A vibrational investigation of several platinum and palladium cyclopentene complexes

Abstract

Complete vibrational assignments of the complexes [Cl 2Pt(C 5H 8)] 2, [Br 2Pt(C 5H 8)] 2, [Cl 2Pd(C 5H 8)] 2 and [Br 2Pd(C 5H 8)] 2 have been undertaken from 1500 to 70 cm −1. A reinvestigation of the cyclopentene spectrum was necessary and a new set of assignments is given. The v(CC) shifts down about 200 cm −1 for all the complexes and represents the largest shift observed for a Pd-mono-olefln complex. The shifts observed for the cyclopentene vibrations upon complexation as well as the fact that there are two platinum-carbon stretching frequencies but only one palladium-carbon stretching frequency is consistent with a strong π interaction in the platinum complexes leading to a ▪ bonding scheme and a predominantly σ interaction in the palladium complexes with the bonding scheme ▪ being the best description. It appears, however, that the total interaction, i.e. σ + π, is about the same in the complexes studied.