Reactions of isocyanides with rhodium porphyrins: formation of formimidoyl and carbamoyl complexes and CN-R bond cleavage

Abstract

Reactions of alkyl and aryl isocyanides with (octaethylporphyrinato)rhodium hydride, (OEP)Rh-H, (octaethylporphyrinato)rhodium(II) dimer, [(OEP)Rh][sub 2] and (tetramesitylporphyrinato)rhodium(II), (TMP)Rh, have been investigated for comparison with CO reactivity. Alkyl and aryl isocyanides interact with (OEP)Rh-H to form 1:1 adducts, (OEP)Rh(H)(CNR), which react further to produce formimidoyl complexes, (OEP)Rh-CH=NR, in analog with the reaction of (OEP)Rh-H with CO that produces a formyl complex, (OEP)Rh-CHO. [(OEP)Rh][sub 2] forms 1:1 complexes with isocyanides where the 2,6-dimethylphenyl isocyanide derivative persists at equilibrium, but alkyl isocyanides undergo CN- alkyl bond cleavage to form alkyl, (OEP)Rh-R and cyanide, (OEP)Rh(CN)(CNR), complexes. No evidence was obtained for bridging isocyanide species analogous to the dimetal ketone RhC(O)Rh and dimetal diketone RhC(O)C(O)Rh complexes observed in reactions of [(OEP)Rh][sub 2] with CO. Carbamoyl complexes, (OEP)Rh-C(O)NHR, are formed in reactions of [(OEP)Rh][sub 2] with CNR and H[sub 2]O or CO and RNH[sub 2]. 24 refs., 7 figs., 3 tabs.