpFe(CO)(2)P(Se)(O(i)Pr)(2)}](2) (X = Cl, ; Br, ). All six clusters have been fully characterized spectroscopically ((1)H, (13)C, (31)P, and (77)Se NMR, IR), and by elemental analyses. X-Ray crystal structures of and consist of discrete cationic clusters in which three iron-selenophosphito fragments are linked to the central copper or silver atom via selenium atoms. Both clusters and crystallize in the noncentrosymmetric, hexagonal space group P6[combining macron]2c. The coordination geometry around the copper or silver atom is perfect trigonal-planar with Cu-Se and Ag-Se distances, 2.3505(7) and 2.5581(7) A, respectively. X-Ray crystallography also reveals that each copper center in neutral heterometallic clusters and is trigonally coordinated to two halide ions and a selenium atom from the selenophosphito-iron moiety. The structures can also be delineated as a dimeric unit which is generated by an inversion center and has a Cu(2)X(2) parallelogram core. The dihedral angle between the Cu(2)X(2) plane and the plane composed of Cp ring is found to be 24.62 and 84.58 degrees for compound and , respectively. Hence the faces of two opposite Cp rings are oriented almost perpendicular to the Cu(2)X(2) plane in , but are close to be parallel in . This is the first report of the coordination chemistry of the anionic selenophosphito moiety [(RO)(2)PSe](-), the conjugated base of a secondary phosphine selenide, which acts as a bridging ligand with P-coordination on iron and Se-coordination to copper or silver.     

Anharmonic, temperature, and matrix effects on the molecular structure and vibrational frequencies of lanthanide trihalides LnX3 (Ln = La, Lu; X = F, Cl)

MP2 and CCSD(T) ab initio calculations have been carried out to elucidate geometrical structure and vibrational frequencies of representative lanthanide trihalides LnX(3) (Ln = La, Lu; X = F, Cl) explicitly including temperature, anharmonic, inert-gas matrix, and spin-orbit effects. The results have been compared with gas-phase electron diffraction, gas-phase IR measurements, and IR spectra of molecules trapped in inert-gas matrices. On the Born-Oppenheimer surface LaCl(3), LuF(3), and LuCl(3) adopt trigonal planar (D(3)(h)()) geometry while LaF(3) assumes a slightly pyramidal (C(3)(v)()) structure. Because of normal-mode anharmonicities, the resulting thermal average bond angles are considerably lower than the equilibrium ones, while vibrationally averaged bond lengths are predicted to be longer. The inert-gas matrix effects, modeled by the coordination of two inert-gas molecules LnX(3).IG(2) (IG = Ne, Ar, Xe, and N(2)), are substantial and strongly depend on the polarizability of coordinating particles. Coordinating inert-gas units always favor the tendency of LnX(3) molecules to adopt planar structure and induce noticeable frequency shifts.     

Reactions of nitrogen oxides with heme models. Characterization of NO and NO2 dissociation from Fe(TPP)(NO2)(NO) by flash photolysis and rapid dilution techniques: Fe(TPP)(NO2) as an unstable intermediate

Described are studies directed toward elucidating the controversial chemistry relating to the solution phase reactions of nitric oxide with the iron(II) porphyrin complex Fe(TPP)(NO) (1, TPP = meso-tetraphenylporphinato2-). The only reaction observable with clean NO is the formation of the diamagnetic dinitrosyl species Fe(TPP)(NO)2 (2), and this is seen only at low temperatures (K(1) < 3 M(-1) at ambient temperature). However, 1 does readily react reversibly with N2O3 in the presence of excess NO to give the nitro nitrosyl complex Fe(TPP)(NO2)(NO) (3), suggesting that previous claims that 1 promotes NO disproportionation to give 3 may have been compromised by traces of air in the nitric oxide sources. It is also noted that 3 undergoes reversible loss of NO to give the elusive nitro species Fe(TPP)(NO2) (4), which has been implicated as a powerful oxygen atom transfer agent in reactions with various substrates. Furthermore, in the presence of excess NO2, the latter undergoes oxidation to the stable nitrato analogue Fe(TPP)(NO3) (5). Owing to such reactivity of Fe(TPP)(NO2), flash photolysis and stopped-flow kinetics rather than static techniques were necessary for the accurate measurement of dissociation equilibria characteristic of Fe(TPP)(NO2)(NO) in 298 K toluene solution. Flash photolysis of 3 resulted in competitive NO2 and NO dissociation to give Fe(TPP)(NO) and Fe(TPP)(NO2), respectively. The rate constant for the reaction of 1 with N2O3 to generate Fe(TPP)(NO2)(NO) was determined to be 1.8 x 10(6) M(-1) s(-1), and that for the NO reaction with 4 was similarly determined to be 4.2 x 10(5) M(-1) s(-1). Stopped-flow rapid dilution techniques were used to determine the rate constant for NO dissociation from 3 as 2.6 s(-1). The rapid dilution experiments also demonstrated that Fe(TPP)(NO2) readily undergoes further oxidation to give Fe(TPP)(NO3). The mechanistic implications of these observations are discussed, and it is suggested that NO2 liberated spontaneously from Fe(P)(NO2) may play a role in an important oxidative process involving this elusive species.