Chiral <i>cis</i>-Platinum Acetylide Complexes via Diphosphine Ligand Exchange: Effect of the Ligand

Chiral, bidentate phosphine ligands (R,R-CHIRAPHOS, R-PROPHOS, S,S-BDPP, R,R-Me-DUPHOS, R,R-NORPHOS) react with trans-platinum acetylide complexes 1a and 1b, (Ph3P)2Pt(CCR)2 (R = TIPS, p-MeC6H4), via ligand exchange to generate chiral platinum acetylide complexes. The corresponding cis-platinum complexes are formed in all cases except for the reaction of 1b with S,S-BDPP, where the dimeric complex 4d′ is the product. Conversely, the reaction of 1a and 1b with the ligands S,S-DIOP, R-BINAP, and R-SYNPHOS fails to give the desired product in appreciable yield. Circular dichroism spectroscopy is used to examine the effect of the chiral ligand on the chiroptical properties of the platinum acetylide framework. X-ray crystallographic analyses of achiral complex 1a and chiral derivative 4e are reported.