Sian C. Davies

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.

Copper(II) nitrite complexes of tripodal ligands derived from 1,1,1-tris(2-pyridyl)methylamine

Copper nitrite complexes of stoichiometric formulae [Cu(NO2)nL] (n=1 or 2), where L is a Schiff base or amide derivative of 1,1,1-tris(2-pyridyl)methylamine, have been prepared and characterized. The crystal structures of the mononuclear Schiff base complex [Cu(NO2)2(tpmbz)] [tpmbz=(C5H4N)3CN=CHC6H5], the nitrite-bridged dinuclear Schiff base complex [{Cu(NO2)(tpmsal)}2]·Et2O [tpmsalH=(C5H4N)3CN=CHC6H4OH-2] and the polymeric amide complex [{Cu(NO2)(tpms)}n]·nH2O [tpmsH=(C5H4N)3CNHC(O)CH2CH2CO2H] are reported. Copper nitrite complexes of new Schiff base and amide ligands derived from 1,1,1-tris(2-pyridyl)methylamine have been prepared and characterized, including three X-ray crystal structures. The complexes have general formulae [Cu(NO2)nL] (n=1 or 2) and the nitrito ligands are coordinated through one or both O atoms.

A di-iron dithiolate possessing structural elements of the carbonyl/cyanide sub-site of the H-centre of Fe-only hydrogenase

The synthesis and characterisation of the first {2Fe2S}-cluster bearing both CO and CN ligands is described; the iron atoms are linked by the bridging 1,3-propanedithiolate unit that has been identified in the crystallographic structure of the {2Fe2S} sub-unit of the H-centre of the all-iron hydrogenase from Desulfovibrio desulfuricans.

{2Fe3S} clusters related to the di-iron sub-site of the H-centre of all-iron hydrogenases

The first synthetic {2Fe3S} clusters structurally related to the sub-site of the H-centre of the all-iron hydrogenases are described: tripodal dithiolate thioether ligands allow the synthesis of di-iron pentacarbonyls with differential (2∶3) S ligation of the Fe atoms.

Synthesis and structure of a thiolate-bridged nickel–iron complex: towards a mimic of the active site of NiFe-hydrogenase

The reaction, under carbon monoxide, of [Fe(NS3)(CO)]– [NS3 = N(CH2CH2S)33–] with [NiCl2(dppe)] gives the structurally characterised dinuclear thiolate-bridged complex [{Fe(NS3)(CO)2-S,S′}NiCl(dppe)], which has structural features similar to those of the active site of NiFe-hydrogenase.

Crown thioether complexes of vanadium(II), vanadium(III) and vanadium(IV): X-ray crystal structure of [VCl3([9]aneS3)]

The synthesis of macrocyclic thioether complexes of vanadium(II), vanadium(III) and vadium(IV) and the X-ray structure of [VCl3([9]aneS3)] are described.

Coordination chemistry of a pyrazoline derived from 2,4-pentanedione bis(4-methylthiosemicarbazone). Crystal structure of the pyrazoline and evidence for metal-mediated ring opening

The heterocyclic structure of the pyrazoline obtained from reaction of 2,4-pentanedione with 4-methyl-3-thiosemicarbazide has been confirmed by X-ray crystallography. Reactions of the pyrazoline with CuII and ZnII have been probed by EPR and NMR spectroscopies respectively. The results suggest that the pyrazoline undergoes ring-opening back to the bis-thiosemicarbazone upon coordination to the transition metal, accompanied by oxidation of the central methylene group when the reactions are carried out under air.

Mononuclear, binuclear, trinuclear and tetranuclear iron complexes of the N(CH2CH2S)33− (NS3) ligand with nitrosyl co-ligands

Reaction of [Fe(acac)3], (NEt4)OAc and N(CH2CH2SH)3 in MeCN in the presence of NO gives (NEt4)[Fe(NS3)(NO)] (1) [where NS3 = N(CH2CH2S)3]. Complex 1 reacts with metal chloride solvates, giving insoluble compounds of stoichiometry MFe2(NO)2(NS3)2, probably having the structure [M{Fe(NS3)(NO)}2-S,S′] [M = Fe (2), Co (3), Ni (4), Cu (5)], the nitrosyl analogues of known structurally characterised carbonyl compounds. 1 also reacts with HBF4·Et2O, giving the tetranuclear complex [{Fe(NO)2{Fe(NS3)}-S,S′}2-S,S′] (6), which adds small molecules, L, giving the binuclear complexes [Fe(NO)2{Fe(NS3)(L)}-S,S′] [L = CO (7), CNMe (8), NO (9), CN− (10)]. Complexes 6–9 are more conveniently prepared by treatment of [Fe(NS3)(L)]− precursors with half an equivalent of [{Fe(NO)2}2(μ-I)2]. Reaction of (NEt4)[Co(NS3)(CN)] with half an equivalent of [{Fe(NO)2}2(μ-I)2] gives [Fe(NO)2{Co(NS3)(CN)}-S,S′] (11). Treatment of the [Fe(NS3)L] precursors used to make 7–9 with one equivalent of [{Fe(NO)2}2(μ-I)2] gives another series of complexes, [{Fe(NO)2I}-S{Fe(NS3)(L)}-S′,S″{Fe(NO)2}] [L = CO (12), CNMe (13), NO (14)]. Products were characterised by microanalyses, IR and Mossbauer spectra; X-ray crystal structure determinations were carried out on 1, 6, 7, 9, 10, 13 and 14. Magnetic measurements at room temperature showed evidence of spin pairing in all the polynuclear complexes.

Copper complexes of 1,3-bis(2-pyridyl)-1-thiapropane (bpt) andpyridine-2(1H)-thione. Crystal structure of[{Cu(µ-O2CMe)2(bpt)}2] and metal-promoted cleavage of bpt

The reactivity of the asymmetric thioether 1,3-bis(2-pyridyl)-1-thiapropane [1-(2-pyridyl)-2-(2-pyridylsulfanyl)ethane] (bpt) with copper-(I) and -(II) starting materials has been investigated. Reaction with [Cu(NCMe) 4 ]PF 6 in MeCN gave a cluster formulated as [Cu 4 (bpt) 6 ][PF 6 ] 4 , whilst reaction in tetrahydrofuran resulted in partial cleavage of bpt to give the mixed thionato–thioether complex [Cu 2 (SC 5 H 4 N)(bpt)]PF 6 [SC 5 H 4 NH = pyridine-2(1H)- thione]. Reaction with [Cu 2 (µ-O 2 CMe) 4 ] in MeOH gave the dimer [{Cu(µ-O 2 CMe) 2 (bpt)} 2 ], whose crystal structure shows that the bpt ligands are monodentate and co-ordinated via the N atom remote from the thioether. The compound bpt undergoes cleavage with other copper(II) salts such as Cu(BF 4 ) 2 , ultimately giving the hexameric copper(I) complex [Cu 6 (SC 5 H 4 N) 6 ]. The details of this reaction have been investigated. Reaction of SC 5 H 4 NH with Cu(NO 3 ) 2 in the presence of HNO 3 gave [Cu(NO 3 )(SC 5 H 4 NH) 2 ], which in turn reacted progressively with PPh 3 to give [Cu(NO 3 )(SC 5 H 4 NH) 2 (PPh 3 )] and the known complex [Cu(SC 5 H 4 NH) 2 (PPh 3 ) 2 ]NO 3 , whose crystal structure has been determined. Other complexes of SC 5 H 4 NH with copper(I) and a range of anions have been prepared, and the crystal structure of the dimer [Cu 2 (SC 5 H 4 NH) 6 ][MeC 6 H 4 SO 3 ] 2 is reported.

Vanadium complexes of theN(CH2CH2S)33-ligand with co-ligands relevant to nitrogen fixation processes

Vanadium(III) and vanadium(V) complexes of the tris(2-thiolatoethyl)amine ligand L 3- containing hydrazine, hydrazide, imide, ammine, cyanide and isocyanide ligands are synthesised; the complexes [V(NH 3 )L] and [V(NNMe 2 )L] have been structurally characterised.