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Starting from the versatile precursors, (Me3TACN)FeCl2 and [(Me3TACN)FeI(CO)-2](super +), a series of (Me3TACN)Fe(super II) derivatives with soft coligands are investigated. Cyanide and thiolates stabilize the binding of CO at the ferrous center.

An examination of nonlinear absorption and nonlinear refraction of solutions of a series of sulfur-rich molecules and anions confirmed that species containing large amounts of highly polarized sulfur would exhibit refracting properties in the absence of nonlinear absorption. Two structural families were identified, with particularly promising optical properties, including the Zn-S-SpH clusters and condensed dithiocarbonates. Results showed that high figures of merit can be achieved without the undesirable effects of linear absorption.

Electrophilic alkenes were reacted with ZnS(sub x)L(sub n) to yield dithiolenes Zn(S2C2R2)L(sub n). It was found that zinc polysulfido complexes, particularly those bearing triamine coligands, effect the dehydrogenative conversion of alkenes to dithiolenes. The rate-determining step was related to the addition of the alkene to the polysulfide ring to generate an alkanedithiolate. The dehydrogenation of the alkanedithiolate to the dithiolane proceeded at a rate that was independent of the ancillary amine ligand.

Research was conducted to examine the addition of alkenes to ReS4-. The well-behaved reactions were due mainly to the fact that they were cleanly reversible and that single adducts were generated. The reversible binding of alkene is extraordinary for an inorganic complex, particularly when the alkene is not directly bound to the metal. Results demonstrate that inorganic sulfides are fully capable of binding alkenes.

A soluble cubic cyanometalate framework that binds metal cations particularly Cs+ has been synthesized. The box-like cages (M(Cp*Rh(CN)3)4(Mo(CO)3)4)(super 3-) result from the reaction of (Cp*Rh(CN)3)(super -) with (eta(super 6)-C(sub 6)H(sub 3)Me(sub 3))Mo(CO)(sub 3) in the presence of K+ and Cs+. They were isolated as their Et4N+ salts with M = K+ and Cs+. Crystallographic analysis reveal that the M8(mu-CN)12 cages have alkali metal cations. They 12 external CO and 4 external C4Me5 ligands.

A study relating to the development of new routes to transition metal sulfides has resulted in the development of a convenient route that produces a reactive, sulfur-rich form of titanium sulfide that is quasimolecular or extractable into donor solvents. The sulfiding agent ZnS6(TMEDA) was used on solutions of TiCl4. The compound derived from their reaction is amorphous and reactive, which is consistent with a rapid polymerization of the formation of Ti(Sn)2.

Research was conducted to investigate the effect of ancillary ligands on the reactivity and structure of zinc polysulfido complexes. Proton NMR studies reveal that samples of the pentacoordinate complex, ZnS4(PMDETA), react with elemental sulfur to generate a substantial amount of a second polysulfido complex. Variable-temperature proton NMR spectroscopy showed the inversion of the stereochemistry at Zn in ZnS4(PMDETA). Results suggest that the third amine ligand enhanced the nucleophilicity of ZnS4(PMDETA).

The redox behaviour of the S-S bond is significant in several areas of chemistry. Organic disulfides are of interest as an alternative to inorganic sulfur in the cathodes, and they have a similar redox cycle to that involving alkali metal polysulfides. Several new binary carbon sulfide anions and molecules have been prepared, including the tricyclic species C(sub6)S(sub8), which is prepared via thermal decomposition of C(sub3)S(sub5)H(sub2).

Cp4Fe4(CO)4 is primarily produced from the thermolysis of a xylene solution of Cp2Fe2(CO)4 and PPh3, together with smaller amounts of (C5H4Ph)Cp3Fe4(CO)4 and Cp3Fe3(CO)3(PPh2). This was gleaned from a study of the functionalization of performed Cp-metal clusters. The main finding is that Cp4Fe4(CO)4 can be functionalized using various methods, such as alkylation and arylation by using organolithium reagents and deprotonation with lithium diisopropylamide and treatment with electrophiles to afford (C5H4X)Cp3Fe4(CO)4.

Related 52e-M3S4 cluster compounds such as [(C5Me5)3RhRu2S4(MeCN)]2+ (PF6)2 (M = Rh or Ir) were synthesized by the reaction of (C5Me5)2RuS4 with [(C5Me5)M(MeCN)3](PF6)2. The dicationic [(C5Me5)3RhRu2S4(MeCN)](SbF6)2 crystals were composed of an unsymmetrical RhRu2S4 core containing an isosceles triangle of metal atoms and one M-M bond. Furthermore, the (C5Me5)3RhRu2S4(MeCN)2+ cluster was composed of sulfur atoms in cationic clusters containing persulfido ligands which induced high reactivity.

The photoaddition of Fe2S2(CO)5L (L=CO,PPh3) to the fullerenes C60 and C70 was examined. The resulting iron-sulfido derivative C60(S2Fe2(CO)6)n, C60(S2Fe2(CO)5(PPh3))n, and C70(S2Fe2(CO)6)n were isolated by size exclusion chromatography and characterized by high performance liquid chromatography, FAB-MS, IR, and 13C nuclear magnetic resonance spectroscopy, as well as X-ray diffraction.

The H-cluster of [Fe–Fe] hydrogenase consists of a [4Fe]H subcluster linked by the sulfur of a cysteine residue to an organometallic [2Fe]H subcluster that utilizes terminal CO and CN ligands to each Fe along with a bridging CO and a bridging SCH2NHCH2S azadithiolate (adt) to catalyze proton reduction or hydrogen oxidation. Three Fe–S "maturase" proteins, HydE, HydF, and HydG, are responsible for the biosynthesis of the [2Fe]H subcluster and its incorporation into the hydrogenase enzyme to form this catalytically active H-cluster. We have proposed that HydG is a bifunctional enzyme that uses S-adenosylmethione (SAM) bound to a [4Fe–4S] cluster to lyse tyrosine via a transient 5′-deoxyadenosyl radical to produce CO and CN ligands to a unique cysteine-chelated Fe(II) that is linked to a second [4Fe–4S] cluster via the cysteine sulfur. In this "synthon model", after two cycles of tyrosine lysis, the product of HydG is completed: a [Fe(CN)(CO)2(cysteinate)]− organometallic unit that is vectored directly into the synthesis of the [2Fe]H sub-cluster. However our HydG-centric synthon model is not universally accepted, so further validation is important. In this Frontiers article, we discuss recent results using a synthetic "Syn-B" complex that donates [Fe(CN)(CO)2(cysteinate)]− units that match our proposed HydG product. Can Syn-B activate hydrogenase in the absence of HydG and its tyrosine substrate? If so, since Syn-B can be synthesized with specific magnetic nuclear isotopes and with chemical substitutions, its use could allow its enzymatic conversions on the route to the H-cluster to be monitored and modeled in fresh detail. [ABSTRACT FROM AUTHOR]

DNMR analysis of Me(C5H4)4Ru4S3(SMe)(super +), produced by the reaction of (MeC5H4)4Ru4S4 with MeO3SCF(MeOTf) reveals that Ru-Ru bonds exhibit mobility. Crystallographic analysis of (1Me)OTf reveals a distorted tetrahedron of Ru atoms with four Ru-Ru nonbonding and two Ru-Ru bonding contacts. NMR studies indicate that this structure is maintained in solution. The compound 1Me+ undergoes a 2e oxidation at 480 mV.

Reaction of ReOCl3(PPH3)2 with thienyllithium reagents in a THF slurry produces thiophene complexes of oxometal centers, Li(THF)(sub n)ReO(thienyl)4 having reduced d-electrons. The oxidation of Re(super V) occurs at moderate potentials. The resulting compound contains square pyramidal Re center with four thienyl ligands located in the equatorial plane at C-Re-O angle of 108-112 degree and C-Re-C angles of 81-85 degree as revealed by crystallographic analysis.

Four types of electrophilic reactions help convert the kinetic isomer of C3S(sub 5)(super 2-) into new carbon sulfides C3S8, C6S8, C6S10, and C6S12. These compounds help prepare new C-S-O compounds that exhibit increased solubility and help complete the characterization of the binary system. Reaction between (Bu4N)2(Zn(C3H5)2) and 4 equiv of SO2Cl2 leads to the formation of C3S5Cl2, which helps prepare nitrogen containing heterocycles. X-ray, NMR, MS and IR experiments help characterize all the synthetic compounds.

Two dicationic clusters are prepared and purified by ion exchange chromatography, and crystallographic studies are employed to characterize these compounds. Variable temperature 1H NMR study reveals the fluxional nature of the molecule, and it is due to mobile metal-metal bond. Internal Ir(super IV)/Ir(super III) self-exchange is responsible for this mobility. Cyclovoltammetry is employed to analyze redox properties of the clusters.

The process of internal redox forms cluster dynamics which display various properties such as diamagnetism of the specimens, sizeable conformational alterations in the influenced metals, and the influence of rapid and gradual exchange extents on the clusters. Mobility of metal-metal bonds results in the stereochemical flexibility of a group of RuIV clusters with different valencies. Lack of pairing to other alterations in metal ligation render this geometrical modification as rare. Clusters with similar conformations are examined.

A study was done on the reduction and protonation of eta4-thiophene ligands in (C6R6)Ru(C4R4S)2+. It was shown that the hydrogenolysis of thiophenes by sulfided metal catalysts proceed by thiophene coordination, electron transfer to the heterocycle, proton transfer to the ring and then C-S cleavage. These findings serve as the basis for further studies on the reactivity of partially hydrogenated thiophene ligands.

A study was done on base hydrolysis of (C5Me5)Rh(C4Me4S)2+ and the relationship of the reaction intermediate to the isomers of (C5Me5)Rh(C4Me4SO). It was shown that hydrolysis of the methylthiophene complex involves the use of OH- as the nucleophile. Thiophene accepts up to two equivalents of the hydroxide resulting in the net addition of O2- to the heterocycle. Further studies have demonstrated that nucleophilic attack at thiophene can occur at sulfur and nucleophile additions at sulfur can occur through initial attack at sulfur.

Photoelectron (PE) spectroscopy, cyclic voltammetry and other physical methods were employed in the investigation of the electronic structure of cyclopentadienyl clusters. These clusters included (eta-C5H4 super i Pr MoS)4, (eta-C5H4 super i Pr MoSe)4, (eta-C5H4Me CrS)4, (eta-C5H4Me CrSe)4, (eta-C5H4Me TiS)4, (eta-C5H4Me VS)4, (eta-C5H5 CrO)4 and (eta-C5H4Me CrO)4. Results revealed that all the clusters have the highest molecular orbital metal based. Moreover, a molecular ion state ordering of (super 2)T(sub 2) < (super 2)E < (super 2)A(sub 1) is favored.

Two types of ruthenium selenide Ru2 (Se2)-based core structures are interconverted by reduction/oxidation procedures, and their structures assigned on the basis of spectroscopic and electrochemical investigations. The oxidized product is obtained in ((MeCp)Ru(PPh3))2 (Se2)2+ while the reduced product is ((MeCp)Ru(PPh3)2)Se4, which is comparable to the compound ((Me4)Ru(PPh3))2(mu-S2). Se2-based complexes such as (C5H4R)Ru(PPh3)2 and (CpRu(PPh3))2Se2+ are analyzed for the production process and large range of bonding modes.

The complex ((C5Me5)Rh)3(eta4,eta1-C4Me4S)2 (1) was obtained from the thermal decomposition of (C5Me5)Rh(eta4-C4Me4S) and characterized by elemental analysis and 1H and 13C NMR spectroscopy. Single-crystal X-ray diffraction showed the structure of ((C5Me4Et)Rh(eta4, eta1-C4Me4S))2Rh(C5Me4Et) to consist of a pair of (C5Me4Et)Rh(eta4-C4Me4S) ligands binded by sulfur atoms to a central (C5Me4Et)Rh unit. The decomposition of 1 followed a first-order kinetics.

Research describes a new class of diiron dithiolates, capable of dihydrogen oxidation, diferrous species, exhibiting higher oxidation states and hydrogen binding capabilities. Results reveal that the diferrous species form the basis for the [Fe(sub)2(SR)(sub)2(CNMe)(sub)7](sup)2+ active site of the iron hydrogenases.

Research has been conducted on the ruthenium sulfide clusters. The characterization of these cluster has been carried out crystallographically and the results demonstrate that the clusters ate structurally and stoichiometrically related.

Research was conducted to examine a novel synthesis of tetrathioxalate and its transformation to C3S5(super 2-) and C4S6(super 2-). The objective of the study was to gain insight into the detoxification of organochlorine compounds which may be influenced by the conversion of chlorocarbons to chlorine-free products. Results indicate that the new synthesis is an intermediate in the formation of two essential thioanions, C3S5(super 2-) and C4S6(super 2-).

Redox reactions, substitutions, and metalations are reported for the iron carbido sulfide [Fe6C(CO)14(S)]2– ([1]2–). Dianion [1]2– oxidized to [Fe6C(CO)16(S)]0 ([2]0) upon treatment with of [Fe(C5H5)2]BF4 or HBF4 (H2 formation) under an atmosphere of CO. Reaction of [2]0 with tBuNC gave [Fe6C(S)(CO)13(tBuNC)5], consisting of Fe5C(CO)13 and [Fe(tBuNC)5]2+ subunits linked by a µ3‐S2–. The Fe7CS cluster [Fe7C(CO)17(S)]2– formed upon treatment of (Ph4P)2[1] with Fe(benzylideneacetone)(CO)3. The Fe7 species is an edge‐fused cluster with [Fe6C(CO)10(µ‐CO)4] and Fe(CO)3 subunits joined by µ3‐S and two Fe–Fe bonds. The analogous reaction using Mo(CO)4(norbornadiene) gave [MoFe6C(CO)18(S)]2–. In this cluster, the Mo center is located in the octahedral subunit. Treatment of [1]2– with SO2 afforded [Fe6C(S)(SO2)(CO)13]2–. This cluster features an Fe6C core decorated with µ3‐S and µ2‐SO2 ligands. These experiments were undertaken in an effort to connect organometallic clusters to FeMoco. [ABSTRACT FROM AUTHOR]

The enzyme [FeFe]-hydrogenase (HydA1) contains a unique 6-iron cofactor, the H-cluster, that has unusual ligands to an Fe-Fe binuclear subcluster: CN-, CO, and an azadithiolate (adt) ligand that provides 2 S bridges between the 2 Fe atoms. In cells, the H-cluster is assembled by a collection of 3 maturases: HydE and HydF, whose roles aren't fully understood, and HydG, which has been shown to construct a [Fe(Cys)(CO)2(CN)] organometallic precursor to the binuclear cluster. Here, we report the in vitro assembly of the H-cluster in the absence of HydG, which is functionally replaced by adding a synthetic [Fe(Cys)(CO)2(CN)] carrier in the maturation reaction. The synthetic carrier and the HydG-generated analog exhibit similar infrared spectra. The carrier allows HydG-free maturation to HydA1, whose activity matches that of the native enzyme. Maturation with 13CN-containing carrier affords 13CN-labeled enzyme as verified by electron paramagnetic resonance (EPR)/electron nuclear double-resonance spectra. This synthetic surrogate approach complements existing biochemical strategies and greatly facilitates the understanding of pathways involved in the assembly of the H-cluster. As an immediate demonstration, we clarify that Cys is not the source of the carbon and nitrogen atoms in the adt ligand using pulse EPR to target the magnetic couplings introduced via a 13C3,15N-Cys-labeled synthetic carrier. Parallel mass-spectrometry experiments show that the Cys backbone is converted to pyruvate, consistent with a cysteine role in donating S in forming the adt bridge. This mechanistic scenario is confirmed via maturation with a seleno-Cys carrier to form HydA1-Se, where the incorporation of Se was characterized by extended X-ray absorption fine structure spectroscopy. [ABSTRACT FROM AUTHOR]