Theoretical study of rhodium(I) carbene complexes: The structural versatility of phosphino- compared with aminocarbenes

Density functional calculations are reported for complexes of general formula [(carbene)RhCIL2] featuring model phosphino- and amino-carbenes. Both the cis and trans isomers of the rhodium(I) eta(1)-complexes (1-9) were investigated, and the influence of the rhodium co-ligands (L= ethylene, phosphine, or carbon monoxide) was evaluated. In the case of phosphinocarbenes and carbon monoxide as a ligand, a somewhat unusual coordination mode was observed, in which a significant intramolecular Cl-->C-carbene interaction is present. The propensity of phosphino- and aminocarbenes to behave as four electron donors was also investigated both structurally and energetically on the related eta(2)-complexes 10-18. These results as a whole emphasize the structural versatility of phosphino- compared with aminocarbene complexes.