A Study of the Dimer of Ethylene Platinous Chloride by Proton Magnetic Resonance

Abstract

The protoll magnetic resonance line of the powdered ethylene platinous chloride dimer complcx has a second moment of 13.68+1 gauss2 a t 77'I< and an over-all line width of 11.15f 0.4gauss. Measi~ren~ents a t various temperatures between 77' and 329" I< show that both second moment and line width decrease slightly with temperature. The mean separation of the doublet observed a t 77'I< is found to be 4 . 8 0 f 0.3 g.The results are interpreted in terms of a distorted ethylene molecule whose interproton distances correspond to an intermediate struct~rre between ethylene and an ethane in a cis configuration but with two of the cis protons removed. 'This is consistent with earlier studies of the Raman spectrum. The a-type bond formed between a metal d orbital and an ethylene a" orbital is also consistent with the lack of rotation of ethylene a t elevated temperatures.Available results frorn high-resolution proton resonance studies of ethylene complexed to metal atorns in solutions is discussed.The bonding of ethylene to the metal in a series of olefin complexes of platinum and palladium I1 has been treated by Chatt and Duncanson (1). A satisfactory explanation of the infrared and dielectric studies has been achieved in terms of a u and a bond. The ethylene is co-ordinated to a dspz metal orbital by use of the ethylene a electrons in a u bond. I t has also been suggested that a donation of charge from a metal d orbital into the ethylene a* orbital fornls a a-type bond which also contributes to the stability of the conzpleu.Further studies of these compounds by X-ray diffraction of the solid have confirmed the suggestions of the earlier workers. Studies of Zeise's salt ( 2 ) , ethylene palladiu~n chloride dimer (3), and styrene palladium chloride (4) show that the ethylene is a t one corner of the square planar co~nplex with the ~netnl a t the center. Resolution was adequate to show the scattering froin the carbon electrolls indicating that the carbon atoms are .an equal distance above and below the plane of the complex. In the dimers, such as [PdC12C2H4]2, there are two chlorine atoms which act as a bridge between the two palladium atoms; the ethylene in the cli~ner units conlplexes in the trans positions.The infrared studies of the C-C stretching mode region indicate the loss of a center of symlnetry by the olefin since a \veal<ly allowed infrared absorption occurs in ethylene platinous chloride. The transition moment of this band in the 1500 cm-I region is very low ancl it is not observed in Zeise's salt. I t is thus evident that the syln~netry of ethylene is very little changed by co-ordination. Well-defined C-H stretching frequencies a t 3068, 3034, and 3010 cm-I call be assigned to the three olefin stretching modes in the spectrum of K[C3H6PtC13] . H 2 0 , a propylene complex.Since the X-ray studies are unable to detect the proton positioils and a certain loss of syill~netry of ethylene is suggested by infrared measurements, the present study of proton resonance in the powdered solid ethylene platinous c...

Olefin and acetylene complexes of platinum and palladium

“…77 The nuclear magnetic resonance spectrum of polycrystalline [PtCl2(C2H4)]2 did not show any evidence for the rotation of the olefin about the platinum-olefin bond, although there was evidence for a rocking motion perpendicular to the platinum-olefin bond and "wagging" about the carboncarbon double-bond axis. 78 The nuclear magnetic resonance data also suggested that the olefinic bond was lengthened and the hydrogen atoms were bent out of the olefinic bond plane away from the platinum atom, giving a geometry similar to that which exists in the excited states of ethylene.46…”

The Use of the Chemical Shift Parameter for Study of Intramolecular Hydrogen Bonds

“…Corrections have been made to eliminate ring current effects. 9 The change in chemical shift so obtained is correlated with the corresponding change in the stretching frequency of the -O-H band. Many of the infrared measurements are taken from the work of A. W. Baker and co-workers,12 some were checked using a Perkin-Elmer 21 instrument, and others arc measurements made by us.…”

A Carbon-13 and Deuterium NMR Investigation of Solid Platinum−Ethylene Complexes: Zeise's Salt and Pt(η2-C2H4)(PPh3)2

“…The dynamics of the ethylene ligand in solid samples of Zeise's salt and Zeise's dimer (Scheme C) have been studied by 1 H NMR. Through a second moment analysis 32 of the 1 H NMR spectra of Zeise's dimer, Reeves concluded that the ethylene ligand undergoes a rocking motion about the axis perpendicular to the C,C bond . In a later 1 H NMR study of Zeise's salt, Maričić et al concluded that, besides the rocking motion, the ethylene ligand also undergoes large-amplitude oscillations about the axis parallel to the C,C bond.…”