METHYLZINC TETRAHYDROBORATE - PHYSICAL AND CHEMICAL-PROPERTIES AND CRYSTAL-STRUCTURE AT LOW-TEMPERATURE

Methylzinc tetrahydroborate, MeZnBH(4), has been prepared by two route s and initially characterized by elemental analysis and its spectrosco pic properties. The structure has been determined by X-ray crystallogr aphy at 150 K [trigonal, space group R3c, a = b = 15.831(10), c = 8.36 (2) Angstrom, Z = 18, R = 0.072] to reveal helical polymers in which M eZn(+) and BH4- units alternate, with the latter functioning as a bide ntate ligand with respect to both of the adjacent metal atoms. Tt thus resembles the structure of solid Be(BH4)(2) with the difference that the zinc is five-co-ordinated, the Me and H ligands adopting a distort ed square-pyramidal geometry. Chemical properties of methylzinc tetrah ydroborate investigated include its thermal decomposition and its reac tions with ammonia, dimethyl sulfide, triphenylphosphine and CO; dispr oportionation into Me(2)Zn and Zn(BH4)(2) appears to be a common featu re of its chemistry.