Oxidation reactions of the phosphinidene oxide ligand

The (H-DBU)+ salt of the anionic phosphinidene oxide complex [MoCp(CO)2{P(O)R*}]- (1) (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene; R* = 2,4,6-C6H2tBu3) reacts with different oxidizing agents, displaying a multisite activity located at the Mo and P atoms or at the Mo=P bond. Thus, reaction of 1 with [FeCp2]BF4 gives the dimer [Mo2Cp2(CO)4{P(O)R*}2], and reaction with bromine gives the phosphinous acid complex [MoBrCp{P(OH)(CH2CMe2C6H2tBu2}(CO)2], the latter arising from an unprecedented C-H bond addition to the oxide P=O moiety. In contrast, reaction of 1 with p-benzoquinone occurs at the P site to give the P,O-bound phosphonite complex [MoCp{kappa2-OP(OC6H4OH)R*}(CO)2]. Finally, oxygen or sulfur atoms are added to the Mo=P bond by reaction of 1 with Me2CO2 and S8 to give the novel dioxophosphorane or thiooxophosphorane complexes [MoCp(CO)2{kappa2-EP(O)R*}]- (E = O, S). The thiooxophosphorane anion is a good nucleophile and is methylated at either the S or O positions depending on the electrophile used (MeI or (Me3O)BF4) to give the isomers [MoCp{kappa2-(MeS)P(O)R*}(CO)2] and [MoCp{kappa2-SP(OMe)R*}(CO)2], both having novel organophosphorus ligands.     

Chemistry of the phosphinidene oxide ligand

Reaction of [Mo2Cp2(mu-H)(mu-PHR*)(CO)4] with DBU followed by O2 gives the first anionic phosphinidene oxide complex (H-DBU)[MoCp{P(O)R*}(CO)2] (1) (DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene; R* = 2,4,6-C6H2tBu3). This anion displays three different nucleophilic sites located at the O, P, and Mo atoms, as illustrated by the reactions reported. Thus, reaction of 1 with excess HBF4.OEt2 gave the fluorophosphide complex [MoCp(PFR*)(CO)2] via the hidroxophosphide intermediate [MoCp{PR*(OH)}(CO)2]. Related alkoxyphosphide compounds [MoCp{P(OR)R*}(CO)2] (R = Me, C(O)Ph) were prepared by reaction of 1 with [Me3O]BF4 and PhC(O)Cl, respectively, whereas reaction of 1 with MeI or C3H5Br gave the P,O-bound phosphinite complexes [MoCp(kappa2-OPRR*)(CO)2] (R = Me, C3H5). Metal-based electrophiles were found to bind at either O or Mo positions. Thus, reaction of 1 with [ZrCl2Cp2] gave the phosphinidene oxide bridged [MoCp{P(OZrClCp2)R*}(CO)2], whereas reaction with SnPh3Cl gave trans-[MoCp{P(O)R*}(CO)2(SnPh3)], an heterometallic complex having an intact terminal P(O)R* ligand.     

Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3− (A=As,Sb, Bi) Complexes

Heteronuclear transition‐metal–main‐group‐element carbonyl complexes of AsFe(CO)₃⁻, SbFe(CO)₃⁻, and BiFe(CO)₃⁻ were produced by a laser vaporization supersonic ion source in the gas phase, and were studied by mass‐selected IR photodissociation spectroscopy and advanced quantum chemistry methods. These complexes have C_3v structures with all of the carbonyl ligands bonded on the iron center, and feature covalent triple bonds between bare Group 15 elements and Fe(CO)₃⁻. Chemical bonding analyses on the whole series of AFe(CO)₃⁻ (A=N, P, As, Sb, Bi, Mc) complexes indicate that the valence orbitals involved in the triple bonds are hybridized 3d and 4p atomic orbitals of iron, leading to an unusual (dp–p) type of transition‐metal–main‐group‐element multiple bonding. The σ‐type three‐orbital interaction between Fe 3d/4p and Group 15 np valence orbitals plays an important role in the bonding and stability of the heavier AFe(CO)₃⁻ (A=As, Sb, Bi) complexes.     

Triple Bonds Between Iron and Heavier Group 15 Elements in AFe(CO)3− (A=As,Sb, Bi) Complexes

Heteronuclear transition‐metal–main‐group‐element carbonyl complexes of AsFe(CO)₃^?, SbFe(CO)₃^?, and BiFe(CO)₃^? were produced by a laser vaporization supersonic ion source in the gas phase, and were studied by mass‐selected IR photodissociation spectroscopy and advanced quantum chemistry methods. These complexes have C_3v structures with all of the carbonyl ligands bonded on the iron center, and feature covalent triple bonds between bare Group 15 elements and Fe(CO)₃^?. Chemical bonding analyses on the whole series of AFe(CO)₃^? (A=N, P, As, Sb, Bi, Mc) complexes indicate that the valence orbitals involved in the triple bonds are hybridized 3d and 4p atomic orbitals of iron, leading to an unusual (dp–p) type of transition‐metal–main‐group‐element multiple bonding. The σ‐type three‐orbital interaction between Fe 3d/4p and Group 15 np valence orbitals plays an important role in the bonding and stability of the heavier AFe(CO)₃^? (A=As, Sb, Bi) complexes.     

Structures and bonding of the sandwich complexes [Ti(eta5-E5)2]2- (E = CH,N, P,As, Sb): a theoretical study

Quantum chemical calculations using gradient-corrected DFT at the BP86/TZ2P level of the compounds [Ti(eta(5)-E(5))(2)](2)(-) (E = CH, N, P, As, Sb) are reported. The nature of the metal-ligand bonding has been analyzed with an energy decomposition method, and the results are compared with [Fe(eta(5)-E(5))(2)]. The bonding in both series of complexes is more covalent than electrostatic. The energy decomposition analysis shows that the dominant orbital interactions in the negatively charged titanium species come from the (e(2)') Ti --> [(eta(5)-E(5))(2)](2)(-) back-donation (delta bonding) while the covalent bonding in the iron complexes come mainly from (e(1)' ') (Cp(-))(2) --> Fe(2+) donation (pi bonding). The nature of the metal-ligand interactions does not change very much for different ligands cyc-E(5) within the two series of compounds. The calculated bond dissociation energies for breaking one metal-ligand bond of the molecules [Ti(eta(5)-E(5))(2)](2)(-) shows for E the order P > As > Sb > N > CH. The central message of this work is that the complexes [Ti(eta(5)-E(5))(2)](2)(-) are delta bonded molecules.     

Electronic structures and properties of eight-coordinate metal-polyarsenic complexes MAs8n- (M = V,Nb, Ta,Cr, Mo,W, Mn,Tc, Re)

The eight-coordinate early transition metal polyarsenic complexes, MAs(8)3- (M = V, Nb, Ta), MAs(8)2- (M = Cr, Mo, W), and MAs8- (M = Mn, Tc, Re), have been studied using density functional theory (DFT). The geometry optimizations of these complexes indicate that in the most stable structures the transition metal atoms are trapped in a crownlike cavity consisting of a zigzag eight-membered ring of As8 cluster. The scalar-relativistic effects and spin-orbit coupling effects on the electronic structures and energy levels were taken into account. The stabilities of gas-phase MAs8n- ions and bonding between the As8 ring and early transition metals are discussed on the basis of population analysis, atomization energies, and decomposition reaction energies. All these complex ions are found to be diamagnetic with notable HOMO-LUMO energy gaps. The vibrational frequencies and infrared absorption intensities of the MAs8n- series are predicted theoretically. Brief theoretical calculations of the similar MoA(8)2- pnictide ions indicate that the analogous P, Sb, and even Bi complexes are likely to be stable, whereas the crownlike MoN(8)2- is not a stable complex.     

Hexacoordinate planar main group atoms centered in hexagonal hydrocopper complexes Cu6H6X (X = Si, P, As)

Ab initio theoretical evidence of hexacoordinate planar main group atoms centered in hexagonal hydrocopper complexes Cu(6)H(6)X (X = Si, P, As) is presented at the density functional theory level in this work. The results obtained extend the bonding capacity of silicon, phosphorus, and arsenic to planar hexacoordination in hydrocopper complexes which are important in fundamental research and may shed new insight into catalyst chemistry.     

Stern-Gerlach experiments of one-dimensional metal-benzene sandwich clusters: Mn(C6H6)m (M = Al, Sc, Ti, and V)

A molecular beam of multilayer metal-benzene organometallic clusters Mn(C6H6)m (M = Al, Sc, Ti, and V) was produced by a laser vaporization synthesis method, and their magnetic deflections were measured. Multidecker sandwich clusters of transition-metal atoms and benzene Scn(C6H6)n+1 (n = 1, 2) and Vn(C6H6)n+1 (n = 1-4) possess magnetic moments that increase monotonously with n. The magnetic moments of Al(C6H6), Scn(C6H6)n+1, and Vn(C6H6)n+1 are smaller than that of their spin-only values as a result of intracluster spin relaxation, an effect that depends on the orbital angular momenta and bonding characters of the orbitals containing electron spin. While Ti(C6H6)2 was found to be nonmagnetic, Tin(C6H6)n+1 (n = 2, 3) possess nonzero magnetic moments. The mechanism of ferromagnetic spin ordering in M2(C6H6)3 (M = Sc, Ti, V) is discussed qualitatively in terms of molecular orbital analysis. These sandwich species represent a new class of one-dimensional molecular magnets in which the transition-metal atoms are formally zerovalent.     

Cl(3)V(mu-S(CH(3))(2))(3)VCl(3)(2)(-): a first-row,face-shared bioctahedral complex with multiple metal-metal bonding

Density functional theory calculations have been used to investigate the structure and bonding of the d(3)d(3) bioctahedral complexes X(3)V(mu-S(CH(3))(2))(3)VX(3)(2)(-) (X = F(-), Cl(-), OH(-), SH(-), NH(2)(-)). According to geometry optimizations using the broken-symmetry approach and the VWN+B-LYP combination of density functionals, the halide-terminated complexes have a V-V bond order of approximately 2, while complexes featuring OH(-), SH(-), or NH(2)(-) as terminal ligands exhibit full triple bonding between the vanadium atoms. The tendency toward triple bonding in the latter complexes is consistent with an increased covalency of the vanadium-ligand bonds, and the influence of bond covalency is apparent also in the tendency for V-V bond elongation in the complexes with OH(-) and NH(2)(-) terminal ligands. Detailed examination of the composition of molecular orbitals in all of the thioether-bridged V(II) complexes substantiates the conclusion that the strong antiferromagnetic coupling which we have determined for these complexes (-J > 250 cm(-)(1)) is due to direct bonding between metal atoms rather than superexchange through the bridging ligands. As such, these V(II) complexes comprise the first apparent examples of multiple metal-metal bonding in first-transition-row, face-shared dinuclear complexes and are therefore of considerable structural and synthetic interest.     

Luminescent piano-stool complexes incorporating 1-(4-cyanophenyl)imidazole: synthesis, spectral, and structural studies

Three novel luminescent piano-stool arene ruthenium complexes of general formula [(eta(6)-arene)RuCl(2)(CPI)] (eta(6)-arene = benzene, 1, p-cymene, 2, and hexamethylbenzene, 3; CPI=1-(4-cyanophenyl)imidazole were prepared. The molecular structures of 2 and 3 were determined crystallographically. Reaction of 1-3 with EPh(3) (E = P, As, or Sb) and N-N donor bases such as 2,2'-bipyridine and 1,10-phenanthroline afforded cationic mononuclear complexes of general formula [(eta(6)-arene)RuCl(CPI)(EPh(3))](+) (eta(6)-arene = C(6)H(6), E = P (1a), E = As (1b), E = Sb(1c); eta(6)-arene = C(10)H(14), E = P (2a), E = As (2b), E = Sb (2c); eta(6)-arene = C(6)Me(6), E = P (3a), E = As (3b), E = Sb (3c)) and [(eta(6)-arene)Ru(N-N)(CPI)](2+) (eta(6)-arene = C(6)H(6), N-N = bipy (1d), N-N = phen (1e); eta(6)-arene = C(10)H(14), N-N = bipy (2d), N-N = phen (2e); eta(6)-arene = C(6)Me(6), N-N = bipy (3d), N-N = phen (3e)). Molecular structures of 1a and 2a were also confirmed by X-ray crystallography. Structural studies of the complexes 2, 3, 1a, and 2a supported coordination of CPI through the imidazole nitrogen and the presence of a pendant nitrile group. Structural data also revealed stabilization of crystal packing in the complexes 2, 3, and 2a by C-H...X (X = Cl, F) type inter- and intramolecular interactions and in complex 1a by pi-pi stacking. Moreover, neutral homonuclear bimetallic complexes 2f,g were prepared by using complex 2 as a metallo-ligand, where CPI acts as a bridge between two metal centers. Emission spectra of the mononuclear complexes [(eta(6)-arene)RuCl(2)(CPI)] and its derivatives exhibited intense luminescence when excited in the metal to ligand charge-transfer band.     

Reactions of halofluorocarbons with group 6 complexes M(C(5)H(5))(2)L (M = Mo, W; L = C(2)H(4), CO). Fluoroalkylation at molybdenum and tungsten, and at cyclopentadienyl or ethylene ligands.

The molybdenum(II) and tungsten(II) complexes [MCp(2)L] (Cp = eta(5)-cyclopentadienyl; L = C(2)H(4), CO) react with perfluoroalkyl iodides to give a variety of products. The Mo(II) complex [MoCp(2)(C(2)H(4))] reacts with perfluoro-n-butyl iodide or perfluorobenzyl iodide with loss of ethylene to give the first examples of fluoroalkyl complexes of Mo(IV), MoCp(2)(CF(2)CF(2)CF(2)CF(3))I (8) and MoCp(2)(CF(2)C(6)F(5))I (9), one of which (8) has been crystallographically characterized. In contrast, the CO analogue [MoCp(2)(CO)] reacts with perfluorobenzyl iodide without loss of CO to give the crystallographically characterized salt, [MoCp(2)(CF(2)C(6)F(5))(CO)](+)I(-) (10), and the W(II) ethylene precursor [WCp(2)(C(2)H(4))] reacts with perfluorobenzyl iodide without loss of ethylene to afford the salt [WCp(2)(CF(2)C(6)F(5))(C(2)H(4))](+)I(-) (11). These observations demonstrate that the metal-carbon bond is formed first. In further contrast the tungsten precursor [WCp(2)(C(2)H(4))] reacts with perfluoro-n-butyl iodide, perfluoro-iso-propyl iodide, and pentafluorophenyl iodide to give fluoroalkyl- and fluorophenyl-substituted cyclopentadienyl complexes WCp(eta(5)-C(5)H(4)R(F))(H)I (12, R(F) = CF(2)CF(2)CF(2)CF(3); 15, R(F) = CF(CF(3))(2); 16, R(F) = C(6)F(5)); the Mo analogue MoCp(eta(5)-C(5)H(4)R(F))(H)I (14, R(F) = CF(CF(3))(2)) is obtained in similar fashion. The tungsten(IV) hydrido compounds react with iodoform to afford the corresponding diiodides WCp(eta(5)-C(5)H(4)R(F))I(2) (13, R(F) = CF(2)CF(2)CF(2)CF(3); 18, R(F) = CF(CF(3))(2); 19, R(F) = C(6)F(5)), two of which (13 and 19) have been crystallographically characterized. The carbonyl precursors [MCp(2)(CO)] each react with perfluoro-iso-propyl iodide without loss of CO, to afford the exo-fluoroalkylated cyclopentadiene M(II) complexes MCp(eta(4)-C(5)H(5)R(F))(CO)I (21, M = Mo; 22, M = W); the exo-stereochemistry for the fluoroalkyl group is confirmed by an X-ray structural study of 22. The ethylene analogues [MCp(2)(C(2)H(4))] react with perfluoro-tert-butyl iodide to yield the products MCp(2)[(CH(2)CH(2)C(CF(3))(3)]I (25, M = Mo; 26, M = W) resulting from fluoroalkylation at the ethylene ligand. Attempts to provide positive evidence for fluoroalkyl radicals as intermediates in reactions of primary and benzylic substrates were unsuccessful, but trapping experiments with CH(3)OD (to give R(F)D, not R(F)H) indicate that fluoroalkyl anions are the intermediates responsible for ring and ethylene fluoroalkylation in the reactions of secondary and tertiary fluoroalkyl substrates.     

Electronic structure and bonding studies on triple-decker sandwich complexes with a P6 middle ring

DFT and hybrid HF-DFT studies of structure and bonding of CpMP6MCp triple-decker sandwich complexes, ranging from 18-28 valence electrons (VE) with M=Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W, show that the middle P6 ring complexes adopt symmetric planar (28 valence electron count [VEC]), asymmetric planar (26 VEC), and puckered (24 VEC) geometries. According to the mno Rule, 50 skeletal electrons are needed for these triple-decker cluster frameworks. For 28 VEC, this corresponds to 10 electrons more than the 50 electrons of the mno Rule if all VE of the metal are included. These additional electrons control the distortion of a P6 middle ring and other finer structural details. Completely filled 2a* and 2b* orbitals in 28 VE complexes lead to a planar symmetrical P6 middle ring, while the occupancy in either 2a* or 2b* alone explains the in-plane distortions (asymmetric) in 26 VE complexes. In comparison with 28 VE complexes, the puckering of P6 middle ring in 24 VE complexes is due to the greater stabilization of 5a and the extra stabilization of the +4 oxidation state of Ti. The quintet state of 22 VE complexes is planar as 2a* and 2b* are half filled. Similar geometrical and bonding patterns of CpScP6ScCp and C2P3H2ScC3P3H3ScC2P3H2 support the carbon-phosphorus analogy further. The 18 VE systems, CpScC3B3H6ScCp+ and CpScP3B3H3ScCp+, have the 50 skeletal electrons as stipulated by the mno Rule. Corresponding anions have 52 skeletal electrons (20 VE); the middle rings here are distorted in the plane.     

From coordinated oxophosphinidene to O,O,P-bound arylhypophosphite(2-) to build a singular Mo2Sn2O4P2 metallocycle

P-bound derivatives of the hypophosphorous acids can be prepared from complexed phosphinidene oxides. The anion [MoCp(CO) 2{P(O)R*}] (-)[(H-DBU) (+) salt (R* = 2,4,6-C 6H 2 (t)Bu 3; Cp = eta (5)-C 5H 5) reacts with SnCl 2Ph 2 to give the neutral oxophosphinidene complex [MoCp{P(O)R*}(CO) 2(SnPh 2Cl)] in high yield. Basic hydrolysis of the latter complex occurs readily to yield the novel Mo-Sn metallocyclic derivatives [MoSn{mu- O, P-OP(OH)R*}CpPh 2(CO) 2] and [MoSn{mu- O, O, P-O 2PR*}CpPh(CO) 2] 2. These products display respectively hydrogenhypophosphite(1-) and hypophosphite(2-) anions coordinated through all of their O (to Sn) and P (to Mo) atoms.     

Chemistry of Thiobenzoates: Syntheses, Structures, and NMR Spectra of Salts of [M(SOCPh)(3)](-) (M = Zn, Cd, Hg)

The salts (Ph(4)E)[M(SOCPh)(3)] (M = Zn, Cd, or Hg; E = P or As) are produced by the reaction of Zn(NO(3))(2).6 H(2)O, Cd(NO(3))(2).4H(2)O or HgCl(2) with Et(3)NH(+)PhCOS(-) and (Ph(4)E)X (E = P, X = Br; E = As, X = Cl) in aqueous MeOH in the ratios M(II):PhCOS(-):Ph(4)E(+) = 1:>/=3:>/=1. The crystal structures of (Ph(4)P)[Zn(SOCPh)(3)] (1), (Ph(4)As)[Cd(SOCPh)(3)] (2) and (Ph(4)P)[Hg(SOCPh)(3)] (3) have been determined by single-crystal X-ray diffraction experiments. Crystal data for 1: triclinic; space group P&onemacr;; Z = 2; a = 10.819(2) ?, b = 13.219(3) ?, c = 15.951(3) ?; alpha = 101.75(2) degrees, beta = 97.92(1) degrees, gamma = 109.18(2) degrees. Crystal data for 2: triclinic; space group P&onemacr;; Z= 2; a = 10.741(2) ?, b = 13.168(2) ?, c = 15.809(2) ?; alpha = 101.00(1) degrees, beta = 97.65(1) degrees, gamma = 109.88(1) degrees. Crystal data for 3: monoclinic; space group P2(1)/n; Z = 4; a = 13.302(2) ?, b = 14.276(2) ?, c = 21.108(2) ?; beta = 90.92(1) degrees. The compounds 1 and 2 are isomorphous and isostructural. In the anions [M(SOCPh)(3)](-) the metal atoms have trigonal planar coordination by three sulfur atoms. The metal atoms are further more weakly coordinated intramolecularly to one (M = Hg) or two (M = Zn, Cd) thiobenzoate oxygen atom(s). Using the Bond Valence approach it is found that the contribution of M.O bonding to the total bonding is in the order Cd > Zn > Hg. The metal ((113)Cd, (199)Hg) NMR signals of [M(SOCPh)(3)](-) (M = Cd, Hg) are more shielded than those found for MS(3) kernels in thiolate complexes, a difference attributed to the M(.)O bonding in the thiobenzoate complexes. The (113)Cd resonance of [Cd(SOCPh)(3)](-) in dilute solution is in the region anticipated from dilution data for [Na(Cd{SOCPh}(3))(2)](-).     

Peculiarity in the electronic structure of Cu(II) complex ferromagnetically coupled with bisimino nitroxides

By means of the electron spin resonance (ESR) technique, we have investigated the electronic structures of the tridentate imino nitroxyl diradical complex with copper(II) (Cu-bisimpy), which has a square planar structure and a ground quartet state with an extremely strong ferromagnetic exchange interaction, and its related compounds (bisimpy = 2,6-bis(1'-oxyl-4',4',5',5'-tetramethyl-4',5'-dihydro-1' H-imidazol-2'-yl)pyridine). It was clarified that Cu-bisimpy had unique magnetic orbitals, compared with the biradical ligand (bisimpy), a zinc(II) biradical complex (Zn-bisimpy) and a copper(II) terpyridine complex (Cu-tpy) (tpy = 2,2';6',2'-terpyridine). Multifrequency ESR spectroscopy provided a reliable set of magnetic parameters of Cu-bisimpy, which has a small g anisotropy ( g x = 2.02, g y = 2.01, g z = 2.08) and small hyperfine coupling with Cu (|A x| = 42.0 MHz, |A y|相似文献   

Structure and bonding energy analysis of cationic metal-ylyne complexes of molybdenum and tungsten, [(MeCN)(PMe3)4M≡EMes]+ (M = Mo, W; E = Si, Ge, Sn, Pb): a theoretical study

The molecular and electronic structures and bonding analysis of terminal cationic metal-ylyne complexes (MeCN)(PMe(3))(4)M≡EMes](+) (M = Mo, W; E = Si, Ge, Sn, Pb) were investigated using DFT/BP86/TZ2P/ZORA level of theory. The calculated geometrical parameters for the model complexes are in good agreement with the reported experimental values. The M-E σ-bonding orbitals are slightly polarized toward E except in the complex [(MeCN)(PMe(3))(4)W(SnMes)](+), where the M-E σ-bonding orbital is slightly polarized toward the W atom. The M-E π-bonding orbitals are highly polarized toward the metal atom. In all complexes, the π-bonding contribution to the total M≡EMes bond is greater than that of the σ-bonding contribution and increases upon going from M = Mo to W. The values of orbital interaction ΔE(orb) are significantly larger in all studied complexes I-VIII than the electrostatic interaction ΔE(elstat). The absolute values of the interaction energy, as well as the bond dissociation energy, decrease in the order Si > Ge > Sn > Pb, and the tungsten complexes have stronger bonding than the molybdenum complexes.     

A three-dimensional extended Sb network in the metallic antimonides (M',Ti)5Sb8 (M' = Zr, Hf, Nb, Mo)

(M',Ti)5Sb8 was prepared from the melt by arc-melting suitable mixtures of Ti, TiSb2, and M'Sb2, respectively. This phase exists at least with M' = Zr, Hf, Nb, and Mo. A significant phase range for Zr delta Ti5 - delta Sb8 was found to be within 1.10(8) < or = delta < or = 3.9(3). All (M',Ti)5Sb8 representatives investigated occur in the same, yet hitherto unknown structure type, as determined by single-crystal analyses. E.g., the lattice dimensions of Zr delta Ti5 - delta Sb8 range from a = 654.49(3) pm, c = 2662.4(2) pm for delta = 1.10(8) to a = 671.06(6), c = 2679.7(4) pm for delta = 3.9(3) (space group I4(1)22, No. 98, Z = 4). The three chemically inequivalent metal sites are statistically occupied by different mixtures of the M atoms M' and Ti, included in a three-dimensional network of Sb atoms on 6- to 8-fold Sb coordinated positions. Sb-Sb bonds of intermediate lengths occur in addition to the predominating heteronuclear M-Sb bonds. Physical property measurements of (Zr,Ti)5Sb8 reveal these phases being metallic exhibiting specific resistances of several m omega.cm and a small Seebeck coefficient at room temperature, in agreement with the results of the electronic structure calculations on the LMTO and extended Hückel levels. The calculations indicate a possible change to semiconducting properties by heavy doping.     

Predicting the relative stability of simple versus ansa-sandwich systems across groups: structure, bonding, and (in)stability in tris(sandwich)benzene complexes

We examine theoretically the bonding and thermodynamic stability of a proposed class of tris(sandwich)benzene complexes with the general formula C(6)(RMR')(3). In these systems, a single central (benzene) ring is flanked by three distorted 18-electron sandwich fragments with M = Groups 6, 7, or 8 metals, and R and R' = Ph or cyclopentadienyl (Cp) substituents. Remarkably, the computed free energy changes for the binding of the metal atoms to the organic fragments in 1) the ansa-(C(6)(RMR')(3)) complexes and 2) the simple (RMR') sandwich complexes--for all the Groups 6, 7, and 8 metals--conform to the linear relationship: [ΔG(bind)(C(6)(RMR')(3))]/3 = β(1)(ΔG)[ΔG(bind)(RMR')]+β(2)(ΔG) (R=0.989). The bonding and relative stabilities of these unusual tris(sandwich) and simple sandwich complexes are assessed at the B3PW91 level of theory employing small-core relativistic MDF pseudopotentials and the corresponding basis sets for all the metals. The possible existence of strain-induced bond localization (the so-called Mills-Nixon effect) in the C(6)(RMR')(3) complexes and the aromaticity at the central benzene ring in C(6)(RMR')(3) are investigated. Despite the strain on the central ring, no bond fixation is observed. The tris(sandwich) complexes of Groups 6, 7, and 8 are all thermodynamically stable, relative to the free M atoms and organic fragments, with increasing stability as M gets heavier (going down the groups). The equation above also enables us to predict, by extrapolation, the (in)stabilities of the C(6)(RMR')(3) complexes of several other transition metals and helps us to better understand thermodynamic aspects of the ansa effect. Similar functions likely apply for other ansa variants of sandwich complexes.     

Structures,bond energies,heats of formation,and quantitative bonding analysis of main-group metallocenes [E(Cp)2] (E = Be-Ba,Zn, Si-Pb) and [E(Cp)] (E = Li-Cs,B-Tl)

The geometries, metal-ligand bond dissociation energies, and heats of formation of twenty sandwich and half-sandwich complexes of the main-group elements of Groups 1, 2, 13, and 14, and Zn have been calculated with quantum chemical methods. The geometries of the [E(Cp)] and [E(Cp)2] complexes were optimized using density functional theory at the BP86 level with valence basis sets, which have DZP and TZP quality. Improved energy values have been obtained by using coupled-cluster theory at the CCSD(T) level. The nature of the metal-ligand bonding has been analyzed with an energy-partitioning method. The results give quantitative information about the strength of the covalent and electrostatic interactions between En+ and (Cp-)n (n = 1, 2). The contributions of the orbitals with different symmetry to the covalent bonding are also given.     

梯形结构二(对甲基苄基)锡氧(氯)簇合物的合成、结构及量子化学研究

二(对甲基苄基)二氯化锡和氢氧化钠溶液反应,合成了梯形结构二(对甲基苄基)锡氧(氯)簇合物,经X-射线衍射测定了其晶体结构。属三斜晶系,空间群为P1,晶体学参数a=0.979 52(16) nm,b=1.313 8(2) nm,c=1.419 5(2) nm,α=62.965(10)°,β=88.551(12)°,γ=73.709(11)°,V=1.550 5(5) nm³,Z=1,D_c=1.563 g·cm^-3,μ(Mo Kα)=17.38 cm^-1,F(000)=727,R=0.024 2,wR=0.057 9。簇合物为由Sn₂O₂构成的平面四元环形成的1个中心内环和2个由Sn₂OCl(O)构成的平面四元外环组成的梯形结构。锡原子均为五配位三角双锥构型。对其结构进行量子化学从头计算,探讨了配合物的稳定性、分子轨道能量以及一些前沿分子轨道的组成特征。