SYNTHESIS, CHARACTERIZATION AND REACTIONS OF COMPOUNDS, CONTAINING ANION [MO2BR8H]3-CENTER-DOT CRYSTAL-STRUCTURE OF (PIPH)3[MO2BR8H] (PIP =PIPERIDINE)

Preparation and characterization of (pyH)3[Mo2Br8H] (py = pyridine) (1 ), (pipH)3[Mo2Br8H] (pip=piperidine) (2), and (morphH)2(H7O3)[Mo2Br8H] (morph=morpholine (3) are described. (pipH)3[Mo2Br8H] (2) crystallize s in the monoclinic space group P2(1)/c with a = 15.378(4), b = 12.149 (7), c 16.870(5) angstrom, beta = 107.40(2)-degrees and Z = 4; 1855 da ta with I > 3sigma(I) were refined to R = 0.069, R(w) = 0.073. The str ucture of crystallographically asymmetric [Mo2Br8H]3- anion revealed a greater trans effect of the mu-H than that of the mu-Br, found also i n the case of other [Mo2X8H]3-, X = Cl, Br, I anions. Two reaction pat hways dominate the chemistry of compounds containing [Mo2Br8H]3-, as f ound in the studies of reactions with pyridine, HBr(aq) and CH3COOH(aq ) and they can be represented schematically as (a) Mo2(6+) + H- + H+ - -> Mo2(6+) + H-2, and (b) Mo2(6+) + H- --> Mo2(4+) + H+.