Carlos A. Murillo

Multiple bonds between metal atoms

Introduction and Survey.- Complexes of the Group 5 Elements.- Chromium Compounds.- Molybdenum Compounds.- Tungsten Compounds.- X3M=MX3 Compounds of Molybdenum and Tungsten.- Technetium Compounds.- Rhenium Compounds.- Ruthenium Compounds.- Osmium Compounds.- Iron, Cobalt and Iridium Compounds.- Rhodium Compounds.- Chiral Dirhodium (II) Catalysts and Their Applications.- Nickel, Palladium and Platinum Compounds.- Extended Metal Atom Chains.- Physical, Spectroscopic and Theoretical Results.

Two chromium(II) complexes with amidato-like ligands: a compound with the longest CrCr bond and a mononuclear compound with D2d symmetry

Abstract Reactions of chromium(II) with ligands that possess an amidato portion have been investigated, and products of two reactions been structurally characterized by X-ray crystallography. They show very different chemical behavior. The 2.550(4) A chromium-chromium distance in the dinuclear saccharinate, Cr2(C7H4NO3S)4·2THF (1), is the longest found so far in any chromium(II) dimer. Compound 1 also has the shortest chromium-axial ligand distance, CrLax. The reaction of Cr2OAc4·2H2O with lithium diethylbarbiturate yielded the mononuclear complex Li2Cr(C8H11N2O3)4·2C2H5OH (2), in which the ligand binds to the metal center in a monodentate fashion and there are only CrN bonds, which might be taken as an extreme manifestation of a Jahn-Teller Effect. The anion is further distorted from planarity and the coordination about the chromium atom has S4 symmetry. The crystallographic data for 1 are: space group C2/c, a=22.467(5), b=21.458(5), c=11.640(7) A, β=112.85(2)°, V=5171(3) A3, Z=4; and those for 2 are: space group Fdd2, a=27.036(9),b=17.154(4),c=20.777(9) A, V=9636(10) A3, Z=8.

Detailed structure of bis(.mu.-trimethylsilylmethylidyne)-tetrakis(trimethylsilylmethyl)ditungsten(W-W)

Abstract : The crystal and molecular structures of a compound of composition W2(CSiMe3)2 (CH2SiMe3)4 have been determined. The compound consists of dinuclear molecules which contain bridging alkylidyne groups, CSiMe3, which, along with the tungsten atoms form planar, rhombic rings, W-C-W-C. Two alkyl groups, CH2SiMe3, are attached to each metal atom to form distorted tetrahedra about the metal atoms. There are two crystallographically independent molecules, each residing on a crystallographic inversion center. The two crystallographically independent W-W distances, 2.521(2)A, and 2.549(2)A, are consistent with the presence of W-W single bonds.

Trinuclear complexes of four-coordinate iron and cobalt:: Some reflections on the importance of the reaction conditions for the formation of metal–metal bonds

Abstract The mononuclear, tetrahedral iron and cobalt complexes, FeCl2(Hhpp)2, I, and CoCl2(Hhpp)2, II, are readily formed by the reaction of the metal (II) chloride with Hhpp. Compound II crystallized as blue blocks in the space group Fdd2. The reaction of I with LiMe yielded the trinuclear complex Fe3Cl2(hpp)4, III, which crystallized as colorless blocks in the space group P21/n. A cobalt complex Co3Cl2(hpp)4, IV, analogous to III, was synthesized by the reaction of CoCl2 with Lihpp. Compound IV crystallized as blue blocks in the space group P21. Both III and IV have three four-coordinate metal centers and contain no metal–metal bonds, two metal atoms are each bound to one chlorine and three nitrogen atoms while the third one is bound to four nitrogen atoms.

A completely suppressed jahn-teller effect in the structure of hexaaquachromium(II) hexafluorosilicate

The structure of [Cr(H 2 O) 6 ]SiF 6 , a chromium(II) compound with homoleptic coordination, is reported. Hexaaquachromium(II) hexafluorosilicate crystallizes in space group R 3¯ with a =9.406(3) A, c =9.762(5) A, V =748.0(7) A 3 , and Z =3. The [Cr(H 2 O) 6 ] 2− cation has 3¯ symmetry and is essentially a regular octahedron, therefore showing no Jahn-Teller distortion. The relationship of the [Cr(H 2 O) 6 ] 2+ ion in this compound to other [ M (H 2 O) 6 ] 2+ ions ( M =Cr, V, Mn) is briefly discussed.

The molybdenum-to-molybdenum triple bond. 5. Preparation and structure of dimethyltetrakis(dimethylamido)dimolybdenum

Abstract : The existence of an extensive chemistry centering around the triplybonded Mo-Mo and W-W units is now well established and has recently been reviewed. A firm structural base for interpreting this chemistry has been provided by more than a score of x-ray crystallographic structure determinations. Among these, however, there have been only a few pairs of molybdenum and tungsten compounds with the same or very similar sets of ligands. The comparisons afforded by such pairs are valuable in developing the comparative chemistry of the M-M multiple bonds in the 2nd and 3rd transition series. (Author)

Preparation of vanadium(II) compounds. Structures of a carboxylato and a 3-pyridinesulphonate compound

Abstract Reactions of aqueous vanadium(II) sulphate with pyridine-2-carboxylate (and other carboxylic acids) and 3-pyridinesulphonate (pySO3) salts have been investigated, as well as the reaction of the products with pyridine. Two of the products have been structurally characterized by X-ray crystallography. An aquo carboxylato compound, [V(Pic)2(H2O)2]·2H2O (I) (Pic = anion of picolinic acid), crystallizes in the monoclinic space group P21/n with a = 9.930(2), b = 5.169(1), c = 14.543(2) A, β = 90.35(2)°, V = 746.1(2) A3 and Z = 2. Extensive hydrogen bonding in the structure provides sufficient protection to the metal centre to make the crystals relatively stable in air. The pyridine adduct V(pySO3)2(py)4 (II) possesses a molecular structure and crystallizes in the monoclinic space group C2/c with a = 17.033(4), b = 11.218(4), c = 17.396(4) A, β = 110.05(2)°, V = 3122(2) A3 and Z = 4. Both compounds exemplify the facile formation of bonds between vanadium(II) and nitrogen-containing ligands.

A double-bonded niobium(III) compound with a formamidinate core: Nb2(μ-SMe)2(μ-DTolF)2 (η2-DTolF)2.2 toluene, DToIF= di-p-tolylformamidinate

The reaction of NaEt3BH with Nb2(μ-SMe2)3Cl6 results in the transfer of a hydride ion to dimethylthioether with concomitant production of methane. Further reaction with potassium di-p-tolylformamidinate, KDTolF, yields Nb2(μ-SMe)2(μ-DTolF)2η2-DTolF:)2.2 toluene, 1. In the latter, two thiomethoxide ions and two DTolF groups bridge the trivalent niobium atoms. Each of the other two DTolF groups chelate a metal atom to give the molecule an edge-sharing bioctahedral structure, The niobium-niobium distance of 2.655(2) A is consistent with the presence of a double bond between the metal atoms.