David L. Hughes

A novel {FeI–FeII–FeII–FeI} iron thiolate carbonyl assembly which electrocatalyses hydrogen evolution

A novel tetra-iron thiolate carbonyl assembly is described in which two dithiolate tetracarbonyl di-iron centres with a butterfly configuration of the {2Fe3S}-cores are fused by two bridging thiolates which form a central planar 2Fe2S unit and comprise the first example of a chain of four metal-metal bonded iron atoms supported by a bridging sulfur framework; the assembly electrocatalyses hydrogen evolution.

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.

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

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

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.

Copper complexes of the functionalised tripodal ligand tris(2-pyridyl)methylamine and its derivatives

The coordination chemistry of the new tripodal ligand tris(2-pyridyl)methylamine (tpm) with copper(I), copper(II) and zinc(II) has been investigated. The synthesis of tpm can readily be modified to access a variety of related tripodal ligands such as 2-(methylsulfanyl)-1,1-di(2-pyridyl)ethylamine (mde); in addition, the primary amine function can be derivatised to extend further the range of complexes obtained. tpm itself is a versatile ligand, showing three distinct coordination modes: bidentate (py, NH2), tridentate (2py, NH2) and tridentate (3py). Complexes of stoichiometries Cu(tpm)n (nxa0=xa01–3) have been obtained. The (2py, NH2) coordination mode is illustrated by the crystal structure of [Cu(tpm)2][BF4]2·Me2CO, whilst (3py) coordination is found in the crystal structures of [Cu(SO4)(tpm)(H2O)]·3H2O, [{Cu(tpm)}2Br3]Br·3MeOH and also the zinc complex [Zn(tpm)(H2O)3]2[Zn(H2O)6][SO4]3·3H2O. Amide derivatives of tpm give complexes of stoichiometry CuL2, and the crystal structures of [Cu(tpma)2][BF4]2 [tpmaxa0=xa0tris(2-pyridyl)methylacetamide] and [Cu(tpms)2]·8H2O {tpmsHxa0=xa04-oxo-4-[tris(2-pyridyl)methylamino]butanoic acid} have been determined. The crystal structure of the sulfate-bridged dimeric complex [{Cu(SO4)(mde)}2]·3H2O shows the mde ligand to be tridentate, with (2py, NH2) coordination.

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= 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, ngiving 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] ngives [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.

Synthesis, structure and chemistry of vanadium(IV) and vanadium(V) compounds with substituted hydrazido(1−) and hydrazido(2−) ligands

The reaction of [V(NS3)O] [NS3 n= N(CH2CH2S)3] with methylhydrazine gives the hydrazido(1−) vanadium(IV) complex [V(NS3)(NMeNH2)] 1, but reaction with various other compounds containing N–N groups results in formation of compounds containing substituted hydrazido(2−) ligands. Structures of 1, [V(NS3)(NNC5H10)] 2 and [V(NS3)(NNCPh2)] 3 are described.

Molybdenum and tungsten complexes of the N(CH2CH2S)33− (NS3) ligand with oxide, sulfide, diazenide, hydrazide and nitrosyl co-ligands

Reaction of [MoO2(acac)2] with N(CH2CH2SH)3 in CH2Cl2 gave an insoluble, red, diamagnetic complex formulated as [{MoO(NS3)}2] 1 [NS3xa0=xa0N(CH2CH2S)33−] together with a small amount of dark red, diamagnetic [{Mo(NS3)}2(μ-S)] 2. The linear, sulfur-bridged structure of 2 was confirmed by a crystal structure determination. With NH2NHR (Rxa0=xa0Me or Ph) in CH2Cl2, 1 gave soluble, red, diamagnetic diazenides [Mo(NS3)(N2R)] (Rxa0=xa0Me 3 or Ph 4) whereas with N2H4 it gave a dark brown, insoluble compound formulated as [{Mo(NS3)(N2H)}n] 5. The crystal structures of 3 and 4 have been obtained. Both 3 and 4 react with mineral acids HX (Xxa0=xa0BF4 or Cl) in CH2Cl2 to give the yellow-brown, diamagnetic hydrazides [Mo(NS3)(N2HR)]X (6, Rxa0=xa0Me, Xxa0=xa0BF4; 7, Rxa0=xa0Me, Xxa0=xa0Cl; 8, Rxa0=xa0Ph, Xxa0=xa0BF4), which deprotonate in more basic solvents to regenerate the parent complexes. Compound 3 reacted with [Me3O]BF4 to give yellow, diamagnetic [Mo(NS3)(N2Me2)]BF49 and with NO to give yellow, diamagnetic [Mo(NS3)(NO)] 10, whose crystal structure shows it to have a linear MoNO system. Reaction of N(CH2CH2SH)3 with [{Mo(μ-Br)Br(CO)4}2] and [WI2(CO)3(MeCN)2] gave the poorly soluble, diamagnetic complexes [{M(NS3)}2{μ-SCH2CH2N(CH2CH2SH)2-S}2] (Mxa0=xa0Mo 11 or W 12) whose structures have been established by determination of the crystal structure of 12.

Dinuclear iron and vanadium complexes of the N(CH2CH2S)33− ligand with bridging oxide, nitride or cyanide

Reaction of Et4N[Fe(NS3)(CO)] [NS3 is the ligand N(CH2CH2S)3] with trimethylamine oxide in MeCN gives (Et4N)2[{Fe(NS3)}2(μ-O)]·MeCN 1 with a symmetrical, bent Fe–O–Fe bridge while reaction of Et4N[V(NS3)Cl] with sodium azide gives Et4N[{V(NS3)}2(μ-N)]·MeCN 2 with an unprecedented linear symmetrical V–N–V bridge. Reaction of [V(NS3)(NH2NH2)] with R4NCN salts gives R4N[{V(NS3)}2(μ-CN)]·2MeCN (3, R = Et; 4, R = nnBu) while reaction of iron(III) acetylacetonate nand Et4NCN + Et4NOAc with N(SH)3 gives (Et4N)2[{Fe(NS3)}2(μ-CN)]·MeCN 5, which dissociates to Et4N[Fe(NS3)(CN)] 6 and an uncharacterised species in methanol. The above complexes were characterised by microanalyses, IR and magnetic measurements and where appropriate by Mossbauer and ESR spectra; X-ray structural determinations were carried out on 1, 2, 4 and 6.

Iron, cobalt and vanadium complexes of the N(CH2CH2S)33− ligand with chloride, azide, cyanide and carbonyl co-ligands

Reaction of [Fe(acac)3], Et4NCl and N(CH2CH2SH)3 (NS3H3) in MeCN gave [Et4N][FeCl(NS3)] 1 and metathesis the azide [Et4N][Fe(N3)(NS3)] 2, but reaction of [Fe(acac)3], R4NOAc and NS3H3 in MeCN gave [R4N][Fe4(NS3)3] (Rxa0=xa0Et, 3; Me, 4). Complex 1 is reduced under various conditions giving R′[Fe(NS3)] (R′xa0=xa0Et4N, 5; Tl, 6; N2H5, 7) which probably contain sulfur-bridged [{Fe(NS3)}n]n− anions. Under CO, 1 is reduced to the paramagnetic [Et4N][Fe(NS3)(CO)] 8 from which Tl[Fe(NS3)(CO)] 9 may be made by metathesis. Compound 8 reacts with metal chlorides in acetonitrile giving trinuclear [M{Fe(NS3)(CO)}2-S,S′] (Mxa0=xa0Fe, 10; Co, 11). The above complexes were characterised by microanalysis, IR and Mossbauer spectra and magnetic measurements; crystal structure determinations were carried out on 1, 2, 8, 10, and 11. The properties of the anions of 1 and 8 and of the hypothetical anions [Fe(NS3)]− and [Fe(N2)(NS3)]− have been investigated by density functional theory calculations. Compounds 8 and 10 have ν(CO) in the range 1960–1880 cm−1 and model aspects of carbon monoxide binding to the cofactor of nitrogenase. Related cyanide complexes [Et4N][M(NS3)(CN)] (Mxa0=xa0Co, 12; V, 13) have been characterised, 12 by X-ray analysis.