Ligand- and oxidation state-dependence of structure of triazenido-bridged complexes with face-to-face and open-book dirhodium cores: MO studies and the crystal structure of [Rh2(µ-CO)(bipy)(dppm)(µ-RNNNR)2][PF6]2·2CH2Cl2(R =p-tolyl)

Abstract

Treatment of [{Rh₂l(CO)(bipy)(µ-RNNNR)₂}₂][PF₆]₂2 with AgPF₆ and dppm gives [Rh₂(µ-CO)(bipy)(L–L)(µ-RNNNR)₂]²⁺(5; L–L = dppm), X-ray and MO studies on which show that it may be viewed as an open-book [Rh₂]⁶⁺ core bridged by a ‘ketonic’ CO^2– ligand; this isomer is in equilibrium in solution with a face-to-face isomer in which the carbonyl ligand is terminally bound to one metal only, a related open-book to face-to-face conversion occurring on one-electron reduction of (5; L–L = dppe) to [Rh₂(CO)(bipy)(dppe-p)(µ-RNNNR)₂]⁺7.