ALKYNE AND CO COUPLING REACTIONS IN DIMANGANESE CARBONYL-COMPLEXES - THE REACTIONS OF MN2(CO)9(NCME) WITH HC=CCO2ME

Four compounds Mn2(CO)8{mu-O=C[C(H)=C(CO2Me)]2}, 2, 35%, (OC)4Mn[trans-mu-HC=C-(CO2Me)]Mn(CO)5, 3, 3%, (OC)4Mn[C(CO2Me)=C(H)C(=O)C(H)=C(CO2Me)C(H)=C(CO2Me)]Mn(CO)4, 4, 20%, and (OC)4Mn[C(CO2Me)=C(H)C(=O)C(H)=C(CO2Me)C(H)=CH-(CO2Me)], 5, 5% yield, were obtained from the reaction of Mn2(CO)9(MeCN), 1, with HC=CCO2Me in hexane solvent at 25-degrees-C. Compounds 3-5 are new. Compound 3 is a dimetalated olefin complex formed by the insertion of the alkyne into the metal-metal bond of 1. Compounds 4 and 5 were characterized by a single-crystal X-ray diffraction analysis. Compound 4 contains two metallacyclic rings (one five membered and one six membered) formed by the coupling of three alkynes to one CO ligand. In the five membered ring the oxygen atom of the CO-derived carbonyl group is coordinated to one of the metal atoms. The six membered ring was formed by one of the alkynes and a coordinated carboxylate group from one of the alkynes coupled to it. Compound 4 was independently obtained from 2 by the addition of 1 equiv of HC=CCO2Me at 25-degrees-C. Compound 5 is similar to 4, but only has one metal atom. A hydrogen atom has replaced the metal atom on the carbon of the six membered ring in 4. Compound 5 was obtained independently from the reaction of 4 with aqueous HCl. The metal atoms in 2 were removed sequentially in a series of reactions with aqueous HCl to yield Mn(CO)4[C(CO2Me)C(H)C(=O)C(H)C(H)CO2Me], 6, in 86% yield and the metal free organic compound MeO2CC(H)C(H)C(=O)C(H)C(H)CO2Me, 20% yield. Crystal Data: (for 4) space group = Pbca, a = 14.905(2) angstrom, b = 12.370(2) angstrom, c = 28.109(6) angstrom, Z = 8, 1642 reflections, R = 0.033; (for 5) space group = P1BAR, a = 11.978(3) angstrom, b = 12.729(3) angstrom, c = 7.020(1) angstrom, alpha = 93.80(2)degrees, beta = 95.93(2)degrees, = 70.86(2)degrees, Z = 2, 1396 reflections, R = 0.035.