Homoleptic Rhodium Pyridine Complexes for Catalytic Hydrogen Oxidation

The homoleptic rhodium pyridine complex [Rh(py)₄]⁺ ([1]⁺) is prepared from simple precursors. Lacking good π-acceptor ligands but being sterically protected, [1]⁺ reversibly oxidizes to colorless [Rh(py)₄(thf)₂]²⁺. This monomeric S = 1/2 Rh(II) complex activates H₂ to give [HRh(py)₄L]²⁺, which can also be generated by protonation of [1]⁺. The Rh(III)-H bond is weak, being susceptible to H atom abstraction as well as deprotonation. These results underpin a novel catalytic system for the oxidation of H₂ by ferrocenium.

Rhodium(ii) dimers without metal–metal bonds

Oxidation of (^MeBDI)Rh(cyclooctene) (^MeBDI = [2,6-Me₂C₆H₃NCMe]₂CH) with Br₂ or I₂ produces paramagnetic halide-bridged Rh^II dimers [(^MeBDI)Rh]₂(μ-X)₂ without a direct Rh–Rh bond.

Ruthenium, osmium and rhodium complexes of 1,4-diaryl 1,4-diazabutadiene: radical versus non-radical states

Molecular and electronic structures of the ruthenium, osmium and rhodium complexes of 1,4-di(3-nitrophenyl)-1,4-diazabutadiene (L^DAB) and their redox series are reported.