Three-coordinate Structure Research Articles

Signatures of Size-Dependent Structural Patterns in Hydrated Copper(I) Clusters, Cu+(H2O)n=1-10.

The isomers of a hydrated Cu(I) ion with n=1-10 water molecules were investigated by using ab initio quantum chemistry and an automated isomer-search algorithm. The electronic structure and vibrational spectra of the hundreds of resulting isomers were used to analyze the source of the observed bonding patterns. A structural evolution from dominantly two-coordinate structures (n = 1-4) toward a mixture of two- and three-coordinate structures was observed at n = 5-6, where the stability provided by expanded hydrogen-bonding was competitive with the dominantly electrostatic interaction between the water ligand and remaining binding sites of the metal ion. Further hydration (n = 7-10) led to a mixture of three- and four-coordinate structures. The metal ion was found, through spectroscopic signatures, to appreciably perturb the O-H bonds of even third-shell water molecules, which highlighted the ability of this nominally simple ion to partially activate the surrounding water network.

Preparation of Tris(8-Hydroxyquinoline-5-Sulfonic Acid) Iron(III) Complex and Photocatalytic Property of Surface Modified TiO<sub>2</sub>

Tris(8-hydroxyquinoline-5-sulfonic acid) iron(III) complex (Fe(HQS)3) was prepared and characterized by elemental analysis, infrared, nuclear magnetic resonance and Raman spectrum. The results indicated that the Fe atom was located at the center of the Fe(HQS)3complex and the sulfonic groups did not present in the quinoline three-coordinate structure. The TGA analysis result showed that the three ligands were thermally stable within wide temperature range (364 °C, 512 °C, 628 °C,). According to XRD and UV-vis data, the nano-TiO2prepared by hydrothermal method was mainly in the form of anatase and brookite, and the Fe(HQS)3complex had single crystal structure. Neither Fe(HQS)3nor nano-TiO2has observable photocatalytic activity according to the result of our methyl orange degrading experiment. The Fe(HQS)3-TiO2complex, however, demonstrated strong spectral response and photocatalytic activity under visible light.

Influence of the Jahn–Teller effect on the g-tensor of the spin-orbit quartet in three-coordinate D3h structures

Theoretical calculations of g-tensor components for the spin–orbit quartet, which arises as the ground state in three-coordinate d9 complexes and low-spin d7 complexes of D3h symmetry, have been made on the assumption that the spin–orbit interaction is commensurable with the electron-vibrational interaction. The calculations were carried out within the framework of crystal field theory using representations of the hole formalism. The analytical expressions for g-tensor components were obtained limited to first-order terms. It was shown that the account of the electron–vibrational interaction in the excited quartet only provides three-axial anisotropy for the g-tensor. It was shown that the g-tensor rotates in the plane of the three-coordinate structure with consensual motion of the atoms. The resulting expressions for the g-factor components are in good agreement with experimental data. Being universal for a wide range of contributions of the vibronic and spin–orbit interactions, these expressions essentially fill the gap in studying structures of coordination compounds.

Synthesis, Molecular Structure, and EPR Analysis of the Three-Coordinate Ni(I) Complex [Ni(PPh3)3][BF4

The compound [Ni(PPh(3))(3)][BF(4)] x BF(3) x OEt(2) was isolated in crystalline form from the olefin oligomerization catalyst system Ni(PPh(3))(4)/BF(3) x OEt(2) and structurally characterized by X-ray diffraction. The influence of vibronic coupling on the EPR parameters of three-coordinate metal complexes with a 3d(9) electronic configuration was investigated within the framework of ligand field theory. Analytical expressions for g-tensor components and isotropic hyperfine coupling constants with ligand nuclei were obtained using first-order perturbation theory. It has been shown that the account of the vibronic interaction in the excited state predicts the existence of three-axial anisotropy of the g-tensor even at the level of first-order perturbation theory; two axes of the g-tensor located in a plane of three-coordinate structure can rotate about the main z axis when a compound is distorted by motion of ligands. It has been shown that in three points of the potential energy surface minimum, for which linear and quadric constants of the vibronic interactions have an identical signs, the HFS isotropic constant from one ligand is larger than HFS constants from the other two; for different vibronic constant signs the ratio between HFS constants varies on opposite. This theoretical researches are in the quality consent with experimental data for a three-coordinate Ni(I) and Cu(II) flat complexes.

A molecular picture of metal ion solvation: Infrared spectroscopy of Cu +(NH 3) n and Ag +(NH 3) n in the gas phase

Infrared spectroscopy is applied to mass-selected Cu +(NH 3) n and Ag +(NH 3) n in the gas phase for investigating coordination chemistry of ammonia solvated noble-metal ions. The Cu +(NH 3) 3 ion prefers a three-coordinated structure but two-coordinated isomers are of growing importance until becoming predominant at n = 8 and 9. The first shell of the Ag + ion is filled with four NH 3 molecules and the resulting tetrahedral Ag +(NH 3) 4 complex is solvated by subsequent NH 3 molecules through hydrogen bonding. A coordination number of 2 for Cu + can be ascribed to extensive 4s-3d hybridization in Cu +, which causes the twofold linear coordination. A larger coordination number of 4 for Ag + can be attributed to its larger ionic size and more importantly to inefficient 5s-4d hybridization in Ag +.

NOVEL EMBRACE OF PROTEIN AND METAL

A COPPER-TRAFFICKING PROTEIN has been found to have a unique type of metal-binding mechanism that may ease copper release. A team led by chemistry professor Thomas V. O’Halloran of Northwestern University reports that the bacterial copper-trafficking protein CusF binds copper via a strong cation-ð interaction between Cu(I) and a key tryptophan ( Nat. Chem. Bio. , DOI: 10.1038/ nchembio. 2007.57). Proteins usually bind metals through covalent interactions. CusF binds Cu(I) in a three-coordinate structure with two methionines and a histidine. Copper also interacts with the indole ring of a nearby tryptophan that stacks on top of it. The team used resonance Raman and Xray spectroscopy to confirm that the Cu-tryptophan interaction is an electrostatic cation-ð type. The Ag(I)- bound form of the binding site’s structure, though not this interaction, was independently reported last year by a team led by biologist Megan M. McEvoy of the University of Arizona ( Protein Sci. 2007 , 16 , 2287). When the researchers ...

Mononuclear and Binuclear Copper(I) Complexes Ligated by Bis(3,5-diisopropyl-1-pyrazolyl)methane: Insight into the Fundamental Coordination Chemistry of Three-Coordinate Copper(I) Complexes with a Neutral Coligand

By using the neutral bidentate nitrogen-containing ligand, bis(3,5-diisopropyl-1-pyrazolyl)methane (L1' '), the copper(I) complexes [Cu(L1' ')2](CuCl2) (1CuCl2), [Cu(L1' ')2](ClO4) (1ClO4), [Cu(L1' ')]2(ClO4)2 (2ClO4), [Cu(L1' ')]2(BF4)2 (2BF4), [Cu(L1' ')(NCMe)](PF6) (3PF6), [Cu(L1' ')(PPh3)](ClO4) (4ClO4), [Cu(L1' ')(PPh3)](PF6) (4PF6), [{Cu(L1' ')(CO)}2(mu-ClO4)](ClO4) (5ClO4), and the copper(II) complexes [{Cu(L1' ')}2(mu-OH)2(mu-ClO4)2] (6), and [Cu(L1' ')Cl2] (7) were systematically synthesized and fully characterized by X-ray crystallography and by IR and 1H NMR spectroscopy. In the case of copper(II), ESR spectroscopy was also applied. In comparison with the related neutral tridentate ligand L1', bis-chelated copper(I) complexes and binuclear linear-coordinated copper(I) complexes are easy to obtain with L1' ', like 1CuCl2, 1ClO4, 2ClO4, and 2BF4. Importantly, stronger and bulkier ligands such as acetonitrile (3PF6) and especially triphenylphosphine (4ClO4 and 4PF6) generate three-coordinate structures with a trigonal-planar geometry. Surprisingly, for the smaller ligand carbon monoxide, a mononuclear three-coordinate structure is very unstable, leading to the formation of a binuclear complex (5ClO4) with one bridging perchlorate anion, such that the copper(I) centers are four-coordinate. The same tendency is observed for the copper(II) bis(mu-hydroxo) compounds 6, which is additionally bridged by two perchlorate anions. Both copper(II) complexes 6 and 7 were obtained by molecular O2 oxidation of the corresponding copper(I) complexes. A comparison of the new copper(I) triphenylphosphine complexes 4ClO4 and 4PF6 with corresponding species obtained with the related tridentate ligands L1' and L1 (8ClO4 and 9, respectively) reveals surprisingly small differences in their spectroscopic properties. Density functional theory (DFT) calculations are used to shed light on the differences in bonding in these compounds and the spectral assignments. Finally, the reactivity of the different bis(pyrazolyl)methane complexes obtained here toward PPh3, CO, and O2 is discussed.

Syntheses and Structures of Bulky Monophosphine-Ligated Methylpalladium Complexes: Application to Homo- and Copolymerization of Norbornene and/or Methoxycarbonylnorbornene

Several new bulky monophosphine-ligated methylpalladium complexes were synthesized. Treatment of Pd(cod)MeCl (cod = cyclooctadiene) with bulky phosphines, PtBu3, or P(o-tol)3 afforded monophosphine-ligated methylpalladium chloride complexes 1a and 1b, which were isolated as crystalline solids in excellent yields. The structures depended on the shape of the ligand: a mononuclear three-coordinate structure for 1a and a chloride-bridged dinuclear structure for 1b. Absorption of chloride from methylpalladium chloride complexes 1a and 1b afforded the corresponding methylpalladium triflate complexes 2a and 2b, which were structurally characterized by NMR spectroscopy and X-ray crystallography. In the presence of NaB[3,5-(CF3)2C6H3]4, 1a and 1b catalyzed the addition homopolymerization of norbornene or methoxycarbonylnorbornene. The activity of the catalyst was found to be dependent on the structure of the complexes and the counteranions. The catalyst system 1a-NaB[3,5-(CF3)2C6H3]4 was also active for the copolymerization of norbornene and methoxycarbonylnorbornene to form a block-type copolymer. The obtained copolymer has the highest ester content probably due to the two vacant sites on the palladium. The molecular weight distribution reached the narrowest value, indicating the long lifetime of the catalyst.

Unambiguous evidence supporting the decomposition reaction of NO on two types of monovalent copper-ion in CuZSM-5 zeolite

By combining the methods of calorimetry and spectroscopy using CO as a probe molecule, we obtained the evidence supporting the decomposition reaction of NO on two types of monovalent copper-ion (Cu +) species in CuZSM-5 zeolite. These Cu + species showed the characteristic emission bands at 21,000 and 18,500 cm −1 and, respectively, gave the CO adsorption heats of 122 and 110 kJ mol −1. Taking account of our previous EXAFS data, it was found that the former species take the two-coordinated structure involving lattice oxygen atoms, while the latter ones the three-coordinated structure. In this paper, we also emphasized the validity of our original assignment of active sites on CuZSM-5 for N 2 adsorption at room temperature; three-coordinated Cu + species adsorb N 2 molecules.

Synthesis, structure, and reductive elimination chemistry of three-coordinate arylpalladium amido complexes.

Four three-coordinate arylpalladium amido complexes with a single hindered phosphine were isolated and structurally characterized. Each possessed a T-shaped geometry. Several of these complexes possessed true three-coordinate structures that lacked any additional coordination by ligand C-H bonds. All of the three-coordinate complexes underwent reductive elimination to form the corresponding triarylamine. A comparison of the rate of reaction of the three-coordinate compounds demonstrated that the rate of elimination from the pentaphenylferrocenyl di-tert-butylphosphine complex were the fastest. A comparison of the rates of reactions between three-coordinate and four-coordinate complexes showed that the rates were much faster from the three-coordinate complexes.

Anomalous valence changes and specific dinitrogen adsorption features of copper ion exchanged in ZSM-5 zeolite prepared from an aqueous solution of [Cu(NH3)2

Direct ion-exchange of monovalent copper ions into a ZSM-5-type zeolite was carried out using an aqueous solution of diammine–copper(I) ions, [Cu(NH3)2]+, to prepare a copper ion-exchanged ZSM-5 zeolite including only monovalent copper ions, and the effect of monovalent copper ions on the zeolite's adsorption properties for dinitrogen (N2) was examined. Strangely enough, the reoxidation of monovalent copper-ion exchanged in ZSM-5 took place in the evacuation process at around 473 K. The changes in valence and structure of the exchanged copper-ions during the evacuation process and the interaction with N2 molecules at room temperature have been investigated by using spectroscopic techniques such as X-ray absorption fine structure (XAFS), IR and photoemission spectroscopy, as well as by measurements of adsorption isotherms and adsorption heats. On the basis of X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses, it has become apparent that the Cu+ species exchanged in ZSM-5 zeolite is oxidized by water to form a divalent species having a CuO-like structure through heat-treatment in vacuo at 473 K. Further heat-treatment at temperatures above 673 K caused a reduction of the divalent species to a monovalent one that exhibits a pronounced adsorption feature for N2 even at room temperature. XANES and photoemission data clearly indicated that the Cu+ species in an 873 K-treated CuZSM-5 sample has a three-coordinate structure with lattice oxygen atoms and interacts strongly with an N2 molecule at room temperature. The strong interaction with N2 was also verified through the adsorption heat and IR data: an initial adsorption energy of 85 kJ mol−1 and an absorption band at 2295 cm−1. A prominent feature of this system is that some of the adsorbed species survives after evacuation at 300 K, indicative of a strong interaction between N2 and the three-coordinate copper ion.

Novel Ag(I) complexes with propeller-like structure of tripodal ligand: syntheses and structures of two- and three-coordinate silver (I) complexes

Two mononuclear Ag(I) complexes, [Ag(tbsb)](NO 3)·DMF ( 1) and [Ag(tbsb)](NO 3)·4.5H 2O ( 2) {tbsb=1,3,5-tris(2-benzimidazol)sulfanylmethyl)-2,4,6-trimethylbenzene}, have been synthesized by self-assembly reaction of AgNO 3 with tbsb and characterized structurally. The silver atoms of both the complexes are coordinated by the imine nitrogen atoms from a tripodal ligand (tbsb) to form two- and three-coordinate structures, respectively. Complex 1 presents the first example of silver (I) compound of the tripodal ligand possessing propeller-like structure.

Synthesis and crystal structure of a three-coordinate bismuth alkoxide with bismuth-β-phenyl secondary interactions, Bi(OCPh 3) 3

Bi(OCPh 3) 3 has been prepared and isolated and its structure established by X-ray crystallography. Bi(OCPh 3) 3 has been found to have a three-coordinate structure, unlike its silyl analogue, due to π interactions between the Lewis acidic metal and one β-phenyl ring of each alkoxide ligand.

Interaction and coordination geometries for Ag(I) in the two metal sites of hemocyanin

111Ag(I) perturbed angular correlations of gamma-rays (PAC) has been used to investigate the binuclear metal site of 111Ag(I)-substituted Carcinus aestuarii deoxyhemocyanin. The studies have shown that apo-hemocyanin is able to bind 2 mol of Ag(I) per mol of protein and that the binding is specific for the metal ion sites. The PAC spectra show pronounced changes when the stoichiometry of Ag(I) to protein is increased from 0.1 to 2.0. These changes have been interpreted as evidence of interactions between the two sites in terms of a structural destabilization of the first occupied site caused by the occupation of the second site. The experimental data for the Ag(I)-substituted metal sites do not agree well with the three-coordinated structure found in the Cu(I) holo-protein. However, if a water molecule is included as a coordinating ligand in the Ag(I) metal site a successful interpretation of the experimental data can be obtained.

Synthesis and Structures of Cationic Aluminum and Gallium Amidinate Complexes

Aluminum and gallium amidinate complexes, {RC(NR‘)2}MMe2 (R, R‘ = alkyl; M = Al, Ga), react with the “cationic activators” [Ph3C][B(C6F5)4] and B(C6F5)3 to yield cationic Al and Ga alkyl species whose structures are strongly influenced by the steric properties of the amidinate ligand. The reaction of acetamidinate Al complexes {MeC(NR‘)2}AlMe2 (R‘ = iPr, 1a; R‘ = Cy, 3a) with 0.5 equiv of [Ph3C][B(C6F5)4] or B(C6F5)3 yields {MeC(NR‘)2}2Al2Me3+ (R‘ = iPr, 2a+; R‘ = Cy, 4a+) as the B(C6F5)4- or MeB(C6F5)3- salts. X-ray crystallographic analyses establish that 2a+ and 4a+ are double-amidinate-bridged dinuclear cations, in which the two metal centers are linked by μ-η1,η1 and μ-η1,η2 amidinate bridges. NMR studies show that 2a+ undergoes two dynamic processes in solution: (i) a μ-η1,η1/μ-η1,η2 amidinate exchange and (ii) Me exchange between the two metal centers. The reaction of {MeC(NiPr)2}GaMe2 (1b) with 0.5 equiv of B(C6F5)3 yields {MeC(NiPr)2}2Ga2Me3+ (2b+), whose structure and dynamic properties are similar to those of 2a+. The reaction of the bulkier tBu-substituted amidinate complexes {tBuC(NiPr)2}MMe2 (M = Al, 6a; M = Ga, 6b) with 0.5 equiv of [Ph3C][B(C6F5)4] yields {tBuC(NiPr)2}MMe2·{tBuC(NiPr)2}MMe+ (M = Al, 7a+; M = Ga, 7b+) as the B(C6F5)4- salts, the former of which is thermally unstable. An X-ray crystallographic analysis establishes that 7b+ is a single-amidinate-bridged dinuclear cation, in which the two metal centers are linked by a μ-η1,η2 amidinate bridge. NMR data establish that the structures of 7a+ and 7b+ are similar and both species are rigid in solution. 6a and 6b also react with B(C6F5)3 to yield [7a][MeB(C6F5)3] and [7b][MeB(C6F5)3], respectively, which decompose by C6F5- transfer to yield {tBuC(NiPr)2}M(Me)(C6F5) (M = Al, 9a; M = Ga, 9b) and boron species. The “super-bulky” amidinate complexes {tBuC(NtBu)2}MMe2 (M = Al, 12a; M = Ga, 12b) react with 1 equiv of [Ph3C][B(C6F5)4] to yield {tBuC(NtBu)2}MMe+ (M = Al, 13a+; M = Ga, 13b+) as the B(C6F5)4- salts. The salts [13a][B(C6F5)4] and [13b][B(C6F5)4] are thermally unstable and could not be isolated. However, the NMR data for 13a+ and 13b+ in C6D5Cl are consistent with base-free, three-coordinate structures or labile, four-coordinate solvated cations. These results provide a starting point for understanding the mechanism and reactivity trends in ethylene polymerization catalyzed by cationic Al amidinate species.

Structure and coordination of organometallic groups on a chemically modified SiO2 surface

The structural, electronic, and energy parameters of the metal-containing clusters (H3SiO)3Si−O−XMe n (X=H, B, Al, or Zn;n=0, 1, or 2), which model organometallic groups on a SiO2 surface modified with B-, Al-, and Zn-containing alkyls, have been studied by quantum-chemical methods. Full geometry optimization for these clusters was carried out by the SCF MO LCAO method taking into account the electron correlation within the frameworks of the MP2 and B3LYP schemes using the 6-31G(d) (6-311G(d) for Zn) basis set. The effect of the crystal environment was taken into account in calculations of siliconoxygen clusters containing 10 and 30 silicon atoms using theab initio SCF/6-31G(d) and semiempirical MNDO-PM3 methods. Various modes of coordination and interactions of organometallic groups with oxygen atoms of surface groups were studied. For the organoaluminum group on the surface, two stable conformations were found, namely, the three-coordinate structure with the chain −O−AlMe2 ligand and the four-coordinate (quasicyclic) structure with the Al atom that forms two nonequivalent bonds with the O atoms at the same Si atom. The four-coordinate structure is energetically more favorable. No stable structures were found for the organoboron and organozinc fragments.

Coordination geometries for monovalent and divalent metal ions in [His121]azurin--studies using perturbed angular correlations of gamma-rays from 111Ag and 111mCd.

The structural details of the metal site in the [His121]azurin mutant from Alcaligenes denitrificans where the axial methionine has been replaced by a histidine have been studied after substitution with the divalent cadmium ion and the monovalent silver ion. The studies have been carried out in solution using the technique of perturbed angular correlations of gamma-rays (PAC) of the two isotopes, 111Ag and 111mCd. In the pH range 6-9, the PAC spectra for cadmium-substituted [His121]azurin reveals a pH-independent equilibrium between two different metal-coordination geometries. Interpretation of the PAC data shows agreement between the dominating coordination geometry and that derived from X-ray diffraction on the Cu(II)[His121] azurin at high pH (Messerschmidt, A., unpublished results). Thus, it appears likely that cadmium for this geometry is four coordinated to the ligands His46, His117, Cys112, and His121. The other geometry is best interpreted as a substitution of His121 by a solvent water ligand. These interpretations stem from predictions of the experimentally determined nuclear quadrupole interactions (NQI) via the simple angular overlap model (AOM). At low pH (3.8), the concentration of the former species is reduced to 50% of its high pH value suggesting a pK of about 4 for His121. Two different coordination geometries have also been observed for the Cu(II) protein and assigned a type 1.5 and a type 1 copper site [Kroes, S. J., Hoitink, C. W. G., Andrew, C. R., Ai, J., Sanders-Loehr, J., Messerschmidt, A., Hagen, W. R. & Canters, G. W. (1996a) Eur. J. Biochem. 240, 342-351]. For silver-substituted [His121]azurin, several notable changes occur relative to the cadmium-substituted protein. At least four different metal-coordination geometries exist for silver[His121]azurin in the pH range 4-8. Changes in the population of these coordination sites occurs between pH 4 and pH 5, and pH 5 and pH 6. Furthermore, in contrast to the cadmium-substituted protein, only a single coordination geometry is present above pH 6. The change in population occurring between pH 5 and pH 6 suggests ionization of a non-coordinating histidine, here proposed as His121. The change in population at low pH could then be due to protonation of an additional coordinating histidine such as His46 or His117. The single coordination geometry existing at pH values above 6 for the silver protein cannot within our model calculations be described with His121 coordinated. However, it can be described with a coordinated water molecule but in a different angular position than for His121 in the copper protein (Messerschmidt, A., unpublished results). The reduced tendency for silver to coordinate His121 is in agreement with the general trend of lower pK values for ligands coordinating to monovalent ions relative to divalent ions. In conclusion, this work demonstrates that mutation of Met121 to other amino acid residues opens the possibility of other coordination geometries than the rigid three-coordinated structure observed for wild-type azurin, especially the possibility of increasing the coordination number by either solvent water ligands or the substituting amino acid. Furthermore, it opens up the possibility for different coordination geometries for monovalent and divalent metal ions as observed here and previously for the [Leu121]azurin mutant [Bauer, R., Danielsen, E., Hemmingsen, L., Bjerrum, M. J., Hansson, O. & Singh, K. (1997) J. Am. Chem. Soc. 119, 157-163].

Interleukin-10 inhibits cytokine production by human gestational tissues: D.J. Dudley, S. Spencer, S. Edwin, M.D. Mitchell. Univ of Utah, Salt Lake City, UT 84132

The molecular orbitals of [diammine(dimethyl sulphide) (methylthiolate)copper (II)]+ and the three-coordinate complex ion without the dimethyl sulphide ligand [diammine (methylthiolato)copper(II)]+ were calculated by the ASED-MO method and are reported for the C1 point group. The molecular orbitals a37 and a38 of the four-coordinate complex ion and a17 and a18 of the three-coordinate complex ion are of sigma symmetry with respect to the CuS(methylthiolate) bond. Transitions from the molecular orbitals a37 or a17 at 16,577 and 16,504 cm−1, respectively, in the four- and three-coordinate structures to the singly occupied molecular orbital of that complex ion are calculated to have oscillator strengths of ca 0.044 and 0.048, respectively. The singly occupied molecular orbital has about 15% 3dxy(Cu) atomic orbital character and about 73% 3px(Smethylthiolate) atomic orbital character.

Ased-Mo calculations of unsymmetrical three-coordinate CuN 2S and four-coordinate CuN 2S 2 cores

The molecular orbitals of [diammine(dimethyl sulphide) (methylthiolate)copper (II)] + and the three-coordinate complex ion without the dimethyl sulphide ligand [diammine (methylthiolato)copper(II)] + were calculated by the ASED-MO method and are reported for the C 1 point group. The molecular orbitals a 37 and a 38 of the four-coordinate complex ion and a 17 and a 18 of the three-coordinate complex ion are of sigma symmetry with respect to the CuS(methylthiolate) bond. Transitions from the molecular orbitals a 37 or a 17 at 16,577 and 16,504 cm −1, respectively, in the four- and three-coordinate structures to the singly occupied molecular orbital of that complex ion are calculated to have oscillator strengths of ca 0.044 and 0.048, respectively. The singly occupied molecular orbital has about 15% 3 d xy(Cu) atomic orbital character and about 73% 3 p x(S methylthiolate) atomic orbital character.

Mercury(II) cyanide complexes with 4,4'-Bipyridine and 4,4'-(Propane-1,3-diyl)-bispyridine

1:1 Coordination complexes formed by mercury(11) cyanide with 4,4'-bipyridine and 4,4'-(propane-1,3-diyl)bispyridine have been prepared and characterized by molar conductance, molecular weight and infrared spectral measurements down to 200 cm-1 in the solid state. The 4,4'-bipyridine complex is shown to have a polymeric chain structure with a tetrahedral environment of two nitrogen atoms of bridging 4,4'-bipyridine and two carbon atoms of the terminally bonded cyano groups about the mercury atoms. The 4,4'-(propane-1,3-diyl)bispyridine complex is suggested to have a monomeric three-coordinate structure with only terminally bonded 4,4'-(propane-1,3-diyl)bispyridine and cyano groups.