[Co(C~5H~5)~2]~n.[M(dmit)~2](M=Ni,Pd;n=0,1,2)型配合物的合成及表征

二茂金属[M'(C~5H~5)~2]^1^+的盐与(NBu~4)~n[M(dmit)~2](M=Ni, Pd; N=1,2)反应, 当M'=Fe, Ni; n=1时, 分别得到了导电配合物[Ni(dmit)~2]和[Pd(dmit)~2]; 当M'=Co, n=1,2时, 分别得到的是电荷几乎不转移的4个盐[Co(C~5H~5)~2]~n[Ni(dmit)~2]和[Co(C~5H~5)~2]~n[Pd(dmit)~2]。用ESCA、Raman谱及循环伏安图讨论了上述化合物形成时的电荷转移量。尽管[M(dmit)~2]的室温电导率相当大, 但其电导率随温度的变化曲线表明它们属于半导体。EHCO能带计算给出[Ni(dmit)~2]的能隙0.112eV, 与实测的电导活化能相当接近。     

Electronic structure of square planar bis(benzene-1,2-dithiolato)metal complexes [M(L)(2)](z) (z = 2-, 1-, 0; M = Ni, Pd, Pt, Cu, Au): an experimental, density functional, and correlated ab initio study

The three diamagnetic square planar complexes of nickel(II), palladium(II), and platinum(II) containing two S,S-coordinated 3,5-di-tert-butylbenzene-1,2-dithiolate ligands, (L(Bu))(2-), namely [M(II)(L(Bu))(2)](2-), have been synthesized. The corresponding paramagnetic monoanions [M(II)(L(Bu))(L(Bu)(*))](-) (S = (1)/(2)) and the neutral diamagnetic species [M(II)(L(Bu)(*))(2)] (M = Ni, Pd, Pt) have also been generated in solution or in the solid state as [N(n-Bu)(4)][M(II)(L(Bu))(L(Bu)(*))] salts. The corresponding complex [Cu(III)(L(Bu))(2)](-) has also been investigated. The complexes have been studied by UV-vis, IR, and EPR spectroscopy and by X-ray crystallography; their electro- and magnetochemistry is reported. The electron-transfer series [M(L(Bu))(2)](2-,-,0) is shown to be ligand based involving formally one (L(Bu)(*))(-) pi radical in the monoanion or two in the neutral species [M(II)(L(Bu)(*))(2)] (M = Ni, Pd, Pt). Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas-Kroll-Hess (DKH2) and zeroth-order regular approximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronic spectra. For the three neutral species a detailed analysis of the orbital structures reveals that the species may best be described as containing two strongly antiferromagnetically interacting ligand radicals. Furthermore, multiconfigurational ab initio calculations using the spectroscopy oriented configuration interaction (SORCI) approach including the ZORA correction were carried out. The calculations predict the position of the intervalence charge-transfer band well. Chemical trends in the diradical characters deduced from the multiconfigurational singlet ground-state wave function along a series of metals and ligands were discussed.     

FT-IR spectroscopic investigation of some Hofmann type complexes: M(1-phenylpiperazine)2Ni(CN)4 (M=Ni, Co, Cd, Pd or Mn)

New Hofmann type complexes in the form of M(pp)(2)Ni(CN)(4) (where pp=1-phenylpiperazine and M=Ni, Co, Cd, Pd or Mn) have been prepared in powder form and their infrared spectra have been reported in the range of (4000-400) cm(-1). The thermal behaviours of these complexes have been investigated by differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA). Ni(pp)(2)Ni(CN)(4) complex has been examined via transmission electron microscope (TEM). The results suggest that these compounds are similar in structure to Hofmann type complexes and their structures consist of polymeric layers |M-Ni(CN)(4)|(infinity) with the pp molecule bounded to the metal atom (M).     

Metal-metal interactions in dinuclear d(8) metal cyanide complexes supported by phosphine ligands. Spectroscopic properties and ab initio calculations of [M(2)(mu-diphosphine)(2)(CN)(4)] and trans-[M(phosphine)(2)(CN)(2)] (M = Pt,Ni)

Structural, spectroscopic properties on the dinuclear [M(2)(dcpm)(2)(CN)(4)] (M = Pt, 1a; Ni, 2a, dcpm = bis(dicyclohexylphosphino)methane) and [M(2)(dmpm)(2)(CN)(4)] (M = Pt, 1b; Ni, 2b, dmpm = bis(dimethylphosphino)methane) and the mononuclear trans-[M(PCy(3))(2)(CN)(2)] (M = Pt, 3; Ni, 4, PCy(3) = tricyclohexylphosphine) and theoretical investigations on the corresponding model compounds are described. X-ray structural analyses reveal Pt.Pt and Ni.Ni distances of 3.0565(4)/3.189(1) A and 2.957(1)/3.209(8) A for 1a/1b and 2a/2b, respectively. The UV-vis absorption bands at 337 nm (epsilon 2.41 x 10(4) dm(3) mol(-)(1) cm(-)(1)) for 1a and 328 nm (epsilon 2.43 x 10(4) dm(3) mol(-)(1) cm(-)(1)) for 1b in CH(2)Cl(2) are assigned to (1)(5d(sigma) --> 6p(sigma)) electronic transitions originating from Pt(II)-Pt(II) interactions. Resonance Raman spectroscopy of 1a, in which all the Raman intensity appears in the Pt-Pt stretch fundamental (93 cm(-)(1)) and overtone bands, verifies this metal-metal interaction. Complexes 1a and 1b exhibit photoluminescence in the solid state and solution. For the dinuclear nickel(II) complexes 2a and 2b, neither spectroscopic data nor theoretical calculation suggests the presence of Ni(II)-Ni(II) interactions. The intense absorption bands at lambda > 320 nm in the UV-vis spectra of 2a and 2b are tentatively assigned to d --> d transitions.     

Synthesis, structure, and magnetism of heterometallic carboxylate complexes [MnIII2M(II)4O2(PhCOO)10(DMF)4], M = Mn(II), Co(II), Ni(II)

Three new homo- and heterometallic hexanuclear complexes [Mn(2)M(II)(4)O(2)(PhCOO)(10)(DMF)(4)] (with M = Mn (1), Co (2) or Ni (3) and DMF = dimethylformamide) have been synthesized by redox generation of benzoate ligands from benzaldehyde in a one-pot reaction. All of the compounds are isostructural and crystallize in the I-42d space group of the tetragonal system, data for 1: a = 27.2249(8) Angstroms, c = 25.5182(5) Angstroms, R1 = 0.0681. The crystal structure contains isolated molecules. Each molecule consists of 2 x Mn(III) surrounded by four M(II) ions to form two edge-sharing OMn(2)M(2) tetrahedra giving rise to the [Mn(2)M(4)O(2)] core. The coordination sphere of each metal is completed by the bridging benzoate ligands and DMF molecules. The magnetic susceptibilities of 1-3 have been measured in the 1.8 K < T < 300 K temperature range. The magnetic susceptibilities for 1 and 2 pass through a broad maximum at low temperature which is characteristic of the diamagnetic ground state, while for 3 no maximum is detected down to 1.8 K. The magnetic data have been interpreted quantitatively for 1 and 3 on the basis of spin exchange interactions between the metallic centers (spin Hamiltonian for a pair being H(AB) = -J(AB) S(A).S(B)). Single-crystal measurements on [Mn(6)O(2)(PhCOO)(10)(CH(3)CN)(4)] (4) show that significant magnetic anisotropy develops at low temperature.     

Magnetic semiconductor: structural,magnetic, and conducting properties of the salts of the 6-oxoverdazyl radical cation with M(dmit)(2) anions (M = Ni,Zn, Pd,and Pt,dmit = 1,3-dithiol-2-thione-4,5-dithiolate)

Five kinds of (1:1), (1:3), and (2:1) salts of 3-[4-(diethylmethylammonio)phenyl]-1,5-diphenyl-6-oxoverdazyl radical cation [V](+) with M(dmit)(2) anions (M = Ni, Zn, Pd, and Pt, dmit = 1,3-dithiol-2-thione-4,5-dithiolate) ([V](+)[Ni(dmit)(2)](-) (1), [V](+)[Ni(dmit)(2)](3)(-) (2), [V](+)(2)[Zn(dmit)(2)](2-) (3), [V](+)(2)[Pd(dmit)(2)](2-) (4), and [V](+)(2)[Pt(dmit)(2)](2-) (5)) and an iodide salt of [V](+) ([V](+)[I](-) (6)) have been prepared, and the magnetic susceptibilities (chi(M) values) have been measured between 1.8 and 300 K. The chi(M) of the (1:1) Ni salt (1) can be well reproduced by the sum of the contributions from (i) a Curie-Weiss system with a Curie constant (C) of 0.376 K emu/mol and a negative Weiss constant (theta) of -1.5 K and (ii) the one-dimensional Heisenberg antiferromagnetic alternating chain system with 2J(A-B)/k(B) = -274 K (alternation parameter alpha = J(A-C)/J(A-B) = 0.2). The chi(M) of the (1:3) Ni salt (2) can be well explained by the two-term contributions from (i) the Curie-Weiss system with C = 0.376 K emu/mol and theta = -5.0 K and (ii) the dimer system with 2J/k(B) = -258 K. The magnetic properties of 1 and 2 were discussed based on the results obtained by crystal structure analysis and ESR measurements of 1 and 2. The chi(M) values of the (2:1) Zn, Pd, Pt salts 3, 4, and 5 and [V](+)[I](-) salt 6 follow the Curie-Weiss law with C = 0.723, 0.713, 0.712, and 0.342 K emu/mol and theta = -2.8, -3.1, -2.6, and +0.02 K, respectively, indicating that only the spins of the verdazyl radical cation contribute to the magnetic property of these salts. The salts 1, 3, and 5 are insulators. On the other hand, the conductivity (sigma) of the Ni salt 2 and Pd salt 4 at 20 degrees C was sigma = 8.9 x 10(-2) and 1.3 x 10(-4) S cm(-)(1) with an activation energy E(A) = 0.11 and 0.40 eV, respectively. The salts 2 and 4 are new molecular magnetic semiconductors.     

Valence-Dependent Metal-Metal Bonding and Optical Spectra in Confacial Bioctahedral [Re(2)Cl(9)](z)()(-) (z = 1, 2, 3). Crystallographic and Computational Characterization of [Re(2)Cl(9)](-) and [Re(2)Cl(9)](2)(-)

The geometric structure of the confacial bioctahedral [Re(2)Cl(9)](z)()(-) anion has been determined by single-crystal X-ray diffraction in two distinct oxidation states, Re(IV)(2) and Re(III)Re(IV). [Bu(4)N][Re(2)Cl(9)] crystallizes in the monoclinic space group P2(1)/m [a/? = 10.6363(3), b/? = 11.420(1), c/? = 13.612(1), beta/deg = 111.18(1), Z = 2], while [Et(4)N](2)[Re(2)Cl(9)] crystallizes in the orthorhombic space group Pnma [a/? = 15.82(1), b/? = 8.55(2), c/? = 22.52(3), Z = 4]. The Re-Re separation contracts from 2.704(1) ? in [Bu(4)N][Re(2)Cl(9)] to 2.473(4) ? in [Et(4)N](2)[Re(2)Cl(9)] (or, equivalently, from 2.725 to 2.481 ? after standard corrections for thermal motions), while the formal metal-metal bond order falls from 3.0 to 2.5. SCF-Xalpha-SW molecular orbital calculations show that, despite the {d(3)d(3)} configuration, the single sigma bond in [Re(2)Cl(9)](-) dominates the observed structural properties. For [Re(2)Cl(9)](2)(-), the 0.23 ? contraction in Re-Re is attributed jointly to radial expansion of the Re 5d orbitals and to diminished metal-metal electrostatic repulsion, which act in concert to make both sigma and delta(pi) bonding more important in the reduced species. Computed transition energies and oscillator strengths for the two structurally defined anions permit rational analysis of their ultraviolet spectra, which involve both sigma --> sigma and halide-to-metal change-transfer absorptions. The intense sigma --> sigma band progresses from 31 000 cm(-)(1) in [Re(2)Cl(9)](-) to 36 400 cm(-)(1) in [Re(2)Cl(9)](2)(-), according to the present assignments. For electrogenerated, highly reactive [Re(2)Cl(9)](3)(-) (where conventional X-ray structural information is unlikely to become available), the dominant absorption band advances to 40 000 cm(-)(1), suggesting further strengthening of the metal-metal sigma bond in the Re(III)(2) species.     

Metal-metal interactions in heterobimetallic d8-d10 complexes. Structures and spectroscopic investigation of [M'M' '(mu-dcpm)2(CN)2]+ (M' = Pt,Pd; M' ' = Cu,Ag, Au) and related complexes by UV-vis absorption and resonance Raman spectroscopy and ab initio calculations

X-ray structural and spectroscopic properties of a series of heterodinuclear d(8)-d(10) metal complexes [M'M' '(mu-dcpm)(2)(CN)(2)](+) containing d(8) Pt(II), Pd(II), or Ni(II) and d(10) Au(I), Ag(I), or Cu(I) ions with a dcpm bridging ligand have been studied (dcpm = bis(dicyclohexylphosphino)methane; M' = Pt, M' ' = Au 4, Ag 5, Cu, 6; M' ' = Au, M' = Pd 7, Ni 8). X-ray crystal analyses showed that the metal...metal distances in these heteronuclear metal complexes are shorter than the sum of van der Waals radii of the M' and M' ' atoms. The UV-vis absorption spectra of 4-6 display red-shifted intense absorption bands from the absorption spectra of the mononuclear trans-[Pt(phosphine)(2)(CN)(2)] and [M' '(phosphine)(2)](+) counterparts, attributable to metal-metal interactions. The resonance Raman spectra confirmed assignments of (1)[nd(sigma)-->(n + 1)p(sigma)] electronic transitions to the absorption bands at 317 and 331 nm in 4 and 6, respectively. The results of theoretical calculations at the MP2 level reveal an attractive interaction energy curve for the skewed [trans-Pt(PH(3))(2)(CN)(2)-Au(PH(3))(2)(+)] dimer. The interaction energy of Pt(II)-Au(I) was calculated to be ca. 0.45 ev.     

Tuning the excited-state properties of [M(SnR3)2(CO)2(alpha-diimine)] (M = Ru, Os; R = Me, Ph)

The influences of R, the alpha-diimine, and the transition metal M on the excited-state properties of the complexes [M(SnR3)2(CO)2(alpha-diimine)] (M = Ru, Os; R = Ph, Me) have been investigated. Various synthetic routes were used to prepare the complexes, which all possess an intense sigma-bond-to-ligand charge-transfer transition in the visible region between a sigma(Sn-M-Sn) and a pi*(alpha-diimine) orbital. The resonance Raman spectra show that many bonds are only weakly affected by this transition. The room-temperature time-resolved absorption spectra of [M(SnR3)2(CO)2(dmb)] (M = Ru, Os; R = Me, Ph; dmb = 4,4'-dimethyl-2,2'-bipyridine) show the absorptions of the radical anion of dmb, in line with the SBLCT character of the lowest excited state. The excited-state lifetimes at room temperature vary between 0.5 and 3.6 microseconds and are mainly determined by the photolability of the complexes. All complexes are photostable in a glass at 80 K, under which conditions they emit with very long lifetimes. The extremely long emission lifetimes (e.g., tau = 1.1 ms for [Ru(SnPh3)2(CO)2(dmb)]) are about a thousand times longer than those of the 3MLCT states of the [Ru(Cl)(Me)(CO)2(alpha-diimine)] complexes. This is due to the weak distortion of the former complexes in their 3SBLCT states as seen from the very small Stokes shifts. Remarkably, replacement of Ru by Os hardly influences the absorption and emission energies of these complexes; yet the emission lifetime is shortened because of an increase of spin-orbit coupling. The quantum yield of emission at 80 K is 1-5% for these complexes, which is lower than might be expected on the basis of their slow nonradiative decay.     

Metal-metal bonding in molecular actinide compounds: electronic structure of [M2X8](2-) (M = U, Np, Pu; X = Cl, Br, I) complexes and comparison with d-block analogues

Density functional and multiconfigurational (ab initio) calculations have been performed on [M(2)X(8)](2-) (X = Cl, Br, I) complexes of 4d (Mo, Tc, Ru), 5d (W, Re, Os), and 5f (U, Np, Pu) metals in order to investigate general trends, similarities and differences in the electronic structure and metal-metal bonding between f-block and d-block elements. Multiple metal-metal bonds consisting of a combination of sigma and pi interactions have been found in all species investigated, with delta-like interactions also occurring in the complexes of Tc, Re, Np, Ru, Os, and Pu. The molecular orbital analysis indicates that these metal-metal interactions possess predominantly d(z2) (sigma), d(xz) and d(yz) (pi), or d(xy) and d(x2-y2) (delta) character in the d-block species, and f(z3) (sigma), f(z2x) and f(z2y) (pi), or f(xyz) and f(z) (delta) character in the actinide systems. In the latter, all three (sigma, pi, delta) types of interaction exhibit bonding character, irrespective of whether the molecular symmetry is D(4h) or D(4d). By contrast, although the nature and properties of the sigma and pi bonds are largely similar for the D(4h) and D(4d) forms of the d-block complexes, the two most relevant metal-metal delta-like orbitals occur as a bonding and antibonding combination in D(4h) symmetry but as a nonbonding level in D(4d) symmetry. Multiconfigurational calculations have been performed on a subset of the actinide complexes, and show that a single electronic configuration plays a dominant role and corresponds to the lowest-energy configuration obtained using density functional theory.     

Kinetic, DFT and TD-DFT studies on the mechanism of stabilization of pyramidal H3PO3 at the [Mo3M'S4(H2O)10]4+ clusters (M' = Pd, Ni)

The kinetics of reaction between the [Mo(3)M'S(4)(H(2)O)(10)](4+) clusters (M' = Pd, Ni) and H(3)PO(3) has been studied in 4.0 M Hpts/Lipts (pts(-) = p-toluenesulfonate). For both complexes there is an initial kinetic step with small absorbance changes that corresponds to substitution of the water coordinated to Pd by a molecule of tetrahedral H(3)PO(3). For the Pd complex, tautomerization of H(3)PO(3) occurs in a slower kinetic step with much larger absorbance changes; it leads to formation of [Mo(3)Pd(pyr-H(3)PO(3))S(4)(H(2)O)(9)](4+) in which H(3)PO(3) adopts a pyramidal structure, but the process is not as favored as for H(3)PO(2). The kinetics of this second step is independent of the concentration of H(3)PO(3) but dependent on the concentration of Hpts on the supporting electrolyte. For the Ni complex, the second step is severely hindered and its kinetics could not be studied. DFT calculations indicate that tautomerization of H(3)PO(3) is expected to be less favoured than that of H(3)PO(2), both processes being less favored at the Ni cluster than at its Pd analogue. With regard to the tautomerization mechanism, the calculations indicate that the mechanism previously proposed for H(3)PO(2) can be the same for H(3)PO(3), although the initial H-shift can also occur through a protonation-deprotonation sequence with participation of external protons instead of a second molecule of the phosphorus acid. TD-DFT studies have been also carried out to understand the similarity between the spectra of the starting complex and the reaction intermediate formed in the first kinetic step as well as the large spectral changes associated to the tautomerization process. Although it contains contributions from several transitions, the intense band observed for clusters containing coordinated pyr-H(3)PO(3) involves essentially ligand-to-metal charge-transfer (LMCT) transitions.     

Density functional theory study of the d(10) series (H3P)3M(eta 1-SO2) and (MenPh(3-n)P)3M(eta 1-SO2) (M = Ni, Pd, Pt; n = 0-3): SO2 pyramidality and M-S bond dissociation energies

Quantum mechanical density functional theory (DFT) and coupled DFT/molecular mechanics (QMMM) studies of the compounds (H(3)P)(3)M(eta(1)-SO(2)) and (Me(n)Ph(3-n)P)(3)M(eta(1)-SO(2)) (M = Ni, Pd, Pt; n = 0-3) model the experimental data well, particularly the planar/pyramidal geometries at sulfur. Bond dissociation energy (BDE) calculations confirm that Pd/Pt systems with pyramidal SO(2) ligands exhibit M-S BDEs smaller by 30-50% than Ni systems with planar SO(2). However, scans of the potential energy surfaces show that flexing the planar/pyramidal torsion angle within ranges of 20-30 degrees requires little energy. Bond energy decomposition calculations indicate that the electrostatic Delta E(elstat) term determines the BDE for Pd/Pt molecules where the sulfur is pyramidal, whereas all three terms matter when the sulfur is planar, as for Ni compounds. However, this accounts only for a fraction of the BDE differences; orbital energy matching accounts for the balance.     

Anion-cation charge-transfer properties and spectral studies of [M(phen)3][Cd4(SPh)10] (M = Ru, Fe, and Ni)

Three anion-cation compounds 1-3 with formula [M(phen)(3)][Cd(4)(SPh)(10)]·Sol (M = Ru(2+), Fe(2+), and Ni(2+), Sol = MeCN and H(2)O) have been synthesized and characterized by single-crystal analysis. Both the cations and anion are well-known ions, but the properties of the co-assembled compounds are interesting. Molecular structures and charge-transfer between the cations and anions in crystal and even in solution are discussed. These compounds are isomorphous and short inter-ion interactions are found in these crystals, such as π···π stacking and C-H···π contacts. Both spectroscopic and theoretical calculated results indicate that there is anion-cation charge-transfer (ACCT) between the Ru-phen complex dye and the Cd-SPh cluster, which plays an important role in their photophysical properties. The intensity of the fluorescent emission of the [Ru(phen)(3)](2+) is enhanced when the cation interacts with the [Cd(4)(SPh)(10)](2-) anion. The mechanism for the enhancement of photoluminescence has been proposed.     

一维〔M（tmp）〕_2ReO_4（M＝Ni、Cu、Pd）聚合物的能带结构

用紧束缚ＥＨＴ晶体轨道方法对一维〔Ｍ（ｔｍｐ）〕_２ＲｅＯ_４（Ｍ＝Ｎｉ、Ｃｕ、Ｐｄ）聚合物进行了能带计算，利用键向量近似方法对能带的结构及组成进行了讨论。结果表明，该类型聚合物具有不同的导电机理，并进一步研究了环平面间的成键性质及转角改变对聚合物导电性能的影响。     

Electronic Structure of [Pt(2)(&mgr;-O(2)CCH(3))(4)(H(2)O)(2)](2+) Using the Quasi-Relativistic Xalpha-SW Method: Analysis of Metal-Metal Bonding, Assignment of Electronic Spectra, and Comparison with Rh(2)(&mgr;-O(2)CCH(3))(4)(H(2)O)(2)

The electronic structure and metal-metal bonding in the classic d(7)d(7) tetra-bridged lantern dimer [Pt(2)(O(2)CCH(3))(4)(H(2)O)(2)](2+) has been investigated by performing quasi-relativistic Xalpha-SW molecular orbital calculations on the analogous formate-bridged complex. From the calculations, the highest occupied and lowest unoccupied metal-based levels are delta(Pt(2)) and sigma(Pt(2)), respectively, indicating a metal-metal single bond analogous to the isoelectronic Rh(II) complex. The energetic ordering of the main metal-metal bonding levels is, however, quite different from that found for the Rh(II) complex, and the upper metal-metal bonding and antibonding levels have significantly more ligand character. As found for the related complex [W(2)(O(2)CH)(4)], the inclusion of relativistic effects leads to a further strengthening of the metal-metal sigma bond as a result of the increased involvement of the higher-lying platinum 6s orbital. The low-temperature absorption spectrum of [Pt(2)(O(2)CCH(3))(4)(H(2)O)(2)](2+) is assigned on the basis of Xalpha-SW calculated transition energies and oscillator strengths. Unlike the analogous Rh(II) spectrum, the visible and near-UV absorption spectrum is dominated by charge transfer (CT) transitions. The weak, visible bands at 27 500 and 31 500 cm(-)(1) are assigned to Ow --> sigma(Pt(2)) and OAc --> sigma(Pt(2)) CT transitions, respectively, although the donor orbital in the latter transition has around 25% pi(Pt(2)) character. The intense near-UV band around 37 500 cm(-)(1) displays the typical lower energy shift as the axial substituents are changed from H(2)O to Cl and Br, indicative of significant charge transfer character. From the calculated oscillator strengths, a number of transitions, mostly OAc --> sigma(Pt-O) CT in nature, are predicted to contribute to this band, including the metal-based sigma(Pt(2)) --> sigma(Pt(2)) transition. The close similarity in the absorption spectra of the CH(3)COO(-), SO(4)(2)(-), and HPO(4)(2)(-) bridged Pt(III) complexes suggests that analogous spectral assignments should apply to [Pt(2)(SO(4))(4)(H(2)O)(2)](2)(-) and [Pt(2)(HPO(4))(4)(H(2)O)(2)](2)(-). Consequently, the anomalous MCD spectra reported recently for the intense near-UV band in the SO(4)(2)(-) and HPO(4)(2)(-) bridged Pt(III) complexes can be rationalized on the basis of contributions from either SO(4) --> sigma(Pt-O) or HPO(4) --> sigma(Pt-O) CT transitions. The electronic absorption spectrum of [Rh(2)(O(2)CCH(3))(4)(H(2)O)(2)] has been re-examined on the basis of Xalpha-SW calculated transition energies and oscillator strengths. The intense UV band at approximately 45 000 cm(-)(1) is predicted to arise from several excitations, both metal-centered and CT in origin. The lower energy shoulder at approximately 40 000 cm(-)(1) is largely attributed to the metal-based sigma(Rh(2)) --> sigma(Rh(2)) transition.     

Mechanistic diversity covering 15 orders of magnitude in rates: cyanide exchange on [M(CN)(4)](2-) (M = Ni, Pd, and Pt)

Kinetic studies of cyanide exchange on [M(CN)(4)](2-) square-planar complexes (M = Pt, Pd, and Ni) were performed as a function of pH by (13)C NMR. The [Pt(CN)(4)](2-) complex has a purely second-order rate law, with CN(-) as acting as the nucleophile, with the following kinetic parameters: (k(2)(Pt,CN))(298) = 11 +/- 1 s(-1) mol(-1) kg, DeltaH(2) (Pt,CN) = 25.1 +/- 1 kJ mol(-1), DeltaS(2) (Pt,CN) = -142 +/- 4 J mol(-1) K(-1), and DeltaV(2) (Pt,CN) = -27 +/- 2 cm(3) mol(-1). The Pd(II) metal center has the same behavior down to pH 6. The kinetic parameters are as follows: (k(2)(Pd,CN))(298) = 82 +/- 2 s(-1) mol(-1) kg, DeltaH(2) (Pd,CN) = 23.5 +/- 1 kJ mol(-1), DeltaS(2) (Pd,CN) = -129 +/- 5 J mol(-1) K(-1), and DeltaV(2) (Pd,CN) = -22 +/- 2 cm(3) mol(-1). At low pH, the tetracyanopalladate is protonated (pK(a)(Pd(4,H)) = 3.0 +/- 0.3) to form [Pd(CN)(3)HCN](-). The rate law of the cyanide exchange on the protonated complex is also purely second order, with (k(2)(PdH,CN))(298) = (4.5 +/- 1.3) x 10(3) s(-1) mol(-1) kg. [Ni(CN)(4)](2-) is involved in various equilibrium reactions, such as the formation of [Ni(CN)(5)](3-), [Ni(CN)(3)HCN](-), and [Ni(CN)(2)(HCN)(2)] complexes. Our (13)C NMR measurements have allowed us to determine that the rate constant leading to the formation of [Ni(CN)(5)](3-) is k(2)(Ni(4),CN) = (2.3 +/- 0.1) x 10(6) s(-1) mol(-1) kg when the following activation parameters are used: DeltaH(2)() (Ni,CN) = 21.6 +/- 1 kJ mol(-1), DeltaS(2) (Ni,CN) = -51 +/- 7 J mol(-1) K(-1), and DeltaV(2) (Ni,CN) = -19 +/- 2 cm(3) mol(-1). The rate constant of the back reaction is k(-2)(Ni(4),CN) = 14 x 10(6) s(-1). The rate law pertaining to [Ni(CN)(2)(HCN)(2)] was found to be second order at pH 3.8, and the value of the rate constant is (k(2)(Ni(4,2H),CN))(298) = (63 +/- 15) x10(6) s(-1) mol(-1) kg when DeltaH(2) (Ni(4,2H),CN) = 47.3 +/- 1 kJ mol(-1), DeltaS(2) (Ni(4,2H),CN) = 63 +/- 3 J mol(-1) K(-1), and DeltaV(2) (Ni(4,2H),CN) = - 6 +/- 1 cm(3) mol(-1). The cyanide-exchange rate constant on [M(CN)(4)](2-) for Pt, Pd, and Ni increases in a 1:7:200 000 ratio. This trend is modified at low pH, and the palladium becomes 400 times more reactive than the platinum because of the formation of [Pd(CN)(3)HCN](-). For all cyanide exchanges on tetracyano complexes (A mechanism) and on their protonated forms (I/I(a) mechanisms), we have always observed a pure second-order rate law: first order for the complex and first order for CN(-). The nucleophilic attack by HCN or solvation by H(2)O is at least nine or six orders of magnitude slower, respectively than is nucleophilic attack by CN(-) for Pt(II), Pd(II), and Ni(II), respectively.     

The clusters [Ma(ECp*)b] (M=Pd, Pt; E=Al, Ga, In): structures, fluxionality, and ligand exchange reactions

The synthesis and structural characterization of the novel homoleptic cluster complexes [Pd2(GaCp*)2(mu2-GaCp*)3] (1c), [Pd3(GaCp*)4(mu2-GaCp*)4] (2b) and [Pd3(AlCp*)2(mu2-AlCp*)2(mu3-AlCp*)2] (3) (Cp*=C5Me5) are presented. Furthermore, ligand exchange reactions of these cluster complexes are explored. In contrast to the electronically and sterically saturated complexes [M(ECp*)4] (M=Ni, Pd, Pt), the new unsaturated analogues [M(a)(ER)b] (E=Al, Ga, In) react with a variety of typical ligands (Cp*Al, CO, phosphines, isonitriles) to give new di- and tri-substituted compounds like [Pt2(GaCp*)2(mu2-AlCp*)3] (1d), [PdPt(GaCp*)(PPh3)(mu2-GaCp*)3] (4b), or [Pd3(PPh3)3(mu2-InCp*)(mu3-InCp*)2] (8). The trends of the reactivity of [M(a)(ER)b] as well as their fluxional behavior in solution has been elucidated by NMR spectroscopy, resulting in a mechanistic rationale for the ligand exchange reactions as well as the fluxional processes.     

M2(hpp)4Cl2 and M2(hpp)4, where M = Mo and W: preparations, structure and bonding, and comparisons with C2, C2H2, and C2Cl2 and the hypothetical molecules M2(hpp)4(H)2

The reaction between M(2)Cl(2)(NMe(2))(4), where M = Mo or W, and Hhpp (8 equiv) in a solid-state melt reaction at 150 degrees C yields the compounds M(2)(hpp)(4)Cl(2) 1a (M = Mo) and 1b (M = W), respectively, by the elimination of HNMe(2) [hpp is the anion derived from deprotonation of 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine, Hhpp]. Purification of 1a and 1b is achieved by sublimation of the excess Hhpp and subsequent recrystallization from either CH(2)Cl(2) or CHCl(3) (or CDCl(3)). By single-crystal X-ray crystallography, the structures of 1a and 1b are shown to contain a central paddlewheel-like M(2)(hpp)(4) core with Mo-Mo = 2.1708(8) A (from CH(2)Cl(2)), 2.1574(5) A (from CDCl(3)), W-W = 2.2328(2) A (from CDCl(3)), and M-N = 2.09(1) (av) A. The Cl ligands are axially ligated (linear Cl-M-M-Cl) with abnormally long M-Cl bond distances that, in turn, depend on the presence or absence of hydrogen bonding to chloroform. The quadruply bonded compounds M(2)(hpp)(4), 2a (M = Mo), and 2b (M = W), can be prepared from the reactions between 1,2-M(2)R(2)(NMe(2))(4) compounds, where R = (i)()Bu or p-tolyl, and Hhpp (4 equiv) in benzene by ligand replacement and reductive elimination. The compounds 2a and 2b are readily oxidized, and in chloroform they react to form 1a and 1b, respectively. The electronic structure and bonding in the compounds 1a, 1b, 2a, and 2b have been investigated using gradient corrected density functional theory employing Gaussian 98. The bonding in the M-M quadruply bonded compounds, 2a and 2b, reveals M-M delta(2) HOMOs and extensive mixing of M-M pi and nitrogen ligand lone-pair orbitals in a manner qualitatively similar to that of the M(2)(formamidinates)(4). The calculations indicate that in the chloride compounds, 1a and 1b, the HOMO is strongly M-Cl sigma antibonding and weakly M-M sigma bonding in character. Formally there is a M-M triple bond of configuration pi(4)sigma(2), and the LUMO is the M-M delta orbital. An interesting mixing of M-M and M-Cl pi interactions occurs, and an enlightening analogy emerges between these d(4)-d(4) and d(3)-d(3) dinuclear compounds and the bonding in C(2), C(2)H(2), and C(2)Cl(2), which is interrogated herein by simple theoretical calculations together with the potential bonding in axially ligated compounds where strongly covalent M-X bonds are present. The latter were represented by the model compounds M(2)(hpp)(4)(H)(2). On the basis of calculations, we estimate the reactions M(2)(hpp)(4) + X(2) to give M(2)(hpp)(4)X(2) to be enthalpically favorable for X = Cl but not for X = H. These results are discussed in terms of the recent work of Cotton and Murillo and our attempts to prepare parallel-linked oligomers of the type [[bridge]-[M(2)]-](n)().     

(d-p)π共轭作用对簇合物Mo_2S_4(dtp)_2和Mo_3S_4(dtp)_4·Py电子光谱的影响

比较了含有配位不饱和过渡金属原子簇合物Mo_2S_4(dtp)_2,(Ⅰ)和Mo_3S_4(dtp)_4·Py,(Ⅱ)的紫外—可见电子吸收光谱实验数据和半经验的量子化学方法INDO计算得到的电子跃迁能,讨论了(d-p)π型共轭作用对其电子吸收光谱位移的影响。结果表明,过渡金属簇合物中电子吸收光谱位移,与有机共轭体系有着类似的变化规律,即随着共轭π键数目增加,π-π电子跃迁的吸收光谱红移。     

Nickel complexes of o-amidochalcogenophenolate(2-)/o-iminochalcogenobenzosemiquinonate(1-) pi-radical: synthesis,structures, electron spin resonance,and x-ray absorption spectroscopic evidence

The preparation of complexes trans-[Ni(-SeC(6)H(4)-o-NH-)(2)](-) (1), cis-[Ni(-TeC(6)H(4)-o-NH-)(2)](-) (2), trans-[Ni(-SC(6)H(4)-o-NH-)(2)](-) (3), and [Ni(-SC(6)H(4)-o-S-)(2)](-) (4) by oxidative addition of 2-aminophenyl dichalcogenides to anionic [Ni(CO)(SePh)(3)](-) proves to be a successful approach in this direction. The cis arrangement of the two tellurium atoms in complex 2 is attributed to the intramolecular Te.Te contact interaction (Te.Te contact distance of 3.455 A). The UV-vis electronic spectra of complexes 1 and 2 exhibit an intense absorption at 936 and 942 nm, respectively, with extinction coefficient epsilon > 10000 L mol(-)(1) cm(-)(1). The observed small g anisotropy, the principal g values at g(1) = 2.036, g(2) = 2.062, and g(3) = 2.120 for 1 and g(1) = 2.021, g(2) = 2.119, and g(3) = 2.250 for 2, respectively, indicates the ligand radical character accompanied by the contribution of the singly occupied d orbital of Ni(III). The X-ray absorption spectra of all four complexes show L(III) peaks at approximately 854.5 and approximately 853.5 eV. This may indicate a variation of contribution of the Ni(II)-Ni(III) valence state. According to the DFT calculation, the unpaired electron of complex 1 and 2 is mainly distributed on the 3d(xz)() orbital of the nickel ion and on the 4p(z)() orbital of selenium (tellurium, 5p(z)()) as well as the 2p(z)() orbital of nitrogen of the ligand. On the basis of X-ray structural data, UV-vis absorption, electron spin resonance, magnetic properties, DFT computation, and X-ray absorption (K- and L-edge) spectroscopy, the monoanionic trans-[Ni(-SeC(6)H(4)-o-NH-)(2)](-) and cis-[Ni(-TeC(6)H(4)-o-NH-)(2)](-) complexes are appositely described as a resonance hybrid form of Ni(III)-bis(o-amidochalcogenophenolato(2-)) and Ni(II)-(o-amidochalcogenophenolato(2-))-(o-iminochalcogenobenzosemiquinonato(1-) pi-radical; i.e., complexes 1 and 2 contain delocalized oxidation levels of the nickel ion and ligands.