Synthesis and Reactivity of a Bioinspired Molybdenum(IV) Acetylene Complex

The isolation of a molybdenum(IV) acetylene (C 2 H 2 ) complex containing two bioinspired 6-methylpyridine-2-thiolate ligands is reported. The synthesis can be performed either by oxidation of a molybdenum(II) C 2 H 2 complex or by substitution of a coordinated PMe 3 by C 2 H 2 on a molybdenum(IV) center. Both C 2 H 2 complexes were characterized by spectroscopic means as well as by single-crystal X-ray diffraction. Furthermore, the reactivity of the coordinated C 2 H 2 was investigated with regard to acetylene hydratase, one of two enzymes that accept C 2 H 2 as a substrate. While the reaction with water resulted in the vinylation of the pyridine-2-thiolate ligands, an intermolecular nucleophilic attack on the coordinated C 2 H 2 with the soft nucleophile PMe 3 was observed to give a cationic ethenyl complex. A comparison with the tungsten analogues revealed less tightly bound C 2 H 2 in the molybdenum variant, which, however, shows a higher reactivity toward nucleophiles.