Halogenation of Lewis acid/base stabilised phosphanylboranes

Abstract

The reaction pattern of the Lewis-acid/base stabilised phosphanylborane [(CO)5W(H2PBH2 · NMe3)] (1) with elemental halogens is comprehensively studied. The reaction with iodine and bromine leads to a selective halogenation at the tungstencarbonyl moiety under formation of [WX2(CO)4(H2PBH2 · NMe3)] (X = I (2), Br (3)). Whereas 2 is a stable product the brominated compound 3 dimerises easily to [WBr2(CO)3(H2PBH2 · NMe3)]2 (4) under lost of CO. The CO elimination reaction of 3 is extensively studied. If 3 is reacted with [Et4N][Br] the ionic compound [Et4N][WBr3(CO)3(H2PBH2 · NMe3)] (5) is formed. Otherwise, if 3 is combined with the donor ligand [H2PBH2 · NMe3], the complex [WBr2(CO)3(H2PBH2 · NMe3)2] (6) is obtained. Compounds 2–6 are comprehensively characterised by X-ray diffraction analysis, NMR, and IR spectroscopy.