34. "Chiral Palladium(0) trans-Stilbene Complexes: Synthesis, Structure, and Oxidative Addition of Phenyl Iodide," Tim J. Brunker, Natalia F. Blank, Jillian R. Moncarz, Corina Scriban, Brian J. Anderson, David S. Glueck,Lev N. Zakharov, James A. Golen, Roger D. Sommer, Christopher D. Incarvito, Arnold L. Rheingold, Organometallics 2005, 24, 2730-2746.
Abstract The chiral Pd(0) trans-stilbene complexes Pd(diphos*)(trans-stilbene) (diphos* = (R,R)-Me-Duphos, (R,R)-Et-Duphos, (R,R)-i-Pr-Duphos, (R,R)-Me-BPE, (S,S)-Me-FerroLANE, (S,S)-Me-DuXantphos, (S,S)-Et-FerroTANE, (R,S)-CyPF-t-Bu, (R,S)-PPF-t-Bu, (R,S)-BoPhoz) and Ni((R,R)-Me-Duphos)(trans-stilbene) were prepared by NaBH(OMe)3 reduction of the corresponding M(diphos*)Cl2 compounds in the presence of trans-stilbene. The rate of oxidative addition of phenyl iodide to the stilbene complexes, which gave Pd(diphos*)(Ph)(I), depended on the ligand (larger for increased ligand bite angles and reduced steric bulk) and was markedly faster than oxidative addition to mixtures of Pd(dba)2 and diphos*. The complexes Pd(diphos*)(Ph)(I) were prepared independently by treatment of PdL2(Ph)(I) (L2 = TMEDA or (PPh3)2) with diphos*. Oxidative addition of PhI to the complexes M((R,R)-Me-Duphos)(trans-stilbene) occurred in the rate order Pd > Ni >> Pt. Several complexes Pd(diphos*)Cl2, Pd(diphos*)(trans-stilbene), and Pd(diphos*)(Ph)(I), as well as some analogous Ni compounds, were structurally characterized by X-ray crystallography.