Graham A. Pike

Stereochemistry of the 4-hydroxyisoleucine from Trigonella foenum-graecum

Abstract The stereochemistry of the 4-hydroxyisoleucine from fenugreek ( Trigonella foenum-graecum ) has been reinvestigated. The absolute configuration was shown to be (2 S ,3 R ,4 S by a combination of chemical, spectroscopic and X-ray crystallographic techniques.

Synthesis of pyridine-containing tetra-aza macrocycles: 3,7,11,17-tetra-azabicyclo[11.3.1]heptadeca-1(17),13,15-triene (L1), its 3,11-dibenzyl (L2) and 3,7,11-tribenzyl (L3) derivatives, and their nickel(II), copper(II), and zinc(II) complexes: crystal structures of L2·HCL and [Ni(L2)Cl]ClO4·H2O

Three pyridine-containing 14-membered-ring tetra-aza macrocycles, 3,7,11,17-tetra-azabicyclo-[11.3.l]heptadeca-1(17),13,15-triene (L1), its 3,11-dibenzyl (L2) and 3,7,11-tribenzyl (L3) derivatives, and their metal complexes with Ni2+, Cu2+, and Zn2+ have been prepared and characterised. The structure of [Ni(L2)Cl] ClO4·H2O has been established by X-ray crystallography. The Ni2+ ion co-ordination is approximately square pyramidal, with the macrocycle folded about an axis defined by the two N–CH2Ph groups, the secondary amine group co-ordinated at the apex of the square pyramid, and the chloride ion in the basal plane along with the other three N-donor atoms (Cl– in a trans position to the pyridine N atom). The crystal structure of L2·HCl is also reported.

Synthesis and co-ordination chemistry of 1-(2′,2″-bipyridyl-6′-ylmethyl)-1,4,7-triazacyclononane, a penta-azamacrocycle based on a triazamacrocycle with a single pendent co-ordinating bipyridyl group

New penta- and hexa-azamacrocycles have been synthesised, based on tri- and tetra-azamacrocycles functionalised with a single pendent co-ordinating 2,2′-bipyridyl-6-ylmethyl-arm; for the quinquedentate ligand 1-(2′,2″-bipyridyl-6′-ylmethyl)-1,4,7-triazacyclononane, the formation of a six-co-ordinate complex of Ni2+, and a seven-co-ordinate complex of Zn2+ has been established by X-ray crystallography, and a five-co-ordinate complex of Pd2+ established by 13C n.m.r. and fast atom bombardment mass spectroscopy.

Reinvestigation of the nickel phosphine catalysed electrochemical synthesis of poly(2,5-pyridine). X-Ray crystal structures of [Ni2Br2(µ-5-BrC5H3N-C2,N)2(PPh3)2] and [PtBr(5-BrC5H3N-C2)(PPh3)2]

Poly(2,5-pyridine) films have been deposited on glassy carbon, platinum and gold electrodes by the electroreduction of a novel binuclear nickel complex, trans(P,N)-bis[bromo(µ-5-bromopyridyl-C2,N)(triphenylphosphine) nickel(II)]. The synthesis, characterisation and electropolymerisation of this complex are described. The results from analytical and electrochemical investigations of poly(2,5-pyridine) are presented. The resultant poly(2,5-pyridine)-modified electrodes display electroactivity in their reduced state and co-ordinate nickel ions. The synthesis and electrochemistry of the analogous platinum and palladium complexes are also discussed.The X-ray crystal structures of the Ni and Pt complexes have been determined. The binuclear Ni complex contains Ni—(C5H4N)—Ni bridges, and the Ni atoms are also co-ordinated by one Br and one PPh3. The platinum complex is mononuclear with the Pt bound to the C2 of the pyridyl ring, to Br and to two trans PPh3 groups.

Reactivity of phenyliodonium bis(arylsulphonyl)methylides towards alkenes and alkynes: crystal structure of 9-phenylsulphonyl-1,2,3,4,4a,9a-hexahydro-1,4- methanofluorene

Thermal or photochemical reactions of phenyliodonium bis(arylsulphonyl)methylides with alkenes lead normally to gem-(arylsulphonyl)cyclopropanes. Norbornene and trans-stilbene, however, afford 1-(phenylsulphonyl)indane derivatives. The crystal structure of the title compound {R= 0.038 for 3 468 unique observed reflections [I/σ(I) 3.0]} confirmed the identity of the product with norbornene. Diarylacetylenes give 1-(arylsulphonyl)indenes. Thermal decomposition of the glides involves a new rearrangement, with formation of aryl arenethiosulphonates.

Generation of homochiral quaternary carbon centres from (vinylketenimine)tricarbonyliron(0) complexes

Abstract The first homochiral (vinylketenimine)tricarbonyliron(0) complexes have been formed. Nucleophilic attack occurs exclusively on their exo face and after an oxidative work-up homochiral β,γ-unsaturated carboxylic acids containing an α quaternary carbon centre are obtained.

1,1-Bis(phenylsulfonyl)-4-diethylamino-1,3-butadiene, a fully delocalized push-pull diene

Abstract The title compound is obtained from the reaction of phenyliodonium bis(phenylsulfonyl)methanide and diethylamine. Its structure and properties suggest that it is a fully delocalized system.

Formation of ethyl- and hydrido-iridium(III) complexes from the reaction of hydrated iridium(III) chloride with a pyridine-containing tetra-azamacrocycle in aqueous ethanolic solution. Crystal structure of trans-[IrCl(Et)L1][PF6]{L1= 3,7,11-trimethyl-3,7,11,17-tetra-aza-bicyclo[11.3.1]heptadeca-1(17),13,15-triene}

Reaction of a pyridine-containing tetra-azamacrocycle, 3,7,11-trimethyl-3,7,11,17-tetra-azabicyclo[11.3.1]heptadeca-1(17),13,15-triene, L1, with IrCl3·3H2O in refluxing aqueous ethanolic solution gives a mixture of hydrido-iridium(III) complexes, together with substantial amounts of trans-[IrCl(Et)L1]+, as shown by NMR measurements, FAB MS, and the single crystal X-ray structure of the ethyl complex.