Seven-Coordinate MoII-Diiodo Complexes with Benzothiazole-N-Heterocyclic-Carbene Ligands and Their Mo0 Precursors: Synthesis, Structures, and Catalytic Application in the Epoxidation of cis-Cyclooctene

The oxidative addition of I-2 to molybdenum(0) complexes [Mo(CO)(4)(L-NC)] (1-3; L-NC1 = 1-(benzothiazolin-2-yl)-3-allyl-2-ylidene; L-NC2 = 1-(benzothiazolin-2-yl)-3-benzylimidazol-2-ylidene; L-NC3 = 1-(benzothiazolin-2-yl)-3-methylimidazol-2-ylidene) afforded the first isolable and crystallographically elucidated seven-coordinate Mo-II-diiodo complexes, [Mo(-CO)(3)I-2(L-NC)] (4-6), with N-heterocyclic carbene (NHC) ligands(.) The application of complexes 1-6 as precatalysts for the epoxidation of cis-cyclooctene with tert-butyl hydroperoxide (TBHP) as an oxidant has also been studied. Complexes 1-3 performed better than previously reported Mo-0-carbonyl-NHC complexes, thereby producing the epoxide in 80-90% yield after 24h. Complexes 4-6 were superior to complexes 1-3. Complex 5 was the most-active Mo-II-NHC complex, thereby achieving the epoxide in quantitative yield after 6h.