Measurement of the trans influence in 1-platinacyclopent-4-ene-2,3-dione complexes : a proton, carbon-l 3, and phosphorus-31 nuclear magnetic resonance study

Abstract

The preparation of a series of 1-platinacyclopent-4-ene-2,3-dione complexes [[graphic omitted]H_v][L =AsPh₃, PPh₃, PEt₂Ph, PEt₃, PMePh₂, PMe₂Ph, P(OPh)₃, Ph₂PCH₂CH₂PPh₂(dppe), pyridine (py), 2,2′-bipyridine (bipy), or 1,10-phenanthroiine (phen)] is described. Measurement of the coupling ²J(PtH_v) between the vinylic proton. H_v, and platinum is expected to provide a measure of the trans influence of L. Instead an apparent trans-influence order AsPh₃∼ PPh₃ > P(OPh)₃ > PMePh₂ > PEt₂Ph > PMe₂Ph > PEt₃ > dppe > py is indicated, more or less the reverse of what is expected. Determination of ¹J(Pt¹³C_v) from ¹³C n.m.r. spectra of a selection of the complexes. however, has indicated the correct order. Phosphorus-31 n.m.r. spectra of the complexes L = PEt₃, PMePh₂ and PPh₃ indicate that the COCO half of the chelate has a considerably lower trans influence than the vinylic half.