Reactions of aminoboron compounds with palladium and platinum complexes

Abstract

Reactions of 3-NH2C6H4B(OH)2 (1, APBA) with [MCl4]2- (M = Pd, Pt) give the boronic acid-containing complexes, MCl2(APBA)2 (M = Pd, 2; M = Pt, 3). Addition of 1 to [PdCl2(COE)]2 (COE = η2-C8H14) ultimately led to PdCl2(APBA)2 (2). The pinacol derivative PdCl2(APBpin)2 (5, pin = O2C2Me4) was characterized by an X-ray diffraction study. Crystals of 5 were monoclinic, a = 13.836(5), b = 14.937(5), c = 11.287(5) Å, β = 99.042(9)°, Z = 2, with space group P21/c. Monoalkene complexes PtCl2(COE)(APBA) (8) and PtCl2(COE)(APBpin) (9) were generated from the addition of APBA and APBpin, respectively, to [PtCl2(COE)]2. Reactions of 2-NMe2CH2C6H4B(OH)2 (10) with palladium complex [PdCl2(COE)]2 proceed via selective B—C bond cleavage to give the cyclopalladated dimer [PdCl(2-NMe2CH2C6H4)]2 as the major amine-containing product. Likewise, reactions with borinic esters H2NCH2CH2OBR2 (R = Bu, 14; R = Ph, 15) give products derived from cleavage of the B—O bond. The unique palladium complex PdCl2[3-NC5H4B(OH)2]2 (19) was prepared by addition of (3-NC5H4BEt2)4 (18) to [PdCl2(COE)]2 in wet methylene chloride, where adventitious water was used to convert the organoborane product into the corresponding boronic acid moiety.Key words: aminoboronic acids, platinum, palladium, cyclomηllation.