Synthesis and solution structure of palladium tris(o-tolyl)phosphine mono(amine) complexes

The complex(es) resulting from a 1:4 mixture Of Pd2(DBA)3 and P(o-tol)3 react with aryl bromides or aryl iodides p-XC6H4R (X = Br, I; R = Me, t-Bu, OMe) to generate the corresponding halide dimers {Pd[P(o-tol)3](p-C6H4R)(μ-X)}2 (X = Br, R = t-Bu (1), Me (2), OMe (3); X = I, R = t-Bu (4), Me (5), OMe (6)) in 46-76% yield. Iodide dimer 5 reacts with AgOTf in acetonitrile to form the cationic bis(acetonitrile) complex {Pd[P(o-tol)3](p-C6H4-Me)(CH 3CN)2]}+OTf- (8) which was treated in situ with LiCl to form the chloride dimer {Pd[P(o-tol)3](p-C6H4Me)(μ-Cl)}2 (9) in 93% yield. The p-tolyl halide dimers 2, 5, and 9 react with N-benzylmethylamine to generate the corresponding 1:1 palladium amine adducts Pd[P(o-tol)3](p-C6H4Me)[HN(Me)Bn]X (X - Cl (12), 85%; X = Br (13), 72%; X = I (14), 77%). Reaction of a mixture of Pd2(DBA)3 and P(o-tol)3 with the haloamines 2-IC6H4(CH2)2N(H)Bn, 2-BrC6H4CH2N(H)(p-tolyl), and 2-BrC6H4(CH2)3N(H)Bn gave the chelated palladium amine complexes Pd[P(o-tol)3](2-C6H4(CH2) 2N(H)Bn]I (18, 71%), Pd[P(o-tol)3][2-C6H4CH 2N(H)(p-tolyl)]Br (19, 77%), and Pd[P(o-tol)3](2-C6H4(CH2) 3N(H)Bn]Br (21, 24%), respectively. Variable-temperature 1H and 31P NMR analysis of 12-14 and related complexes was consistent with hindered rotation about the P-C bonds, with predominant formation of the exo2-P(o-tol) conformer, and hindered rotation about the Pd-P bond with formation of three unequally populated rotamers.

Duke Scholars

Author Ross A. Widenhoefer Chemistry