Showing papers by "Edward W. Abel published in 1980"

Complexes of trimethylplatinum(IV) halides with dithio- and diselenoethers, dimethyl disulphide, and dimethyl diselenide

Abstract: Trimethylplatinum(IV) halides react with MeE(CH2)nEMe, E = S or Se, n= 2 or 3, to give mononuclear species [PtXMe3{MeE(CH2)n EMe}], X = Cl, Br or I. Under similar conditions the ligands L–L = MeECH2EMe, MeECH(Me)EMe, and MeEEMe, E = S or Se, give dinuclear complexes [(PtXMe3)2(L–L)] in which the S or Se donor ligand bridges the metal atoms. Structural asignments are based on 1H n.m.r. solution studies.

Nuclear magnetic resonance investigations of configurational nonrigidity in dinuclear platinum(IV) complexes. Part 2. Pyramidal inversion and novel fluxional rearrangements in [(PtXMe3)2(MeEEMe)](E = S or Se) complexes

Abstract: Dinuclear complexes of the type DL-[(PtXMe3)2(MeSCH2SeMe)] containing both PtIV–S and PtIV–Se bonds have been isolated. Detailed variable-temperature n.m.r. studies have established the existence of ligand ring reversal, pyramidal inversion of both S and Se atoms, ligand commutation (switching) between Pt atom pairs and scrambling of the platinum methyl environments which is considered to be a consequence of rapid ligand commutation producing a highly non-rigid seven-co-ordinate PtIV intermediate. Accurate energy barriers for these non-dissociative dynamic processes have been computed. Despite the probable non-synchronous nature of the S/Se double inversion, the spectra are shown to be sensitive only to Se inversion.

A nuclear magnetic resonance study of sulphur and selenium inversion in complexes of trimethylplatinum(IV) halides with dithio- and diselenoethers

Abstract: Dynamic n.m.r studies have yielded accurate energy data for S and Se pyramidal inversion in complexes of type [PtXMe3(L–L)][X = Cl, Br, or I; L–L = MeE(CH2)nEMe, E = S or Se, n= 2 or 3]. The mechanism of the inversion process and the effects of atomic mass, ring size, and nature of halogen on the barrier energies are discussed.

Determination of the separate barrier energies for six-membered ligand ring reversal and pyramidal sulphur inversion in complexes of palladium(II) and platinum(II). A dynamic hydrogen-1 and carbon-13 nuclear magnetic resonance study

Abstract: The series of complexes trans-[MX2{[graphic omitted]H2)5}2](M = Pd; X = Cl, Br, or I; M = Pt; X = Cl) have been synthesised and, by accurate analysis of their variable-temperature 1H and 13C n.m.r. spectra using total band-shape fitting methods, energy barriers for ligand ring reversal and for sulphur inversion have been separated and calculated for the first time. The barriers to ring reversal in the complexes are similar to those already known for the unco-ordinated ligand, whereas those for sulphur inversion are also similar to values known for analogous non-cyclic ligand complexes. The power of 13C dynamic n.m.r. spectral analysis was demonstrated by the fact that no simplifications in the conformational analyses were needed in order to account for the 13C spectral line changes. This was in marked contrast to the 1H spectra, which, in order for their analyses to be possible, had to be attributed to the conformations of either six-membered heterocyclic ring rather than to total conformational structures of the complexes.

η-TETRAPHENYLPHOSPHOLYL AND η-TETRAPHENYLARSOLYL DERIVATIVES OF MANGANESE, RHENIUM, AND IRON

Abstract: The tetraphenyl-phospholyl and -arsolyl complexes of manganese and rhenium [M(CO)5(σ-EC4Ph4)](E = P or As, M = Mn or Re) lose carbon monoxide on heating to yield the corresponding η-phospholyl and η-arsolyl complexes [M(CO)3(η-EC4Ph4)]. These products are also obtained by loss of carbon monoxide from the dimers [{Mn(CO)4(EC4Ph4)}2], the action of Ph4C4E–EC4Ph4(E = P or As) upon [Mn2(CO)10], and by the action of tetraphenyl-1-trimethylsilylarsole upon [Mn(CO)5Cl]. Triphenylphosphine, diphenylacetylene, and the nitrosyl cation all displaced one carbonyl group from the complex [Mn(CO)3(η-AsC4Ph4)]. Prolonged heating of the iron complexes [Fe(CO)2(η-C5H5)(σ-EC4Ph4)](E = P or As) caused loss of carbon monoxide and production of the corresponding phospha- and arsa-ferrocenes [Fe(η-C5H6)(η-EC4Ph4)].