TRIMETALLIC COMPLEXES WITH SIGMA,SIGMA,PI-BONDED THIENYLENE LIGANDS

The reaction of dilithiated (eta5-thiophene)-Cr(CO)3 with 2 equiv of Mn(CO)5X (X = Cl or Br) afforded [(eta1:eta1:eta5-SC{Mn(CO)5}CHCHC{Mn(CO)5})Cr(CO)3] which irreversibly converts into the thermodynamically more stable [(eta1::eta1:eta5-SC{Mn(CO)5}CHCHC{Cr(CO)5)Mn(CO)3]. Insertion of a carbonyl, unit in one of the thio thiopene-manganese sigma-bonds, [(eta1:eta1:eta5-SC{C(O)Mn(CO)5}CHCHC{Mn(CO)5})Cr(CO)3], inhibits this (eta1-tnlMn, eta5-tnlCr) --> (eta1-tnlCr, eta5-tnlMn (tnl = thienylene) metal exchange process. Crystals of 2, C17H2SO13CrMn2, are monoclinic with a = 8.101(2) angstrom, b = 13.024(2) angstrom, c = 21.771(4) angstrom, beta = 99.29(2)degrees, space group P2(1)/c, and Z = 4; and those of 3, C18H2SO14CrMn2, are monoclinic with a = 13.986(3) angstrom, b = 14.053(3) angstrom, c = 12.888(2) angstrom, beta = 112.42(1)degrees, space group P2(1)/c, and Z = 4. At convergence the refined structures yielded R(w) = 0.057 and 0.025 for 2 and 3, respectively, using reflections with I greater-than-or-equal-to 3sigma(I).