M. Angeles Alvarez

University of Oviedo, Oviedo, Asturias, Spain

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Publications (91)414.1 Total impact

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    ABSTRACT: Complex [Mo2Cp2(μ-PCy2)(μ-NO)(NO)2] (1) was prepared by reacting [Mo2Cp2(μ-H)(μ-PCy2)(CO)4] with 2 equiv of [NO]BF4 and then treating the resulting product [Mo2Cp2(μ-PCy2)(CO)2(NO)2](BF4) with NaNO2 at 323 K, and it was shown to display a bridging nitrosyl ligand with significant pyramidalization at the N atom, a circumstance related to an unusual behavior concerning degradation of the bridging nitrosyl. Indeed, complex 1 reacts with HBF4·OEt2 to give the nitroxyl-bridged derivative [Mo2Cp2(μ-PCy2)(μ-κ(1):η(2)-HNO)(NO)2](BF4), is reduced by Zn(Hg) in the presence of trace H2O to give the amido complex [Mo2Cp2(μ-PCy2)(μ-NH2)(NO)2], and reacts with excess P(OPh)3 to give the phosphoraniminato-bridged derivative [Mo2Cp2(μ-PCy2){μ-NP(OPh)3}(NO)2].
    No preview · Article · Nov 2015 · Inorganic Chemistry
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    Full-text · Dataset · Oct 2015
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    ABSTRACT: The title phosphinidene complex could be sequentially protonated with HBF4·OEt2 or [H(OEt2)2](BAr'4) to give the phosphido-bridged derivatives [Mo2Cp(μ-κ(1):κ(1),η(5)-HPC5H4)(η(6)-HMes*)(CO)2(PMe3)]X and then the hydrides [Mo2Cp(H)(μ-κ(1):κ(1),η(5)-HPC5H4)(η(6)-HMes*)(CO)2(PMe3)]X2 (X = BF4, BAr'4; Ar' = 3,5-C6H3(CF3)2; Mes* = 2,4,6-C6H2(t)Bu3). Density functional theory (DFT) calculations revealed that the most favored site for initial electrophilic attack is the metallocene Mo atom, but attachment of the electrophile to the phosphinidene P atom gives more stable products. This was in agreement with all other reactions investigated, which invariably involved the attachment of the added electrophile at the P site. Thus, the title compound reacted with S8 at 223 K to give the thiophosphinidene-bridged complex [Mo2Cp{μ-κ(1):κ(1),η(5)-P(S)C5H4}(η(6)-HMes*)(CO)2(PMe3)], a poorly stable molecule which reacted with MeI at room temperature to give the corresponding thiolatophosphido derivative, isolated as [Mo2Cp{μ-κ(1):κ(1),η(5)-P(SMe)C5H4}(η(6)-HMes*)(CO)2(PMe3)](BAr'4) (P-S = 2.128(4) Å) after anion exchange with Na(BAr'4). Reaction of the title compound with MeI proceeded smoothly to give the corresponding methylphosphido derivative, isolated analogously as [Mo2Cp{μ-κ(1):κ(1),η(5)-P(Me)C5H4}(η(6)-HMes*)(CO)2(PMe3)](BAr'4). The related complex [Mo2Cp{μ-κ(1):κ(1),η(5)-P(Me)C5H4}(η(6)-HMes*)(CO)2(PMe2Ph)](BAr'4) (P-C(Me) = 1.841(5) Å) could be prepared analogously from the neutral precursor [Mo2Cp{μ-κ(1):κ(1),η(5)-PC5H4}(η(6)-HMes*)(CO)2(PMe2Ph)]. In contrast, reaction of the title complex with ethylene sulfide involved opening of the C2S ring and formation of new P-C and Mo-S bonds (1.886(7) and 2.493(2) Å, respectively), with displacement of the PMe3 ligand, to give the phosphido-thiolato complex [Mo2Cp{μ-κ(2)P,S:κ(1)P,η(5)-P(C2H4S)C5H4}(η(6)-HMes*)(CO)2]. All these derivatives of the title complex displayed an unusual trigonal pyramidal-like environment around the bridging P atom, with the added electrophile placed in the Mo2P plane as a result of the directionality of the relevant frontier orbital of the phosphinidene complex, according to DFT calculations.
    Full-text · Article · Oct 2015 · Inorganic Chemistry
  • M. Ángeles Alvarez · M.Esther García · Sonia Menéndez · Miguel A. Ruiz
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    ABSTRACT: The carbonyl-bridged complex [Mo2Cp2(μ-CPh) (μ-PCy2) (μ-CO)] (1) reacted with [Fe2(CO)9] at room temperature to give the 46-electron trinuclear cluster [FeMo2Cp2(μ3-CPh) (μ-PCy2) (CO)5] (Mo-Mo = 2.6782(4) Å), and a similar Mo2Ru cluster was obtained upon reaction with [Ru3(CO)12] under irradiation with visible-UV light (Cp = η5-C5H5). Compound 1 reacted with [Co2(CO)8] at room temperature to give the 60-electron tetrahedral cluster [Co2Mo2Cp2(μ3-CPh) (μ-PCy2) (CO)7], which in solution exits as an equilibrium mixture of two isomers and presumably displays phosphide and carbyne ligands in a cisoid arrangement. This compound evolved thermally to give a third isomer having these ligands arranged in a transoid way (P-Mo-C = 126.3(1)o, Mo-Mo = 2.9612(6) Å). The dicarbonyl complex [Mo2Cp2(μ-CPh) (μ-PCy2) (CO)2] (2) reacted with W(CO)6 under visible-UV light irradiation to give two thermally unstable isomers of the 46-electron trinuclear cluster [Mo2WCp2(μ3-CPh) (μ-PCy2) (CO)6]. Reaction of 2 with [AuCl(PR3)] (R = Me, p-tol, iPr) in the presence of TlPF6 gave first the corresponding cationic clusters trans-[AuMo2Cp2(μ3-CPh) (μ-PCy2) (CO)2(PR3)]PF6, which then evolved thermally to the more stable isomers cis-[AuMo2Cp2(μ3-CPh) (μ-PCy2) (CO)2(PR3)]PF6 (Mo-Mo = 2.810(1) Å for R = iPr), selectively formed with a syn conformation of the carbyne and Cp ligands, except for the PMe3 complex. In contrast, reaction of 2 with CuCl led to a cluster of composition [CuMo2ClCp2(μ3-CPh) (μ-PCy2) (CO)2], presumably present as a monomer in solution, but certainly appearing in the solid state as a centrosymmetric dimer held by bridging Cu-Cl-Cu interactions (Mo-Mo = 2.8004(5), Cu-Cl = 2.309(1), 2.409(1) Å).
    No preview · Article · Sep 2015 · Journal of Organometallic Chemistry
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    ABSTRACT: Reaction of the Li+ salt of the title anion with [Fe2(CO)9] or tetrahydrofuran adducts of formula [MLn(THF)] gave the trinuclear species Li[Mo2MCp2(μ-PCy2)(μ-κ2:κ2:κ1-P2)(CO)2Ln], (MLn = Fe(CO)4, MnCp′(CO)2, Mo(CO)5, W(CO)5; Cp′ = η5-C5H4Me), some of which could be isolated as the corresponding PPN+ salts (PPN = N(PPh3)2). These products followed from further coordination of the P2 ligand to the incoming 16-electron MLn fragment via the lone electron pair at its basal P atom, and displayed characteristically high P–P couplings (1JPP ca. 500 Hz) indicative of retention of a strong P–P bond. In addition, these products underwent a fluxional process derived from the swing of the P2 unit around the Mo–Mo axis with concomitant exchange of the MLn fragment between P atoms. Reaction of the title anion with excess of the above carbonyl complexes involved further addition of a second MLn fragment to the P atom still bearing a lone electron pair, thus leading to the tetranuclear anionic derivatives Li[Mo2M2Cp2(μ-PCy2)(μ-κ2:κ2:κ1:κ1-P2)(CO)2L2n], most of which could be isolated as the corresponding PPN+ salts. For the Mo and W derivatives, this reaction also involved a trans to cis isomerisation at the Mo2(CO)2 moiety of the parent anion. All tetranuclear anions displayed fluxional behaviour in solution, comparable to that of the parent anion in the case of the Fe and Mn derivatives, but likely involving rotation of the P2 ligand in the case of the cisoid Mo and W derivatives. Protonation of the above trinuclear anions with [NH4]PF6 led to decomposition except for the Mn complex, this yielding a poorly characterized diphosphenyl derivative [MnMo2Cp2Cp′(μ-κ1,η2:κ2:κ1-HP2)(μ-PCy2)(CO)4] displaying an agostic-like P–H–Mo interaction, eventually decomposing to the known phosphide-bridged complex [MnMo2Cp2Cp′(μ3-P)(μ-PCy2)(CO)4]. In contrast, protonation of the tetranuclear anions yielded the unsaturated hydride derivatives [Mo2M2Cp2(H)(μ-PCy2)(μ-κ2:κ2:κ1:κ1-P2)(CO)L2n], (M = Mn, Mo, W), with a formal intermetallic double bond (Mo–Mo = 2.7412(6) Å for the tungsten complex) as a result of loss of a CO ligand from the Mo2(CO)2 moiety after protonation, probably favoured by the presence of excess of adducts [MLn(THF)] in these reaction mixtures.
    No preview · Article · Aug 2015 · Journal of Organometallic Chemistry
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    ABSTRACT: The title compound reacted rapidly with N2CH(SiMe3) at room temperature to give the electron-precise hydride [W2Cp2(H)(μ-PCy2)(CO)2{N-N2CH(SiMe3)}] (W–W = 2.9907(5) Å), in which the diazoalkane molecule is N-bound strongly to one of the metal centers, formally acting as an imido-like four-electron donor. Reaction with N2CPh2 led instead to a mixture of two products, the analogous diphenyldiazomethane complex [W2Cp2(H)(μ-PCy2)(CO)2(N-N2CPh2)] and the bis(diazoalkane) derivative [W2Cp2(H)(μ-PCy2)(CO)2(N-N2CPh2)2], the latter having no metal–metal bond and bearing two inequivalent diazoalkane ligands bound to the same metal center (W–N = 1.78(1), 1.82(1) Å), whereas its dicarbonyl metal fragment displays a transoid geometry in the crystal, but a cisoid one in solution. These two compounds follow from competitive reaction pathways, since independent experiments revealed that the above mono(diazoalkane) complexes did not add a second diazoalkane molecule even under thermal activation. In contrast, the title compound reacted with excess N2CH2 to yield two new methyl derivatives requiring the participation of two molecules of reagent, the diazomethane complex [W2Cp2(CH3)(μ-PCy2)(CO)2(N-N2CH2)] and the 30-electron phosphinomethyl-bridged complex [W2Cp2(CH3)(μ-C:P-CH2PCy2)(μ-CO)(CO)], along with small amounts of the known methyl-bridged complex [W2Cp2(μ-CH3)(μ-PCy2)(CO)2]. The two new complexes follow from denitrogenation of one diazomethane molecule followed by insertion of methylene into the W–H bond to yield a methyl ligand, while the second diazomethane molecule either remains bound through its nitrogen atom or undergoes denitrogenation followed by insertion of methylene into a W–P bond, to yield a phosphinomethyl ligand. Once more, no denitrogenation of the coordinated diazomethane ligand in the first complex was observed even under thermal or photochemical activation.
    No preview · Article · Jul 2015 · Organometallics
  • Belén Alvarez · M Angeles Alvarez · M Esther García · Miguel A Ruiz
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    ABSTRACT: The thiophosphinidene complex [Mo2Cp2(μ-κ(2):κ(1),η(6)-SPMes*)(CO)2] (Mes* = 2,4,6-C6H2(t)Bu3) reacted with [Co2(CO)8] at room temperature or below to give several of the following phosphinidene-bridged products, depending on reaction conditions: the MoCo complexes [CoMoCp(μ-κ(1):κ(1),η(6)-PMes*)(CO)3] and [CoMoCp(μ-PMes*)(CO)5] (Co-Mo = 2.972(1) Å), the MoCo3 cluster [Co3MoCp(μ3-PMes*)(CO)9] (Co-Mo = 2.664(1), 2.810(1) Å), and the sulphido-bridged tetranuclear complexes [Co2Mo2Cp2(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)7] and [Co3MoCp(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)8]. In contrast, the thiophosphinidene complex [Mo2Cp2(μ-κ(2):κ(1),η(4)-SPMes*)(CO)3] reacted with the same cobalt reagent selectively to give the above Mo2Co2 complex in very high yield. The latter could be decarbonylated photochemically to give [Co2Mo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PMes*)(μ3-S)(CO)6] (Co-Co = 2.435(3), Co-Mo = 2.769(2), 2.798(2) Å), after an η(4)- to η(6)-haptotropic rearrangement of the aryl ring of the phosphinidene ligand that could be reversed upon reaction with CO. The related complex [Mo2Cp2(μ-κ(2):κ(1),η(4)-SPMes*)(CO)2(CN(t)Bu)], however, displayed poor selectivity towards the cobalt dimer and yielded a mixture of CoMo complexes [CoMoCp(μ-PMes*)(CO)5] and [CoMoCp(μ-PMes*)(CO)3(CN(t)Bu)2], and the tetranuclear sulphido-bridged ones [Co2Mo2Cp2(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)6(CN(t)Bu)] (Co-Co = 2.533(1), Co-Mo = 2.7485(9), 2.770(1) Å) and [Co3MoCp(μ-κ(1):κ(1):κ(1),η(4)-PMes*)(μ3-S)(CO)7(CN(t)Bu)] (Co-Co = 2.4120(7) to 2.5817(7) Å). This reduction in selectivity might have an electronic origin rather than a steric origin, since the related but cationic substrate [Mo2Cp2{μ-κ(2):κ(1),η(5)-SP(C6H3(t)Bu3)}(CO)2(CN(t)Bu)]BAr [Ar' = 3,5-C6H3(CF3)2] reacted with [Co2(CO)8] more selectively to give the sulphido-bridged Co2Mo2 complex [Co2Mo2Cp2{μ-κ(1):κ(1):κ(1),η(5)-P(C6H3(t)Bu3)}(μ3-S)(CO)6(CN(t)Bu)]BAr, along with small amounts of the Co3Mo complex [Co3MoCp{μ-κ(1):κ(1):κ(1),η(5)-P(C6H3(t)Bu3)}(μ3-S)(CO)7(CN(t)Bu)]BAr (Co-Co = 2.414(2) to 2.560(2) Å). The structure of the new complexes was analyzed on the basis of the corresponding X-ray diffraction and spectroscopic data, and likely reaction pathways were discussed on the basis of the above results and some additional experiments.
    No preview · Article · Jun 2015 · Dalton Transactions
  • M. Angeles Alvarez · M. Esther García · Sonia Menéndez · Miguel A. Ruiz
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    ABSTRACT: The unsaturated methoxycarbyne complex [Mo2Cp2(μ-COMe)(μ-CPh)(μ-PCy2)](CF3SO3) (Cp = η5-C5H5; Mo-Mo = 2.4707(3) Å) reacted with CO (293 K, 40 bar) or CNR (233 K, R = tBu, Xyl) to give the corresponding methoxyalkyne-bridged derivatives [Mo2Cp2{μ-η2:η2-C(OMe)CPh}(μ-PCy2)L2](CF3SO3) following from a reductive C-C coupling between methoxycarbyne and benzylidyne ligands (L = CO, CNR). This coupling could be fully reversed for the dicarbonyl product upon photolysis in tetrahydrofuran solution. The related hydroxycarbyne complex [Mo2Cp2(μ-COH)(μ-CPh)(μ-PCy2)]BF4 reacted analogously with CO (293 K, 4 bar) to give the hydroxyalkyne-bridged derivative [Mo2Cp2{μ-η2:η2-C(OH)CPh}(μ-PCy2)(CO)2]BF4 (Mo-Mo = 2.6572(5) Å) as a result of C-C coupling between hydroxycarbyne and benzylidyne ligands, but this process could not be reversed photochemically. The latter complex could be prepared more efficiently via protonation of the ketenyl precursor [Mo2Cp2{μ-C(Ph)CO}(μ-PCy2)(CO)2] with HBF4·OEt2 in dichloromethane solution. The hydroxycarbyne complex also reacted with CNtBu and CNXyl to give C-C coupled products, but different than anticipated: in both cases this reaction yielded selectively the corresponding aminoalkyne-bridged derivatives [Mo2Cp2{μ-η2:η2-C(NHR)CPh}(μ-PCy2)(CNR)2]BF4 (Mo-Mo = 2.6525(5) Å when R = tBu), as a result of H-transfer from hydroxycarbyne to isocyanide ligands and subsequent C-C coupling between aminocarbyne and benzylidyne ligands.
    No preview · Article · May 2015 · Organometallics
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    ABSTRACT: The Na+ salt of the title anion reacted with MeI to give a mixture of isomeric methoxycarbyne [W2Cp2(μ-COMe)(μ-PCy2)(μ-CO)] (major) and methyl-bridged [W2Cp2(μ-CH3)(μ-PCy2)(CO)2] (minor) derivatives, following from competitive methylation at the O atoms or at the ditungsten center, respectively. In contrast, its reaction with ClCH2Ph gave exclusively the benzyl-bridged complex [W2Cp2(μ-CH2Ph)(μ-PCy2)(CO)2], which in solution displays a medium-strength agostic W-H-C interaction, as suggested by the reduced C-H coupling of 90 Hz for the atoms involved. This complex could be dehydrogenated photochemically to give the 30-electron benzylidyne derivative [W2Cp2(μ-CPh)(μ-PCy2)(μ-CO)] in a selective way. The title anion reacted rapidly with several chlorophosphines ClPR2 (R = tBu, Et, Cy) to give also two types of isomers: the phosphinoxycarbyne complexes [W2Cp2(μ-COPR2)(μ-PCy2)(μ-CO)] and the mixed-phosphide derivatives [W2Cp2(μ-PCy2)(μ-PR2)(CO)2], with the former being obtained selectively when R was the bulky tBu group, whereas the latter was the major product for the smaller Et group. The phosphinoxycarbyne complexes were quite unstable species that could not be isolated as pure materials, but when R = Et, Cy, they underwent thermal rearrangement to give the corresponding mixed-phosphide isomers, among other processes. In contrast, the reaction with ClP(O)(OPh)2 gave a more stable phosphatecarbyne complex, [W2Cp2{μ-COP(O)(OPh)2}(μ-PCy2)(μ-CO)], which could be isolated and fully characterized (W-W = 2.5034(4) Å). The title anion also reacted with P4 via its ditungsten center to give the Na+ salt of the diphosphorus-bridged anionic complex [W2Cp2(μ-κ2:κ2-P2)(μ-PCy2)(CO)2]−, following from a symmetrical cleavage of the P4 molecule. The latter anion reacted rapidly with MeI to give the new methyldiphosphenyl-bridged complex [W2Cp2(μ-κ2:κ2-P2Me)(μ-PCy2)(CO)2], which could be isolated in good yield.
    Full-text · Article · Feb 2015 · Organometallics
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    ABSTRACT: Reaction of the title complex with excess [Fe2(CO)9] at room temperature gave the tetranuclear derivative [Fe2Mo2Cp2(μ4-P)(μ-PCy2)(μ3-PMe)(CO)9], following from formal insertion of an Fe(CO)3 fragment in the P-P bond of the diphosphenyl ligand with formation of a new heterometallic bond (Mo-Fe = 2.935 (1) Å), and coordination of an Fe(CO)4 fragment through the lone electron pair of the resulting phosphide ligand (P-Fe = 2.359(2) Å). Reactions of the title complex with excess of the tetrahydrofuran (THF) adducts [MLn(THF)] (MLn = MnCp'(CO)2, W(CO)5) led instead to tetranuclear diphosphenyl-bridged complexes [M2Mo2Cp2(μ-PCy2)(μ-κ(2):κ(1):κ(1):κ(1)-P2Me)(CO)2L2n] displaying a Mo-Mo double bond (Mo-Mo = 2.760(2) Å when M = W), along with the phosphide- and phosphinidene-bridged complex [Mo2W2Cp2(μ3-P)(μ-PCy2)(μ3-PMe)(CO)10], with the latter displaying a Mo-Mo triple bond (Mo-Mo = 2.5542(4) Å) and a trigonal planar phosphide ligand. Reaction of the title complex with excess [Mo(CO)4(THF)2] also resulted in facile P-P bond cleavage of the diphosphenyl ligand to give [Mo4Cp2(μ4-P)(μ-PCy2)(μ3-PMe)(CO)9], a cluster built on a Mo3 triangular core bridged by phosphinidene and phosphide ligands, with the latter further coordinated to an exocyclic Mo(CO)5 fragment. The related Mo2W2 complex [Mo2W2Cp2(μ3-P)(μ-PCy2)(μ3-PMe)(CO)9] could be rationally synthesized upon reaction of the trinuclear cluster [Mo2WCp2(μ3-P)(μ-PCy2)(μ3-PMe)(CO)6] with the adduct [W(CO)5(THF)]. The title complex reacted photochemically with [M2(CO)10] (M = Mn, Re) to give the 66-electron tetranuclear derivatives [M2Mo2Cp2(μ4-P)(μ-PCy2)(μ3-PMe)(CO)9], after formation of a new Mo-M bond (Mo-Mn = 2.9988(7) Å, Mo-Re = 3.1003(4) Å) and cleavage of the diphosphenyl P-P bond. In contrast, its room-temperature reaction with [Co2(CO)8] gave the 64-electron square-planar cluster [Co2Mo2Cp2(μ4-P)(μ-PCy2)(μ4-PMe)(μ-CO)(CO)6] resulting from formation of two new Mo-Co bonds (Mo-Co = 2.8812(7) and 2.9067(7) Å) and facile P-P bond cleavage in the diphosphenyl ligand.
    Full-text · Article · Feb 2015 · Inorganic Chemistry
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    ABSTRACT: The Mo–Mo triple bond of the title complex dominates its Lewis-acid reactivity.•Reactivity of the Mo–P multiple bonds at the title complex is sterically blocked.•Mo–Mo and Mo–P multiple bonds are both involved in P–H bond activation.
    No preview · Article · Jan 2015 · Inorganica Chimica Acta
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    ABSTRACT: Reactions of the title diphosphenyl complex with [Fe2(CO)9] and [W(CO)4(THF)2] gave the trinuclear species [Mo2FeCp2(μ3-P)(μ-PCy2)(μ3-PMe)(CO)5] and [Mo2WCp2(μ3-P)(μ-PCy2)(μ3-PMe)(CO)6] following from formal insertion of the 14-electron fragments Fe(CO)3 and W(CO)4, respectively, in the P-P bond of the diphosphenyl ligand and formation of a new heterometallic bond [Mo-Fe = 2.9294(6) Å and Mo-W = 3.146(1) Å]. Reactions of the diphosphenyl complex with the tetrahydrofuran adducts [MLn(THF)] (MLn = MnCp'(CO)2, W(CO)5) led instead to trinuclear diphosphenyl complexes [Mo2MCp2(μ-PCy2)(μ3-κ(2):κ(2):κ(1)-P2Me)(CO)2Ln] following from coordination in each case of the corresponding 16-electron fragment MLn to the lone-pair-bearing P atom of the P2Me ligand. However, these diphosphenyl complexes were unstable and decomposed at room temperature or under mild heating by the release of methylphosphinidene (PMe), to give the corresponding derivatives [Mo2MCp2(μ3-P)(μ-PCy2)(CO)2Ln] displaying trigonal-planar phosphide ligands, giving rise to strongly deshielded (31)P NMR resonances (δP ca. 1100 ppm), while being involved in strong π bonding with the unsaturated Mo2 center of these molecules [Mo-Mo = 2.749(1) Å and Mo-P = ca. 2.30 Å when M = W]. An isolobal analogy could be established between the P→MLn fragments in these products and a carbyne ligand (CR), supported by density functional theory calculations on the tungsten compound, which also enabled an easy interpretation and prediction of their chemical behavior. Thus, the manganese complex could be reversibly carbonylated (pCO = ca. 3 atm, 293 K) to give the corresponding electron-precise pentacarbonyl [MnMo2Cp2Cp'(μ3-P)(μ-PCy2)(CO)5] [Mo-Mo = 3.1318(7) Å], a process also involving a trans-to-cis rearrangement of the Mo2Cp2 subunit. On the other hand, decarbonylation of the tungsten complex was accomplished in a refluxing toluene solution to give the hexacarbonyl [Mo2WCp2(μ3-P)(μ-PCy2)(μ-CO)(CO)5], a derivative containing an unsaturated 30-electron dimolybdenum center with an intermetallic triple bond.
    No preview · Article · Oct 2014 · Inorganic Chemistry
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    ABSTRACT: The title anions were prepared as (DBU-H)+ salts upon reaction of the oxophosphinidene complex (H-DBU)[MoCp(CO)2{P(O)R*}] with either dimethyldioxirane or elemental sulphur (R* = 2,4,6-C6H2tBu3; Cp = η5-C5H5, DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene). The dioxophosphorane complex failed to react with MeI at room temperature, but reacted readily with (Me3O)BF4 to give the phosphonite complex [MoCp{O,P-OP(OMe)R*}(CO)2]. In contrast, the thiooxophosphorane complex reacted with MeI to give the thiolophosphinide derivative [MoCp{S,P-(MeS)P(O)R*}(CO)2], whereas its reaction with (Me3O)BF4 gave a mixture of the latter complex and the phosphonothiolate isomer [MoCp{S,P-SP(OMe)R*}(CO)2] in similar amounts. Other electrophiles were added selectively to the terminal O atom of the R*POS ligand. Thus the thiooxophosphorane complex reacted with ClC(O)C2H3, [NH4]PF6, ClSiMe3, ClSnMe3 and [ZrCp2Cl2] to give the corresponding derivatives [MoCp{S,P-SP(OX)R*}(CO)2] (X = C(O)C2H3, H, SiMe3, SnMe3, ZrCp2Cl). The structure of two of these products (X = C(O)C2H3, SiMe3) was determined by single-crystal X-ray diffraction studies. Density functional theory (DFT) calculations of the title anions and some of their derivatives indicated that attachment of an external electrophile to the terminal O atom of the thiooxophosphorane ligand is favoured under the conditions of charge control, while the sulphur atom is the favoured site under the conditions of orbital control, although it leads to less stable products.
    No preview · Article · Sep 2014 · Dalton Transactions
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    ABSTRACT: Protonation of the title anion with [NH4]PF6 gave [W2Cp2(H)(μ-PCy2)(CO)2] (), which in solution exists as an equilibrium mixture of two isomers having either bridging (major) or terminal (minor) hydrides. Both molecules retain short intermetallic distances (ca. 2.54 Å), with the H-bridged isomer being almost 15 kJ mol(-1) more stable than the terminal one, according to density functional theory calculations. Further protonation with acids having weakly coordinating anions (BF4(-) or BAr'4(-); Ar' = 3,5-C6H3(CF3)2) yielded isomeric cations also displaying bridging and terminal hydride ligands ([W2Cp2(μ-H)(H)(μ-PCy2)(CO)2](+) and [W2Cp2(H)2(μ-PCy2)(CO)2](+)), with the latter being only slightly more energetic (by ca. 4 kJ mol(-1)). In contrast, protonation of with carboxylic acids yielded carboxylate-bridged derivatives [W2Cp2(μ-PCy2)(μ-O:O'-O2CR)(CO)2] [R = Ph, CF3] following from dihydrogen elimination. The title anion also reacted readily with metal-based electrophiles such as ClSnPh3 and [AuCl(PR3)] (R = (i)Pr, p-tol) to give the corresponding heterometallic clusters [W2Cp2(μ-PCy2)(μ-SnPh3)(CO)2] and [AuW2Cp2(μ-PCy2)(CO)2(PR3)], these having the added electrophile placed at the bridging position and formally retaining triple W-W bonds. The gold complexes, however, were rather unstable species decomposing spontaneously to give the tetranuclear clusters [Au2W2Cp2(μ-PCy2)(CO)2(PR3)2]X (W-W = 2.5803(6) Å and Au-Au = 2.8050(6) Å when R = (i)Pr and X = PF6), which could be prepared more conveniently by adding two equivalents of [AuCl(PR3)] to the anion, as expected. In contrast, reaction of the title anion with ClPbPh3 led to the formation of the phenyl-bridged complex [W2Cp2(μ-PCy2)(μ-Ph)(CO)2], following from the formal loss of PbPh2.
    Full-text · Article · Sep 2014 · Dalton Transactions
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    ABSTRACT: The phosphinidene-bridged complexes [Mo2Cp2(μ-κ(1):κ(1),η(6)-PR*)(CO)2] (1), [Mo2Cp2(μ-κ(1):κ(1),η(4)-PR*)(CO)3] (2), [Mo2Cp(μ-κ(1):κ(1),η(5)-PC5H4)(η(6)-HR*)(CO)2] (3), and [Mo2Cp2(μ-κ(1):κ(1)-PH)(η(6)-HR*)(CO)2] (4) were examined as precursors of heterometallic gold(I) and related derivatives (Cp = η(5)-C5H5, R* = 2,4,6-C6H2(t)Bu3). These complexes reacted with [AuCl(THT)] to give the corresponding derivatives [AuMo2ClCp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2], [AuMo2ClCp2(μ-κ(1):κ(1):κ(1),η(4)-PR*)(CO)3] (Au-Mo = 2.8493(6) Å), [AuMo2ClCp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)], and [AuMo2ClCp2(μ3-PH)(CO)2(η(6)-HR*)] formally resulting from the addition of an acceptor AuCl moiety to the short Mo-P bond of the parent substrates almost perpendicular to the corresponding Mo2P plane. The chloride ligand was easily displaced upon reaction of the PC5H4-bridged gold complex with K[MoCp(CO)3] to give the tetranuclear derivative [AuMo3Cp2(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)5(η(6)-HR*)] (Au-Mo = 2.711(2) and 2.807(2) Å). Compound 1 also reacted with HgI2 to give a hexanuclear complex [HgMo2Cp2(μ-I)I(μ-κ(1):κ(1),η(6)-PR*)(CO)2]2 containing dative Mo→Hg bonds (2.820(1) and 2.827(1) Å), whereas complex 3 gave the μ3-PR bridged complex [HgMo2CpI2(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)]. Complexes 1 to 4 also reacted easily with [AuL(THT)]PF6 (L = THT, P(p-tol)3, PMe3, P(i)Pr3) to give the corresponding cationic trinuclear derivatives [AuMo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2L](PF6) (Au-Mo = 2.8080(3) Å for L = P(p-tol)3), [AuMo2Cp2(μ-κ(1):κ(1):κ(1),η(4)-PR*)(CO)3L](PF6), and [AuMo2Cp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*){P(p-tol)3}](PF6). The blue, analogous PH-bridged complexes were more conveniently isolated as tetra-arylborate salts [AuMo2Cp2(μ3-PH)(CO)2(η(6)-HR*)L](BAr'4) (Au-Mo = 2.8038(6) Å for L = P(i)Pr3; Ar'= 3,5-C6H3(CF3)2]. Compounds 1, 3, and 4 reacted readily with the cation [Au(THT)2](+) (as PF6(-) or BAr'4(-) salts) in a 2:1 ratio to give respectively the corresponding pentanuclear derivatives [Au{Mo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2}2](PF6), [Au{Mo2Cp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)}2](PF6) (Au-Mo = 2.7975(7) and 2.8006(7) Å), and [Au{Mo2Cp2(μ3-PH)(CO)2(η(6)-HR*)}2](BAr'4) (Au-Mo = 2.8233(8) and 2.8691(7) Å). Related silver complexes were obtained from the reaction of 3 and 4 with [AgCl(PPh3)]4 after spontaneous symmetrization, while reaction of 1 with [Cu(NCMe)4]PF6 in a 2:1 ratio yielded the analogous copper complex [Cu{Mo2Cp2(μ-κ(1):κ(1):κ(1),η(6)-PR*)(CO)2}2](PF6). All the above cationic gold complexes having (μ-κ(1):κ(1):κ(1),η(6)-PR*) ligands (but not the copper complex) rearranged into [Au{Mo2Cp(μ-κ(1):κ(1):κ(1),η(5)-PC5H4)(CO)2(η(6)-HR*)}2](PF6) in refluxing 1,2-dichloroethane solution.
    No preview · Article · Sep 2014 · Inorganic Chemistry
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    ABSTRACT: The dicarbonyl complex trans-[W2Cp2(μ-PPh2)2(CO)2] (Cp = η(5)-C5H5) reacted rapidly with NO (5% in N2) at 273 K to give selectively cis-[W2Cp2(μ-PPh2)2(NO)2]. In contrast, the analogous reactions of monocarbonyl [W2Cp2(μ-PPh2)2(μ-CO)] yielded either trans-[W2Cp2(μ-PPh2)2(NO)2] or the nitrito complex [W2Cp2(μ-PPh2)2(ONO)(CO)(NO)] (W-W = 2.9797(4) Å), depending on experimental conditions, with the latter presumably arising from reaction with trace amounts of oxygen in the medium. The stereoselectivity of the above reactions can be rationalized by assuming the participation of 33-electron [W2Cp2(μ-PPh2)2(CO)(NO)] intermediates which rapidly add a second molecule of NO via η(2)-C5H5 intermediates to eventually yield the corresponding dinitrosyls with inversion of the stereochemistry at the dimetal center, as supported by density functional theory (DFT) calculations. The nitrito complex was thermally unstable and evolved through oxygen transfer either to the carbonyl ligand, to yield the above dinitrosyls with release of CO2, or to the phosphide ligand, to give the phosphinito derivative cis-[W2Cp2(μ-OPPh2)(μ-PPh2)(NO)2], depending on experimental conditions. According to DFT calculations, the first process would involve transient dissociation/recombination of the nitrite ligand followed by coupling to carbonyl to give an intermediate with a chelate W{C,N-C(O)ON(O)} ring. Indeed, the nitrite ligand could be easily removed upon reaction of the nitrito complex with Na(BAr'4), but immediate decomposition also took place to render the electron-precise dicarbonyl [W2Cp2(μ-PPh2)2(CO)2(NO)]BAr'4 (W-W = 2.9663(3) Å) as the unique product (Ar' = 3,5-C6H3(CF3)2). Attempts to decarbonylate the latter complex photochemically yielded instead the oxo derivatives cis- and trans-[W2Cp2(μ-PPh2)2(O)(NO)]BAr'4 as the only isolable products (W-W = 2.980(2) and 3.0077(3) Å, respectively).
    No preview · Article · Apr 2014 · Inorganic Chemistry
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    ABSTRACT: The methyl-bridged complex [Mo2Cp2(μ-Me)(μ-PCy2)(CO)2] (Cp = η(5)-C5H5) reacted with stoichiometric amounts of CN(t)Bu at 243 K to give the C,O:C,O-bridged acyl complex [Mo2Cp2{μ-C,O:C,O-C(O)Me}(μ-PCy2)(CN(t)Bu)(CO)], which at room temperature slowly rearranges into its iminoacyl-bridged isomer [Mo2Cp2(μ-C,N:C,N-MeCN(t)Bu)(μ-PCy2)(CO)2]. In contrast, the C:O-bridged acyl complex [Mo2Cp2{μ-C:O-C(O)Me}(μ-PCy2)(CN(t)Bu)(CO)] was the major product obtained when the above reaction was carried out at room temperature. Density Functional Theory (DFT) was used to find the most likely structures of all these isomers, of which the iminoacyl complex was the absolute minimum. In contrast to the above reactions, up to three molecules of the ligand added rapidly to the methyl complex when using the aryl isocyanides CNR (R = o-C6H4Me, p-C6H4OMe), triggering the coupling between the methyl ligand and one of the cyclopentadienyl groups to give the corresponding methylcyclopentadiene derivatives [Mo2Cp(η(4)-C5H5Me)(μ-PCy2)(CNR)3(CO)]. Carbonylation of the latter complex (R = o-C6H4Me) induced the displacement of the η(4)-bound ligand, but also gave small yields of the hydride derivative [Mo2Cp(η(5)-C5H4Me)(μ-H)(μ-PCy2){CN(o-C6H4Me)}(CO)3] (Mo-Mo = 3.2467(5) Å), the latter resulting from a C-H cleavage in the methylcyclopentadiene ligand. The reaction of the title complexes with phosphines HPR (R' = Et, Ph) gave two major products: the corresponding aldehyde complexes [Mo2Cp2(μ-PCy2)(μ-PR){η(2)-C(O)HR}(CO)] (Mo-Mo = 2.8288(5) Å when R = CH2Ph and R' = Et) and the dicarbonyl complexes [Mo2Cp2(μ-PCy2)(μ-PR)(CO)2], these following from alternative reductive elimination processes, from hydrogen and either acyl or alkyl ligands, respectively.
    No preview · Article · Apr 2014 · Dalton Transactions
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    ABSTRACT: Reactions of the chalcogenophosphinidene-bridged complexes syn-[Mo2Cp2(μ-κ2P,Z:κ1P,η4-ZPMes*)(CO)2L] (L = CO, CNtBu; Z = O, S, Se), anti-[Mo2Cp2(μ-κ2P,S:κ1P,η4-SPMes*)(CO)2L] (L = CO, CNtBu) and [Mo2Cp2{μ-κ2P,Z:κ1P-ZPH}(η6-HMes*)(CO)2] (Z = S, Se, Te) towards sources of H+, Me+, and AuP(pTol)3+ cations were investigated (Mes* = 2,4,6-C6H2tBu3; Cp = η5-C5H5). The latter two electrophiles invariably added to the chalcogen atom to give corresponding derivatives [Mo2Cp2{μ-κ2P,Z:κ1P,η4-Mes*PZ(CH3)}(CO)3]BX4 [X = F, Z = O, S, Se; P–S 2.144(1) Å when Z = S and X = Ar′ = 3,5-C6H3(CF3)2], [Mo2Cp2{μ-κ2P,Z:κ1P,η4-Mes*PZ(CH3)}(CNtBu)(CO)2]BF4 (Z = S, Se), and [AuMo2Cp2(μ3-κ1S:κ2P,S:κ1P,η4-SPMes*){P(pTol)3}(CO)3]PF6 [P–S 2.113(2), S–Au 2.320(2) Å]. Even when syn and anti isomers of the neutral precursor were used, the corresponding products were invariably characterized by their syn conformation (Z atom close to L ligand). Besides this, methylated derivatives of the chalcogenophosphinidene complexes bearing the formula [Mo2Cp2{μ-κ2P,Z:κ1P-HPZ(Me)}(η6-HMes*)(CO)2](CF3SO3) (Z = S, Se, Te), were found in solution to exist as an equilibrium of corresponding cis and trans isomers differing, in each case, in the relative positioning of the Cp rings with respect to the MoPZ plane. In contrast to the above results, the protonation of all these compounds was quite sensitive to the particular chalcogenophosphinidene ligand and conformation of the complex. Protonation of the HPZ-bridged complexes led to complex mixtures of products that could not be isolated or properly characterized. In contrast, the aryl-bearing substrates reacted selectively to give corresponding complexes [Mo2Cp2{μ-κ2P,Z:κ1P,η5-ZP(C6H3tBu3)}(CO)3]BX4 (Z = S, X = F; P–S 2.032(2) Å when X = Ar′; Z = Se, X = F) and [Mo2Cp2{μ-κ2P,Z:κ1P,η5-ZP(C6H3tBu3)}(CNtBu)(CO)2]BAr′4 (Z = S, Se). The reaction of anti-[Mo2Cp2(μ-κ2P,S:κ1P,η4-SPMes*)(CO)3] with HBF4·OEt2 at 213 K initially gave unstable intermediate anti-[Mo2Cp2{μ-κ2P,S:κ1P,η4-Mes*PS(H)}(CO)3]BF4, which then rapidly converted at room temperature to the conventional isomer with the S atom close to the metallocene-bound carbonyl ligand (syn isomer). This transformation is in agreement with Density Functional Theory calculations for neutral thiophosphinidene complexes; electrophilic attack at the sulfur atom, which is both an orbital- and charge-favoured event, affords products that are more stable than those resulting from protonation at the metal sites. All these protonation reactions eventually result in an endo addition of H+ to the C6 atom of the Mes* ring with concomitant η4→η5 haptotropic shift of the resulting HMes* group. This conversion involves an easy H migration from S to the C6 atom, computed to take place with a low activation barrier of about 70 kJ/mol.
    No preview · Article · Apr 2014 · European Journal of Inorganic Chemistry
  • M. Angeles Alvarez · M. Esther García · Sonia Menéndez · Miguel A Ruiz
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    ABSTRACT: The benzylidyne complex [Mo2Cp2(m-CPh)(m-PCy2)(m-CO)] (1) reacted with either 2-aminothiophenol or 2-hydroxythiophenol in the presence of 1 equiv of [FeCp2]BF4 to give selectively the corresponding thiolate-bridged derivatives [Mo2Cp2(m-CPh)(m-PCy2)(m-S:S,N-SC6H4NH2)(CO)]BF4 and [Mo2Cp2(m-CPh)(m-PCy2)(m-S:S,O-SC6H4OH)(CO)]BF4 (Cp = h5-C5H5). The latter complex was readily deprotonated by 1,8-diazabicycloundec-7-ene (DBU) to give the phenolate derivative [Mo2Cp2(m-CPh)(m-PCy2)(m-S:S,O-SC6H4O)(CO)] (Mo-Mo = 2.7837(8) Å), with retention of the overall stereochemistry. In contrast, the redox-induced reaction of 1 with 2-aminophenol gave the chelate derivative [Mo2Cp2(m-CPh)(m-PCy2)(O,N-OC6H4NH2)(CO)]BF4, whereas the reaction with catechol yielded the O-bound cathecolate derivative [Mo2Cp2(m-CPh)(m-PCy2)(O-OC6H4OH)(CO)]BF4, an unstable complex that was deprotonated with DBU to give the more stable catechodiolate derivative [Mo2Cp2(m-CPh)(m-PCy2)(O,O´-O2C6H4)(CO)], displaying a chelate ligand (Mo-Mo = 2.7850(5) Å). The redox-induced reaction of 1 with benzoic acid still took a different pathway, to eventually yield the benzoate-bridged derivative [Mo2Cp2(m-CPh)(m-O:O´-O2CPh)(m-PCy2)]BF4 (Mo-Mo = 2.577(1) Å). The formation and structures of all the above products could be satisfactorily explained by assuming different elemental steps starting from the radical [Mo2Cp2(m-CPh)(m-PCy2)(m-CO)]+ that follows from the 1-electron oxidation of the neutral benzylidyne complex 1.
    No preview · Article · Mar 2014 · Organometallics
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    ABSTRACT: A novel dimerization of maleic anhydride involving olefinic to carbonyl C–C coupling and an [1,7]-H shift is promoted by a strongly nucleophilic pyramidal phosphinidene complex. The resulting carbene is stabilized by coordination of the P atom of the phosphinidene ligand and undergoes keto/enol tautomerization when going from solution to the solid state. This is accompanied by a strong pyramidalization of the ylidic carbon atom, facilitated by the presence of π···π stacking interactions in the crystal lattice.
    No preview · Article · Oct 2013 · Organometallics