Synthesis and characterisation of monomeric and dimeric 2-substituted eta(3)-bonded butadienyl complexes of molybdenum(II)

Addition of excess thiol RSH (R = Et, Pr-n, Pr-i, (n)Bu or (i)Bu) to solutions of [MoCl(CO)(2)(eta(3)-CH2C(COCl)C=CH2)(phen)] (1) (phen = 1,10-phenanthroline) gave good yields of the complexes [MoCl(CO)(2)(eta(3)-CH2C(COSR)C=CH2)(phen)], containing a 2-substituted butadienyl ligand. On reaction of 1 with 1,2-ethanedithiol in 2:1 molar ratio under basic conditions, dimeric complexes were obtained containing two metal centres bridged by a pair of 2-substituted butadienyl groups linked by the dithiol unit. Analogous dimeric complexes containing linked amido eta(3)-butadienyl groups were isolated from a similar 2:1 reaction of 1 and diamines RHN(CH2)(2)NHR (R = H or Me). However, reactions involving 1 and mixed bifunctional reactants HA(CH2)(2)BH (A = NH, B = O, S or A = O, B = S) under the same conditions gave monomeric complexes exclusively, the less electonegative atom of the donor pair remaining unreacted.