NMR Studies on Zerovalent Metal π-Complexes of Dibenzylideneacetone. II. Structure and Pt–H Coupling in the Binuclear Platinum Complex

Abstract

Abstract The NMR analysis on the olefinic protons of the binuclear complex Pt2[(C6H5CH=CH)2CO]3 was conducted on the deuteriated compounds Pt2[(C6D5CH=CH)2CO]3, Pt2[(C6D5CD=CH)2CO]3, and Pt2[(C6D5CH=CD)2CO]3. Examination of the various 1H NMR parameters revealed the individual characteristics of the six coordinated olefins of three dibenzylideneacetone ligands with respect to the metal-olefin bonding and coordination geometry. The three ligands which triply bridge the two Pt atoms are composed of one s-cis,cis ligand which is distant from the Pt atoms and of two s-cis,trans ligands which are close to the Pt atoms. Asymmetry in the coordination, which is caused by the gliding of the olefinic double bond to the metal atom, becomes greater as the olefinic moiety approaches the metal atom more closely. The major transmission route of the Pt–olefinic proton coupling is attributable to metal to olefin π-back bonding.