Steroselective Oxidative Addition of Silanes and Hydrogen Halides to the Iridium(I) cis-Phosphine Complexes IrX(CO)(1,2-Bs(diphenylphosphino)ethane), X = Br, CN.
Abstract
The oxidative addition of silanes, RnCl3-nSiH (n = 3, R = Et, Ph, OEt; n = 2, R = Me; n = 1, R = Me), to the Ir(I) cis phosphine complexes IrX(CO)(dppe)(X = Br, CN; dppe = 1,2-bis(diphenylphosphino)ethane) has been found to proceed stereoselectively under kinetic control. Of the four possible diastereomers which can form by concerted cis addition of the Si-H bond to the iridium(I) center, the one having hydride trans to CO and Si trans to P(dppe) is formed initially with >98% steroselectivity. For X = Br, this diastereomer is not the thermodynamically favored product. Isomerization of the initially formed silyl hydride product to the equilibrium mixture of diastereomers follows first order kinetics for the triphenylsilyl derivative with k sub 1 = 0.015/min. the rate of isomerization for the kinetic silyl hydride adducts decreases int he order Et3SiH > Ph3SiH > (OEt)3SiH > Me2C1SiH with the MeCl2SiH derivative not isomerizing even after prolonged heating. The most stable diastereomer for x = Br has hydride trans to Br and silyl trans to P(dppe). For X = CN, the kinetic isomer with H trans to CO and Si trans to P(dppe) is also the most stable isomer, although other isomers are observed to form after initial reaction. Secondary chemistry of the triethylsilyl hydride products for X = Br and CN is observed over longer reaction times leading to the formation of IrHX2(CO)(dppe)(X = Br), IrH2(SiEt3)(CO)(dppe), and Et3SiSiEt3.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 20, 1986
- Accession Number
- ADA164119
Entities
People
- Curtis E. Johnson
- Richard Eisenberg
Organizations
- University of Rochester