Synthesis and structural,spectroscopic, and electrochemical characterization of new ruthenium dimethyl sulfoxide nitrosyls

The reactivity of ruthenium(II)- and ruthenium(III)-chloride-dimethyl sulfoxide precursors and of the antimetastatic drug [ImH][trans-RuCl(4)(dmso-S)(Im)] (NAMI-A, Im = imidazole, dmso = dimethyl sulfoxide) toward NO was investigated. Treatment of [(dmso)(2)H][trans-RuCl(4)(dmso-S)(2)] and mer-RuCl(3)(dmso)(3) with gaseous NO yielded [(dmso)(2)H][trans-RuCl(4)(dmso-O)(NO)] (1) and mer,cis-RuCl(3)(dmso-O)(2)(NO) (2), respectively. Thus, coordination of the strong pi-acceptor NO induces a S to O linkage isomerization of the dmso trans to it to avoid competition for pi-electrons. In light-protected nitromethane solutions, complex 2 equilibrates slowly with the two isomers mer-RuCl(3)(dmso-S)(dmso-O)(NO) (3), with NO trans to Cl, and mer-RuCl(3)(dmso-S)(dmso-O)(NO) (4), with NO trans to dmso-O; the equilibrium mixture consists of ca. 64% 2, 3% 3, and 33% 4. Treatment of the Ru(II) precursor trans-RuCl(2)(dmso-S)(4) with gaseous NO in CH(2)Cl(2) solution yielded the nitrosyl-nitro derivative trans,cis,cis-RuCl(2)(dmso-O)(2)(NO)(NO(2)) (5). Finally, [(Im)(2)H][trans-RuCl(4)(Im)(NO)] (6) was prepared by treatment of [ImH][trans-RuCl(4)(dmso-O)(NO)] (1Im) with an excess of imidazole in refluxing acetone. The spectroscopic features are consistent with the [Ru(NO)](6) formulation for all complexes, that is, a diamagnetic Ru(II) nucleus bound to NO(+). Compounds 1, 2, 5, and 6 were characterized also by X-ray crystallography; they all show a linear nitrosyl group, with short Ru-NO bond distances consistent with a strong d(pi) --> pi NO back-bonding. An unusual inertness of O-bonded dmso was observed in compound 1. Complexes 1, 2, 3, 5, and 6 are all redox active in DMF solutions showing irreversible reductions whose peak potentials depend on the other ligands attached to the Ru metal center. The site of reduction is the NO(+) moiety. The reduced complexes are not stable and release a Cl(-) or NO(2)(-) ligand followed by the NO(*) radical. The chemical reactions following electron transfer are all fast (rate constant >100 s(-1) at 293 K). The Ru product species are not redox active within the DMF window.     

Thermodynamic model of solubility for CO2 in dimethyl sulfoxide

The solubility of CO₂ in dimethyl sulfoxide has been determined from 293.15 K to 313.15 K and partial pressure of CO₂ from 5.56 kPa to 18.2 kPa. Based on the data obtained from the CO₂ solubility experiments, a gas–liquid phase equilibrium model for CO₂–DMSO system was proposed. The average relative deviation between the experimental data of equilibrium partial pressure of CO₂ in DMSO and the corresponding data predicted by the model proposed is 4.85%, it shows that the agreement is satisfactory.     

Oxidative addition of water to novel Ir(I) complexes stabilized by dimethyl sulfoxide ligands.

The oxidative addition of water to novel Ir(I) DMSO complexes is described. IrCl(DMSO)3 (1) is synthesized in 90% yield when treating a toluene slurry of [Ir2Cl2(COE)4] (COE = cyclooctene) with excess DMSO. Its dimer, [Ir2Cl2(DMSO)4] (2) is obtained in 95% yield starting from 1. The cationic complex [Ir(DMSO)4]PF6 (6) is prepared in situ from [Ir(COE)2(O=CMe2)2]PF6 (5). These complexes add water at room temperature, giving rise to the oxidative addition products syn-[(DMSO)2HIr(mu-OH)2(mu-Cl)IrH(DMSO)2] [IrCl2(DMSO)2] (3) and anti-[(DMSO)2(DMSO)HIr(mu-OH)2IrH(DMSO)2(DMSO)](PF6)2 (7), respectively. Reductive elimination in pyridine leads to quantitative isolation of mixed Ir(I) DMSO-pyridine complexes IrCl(py)(DMSO)2 (4) and [Ir(py)2(DMSO)2]PF6 (8), respectively. Compounds 1, 3, and 7 have been characterized by X-ray crystallography. 3 and 7 show dimeric structures with the hydroxo ligands bridging the iridium atoms and in 7 both O- and S-bonded DMSO ligands are present.     

Reversible, electrochemically controlled binding of phosphine to iron and cobalt bis(dithiolene) complexes

The homoleptic bis(dithiolene) complexes [M(S(2)C(2)R(2))(2)](2) (M = Fe, Co; R = p-anisyl) undergo two successive reductions to form anions that display [M(S(2)C(2)R(2))(2)](2)(2-) <--> 2[M(S(2)C(2)R(2))(2)](1-) solution equilibria. The neutral dimers react with Ph3P to form square pyramidal [M(Ph(3)P)(S(2)C(2)R(2))(2)](0). Voltammetric measurements upon [M(Ph(3)P)(S(2)C(2)R(2))(2)](0) in CH(2)Cl(2) reveal only irreversible features at negative potentials, consistent with Ph(3)P dissociation upon reduction. Dissociation and reassociation of Ph(3)P from and to [Fe(Ph(3)P)(S(2)C(2)R(2))(2)](0) is demonstrated by spectroelectrochemical measurements. These collective observations form the basis for a cycle of reversible, electrochemically controlled binding of Ph(3)P to [M(S(2)C(2)R(2))(2)](2) (M = Fe, Co; R = p-anisyl). All members of the cycle ([M(S(2)C(2)R(2))(2)](2)(0), [M(S(2)C(2)R(2))(2)](2)(1-), [MM(S(2)C(2)R(2))(2)](2)(2-), [M(S(2)C(2)R(2))(2)](1-), [M(Ph(3)P)(S(2)C(2)R(2))(2)]) for M = Fe, Co have been characterized by crystallography. Square planar [Fe(S(2)C(2)R(2))(2)](1-) is the first such iron dithiolene species to be structurally identified and reveals Fe-S bond distances of 2.172(1) and 2.179(1) Angstrom, which are appreciably shorter than those in corresponding square planar dianions.     

Synthesis and structures of bis(dithiolene)molybdenum complexes related to the active sites of the DMSO reductase enzyme family

Structural analogues of the reduced (Mo(IV)) sites of members of the DMSO reductase family of molybdoenzymes are sought. These sites usually contain two pterin-dithiolene cofactor ligands and one protein-based ligand. Reaction of [Mo(MeCN)3(CO)3] and [Ni(S2C2R2)2] affords the trigonal prismatic complexes [Mo(CO)2(S2C2R2)2] (R = Me (1), Ph (2)), which by carbonyl substitution serve as useful precursors to a variety of bis(dithiolene)molybdenum-(IV,V) complexes. Reaction of 1 with Et4NOH yields [MoO(S2C2Me2)2]2- (3), which is readily oxidized to [MoO(S2C2Me2)2]1- (4). The hindered arene oxide ligands ArO- afford the square pyramidal complexes [Mo(OAr)(S2C2R2)2]1- (5, 6). The ligands PhQ- affordthe trigonal prismatic monocarbonyls [Mo(CO)(QPh)(S2C2Me2)2]1- (Q = S (8), Se (12)) while the bulky ligand ArS- forms square pyramidal [Mo(SAr)(S2C2R2)2]- (9, 10). In contrast, reactions with ArSe- result in [Mo(CO)(SeAr)(S2C2R2)2]1-(14, 15), which have not been successfully decarbonylated. Other compounds prepared by substitution reactions of 1 and 2 include the bridged dimers [Mo2(mu-Q)2(S2C2Me2)4]2- (Q = S (7), Se (11)) and [Mo2(mu-SePh)2(S2C2Ph2)4]2- (13). The complexes 1, 3-5, 7-10, 12-14, [Mo(S2C2Me2)3] (16), and [Mo(S2C2Me2)3]1- (17) were characterized by X-ray structure determinations. Certain complexes approach the binding arrangements in at least one DMSO reductase (5/6) and its Ser/Cys mutant, and in dissimilatory nitrate reductases (9/10). This investigation provides the initial demonstration of the new types of bis(dithiolene)molybdenum(IV) complexes available through [Mo(CO)2(S2C2R2)2] precursors, some of which will be utilized in reactivity studies. (Ar = 2,6-diisopropylphenyl or 2,4,6-triisopropylphenyl.)     

A mechanism for the addition of ethylene to nickel bis‐dithiolene

Density functional theory calculations predict a new lower energy route for the formation of the desired interligand addition product from the reaction between ethylene and nickel bis(dithiolene). The new route involves the initial binding of ethylene along the nickel–sulfur bond. The barrier heights for adding ethylene along this bond for the neutral and anionic nickel complexes are compared to each other as well as to a previously published previous mechanism. Selected structural parameters of the studied species have been analyzed to highlight the structural change on specific reactions. It was found that the ethylene/nickel bis‐dithiolene reaction occurs preferably via the nickel–sulfur bond of the neutral species, forming a complex which then rearranges to a desired interligand adduct via a low barrier. © 2012 Wiley Periodicals, Inc.     

Regioselectivity in the addition of alkanethiols to vinylacetylene in superbasic media of alkali-metal hydroxides in dimethyl sulfoxide

Conclusions The reaction of vinylacetylene with alkanethiols is largely directed toward the formation of alkyl 1,3-butadien-l-yl sulfide with increasing basicity of the system consisting of an alkali-metal hydroxide and DMSO. A reduction in the basicity facilitates the formation of alkyl 2,3-butadien-l-yl sulfide.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2800–2803, December, 1985.     

Bis(dithiolene)molybdenum analogues relevant to the DMSO reductase enzyme family: synthesis, structures, and oxygen atom transfer reactions and kinetics.

A series of dithiolene complexes of the general type [Mo(IV)(QR')(S(2)C(2)Me(2))(2)](1)(-) has been prepared and structurally characterized as possible structural and reactivity analogues of reduced sites of the enzymes DMSOR and TMAOR (QR' = PhO(-), 2-AdO(-), Pr(i)()O(-)), dissimilatory nitrate reductase (QR' = 2-AdS(-)), and formate dehydrogenase (QR' = 2-AdSe(-)). The complexes are square pyramidal with the molybdenum atom positioned 0.74-0.80 A above the S(4) mean plane toward axial ligand QR'. In part on the basis of a recent clarification of the active site of oxidized Rhodobacter sphaeroides DMSOR (Li, H.-K.; Temple, C.; Rajagopalan, K. V.; Schindelin, H. J. Am. Chem. Soc. 2000, 122, 7673), we have adopted the minimal reaction paradigm Mo(IV) + XO right arrow over left arrow Mo(VI)O + X involving desoxo Mo(IV), monooxo Mo(VI), and substrate/product XO/X for direct oxygen atom transfer of DMSOR and TMAOR enzymes. The [Mo(OR')(S(2)C(2)Me(2))(2)](1)(-) species carry dithiolene and anionic oxygen ligands intended to simulate cofactor ligand and serinate binding in DMSOR and TMAOR catalytic sites. In systems with N-oxide and S-oxide substrates, the observed overall reaction sequence is [Mo(IV)(OR')(S(2)C(2)Me(2))(2)](1)(-) + XO --> [Mo(VI)O(OR')(S(2)C(2)Me(2))(2)](1)(-) --> [Mo(V)O(S(2)C(2)Me(2))(2)](1)(-). Direct oxo transfer in the first step has been proven by isotope labeling. The reactivity of [Mo(OPh)(S(2)C(2)Me(2))(2)](1)(-) (1) has been the most extensively studied. In second-order reactions, 1 reduces DMSO and (CH(2))(4)SO (k(2) approximately 10(-)(6), 10(-)(4) M(-)(1) s(-)(1); DeltaS(double dagger) = -36, -39 eu) and Me(3)NO (k(2) = 200 M(-)(1) s(-)(1); DeltaS(double dagger) = -21 eu) in acetonitrile at 298 K. Activation entropies indicate an associative transition state, which from relative rates and substrate properties is inferred to be concerted with X-O bond weakening and Mo-O bond making. The Mo(VI)O product in the first step, such as [Mo(VI)O(OR')(S(2)C(2)Me(2))(2)](1)(-), is an intermediate in the overall reaction sequence, inasmuch as it is too unstable to isolate and decays by an internal redox process to a Mo(V)O product, liberating an equimolar quantity of phenol. This research affords the first analogue reaction systems of biological N-oxide and S-oxide substrates that are based on desoxo Mo(IV) complexes with biologically relevant coordination. Oxo-transfer reactions in analogue systems are substantially slower than enzyme systems based on a k(cat)/K(M) criterion. An interpretation of this behavior requires more information on the rate-limiting step(s) in enzyme catalytic cycles. (2-Ad = 2-adamantyl, DMSOR = dimethyl sulfoxide reductase, TMAOR = trimethylamine N-oxide reductase)     

Spectroscopic and electronic structure studies of a dimethyl sulfoxide reductase catalytic intermediate: implications for electron- and atom-transfer reactivity

The electronic structure of a genuine paramagnetic des-oxo Mo(V) catalytic intermediate in the reaction of dimethyl sulfoxide reductase (DMSOR) with (CH(3))(3)NO has been probed by electron paramagnetic resonance (EPR), electronic absorption, and magnetic circular dichroism (MCD) spectroscopies. EPR spectroscopy reveals rhombic g- and A-tensors that indicate a low-symmetry geometry for this intermediate and a singly occupied molecular orbital that is dominantly metal centered. The excited-state spectroscopic data were interpreted in the context of electronic structure calculations, and this has resulted in a full assignment of the observed MCD and electronic absorption bands, a detailed understanding of the metal-ligand bonding scheme, and an evaluation of the Mo(V) coordination geometry and Mo(V)-S(dithiolene) covalency as it pertains to the stability of the intermediate and electron-transfer regeneration. Finally, the relationship between des-oxo Mo(V) and des-oxo Mo(IV) geometric and electronic structures is discussed relative to the reaction coordinate in members of the DMSOR enzyme family.     

The addition polymerization of a p=c bond: a route to new phosphine polymers

Addition polymerization, the most general method of preparation for organic polymers, has successfully been extended to P=C bonds. The polymerization of a phosphaalkene has been initiated by thermolysis or with alkyllithium reagents. The unprecedented poly(methylenephosphine)s are easily oxidized using oxygen or sulfur to give air stable macromolecules. A molecular weight (M(w)) of 35000 g/mol for the poly(methylenephosphine sulfude) was estimated by light-scattering GPC.     

Synthesis and structure of a mixed ligand complex of tris(1-phenyl-3-methyl-4-trifluoroacetyl-pyrazolone-5)bis(dimethyl sulfoxide) neodymium

A mixed ligand complex of l-phenyl-3-methyl-4-trifluoroacetyl pyrazolone-5 (HPMTFP) and dimethyl sulfoxide (DMSO) with neodymium having molecular formula Nd(PMTFP)₃ · 2DMSO has been synthesized. Its crystal and molecular structures have been determined by a four-circle X-ray diffractometer. The complex crystallizes in monoclinic with space group P 2₁/n. a = 21.897 (4), b = 23.339 (4), c = 8.958 (2)Å, β = 96.61 (3)°, Z = 4. The Nd atom is coordinated by eight oxygen atoms, which takes a distorted delta dodecahedron arrangement around the central Nd atom. The average bond length of Nd—O is 2.45 Å. The IR spectra have been discussed as well.     

Syntheses, characterization, and catalytic ability in alkane oxygenation of chloro(dimethyl sulfoxide)ruthenium(II) complexes with tris(2-pyridylmethyl)amine and its derivatives

New ruthenium(II) complexes having a tetradentate ligand such as tris(2-pyridylmethyl)amine (TPA), tris[2-(5-methoxycarbonyl)pyridylmethyl]amine [5-(MeOCO)3-TPA], tris(2-quinolylmethyl)amine (TQA), or bis(2-pyridylmethyl)glycinate (BPG) have been prepared. The reaction of the ligand with [RuCl2(Me2SO)4] resulted in a mixture of trans and cis isomers of the chloro(dimethyl sulfoxide-kappaS)ruthenium(II) complexes containing a TPA or a BPG, whereas a trans(Cl,N(amino)) isomer was selectively obtained for 5-(MeOCO)3-TPA and TQA. The trans and cis isomers of the [RuCl(TPA)(Me2SO)]+ complex were easily separated by fractional recrystallization. The molecular structures of trans- and cis(Cl,N(amino))-[RuCl(TPA)(Me2SO)]+ complexes and the trans(Cl,N(amino))-[RuCl{5-(MeOCO)3-TPA}(Me2SO)]+ complex have been determined by X-ray structural analyses. The reaction of TPA with [RuCl2(PhCN)4] gave a single isomer of the chloro(benzonitrile)ruthenium(II) complex, whereas the bis(benzonitrile)ruthenium(II) complex was obtained with BPG. The cis(Cl,N(amino))-[RuCl(TPA)(Me2SO)]+ complex is thermodynamically much less stable than the trans isomer and isomerizes in dimethyl sulfoxide at 65-100 degrees C. Oxygenation of alkanes catalyzed by these ruthenium(II) complexes has been examined. The chloro(dimethyl sulfoxide-kappaS)ruthenium(II) complexes with TPA and its derivatives using m-chloroperbenzoic acid as a cooxidant showed high catalytic ability. Adamantane was efficiently and selectively oxidized to give 1-adamantanol up to 88%. The chloro(dimethyl sulfoxide-kappaS)ruthenium(II) complex with 5-(MeOCO)3-TPA was found to be the most active catalyst among the complexes examined.     

Electronic structures of tris(dioxolene)chromium and tris(dithiolene)chromium complexes of the electron-transfer series [Cr(dioxolene)(3)](z) and [Cr(dithiolene)(3)](z) (z = 0, 1-, 2-, 3-). A combined experimental and density functional theoretical study

From the reaction mixture of 3,6-di-tert-butylcatechol, H2[3,6L(cat)], [CrCl3(thf)3], and NEt3 in CH3CN in the presence of air, the neutral complex [CrIII(3,6L*(sq))3] (S = 0) (1) was isolated. Reduction of 1 with [Co(Cp)2] in CH2Cl2 yielded microcrystals of [Co(Cp)2][CrIII(3,6L*(sq))2(3,6L(cat))] (S = 1/2) (2) where (3,6L*(sq)(1-) is the pi-radical monoanionic o-semiquinonate of the catecholate dianion (3,6Lcat)(2-). Electrochemistry demonstrated that both species are members of the electron-transfer series [Cr(3,6LO,O)]z (z = 0, 1-, 2-, 3-). The corresponding tris(benzo-1,2-dithiolato)chromium complex [N(n-Bu)4][CrIII(3,5L*S,S)2(3,5LS,S)] (S = 1/2) (3) has also been isolated; (3,5LS,S)(2-) represents the closed-shell dianion 3,5-di-tert-butylbenzene-1,2-dithiolate(2-), and (3,5L*S,S)(1-) is its monoanionic pi radical. Complex 3 is a member of the electron-transfer series [Cr(3,5L(S,S))3]z (z = 0, 1-, 2-, 3-). It is shown by Cr K-edge and S K-edge X-ray absorption, UV-vis, and EPR spectroscopies, as well as X-ray crystallography, of 1 and 3 that the oxidation state of the central Cr ion in each member of both electron-transfer series remains the same (+III) and that all redox processes are ligand-based. These experimental results have been corroborated by broken symmetry density functional theoretical calculations by using the B3LYP functional.