STUDIES OF THE COUPLING OF ARYL ISOTHIOCYANATES TO BRIDING ALKYNE LIGANDS IN DIRHENIUM CARBONYL-COMPLEXES

Reactions of the lightly stabilized dimetalated olefin complex Re(CO)4[trans-mu-HC=C(CO2-Me)]Re(CO)4(NCMe) (1) with aryl isothiocyanates have yielded a series of complexes having the general formula Re(CO)4[(E)-HC=C(CO2Me)CN(Ar)=S]Re(CO)4 (2a, Ar = p-tolyl; 2b, Ar = Ph; 2c, Ar = p-chlorophenyl). Compounds 2a-c were formed by the loss of NCMe from 1 and the addition and insertion of one isothiocyanate molecule into one of the metal-carbon bonds to form a thioamido group that is chelated to one of the rhenium atoms. When heated to 98-degrees-C, complexes 2a-c were decarbonylated and converted into the dimeric complexes [Re(CO)4[(E)-HC=C(CO2Me)CN(Ar)=S]Re(CO)3]2 (3a, Ar = p-tolyl; 3b, Ar = Ph; 3c, Ar = p-chlorophenyl), in which the sulfur atoms of the thioamido groups bridge the two metal atoms. Decarbonylation of 2a-c at 80-degrees-C in the presence of [Re(CO)4(mu-I)]2 yielded the trirhenium complexes Re(CO)4[mu-(E)-HC=C(CO2Me)CN(Ar)=S]Re2(CO)7(mu-I) (4a, Ar = p-tolyl; 4b, Ar = Ph; 4c, Ar = p-chlorophenyl). These complexes contain a Re(CO)4[(E)-HC=C(CO2Me)CN(Ar)=S]Re(CO)3 grouping similar to that found in the free molecules 2a-c but also have a Re(CO)4I grouping joined to the complex through a bridging thioamido sulfur atom and a bridging iodo ligand. Complexes 1, 2a, 3a, and 4c were characterized by single-crystal X-ray diffraction analyses. Crystal data: for 1, space group P1BAR, a = 9.272(1) angstrom, b = 13.122(2) angstrom, c = 8.509(1) angstrom, alpha = 106.46(1)degrees, beta = 95.78(1)degrees, gamma = 69.85(1)degrees, Z = 2,2097 reflections, R = 0.038; for 2a, space group P2(1)/c, a = 10.317(10 angstrom, b = 15.819(2) angstrom, c = 15.448(3) angstrom, 103.26(1)degrees, Z = 4, 2415 reflections, R = 0.027; for 3a, space group P1BAR, a = 10.361(2) angstrom, b = 12.638(2) angstrom, c = 9.318(2) angstrom, alpha = 91.36(2)degrees, beta = 102.72(2)degrees, gamma = 78.14(1)degrees, Z = 2,1439 reflections, R = 0.031; for 4c, space group Pbca, a = 19.910(4) angstrom, b = 24.294(4) angstrom, c = 12.901(2) angstrom, Z = 8,2716 reflections, R = 0.029.