Reactivity of Boryl Complexes: Synthesis and Structure of New Neutral and Cationic Platinum Boryls and Borylenes

A reactivity study on a series of platinum boryl complexes was performed. The first stable base adducts of cationic haloboryl complexes of the form trans-[Pt{B(Br)-(NMe2)}(NCMe)(PCy3)(2)](+) were isolated and fully characterized. The dianion [B12Cl12](2-) was introduced as a weakly coordinating anion to complex chemistry forming a A(2)X salt. Through the reaction of trans-[Pt{B(Br)(tBu)}Br(PCy3)(2)] E ith BBr(2)tBu, the first highly soluble dinuclear platinum boryl complex, [Pt{B(Br)(tBu)}(mu-Br)(PCy3)](2), could be synthesized with concomitant buildup of the corresponding phosphine-borane adduct. In contrast to this observation, reaction of trans-[Pt{B(Br)(Mes)}Br(PCy3)(2)] with BBr3 leads to the formation of the cationic borylene complex trans[Pt(BMes)Br(PCy3)(2)](+) by abstraction of the bromo ligand bound mutually trans to the boryl ligand in the precursor and concomitant buildup of [BBr4](-). Reaction of [Pt(PCy3)(2)] with BCl3 and subsequent abstraction of the platinum-bound chloro ligand enabled the structural characterization of trans-[Pt(BCl2)(PCy3)(2)](+), which is isoelectronic with the metal-only Lewis pair trans-[Pt(BeCl2)(PCy3)(2)]. The bonding situation in both systems was investigated in detail using quantum chemical calculations. A T-shaped cationic complex, trans-[Pt{B(Br)(Fc)}(PiPr(3))(2)](+), and its precursor trans-[Pt{B(Br)(Fc)}Br(PiPr(3))(2)], both with reduced steric bulk at the phosphine ligands compared with their PCy3 derivatives, were fully characterized.