132698-69-2Relevant academic research and scientific papers
Synthesis and reactivity of silyl ruthenium complexes: The importance of trans effects in C-H activation, Si-C bond formation, and dehydrogenative coupling of silanes
Dioumaev, Vladimir K.,Procopio, Leo J.,Carroll, Patrick J.,Berry, Donald H.
, p. 8043 - 8058 (2003)
A series of octahedral ruthenium silyl hydride complexes, cis-(PMe3)4Ru(SiR3)H (SiR3 = SiMe3, 1a; SiMe2CH2SiMe3, 1b; SiEt3, 1c; SiMe2H, 1d), has been synthesized by the reaction of hydrosilanes with (PMe3)3Ru(η2-CH2 PMe2)H (5), cis-(PMe3)4RuMe2 (6), or (PMe3)4RuH2 (9). Reaction with 6 proceeds via an intermediate product, cis-(PMe3)4Ru(SiR3)Me(SiR3 = SiMe3, 7a; SiMe2CH2SiMe3, 7b). Alternatively, 1 and 7 have been synthesized via a fast hydrosilane exchange with another cis-(PMe3)4Ru(SiR3)H or cis-(PMe3)4-Ru(SiR3)Me, which occurs at a rate approaching the NMR time scale. Compounds 1a, 1b, 1d, and 7a adopt octahedral geometries in solution and the solid state with mutually cis silyl and hydride (or silyl and methyl) ligands. The longest Ru - P distance within a complex is always trans to Si, reflecting the strong trans influence of silicon. The aptitude of phosphine dissociation in these complexes has been probed in reactions of 1a, 1c, and 7a with PMe3-d9 and CO. The dissociation is regioselective in the position trans to a silyl ligand (trans effect of Si), and the rate approaches the NMR time scale. A slower secondary process introduces PMe3-d9 and CO in the other octahedral positions, most likely via nondissociative isomerization. The trans effect and trans influence in 7a are so strong that an equilibrium concentration of dissociated phosphine is detectable (～5%) in solution of pure 7a. Compounds 1a-c also react with dihydrogen via regioselective dissociation of phosphine from the site trans to Si, but the final product, fac-(PMe3)3Ru(SiR3)H3 (SiR3 = SiMe3, 4a; SiMe2CH2SiMe3, 4b; SiEt3, 4c), features hydrides cis to Si. Alternatively, 4a-c have been synthesized by photolysis of (PMe3)4RuH2 in the presence of a hydrosilane or by exchange of fac-(PMe3)3Ru(SiR3)H3 with another HSiR3. The reverse manifold - HH elimination from 4a and trapping with PMe3 or PMe3-d9 - is also regioselective (1a-d9 is predominantly produced with PMe3-d9 trans to Si), but is very unfavorable. At 70 °C, a slower but irreversible SiH elimination also occurs and furnishes (PMe3)4RuH2. The structure of 4a exhibits a tetrahedral P3Si environment around the metal with the three hydrides adjacent to silicon and capping the P2Si faces. Although strong Si...HRu interactions are not indicated in the structure or by IR, the HSi distances (2.13-2.23(5) A) suggest some degree of nonclassical SiH bonding in the H3SiR3 fragment. Thermolysis of 1a in C6D6 at 45-55 °C leads to an intermolecular CD activation of C6D6. Extensive H/D exchange into the hydride, SiMe3, and PMe3 ligands is observed, followed by much slower formation of cis-(PMe3)4Ru(D)(Ph-d5). In an even slower intramolecular CH activation process, (PMe3)3Ru(η2-CH2 PMe2)H (5) is also produced. The structure of intermediates, mechanisms, and aptitudes for PMe3 dissociation and addition/elimination of H-H, Si-H, C-Si, and C-H bonds in these systems are discussed with a special emphasis on the trans effect and trans influence of silicon and ramifications for SiC coupling catalysis.
Inter- and intramolecular C-H bond forming and cleavage reactivity of two different types of poly(trimethylphosphine)ruthenium intermediates
Hartwig, John F.,Andersen, Richard A.,Bergman, Robert G.
, p. 6492 - 6498 (2007/10/02)
The products and mechanisms of the thermal reactions of several complexes of the structure (PMe3)4Ru(X)(H), where X is an aryl or benzyl group, have been investigated. The mechanism of decomposition depends critically on the structure of the complex and the medium in which the thermolysis is carried out. For example, thermolysis of the benzyl hydride complex (PMe3)4Ru(CH2Ph)(H) (1) leads to reductive elimination of toluene directly from the 18-electron complex and yields the intermediate (PMe3)4Ru which undergoes intramolecular oxidative addition of a phosphine C-H bond. Heating the phenyl hydride complex (PMe3)4Ru(Ph)(H) (5) in cyclohexane also leads to reductive elimination to form (PMe3)4Ru, In contrast, allowing 5 to decompose in arene solvents leads to exchange of the arene ring by an intermolecular C-H activation mechanism involving the intermediate (PMe3)3Ru(Ph)(H) by rapid, reversible phosphine dissociation. Thermolysis of (PMe3)4Ru(H)2 does not result in the formation of H2 and (PMe3)4Ru, but instead it undergoes only H/D exchange with C6D6 solvent via the intermediate (PMe3)3Ru(H)2. Thus, the intermediate (PMe3)4Ru gives rise to products resulting from intramolecular C-H activation, whereas (PMe3)3Ru(Ph)(H) and (PMe3)3Ru(H)2 lead only to products resulting from intermolecular C-H activation.
Structure, synthesis, and chemistry of (PMe3)4Ru(η2-benzyne). Reactions with arenes, alkenes, and heteroatom-containing organic compounds. synthesis and structure of a monomeric hydroxide complex
Hartwig, John F.,Bergman, Robert G.,Andersen, Richard A.
, p. 3404 - 3418 (2007/10/02)
Thermolysis of (PMe3)4Ru(Ph)(Me) or (PMe3)4Ru(Ph)2 leads to the ruthenium benzyne complex (PMe3)4Ru(η2-C6H4) (1) by a mechanism that involves initial reversible dissociation of phosphine. In many ways, its chemistry is analogous to that of early rather than late organo-transition-metal complexes. Thus, compound 1 undergoes apparent σ-bond metathesis reactions with the C-H bonds of benzene or toluene solvent (the reverse of the formation of 1), the N-H bond in aniline, and O-H bonds of p-cresol, 2-propanol, and water. The monomeric hydroxide complex resulting from addition of water has been structurally characterized. Compound 1 also undergoes insertion reactions with a variety of unsaturated organic molecules, including ethylene, di-p-tolylacetylene, benzaldehyde, and benzonitrile. Qualitative mechanistic studies on the O-H addition of p-cresol and the insertion of benzaldehyde and benzonitrile are reported.
