Thiocarbonyl Ligand Research Articles

Theoretical Study of the Hydrolysis of Iron–Sulfur–Nitrosyl Complex [Fe(NO)2(SCH2)2

The mechanisms of hydrolysis of a model iron–sulfur–nitrosyl complex (ISNC) [Fe(NO)2(SCH2)2]+ 1 with thioformaldehyde ligands have been studied using the density functional theory and polarizable continuum model of water. Quantum chemical calculations employed the TPSSH and M06 functionals and def2-TZVP basis set and took into account interactions with water medium. Hydrolysis of 1 was found to be an exothermic process with small activation energy whereas exchange of NO for H2O is thermodynamically unfavorable. The calculations have predicted lower activation barrier for the associative mechanism with concerted replacement of SCH2 by H2O than for dissociative mechanism with homolytic bond cleavage of the Fe–S coordination bond in water. The mechanism of hydrolysis that involves participation of OH– was found to be less probable at pH 7. The calculation results show that ISNC 1 is of {Fe1+(NO•)2}9 type and retains its tetrahedral structure that is typical for crystals of ISNC with thiocarbonyl ligands.

Advances in Transition Metal Seleno- and Tellurocarbonyl Chemistry.

In contrast to the ubiquity of transition-metal carbonyl, and (to a lesser extent) thiocarbonyl complexes, transition-metal complexes of carbon monoselenide Ln MCSe and monotelluride Ln MCTe remain scarce. The last few years, however, have seen notable steps towards expanding this chemistry, specifically with regards to new systematic studies on homologous sets of chalcocarbonyl complexes Ln MCE (E=O, S, Se, Te), the first reports of new bi- and polynuclear CSe and CTe bridging complexes and a confluence with metal carbido chemistry. Herein the properties, syntheses and reactions of these rare but fundamentally intriguing compounds are discussed.

Synthesis and Systematic Structural Analysis of Cationic Half-Sandwich Ruthenium Chalcogenocarbonyl Complexes.

Although the chemistry of transition-metal complexes with carbonyl (CO) and thiocarbonyl (CS) ligands has been well developed, their heavier analogues, namely selenocarbonyl (CSe) and tellurocarbonyl (CTe) complexes remain scarce. The limited availability of such CSe and CTe complexes has so far hampered our understanding of the differences between such chalcogenocarbonyl (CE: E=O, S, Se, Te) ligands. Herein, we report the synthesis and properties of a series of cationic half-sandwich ruthenium CE complexes of the type [CpRu(CE)(H2 IMes)(CNCH2 Ts)][BArF 4 ] (Cp=η5 -C5 H5 - ; H2 IMes=1,3-dimesitylimidazolin-2-ylidene; ArF =3,5-(CF3 )2 C6 H3 ). A combination of X-ray diffraction analyses, NMR spectroscopic analyses, and DFT calculations revealed an increasing π-accepting ability of the CE ligands in the order O<S<Se<Te. A variable-temperature NMR analysis of the thus obtained chiral-at-metal CE complexes indicated high stereochemical stability.

Thiocarbonyl-bound metallonitrosyl complexes with visible-light induced DNA cleavage and promising vasodilation activity

Nitric oxide has been involved in many key biological processes such as vasodilation, platelet aggregation, apoptosis, memory function, and this has drawn attention to the development of exogenous NO donors. Metallonitrosyl complexes are an important class of these compounds. Here, two new ruthenium nitrosyl complexes containing a thiocarbonyl ligand, with the formula cis-[Ru(phen)2(L)(NO)](PF6)3 (phen = phenantroline, L = thiourea or thiobenzamide), were synthesized and characterized by electronic spectroscopy, FTIR, NMR, mass spectrometry and voltammetric techniques. Theoretical calculations using Density Functional Theory (DFT) and Time-dependent Density Functional Theory (TD-DFT) were also used and further supported the characterizations of these complexes. An efficient release of nitric oxide by blue light was validated using a NO/HNO probe: 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, known as cPTIO. Interestingly, the complex containing thiourea cleaved DNA even in the dark, while both complexes showed great DNA photocleavage activity in blue light. This process might work mainly through NO and hydroxyl radical production. Additionally, these complexes showed promising vasodilator activity, whose mechanism of action was investigated using N-Nitro-l-arginine methyl ester hydrochloride (L-NAME) and 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) and compared to sodium nitroprusside. Both compounds were indeed NO-mediated heme-dependent activators of soluble guanylate cyclase. Additionally, they did not show any significant cytotoxicity against cancer cell lines U87 and GBM02. Altogether, these results supported both complexes having potential pharmacological applications that deserve further studies.

Isoequilibrium and free energy relationships in complex formation equilibria between Ag(I) and thiocarbonyl ligands in oxygenated solvent media

The standard enthalpy and entropy changes for the stepwise and overall complex formation homogeneous equilibria between Ag(I) and thiocarbonyl ligands or for the single reactions (series of reactions) in H2O, CH3OH (MeOH), C2H5OH (EtOH), C3H7OH (n-PrOH), CH3CHOHCH3 (Is-PrOH), and CH3COCH3 (Ac) are linearly correlated (corr. coeff. R > 0.9). The intercepts of the ∆H − ∆S regression straight lines ∆H = ∆Hres − τ ∆S depend on both solvent and number of coordinated ligands (hereafter coordination level) in the coordination sphere of the substrate AgLn. The slopes τ = d∆H/d∆S (hereafter susceptivities/sensitivities) depend only on solvent. Robust and sound hard solvent parameter scales, founded on solute–solute soft–soft interactions, can be set up on ∆Hres and/or τ bases. At 25 °C, the transfer standard free energies for the overall complex formation reactions at the single coordination levels n = 1, 2, or 3 between the various solvents are uncorrelated. When considered as unique set with n = 1, 2, and 3, the results linearly correlated (0.85 ≤ R ≤ 0.97) with slope ≈ 1 and intercepts depending on the actual couple of solvent media. The enthalpy(entropy) changes are uncorrelated.

Thermodynamics of complex formation equilibria between Ag(I) and thiocarbonyl ligands in propan-2-one (acetone) solution

Complex formation equilibria in propan-2-one between Ag(I) and thiourea (Tu), thioacetamide (Ta), N-methylthiourea (MeTu), N-ethylthiourea (EtTu), N,N′-diethylthiourea (Et2Tu), N-phenylthiourea (PhTu), N, N′-diphenylthiourea (Ph2Tu), and thiobenzanilide (TbAn) have been investigated by potentiometry at different temperatures t = 0–20 °C and self-determined ionic medium. Formation of mono-, bis-, and tris-coordinated AgL n complexes (charges are omitted) has been detected, but for Ag(I)–Ph2Tu system, where the occurrence of the mono-coordinate AgPh2Tu and bis-coordinate Ag(Ph2Tu)2 has been found. The stability constants have been deduced. The standard enthalpy and entropy changes have been evaluated from the linear dependence of the free energies on temperature.

Density functional theory investigation of the binding interactions between phosphoryl, carbonyl, imino, and thiocarbonyl ligands and the pentaaqua nickel(II) complex: Coordination affinity and associated parameters

Density Functional Theory (UB3LYP/6-311++G(d,p)) calculations of the affinity of the pentaaqua nickel(II) complex for a set of phosphoryl [OP(H)(CH3)(PhR)], imino [HNC(CH3)(PhR)], thiocarbonyl [SC(CH3)(PhR)] and carbonyl [OC(CH3)(PhR)] ligands were performed, where RNH2, OCH3, OH, CH3, H, Cl, CN, and NO2 is a substituent at the para-position of a phenyl ring.The affinity of the pentaaqua nickel(II) complex for these ligands was analized and quantified in terms of interaction enthalpy (ΔH), Gibbs free energy (ΔG298), geometric and electronic parameters of the resultant octahedral complexes. The ΔH and ΔG298 results show that the ligand coordination strength increases in the following order: carbonyl < thiocarbonyl < imino < phosphoryl. This coordination strength order is also observed in the analysis of the metal-ligand distances and charges on the ligand atom that interacts with the Ni(II) cation. The electronic character of the substituent R is the main parameter that affects the strength of the metal-ligand coordination. Ligands containing electron-donating groups (NH2, OCH3, OH) have more exothermic ΔH and ΔG298 than ligands with electron-withdrawing groups (Cl, CN, NO2). The metal-ligand interaction decomposed by means of the energy decomposition analysis (EDA) method shows that the electronic character of the ligand modulates all the components of the metal-ligand interaction. The absolute softness of the free ligands is correlated with the covalent contribution to the instantaneous interaction energy calculated using the EDA method. © 2013 Wiley Periodicals, Inc.

DFT studies of imino and thiocarbonyl ligands with the pentaaqua Mg2+ cation: affinity and associated parameters

The affinity of the pentaaqua Mg(2+) cation for a set of para-substituted imino [HN = CHC₆H₄(R)] and thiocarbonyl [S = CHC₆H₄(R)] ligands (R = H, F, Cl, Br, OH, OCH₃, CH₃, CN, NH₂ and NO₂) was analyzed with DFT (B3LYP/6-31+G(d)) and semi-empirical (PM6-DH2) methods. The interaction enthalpy was calculated to quantify the affinity of the Mg(2+) cation for the ligands. Additionally, geometric and electronic parameters were correlated with the intensity of the metal-ligand interaction. The imino ligands have stronger interaction with the pentaaqua Mg(2+) cation than the thiocarbonyl derivatives. The electronic nature of the substituent is the main parameter that determines the interaction enthalpy. Ligands with electron donor substituents have more exothermic interaction enthalpies than those with electron withdrawing groups. The HSBA analysis showed that the interaction between the Mg(2+) cation and hard bases (imino ligands) is stronger than with soft bases (thiocarbonyl derivatives). The EDA analysis showed that the electrostatic, covalent and repulsion components of the interaction are the most affected by the substituent, whereas the dispersion and exchange components are almost constant.

Ab Initio, DFT and semi-empirical studies on interactions of phosphoryl, carbonyl, imino and thiocarbonyl ligands with the li+ cation: affinity and associated parameters

+para uma serie de ligantes fosforila, carbonila, imino e tiocarbonila substituidos na posicao para de um anel aromatico foi calculada com os metodos ab initio MP2/6-311+G(d,p), DFT B3LYP/6-311+G(d,p) e semi-empirico PM6. Cada serie de ligante e constituida pelos seguintes grupos substituidos na posicao para: NH 2 , OCH 3 , CH 3 , H, Cl, CN and NO 2 . A entalpia de interacao foi calculada para quantificar a afinidade dos ligantes para o cation Li + . Parâmetros geometricos e eletronicos foram correlacionados com a forca da interacao metal-ligante. A natureza eletronica dos grupos substituintes e o principal parâmetro que modula a intensidade da ligacao metal-ligante. Grupos doadores de eletrons tornam a entalpia de interacao mais exotermica, enquanto grupos aceptores de eletrons tornam a entalpia de interacao menos exotermica. Analise da decomposicao da energia mostra que os grupos substituintes modulam a intensidade da componente eletrostatica da interacao sem afetar a componente covalente. The affinity of the Li + cation for a set of para-substituted phosphoryl, carbonyl, imino and thiocarbonyl ligands was calculated with the ab initio MP2/6-311+G(d,p), DFT B3LYP/6311+G(d,p) and semi-empirical PM6 methods. Each set of ligand is constituted by the following para-substituted groups: NH 2 , OCH 3 , CH 3 , H, Cl, CN and NO 2 . The interaction enthalpy was calculated to quantify the affinity of the ligands for the Li + cation. Geometric and electronic parameters were correlated with the strength of the metal-ligand interaction. The electronic nature of the para-substituted group is the main parameter that modulates the intensity of the metalligand binding energy. Electron donor groups make the interaction enthalpy more exothermic, whereas electron acceptor groups make the interaction enthalpy less exothermic. The energy decomposition analysis shows that the para-substituted groups modulate the intensity of the electrostatic component of the interaction without affecting the covalent component.

Annulation of an Iridabenzene through Formal Cycloaddition Reactions with Organonitriles

The cationic iridacyclopentadiene complex [Ir(C4H4)(CS)(MeCN)(PPh3)2][CF3SO3] (2), which is derived from the reaction between [Ir(CS)(MeCN)(PPh3)2][CF3SO3] (1) and ethyne, undergoes a thermally induced migratory insertion reaction involving the thiocarbonyl ligand to form the cationic iridabenzene [Ir(C5H4{S-1})(MeCN)(PPh3)2][CF3SO3] (3) in very high yield. The addition of methyl triflate to this iridabenzene in the presence of NCMe results in methylation of the sulfur atom, and the red dicationic iridabenzene [Ir(C5H4{SMe-1})(MeCN)2(PPh3)2][PF6]2 (4) is obtained after the addition of NH4PF6. Upon treatment of 3 with RCN (R = Me or p-tolyl) and acid, a cyclization reaction ensues between the organonitrile and the η2-C(S)Ir function of the iridabenzene to give the corresponding iridabenzothiazolium complexes [Ir(C5H4{NH═C(R)S-1})(RCN)(PPh3)2][PF6]2 [R = Me (6a); p-tolyl (6b)], where the iridium occupies a ring junction position.

A Stable Iridabenzene Formed from an Iridacyclopentadiene Where the Additional Ring-Carbon Atom Is Derived from a Thiocarbonyl Ligand

The cationic thiocarbonyl complex [Ir(CS)(MeCN)(PPh3)2][CF3SO3] (1) reacts sequentially with ethyne and LiCl to give the iridacyclopentadiene Ir[C4H4]Cl(CS)(PPh3)2 (2), which in turn when heated with methyl triflate followed by addition of LiCl produces the stable, purple, iridabenzene Ir[C5H4(SMe-1)]Cl2(PPh3)2 (3). This iridabenzene undergoes electrophilic aromatic bromination in the position para to the SMe substituent to form Ir[C5H3(SMe-1)(Br-4)]Br2(PPh3)2 (4).

Two Generalizable Routes to Terminal Carbido Complexes

Desulfurization of the thiocarbonyl ligand in square pyramidal [Ru(CS)Cl2(PCy3)2] (1-S) via sulfur atom abstraction using [Mo(H)(eta2-Me2CNAr)(N[i-Pr]Ar)2] forms [Ru(C)Cl2(PCy3)2] (1) cleanly over several hours in benzene; isolated yield is 55%. Complex 1 is also formed in 87% isolated yield upon reaction of [Ru(CHR)(PCy3)2Cl2] (R = p-C6H4Me, 2; Ph, 3) with vinyl acetate in dichloromethane. Complex 1-S is re-formed quantitatively from 1 upon treatment with elemental sulfur in CH2Cl2, but is prepared most conveniently by treatment of crude [Ru(CS)Cl2(PPh3)2(OH2)] with excess PCy3 in toluene. Nearly quantitative conversion of 1 to [Ru(CO)Cl2(PCy3)2] (1-O) occurs upon addition of dimethyldioxirane solution in acetone to 1 dissolved in CH2Cl2 at ca. -90 degrees C.

A novel route to dithiolenes from 1,3-dithiole-2-thiones at a dicobalt centre

On reaction with [Co2(μ-dppm)(CO)6] at room temperature, 4,5-bis(alkoxycarbonyl)-1,3-dithiole-2-thiones are dismantled into dithiolene and thiocarbonyl ligands by cleavage of two C–S bonds to give [Co2(μ-CS)(μ-S2C2R2)(CO)3(μ-dppm)] (R = CO2Me, CO2Et).

Photooxidation of Rh(PPh 3) 2(CS)Cl induced by metal-to-ligand charge transfer excitation

The longest-wavelength absorption of Rh I(PPh 3) 2(CS)Cl at λ max=452 nm is assigned to a metal-to-ligand charge transfer (MLCT) transition which terminates at the π* orbital of the thiocarbonyl ligand. MLCT excitation of the complex in CH 2Cl 2 initiates a photooxidation which finally leads to Rh III(PPh 3) 2(CS)Cl 3 as a stable photoproduct with φ=0.003 at λ irr=436 nm.

Reactions of Cp*3Co3(.mu.3-H)(.mu.2-H)3 with Carbon Dioxide, Carbon Disulfide, and Phenyl Isocyanate

The tetrahydride tricobalt cluster Cp {sub 3}Co{sub 3}({mu}{sub 2}-H){sub 3}({mu}{sub 3}-H) (1) reduces CO{sub 2} at 120 {degrees}C to form the dicobalt dicarbonyl complex [CpCo({mu}-CO)]{sub 2} (2) in 45% yield by H NMR. 1 reacted with CS{sub 2} at room temperature to form the thiocarbonyl cluster Cp {sub 3}Co{sub 3}({mu}{sub 3}-CS)({mu}{sup 3}-S) (3) in 19% isolated yield. 3 was characterized by X-ray crystallography and shown to consist of a triangle of cobalt atoms [Co-Co{sub ave}=2.495 {Angstrom}] capped on one face by a {mu}{sub 3}-sulfide ligand [Co-{mu}{sub 3}-S{sub ave} = 2.129 {Angstrom}] and on the opposite face by a {mu}{sub 3}-thiocarbonyl ligand [Co-{mu}{sub 3}-C{sub ave} = 1.949, {mu}{sub 3}-C-S=1.634(5) {Angstrom}]. 1 reacted with phenyl isocyanate at 55 {degrees}C to form the N,N{prime}-diphenylureylene complex Cp {sub 2}Co{sub 2}({mu}{sub 2},{mu}{sub 2}-{eta}{sup 2}-PhNCONPh) (5), the dicarbonyl tricobalt cluster Cp {sub 3}Co{sub 3}({mu}{sub 3}-CO){sub 2} (6), and the carbonyl dimer 2. 5 was isolated in 13% yield and characterized by X-ray crystallography, which revealed that each nitrogen atom of the {eta}{sup 2}-N,N{prime}-diphenylureylene ligand was symmetrically bonded to cobalt atoms [Co-Co = 2.456-(1), Co-{mu}{sub 2}-N{sub ave} = 1.959 {Angstrom}].

Synthesis, characterization and reactivity of ruthenium tetraphenylporphyrin complexes containing the thiocarbonyl ligands

A new synthetic route to generate tetraphenylporphyrin ruthenium(II) thiocarbonyl complexes of the general formula Ru 11(Por)(CS)L has been developed and the chemistry and electrochemistry of these complexes have been studied. [Ru IV(Por)(EtO)] 2O has been applied as a convenient starting material for ligand incorporation using carbon disulphide, thiophosgene and benzyl trichloromethyl thioether as thiocarbonyl precursors in the reducing medium. The RuCS bond is very strong and resistant to nucleophilic replacement. Thiocarbonyl and carbonyl ruthenium(II) porphyrin complexes reveal essential similarity as far as chemical and electrochemical properties are concerned, with the exception of the internal reactivity of the thiocarbonyl ligand. One-electron oxidation of [Ru(Por)(CS)(EtOH)] led to the formation of the respective π-cation radical characterized by visible, IR and 1H NMR spectroscopy.

Synthesis and stereophysical characterization of the Fischer-Palm-related 49-electron thiocarbonyl-capped triangular nickel clusters Ni3(.eta.5-C5H5-xMex)3(.mu.3-X)(.mu.3-Y) (x = 0, 1), containing .pi.-acceptor X and Y capping Ligands (X = Y = CS; X = CS, Y = CO): comparative experimental/theoretical analysis of the triply bridging carbonyl and thiocarbonyl ligands in analogous molecular environments

Synthesis and stereophysical characterization of the Fischer-Palm-related 49-electron thiocarbonyl-capped triangular nickel clusters Ni3(.eta.5-C5H5-xMex)3(.mu.3-X)(.mu.3-Y) (x = 0, 1), containing .pi.-acceptor X and Y capping Ligands (X = Y = CS; X = CS, Y = CO): comparative experimental/theoretical analysis of the triply bridging carbonyl and thiocarbonyl ligands in analogous molecular environments

Migratory insertion of silyl and thiocarbonyl ligands on ruthenium and osmium to give the .eta.2-silathioacyl complexes M(.eta.2-C[S]SiMe2X)Cl(CO)(PPh3)2 (M = Ru, Os; X = Cl, OEt)

Migratory insertion of silyl and thiocarbonyl ligands on ruthenium and osmium to give the .eta.2-silathioacyl complexes M(.eta.2-C[S]SiMe2X)Cl(CO)(PPh3)2 (M = Ru, Os; X = Cl, OEt)

Reactions of carbonyl and nitrosyl ruthenium complexes with uninegative (X,S)-donor ligands (X = S, P)

Reactions of 1,1-dithiolates (EtOCS 2 − and Et 2NCS 2 −) and the related (P,S)- donor ligand (Ph 2PCSNPh −) with halocarbonylphosphine complexes of ruthenium give halide substitution derivatives with chelation of the (S,S)- or (P,S)-donor ligand. The reaction of [RuCl 2(CO)(CS)(PPh 3) 2] with dithiolates gives rise to displacement of the thiocarbonyl ligand, while with Ph 2PCSNPh − the derivative [RuCl(Ph 2PCSNPh)(CO) (CS)(PPh 3)] is obtained. The carbonyl nitrosyl complex [RuCl(CO)(NO)(PPh 3) 2] reacts with displacement of nitrosyl and formation of [RuCl(X,S)(CO)(PPh 3) 2] complexes.

Linear semibridging carbonyls—III. Carbonyl and thiocarbonyl ligands as four-electron donors

Parameter-free Fenske—Hall molecular orbital calculations predict the electronic structure and bonding of several heterobimetallic complexes containing linear semibridging carbonyl and thiocarbonyl ligands. The results suggest that the linear semibridging ligand acts as a four-electron donor only when the secondary metal centre is an electron-deficient early transition metal atom. When the secondary centre is a late transition metal atom, the linear semibridging ligand acts as a π-acceptor of electron density, even if the late metal has less than 18 electrons. Holes in the d shell of the early metal atoms are more prominent than those in the late metal atoms where the higher nuclear charge pulls the d electrons closer to the nucleus. The role of the semibridging ligand is to fill in the prominent holes in the d shell when they exist by donating electron density from an occupied π orbital. When there are no holes in the d shell, or when the holes are very small, the semibridging ligands accept electron density from the secondary metal centre into a π* orbital.