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 - (Cy 3 P) 2 Pt (Br) B (NC 5 H 4 -4-R) XBAr f 4 (R = Me, X = NMe 2, Pip, Br; R = t Bu, X = Pip) were synthesized by addition of NaBAr f 4 and a pyridine Lewis base to boryl complexes trans - (Cy 3 P) 2 Pt (Br) B (Br) X, inducing a formal 1, 2-bromide shift from the boron atom to the platinum center. Furthermore, the reactions of Pt (PCy 3) 2 with 1, 4- (Br 2 B) 2 -C 6 H 4 allowed for the isolation of the dinuclear boryl complex 1, 4- trans - (Cy 3 P) 2 (Br) Pt (BBr) 2 -C 6 H 4 and trans - (Cy 3 P) 2 Pt (Br) -1-B (Br) -C 6 H 4 -4-{BBr 2 (PCy 3) }. The former was treated with KB (C 6 F 5) 4, which afforded the abstraction of both platinum-bound bromides and formation of the dicationic boryl complex 1, 4- trans - (Cy 3 P) 2 Pt (BBr) 2 -C 6 H 4 B (C 6 F 5) 4 2. This compound was converted into the base-stabilized borylene species 1, 4- trans - (Cy 3 P) 2 (Br) Pt{B (NC 5 H 4 -4-Me) } 2 -C 6 H 4 B (C 6 F 5) 4 2 by reaction with 4-methylpyridine.