Neil Bricklebank

The structure of triphenylphosphorus–dibromine, the first crystallographically characterised bromophosphorane, a compound which has the novel four-coordinate molecular Ph3P–Br–Br geometry

Triphenylphosphorus–dibromine is shown by X-ray crystallography to have a four-coordinate Ph3P–Br–Br ‘spoke’ structure and is isostructural with Ph3P–I–I and Ph3As–I–I; thus forcing us to question the conventional belief that tertiary-organo group 15 adducts with dihalogens have either pentacoordinate R3EX2 or ionic [R3EX]+X– structures in the solid state.

Modification of the solid state structures of dithiadiazolyl radicals: crystal structure of p-iodophenyl-1,2,3,5-dithiadiazolyl

Abstract The solid state structure of the 1,2,3,5-dithiadiazolyl p -IC 6 H 4 CNSSN ( 3 ) is described. The molecules associate in dimer pairs, across an inversion centre, in an unusual trans -cofacial manner. The separation between the heterocyclic rings is 3.121 A. The intradimer sulfur contacts (3.696 A) are larger than those observed in dithiadiazolyls that associate in the more usual cis -cofacial manner. Individual p -IC 6 H 4 CNSSN molecules are linked into zigzag chains through weak I⋯S interactions (3.82 A); each half of a [ p -IC 6 H 4 CNSSN] 2 dimer is a member of separate chains that run in opposite directions.

The isolation from diethyl ether of ionic [(Me2N)3PI]I and [(CH2CHCH2)2PhPI]I, and the crystallographically characterised molecular ‘spoke’ structure PhMe2PI2

Ten new compounds of stoichiometry R3PI2[R3=(o-MeOC6H4)3, (o-MeOC6H4)2Ph, (o-MeOC6H4)Ph2, (p-FC6H4)2Ph, (p-FC6H4)Ph2, (p-CH2CHC6H4)Ph2, (CH2CHCH2)2Ph, (C6H11)Ph2, (PhCH2CH2)3 or (Me2N)3] have been prepared by the direct reaction of PR3 and I2 in diethyl ether solution. The compounds have been characterised by Raman and solid-state 31P-{H} magic angle spinning (MAS) and solution NMR spectroscopy. Solid-state 31P-{H} MAS NMR studies indicate that the predominant solid-state species is the molecular ‘spoke’ structure R3P–I–I; however, in some cases a minor peak was also assignable to the ionic species, [R3PI]I. Additionally, solid-state 31P-{H} MAS NMR studies of (Me2N)3PI2 and (CH2CHCH2)2PhPI2 indicate that, in contrast to all other compounds of stoichiometry R3PI2 prepared in diethyl ether, they are exclusively ionic, [R3PI]I. The crystal structure of PhMe2PI2 shows it to have the molecular ‘spoke’ geometry, PhMe2P–I–I, d(I–I)= 3.408 A, previously observed for Ph3PI2, in agreement with solid-state 31P-{H} MAS NMR results.

Water-soluble gold nanoparticles stabilized with cationic phosphonium thiolate ligands

Attachment of cationic groups to the surface of gold nanoparticles (AuNPs) is an attractive proposition for facilitating mitochondria-targeted therapeutics and diagnostics. With this in mind we have prepared and characterised AuNPs functionalised with phosphonium groups derived from either triarylphosphoniopropylthiosulfate zwitterions or ω-thioacetylpropyl(triphenyl)phosphonium salts; organophosphonium cations display remarkable lipophilicity and are readily taken up by cells and are concentrated in the mitochondria. The phosphonium-functionalised AuNPs can be dispersed in water and biological media. Transmission Electron Microscopy reveals the formation of spherical particles with diameters in the range 3–5 nm. The presence of the phosphonioalkylthiolate ligands on the surface of the AuNPs is confirmed by XPS, LDI-TOF-MS, TOF-SIMS and 31P NMR spectroscopy. The phosphonium-AuNPs display excellent stability and preliminary studies indicate that the phosphonioalkylthiolate ligands are slowly oxidised over a period of months to the corresponding phosphonioalkylsulfonate species with a concomitant increase in the particle size, and particle size distribution, of the AuNPs.

Diiodophosphoranes. Synthesis and structure in the solid state and in solution

Nineteen diiodophosphoranes, R3PI2(R3= Ph3, substituted triaryl, mixed arylalkyl, or trialkyl), the vast majority of which have previously not been reported, are described. Their 31P{H} NMR data indicate an ionic [R3PI]I structure in CDCl3 solution, in keeping with results of other solution studies of a limited number of dihalogenophosphoranes, but solid-state 31P-{H} magic angle spinning NMR data for R3PI2(R3= Ph3, PhMe2 or Me3) indicate a molecular four-co-ordinate R3P–I–I structure, strongly suggesting that this is the common structure for diiodophosphoranes, and not the five-co-ordinate trigonalbipyramidal structure of conventional wisdom.

Spontaneous Magnetisation at 36k in a Sulfur-Nitrogen Radical

Abstract The radical p-NCC6F4CNSSN, 1, can be obtained in two different phases depending upon sublimation conditions. The α-phase, lα, crystallises in space group P 1, and the molecules are related through an inversion centre. The β- phase, lβ crystallises in the orthorhombic space group Fdd2 and the molecules are not related by an inversion centre. The latter shows a sharp rise in the magnetic susceptibility at 36K which is accompanied by an out-of-phase component in the a.c. susceptibility. Heat capacity measurements show a distinct peak at 35.5K indicative of the long range ordering of the magnetic moments. The magnetic ordering of the compound is also confirmed by neutron diffraction experiments. Magnetisation isotherms indicate the presence of a small residual moment that saturates below 100 Oe. Extrapolation of the residual moment at T= 0K gives a value for the spontaneous magnetisation of 1.5×l0−3 μB/molecule. The behaviour is interpreted in terms of weak ferromagnetism.

The first solid state paramagnetic 1,2,3,5-dithiadiazolyl radical; X-ray crystal structure of [p-NCC6F4CNSSN]˙

The solid state structure of the fluorinated 1,2,3,5-dithiadiazolyl radical [p-NCC6F4[graphic omitted]]· is reported; it is the first dithiadiazolyl radical to retain its paramagnetic character in the solid state.

Reaction of Me2SBr2 and Prn3PI2 with tin metal powder; a novel route to metal thioether complexes and the first tin(IV) phosphine complex containing iodide ligands

Tin metal powder reacts readily with both Me2SBr2 and Prn3PI2 in diethyl ether under ambient conditions, producing the novel SnBr4(SMe2)2, which contains both cis and trans isomers within the unit cell, and the first complex of stoichiometry Snl4(PR3)2 to be isolated: both complexes have been crystallographically characterised.

Tertiary phosphine adducts of mixed halogens, R3PlBr; synthesis and structure in the solid state and solution

The first extensive solid-state study of compounds of formula R3PIBr [R3=(p-CIC6H4)3, Ph3, Ph2Prn, Ph2Me, PhMe2 or Bun3] has been made, most having not previously been described. The crystal structure of Ph3PIBr shows it to be a surprisingly complex molecule containing dual occupancy of the halogen sites within the unit cell, existing predominantly as Ph3PIBr. Nevertheless, it is clear that the molecule is a further example of the four-co-ordinate molecular ‘spoke’ structure, Ph3P–X–X, previously established for Ph3PX2(X = Br or I) and Ph3ASI2. X-Ray powder diffraction studies on analytically pure samples of Ph3PIBr prepared the same way indicated that subtly different compounds are formed containing varying degrees of occupancy for the two sites described above; however, the molecule is always predominantly Ph3P–I–Br. Raman spectroscopic studies on all the R3PIBr compounds illustrate the dominance of the P–I bond in the spectrum; however, in some cases a minor peak assignable to v(P–Br) was noted, in agreement with the crystallographic studies. Solution 31P-{H} NMR studies in CDCI3 indicate complete ionisation of the compounds R3P–I–Br to [R3PI]Br; no evidence for the corresponding [R3PBr]I was observed. Results for the compound Bun3PIBr were inconclusive however. This suggests halogen exchange occurs in solution, in agreement with the findings of previous workers.

Synthesis and structural characterisation of R3AsX2 compounds (R = Me, Ph, p-FC6H4 or p-MeOC6H4; X2= Br2, I2 or IBr); dependency of structure on R, X and the solvent of preparation

Compounds of stoichiometry R3AsX2(R =p-MeOC6H4, Ph or Me; X = Br or I; R =p-FC6H4, X = I), R3AsI4(R =p-FC6H4 or Ph) and Ph3AsIBr have been synthesised in anhydrous diethyl ether and characterised by elemental analysis and Raman spectroscopy. Single-crystal X-ray diffraction studies of Ph3AsBr2 showed it to possess a molecular trigonal-bipyramidal structure, in contrast to Ph3AsI2 which adopts the molecular four-co-ordinate structure Ph3As-I-I. Both Me3AsI2 and Me3AsBr2 have the molecular four-co-ordinate structure, Me3As-X-X, thus illustrating that the structure of R3AsX2 compounds isolated from diethyl ether is dependent on R and X. The structure of Ph3AsIBr also revealed four-co-ordinate molecular geometry in contrast to Ph3AsBr2. The compound Ph3AsIBr showed no dual occupancy of the halogen sites, and the heavier halogen is bound directly to the arsenic. The X-ray powder diffraction patterns of Ph3AsX2(X2= Br2, I2 or IBr) have been recorded and are compared. Solution studies on R3AsI2(R =p-FC6H4, Ph or p-MeOC6H4) again showed the sensitivity of these molecules to the nature of R. For example, (p-FC6H4)3AsI2 was not formed in any solvent employed; instead, equimolar quantities of (p-FC6H4)3AsI4 and (p-FC6H4)3As were isolated; Ph3AsI2 was only formed in non-polar solvents upon dropwise addition of a light petroleum solution of I2 to a saturated solution of Ph3As in the same solvent. The compound (p-MeOC6H4)3AsI2 was the quantitative product from the direct reaction of the tertiary arsine with I2 in diethyl ether. Its stability constant in CCl4 is approximately 2.5 times greater than that calculated for Ph3AsI2.