Structural Features and Dynamical Behavior of Heteroleptic trans-C,C-Bisaryl-Platinum(II) and -Palladium(II) Complexes

Several heteroleptic trans- bisaryl-Pt II complexes, trans-C,C- [Pt(NCN)R] ( 6 − 9 ), have been prepared starting from the readily available precursor [PtCl(NCN)] ( 1, NCN = [C 6 H 3 (CH 2 NMe 2 ) 2 -2,6] - ) and ortho- substituted phenyl- or naphthyllithium reagents, respectively. Variable-temperature 1 H NMR spectroscopy shows that in solution the NCN ligand is η 3 -coordinated and that rotation of the trans -aryl ligand about the Pt−C ipso bond is slow or even nonexistent on the NMR time scale. Moreover, in the temperature range −80 to +90 °C no dissociation of the Pt−N (NCN) coordination occurs. In contrast, the analogous Pd II complex 13 shows fluxional behavior of the nitrogen-to-metal coordination (above 0 °C). The dynamic properties of this type of complexes can thus be tuned by the choice of metal. The crystal structure determinations of two trans-C,C -[M(NCN)(C 10 H 6 (CH 2 NMe 2 )-2)] complexes ( 8 (M = Pt), 13 (M = Pd)) are reported. The most significant feature in these structures is that the η 3 - N,C,N -coordinating NCN ligand present in 1 has been retained in 8 and 13; that is, the ortho- (dimethylamino)methyl group of the naphthyl ligand remains noncoordinating and cannot compete with the ortho -(dimethylamino)methyl groups of the NCN ligand.