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)(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 -C 6 H 4 Me)(CH 3 CN) 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)(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 -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-IC 6 H 4 (CH 2 ) 2 N(H)Bn, 2-BrC 6 H 4 CH 2 N(H)( p -tolyl), and 2-BrC 6 H 4 (CH 2 ) 3 N(H)Bn gave the chelated palladium amine complexes Pd[P( o -tol) 3 ](2-C 6 H 4 (CH 2 ) 2 N(H)Bn]I ( 18, 71%), Pd[P( o -tol) 3 ][2-C 6 H 4 CH 2 N(H)( p -tolyl)]Br ( 19, 77%), and Pd[P( o -tol) 3 ](2-C 6 H 4 (CH 2 ) 3 N(H)Bn]Br ( 21, 24%), respectively. Variable-temperature 1 H and 31 P 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 Pd−P bond with formation of three unequally populated rotamers.