Synthesis and Reactivity of Molybdenum Complexes Containing Functionalized Alkynyl Ligands: A Photochemically Activated CO-Releasing Molecule (PhotoCO-RM)

Abstract

Reaction of [MoCl(η5-C5H5)(CO)3] with propargyl alcohols HC≡CCR1R2OH in the presence of catalytic amounts of CuI and using NEt2H as solvent results in the formation of alkynyl complexes [Mo(C≡CCR1R2OH)(η5-C5H5)(CO)3]. The structure of the complexes where R1 = R2 = Me and R1 = Me, R2 = Ph were confirmed by single-crystal X-ray diffraction. The method could be extended to a range of propargyl ethers and propargyl esters, which allowed for the preparation of molybdenum complexes containing pendant salicylate and β-d-fructopyranose groups. The alkynyl complex [Mo(C≡CCH2OH)(η5-C5H5)(CO)3] undergoes a further reaction with NEt2H to give the substituted allyl complex [Mo(η3-H2CC{NEt2}CHC{O}NEt2)(η5-C5H5)(CO)3]. Similar products could be obtained from the reaction of [MoCl(η5-C5H5)(CO)3] with HC≡CCH2OH in the presence of CuI using pyrrolidine or piperidine as solvent. In the case of the reaction with piperidine a further product could be isolated that has arisen from the coupling of two propargyl alcohol molecules to afford a butadienyl ligand. The CO-releasing properties of a number of these novel complexes have been investigated. In the case of the water-soluble alkynyl complex containing a β-d-fructopyranose group CO release was shown to be promoted by exposure to UV light, revealing a new class of photochemically activated CO-releasing molecules (PhotoCO-RMs).