Stereochemistry and Dynamic Properties of Square-Planar and Square-Pyramidal Cations of Bivalent Nickel, Palladium, and Platinum Containing the Enantiomers of (R*,R*)-(±)-and (R*,S*)-(±)-1-(methylphenylarsino)-2-(methylphenylphosphino)benzene

Abstract

Square-planar and square-pyramidal complexes of bivalent nickel, palladium, and platinum containing the enantiomers of (R1,R1)-(±)-and (R1,S1)-(±)-l-(methylphenylarsino)-2-(methylphenylphosphino)benzene (phas) have been prepared, and their behavior in solution has been investigated by and 31P NMR spectroscopy. All possible stereoisomers of the different species have been detected and unambiguously identified. The kinetically stable complex (+)-[Ni([H-(H1,-S1)]-phas)2](CIO4)2 is stereochemically nonrigid at 304 K in MeCN-rf3. The corresponding five-coordinate chloro species are also nonrigid but exhibit facile redistribution of the bidentates under ambient conditions. In the absence of free ligand the compounds [MCl(phas)2]Cl (where M = Pd and Pt) are kinetically stable with respect to redistribution of the bidentate ligands but undergo intramolecular cis-trans isomerization upon heating. Reaction of (R1,R1)-(±)-phas with (±)-[MCl2((R1,R1)-phas)] produces crystalline meso complexes only, although the corresponding racemic complexes are of comparable stability. The square-planar cations are more stable: the complexes [Pt(phas)2](PF6)2 do not undergo redistribution of bidentates in the presence of free ligand under ambient conditions. Show more