Structural Alternatives in R2(Cl)P:GaCl3 Systems (R = Alkyl, Phenyl), Including Examples of Intermolecular P → P Coordination

Systematic NMR studies of (dialkyl/diaryl)chlorophosphine−gallium chloride reaction mixtures reveal three structural alternatives, which are related by equilibria in solution, and their relative stability is dependent on the nature of the substituent (R = Me, Et, i Pr, t Bu, Ph) and the reaction stoichiometry. The coordination complex R 2 (Cl)P→GaCl 3 is observed in all cases, and a derivative (R = i Pr) has been crystallographically characterized. Tetrachlorogallate salts of the diphosphorus cations [R 2 (Cl)P−PR 2 ] + are observed for smaller R substituents (R = Me, Et, i Pr, Ph), consistent with a previous report. Solid-state 31 P CP-MAS NMR spectra distinguish the methyl derivative from the novel salt [Me 2 (Cl)P−P(Me 2 )−GaCl 3 ][GaCl 4 ], containing a phosphine−phosphenium−gallium chloride cation, which has been crystallographically characterized. Factors governing the relative stabilities of the structural alternatives are discussed, and comparisons are made between the isomeric forms for R 2 (Cl)P:GaCl 3 .