Carboxylato Complexes Research Articles

Synthesis and reactivity of ?-?2-carbamato complexes of triosmium decacarbonyl

The synthesis of (μ-H)(μ-η2-RR′NCO2)Os3(CO)10 (R=R′=CH3 2a; R=R′=CH2CH3,2b; R=CH3, R′=CH2CH3,2c) and their cyclic analogs (μ-H)(μ-η2- -CO2)Os3(CO)10(n=42d,n=5,2e) from carbon dioxide, secondary amine, and Os3(CO)10(CH3CN)2 (1) are reported. A solid-state structure of2c reveals a bonding mode for the carbamato ligand very similar to that observed for related carboxylato complexes. Compound2c crystallizes in the orthorombic space group Pbca witha=9.136 (3),b=15.310 (4) andc=30.361 (5) A;V=4247 A3,Z=8. Least-squares refinement of 2405 observed reflections gave a final agreement factor ofR=0.043 (R w =0.043). The reactivity of the complexes2a–2e was examined. Compound2c or2b give good yields of the cluster derivatives (μ-H)(μ-X)Os3(CO)10 (X=Cl,3; X=OCH3,4; X=N(CH3)2,7) when reacted with HX. Reaction of2a with P(CH3)3 at 68°C gives good yields of the otherwise difficult to obtain 1,1,2-(P(CH3)3)3Os3(CO)9 (5). Evidence is presented that suggests that2a–2e form by oxidative addition of preformed carbamic acids to1.

ChemInform Abstract: Carboxylato Complexes of Zirconium(IV). Part 4. The Formation of Bis‐(heptafluorocarboxylato)zirconium(IV) Difluoride.

ChemInform Abstract: Carboxylato Complexes of Zirconium(IV). Part 4. The Formation of Bis‐(heptafluorocarboxylato)zirconium(IV) Difluoride.

Carboxylato complexes of zirconium(IV) Part IV. The formation of bis(heptafluorocarboxylato)zirconium(IV) difluoride

The reaction of heptafliuorobutyric acid with zirconium tetrachloride has been shown to form ZrF2(C 3F 7COO) 2(CH 3OCH 2CH 2OCH 3) in ethylene glycol dimethyl ether and ZrF 2(C 3F 7COO) 2 in carbon tetrachloride instead of the expected product Zr(C 3F 7COO) 4. The infrared spectra and possible structure of these products are discussed.

ESR Spin Trapping Detection of Hydroxyl Radicals in the Reactions of Cr(V) Complexes with Hydrogen Peroxide

Electron spin resonance (ESR) measurements provide direct evidence for the involvement of Cr(V) in the reduction of Cr(VI) by NAD(P)H. Addition of hydrogen peroxide (H2O2) to NAD(P)H-Cr(VI) reaction mixtures suppresses the Cr(V) signal and generates hydroxyl (.OH) radicals (as detected via spin trapping), suggesting that Cr(V) reacts with H2O2 to generate the .OH radicals. Reaction between H2O2 and a Cr(V)-glutathione complex, and between H2O2 and several Cr(V)-carboxylato complexes also produces .OH radicals. These results suggest that Cr(V) complexes catalyze the generation of .OH radicals from H2O2, and that .OH radicals might play a significant role in the mechanism of Cr(VI) cytotoxicity.

Electronic excitation MO assignment of rhodium carboxylato complexes, Rh2(O2CR)4(Lax)2, using MCD experiment and theory

Electronic excitation MO assignment of rhodium carboxylato complexes, Rh2(O2CR)4(Lax)2, using MCD experiment and theory

CC coupling of activated alkanes with carbon dioxide by [(phen)(Ph 3P)Cu(O 2COH)

The reactions of the bicarbonatocopper( I) complex, [(phen)(Ph 3P)Cu(O 2COH)] ( A, phen = 1,10-phenanthroline), with activated alkanes CH 2(R)(R′) (R = R′ = CN; R = R′ = COOEt; R = CN, R′ = COOEt), in the presence and in the absence of carbon dioxide have been studied. Reaction of malonodinitrile with A under an inert atmosphere gives the organocopper complexex, [(phen)(Ph 3P)CuCH(CN) 2] ( 1), whereas in the presence of CO 2 CC coupling occurs to give the carboxylated derivative [(phen)(Ph 3]P)CuO2CCH(CN) 2]( 2). Complex 2 can be obtained by bubbling CO 2 through solutions of 1. Complex 1 is readily formed when dinitrogen is bubbled through suspensions of 2 or when 2 is kept under vacuum at room temperature. Ethyl cyanoacetate reacts with A under an inert atmosphere to give [(phen)(Ph 3P)CuOC(OEt)CHCN] ( 3), and in the presence of carbon dioxide to give [(phen)(Ph 3P)CuO 2CCH(CN)(COOEt)] ( 4). The latter can be also obtained by the action of CO 2 on complex 3. The reaction of diethyl malonate with A gives the unexpected carboxylato complex [(phen)(Ph 3P)CuO 2CCH 2COOEt] ( 5) under nitrogen or under a carbon dioxide. A possible mechanism for formation of 5 is discussed.

Carboxylato complexes of zirconium(IV)

The preparation and thermal decomposition of several trifluoroacetatozirconium chlorides is described. A mechanism for the thermal decomposition is proposed and the formation of zirconium tetrafluoride discussed in terms of composition of the parent compound.

Thermal decomposition reactions of metal carboxylato complexes in the solid state. III. Thermographic and differential thermal studies of metal oxalato, malonato and succinato complexes

The thermal properties of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II), and non-transition metals, Zn(II) and Cd(II), in the solid state were studied under non-isothermal conditions in a nitrogen atmosphere by simultaneous TG and DTA. TG and DTA curves showed that the decomposition took place in single or multiple steps and thermal stability of the complex decreased, approximately, with the increase of the standard potential of the central metal ion. Thermodynamic parameters, such as activation energy, E ∗ a, enthalpy change, Δ H, and entropy change, Δ S, for dehydration and decomposition were determined from TG and DTA curves by standard methods. A linear correlation was found between Δ H and Δ S, and E ∗ a and Δ S, in dehydration and decomposition processes. An irreversible phase transition was observed for Li 2[Co(suc) 2] in the DTA curve. The residual products were mixtures of Li 2CO 3 and metal oxides except Li 2[Mn(ox) 2], Li 2[Zn(mal) 2] and Li 2 [Cd(mal) 2], where the final products were a mixture of Li 2O·MnO 2, Li 2CO 3·ZnCO 3 and Li 2CO 3·CdCO 3, respectively.

Thermal decomposition reactions of metal carboxylato complexes in the solid state: II. Thermographic and differential thermal studies of metal oxalato, malonato and succinato complexes

The thermal investigations of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non transition metals like Zn(II) and Cd(II) in solid state were carried out under non-isothermal condition in nitrogen atmopshere by thermogravimetric (TG) and differential thermal analyses (DTA) methods. The results of DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of standard potential of the central metal ion. The thermal parameters like activation energy ( E a ∗), enthalpy change (Δ H) and entropy change (Δ S) corresponding to deaquation, deammoniation and decomposition processes occurred simultaneously or separately were determined from TG and DTA curves by the standard methods. A linear correlation has been found in the plots of Δ H vs. Δ S and E a ∗ vs. Δ S in deaquation, deammoniation and decomposition processes. An irreversible phase transition was noticed for H 2[Mn(suc) 2] and H 2[Co(suc) 2] complexes in DTA curves. The residual pyrolysed products were metal carbonates.

An exploratory scandium-45 NMR study into the complexation of alanine and oligopeptides

The 87.5 MHz 45Sc NMR spectrum of 0.025 M aqueous Sc(NO 3) 3 exhibits two resonance signals, separated by ca. 25 ppm, attributable to [Sc(H 2O) 6] 3+ and [Sc(H 2O) 5OH] 2+. Acidification leads to a single, comparatively sharp line ( W 1/2 = 160 Hz) for the hexaqua complex, the temperature dependence (temperature gradient = 0.076 ppm/deg) of which indicates that relaxation is dominated by the quadrupole mechanism. Addition of α-alanine gives rise to an additional broad signal at ca. +70 ppm (relative to [Sc(H 2O) 6] 3+), which is assigned to a carboxylato complex [Sc(H 2O) 6−n(ala) n] 3+ or [Sc(H 2O) 5−nOH- (ala) n] 2+ (1 < n < 2). At ambient temperatures, these species are in slow exchange with the hexaqua and pentaqua-hydroxo complex, progressing through medium towards fast exchange as the temperature increases, and giving rise to an exchange contribution to relaxation. W 1/2 becomes a measure for the stability of the complexes, which increases in the order ala < (ala) 4 ∼ (ala) 2 < ala-val-leu. The pronounced stability of the latter is due to the formation of a chelate-five ring structure (participation of the NH- function of the peptide bond in coordination to Sc 3+). 1 M aqueous ScCl 3 probably contains the two species [Sc(H 2O) 6] 3+ and [Sc(H 2O) 5Cl] 2+, separated by 33 ppm.

Thermal decomposition reactions of metal carboxylato complexes in the solid state. I.: Thermographic and differential thermal studies of metal oxalato, malonato and succinato complexes

Thermal investigation of metal carboxylato complexes of the first transition metals, Mn(II), Fe(II), Fe(III), Co(II), Ni(II) and Cu(II) and non-transition metals like Zn(II) and Cd(II) in the solid state has been carried out under non-isothermal conditions in nitrogen atmosphere by simultaneous TG and DTA. TG and DTA curves inferred that the thermal stability of the complex decreased approximately with the increase of the standard potential of the central metal ion. The thermal parameters like activation energy, E ★ a, enthalpy change, Δ H, and entropy change, Δ S, corresponding to the dehydration and decomposition of the complexes are determined from TG and DTA curves by standard methods. A linear correlation is found between Δ H and Δ S and E ★ a and Δ S in dehydration and decomposition processes. DTA curves show an irreversible phase transition for Na 2Mn(mal) 2], Na 2[Cu(mal) 2] and Na 2,[Co(suc) 2] complexes. The residual products in these decomposition processes being a mixture of two oxides, of oxide and carbonate or a mixture of two carbonates.

Preparation, Characterization, and Some Reactions of Cationic Hydrido Carboxylato Complexes of Molybdenum(IV), [MoH2(O2CR)(dppe)2

Abstract Cationic carboxylatodihydridomolybdenum(IV) complexes, [MoH2(O2CR)(dppe)2]BPh4 (R=CH3, C2H5, CH2=CH, and CH2=C(CH3); dppe=Ph2PCH2CH2PPh2), were prepared by treating [MoH4(dppe)2] with RCOOH followed by anion exchange with NaBPh4, and characterized spectroscopically. A possible pathway of the reaction is discussed on the basis of the experiment using CH3COOD. Light irradiation of the EtOH solution of the cationic acetato complex in the presence and absence of CO afforded the known cis-[Mo(CO)2(dppe)2] and the neutral hydridoacetato complex, [MoH(O2CCH3)(dppe)2], respectively.

Carboxylato complexes of zirconium(IV) I: Trifluoroacetato complexes

The preparation and thermal decomposition of a trifluoroacetato complex of zirconium is described. A polymeric structure involving linked Zr 4(OH) 8 tetramers is proposed. A review of available IR spectroscopic data on trifluoroacetato complexes is presented.

Mechanisms of ligand-to-metal intramolecular electron transfer in cobalt(III)-amine complexes containing a coordinated radical

The one-electron reduction of Co(III) complexes containing nitrophenyl ligands possessing differing lead-in and bridging groups by radiolytically generated CO/sub 2//sup -/ and C(CH/sub 3/)/sub 2/OH radicals in neutral and acidic aqueous solution results in the formation of coordinated nitrophenyl ligand radicals. The uv-visible absorption spectra, the acid-base properties, and the decay kinetics of the transient intermediates were examined by pulse radiolysis. In neutral solution, the coordinated ligand radicals decay via intramolecular electron transfer from the coordinated nitrophenyl radical donor to the Co(III) acceptor. The values of the intramolecular electron-transfer rate constants depend on the isomeric position of the nitro group on the phenyl moiety, the structure of the bridging molecule between the redox sites, and the nature of the lead-in group to the metal center. Bridging structures between the initial radical site and the metal center of varying length, flexibility, and ..pi..-conjugation are incorporated into the 18 complexes studied. Correlation of the values of ..delta..H double dagger and ..delta..S double dagger of electron transfer with the structural relationship of the donor and acceptor sites leads to the proposition that four different mechanisms of intramolecular electron transfer operate in these complexes: through chain, direct and indirect ligand bypass, and nonadiabatic transfer.more » Protonation of the coordinated nitro radical greatly diminishes the rate of intramolecular electron transfer in the nitrophenol carboxylato complexes; in most cases, protonation affects only the driving force for electron transfer while leaving the mechanism unchanged. 37 references, 3 figures, 4 tables.« less

Kinetics of the displacement of chloroacetate ion from cis-bis(chloroacetato)bis(isopropylamine)platinum(II) and the (chloroacetato)(1,5-diamino-3-azapentane)platinum(II) cation

The displacement of ClCH2CO2– from cis-[Pt(PriNH2)2(ClCH2CO2)2] and [Pt(dien)(ClCH2CO2)]+(dien = 1,5-diamino-3-azapentane) by solvent, Cl–, Br–, and SCN– has been studied in aqueous solution at 25.0 °C. The reactions are catalysed by acid by way of a pre-equilibrium protonation of the carboxylate ligand. In the absence of added acid the cationic monocarboxylato complex exhibits a normal nucleophilic discrimination power, comparable to that of the corresponding chloro complex and the nucleophile-independent pathway makes only a small contribution to the consumption of the substrate. In the uncatalysed reactions of the bis(carboxylato) complex, the nucleophile-independent pathway dominates the substitution by the weak nucleophile, Cl–, and a relatively strong nucleophile, such as SCN–, is required to make the direct substitution pathway important. The unusually large contribution from the nucleophile-independent pathway is discussed.

Complexes of the platinum metals. Part 31. Reactions of binuclear ruthenium(II,III) and rhodium(II) carboxylates with chelating diphosphines;X-ray crystal structure of (acetato-O,O′)bis[bis(diphenylphosphino)methane-P,P′]ruthenium(II) tetraphenylborate

The chelating diphosphines Ph2P(CH2)nPPh2(n= 1–3) react with binuclear carboxylato complexes [Ru2(O2CR)4Cl](R = Me, Et, or Ph) in cold or refluxing benzene to yield products trans-[Ru(O2CR)2{Ph2P(CH2)nPPh2}2] and cis-[Ru(O2CR)2{Ph2P(CH2)nPPh2}2] respectively, both of which are readily converted to the tetraphenylborate salts [Ru(O2CR){Ph2P(CH2)nPPh2}2]BPh4. Attempts to obtain similar products using samples of [Ru2(O2CR)4Cl](R = CF3 or But), prepared from the corresponding acetate complex by treatment with the appropriate carboxylic acids under vigorous conditions, gave mixtures indicative of incomplete carboxylato exchange. The trans complexes [Ru(O2CR)2(Ph2PCH2PPh2)2] react with NaBH4 and CO to afford cis- and trans-[RuH2(Ph2PCH2PPh2)2] and cis,cis,trans-[ Ru(O2CR)2(CO)2(Ph2PCH2PPh2)2] respectively. The latter species react with NaBH4 to yield cis- and trans-[RuH2(CO)(Ph2PCH2PPh2)2]. Several of these products contain pendant Ph2PCH2PPh2 ligands. The corresponding complexes containing Ph2P(CH2)2PPh2 failed to carbonylate even under vigorous conditions. The relationship between chelate ring size and 31P n.m.r. parameters for some of these complexes is discussed. Confirmation that the cations contained in the tetraphenylborate salts are mononuclear and not, as previously suggested elsewhere, binuclear has been provided by an X-ray diffraction study of one such salt [Ru(O2CMe)(Ph2PCH2PPh2)2]BPh4. The crystals are triclinic, space group P(no. 2), with a= 14.693(5), b= 18.821(4), c= 11.807(3)A, α= 95.39(2), β= 108.03(2), γ= 92.43(2)°, and Z= 2 at 144(2) K. The complex contains tris(chelate)ruthenium(II) cations with bidentate acetate and bis(diphenylphosphino)methane ligands together with tetraphenylborate anions.

Synthesis, reactivity and x-ray crystal structures of mixed thiazolato- or carboxylato- carbonyl(phosphine) rhenium(I) complexes

The compound [Re(CO)3(PPh3)2Cl] reacts with the lithium salt of thiazole derivatives (L1H = 2-amino-benzothiazole, L2H = 2−N-methyl-aminothiazole, L3H = 2−N-phenylaminothiazole, L4H = 2−N-(4-methoxyphenyl)aminothiazole, L5H = 2−N(4-nitrophenyl)aminothiazole) to give [Re(CO)2-(PPh3)2(L)]. The compounds have been characterized by elemental analysis, i.r. and1H n.m.r. spectra. At room temperature [Re(CO)2(PPh3)(L2)] reacts with L6H (L6H = diphenylacetic acid), to give the carboxylato complex [Re(CO)2 .

Synthesis and Characterization of Some N-Benzoylglicinato Complexes of Chromium(III)

Abstract Tris(N-benzoylglycinato) chromium(III) has been prepared by the reaction of CrCl3.3THF and the sodium salt of N-benzoylglycine (hippuric acid, hipH) in 1:3 molar ratio in refluxing methanol. A number of its addition complexes with the general formula Cr(hip)3.xL (where L = EtOH, PriOH, ButOH, THF, py, pd, HexnNH2, 2,2′-bipy and x = 1 or 2) have been isolated by treating the chromium(III) hippurate with excess of the ligands under refluxing conditions. A few mixed (carboxylato) (N-benzoyl-glycinato) complexes of chromium(III) with the general formula Cr(OOCR)3-n(hip)n (where R = C13H27, C15H31, C17H35 and n=1 or 2) have also been synthesized. All the complexes have been characterized by elemental analyses, conductivity, molecular weight, infrared, electronic and e.s.r. spectra and magnetic susceptibility measurements, which indicate the bidentate nature of N-benzoylglycine in all the complexes with octahedral geometry around the chromium in the high spin (3d3) state.

Reactions of vanadocene-carbyls with carbon monoxide, xylylisocyanide and carbon dioxide

Vanadocene-allyl Cp 2V(η 1-C 3H 5) ( 1a) reacts with strong π-acceptor substrate ligands such as carbon monoxide, carbon dioxide and isonitriles. No reactions are observed with poorer π-acceptor substrates such as alkynes and nitriles. Reaction of 1a with CO gives Cp[η 4-C 5H 5)(C 3H 5)]V(CO) 2, showing that migration of the allylic ligand to one of the Cp rings has taken place. The reaction of 1a with 2,6-xylylisocyanide gave the very stable complex Cp 2V[η 1-C(C 3H 5)N-2,6-(CH 3) 2C 6H 3]. For other Cp 2VR (R = Me, Ph) compounds formation of this type of insertion product with an η 1-iminoacyl ligand was also observed. A carboxylato complex Cp 2V[η 1- OC(O)C 3H 5] was formed in the reaction of 1a with CO 2.

Asymmetric synthesis by chiral ruthenium complexes: XI. Asymmetric hydrogenation of tiglic acid in the presence of phosphine substituted ruthenium carbonyl carboxylates

The enantioface-discriminating hydrogenation of tiglic acid in the presence of (−)-DIOP substituted carbonyl carboxylato complexes of ruthenium has been investigated in order to identify the factors affecting the stereoselectivity of this reaction. The carboxylato ligand present in the catalytic intermediate does not seem to make a significant contribution to the stereoselectivity of this process. The stereoselectivity seems to be associated with the presence of the optically active phosphine. The catalytic system develops during the reaction through intermediates having a higher enantioface-discriminating activity than the initial and the final ruthenium complexes.