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The complexes Mo{η5‐C5H4[CH(CH2)3]‐η1‐CH}(CO)3 (2a) and W{η5‐C5H4[CH(CH2)3]‐η1‐CH}CO)3 (2b) were synthesized by reacting spiro[4.2]bicyclo[4.1]deca‐6,8‐diene (1) with the tri(acetonitrile)tri(carbonyl)metal complexes M(CO)3(CH3CN)3 (M=Mo, W). Thermogravimetric (TGA) measurements confirm that the complexes are stable up to 140 °C in air in the solid state. The complexes 2a and 2b are very active catalysts at room temperature for the epoxidation of cyclooctene with tert‐butyl hydroperoxide (TBHP) as oxidant, reaching TOFs of up to 3650 h−1. Complex 2a achieves a quantitative product yield without formation of any by‐products within 1.5 h, outperforming previously published ansa compounds and performing on par with the cyclopentadienyltri(carbonyl)(halo)‐ or (alkyl)molybdenum compelxes CpMo(CO)3R (R=Hal, Me, Et).

Abstract:The molybdenum and tungsten compounds (MoA C H T U N G T R E N N U N G {h-CH}(CO) 3 ) (2a, 3a n = 3; 2b, 3b n = 4; 2c, 3c n = 5; 2d, 3d n = 6) were synthesized by reacting the spiro-bicyclic compounds 1a-d with theNMR spectroscopy, as well as X-ray diffraction studies, confirm the formation of an intramolecular ansa bridge. The complexes display a good stability in the solid state (stable up to 180 8C under air, as determined by thermogravimetric studies) and are highly active catalysts at room temperature (molybdenum compounds) or above (tungsten compounds) in olefin epoxidation. In the case of cyclooctene as substrate, TOFs up to ca. 11800 h À1 are obtained. Moreover, most of the catalysts described here display a high selectivity in the epoxidation of cis-and transstilbene. In addition, the novel complexes were compared with previously synthesized related compounds, at least matching their catalytic performances.