Ruthenium xantphos complexes in hydrogen transfer processes: reactivity and mechanistic studies.
The in situ combination of [Ru(PPh3)3(CO)H2] with xantphos is catalytically active for the alkylation of alcohols with the ketonitrile (t)BuC(O)CH2CN in a model oxidation-Knoevenagel-reduction process. The precursor complex [Ru(xantphos)(PPh3)(CO)H2] was isolated and reacted with stoichiometric amounts of PhCH2OH and PhCHO. Under these conditions, the alcohol is decarbonylated to afford [Ru(xantphos)(CO)2H2] and finally [Ru(xantphos)(CO)3], both of which prove to be less active for catalysis than the starting complex. The reactivity of the xantphos system contrasts with that of [Ru(dppp)(PPh3)(CO)H2], which is catalytically inactive for the Knoevenagel reaction and fails to show any stoichiometric reactivity with alcohols.
Ledger
Araminta E W
AE
Department of Chemistry, University of Bath, Claverton Down, Bath, UK.
Slatford
Paul A
PA
Lowe
John P
JP
Mahon
Mary F
MF
Whittlesey
Michael K
MK
Williams
Jonathan M J
JM