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Copper dithiocarbamate complexes have been known for ca. 120 years and find relevance in biology and medicine, especially as anticancer agents and applications in materials science as a single-source precursor (SSPs) to nanoscale copper sulfides. Dithiocarbamates support Cu(I), Cu(II) and Cu(III) and show a rich and diverse coordination chemistry. Homoleptic [Cu(S2CNR2)2] are most common, being known for hundreds of substituents. All contain a Cu(II) centre, being either monomeric (distorted square planar) or dimeric (distorted trigonal bipyramidal) in the solid state, the latter being held together by intermolecular C···S interactions. Their d9 electronic configuration renders them paramagnetic and thus readily detected by electron paramagnetic resonance (EPR) spectroscopy. Reaction with a range of oxidants affords d8 Cu(III) complexes, [Cu(S2CNR2)2][X], in which copper remains in a square-planar geometry, but Cu–S bonds shorten by ca. 0.1 Å. These show a wide range of different structural motifs in the solid-state, varying with changes in anion and dithiocarbamate substituents. Cu(I) complexes, [Cu(S2CNR2)2]−, are (briefly) accessible in an electrochemical cell, and the only stable example is recently reported [Cu(S2CNH2)2][NH4]·H2O. Others readily lose a dithiocarbamate and the d10 centres can either be trapped with other coordinating ligands, especially phosphines, or form clusters with tetrahedral [Cu(μ3-S2CNR2)]4 being most common. Over the past decade, a wide range of Cu(I) dithiocarbamate clusters have been prepared and structurally characterised with nuclearities of 3–28, especially exciting being those with interstitial hydride and/or acetylide co-ligands. A range of mixed-valence Cu(I)–Cu(II) and Cu(II)–Cu(III) complexes are known, many of which show novel physical properties, and one Cu(I)–Cu(II)–Cu(III) species has been reported. Copper dithiocarbamates have been widely used as SSPs to nanoscale copper sulfides, allowing control over the phase, particle size and morphology of nanomaterials, and thus giving access to materials with tuneable physical properties. The identification of copper in a range of neurological diseases and the use of disulfiram as a drug for over 50 years makes understanding of the biological formation and action of [Cu(S2CNEt2)2] especially important. Furthermore, the finding that it and related Cu(II) dithiocarbamates are active anticancer agents has pushed them to the fore in studies of metal-based biomedicines.

Diaryldithiocarbamate complexes, [Fe(S2CNAr2)3], have been prepared and their structure, reactivity, and thermal degradation to afford iron sulfide nanomaterials have been investigated. The addition of three equivalents of LiS2CNAr2 to FeCl2·4H2O in water-air affords dark red [Fe(S2CNAr2)3] in high yields. All show magnetic measurements consistent with a predominantly high-spin electronic arrangement at room temperature. The molecular structure of [FeS2C(N-p-MeOC6H4)23] reveals the expected distorted octahedral geometry, but Fe-S distances are more consistent with a low-spin electronic configuration, likely a result of the low temperature (120 K) of the data collection. The thermal stability of [FeS2C(N-p-MeC6H4)23] has been investigated. TGA shows that it begins to decompose at a significantly lower temperature (ca. 160 °C) than previously observed for [Fe(S2CNEt2)3], and this is further lowered (to ca. 100 °C) in oleylamine. The decomposition of [FeS2C(N-p-MeC6H4)23] in oleylamine, via either a heat-up or hot injection process, affords nanoparticles of Fe3S4 (greigite), while in contrast, dry heating at 450 °C affords FeS (troilite) as large agglomerates.

While many [FeFe]-hydrogenase biomimetics are effective proton-reduction catalysts, few are active for H2 oxidation, and examples containing both a pendant amine group, able to act as a proton relay, and a second redox center, both essential features of the enzymes, are rare. Here we report the preparation and oxidation chemistry of two ferrocene-functionalized amino-diphosphines (PCNCP), (CH2PR2)2NCH2Fc (R = Ph (1), Cy (2)), and their ethylenedithiolate (edt) diiron complexes, [Fe2(CO)4(μ-edt)κ2-(R2PCH2)2NCH2Fc] (R = Ph (3), Cy (4)). Their crystallographic characterization shows that PCNCP occupies an apical–basal position. CV responses are slightly R-dependent, showing for 3 and 4 in three separate oxidative processes assigned to successive one-electron oxidation of the diiron core (quasireversible), appended Fc (reversible), and the amine–diiron moiety (irreversible), as confirmed by IR and UV–Vis spectroelectrochemical studies supported by Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TDDFT) calculations. The first oxidation results in a structural rearrangement of the Fe(PNP)(CO) unit and the formation of a semi-bridging carbonyl. Slow protonation of 3 with HBF4∙Et2O affords the corresponding N-protonated cation in acetone, whilst μ-hydride products dominate for both 3 and 4 in CD2Cl2. A preliminary H2 oxidation study was carried out with 3, and while there was some evidence of activity, it was much lower than reported for alkyl-functionalized PCNPC diiron derivatives.

The reactivity of the benzenedithiolate (bdt)-bridged complex [Fe2(CO)6(µ-bdt)] with arsine, stibine and phosphine ligands has been studied. The new mono- and disubstituted complexes [Fe2(CO)5(EPh3)(µ-bdt)] (E = As, 1; E = Sb 3) and [Fe2(CO)4(EPh3)2(µ-bdt)] (E = As, 2; E = Sb, 4) and the previously reported [Fe2(CO)4(PPh2H)2(µ-bdt)] (5) have been prepared by Me3NO-initiated carbonyl substitution reactions of [Fe2(CO)6(µ-bdt)] with appropriate ligands at 80 °C. Spectroscopic and single-crystal X-ray diffraction studies reveal that in all cases the introduced ligands occupy apical coordination site(s) lying trans to the iron–iron bond. Their electrochemistry has been probed by cyclic voltammetry and selected complexes have been tested as proton reduction catalysts. Monosubstituted complexes 1 and 3 show two irreversible reductions at ca. −1.7 V and −2.0 V, respectively, relative to Fc+/Fc, while the disubstituted complexes 2 and 5 show a single irreversible reduction at ca. −2.2 V and −1.84 V, respectively. Complexes 1, 3 and 5 can catalyse electrocatalytic proton reduction in the presence of either p-toluene sulfonic acid (TsOH) or trifluoroacetic acid (CF3CO2H).

Addition of the bulky redox-active diphosphine 1,8-bis(diphenylphosphino)naphthalene (dppn) to [Fe2(CO)6(µ-edt)] (1) (edt = 1,2-ethanedithiolate) affords [Fe2(CO)4(κ2-dppn)(µ-edt)] (3) as the major product, together with small amounts of a P–C bond cleavage product [Fe2(CO)5κ1-PPh2(1-C10H7)(µ-edt)] (2). The redox properties of 3 have been examined by cyclic voltammetry and it has been tested as a proton-reduction catalyst. It undergoes a reversible reduction at E1/2 = −2.18 V and exhibits two overlapping reversible oxidations at E1/2 = −0.08 V and E1/2 = 0.04 V. DFT calculations show that while the Highest Occupied Molecular Orbital (HOMO) is metal-centred (Fe–Fe σ-bonding), the Lowest Unoccupied Molecular Orbital (LUMO) is primarily ligand-based, but also contains an antibonding Fe–Fe contribution, highlighting the redox-active nature of the diphosphine. It is readily protonated upon addition of strong acids and catalyzes the electrochemical reduction of protons at Ep = −2.00 V in the presence of CF3CO2H. The catalytic current indicates that it is one of the most efficient diiron electrocatalysts for the reduction of protons, albeit operating at quite a negative potential.

Reactions of the anti-alcohol drug disulfiram (tetraethylthiuram disulphide = Et 4 TDS) with low valent triosmium complexes are described. Room temperature reaction with [Os 3 (CO) 10 (MeCN) 2 ], affords three new open polynuclear clusters, [Os 3 (CO) 10 (S 2 CNEt 2 ) 2 ] ( 1 ), [Os 4 (CO) 12 {µ 3 -η 1 (C), κ 2 (O,O)-CO 2 }(S 2 CNEt 2 )(µ-S 2 CNEt 2 )] ( 2 ) and [Os 3 (CO) 9 (µ 3 -SCNEt 2 ){µ-SC(O)NEt 2 }] ( 3 ) together with the known mononuclear complex cis- [Os(CO) 2 (S 2 CNEt 2 ) 2 ] ( 4 ). All result from oxidative-addition of disulfiram to the triosmium centre, with 2 also capturing CO 2 , while cluster 3 has undergone further C–S bond scission and partial oxidation of one of the generated thiocarboxamide ligands. With [Os 3 (CO) 10 (µ-H) 2 ], complexes 1 and 4 are also formed along with previously reported [Os 3 (CO) 10 (µ-S 2 CNEt 2 )(µ-H)] ( 5 ), [Os 3 (CO) 9 (µ 3 -S 2 CNEt 2 )(µ-H)] ( 6 ), and the new cluster, [Os 3 (CO) 9 (µ-S 2 CNEt 2 )(µ-H)] ( 8 ), which is an isomer of 6 . The product distribution is rationalized by completing pathways following the oxidative-addition of disulfiram. Thus, reductive-elimination of H 2 affords 1 , which in turn converts to 4 , while reductive-elimination of the (unstable) dithiocarbamic acid, Et 2 NCS 2 H, leads to the formation of 5 , which can further lose CO to afford isomers 6 and 8 . Heating disulfiram with [Os 3 (CO) 12 ] at 110 °C predominantly affords 4 , together with smaller amounts of the novel trithiocarbamate complex, cis- [Os(CO) 2 (S 2 CNEt 2 )(S 3 CNEt 2 )] ( 9 ). All the compounds have been characterized by elemental analysis, IR and 1 H NMR spectroscopy, together with single crystal X-ray diffraction analysis of six molecules.

AbstractThe electrochemistry of dppm-bridged dithiolate complexes [M2(CO)4(μ-dppm)μ-S(CH2)nS] (M = Fe, Ru; n = 2, 3) has been studied by cyclic voltammetry. The diiron complexes show similar electrochemical responses in CH2Cl2 but differ significantly in MeCN, while the diruthenium complexes change only slightly with changes in the dithiolate backbone and solvent. Proton-reduction studies in MeCN with HBF4·Et2O as the proton source show that all are active catalysts for proton reduction in their singly reduced state. An additional catalytic event is observed for all, resulting from their partial protonation giving [M2(CO)4(μ-dppm)μ-S(CH2)nS(μ-H)][BF4]. The diiron complexes show better long-term stability to acids, the diruthenium complexes degrading at high acid concentrations.Graphical AbstractThe electrochemical response of dithiolate complexes [M2(CO)4(μ-dppm)μ-S(CH2)nS] (M = Fe, Ru; n = 2, 3) has been investigated in different solvents as well as they have been tested as electrocatalysts for the reduction of protons to hydrogen.

AbstractMicrowave irradiation of 1,6-diynes, RC≡C(CH2)4C≡CR, with Fe(CO)5 in dimethylether leads to the facile and clean formation of cyclopentadienone complexes [η4-C4R2C(O)C4H8Fe(CO)3] in good yields resulting from a [2 + 2 + 1] cycloaddition. The molecular structures of three examples (R = Ph, 2,4-F2C6H3, 4-MeOC6H4) have been obtained. The addition of HBF4 leads to the clean and reversible formation of cationic hydroxycyclopentadienyl complexes [η5-C4R2C(OH)C4H8Fe(CO)3][BF4]. Sequential addition of hydroxide and acid has also been carried out in an attempt to prepare hydroxycyclopentadienyl–hydride complexes. These were largely unsuccessful but in one case a Shvo-type complex with a bridging hydride was detected by 1H NMR spectroscopy. Reasons for the differing behaviour of [η4-C4(SiMe3)2C(O)C4H8Fe(CO)3] and the related aryl-functionalised derivatives are considered. Graphical AbstractMicrowave irradiation of 1,6-diynes, RC≡C(CH2)4C≡CR, with Fe(CO)5 gives cyclopentadienone complexes [η4-C4R2C(O)C4H8Fe(CO)3], the molecular structures of three (R = Ph, 2,4-F2C6H3, 4-MeOC6H4) being carried out. Sequential addition of hydroxide and acid was carried out in an attempt to prepare hydroxycyclopentadienyl–hydride complexes, and while largely unsuccessful, in one case a Shvo-type complex with a bridging hydride was suggested by 1H NMR spectroscopy.

Diaryldithiocarbamate complexes, [Fe(S[sub.2]CNAr[sub.2])[sub.3]], have been prepared and their structure, reactivity, and thermal degradation to afford iron sulfide nanomaterials have been investigated. The addition of three equivalents of LiS[sub.2]CNAr[sub.2] to FeCl[sub.2]·4H[sub.2]O in water-air affords dark red [Fe(S[sub.2]CNAr[sub.2])[sub.3]] in high yields. All show magnetic measurements consistent with a predominantly high-spin electronic arrangement at room temperature. The molecular structure of [FeS[sub.2]C(N-p-MeOC[sub.6]H[sub.4])[sub.2][sub.3]] reveals the expected distorted octahedral geometry, but Fe-S distances are more consistent with a low-spin electronic configuration, likely a result of the low temperature (120 K) of the data collection. The thermal stability of [FeS[sub.2]C(N-p-MeC[sub.6]H[sub.4])[sub.2][sub.3]] has been investigated. TGA shows that it begins to decompose at a significantly lower temperature (ca. 160 °C) than previously observed for [Fe(S[sub.2]CNEt[sub.2])[sub.3]], and this is further lowered (to ca. 100 °C) in oleylamine. The decomposition of [FeS[sub.2]C(N-p-MeC[sub.6]H[sub.4])[sub.2][sub.3]] in oleylamine, via either a heat-up or hot injection process, affords nanoparticles of Fe[sub.3]S[sub.4] (greigite), while in contrast, dry heating at 450 °C affords FeS (troilite) as large agglomerates.

AbstractReactions of a series of diphosphines with Fe2(CO)6(µ-edt) (1) and Fe2(CO)6(µ-tdt) (2) have been explored, the nature of the products being highly dependent upon the diphosphine. Reaction of 1 with bis(diphenylphosphino)methane (dppm) in acetonitrile at 82 °C affords monosubstituted Fe2(CO)5(κ1-dppm)(µ-edt) (3) in which the phosphine occupies an apical site and disubstituted Fe2(CO)4(µ-dppm)(µ-edt) (4) in which the phosphine is acting as a bridging ligand, while a similar reaction of 2 with dppm yields only Fe2(CO)4(µ-dppm)(µ-tdt) (5). In contrast, 1 and 2 react with 1,2-bis(diphenylphosphino)ethane (dppe) to form the chelate complex Fe2(CO)4(κ2-dppe)(µ-edt) (7) and Fe2(CO)4(κ2-dppe)(µ-tdt) (8), respectively; in both the diphosphine binds in an apical–basal fashion to a single iron atom. A second product of the dppe reaction with 1 is tetranuclear [Fe2(CO)5(µ-edt)]2(κ1,κ1-dppe) (6) in which the diphosphine again occupies apical sites. Similar reactions of 1 and 2 with 1,1′-bis(diphenylphosphino)ferrocene (dppf) give single products, namely Fe2(CO)5(κ1-dppf)(µ-edt) (9) and Fe2(CO)5(κ1-dppf)(µ-tdt) (10), respectively, which are structurally similar to 3. All seven complexes have been characterized by a combination of analytical and spectroscopic data, together with single-crystal X-ray diffraction analysis for 3, 7, 9 and 10.Graphical AbstractReactivity of Fe2(CO)6(µ-edt) and Fe2(CO)6(µ-tdt) toward a series of diphosphines has been investigated from which a number of different kinds of products are isolated and characterized.