J. Elaine Barclay

All-iron hydrogenase: synthesis, structure and properties of {2Fe3S}-assemblies related to the di-iron sub-site of the H-clusterElectronic supplementary information (ESI) available: crystal and structure refinement data for complexes 4a, 4b and 5a. See http://www.rsc.org/suppdata/dt/b2/b209690k/

Tripodal dithiolate thioether ligands MeC(CH2SH)2CH2SR (R = Me or Ph) provide a route to {2Fe3S}-complexes and syntheses are described. X-Ray crystal structures for two {2Fe3S}-pentacarbonyl derivatives and that for the first carbonyl cyanide are reported, together with temperature dependent 1H-NMR, Mossbauer, FTIR and redox potential data. The NMR data establish fluctionality associated with inversion at the thioether sulfur in the carbonyl complexes. The Mossbauer data affirm that the coordination environment of the two iron atoms in a dicyanide bridging carbonyl intermediate are differentiated. Bridging carbonyl intermediates have been structurally and spectroscopically identified in resting and CO inhibited forms of the sub-site of all-iron hydrogenases; the observation of a thermally unstable {2Fe3S}-bridging carbonyl intermediate is discussed in this context.

Virus‐Templated Silica Nanoparticles

An engineered variant of the plant virus, Cowpea mosaic virus, can template the controlled fabrication of silica nanoparticles of ≈30-nm diameter under environmentally benign conditions at ambient temperature and in aqueous solvent. This is the first reported mineralization of the external surface of a cage-like viral bionanoparticle.

Mössbauer and preparative studies of some iron(II) complexes of diphosphines

Analytical and Mossbauer spectral data show that Ph2PCH2CH2PPh2(dppe) forms adducts [FeCl2(dppe)] and [FeI2(dppe)], and that [FeCl2(dppe)2] does not exist. The phosphine 1,2-C6H4(PPh2)2(opdp) forms adducts FeX2(opdp)2, which exists in one form (high-spin, trans octahedral) for X = Cl, and in two isomeric forms for X = Br or I. One isomer for X = I is high-spin, trans octahedral, and the other is ionic low-spin, and five-co-ordinate. A comparison is made of these structures and of their Mossbauer spectra with those of derivatives of Me2PCH2CH2PMe2, Et2PCH2CH2PEt2, Pri2PCH2CH2Pri2, and Ph2PCH2PPh2.

Controlled immobilisation of active enzymes on the cowpea mosaic virus capsid

Immobilisation of horseradish peroxidase (HRP) and glucose oxidase (GOX) via covalent attachment of modified enzyme carbohydrate to the exterior of the cowpea mosaic virus (CPMV) capsid gave high retention of enzymatic activity. The number of enzymes bound per virus was determined to be about eleven for HRP and 2-3 for GOX. This illustrates that relatively large biomacromolecules can be readily coupled to the virus surface using simple conjugation strategies. Virus-biomacromolecule hybrids have great potential for uses in catalysis, diagnostic assays or biosensors.

Liquid Viruses by Nanoscale Engineering of Capsid Surfaces

Surface engineering of plant virus capsids via cationization (1) and stoichiometric coupling of a polymer surfactant coronal layer (2) produces a highly concentrated, solvent-free liquid virus at 28 °C. These ionic bionanoconstructs are viscoelastic, retain plant infectivity and can be dispersed in a range of organic solvents for aerosol delivery.

Preparation and crystal structures of trans-[Fe(NCMe)2(Ph2PCH2PPh2)2][FeI4]·2H2O and [Fe{Ph2P(O)CH2P(O)Ph2}3][I3]2

In an attempt to characterise definitively the species previously reported to be [Fe(NCMe)2(dppm)]I2, the structure of [Fe(NCMe)2(dppm)2][FeI4]·2H2O (dppm = Ph2PCH2PPh2) has been determined. Thus dppm is capable of forming bis(bidentate) complexes with iron(II). However, such materials are air-sensitive, and in attempting to reproduce the synthesis of the dihydrate the novel diphosphine dioxide complex [Fe(dppom)3][I3]2[dppom = Ph2P(O)CH2P(O)Ph2] was actually isolated and characterised by X-ray structure analysis. It is doubtful whether [Fe(NCMe)2(dppm)]I2 has ever been prepared.

Protonation of bis[1,2-bis(diethylphosphino)ethane]bis(dinitrogen)-molybdenum and -tungsten with fluoroboric acid–diethyl ether (1/1) in benzene; crystal and molecular structure of bis[1,2- bis(diethylphosphino)ethane]fluoro[hydrazido(2–)]tungsten tetrafluoroborate

The reaction of HBF4·Et2O with [W(N2)2(depe)2] in benzene can, depending upon the conditions, give rise to [WF(NNH2)(depe)2]BF4, [WF(NNH3)(depe)2][BF4]2, or [WH(F)(NNH2)(depe)2][BF4]2. The compounds are to some extent interconvertible. The structures have been completely elucidated using 31P and 15N n.m.r. spectroscopy, and the X-ray crystal structure of [WF(NNH2)(depe)2]BF4 has been determined. This reveals no unusual bond distances, but an extensive system of hydrogen bonding. The parallel reaction of [Mo(N2)2(depe)2] yields only one product, tentatively formulated as [Mo(BF4)(NNH2)(depe)2]BF4. The relevance of these observations to the mechanism of the protonation of complexed dinitrogen is discussed.

The first hetero-binuclear alkoxide of iron and vanadium: structural and spectroscopic features

Abstract The immediate reaction between [V2(μ-OPri)2(OPri)6] (A) and [Fe2(μ-I)2I2(HOPri)4] (B) in toluene/propan-2-ol gives the novel mixed-metal [FeI2(μ-OPri)2V(OPri)2(HOPri)] (C). Structural, spectroscopic and magnetochemical characterisation are all consistent with a non-oxo vanadium(IV)/high-spin iron(II) formulation; variable-temperature X-band EPR spectra reveal an S=1/2↔S=1 equilibrium involving the vanadium centres in propan-2-ol solution.

Lattice effects in the Mössbauer spectra of salts of [Fe4S4{S(CH2)nOH}4]2−. Crystal structures of [PPh4]2[Fe4S4{S(CH2)nOH}4] (n=2, 3 and 4)

Abstract The synthesis and spectroscopic (NMR, UV–Vis, Mossbauer) characterisation are reported for a series of mercaptoalcohol ligated cluster salts [Q]2[Fe4S4{S(CH2)nOH}4] (Q=NMe4, n=2, 3, 4, 6; Q=PPh4, n=2, 3, 4), together with the crystal structures of the three [PPh4]+ salts. The variation of the solid state Mossbauer parameters with ligand alkyl chain length, n, is discussed and related to crystallographic properties. In dimethyl sulfoxide frozen solution, all samples, independent of cation and ligand chain length, n, show the same quadrupole splitting in their Mossbauer spectrum.

Targeting synthetic analogues of the metallo-sulfur active sites of nickel enzymes capable of important catalysis

The nickel containing enzymes NiFe-hydrogenase, carbon monoxide dehydrogenase and acetyl-CoA synthase are able to catalyse environmentally, and potentially industrially, important reactions: hydrogen uptake; carbon dioxide/carbon monoxide interconversion; and incorporation of carbon monoxide to form acetyl-CoA, respectively. Progress toward the synthesis of nickel–iron complexes with structural features related to the active sites of these enzymes are described, together with the synthesis, properties and crystal structure of the first methylated-nickel–iron diheterometallic complex, [{Fe(NS3)(NO)-S}Ni(CH3)(dppe)] (NS3 = N(CH2CH2S)33−), relevant to a proposed mechanistic intermediate in the acetyl-CoA synthase mechanism.