METHYLZINC TETRAHYDROBORATE - INVESTIGATION OF THE VAPOR-PHASE BY SPECTROSCOPIC AND QUANTUM-CHEMICAL TECHNIQUES

Methylzinc tetrahydroborate vapour, as shown by its mass and infrared spectra, consists of an equilibrium mixture of monomeric and dimeric s pecies, the proportion of the dimer increases Bs the temperature is ra ised from 243 to 268 K (at pressures < 10(-1) Torr). Consistent with t he results of Density Functional Theory (DFT) calculations, the patter n of infrared bands of the matrix-isolated monomer points to a bidenta te BH4 group and a tri-coordinate zinc centre. Close agreement between computed and experimentally determined infrared frequencies acids cre dence to the calculated structural parameters. The nature of the dimer is less certain. The spectroscopic results are consistent with a cycl ic structure of the type MeZn(mu(2),eta(2)-BH4)(2)ZnMe; the minimum en ergy DFT structure features C-2v symmetry and a puckered eight-membere d Zn(mu-H)B(H)(2)(mu-H)Zn(mu-H)B(H)(2)(mu-H) ring. (C) 1998 Elsevier S cience B.V.