REACTIONS OF ISOCYANIDES WITH RHODIUM PORPHYRINS - FORMATION OF FORMIMIDOYL AND CARBAMOYL COMPLEXES AND CN-R BOND-CLEAVAGE

Reactions of alkyl and aryl isocyanides with (octaethylporphyrinato)rhodium hydride, (OEP)Rh-H, (octaethylporphyrinato)rhodium(II) dimer, [(OEP)Rh]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 analogy with the reaction of (OEP)Rh-H with CO that produces a formyl complex, (OEP)Rh-CHO. [(OEP)Rh]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(0)C(0)Rh complexes observed in reactions of [(OEP)Rh]2 with CO. Carbamoyl complexes, (OEP)Rh-C(O)NHR, are formed in reactions of [(OEP)Rh]2 with CNR and H2O or CO and RNH2. The crystal and molecular structures were determined for (OEP)Rh-C(O)NH(C6H3(CH3)2) which crystallizes in the triclinic space group P1 with unit cell dimensions a = 12.256(3) angstrom, b = 13.234(2) angstrom, c = 15.075(3) angstrom, alpha = 61.79(2)-degrees, beta = 75.89(2)-degrees, gamma = 73.39(l)-degrees, V = 2047.7(7) angstrom3, and Z = 2.