Dioxomolybdenum(VI) complexes as catalysts for the hydrosilylation of aldehydes and ketones.
The dioxomolybdenum(VI) complexes [MoO2Cl2] (1), [MoO2(acac)2] (2), [MoO2(S2CNEt2)2] (3), [CpMoO2Cl] (4), [MoO2(mes)2] (5) and the polymeric organotin-oxomolybdates [(R3Sn)2MoO4] [R = n-Bu (6), t-Bu (7), Me (8)] were examined as catalysts for the hydrosilylation of aldehydes and ketones with dimethylphenylsilane. Of these, [MoO2Cl2] (1) was the most efficient catalyst, affording quantitative yields of the corresponding silylated ethers at room temperature in acetonitrile. Complexes 2, 4-8 also catalyzed the same reaction but required heating at 80 degrees C and longer reaction times compared with 1. Compound 3 is inactive. The wide scope of molybdenum oxide-mediated hydrosilylation was established with a variety of aldehydes and ketones. Counter intuitively, the activity of is 1 highest in NCMe. In the absence of a carbonyl substrate, [MoO2Cl2(NCBu(t))] (10) reacts with HSiMe2Ph affording [MoO(OSiMe2Ph)Cl2]2 (11) which has been fully characterized by NMR and IR spectroscopy, elemental analyses and mass spectrometry. Addition of radical scavengers strongly slows down the [MoO2Cl2]-based hydrosilylation suggesting the intermediacy of oxygen-centered radicals.
Reis
Patrícia M
PM
Instituto de Tecnologia Química e Biológica da Universidade Nova de Lisboa, Quinta do Marquês, EAN, Apt. 127, 2781-901, Oeiras, Portugal.
Romão
Carlos C
CC
Royo
Beatriz
B
D000447:Aldehydes / Q000737:chemistry*; D002384:Catalysis; D007659:Ketones / Q000737:chemistry*; D015394:Molecular Structure; D008982:Molybdenum / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D017646:Organosilicon Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
D000447:Aldehydes; D007659:Ketones; D009942:Organometallic Compounds; D017646:Organosilicon Compounds; D008982:Molybdenum