Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water... more Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water-methanol solvent, to yield compound [{Cp*Mo(-SCH2CO2)}2(-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo-S-Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs. The Mo-Mo distance of 2.792(7) Å indicates metal-metal bonding, in agreement with the compound diamagnetism.
Compound [Cp2∗Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water... more Compound [Cp2∗Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water–methanol solvent, to yield compound [{Cp*Mo(μ-SCH2CO2)}2(μ-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo–S–Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs.
Journal of Molecular Structure - J MOL STRUCT, 2008
The platinum complex [1,2-Fc(PPh2)(CH2SPh)]PtCl21 has been transformed into [1,2-Fc(PPh2)(CH2SPh)... more The platinum complex [1,2-Fc(PPh2)(CH2SPh)]PtCl21 has been transformed into [1,2-Fc(PPh2)(CH2SPh)]PtCl(SnCl3) 2 as a single isomer, in high yields, by reaction with SnCl2. The SnCl2 reagent inserts regioselectively in the PtCl bond trans to the sulphur atom, while the sulphur atom configuration is fully controlled by the planar chirality of the P,S ligand. Complex 1 has also been efficiently reduced in the presence of diphenylacetylene to a single isomer of [1,2-Fc(PPh2)(CH2SPh)]Pt(PhCCPh), 5, where the central chirality on sulphur is again maintained. In compound 5, the central CC bond of the diphenylacetylene moiety acquires a strong double bond character. The structures of complexes 1 and 5 have been determined by X-ray diffraction on monocrystals. To the best of our knowledge, this study presents the first example of fully characterized L2PtCl(SnCl3) and L2Pt(PhCCPh) complexes, L2 being a P,S ligand.
A new ferrocenyl P,O ligand has been synthesized and successfully used in the Suzuki-Miyaura coup... more A new ferrocenyl P,O ligand has been synthesized and successfully used in the Suzuki-Miyaura coupling reaction of phenylboronic acid with bromobenzene. Some analogues carrying charged (imidazolium) or neutral (monomethylether PEG 750, tetraethylbisphosphonate) polar substituents have been prepared by functionalization of a common synthetic intermediate easily obtained using bromoalcohol p-HOCH2(C6H4)CH2Br as bifunctional linker.
The preparation of several new molybdenum(VI) complexes containing Schiff base ligands tagged wit... more The preparation of several new molybdenum(VI) complexes containing Schiff base ligands tagged with sulfonate functionalities is presented. The title compounds have been characterized by standard analytical methods including NMR, IR, and mass spectroscopy. Xray structures of the N-salicylidene-2-aminophenolate dioxidomolybdenum complexes bearing sulfonato groups on the salicylidene moiety (as the sodium and ammonium salts) are described herein accompanied by the structural characterization of the N-salicylidene-2aminoethanolate sulfonate Schiff base ligand. The activity of the ionic catalysts for cyclooctene epoxidation is shown in different room temperature ionic liquids (i.e. [BMIM][NTf2] (NTf2-= (CF3SO2)2N-), [BMIM][CF3SO3], [EMIM][CH3C6H4SO3]).
... Ana M. Martins,* Carlos C. Romão,* Marta Abrantes, M. Cristina Azevedo, Jinlan Cui, ... more ... Ana M. Martins,* Carlos C. Romão,* Marta Abrantes, M. Cristina Azevedo, Jinlan Cui, Alberto R. Dias, M. Teresa Duarte, M. Amélia Lemos, § Tiago Lourenço, and Rinaldo Poli. Centro de Química Estrutural, Instituto ...
... Andrew D. Phillips, † Sandra Bolaño, † Sylvain S. Bosquain, † Jean-Claude Daran, ‡ Raluca Mal... more ... Andrew D. Phillips, † Sandra Bolaño, † Sylvain S. Bosquain, † Jean-Claude Daran, ‡ Raluca Malacea, ‡ Maurizio Peruzzini,* † Rinaldo Poli,* ‡ and Luca Gonsalvi* †. Consiglio Nazionale delle Ricerche, Istituto di Chimica dei ...
The molybdenum(III) coordination complexes MoX 3 (PMe 3) 3 (X = Cl, Br and I) are capable to cont... more The molybdenum(III) coordination complexes MoX 3 (PMe 3) 3 (X = Cl, Br and I) are capable to control styrene polymerization under typical atom transfer radical polymerization (ATRP) conditions, in conjunction with 2-bromoethylbenzene (BEB) as an initiator. The process is accelerated by the presence of Al(O-i-Pr) 3 as a co-catalyst. Electrochemical and synthetic studies aimed at identifying the nature of the spin trap have been carried out. The cyclic voltammogram of MoX 3 (PMe 3) 3 (X = Cl, Br, I) shows partial reversibility (increasing in the order Cl < Br < I) for the one-electron oxidation wave. Addition of Xchanges the voltammogram, indicating the formation of MoX 4 (PMe 3) 3 for X = Cl and Br. On the other hand, Iis more easily oxidized than the MoI 3 (PMe 3) 3 complex, thus the putative MoI 4 (PMe 3) 3 complex is redox unstable. Electrochemical studies of MoI 3 (PMe 3) 3 in the presence of X-(X = Cl or Br) reveal the occurrence of facile halide exchange processes, leading to the conclusion that the MoI 3 X(PMe 3) 3 products are also redox unstable. The oxidation of MoX 3 (PMe 3) 3 with ½ Br 2 yields MoX 3 Br(PMe 3) 3 (X = Cl, Br), whose molecular nature is confirmed by single crystal X-ray analyses. On the other hand, the oxidation of MoI 3 (PMe 3) 3 by I 2 slowly yields a tetraiodomolybdate(III) salt of iodotrimethylphosphonium, [Me 3 PI][MoI 4 (PMe 3) 3 ], as confirmed by an X-ray study. This product has no controlling ability in radical polymerization. The redox instability of MoI 3 X(PMe 3) 3 can be reconciled with its involvement as a radical trapping species in the MoI 3 (PMe 3) 3-catalyzed ATRP, given the second order nature of its decomposition rate.
Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water... more Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water-methanol solvent, to yield compound [{Cp*Mo(-SCH2CO2)}2(-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo-S-Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs. The Mo-Mo distance of 2.792(7) Å indicates metal-metal bonding, in agreement with the compound diamagnetism.
The reaction of Mo(CO) 3 (MeCN) 3 and E 2 Ph 2 (E= Se, Te) yields the edge-sharing bioctahedral, ... more The reaction of Mo(CO) 3 (MeCN) 3 and E 2 Ph 2 (E= Se, Te) yields the edge-sharing bioctahedral, metal metal bonded Mo(I) products [Mo(CO) 3 (MeCN)(m-EPh)] 2. The structure of the tellurolato derivative was confirmed by X-ray crystallography: triclinic,
A stopped-flow study of the Cp*MoO3protonation at low pH (down to zero) in a mixed H2O-MeOH (80:2... more A stopped-flow study of the Cp*MoO3protonation at low pH (down to zero) in a mixed H2O-MeOH (80:20) solvent at 25°C allows the simultaneous determination of the first acid dissociation constant of the oxo dihydroxo complex, [Cp*MoO(OH)2] + (pKa1 =-0.56), and the rate constant of its isomerization to the more stable dioxo aqua complex [Cp*MoO2(H2O)] + (k-2 = 28 s-1). Variable temperature (5-25°C) and variable pressure (10-130 MPa) kinetics studies have yielded the activation parameters for the combined protonation/isomerization process (k-2/Ka1) from Cp*MoO2(OH) to [Cp*MoO2(H2O)] + , viz. ΔH ‡ = 5.1 0.1 kcal mol-1 , ΔS ‡ =-37 1 cal mol-1 K-1 and ΔV ‡ =-9.1 0.2 cm 3 mol-1. Computational analysis of the two isomers, as well as the [Cp*MoO2] + complex resulting from the dissociation of water, reveal a crucial solvent effect on both the isomerization and the water dissociation energetics. Introducing a solvent model by CPCM and especially by explicitly including up to three water molecules in the calculations led to the stabilization of the dioxo aqua species relative to the oxo dihydroxo isomer, and to the substantial decrease of the energy cost for the water dissociation process. The presence of a water dissociation equilibrium is invoked to account for the unusually low effective acidity (pKa1' = 4.19) of the [Cp*MoO2(H2O)] + ion. In addition, the computational study reveals the positive role of external water molecules as simultaneous proton donors and acceptors, having the effect of dramatically lowering the isomerization energy barrier.
The tris(1‐pyrazolyl)methanesulfonate lithium salt Li(Tpms) [Tpms = SO3C(pz)3–] reacts with [Mo(C... more The tris(1‐pyrazolyl)methanesulfonate lithium salt Li(Tpms) [Tpms = SO3C(pz)3–] reacts with [Mo(CO)6] in NCMe heated at reflux to yield Li[Mo(Tpms)(CO)3] (1), which, upon crystallization from thf, forms the coordination polymer [Mo(Tpms)(CO)2(μ‐CO)Li(thf)2]n (2). Reaction of 1 with I2, HBF4 or AgBF4 yields [Mo(Tpms)I(CO)3] (3), [Mo(Tpms)H(CO)3] (5) or [Mo(Tpms)O2]2(μ‐O) (7), respectively. The high‐oxidation‐state dinuclear complexes [{Mo(Tpms)O(μ‐O)}2] (4) and [{Mo(tpms)OCl}2](μ‐O) (6) are formed upon exposure to air of solutions of 3 and 5, respectively. Compounds 1–7, which appear to be the first tris(pyrazolyl)methanesulfonate complexes of molybdenum to be reported, were characterized by IR, 1H and 13C NMR spectroscopy, ESI‐MS, elemental analysis, cyclic voltammetry and, in the cases of Li(Tpms) and compounds 2, 4·2CH3CN, 6·6CHCl3 and 7, by X‐ray diffraction analyses. Li(Tpms) forms a 1D polymeric structure {i.e., [Li(tpms)]n} with Tpms as a tetradentate N2O2 chelating ligand tha...
The reduction of [Cp*2Mo2O5] with Zn in a MeOH/H2O solution acidified with either CF3COOH or CF3S... more The reduction of [Cp*2Mo2O5] with Zn in a MeOH/H2O solution acidified with either CF3COOH or CF3SO3H leads to the formation of the [Cp*3Mo3(μ‐O)2(μ‐OH)4]2+ ion as its trifluoroacetate or trifluoromethanesulfonate salt. The structure of the compound was confirmed by X‐ray analyses. The anions establish hydrogen‐bonding interactions with all four bridging OH groups. Density functional calculations afford bonding parameters in close agreement with the observed structure and indicate that the cluster is best described as a valence‐delocalized Mo313+ species. The five metal electrons are distributed among an a‐type (z2) orbital, which accounts for most of the metal–metal attraction, and two essentially metal–metal nonbonding e‐type (xy) orbitals with a slight Mo‐(μ‐O) π*‐type contribution. Because of the C2 symmetry, the latter orbitals are not degenerate. The calculations show that the unpaired electron is located in a molecular orbital with equal contribution from two Mo atoms, in agre...
Complex MoOCl2(PMe3)3 smoothly reacts with NaI in acetone to produce MoOI2(PMe3)3 in good yields.... more Complex MoOCl2(PMe3)3 smoothly reacts with NaI in acetone to produce MoOI2(PMe3)3 in good yields. The geometry of the compound is mer‐cis octahedral, that is, identical to that of the dichloride precursor, as shown by NMR spectroscopy and by an X‐ray crystallographic study. Electrochemical investigations of MoOX2(PMe3)3 show irreversible oxidation waves at Ep,a = +0.18 and +0.39 V for X = Cl and I, respectively. A study of the halide exchange between MoOCl2(PMe3)3 and NaI, or between MoOI2(PMe3)3 and Bu4NCl, shows two equilibrated isomers for the mixed halide intermediate MoOICl(PMe3)3. The diiodide complex rapidly exchanges the iodo ligands with chloride upon dissolution in chloroform at room temperature, and with bromide from (1‐bromoethyl)benzene (BEB) under more forcing conditions. The equilibrium favors the softer halide (I) on C and the harder one (Cl or Br) on MoIV. Both oxido compounds catalyze the atom transfer radical polymerization (ATRP) of styrene in combination with th...
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Ir(CO)(CpFe(η 5-C5H3(PPh2)CH2SR)Cl [R = Ph and t Bu], containing a 2 :P,S ligand, undergoes H2 ... more Ir(CO)(CpFe(η 5-C5H3(PPh2)CH2SR)Cl [R = Ph and t Bu], containing a 2 :P,S ligand, undergoes H2 addition across the SIr CO axis under kinetic control to form two distinct diastereoisomeric products, which then rearrange via S dissociation in a process that can be hijacked for useful catalysis, but ultimately form a single diastereoisomer of the thermodynamic product where the hydride ligands are trans to chloride and phosphine.
Complexes Cp # Mo(PMe3)2H3 (Cp # = 1,2,4-C5H2tBu3, 2a; C5HiPr4, 2b) have been synthesized from th... more Complexes Cp # Mo(PMe3)2H3 (Cp # = 1,2,4-C5H2tBu3, 2a; C5HiPr4, 2b) have been synthesized from the corresponding compounds Cp # MoCl4 (1a, 1b) and fully characterized, including by X-ray crystallography and by a neutron diffraction study for 2a. Protonation of 2a led to complex [(1,2,4-C5H2tBu3)Mo(PMe3)2H4] + (3a) in THF and to [(1,2,4-C5H2 t Bu3)Mo(PMe3)2(MeCN)H2] + (4a) in MeCN. Complex 4b analogously derives from protonation of 2b in MeCN, whereas the tetrahydride complex 3b is unstable. One-electron oxidation of 2a and 2b by [Cp2Fe]PF6 produces the EPR active 17-electron complexes [2a] + and [2b] +. The former is thermally more stable than the latter and could be crystallographically characterized as the PF6salt by X-ray diffraction, providing evidence for the presence of a stretched dihydrogen ligand (H … H = 1.36(6) Å). Controlled thermal decomposition of [2a] + yielded the product of H2 elimination, the 15-electron monohydride complex [(1,2,4-C5H2tBu3)Mo(PMe3)2H]PF6 (5a) which was characterized by X-ray crystallography and by EPR spectroscopy at liquid He temperature. The compound establishes an equilibrium with the solvent adduct in THF. An electrochemical study by cyclic voltammetry provides further evidence for a rapid H2 elimination process from the 17electron complexes. Contrary to the previously investigated [Cp*Mo(dppe)H3] + system, the decomposition of [2a] + by H2 substitution with a solvent molecule appears to follow a dissociative pathway in MeCN.
A DFT analysis of the epoxidation of C2H4 by H2O2 and MeOOH (as models of tert‐butylhydroperoxide... more A DFT analysis of the epoxidation of C2H4 by H2O2 and MeOOH (as models of tert‐butylhydroperoxide, TBHP) catalyzed by [Cp*MoO2Cl] (1) in CHCl3 and by [Cp*MoO2(H2O)]+ in water is presented (Cp*=pentamethylcyclopentadienyl). The calculations were performed both in the gas phase and in solution with the use of the conductor‐like polarizable continuum model (CPCM). A low‐energy pathway has been identified, which starts with the activation of ROOH (R=H or Me) to form a hydro/alkylperoxido derivative, [Cp*MoO(OH)(OOR)Cl] or [Cp*MoO(OH)(OOR)]+ with barriers of 24.9 (26.5) and 28.7 (29.2) kcal mol−1 for H2O2 (MeOOH), respectively, in solution. The latter barrier, however, is reduced to only 1.0 (1.6) kcal mol−1 when one additional water molecule is explicitly included in the calculations. The hydro/alkylperoxido ligand in these intermediates is η2‐coordinated, with a significant interaction between the Mo center and the Oβ atom. The subsequent step is a nucleophilic attack of the ethylene m...
Three palladium(II) complexes and four platinum(II) complexes having general formula CpFe{1,2-C5H... more Three palladium(II) complexes and four platinum(II) complexes having general formula CpFe{1,2-C5H3(PPh2)(CH2SR)}MCl2 (M = Pd, R = Ph, Et and tBu; M = Pt, R = Ph, Et, tBu and Cy) have been synthesized by reaction of the corresponding CpFe{1,2-C5H3(PPh2)(CH2SR)} ligands with PdCl2(CH3CN)2 or PtCl2(CH3CN)2. These complexes have been fully characterized in solution and in solid state. In all cases, monomeric square planar complexes were obtained as pure diastereoisomers.
Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water... more Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water-methanol solvent, to yield compound [{Cp*Mo(-SCH2CO2)}2(-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo-S-Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs. The Mo-Mo distance of 2.792(7) Å indicates metal-metal bonding, in agreement with the compound diamagnetism.
Compound [Cp2∗Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water... more Compound [Cp2∗Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water–methanol solvent, to yield compound [{Cp*Mo(μ-SCH2CO2)}2(μ-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo–S–Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs.
Journal of Molecular Structure - J MOL STRUCT, 2008
The platinum complex [1,2-Fc(PPh2)(CH2SPh)]PtCl21 has been transformed into [1,2-Fc(PPh2)(CH2SPh)... more The platinum complex [1,2-Fc(PPh2)(CH2SPh)]PtCl21 has been transformed into [1,2-Fc(PPh2)(CH2SPh)]PtCl(SnCl3) 2 as a single isomer, in high yields, by reaction with SnCl2. The SnCl2 reagent inserts regioselectively in the PtCl bond trans to the sulphur atom, while the sulphur atom configuration is fully controlled by the planar chirality of the P,S ligand. Complex 1 has also been efficiently reduced in the presence of diphenylacetylene to a single isomer of [1,2-Fc(PPh2)(CH2SPh)]Pt(PhCCPh), 5, where the central chirality on sulphur is again maintained. In compound 5, the central CC bond of the diphenylacetylene moiety acquires a strong double bond character. The structures of complexes 1 and 5 have been determined by X-ray diffraction on monocrystals. To the best of our knowledge, this study presents the first example of fully characterized L2PtCl(SnCl3) and L2Pt(PhCCPh) complexes, L2 being a P,S ligand.
A new ferrocenyl P,O ligand has been synthesized and successfully used in the Suzuki-Miyaura coup... more A new ferrocenyl P,O ligand has been synthesized and successfully used in the Suzuki-Miyaura coupling reaction of phenylboronic acid with bromobenzene. Some analogues carrying charged (imidazolium) or neutral (monomethylether PEG 750, tetraethylbisphosphonate) polar substituents have been prepared by functionalization of a common synthetic intermediate easily obtained using bromoalcohol p-HOCH2(C6H4)CH2Br as bifunctional linker.
The preparation of several new molybdenum(VI) complexes containing Schiff base ligands tagged wit... more The preparation of several new molybdenum(VI) complexes containing Schiff base ligands tagged with sulfonate functionalities is presented. The title compounds have been characterized by standard analytical methods including NMR, IR, and mass spectroscopy. Xray structures of the N-salicylidene-2-aminophenolate dioxidomolybdenum complexes bearing sulfonato groups on the salicylidene moiety (as the sodium and ammonium salts) are described herein accompanied by the structural characterization of the N-salicylidene-2aminoethanolate sulfonate Schiff base ligand. The activity of the ionic catalysts for cyclooctene epoxidation is shown in different room temperature ionic liquids (i.e. [BMIM][NTf2] (NTf2-= (CF3SO2)2N-), [BMIM][CF3SO3], [EMIM][CH3C6H4SO3]).
... Ana M. Martins,* Carlos C. Romão,* Marta Abrantes, M. Cristina Azevedo, Jinlan Cui, ... more ... Ana M. Martins,* Carlos C. Romão,* Marta Abrantes, M. Cristina Azevedo, Jinlan Cui, Alberto R. Dias, M. Teresa Duarte, M. Amélia Lemos, § Tiago Lourenço, and Rinaldo Poli. Centro de Química Estrutural, Instituto ...
... Andrew D. Phillips, † Sandra Bolaño, † Sylvain S. Bosquain, † Jean-Claude Daran, ‡ Raluca Mal... more ... Andrew D. Phillips, † Sandra Bolaño, † Sylvain S. Bosquain, † Jean-Claude Daran, ‡ Raluca Malacea, ‡ Maurizio Peruzzini,* † Rinaldo Poli,* ‡ and Luca Gonsalvi* †. Consiglio Nazionale delle Ricerche, Istituto di Chimica dei ...
The molybdenum(III) coordination complexes MoX 3 (PMe 3) 3 (X = Cl, Br and I) are capable to cont... more The molybdenum(III) coordination complexes MoX 3 (PMe 3) 3 (X = Cl, Br and I) are capable to control styrene polymerization under typical atom transfer radical polymerization (ATRP) conditions, in conjunction with 2-bromoethylbenzene (BEB) as an initiator. The process is accelerated by the presence of Al(O-i-Pr) 3 as a co-catalyst. Electrochemical and synthetic studies aimed at identifying the nature of the spin trap have been carried out. The cyclic voltammogram of MoX 3 (PMe 3) 3 (X = Cl, Br, I) shows partial reversibility (increasing in the order Cl < Br < I) for the one-electron oxidation wave. Addition of Xchanges the voltammogram, indicating the formation of MoX 4 (PMe 3) 3 for X = Cl and Br. On the other hand, Iis more easily oxidized than the MoI 3 (PMe 3) 3 complex, thus the putative MoI 4 (PMe 3) 3 complex is redox unstable. Electrochemical studies of MoI 3 (PMe 3) 3 in the presence of X-(X = Cl or Br) reveal the occurrence of facile halide exchange processes, leading to the conclusion that the MoI 3 X(PMe 3) 3 products are also redox unstable. The oxidation of MoX 3 (PMe 3) 3 with ½ Br 2 yields MoX 3 Br(PMe 3) 3 (X = Cl, Br), whose molecular nature is confirmed by single crystal X-ray analyses. On the other hand, the oxidation of MoI 3 (PMe 3) 3 by I 2 slowly yields a tetraiodomolybdate(III) salt of iodotrimethylphosphonium, [Me 3 PI][MoI 4 (PMe 3) 3 ], as confirmed by an X-ray study. This product has no controlling ability in radical polymerization. The redox instability of MoI 3 X(PMe 3) 3 can be reconciled with its involvement as a radical trapping species in the MoI 3 (PMe 3) 3-catalyzed ATRP, given the second order nature of its decomposition rate.
Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water... more Compound [Cp*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water-methanol solvent, to yield compound [{Cp*Mo(-SCH2CO2)}2(-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo-S-Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs. The Mo-Mo distance of 2.792(7) Å indicates metal-metal bonding, in agreement with the compound diamagnetism.
The reaction of Mo(CO) 3 (MeCN) 3 and E 2 Ph 2 (E= Se, Te) yields the edge-sharing bioctahedral, ... more The reaction of Mo(CO) 3 (MeCN) 3 and E 2 Ph 2 (E= Se, Te) yields the edge-sharing bioctahedral, metal metal bonded Mo(I) products [Mo(CO) 3 (MeCN)(m-EPh)] 2. The structure of the tellurolato derivative was confirmed by X-ray crystallography: triclinic,
A stopped-flow study of the Cp*MoO3protonation at low pH (down to zero) in a mixed H2O-MeOH (80:2... more A stopped-flow study of the Cp*MoO3protonation at low pH (down to zero) in a mixed H2O-MeOH (80:20) solvent at 25°C allows the simultaneous determination of the first acid dissociation constant of the oxo dihydroxo complex, [Cp*MoO(OH)2] + (pKa1 =-0.56), and the rate constant of its isomerization to the more stable dioxo aqua complex [Cp*MoO2(H2O)] + (k-2 = 28 s-1). Variable temperature (5-25°C) and variable pressure (10-130 MPa) kinetics studies have yielded the activation parameters for the combined protonation/isomerization process (k-2/Ka1) from Cp*MoO2(OH) to [Cp*MoO2(H2O)] + , viz. ΔH ‡ = 5.1 0.1 kcal mol-1 , ΔS ‡ =-37 1 cal mol-1 K-1 and ΔV ‡ =-9.1 0.2 cm 3 mol-1. Computational analysis of the two isomers, as well as the [Cp*MoO2] + complex resulting from the dissociation of water, reveal a crucial solvent effect on both the isomerization and the water dissociation energetics. Introducing a solvent model by CPCM and especially by explicitly including up to three water molecules in the calculations led to the stabilization of the dioxo aqua species relative to the oxo dihydroxo isomer, and to the substantial decrease of the energy cost for the water dissociation process. The presence of a water dissociation equilibrium is invoked to account for the unusually low effective acidity (pKa1' = 4.19) of the [Cp*MoO2(H2O)] + ion. In addition, the computational study reveals the positive role of external water molecules as simultaneous proton donors and acceptors, having the effect of dramatically lowering the isomerization energy barrier.
The tris(1‐pyrazolyl)methanesulfonate lithium salt Li(Tpms) [Tpms = SO3C(pz)3–] reacts with [Mo(C... more The tris(1‐pyrazolyl)methanesulfonate lithium salt Li(Tpms) [Tpms = SO3C(pz)3–] reacts with [Mo(CO)6] in NCMe heated at reflux to yield Li[Mo(Tpms)(CO)3] (1), which, upon crystallization from thf, forms the coordination polymer [Mo(Tpms)(CO)2(μ‐CO)Li(thf)2]n (2). Reaction of 1 with I2, HBF4 or AgBF4 yields [Mo(Tpms)I(CO)3] (3), [Mo(Tpms)H(CO)3] (5) or [Mo(Tpms)O2]2(μ‐O) (7), respectively. The high‐oxidation‐state dinuclear complexes [{Mo(Tpms)O(μ‐O)}2] (4) and [{Mo(tpms)OCl}2](μ‐O) (6) are formed upon exposure to air of solutions of 3 and 5, respectively. Compounds 1–7, which appear to be the first tris(pyrazolyl)methanesulfonate complexes of molybdenum to be reported, were characterized by IR, 1H and 13C NMR spectroscopy, ESI‐MS, elemental analysis, cyclic voltammetry and, in the cases of Li(Tpms) and compounds 2, 4·2CH3CN, 6·6CHCl3 and 7, by X‐ray diffraction analyses. Li(Tpms) forms a 1D polymeric structure {i.e., [Li(tpms)]n} with Tpms as a tetradentate N2O2 chelating ligand tha...
The reduction of [Cp*2Mo2O5] with Zn in a MeOH/H2O solution acidified with either CF3COOH or CF3S... more The reduction of [Cp*2Mo2O5] with Zn in a MeOH/H2O solution acidified with either CF3COOH or CF3SO3H leads to the formation of the [Cp*3Mo3(μ‐O)2(μ‐OH)4]2+ ion as its trifluoroacetate or trifluoromethanesulfonate salt. The structure of the compound was confirmed by X‐ray analyses. The anions establish hydrogen‐bonding interactions with all four bridging OH groups. Density functional calculations afford bonding parameters in close agreement with the observed structure and indicate that the cluster is best described as a valence‐delocalized Mo313+ species. The five metal electrons are distributed among an a‐type (z2) orbital, which accounts for most of the metal–metal attraction, and two essentially metal–metal nonbonding e‐type (xy) orbitals with a slight Mo‐(μ‐O) π*‐type contribution. Because of the C2 symmetry, the latter orbitals are not degenerate. The calculations show that the unpaired electron is located in a molecular orbital with equal contribution from two Mo atoms, in agre...
Complex MoOCl2(PMe3)3 smoothly reacts with NaI in acetone to produce MoOI2(PMe3)3 in good yields.... more Complex MoOCl2(PMe3)3 smoothly reacts with NaI in acetone to produce MoOI2(PMe3)3 in good yields. The geometry of the compound is mer‐cis octahedral, that is, identical to that of the dichloride precursor, as shown by NMR spectroscopy and by an X‐ray crystallographic study. Electrochemical investigations of MoOX2(PMe3)3 show irreversible oxidation waves at Ep,a = +0.18 and +0.39 V for X = Cl and I, respectively. A study of the halide exchange between MoOCl2(PMe3)3 and NaI, or between MoOI2(PMe3)3 and Bu4NCl, shows two equilibrated isomers for the mixed halide intermediate MoOICl(PMe3)3. The diiodide complex rapidly exchanges the iodo ligands with chloride upon dissolution in chloroform at room temperature, and with bromide from (1‐bromoethyl)benzene (BEB) under more forcing conditions. The equilibrium favors the softer halide (I) on C and the harder one (Cl or Br) on MoIV. Both oxido compounds catalyze the atom transfer radical polymerization (ATRP) of styrene in combination with th...
HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
Ir(CO)(CpFe(η 5-C5H3(PPh2)CH2SR)Cl [R = Ph and t Bu], containing a 2 :P,S ligand, undergoes H2 ... more Ir(CO)(CpFe(η 5-C5H3(PPh2)CH2SR)Cl [R = Ph and t Bu], containing a 2 :P,S ligand, undergoes H2 addition across the SIr CO axis under kinetic control to form two distinct diastereoisomeric products, which then rearrange via S dissociation in a process that can be hijacked for useful catalysis, but ultimately form a single diastereoisomer of the thermodynamic product where the hydride ligands are trans to chloride and phosphine.
Complexes Cp # Mo(PMe3)2H3 (Cp # = 1,2,4-C5H2tBu3, 2a; C5HiPr4, 2b) have been synthesized from th... more Complexes Cp # Mo(PMe3)2H3 (Cp # = 1,2,4-C5H2tBu3, 2a; C5HiPr4, 2b) have been synthesized from the corresponding compounds Cp # MoCl4 (1a, 1b) and fully characterized, including by X-ray crystallography and by a neutron diffraction study for 2a. Protonation of 2a led to complex [(1,2,4-C5H2tBu3)Mo(PMe3)2H4] + (3a) in THF and to [(1,2,4-C5H2 t Bu3)Mo(PMe3)2(MeCN)H2] + (4a) in MeCN. Complex 4b analogously derives from protonation of 2b in MeCN, whereas the tetrahydride complex 3b is unstable. One-electron oxidation of 2a and 2b by [Cp2Fe]PF6 produces the EPR active 17-electron complexes [2a] + and [2b] +. The former is thermally more stable than the latter and could be crystallographically characterized as the PF6salt by X-ray diffraction, providing evidence for the presence of a stretched dihydrogen ligand (H … H = 1.36(6) Å). Controlled thermal decomposition of [2a] + yielded the product of H2 elimination, the 15-electron monohydride complex [(1,2,4-C5H2tBu3)Mo(PMe3)2H]PF6 (5a) which was characterized by X-ray crystallography and by EPR spectroscopy at liquid He temperature. The compound establishes an equilibrium with the solvent adduct in THF. An electrochemical study by cyclic voltammetry provides further evidence for a rapid H2 elimination process from the 17electron complexes. Contrary to the previously investigated [Cp*Mo(dppe)H3] + system, the decomposition of [2a] + by H2 substitution with a solvent molecule appears to follow a dissociative pathway in MeCN.
A DFT analysis of the epoxidation of C2H4 by H2O2 and MeOOH (as models of tert‐butylhydroperoxide... more A DFT analysis of the epoxidation of C2H4 by H2O2 and MeOOH (as models of tert‐butylhydroperoxide, TBHP) catalyzed by [Cp*MoO2Cl] (1) in CHCl3 and by [Cp*MoO2(H2O)]+ in water is presented (Cp*=pentamethylcyclopentadienyl). The calculations were performed both in the gas phase and in solution with the use of the conductor‐like polarizable continuum model (CPCM). A low‐energy pathway has been identified, which starts with the activation of ROOH (R=H or Me) to form a hydro/alkylperoxido derivative, [Cp*MoO(OH)(OOR)Cl] or [Cp*MoO(OH)(OOR)]+ with barriers of 24.9 (26.5) and 28.7 (29.2) kcal mol−1 for H2O2 (MeOOH), respectively, in solution. The latter barrier, however, is reduced to only 1.0 (1.6) kcal mol−1 when one additional water molecule is explicitly included in the calculations. The hydro/alkylperoxido ligand in these intermediates is η2‐coordinated, with a significant interaction between the Mo center and the Oβ atom. The subsequent step is a nucleophilic attack of the ethylene m...
Three palladium(II) complexes and four platinum(II) complexes having general formula CpFe{1,2-C5H... more Three palladium(II) complexes and four platinum(II) complexes having general formula CpFe{1,2-C5H3(PPh2)(CH2SR)}MCl2 (M = Pd, R = Ph, Et and tBu; M = Pt, R = Ph, Et, tBu and Cy) have been synthesized by reaction of the corresponding CpFe{1,2-C5H3(PPh2)(CH2SR)} ligands with PdCl2(CH3CN)2 or PtCl2(CH3CN)2. These complexes have been fully characterized in solution and in solid state. In all cases, monomeric square planar complexes were obtained as pure diastereoisomers.
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