Reversible Insertion of Methyl Isothiocyanate into Copper(I) Aryloxides

MeNCS undergoes insertion into the copper(I)-aryloxide bond to form [N-methylimino(aryloxy)methanethiolato]copper(I) complexes. This insertion occurs in the absence of ancillary ligands unlike the analogous insertion of PhNCS. The reaction with 4-methylphenoxide results in the formation of hexakis[[N-methylimino(4-methylphenoxy)methanethiolato]copper(I)] (1), which has been characterized by X-ray crystallography. Crystal data for 1: hexagonal R&thremacr;, a = 12.365(3) Å, c = 36.734(16) Å, gamma = 120 degrees, Z = 3, V = 4863(3) Å(3), R = 0.0306. Reactions of 2,6-dimethyl- and 4-chlorophenoxides also result in analogous copper(I) complexes 2 and 3. Addition of stochiometric amounts of PPh(3) to the oligomeric complexes typically results in the extrusion of MeNCS. The ease of extrusion is dependent on the substituents on the aryloxide, and this deinsertion is accelerated by water. However, the extrusion reaction is slow enough in the case of the N-methylimino(2,6-dimethylphenoxy)methanethiolate complex and the isolation of an intermediate monomeric product bis(triphenylphosphine)[N-methylimino(2,6-dimethylphenoxy)methanethiolato]copper(I) (4) is possible. Crystal data for 4: triclinic P&onemacr;, a = 10.088(2) Å, b = 11.302(1) Å, c = 17.990(2) Å, alpha = 94.06(1) degrees, beta = 95.22(2) degrees, gamma = 103.94(1) degrees, Z = 2, V = 1974.4(7) Å(3), R = 0.0361. In the presence of of PPh(3), the insertion reaction becomes reversible. This allows the exchange of the heterocumulene MeNCS or the aryloxy group in these molecules with another heterocumulene or a phenol, respectively, when catalytic amounts of PPh(3) are added. Oligomers with exchanged heterocumulmes and phenols could be characterized by independent synthesis.