New complexes of the formula (Cp'Mo^-S^SsCHR, where R = C02Me (3) and C02Na (4) (Cp' = C5H5, CH3C5H4), have been synthesized and characterized spectroscopically. Their reactions have been compared to those of the parent compound, where R =(1). The synthesis of 3 involved the alkylation of (MeCpMo)2U-S2) (µ-Sh with BrCH2C02Me to form [(MeCpMo)2-(µ-82)(µ-S)(g-SCH2C02Me)]Br (2(Br)). Complex 2 crystallized in space group P2Jc with a = 10.379(2) A, b = 20.820(6) A, c = 9.597(2) A, ß = 102.56°, V = 2024.3(8) A3, and Z = 4. An X-ray diffraction study of 2 confirmed that a µ-sulfido ligand was the site of alkylation and the µ-2 ligand remained intact. Complex 2 was deprotonated on an alumina column to form 3. The water-soluble complex 4 was synthesized by the reaction of [ , (µ-8)(µ-8 )]2 with Br2-CHC02Na in the presence of base. The reactivities of 3 and 4 are similar to that of 1 in most cases. Unlike 1, complex 3 reacts with triflic acid to cleave a C-S bond of the dithiolate ligand and form the triflate salt of 2. Complex 4 differs from 1 in that it undergoes an observable reaction with hydrogen in neutral or basic aqueous solution. Spectroscopic data for the hydrogen addition product are consistent with the formulation ( )2(µ-8)2(µ-8 )(µ-80 2 2 8) ( 7).The catalytic activity of 4 and 7 for D2-H20 exchange and for the hydrogenation of C=N and N=N bonds in two-phase aqueous/organic solvent systems has been studied.(µ-8))282 with new electron-withdrawing substituents on the methanedithiolate ligands and the characterization of their reaction chemistry. A second paper in this series describes the syntheses of water-soluble molybdenum sulfide complexes with electron-withdrawing substituents on the cyclopentadienyl ligands.15

Solid state coordination geometry (distances, angles) in the titled complexes has been statistically characterized. Data have been extracted from the Cambridge Structural Database (CSD) and from three new crystal structures reported in this paper. The conformation adopted by the 8-membered ring defined by nickel atoms and bridging ligands has been characterized by a probabilistic method in complexes [{NiL(µ-O 2 P(OR) 2 )} 2 ] (L ϭ hydrotris(3,5-1869 dimethylpyrazolyl)borate, R ϭ Me, Ph). The observed and ideal conformations have been studied by Molecular Mechanics. The strain energy calculated for the observed conformations is clearly lower, justifying their appearance in the solid state.