859527-83-6

Upstream product

• 32109-09-4 [MoH₄(1,2-bis(diphenylphosphino)ethane)2] 
• 1072-14-6 hexylsilane 

Relevant academic research and scientific papers

Reactivity patterns of O2, CO2, carboxylic acids, and triflic acid with molybdenum silyl hydrido complexes bearing polydentate phosphinoalkyl-silyl ligands: Pronounced effects of silyl ligands on reactions

The reactivity patterns of a series of molybdenum silyl hydrido complexes, [MoH3{[Ph2PCH2CH2P(Ph)C 6H4-o]2(R)Si-P,P,P,P,Si}] (2a, R = Ph; 2b, R = C6F5; 2c, R = 4-Me2NC6H4; 2d, R = cyclohexyl; 2e, R = n-C6H13), toward electrophilic materials, including dioxygen, carbon dioxide, carboxylic acids, and triflic acid, have been explored. The influence of substituents directly attached to the Si atom in the quintuply chelating diphosphine-silyl ligands during the course of the reactions has been studied in detail. Complexes 2a-c react readily with dioxygen at ambient temperature, yielding η2-O2 complexes 3a-c, in which the dioxygen ligand ligates at the site opposite to the Si atom. Single-crystal X-ray studies have established that the Mo-O distance of 3a, which contains a phenyl-substituted Si fragment, is significantly longer than that found in common η2-O2 complexes, in which the sizes of the central atoms are nearly equal to that of Mo as a consequence of the strong trans influence of the silyl ligand. In contrast, the replacement of the phenyl group on a Si fragment by an electron-withdrawing perfluoro phenyl group, as in 3b, gives rise to a dramatic decrease in the trans influence. Treatment of 2a-c with 2 equiv of carboxylic acids, such as formic acid, acetic acid, and benzoic acid, readily leads to the formation of carboxylato molybdenum complexes, in which the carboxylate ligand coordinates to the metal in a monodentate mode. The resulting formato complex 4a1 can also be derived from the insertion of CO 2 into the Mo-H bond of 2a. In addition, complexes 2a,c,e mediate the catalytic carbon dioxide hydrogenation. The activity of the catalysts depends dramatically on the electronic effects of the substituents attached to the Si atom; electron-donating substituents lead to an increase in the catalytic activity. Reactions of complexes 2a,d with triflic acid yield highly labile triflato complexes, which can be further treated with aqueous NaOH to give hydroxo complexes 5a,d, respectively. The molecular structure of 5d has been determined by single-crystal X-ray diffraction. The reactivities of 2a-e are discussed in comparison with those of the parent complex [MoH 4(dppe)2] (1; dppe = Ph2PCH2CH 2PPh2).

Unexpected formation of polydentate phosphinoalkyl-silyl and -germyl ligands from reaction of [MoH4(Ph2PCH2CH 2PPh2)2] with organosilanes and organogermanes: Novel activation of Mo-H, E-H (E = Si, Ge), and C-H bonds in the same system

Reaction of [MoH4(Ph2PCH2CH 2PPh2)2] (1) with PhEH3 (E = Si, Ge) in refluxing toluene yielded the novel complexes [MoH3{[Ph 2PCH2CH2P(Ph)C6H4-o] 2(Ph)E-P,P,P,P,E}] (E = Si (2), Ge (3)) with a quinquidentate ligand comprised of a P-P-E-P-P framework as a result of the oxidative addition involving E-H bond cleavage with concomitant selective activation of the ortho C-H bonds of the two dppe ligands. When secondary Ph2SiH2 was employed in a similar reaction with 1, a trihydrido complex with a tridentate ligand ([Ph2PCH2CH2P-(Ph)C 6H4-o]Ph2Si-P,P,Si) comprised of a P-P-Si framework was isolated. On the other hand, the reaction between Ph 2GeH2 and 1 proceeded with accompanying evolution of 1 mol of benzene to give 3; that is, in addition to the Ge-H and C-H activation, Ge-C(Ph) bond cleavage took place. It is concluded that the reaction path includes the intermediacy of silylene or germylene metal complexes via an α-migration process on the basis of deuterium-labeling studies.