The synthesis of novel square-planar, terdentate, aryl-substituted pyridine-diimine Rh(I) and Ir(I) chloro complexes from the free ligands and the bis(µ-chloro) ethylene-bridged dimers [(C 2 H 4 )RhIrCl] 2 is reported. Since attempts to achieve direct conversion to the corresponding hydride and methyl complexes through metathesis of the chloro ligand in these compounds were unsuccessful, synthetic access to more reactive methoxy-and triflate-substituted starting materials was developed. The methoxy and triflate complexes could be successfully converted to the Rh(I) η 2 -BH 4 and Rh,Ir(I) methyl complexes. The structure and bonding and thermodynamics of the methoxy and η 2 -BH 4 species were analyzed by DFT methods. X-ray crystal structures of selected Rh,Ir(I,III) representatives are reported.

The synthesis of the novel diimine 1 is described, and its low/absent propensity for the complexation of group 9 transition metals (Co, Rh, Ir) is rationalized by a potentially difficult C-H activation step required for terdentate coordination. To overcome this problem, deprotonation of this unique C-H bond in 1 with a variety of bases was attempted. The unexpected outcome of these reactions, including the formation of the Meisenheimer complex 3 by addition of butyllithium, is reported. In addition, the formation of the double-addition product 4 through reaction with t-BuLi is described. Deprotonation at the diimine methyl group with the hard base lithium dimethylamide gives the corresponding diketiminate 5. The structures of the novel compounds 1 and 3-5 were unambiguously confirmed by X-ray crystal structure analyses.