Transition Metal Complexes with Sterically Demanding Ligands, 3.¹Synthetic Access to Square-Planar Terdentate Pyridine−Diimine Rhodium(I) and Iridium(I) Methyl Complexes:  Successful Detour via Reactive Triflate and Methoxide Complexes

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.