Synthesis and reactions: (u-h)(u-ph(2)p(ch(2))(n)ph(2)p)mo(co)(8)(-) anions and axial replacement in na(2)pt(2)(u-po(4)h)(4)(h(2)o)(2) (binuclear molybdenum carbonyl anions bridged by hydride and bidentate phosphine ligands, tetrakis u-phosphato diplatin
Description
Synthesis and Reactions of Binuclear Molybdenum Carbonyl Anions Bridged Both by Hydride and Bidentate Phosphine Ligands, and Axial Ligand Replacement in Tetrakis u-Phosphato Diplatinum (III) Complexes Reactions of Et(,4)N('+) and Ph(,4)P('+) salts of u-HMo(,2)(CO)(,10)('-) with diphos ligands in refluxing THF yielded salts of u-H-Mo(,2)(CO)(,8)(Ph(,2)P- (CH(,2))(,n)PPh(,2))('-), n = 1, 2 and 4. X-ray crystal structure analysis of the n = 1 and n = 4 derivatives shown an overall bent, staggered config- uration in each case with a P-Mo-Mo-P torsion angle of 21(DEGREES) for n = 1 and 42(DEGREES) for n = 4 Chemical reactions of these supported bridging hydrides include protonation to remove H('-) and open up adjacent coordination sites, capturable by other ligands such as diars, diphos, acetonitrile, t-butyl-isocyanide, and carbon monoxide. The u-HMo(,2)(CO)(,8)Ph(,2)PCH(,2)PPh(,2)('-) anion catalytically decomposes formic acid, producing H(,2) and a spectroscopically observable u-formato binuclear complex anion which slowly extrudes CO(,2) and reforms the original u-H binuclear anion. Photolysis of u-HMo(,2)(CO)(,8)Ph(,2)PCH(,2)PPh(,2)('-) in the presence of Ph(,2)PCH(,2)PPh(,2) leads to the triply bridged binuclear anion, u-HMo(,2)- (CO)(,6)(Ph(,2)PCH(,23)Ph(,2))(,2)('-) The diplatinum(III) complex Pt(,2)(u-PO(,4)H)(,4)(H(,2)O)(,2) ('2-) reacts with halide ions X('-)(X = CL, Br) to give first Pt(,2)(u-PO(,4)H)(,4)X(H(,2)O) ('3-) and then Pt(,2)(u-PO(,4)H)(,4)X(,2) ('4-). The reaction establishes an equilibrium situation between the three complexes: (UNFORMATTED TABLE FOLLOWS) K(,1) Pt(,2)(u-PO(,4)H)(,4)(H(,2)O)(,2)('2-) + X('-) Pt(,2)(u-PO(,4)H)(,4)X(H(,2)O)('3-) k(,2) K(,3) Pt(,2)(u-PO(,4)H)(,4)X(H(,2)O)('3-) + X('-) Pt(,2)(u-PO(,4)H)(,4)X(,2)('4-) k(,4)(TABLE ENDS) Using pseudo first order conditions in halide ion at 25(DEGREES)C we have used a biphasic analysis to evaluate the rate constants. Under comparable conditions we measured the equilibrium constants Reactions of diplatinum(III) complex Pt(,2)(u-PO(,4)H)(,4)-(H(,2)O)(,2)('2-) with ligands L (L = I('-), N(,3)('-), NH(,3), pyridine, pyrazine, guanine, cytosine, S-methyl-L-cysteine, methionine, 2,2('-)-thiodiethanol, thiodipropionic acid, tetrahydrothiophene, thioacetamide, thiourea, mercaptopropi- onic acid, and homo L-cysteine) in aqueous solution yield Pt(,2)(u-PO(,4)H)(,4)L(,2) ('-n) where n = 2 for neutral ligands and n = 4 for anionic ligands. All of these compounds where characterized by UV-Vis, ('31)P NMR, IR or by X-ray crystallography