Journal of Molecular Catalysis A-Chemical, Vol.249, No.1-2, 60-64, 2006
Rhodium(III) complexes containing the ligand 2,6-bis[4'-(S)-isopropyloxazolin-2'-yl]pyridine ((S,S)-Pr-i-pybox): Efficient catalysts for asymmetric hydrosilylation of acetophenone
The dinuclear complexes [Rh-2(mu-Cl)(2)(R)(2){(S,S)-Pr-i-pybox}(2)][BF4](2) (R=(E)-C(Me)=CH(Ph), C(Ph)=CH2) have been synthesized by the reaction of the complexes trans-[RhCl2(R){(S,S)-Pr-1-pybox}] (R=(E)-C(Me)=CH(Ph), C(Ph)=CH2) with AgBF4. The rhodium(III) complexes cis-[RhCl2(R){(S,S)-Pr-i-pybox}] (R=COPh, CH2C(Me)=CH2, CH2CH=CH2, CH2CH=CH(Ph), CH=C=CH2) and trans-[RhCl2{(E)C(Me)=CH(Ph)}{(S,S)-Pr-i-pybox}], recently reported, and the novel dinuclear complex [Rh-2(mu-Cl)(2){(E)-C(Me)=CH(Ph)}(2){(S,S)-Pr-i-pybox}21[BF4]2, exhibit high enantioselectivity in the hydrosilylation of acetophenone affording (S)-l-phenylethanol with high conversions and up to 89% ee. The species "RhCl{(S,S)-Pr-i-pybox}" is proposed as the real active rhodium catalyst and a pathway for its formation is also tentatively provided. (c) 2006 Elsevier B.V. All rights reserved.