Über die Einwirkung von Wasserstoff auf einige metallorganische Verbindungen und Komplexe

Can. J. Chem. 68, 471 (1990). Dimethyltitanocene is an excellent catalyst for the redistribution of alkoxy-and siloxyhydrosilanes. The redistribution reactions of triethoxysilane, diethoxymethylsilane, 1,3,5,7-tetramethylcyclotetrasiloxane, pentamethyldisiloxane, and H-(SiMe20),-SiMe2H ( n = 1 to 3) are described. The mechanism of these reactions is discussed in terms of TiH mediated displacements. The possibility of both Ti(II1) and Ti(IV) mediated displacements are considered and a mechanism involving the former, which fits all of the experimental data, is proposed.Key words: siloxanes, alkoxysilanes, redistribution, catalysis, dimethyltitanocene.SHIXUAN XIN, CLARE AITKEN, JOHN F. HARROD, YING MU et E. SAMUEL. Can. J. Chem. 68, 471 (1990) Le dimkthyltitanoc&ne est un excellent catalyseur pour la redistribution des alcoxy-et siloxyhydrosilanes. On dCcrit les rCactions de redistribution du triCthoxysilane, du diCthoxymCthylsilane, du 1,3,5,7-t~tramCthylcyclotCtrasiloxane, du pentamCthyldisiloxane et des H-(SiMe20),-SiMe2H( n = 1 a 3). On discute du mkcanisme de ces rkactions en fonction de dCplacements effectuCs sous l'influence du TiH. On a considCrC la possibilitC que les dCplacements s'effectuent sous l'influence du Ti(II1) ainsi que du Ti(1V) et on propose une mecanisme impliquant le premier qui permet d'expliquer l'ensemble des donnCes expCrimentales.

Section: Reactions Of Alkoxysilanes With Dimethyltitanocenesupporting

confidence: 61%

“…Dimethyltitanocene was synthesized by a literature procedure (5). The following compounds were obtained from Petrarch Systems Inc.: E'E', E'E, E'DE', E1D2E', E1D3E', D4, D4', D5, (MeO)3SiH, and Me(EtO)2SiH.…”

Section: Methodsmentioning

confidence: 99%

Redistribution reactions of alkoxy- and siloxysilanes, catalyzed by dimethyltitanocene

Xin¹,

Aitken²,

Harrod³

et al. 1990

“…Silanes were prepared by LiA1H4 reduction of the appropriate chlorosilane using modifications of literature methods (17). Dimethyltitanocene was prepared by a literature procedure (9) and freshly recrystallized before use.…”

Section: Materials and Reagentsmentioning

confidence: 99%

Structural studies of oligosilanes produced by catalytic dehydrogenative coupling of primary organosilanes

Aitken¹,

Harrod²,

Gill³

1987

The structures of some poly(organosilylenes), [Formula: see text] (R = Ph, p-tolyl, n-hexyl, and benzyl), produced by catalytic dehydrogenative coupling of primary silanes have been studied by infrared, nuclear magnetic resonance, and mass spectroscopies. These results, combined with data on molecular weights and molecular weight distributions from vapour pressure osmometry and gel permeation chromatography, lead to the conclusion that the polymers are linear and have SiH2R end groups. The polymers all have degrees of polymerization of ca. 10 and very narrow molecular weight dipersions. Some possible features of the mechanism that gives rise to this behaviour are discussed.

“…The critical feature of the DMT reactions, and one which distinguishes DMT from its zirconium and hafnium analogues, is the explosive nature of the reaction that leads to reduced titanium species. In its strongly autocatalytic nature and its spatially inhomogeneous propagation, this reaction is very similar to the reaction of Hz with DMT (6,10). It is likely in both cases that titanocene is the chain carrier that is responsible for the branched chain character of these reactions.…”

Section: The Reactions Of Dipherzylsilarze and Metlzylplzenylsilanementioning

confidence: 82%

Organometallic intermediates in the group 4 metallocene-catalyzed dehydrocoupling of organosilanes. 2. Variations in the intermediates of dimethyltitanocene reactions with several silanes

Harrod¹,

Mu²,

Samuel³

1992

2980 (1992). As previously described, organosilanes react with dirnethyltitanocene (DMT) to give three reduced titanium intermediates, CpzTi(k-SiRRIH)(p-H)TiCpz, 1, [Cp.Ti(k-SiRR'H)],, 2, and [Cp2Ti(H)],(~-H), 3. When R = Me and R' = tz-Bu, the DMT is quantitatively converted to 1, which is persistent at room temperature. When R' = H, DMT is initially converted quantitatively to 1, which then rapidly declines to give an equilibrium mixture of 1, 2, and 3, with 2 as the dominant species. When R = Ph and R' = Ph or Me, 1 is again produced quantitatively, but it rapidly declines to produce an unidentified paramagnetic product, rather than 2 or 3. It is believed that 2 is unstable with respect to dissociation in these cases due to the steric bulk of the substituents. [Traduit par la rkdaction]