Highly Efficient Large Bite Angle Diphosphine Substituted Molybdenum Catalyst for Hydrosilylation

作者：Chakraborty Subrata; Blacque Olivier; Fox Thomas; Berke Heinz^*

来源：ACS Catalysis, 2013, 3(10): 2208-2217.

DOI：10.1021/cs4004276

• hemogeneous catalysis
• hydrosilylation
• molybdenum
• diphosphine
• aldehydes
• ketones

Treatment of the complex Mo(NO)Cl-3(NCMe)(2) with the large bite angle diphosphine, 2,2'-bis(diphenylphosphino)diphenylether (DPEphos) afforded the dinuclear species [Mo(NO)(P boolean AND P)Cl-2](2)[mu Cl](2) (P boolean AND P = DPEphos = (Ph2PC6H4)(2)O (1) 1 could be reduced in the presence of Zn and MeCN to the cationic complex [Mo(NO)(P boolean AND P)(NCMe)(3)](+)[Zn2Cl6](1/2)(2-) (2). In a metathetical reaction the [Zn2Cl6](1/2)(2-) counteranion was replaced with NaBAr4F (BAr4F = [B{3,5-(CF3)(2)C6H3}(4)]) to obtain the [BAr4F](-) salt [Mo(NO)(P boolean AND P)(NCMe)(3)](+)[Bar(4)(F)](-) (3). 3 was found to catalyze hydrosilylations of various para substituted benzaldehydes, cyclohexanecarboxaldehyde, 2-thiophenecarboxaldehyde, and 2-furfural at 120 degrees C. A screening of silanes revealed primary and secondary aromatic silanes to be most effective in the catalytic hydrosilylation with 3. Also ketones could be hydrosilylated at room temperature using 3 and PhMeSiH2. A maximum turnover frequency (TOF) of 3.2 x 10(4) h(-1) at 120 degrees C and a TOF of 4400 h(-1) was obtained at room temperature for the hydrosilylation of 4-methoxyacetophenone using PhMeSiH2 in the presence of 3. Kinetic studies revealed the reaction rate to be first order with respect to the catalyst and silane concentrations and zero order with respect to the substrate concentrations. A Hammett study for various para substituted acetophenones showed linear correlations with negative rho values of -1.14 at 120 degrees C and -3.18 at room temperature.

• 出版日期2013-10