Syntheses and Structures of Mono- and Dinuclear Cationic Base-Stabilized Platinum Borylene Complexes

A series of fully characterized cationic, base-stabilized borylene complexes of the type trans-[(Cy3P)2Pt(Br){B(NC5H4-4-R)X}][BArf4] (R = Me, X = NMe2, Pip, Br; R = tBu, X = Pip) were synthesized by addition of Na[BArf4] and a pyridine Lewis base to boryl complexes trans-[(Cy3P)2Pt(Br){B(Br)X}], inducing a formal 1,2-bromide shift from the boron atom to the platinum center. Furthermore, the reactions of [Pt(PCy3)2] with 1,4-(Br2B)2-C6H4 allowed for the isolation of the dinuclear boryl complex 1,4-trans-[{(Cy3P)2(Br)Pt(BBr)}2-C6H4] and trans-[(Cy3P)2Pt(Br)-1-{B(Br)-C6H4-4-{BBr2(PCy3)}}]. The former was treated with K[B(C6F5)4], which afforded the abstraction of both platinum-bound bromides and formation of the dicationic boryl complex 1,4-trans-[{(Cy3P)2Pt(BBr)}2-C6H4][B(C6F5)4]2. This compound was converted into the base-stabilized borylene species 1,4-trans-[{(Cy3P)2(Br)Pt{B(NC5H4-4-Me)}}2-C6H4][B(C6F5)4]2 by reaction with 4-methylpyridine.