Silyl-Komplexe des Molybdäns und Wolframs. Synthese, Reaktivität und Struktur

Petri, S.; Neumann, Beate; Stammler, Hans‐Georg; Jutzi, Peter

doi:10.1016/s0022-328x(97)00617-7

Cited by 17 publications

(11 citation statements)

References 66 publications

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“…In both cases, the Mo−H bond is longer than in 4 (1.71(9) and 1.74(8) Å, respectively). Mo−H bond distances more similar to the one in 4 are found in the complexes [Cp 2 Mo(H)(SiH 2 (C 5 Me 4 H)], XIX (1.58(6) Å), and [Cp 2 Mo(H)(SnMe 3 )], XX (1.60(5) and 1.51(6) Å in two independent molecules in the unit cell).…”

Section: Resultsmentioning

confidence: 60%

Reactivity and Properties of [−O−Bi^III...OMo−]_nChains

et al. 2006

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A coordination polymer [Cp(O)2Mo-O-Bi(o-tolyl)2]n, II, containing Mo-O-Bi and Mo=O...Bi moieties was investigated with respect to its behavior in contact with OH- and Cp2MoH2 and as potential single source precursor in the polyol method. It turned out that hydroxide as a base breaks up the polymer to yield CpMoO3- and (o-tolyl)2BiOH. The latter polymerizes to give the coordination polymer [(o-tolyl)2BiOH]n, 1. Alternatively, 1 can be prepared by reacting [(o-tolyl)2Bi(hmpa)2]SO3CF3 with NBu4OH/H2O in thf/water. If, however, NBu4OH/MeOH is used in dichloromethane as the solvent, the (o-tolyl)2BiOH formed intermediately undergoes methanolysis, and finally, [(o-tolyl)2BiOMe]n, 3, is isolated. Although 1 and 3 are very similar compounds, their crystal structures differ significantly: while the structure of 1 is dominated by secondary bonding leading to seesaw-type coordination geometries around the Bi centers, the Bi atoms in 3 are coordinated in a distorted tetrahedral fashion, and secondary bonding plays only a minor role. If 1 is dissolved in a nonpolar, nonprotic solvent, condensation reactions occur immediately leading to [(o-tolyl)2BiOBi(o-tolyl)2], 2, which can be obtained on a preparative scale this way. Compound 3 which can be prepared in good yields may prove to be a useful starting material in bismuth chemistry. Here, it was shown to react with molybdocene dihydrides to provide stable Bi-substituted molybdocene monohydrides [(R)Cp2Mo(H)(Bi(o-tolyl)2)] (R = Me 4, R = H 5); compounds of that type were identified in solution before but had so far eluded isolation. Compound 4, whose crystal structure is discussed, also forms when II is treated with methylated molybdocene dihydride. This obviously leads to the formation of Mo-Bi bonds (--> 4), as well as Mo-OH units, which undergo condensation reactions leading to Mo-O-Mo moieties (i.e., [Cp2Mo2O5] is formed as a byproduct). The use of II as precursor in the polyol method successfully led to bismuthmolybdate nanoparticles (accompanied by crystallites); however, no single phase is obtained, but biphasic materials consisting of Bi(2)Mo2O9 and Bi2MoO6, whose ratio can be determined by the choice of the hydrolyzing reagent, are formed instead. One of these materials proved to be capable of sensing EtOH selectively at elevated temperatures.

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Section: Resultsmentioning

confidence: 60%

Reactivity and Properties of [−O−Bi^III...OMo−]_nChains

et al. 2006

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“…Matrix isolation experiments revealed tungstenocene as the primary photoproduct and showed via IR, UV–vis, laser-induced fluorescence, and magnetic circular dichroism that it has a parallel sandwich structure with a 3 E 2g ground state. These early experiments are summarized in reviews. , Since then, the matrix photochemistry has been investigated in more detail. − Additional reports have added the photochemical reactions of Cp 2 W(H) 2 in solution with HSiCl 3 , HSiMe 2 Cl, and HSiMe 3 to make the corresponding Cp 2 WH(SiR 3 ) complexes. , Co-irradiation of Cp 2 W(H) 2 and metal–metal-bonded carbonyl complexes such as [CpNi(CO)] 2 or [CpRu(CO) 2 ] 2 have been used to generate heterodinuclear complexes. In these reactions with two metal complexes, there is no control of which complex undergoes photochemical reactions, and it is likely that both contribute .…”

Section: Photochemical Processesmentioning

confidence: 99%

“…The photoactivity of Cp 2 Mo(H) 2 led to H 2 elimination in the primary photochemical step (quantum yield at 366 nm = 0.1 ± 0.02) to yield the transient unsaturated species [Cp 2 Mo] that was trapped in the presence of CO, C 2 H 2 , and PR 3 to form the respective adducts. , The photochemical reaction in C 6 H 6 resulted in dimerization, while irradiation in the presence of thiophene formed the C–H activated product Cp 2 MoH(2-thienyl), selectively . Reactions in the presence of hydridosilanes produced the silyl hydride complexes Cp 2 MoH(SiR 3 ) in very good yields through a reductive elimination/oxidative addition process; similar behavior was observed for the Cp* analogue. , Thus, molybdenocene inserts into Si–H bonds, but the only C–H bonds that prove reactive are those of thiophene and its own precursor Cp 2 Mo(H) 2 . The reactions in the presence of activated alkenes formed a series of electron donor–acceptor complexes with charge-transfer bands in the visible region.…”

Section: Metal Hydride Photochemistry By Transition Metal Groupmentioning

confidence: 99%

“…Photoreaction with ethyl acetate yielded Cp 2 WH(OCOEt), whereas reaction with carboxylic acids generated Cp 2 W(OCOR) 2 (R= H, Me, Et, CH 2 CMe). , With thiophene, C–S bond cleavage was achieved as a primary photoproduct; prolonged irradiation converted the latter into the C–H insertion product Cp 2 WH(2-thienyl) . A number of mono- and bis(silyl) complexes of W were obtained in good yields by photolysis at 350 nm of Cp 2 W(H) 2 in hydridosilanes; Cp* derivatives were also prepared by the same method. , In the absence of substrates, dimers are formed resulting from activation of C–H bonds of the cyclopentadienyl groups . The reaction of Cp 2 W(H) 2 in the presence of M–M bonded complexes led to the formation of heterometallic clusters, but the presence of CO groups in the reagents made it unclear whether the photochemistry proceeds by H 2 reductive elimination from the tungsten precursor or CO loss from one of the dimers .…”

Section: Metal Hydride Photochemistry By Transition Metal Groupmentioning

confidence: 99%

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Photochemistry of Transition Metal Hydrides

2016

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Photochemical reactivity associated with metal-hydrogen bonds is widespread among metal hydride complexes and has played a critical part in opening up C-H bond activation. It has been exploited to design different types of photocatalytic reactions and to obtain NMR spectra of dilute solutions with a single pulse of an NMR spectrometer. Because photolysis can be performed on fast time scales and at low temperature, metal-hydride photochemistry has enabled determination of the molecular structure and rates of reaction of highly reactive intermediates. We identify five characteristic photoprocesses of metal monohydride complexes associated with the M-H bond, of which the most widespread are M-H homolysis and R-H reductive elimination. For metal dihydride complexes, the dominant photoprocess is reductive elimination of H2. Dihydrogen complexes typically lose H2 photochemically. The majority of photochemical reactions are likely to be dissociative, but hydride complexes may be designed with equilibrated excited states that undergo different photochemical reactions, including proton transfer or hydride transfer. The photochemical mechanisms of a few reactions have been analyzed by computational methods, including quantum dynamics. A section on specialist methods (time-resolved spectroscopy, matrix isolation, NMR, and computational methods) and a survey of transition metal hydride photochemistry organized by transition metal group complete the Review.

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“…Reaction of Cp 2 MH 2 with primary, secondary, or tertiary silanes has provided several examples of formation of derivatives of Cp 2 (H)MSiR 3 including R ) Et (M ) Mo, 3-31) and R ) Cl (M ) W, 3-38). 35 Niobium hydrides have also been used as precursors to silyl-niobium complexes. When Cp 2 NbH 3 was reacted with HSiMe 2 Cl in toluene at 50-60 °C, a mixture of two isomers of Cp 2 (H) 2 NbSiMe 2 Cl (3-12ab) formed, but at 95 °C, the product was the symmetrical isomer of Cp 2 Nb(SiMe 2 Cl) 2 H (3-16).…”

Section: Tm-h Precursorsmentioning

confidence: 99%