Carbonyl ligand substitution at rhodium in the heterometallic cluster [PPN] 2[Re 7C(CO) 21Rh(CO) 2]. A reactivity comparison with mononuclear ( n5-C 5H 5Rh(CO) 2 and related compounds

Abstract

The heteometallic cluster compound [PPN] 2[Re 7C(CO) 21Rh(CO) 2] reacts with tertiary phosphines and phosphites selectively at the rhodium center to form the mono-substituted products [PPN] 2[Re 7C(CO) (L)]. Isolated compounds have been characterized by standard analytical and spectroscopic methods. Kinetics studies have shown that the reaction proceeds by an overall second-order process, first order in complex and first order in nucleophile. The second-order rate constants have been analysed in terms of electronic and steric effects. The substitution rates at the rhodium center in the cluster are compared with those for the analogous mononuclear complexes ( n 5-C 5 H 4 X) Rh( CO) 2 previously studied by Basolo and co-workers.