STRUCTURAL ALTERNATIVES IN R-2(CL)P-GACL3 SYSTEMS (R = ALKYL, PHENYL), INCLUDING EXAMPLES OF INTERMOLECULAR P-]P COORDINATION

Systematic NMR studies of (dialkyl/diaryl)chlorophosphine-gallium chlo ride reaction mixtures reveal three structural alternatives, which are related by equilibria in solution, and their relative stability is de pendent on the nature of the substituent (R = Me, Et, Pr-i, Bu-t, Ph) and the reaction stoichiometry. The coordination complex R-2(Cl)P-->Ga Cl3 is observed in all cases, and a derivative (R = Pr-i) has been cry stallographically characterized. Tetrachlorogallate salts of the dipho sphorus cations [R-2(Cl)P-PR2](+) are observed for smaller R substitue nts (R = Me, Et, Pr-i, Ph), consistent with a previous report. Solid-s tate P-31 CPMAS NMR spectra distinguish the methyl derivative from the novel salt [Me-2(Cl)P-P(Me-2)GaCl3][GaCl4], containing a phosphine-ph osphenium-gallium chloride cation, which has been crystallographically characterized. Factors governing the relative stabilities of the stru ctural alternatives are discussed, and comparisons are made between th e isomeric forms for R-2(Cl)P:GaCl3.