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6595002 
Journal Article 
Amino-phosphanes in RHI-catalyzed hydroformylation: New mechanistic insights using D2O as deuterium-labeling agent 
Andrieu, J; Camus, JM; Balan, C; Poli, R; , 
2006 
Yes 
European Journal of Inorganic Chemistry
ISSN: 1434-1948
EISSN: 1099-0682 
WILEY-V C H VERLAG GMBH 
WEINHEIM 
1 
62-68 
English 
WOS:000234621000006 
In previous work, we have demonstrated that the dangling amino group in amino-phosphane ligands increases the rate of Rh-catalyzed styrene hydroformylation as a function of the amino group basicity and of the distance between the P and N functions. We now report additional stereochemical and mechanistic insights resulting from new catalytic experiments performed with Rh-alpha-PN catalytic systems in the presence of D2O. In addition to the expected Do product, the formation of the P-D, aldehyde, PhCH(CH2D)CHO was observed in all cases by H-1 and C-13 NMR spectroscopy, indicating that H/D exchange occurs for the rhodium-hydride complex. Minor amounts of a beta-D-2 product, PhCH(CHD2)CHO, were also formed under certain conditions, demonstrating the reversibility of the olefin coordination step. The composition of the aldehyde mixture is slightly affected by the nature of the catalytic precursor or the PN ligand used. In the specific case of the alpha-PN ligand [alpha-PN = (S-Ar,S-C)-Ph2PCH-{o-C6H4Cl(Cr(CO)(3))}NHPh], in combination with the [RhCl(COD)](2) precatalyst, products PhCD(CH3)CHO (alpha-D-1) and PhCD(CH2D)CHO (alpha,beta-D-2) were also produced. This result suggests a reversible deprotonation assisted by an intramolecular H-bonding interaction between the dangling ammonium function and the carbonyl moiety. This isotopic exchange process decreases the asymmetric induction from 14 to 7 % ee when using the enantiopure version of this ligand. Aldehydes bearing a D atom on the formyl group, e.g. PhCH(CH3)CDO, were never observed. The latter observation excludes protonolysis of the rhodium-acyl intermediate as the aldehyde forming step. In addition, it also excludes a bimolecular reaction involving the rhodium-acyl and rhodium-hydride intermediates. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)