Portal de Periódicos da CAPES

Mononuclear and Binuclear Cyclopentadienyl Oxo Molybdenum and Tungsten Complexes: Syntheses and Applications in Olefin Epoxidation Catalysis

2005; American Chemical Society; Volume: 24; Issue: 11 Linguagem: Inglês

10.1021/om049107b

1520-6041

Ana M. Martins, Carlos C. Romão, Marta Abrantes, C.G. De Azevedo, Jinlan Cui, Alberto R. Dias, M. Teresa Duarte, M.A.N.D.A. Lemos, Tiago Lourenço, Rinaldo Poli,

Organometallic Complex Synthesis and Catalysis

New half-sandwich molybdenum complexes [Mo(CpBz)Cl2(O)] (1), [{Mo(CpBz)(O)2}2(μ-Ο)] (5), and [Mo(CpBz)Cl2]2 (6) (CpBz = C5(CH2Ph)5), the tungsten derivative [W(CpBz)Cl(O)2] (3), and a high yield synthesis of [Mo(CpBz)Cl(O)2] (2) are described. The molecular structures and cyclic voltammetry measurements of 1 and 2 and a comparative study of various molybdenum dioxo complexes as olefin epoxidation catalyst precursors are also presented. The performance of [Mo(CpPri4)Cl(O)2] (9) as cyclooctene epoxidation catalyst using TBHP as oxidant was determined and compared with other [MoCp'Cl(O)2] complexes (Cp' = C5H5 (7), C5Me5 (8), CpBz (2)) to assess the activity dependence on the ring substituents. Under the same experimental conditions, bimetallic compounds [{MoCp'(O)2}2(μ-Ο)] (Cp' = CpBz (5), Cp* (10), CpBut3 (11), CpPri4 (12)) have been tested and [CpMoO2]2O was checked in aqueous solution, with H2O2 and TBHP as oxidant. Finally, [Mo(CpBz)(CO)3CH3] (4) was used as a catalyst precursor for cyclooctene epoxidation in the presence of TBHP. The analogy between the behaviors displayed by this complex and complex 2 is discussed.