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

The complex(es) resulting from a 1:4 mixture of Pd-2(DBA)(3) and P(o-tol)(3) react with aryl bromides or aryl iodides p-XC(6)H(4)R (X = Br, I; R = Me, T-Bu, OMe) to generate the corresponding halide dimers {Pd[P(o-tol)(3)](p-C(6)H(4)R)(mu-X)}(2) (X = Br, R = t-Bu (1), Me (2), OMe (3); X = I, R = t-Bu (4), Me (5), OMe (5)) 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)(CH3CN)(2)]}(+)OTf(-) (8) which was treated in situ with LiCl to form the chloride dimer {Pd[P(o-tol)(3)](p-C(6)H(4)Me)[HN(Me)Bn]X (X = Cl (12), 85%; X = Br (13), 72%; X = I (14), 77%). Reaction of a mixture of Pd-2(DBA)(3) and P(o-tol)(3) with the haloamines 2-IC6H4(CH2)(2)N(H)Bn, 2-BrC6H4CH2N(H)(p-tolyl, and 2-BrC6H4(CH2)(3)N(H)Bn gave the chelated palladium amine complexes Pd[P(o-tol)(3)](2-C6H4(CH2)(2)N(H)Bn]I (18, 71%), Pd[P(o-tol)(3)][2-C6H4CH2N(H)(p-tolyl)[Br (19, 77%), and Pd[P(o-tol)(3)](2-C6H4(CH2)(3)N(H)Bn]Br (21, 24%), respectively. Variable-temperature H-1 and P-31 NMR analysis of 12-14 and related complexes was consistent with hindered rotation about the P-C bonds, with predominant formation of the exo(2)-P(o-tol) conformer, and hindered rotation about the the Pd-P bond with formation of three unequally populated rotamers.