OXIDATIVE ADDITION OF B-B BONDS BY RHODIUM(I) PHOSPHINE COMPLEXES - MOLECULAR-STRUCTURES OF B(2)CAT(2) (CAT=1,2-O2C6H4) AND ITS 4-BU(T) AND 3,5-BU(2)(T) ANALOGS

The B-B-bonded compounds B-2(1,2-O2C6H4)(2) (1a), B-2(1,2-O-2-4-Bu(t)C(6)H(3))(2) (1b), B-2- (1,2-O-2-3,5-Bu(t)C(6)H(2))(2) (1c), and B-2(OCH(2)CMe(2)CH(2)O)(2) (1e) have been prepared, and the crystal structures of 1a-c are reported. Compounds 1a-c react rapidly at room temperature under stoichiometric conditions with either [(PPh(3))(2)Rh(mu-Cl)](2) (4) or [(PPh(3))(3)RhCl] (6) via oxidative addition of the B-B bond, yielding the bis(boryl) complexes [(PPh(3))(2)RhCl(B-1,2-O(2)C(6)H(4-n)Bu(n)(t))(2)] (3a-c) in quantitative yield. In contrast, no reaction was observed between the alkoxydiboron compound 1e or B-2(pin)(2) (1d; pin = OCMe(2)CMe(2)O) and 4 or 6 under these conditions.