Ligand reactions of manganese carbonylisocyanide complexes with amines

Abstract

The complex, cis-Mn(CO) 4(CNCH 3) + 2, I, reacts rapidly with excess CH 3NH 2 at 25° to form the carbamoyl complex fac-Mn(CO) 3(CONHCH 3)(CNCH 3) 2, II. On standing, the carbamoyl complex slowly disappears and the chelated amidinium complex, (OC) 4 MnC(NHCH 3)N(CH 3)C (NHCH 3) +, VI, may be isolated. On reaction with bases such as CH 3NH 2 or (C 2H 5) 3N, complex VI is deprotonated to give (OC) 4 MnC(=NCH 3)N(CH 3)C (NHCH 3), V.`Passage of VI through a silica gel chromatography column leads to some rearrangement and the isolation of cis-Mn(CO) 4(CNCH 3)[C(NHCH 3) 2] +, III, which is an isomer of VI containing CNCH 3 and monodentate amidinium ligands. When treated with base. III is rapidly converted to the chelated form, V. The complex, mer-Mn(CO) 3(CNCH 3) + 3, VII, reacts rapidly in neat n-BuNH 2 to give the carbamoyl complex Mn(CO) 2(CNCH 3) 3(CONHR) (VIII, R = Bu) and no further reaction occurs. At lower concentrations of amine, VIII does not form, but in a slow reaction the chelated amidinium complex, mer-(OC) 3(CH 3NC) MnC(NHCH 3)N(CH 3)C (NHCH 3) +, IX, is produced. The isomer of VII, fac-Mn(CO) 3(CNCH 3) + 3, has also been prepared and it appears to react with CH 3NH 2 giving an amidinium complex which was too unstable to be isolated. Factors affecting the relative reactivities of CO and CNCH 3 ligands with amines are discussed.