The 2-mercapto-1-methylimidazolyl moiety as a bridging ligand in complexes of gallium, rhenium, and molybdenum

Abstract

The synthesis and characterization of complexes containing the 2-mercapto-1-methylimidazolyl ligand are described. [Formula: see text] occurs as a dimer, crystals of which are monoclinic, C2/c, a = 14.140(2), b = 7.4098(4), c = 18.024(2) Å, β = 106.38(1)°, Z = 4 dimers; the structure was determined by conventional heavy atom methods and refined by full-matrix least-squares techniques to a final R value of 0.039 for 1767 reflections. The crystal contains centrosymmetric dimeric molecules, with a central 8-membered ring, formed by mercaptoimidazolyl ligand bridging between dimethylgallium groups; galliumm has tetrahedral geometry, with no tendency to five-coordination, Ga—S = 2.3697(8), Ga—N = 2.019(2) Å. Reaction of [Formula: see text] L−, with [Re(CO)4Cl]2 results in the formation of LRe(CO)3, whose physical properties indicate a fac arrangement of the organogallate ligand. Attempts to synthesize corresponding LMo(η3-C4H7)(CO)2 and LMo(η3-C3H5)(CO)2 complexes yielded the dimeric species [Formula: see text] and [Formula: see text] Crystals of the [Formula: see text] complex are monoclinic, I2/a, a = 15.057(2), b = 9.4853(9), c = 18.240(2) Å, β = 108.67(1)°, Z = 4 dimers, R = 0.028 for 2363 reflexions. The structure contains dimeric molecules with C2 symmetry, and five fused rings, a central group of three 4-membered rings being formed by bonding of the S atoms of the ligands to both Mo atoms (in contrast to the gallium complex). The molecule has a U-shape, with Mo atoms having pseudo-octahedral environments, Mo—S = 2.6868(7), 2.5576(7), Mo—N = 2.253(2), Mo—CO = 1.950(2), Mo—C(allyl) = 2.259(3), 2.326(3) Å. Considerable strain in the chelate rings is indicated by angles as low as S—Mo—N = 63.9(1)°.