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.

نویسندگان

  • Vladimir K Dioumaev
  • Leo J Procopio
  • Patrick J Carroll
  • Donald H Berry
چکیده

A series of octahedral ruthenium silyl hydride complexes, cis-(PMe(3))(4)Ru(SiR(3))H (SiR(3) = SiMe(3), 1a; SiMe(2)CH(2)SiMe(3), 1b; SiEt(3), 1c; SiMe(2)H, 1d), has been synthesized by the reaction of hydrosilanes with (PMe(3))(3)Ru(eta(2)-CH(2)PMe(2))H (5), cis-(PMe(3))(4)RuMe(2) (6), or (PMe(3))(4)RuH(2) (9). Reaction with 6 proceeds via an intermediate product, cis-(PMe(3))(4)Ru(SiR(3))Me (SiR(3) = SiMe(3), 7a; SiMe(2)CH(2)SiMe(3), 7b). Alternatively, 1 and 7 have been synthesized via a fast hydrosilane exchange with another cis-(PMe(3))(4)Ru(SiR(3))H or cis-(PMe(3))(4)Ru(SiR(3))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 PMe(3)-d(9) 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 PMe(3)-d(9) 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 (approximately 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-(PMe(3))(3)Ru(SiR(3))H(3) (SiR(3) = SiMe(3), 4a; SiMe(2)CH(2)SiMe(3), 4b; SiEt(3), 4c), features hydrides cis to Si. Alternatively, 4a-c have been synthesized by photolysis of (PMe(3))(4)RuH(2) in the presence of a hydrosilane or by exchange of fac-(PMe(3))(3)Ru(SiR(3))H(3) with another HSiR(3). The reverse manifold - HH elimination from 4a and trapping with PMe(3) or PMe(3)-d(9) - is also regioselective (1a-d(9)() is predominantly produced with PMe(3)-d(9) trans to Si), but is very unfavorable. At 70 degrees C, a slower but irreversible SiH elimination also occurs and furnishes (PMe(3))(4)RuH(2). The structure of 4a exhibits a tetrahedral P(3)Si environment around the metal with the three hydrides adjacent to silicon and capping the P(2)Si 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 H(3)SiR(3) fragment. Thermolysis of 1a in C(6)D(6) at 45-55 degrees C leads to an intermolecular CD activation of C(6)D(6). Extensive H/D exchange into the hydride, SiMe(3), and PMe(3) ligands is observed, followed by much slower formation of cis-(PMe(3))(4)Ru(D)(Ph-d(5)). In an even slower intramolecular CH activation process, (PMe(3))(3)Ru(eta(2)-CH(2)PMe(2))H (5) is also produced. The structure of intermediates, mechanisms, and aptitudes for PMe(3) 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.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Titanium-catalyzed dehydrocoupling of silanes: direct conversion of primary monosilanes to titanium(0) oligosilane complexes with agostic alpha-Si-H...Ti interactions.

Polysilane high polymers have been attracting increasing interest owing to their potential applications as photoresists, photoinitiators, thermochromic materials, and precursors to silicon carbide.1 In 1985, Harrod and co-workers discovered that group 4 metallocenes such as Cp2TiMe2 could catalyze the dehydrogenative coupling of primary organosilanes to linear poly(hydrosilanes), H-(SiHR)n-H wi...

متن کامل

Direct synthesis of pyridines and quinolines by coupling of γ-amino-alcohols with secondary alcohols liberating H2 catalyzed by ruthenium pincer complexes.

A novel, one-step synthesis of substituted pyridine- and quinoline-derivatives was achieved by acceptorless dehydrogenative coupling of γ-aminoalcohols with secondary alcohols. The reaction involves consecutive C-N and C-C bond formation, catalyzed by a bipyridyl-based ruthenium pincer complex with a base.

متن کامل

Platinum-oxygen Bond Formation: Kinetic and Mechanistic Studies

Reaction of [PtMe(C^N)(SMe2)] (C^N = 2-phenylpyridinate (ppy); 1a, C^N = benzo[h]quinolate, (bhq); 1b) with hydrogen peroxide gives the platinum(IV) complexes trans-[PtMe(OH)2(C^N)(H2O)] (C^N = ppy; 3a, C^N = bhq, 3b) bearing platinum-oxygen bonds. The Pt(II) complexes 1a and 1b have 5dπ(Pt)→π*(C^N) MLCT band in the visible region which is used to easily follow the kinetic of its reaction with ...

متن کامل

Metal-to-Metal Silyl Migration and Silicon-Carbon Bond Cleavage/Re-formation Processes in the Methylene/Silyl

Ruthenium methylene/silyl complexes of stoichiometry Cp*2Ru2(μ-CH2)(SiR3)(μ-Cl), where SiR3 ) SiMe3 (1), SiEt3 (2), SiMe2Et (3), and SiMe2Ph (4), are produced when [Cp*RuCl]4 is treated with the appropriate dialkylmagnesium reagent, Mg(CH2SiR3)2. Each complex undergoes two fluxional processes as observed by variable-temperature 1H NMR spectroscopy. The low-temperature exchange process is migrat...

متن کامل

Ru-catalyzed dehydrogenative coupling of carboxylic acids and silanes - a new method for the preparation of silyl ester

Ru(3)(CO)(12)/EtI has been found to be an efficient catalyst system for the dehydrosilylation of carboxylic acids with silanes. In the presence of 1 mol% Ru(3)(CO)(12) and 4 mol% EtI, dehydrosilylation reactions in toluene afforded the corresponding silyl esters at 100 degrees C in good and high yields.

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:
  • Journal of the American Chemical Society

دوره 125 26  شماره 

صفحات  -

تاریخ انتشار 2003