Chemical Properties of Mononuclear and Dinuclear Phenylplatinum(II) Hydroxo Complexes with Cod Ligands. Transmetalation of Arylboronic Acids, Coupling of the Phenyl Ligands, and Carbonylation

Abstract

The reaction of bpy with [{Pt(Ph)(cod)}2(μ-OH)](BF4) (1-BF4; cod = 1,5-cyclooctadiene) in acetone splits a Pt−O bond to yield a mixture of Pt(CH2COMe)(Ph)(cod) (2) and [Pt(Ph)(bpy)(cod)](BF4) (3-BF4), whereas a similar reaction in toluene produces 3-BF4 and Pt(OH)(Ph)(cod) (4). The complex 4 was obtained in solution and was not isolated as analytically pure crystals because of its gradual disproportionation, giving PtPh2(cod) (5). The dinuclear complex 1-BF4 reacts with ArB(OH)2 (Ar = Ph, C6H2F3-2,4,6) to form 5 and Pt(C6H2F3-2,4,6)(Ph)(cod) (6), respectively, via aryl group transfer from boron to platinum. The accompanying formation of B(OH)3 has been confirmed by 11B{1H} NMR spectroscopy. The reaction of BF3·Et2O with 1-BF4 followed by the addition of NH4Cl(aq) produces biphenyl and PtCl2(cod), which takes place possibly via a dinuclear intermediate. The cationic dinuclear complex 1-BF4 reacts with CO (1 atm) to form benzophenone. Since the reactions of AgBF4 with Pt(COPh)(I)(cod) (7) and CO with [Pt(Ph)(THF)(cod)](BF4) also yield benzophenone, the above carbonylation of 1-BF4 is considered to involve mononuclear intermediates.