Synthesis and reactivity of organochalogen ester substituted η3-butadienyl complexes of Mo(II): crystal structure of [MoCl(CO)2(η3-CH2C(COSePh)CCH2)(1,10-phenanthroline)]·0.5 CH2Cl2

A series of organochalcogen ester substituted η3-butadienyl complexes of the type [MoCl(CO)2(η3-CH2C(COXR)CCH2)(phen)]n (phen=1,10-phenanthroline, R=alkyl, aryl) were prepared from the acyl chloride precursor (1) and either thiols (X=S, n=1–4), selenols (X=Se, n=1,2) or bis(organochalcogen) mercurials, Hg[XR]2 (X=Se, Te, n=1,2), and the structure of the first selenoester substituted η3-butadienyl complex (4) was determined by a single-crystal X-ray diffraction analysis. Reactions of various nucleophiles or electrophiles with 1, 4 or the ester substituted complex, XR=OMe, were examined, and compared to those of related η3-allyl analogues and to their predicted behaviour based upon the structural evidence and molecular modelling calculations.