Showing papers by "Bryan M. Gatehouse published in 1981"

Coordination chemistry of methylmercury(II). Synthesis, hydrogen-1 NMR, and crystallographic studies of cationic complexes of MeHg(II) with ambidentate and polydentate ligands containing pyridyl and N-substituted imidazolyl donors and involving unusual coordination geometries

Abstract: Complexes [MeHgL]N03 (L = 4,4’,4’’-triethyL2,2':6’,2”-terpyridyl (Et3terpy), terpy, bis(2-pyridy1)methanes ((py)CH2's), (py)2CMe2, (py)2CEt2, tris(2-pyridyl)methane, several N-alkylimidazoles, N-(2-pyridyl)imidazole, and N-methyl-2-(2-pyridy1)imidazoles) are obtained from addition reactions in acetone. Proton magnetic resonance spectroscopy is used to deduce coordination behavior of potential uni- or polydentate ligands in methanol, indicating that Et3terpy, terpy, (py)2CH2's, and N-methyl-2-(2-pyridyl)imidazoles act as bidentates to give three-coordinate mercury, but (py)2CR2 (R = Me, Et) are present as unidentates. A linear relation is obtained between 2J(1H-199Hg) for [MeHgL]+ and protonation constants for L, where L = N-alkylimidazoles, and the relation is similar to that obtained previously for L = pyridines. The ambidentate ligand N-(2-pyridyl)imidazole binds to mercury via the imidazole ring. Crystalline [MeHg((py)2CH2)]N03 has (py)CH2 present as a bidentate ligand with “T-shape” coordination geometry based on a dominant C-Hg-N moiety [Hg-N = 2.16(1) A, C-Hg-N = 172 (1) and a weaker Hg-N’ bond [2.75(2) A]. Crystalline [MeHg(Et3terpy)]N03 has Et3terpy present as a tridentate ligand with MeHg(II) bonded strongly to the central nitrogen [2.26(2) A, C-Hg-N = 171(1) and weakly to the terminal nitrogens [2.51(2), 2.61(2) A]. Syntheses of new ligands containing pyridyl and N-methylimidazolyl donor groups are described.

Constituents of Endiandra species. I. Endiandric acid, a novel carboxylic acid from Endiandra introrsa (Lauraceae), and a derived lactone

Abstract: X-ray crystallographic analysis shows that endiandric acid and a derived lactone have the respective structures 2-(6'- phenyltetracyclo[5,4,2,03,13,010,12]trideca-4',8'-dien-11'-yl)acetic acid and 12-phenyl-3-oxapentacyclo[7,5,2,02,6,07,15,013,16]hexadecan-4-one.

The autoxidation of a chromium (II) porphyrin: synthesis and structural characterisation by X-ray crystallography of αβγδ-tetraphenyl-porphinato-oxochromium(IV)

Abstract: The reaction of dioxygen with αβγδ-tetraphenyl-porphinatochromium (II) in toluene proceeds in two stages; a µ-oxo-chromium(III) intermediate is formed initially and this then further reacts with dioxygen to give the title complex, the structure of which has been determined by X-ray crystallography.

Coordination chemistry of methylmercury(II). Complexes of aromatic nitrogen donor tripod ligands involving new coordination geometries for methylmercury(II)

Abstract: Complexes [MeHgL]N03 {L = diphenyl(2-pyridy1)methane (pyCHPh2), bis(2-pyridy1)phenylmethane [(py)2CHPh], and the tripod ligands tris(2-pyridy1)carbinol [(py)3COH] and bis(2-pyridyl)(N-methyl-2-imidazolyl)carbinol [(py)2(NMeIm)COH]} are obtained from addition reactions in acetone. The ligand (py)2CHPh is formed on reaction of (2-benzylpyridy1)lithium with 2-bromopyridine. 1H NMR spectra indicate that (py)2CHPh and (py)2(N-Me1m)COH are present as bidentates in methanol solutions of their complexes, with the latter coordinated via the imidazolyl ring and one pyridyl ring. Spectra are consistent with the presence of weak pi interactions between mercury and phenyl rings in the (py)CHPh2 and (py)2CHPh complexes and the uncoordinated pyridyl ring in the (py)2(N-Me1m)COH complex. In complexes [MeHgL]N03 (L = (py)3OH, (py)3CH) the ligands are present as tridentates in methanol. Crystalline [MeHgL]NO3 [L = (py)3OH, (py)2(N-MeIm)COH] have the tripod ligands coordinating as tridentates, with irregular coordination geometries based on a dominant C-Hg-N’ moiety [Hg-N’ = 2.28 (1) A, C-Hg-N’ = 150(1)O ((py)3COH) and 2.13(1) A, 170(0) ((py)2(N-MeIm)COH)] with weaker Hg-N,N” bonds [2.45(l), 2.53(1) ((py)3OH) and 2.66(l), 2.71(1) A ((py)2(N-MeIm)COH)]. For [MeHg((py)2(N-MeIm)COH)] the coordination geometry resembles a trigonal bipyramid lacking one equatorial donor and with axial direction C-Hg-N’.

Methyleneketenes and methylenecarbenes. XVI. The formation of Diphenylfuran-2-ones and 3-Phenylphthalide as minor products of the pyrolysis of diphenylmethyl propiolate

Abstract: The formation of a mixture of lactones as a minor product of the flash vacuum pyrolysis of diphenyl-methyl propiolate (1) has been investigated further. The diphenylfuran-2-ones (3), (4), and (5) are shown to be formed through an intramolecular insertion reaction of the methylenecarbene (2), formed from (1) at 640°, which leads to 5,5-diphenyl-furan-2(5H)- one (3) as the primary product. 3-Phenylphthalide (8) is apparently formed by intramolecular Diels-Alder addition of the C≡C bond of (1) to one phenyl ring which acts as the diene component, followed by loss of acetylene from an intermediate barrelene derivative (10). This is confirmed by a deuterium labelling experiment. 1-Phenyl-2-benzoxepin-3(1H)-one (7), considered at first as a possible intermediate in the pyrolysis of (1), is synthesized in six steps from 2-aminobenzophenone, and its X-ray structure determination is reported. On pyrolysis at 640°/0.07 mm (7) decarbonylates smoothly to give 2-vinylbenzophenone.

Palladium-mediated transfer of oxygen from carbonate ion to an organic ligand

Abstract: Reaction of some αβ-unsaturated ketones with palladium(II) chloride and sodium carbonate in tetra-hydrofuran (THF) gives acetylacetonate complexes; use of 18O-enriched carbonate shows that the reaction involves a highly unusual transfter of oxygen from carbonate ion to the organic ligand.

Methyleneketenes and methylenecarbenes. xvi. the formation of diphenylfuran-2-ones and 3-phenylphthalide as minor products of the pyrolysis of diphenylmethyl propiolate

Abstract: The formation of a mixture of lactones as a minor product of the flash vacuum pyrolysis of diphenyl-methyl propiolate (1) has been investigated further. The diphenylfuran-2-ones (3), (4), and (5) are shown to be formed through an intramolecular insertion reaction of the methylenecarbene (2), formed from (1) at 640°, which leads to 5,5-diphenyl-furan-2(5H)- one (3) as the primary product. 3-Phenylphthalide (8) is apparently formed by intramolecular Diels-Alder addition of the C≡C bond of (1) to one phenyl ring which acts as the diene component, followed by loss of acetylene from an intermediate barrelene derivative (10). This is confirmed by a deuterium labelling experiment. 1-Phenyl-2-benzoxepin-3(1H)-one (7), considered at first as a possible intermediate in the pyrolysis of (1), is synthesized in six steps from 2-aminobenzophenone, and its X-ray structure determination is reported. On pyrolysis at 640°/0.07 mm (7) decarbonylates smoothly to give 2-vinylbenzophenone.