REACTIONS OF ISOCYANIDE-SUBSTITUTED DIMANGANESE CARBONYL-COMPLEXES WITH ALKYNES - ALKYNE-ISOCYANIDE COUPLING AND THE SYNTHESIS OF METALATED N-SUBSTITUTED PYRIDINES

When activated by Me(3)NO in the presence of MeCN, the compounds Mn-2(CO)(9)(CNR) (1a,b; R = Me, Ph) react with MeO(2)CC=CCO(2)Me to yield the new compounds Mn-2(CO)(8)[mu-(MeO(2)C)C=C(CO(2)Me)C=NR] (2a,b; R = Me, Ph) in yields of 40% and 32%, respectively. Minor products, Mn-2(CO)(7)(CNR)[mu-(MeO(2)C)C=C(CO(2)Me)C=O] (3a,b; R = Me, Ph) were also formed. Compound 2a was characterized crystallographically. The structure shows that the isocyanide ligand was coupled to the alkyne, and the nitrogen atom is coordinated to one of the manganese atoms to form a five-membered cyclo-mangana enimine ring. One of the carboxylate groups is coordinated to the other manganese atom. The compounds I I I Mn-2(CO)(7)[mu-eta(4)-CN(Me)CHCHC(CO(2)Me)C(CO(2)Me)](4a), Mn-2(C O)(7)[mu-eta(4)-CN(Ph)CHCHC(CO2-Me)C(CO(2)Me)](4b), and Mn-2(CO)(7)[mu-eta(4)CN(Me)CHC(CO(2)Me)C(CO(2)Me)C(CO(2)ME)](4c) were prepared in yields of 27%, 32%, and 31%, respectively, by treatment of 2a,b with C2H2 and of 2a with HC2(CO(2)Me) in the presence of UV irradiation. Compound 4a was characterized crystallographically. This compound contains a metalated N-methylpyridine ring formed by a 1,4-cycloaddition of the allkyne to the enimine grouping in compound 2a. One of the metal atoms was shifted to a pi-bonding coordination involving four of the carbon atoms of the pyridine ring. Crystal data: for 2a space group P2(1)/n, a = 10.981(4) Angstrom, b = 11.425(2) Angstrom, c = 16.780(5) Angstrom, beta = 92.00(3)degrees, Z = 4, 1526 reflections, R = 0.041; for 4a space group P2(1)/n, a = 9.655(2) Angstrom, b = 17.538(5) Angstrom, c = 12.599(1) Angstrom, beta = 107.03(1)degrees, Z = 4, 1950 reflections, R = 0.033.