Chemistry of heavy carbene analogues R2M (M  Si, Ge, Sn)

Klein, Beatrix; Neumann, Wilhelm P.; Weisbeck, Markus; Wienken, S.

doi:10.1016/0022-328x(93)80047-f

Cited by 19 publications

(13 citation statements)

References 17 publications

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“…7, and selected bond lengths and angles are collected in Table 5. The Ge-O bond lengths of the bound aryloxide ligands in 6 are 1.720(4) and 1.733(4) Å, which are 37 The upfield shift of the methyl resonance of 7 is likely a result of the diamagnetic anisotropy of the ortho-phenyl rings of the tetraphenylphenoxide ligands, which provides increased shielding for the methyl protons.…”

Section: Reaction Chemistry Of [Ge(oar) 2 ] Nmentioning

confidence: 97%

Synthesis, structures and reactivity of novel germanium(ii) aryloxide and arylsulfide complexes

et al. 2003

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Section: Reaction Chemistry Of [Ge(oar) 2 ] Nmentioning

confidence: 97%

Synthesis, structures and reactivity of novel germanium(ii) aryloxide and arylsulfide complexes

et al. 2003

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“…The second objective was to examine the effects on the O−H insertion reaction with HOAc. This reaction is closely related to that with alcohols, which was first discovered by Lappert and co-workers and has since been shown to proceed via initial Lewis acid−base complexation followed by rate-determining H-migration, ,, the second step most likely proceeding catalytically. , Both steps in the sequence are reversible, as has been known since the work of Satgé and co-workers on the chemistry of hydridoalkoxygermanes . The primary question to be answered in the case of the analogous reaction with carboxylic acids, which in contrast to the reaction with alcohols proceeds irreversibly, is whether the mechanism is similar to that of the reaction with alcohols (with the carboxylic acid playing the role of the base in the initial step) or involves protonation of the germylene in the initial (or perhaps only kinetically significant) step.…”

Section: Introductionmentioning

confidence: 94%

Substituent Effects on the Reactions of Diarylgermylenes and Tetraaryldigermenes with Acetic Acid and Other Lewis Bases in Hydrocarbon Solution

Huck

Leigh

2007

Organometallics

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A series of three 1,1-diaryl-3,4-dimethylgermacyclopent-3-ene derivatives bearing polar substituents in the para-positions of the 1,1-diphenyl rings have been synthesized, and their photochemistry has been studied by steady state and laser flash photolysis methods. Photolysis in hydrocarbon solvents affords the corresponding diarylgermylenes in chemical and quantum yields similar to those of the parent (1,1-diphenyl) compound, as shown by the results of trapping experiments with methanol (MeOH) and acetic acid (HOAc). The germylenes exhibit UV/vis absorption spectra (λmax = 480−500 nm) and kinetic behavior (τ ≈ 2 μs) similar to that of the parent, diphenylgermylene (GePh2), in hexane solution. Their decay results in the formation of new transient products assigned to the corresponding tetraaryldigermenes (Ge2Ar4), whose absorption spectra (λmax = 440 nm) and lifetimes are also similar to those exhibited by the parent, Ge2Ph4. Both the germylenes and the corresponding digermenes are quenched rapidly by added HOAc and Et2NH, with rate constants that increase with increasing electron-withdrawing power of the aryl substituents, consistent with reaction mechanisms that involve initial nucleophilic attack at germanium in all cases. The Lewis acid−base complexation of the three germylenes with THF and ethyl acetate (EtOAc) has also been studied and supports a two-step mechanism for the reaction with HOAc that involves initial, rate-determining nucleophilic attack at germanium followed by rapid proton transfer. A similar mechanism is proposed for reaction of this substrate with Ge2Ph4 on the basis of the measured Hammett ρ-value. Tetramesityldigermene reacts with HOAc in toluene or THF solution to afford the 1,2-addition product, 1-acetoxy-1,1,2,2-tetramesityldigermane, while no reaction could be detected with Et2NH.

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“…The reactions studied include O-H insertion with AcOH, Lewis acid-base complexation with primary and tertiary amines, M-H insertions with trialkylhydridosilanes and -stannanes, reaction with terminal alkenes, alkynes, and conjugated dienes, chlorine atom abstraction from CCl 4 , reaction with oxygen, and dimerization, as summarized in Scheme 4. While product studies specific to GeMePh have not been carried out in most instances, the course of these reactions are well established for GeMe 2 and other reactive germylenes (1,10,11,24,25) and all of them have direct analogies in silylene chemistry (26).…”

Section: Mementioning

confidence: 99%

Direct detection of methylphenylgermylene and 1,2-dimethyl-1,2-diphenyldigermene — Kinetic studies of their reactivities in solution

Leigh¹,

Dumbrava²,

Lollmahomed³

2006

Can. J. Chem.

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Photolysis of 1,3,4-trimethyl-1-phenylgermacyclopent-3-ene (5) in hydrocarbon solvents containing isoprene, methanol, or acetic acid affords 2,3-dimethyl-1,3-butadiene (DMB) and the expected trapping products of methyl phenylgermylene (GeMePh) in chemical yields exceeding 90%. The germylene has been detected in hexane solution by laser flash photolysis as a short-lived species (τ ~ 2 µs) exhibiting a UV-vis absorption spectrum centered at λmax = 490 nm. It decays with second-order kinetics and a rate constant close to the diffusion-controlled limit, with the concomitant growth of a second longer-lived transient (λmax = 420 nm) that is assigned to a mixture of (E)- and (Z)-1,2-dimethyl-1,2-diphenyldigermene (4). Absolute rate constants have been determined for the reactions of the germylene with primary and tertiary amines (n-BuNH2 and Et3N, respectively), acetic acid (AcOH), a terminal alkyne and alkene, isoprene, DMB, CCl4, and the group 14 hydrides Et3SiH and Bu3SnH. GeMePh is slightly more reactive than GePh2 towards all the reagents studied in this work; both are significantly less reactive than GeMe2 toward the same substrates. Absolute rate constants for the reactions of 4 have also been measured or assigned upper limits in every case and are compared to previously reported values for tetraphenyl- and tetramethyl-digermene with the same reagents.Key words: germylene, digermene, kinetics, laser flash photolysis, germirane, germirene, vinylgermirane, complex, UV–vis spectrum, insertion, addition.

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Chemistry of heavy carbene analogues R2M (M  Si, Ge, Sn)

Cited by 19 publications

References 17 publications

Synthesis, structures and reactivity of novel germanium(ii) aryloxide and arylsulfide complexes

Synthesis, structures and reactivity of novel germanium(ii) aryloxide and arylsulfide complexes

Substituent Effects on the Reactions of Diarylgermylenes and Tetraaryldigermenes with Acetic Acid and Other Lewis Bases in Hydrocarbon Solution

Direct detection of methylphenylgermylene and 1,2-dimethyl-1,2-diphenyldigermene — Kinetic studies of their reactivities in solution

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