Synthesis and Structural Studies of NCN Diimine Palladium Pincer Complexes Bearing <i>m</i>-Terphenyl Scaffolds

The reaction of 2,6-[2-{RNC(H)}C6H4]2C6H3I [R = Ph (4), Cy (5), 2,6-Me2C6H3 (6), 2,4,6-Me3C6H2 (7), (S)-α-methylbenzyl (8)] with Pd2(dba)3 afforded the NCN diimine pincer palladium complexes [2,6-[2-{RNC(H)}C6H4]2C6H3PdI] (9−13) by oxidative addition of the C−I bonds of the ligand precursors. Single-crystal X-ray diffraction analyses of complexes 9−13 reveal formal C2-symmetric environments. Variable-temperature NMR studies of complexes 11 and 12 show hindered rotation about the N−Ar bonds and also suggest that atropisomers of complexes 9−13 do not interconvert on the NMR time scale. Consistent with this proposal, isolation of the two possible isomers of 13 (13a and 13b) was possible, and their structures and NMR properties have been examined in detail.