Borole Derivatives. 23. Reversible Carbonylation and Lewis Base Degradation of the Heterocubane [Rh(μ3-I)(C4H4BPh)]4and of the Bis(borole) Complex RhI(C4H4BPh)2and Synthesis and Structure of the Dinuclear Complex Cp*Rh(μ-I)3Rh(C4H4BPh)1

Abstract

The heterocubane [Rh(μ3-I)(C4H4BPh)]4 (2a) readily adds Lewis bases to form the mononuclear products RhI(py)2(C4H4BPh) (4), and RhI(bpy)(C4H4BPh) (7), the labile solution species RhI(NCMe)2(C4H4BPh) (8) and RhI(CO)2(C4H4BPh) (9), RhI(PPh3)2(C4H4BPh) (11), the 1,1‘-bis(diphenylphosphino)ferrocene complex RhI(dppf)(C4H4BPh) (13), and the norbornadiene complex RhI(nbd)(C4H4BPh) (14) as well as the dinuclear products [Rh(μ-I)(py)(C4H4BPh)]2 (5), [Rh(μ-I)(CO)(C4H4BPh)]2 (10), and the bis(diphenylphosphino)methane complex [Rh2(μ-I)2(μ-dppm)(C4H4BPh)2] (12). The complexes 5 and 10 exist as mixtures of cis and trans isomers; the isomeric carbonyls 10 interconvert slowly at ambient temperature, while the isomeric pyridine complexes 5 show fast interchange on the NMR time scale at 20 °C and low-temperature limiting spectra at −80 °C. The heterocubane also adds (RhI2Cp*)2 (which acts as a Lewis base and as a Lewis acid) to produce the novel unsymmetrical dinuclear complex Cp*Rh(μ-I)3Rh(C4H4BPh) (15). Complex 15 was ...