Neil Burford

Definitive identification of cysteine and glutathione complexes of bismuth by mass spectrometry: assessing the biochemical fate of bismuth pharmaceutical agents

Solutions containing BiCl3, bismuth subsalicylate or Bi(NO3)3 with L-cysteine, DL-homocysteine, D-methionine or glutathione have been examined by electrospray mass spectrometry. Prominent peaks are assigned to bismuth complexes of these biomolecules and provide insight towards understanding the bioactivity of bismuth compounds.

Coordination complexes of Ph₃Sb²⁺ and Ph₃Bi²⁺: beyond pnictonium cations.

The syntheses of salts containing ligand-stabilized Ph3Sb(2+) and Ph3Bi(2+) dications have been realized by in situ formation of Ph3Pn(OTf)2 (Pn=Sb or Bi) and subsequent reaction with OPPh3, dmap and bipy. The solid-state structures demonstrate diversity imposed by the steric demands and nature of the ligands. The synthetic method has the potential for broad application enabling widespread development of the coordination chemistry for Pn(V) acceptors.

Paramagnetic liquids: the preparation and characterisation of the thermally stable radical ButCNSNS· and its quantitative photochemically symmetry allowed rearrangement to a second stable radical ButCNSSN

The new thermally stable paramagnetic liquid 5-t-butyl-1,3,2,4-dithiadiazolyl has been isolated in the dark and quantitatively photochemically isomerised to the paramagnetic liquid 5-t-butyl-2,3,1,4-dithiadiazolyl (non-systematic numbering for ease of comparison).

The high yield preparation, characterisation, and gas phase structure of the thermally stable CF3CSNSCCF3·, 4,5-bis(trifluoromethyl)-1,3,2-dithiazolyl and the X-ray crystal structure of benzo-1,3,2-dithiazolyl

The very thermally stable, but photochemically sensitive radical, 4,5-bis(trifluoromethyl)-1,3,2-dithiazolyl has been prepared, isolated, and fully characterised including a gas phase structure, and found to be paramagnetic in the liquid state at room temperature; the X-ray structure of benzo-1,3,2-dithiazolyl has been obtained for comparison.

Coordination complexes of bismuth(III) involving organic ligands with pnictogen or chalcogen donors

Publisher Summary The chapter presents an overview of the structural diversity demonstrated by complexes of bismuth(III) with organic-based ligands involving the elements of Groups 15 (pnictogens) and 16 (chalcogens) as donor sites, recognizing the potential for tailoring structure and reactivity by manipulation of the organic moiety. Although most complexes of bismuth obey standard valence guidelines, the high and variable coordination numbers accessible to bismuth are responsible for interesting and unpredictable structural arrangements. The formulas of well-defined bismuth compounds are presented to outline the type and extent of characterization data available for each, enabling assessment of the significance and relevance of the observations regarding synthesis and reactivity. Some of the structural features are described in detail to illustrate the novelty or generality of a particular arrangement. A diverse coordination chemistry is emerging for bismuth(III) made possible by a spacious and flexible coordination environment, allowing for coordination numbers in excess of 9.

New Synthetic Procedures to Catena-Phosphorus Cations: Preparation and Dissociation of the First cyclo-Phosphino-halophosphonium Salts

Chlorination of 1,2,3,4-tetracyclohexyl-cyclo-tetraphosphine (2) by PhICl(2) or PCl(5) in the presence of Me(3)SiOTf or GaCl(3) provides a stepwise approach to salts of the first cyclo-phosphino-chlorophosphonium cations [Cy(4)P(4)Cl](+) ([19](+)) and [Cy(4)P(4)Cl(2)](2+) ([20](2+)). The analogous iodo derivative [Cy(4)P(4)I](+) ([17](+)) is obtained as the tetraiodogallate salt from reaction of 2 with I(2) in the presence of GaI(3). Reactions of the dication [20](2+) with PMe(3) or dmpe effect a dissociation of the cyclic framework resulting in the formation of salts containing [Me(3)PPCyPCyPMe(3)](2+) ([27](2+)), [dmpeCyP](2+) ([29](2+)), and [dmpeCyPCyP](2+) ([30](2+)), respectively. The new cations represent phosphine complexes of the [PCy](2+) and [P(2)Cy(2)](2+) cationic fragments from [20](2+), demonstrating the coordinate nature of the phosphinophosphonium bonds in cyclo-phosphino-halophosphonium cations. The compounds have been characterized by NMR spectroscopy, single crystal X-ray crystallography, and Raman spectroscopy.

31P NMR Studies Demonstrating the Assembly of catena-Phosphorus Frameworks from Chlorophosphinochlorophosphonium Cations

New examples of chlorophosphinochlorophosphonium (4) and chlorophosphinodichlorophosphonium (5) cations have been prepared and spectroscopically characterized. These bifunctional phosphinophosphonium cations offer a new approach to the development of phosphinophosphonium frameworks using reductive coupling reactions and have been exploited as synthons to assemble larger catena-phosphorus cations. The reactions of 4 and 5 with stibine reducing agents have been studied using (31)P NMR spectroscopy and have been shown to produce a variety of new and known frameworks in a facile manner, depending on the reducing agent selection and the stoichiometry of the reaction. New derivatives of frameworks containing three, four, and five phosphorus atoms have been identified by (31)P NMR spectroscopy. Crystals of the [GaCl(4)](-) salt of the five-membered dication 11((i)Pr) have been isolated from the reaction of [4((i)Pr)][GaCl(4)] with SbBu(3), and the solid state structural features and solution state dynamics are comprehensively described in the context of (31)P{(1)H} NMR spectroscopic observations.

Nuclear magnetic resonance spectroscopic characterisation and the crystal and molecular structures of Ph3PSe·AlCl3and Ph3PSe·AlCl3: a classification of the co-ordinative bonding modes of the phosphine chalcogenides

A series of compounds with the general formula R3PE·AlCl3(R = Ph or NMe2, E = S or Se) has been examined by n.m.r. spectroscopy as a contribution toward the characterisation of the P–E bond and of the co-ordinate bond. Two derivatives, Ph3PS·AlCl3 and Ph3PSe·AlCl3, have been studied by X-ray crystallography. [Crystal data: C18H15AlCl3PS, monoclinic, space group, P21/n, a= 9.710(2), b= 9.464(1), c= 21.893(5)A, β= 95.15(2)°Z= 4, R= 0.042; C18H15AlCl3PSe, triclinic, space group, Pa= 8.967(2), b= 12.626(4), c= 18.242(4)A, α= 84.83(2), β= 89.02(2), γ= 85.67(2)°, Z= 4, R= 0.044.] In contrast to the oxygen analogues, the sulphur and selenium derivatives exhibit bent geometries [P–S–Al 109.62(8), P–Se–Al (mean)= 107.0(1)°]. The structures are maintained in solution, as demonstrated by the 27Al n.m.r. spectra. The 31P and 13C n.m.r. spectra are informative of the changes associated with adduct formation, and show the oxygen derivatives (E = O) to be unique. Disruption of the P–E π interaction due to adduct formation is more dramatic for the sulphur and selenium than for the oxygen derivatives. The extensive information available in the literature is re-evaluated in the light of the present results, and a classification for the co-ordinative bonding modes of the phosphine chalcogenides is proposed.

Prototypical Phosphine Complexes of Antimony(III)

Complexes of the generic formula [Cln(PR3)mSb]((3-n)+) (n = 1, 2, 3, or 4 and m = 1 or 2) have been prepared featuring [ClSb](2+), [Cl2Sb](1+), Cl3Sb, or [Cl4Sb](1-) as acceptors with one or two phosphine ligands {PMe3, PPh3, PCy3 (Cy = C6H11)}. The solid-state structures of the complexes reveal foundational features that define the coordination chemistry of a lone pair bearing stibine acceptor site. The experimental observations are interpreted with dispersion-corrected density functional theory calculations to develop an understanding of the bonding and structural diversity.

Coordination of arsine ligands as a general synthetic approach to rare examples of arsenic-antimony and arsenic-bismuth bonds.

Tertiary arsines form stable adducts with trichlorostibine and with cationic antimony and bismuth centers, defining coordination chemistry as a general synthetic approach to the formation of rare As-Sb and As-Bi bonds. A series of compounds containing As-Sb and As-Bi bonds define key milestones in the systematic development of interpnictogen compounds.