Karstedt’s catalysts

A PEO macroinitiator with Si — H end groups was prepared through the condensation of monohydroxy-terminated PEO with CISiMePhH in the presence of pyridine [130]. The presence of the Si —Ph moiety prevents the hydrolysis of the Si — O — C bond, due to steric factors. This macroinitiator was subsequently used for the synthesis of poly(ferrocenyldimethylsilane), PFS, to afford PEO-fc-PFS block copolymers. The ROP of the ferrocenophane was conducted catalytically using the Pt(0) Karstedt s catalyst in toluene at 25 °C (Scheme 55). Rather broad molecular weight distributions (higher than 1.3) were obtained. 

Combining two different hydrosilylation catalysts in sequence with chlorodimethylsilane has allowed the construction of complex dye assemblies and conducting polymers. In the example shown (Scheme 8), Karstedt s catalyst was chosen after a brief screen for the hydrosilylation of an aromatic diyne with chlorodimethylsilane. After reduction of the chlorosilane, an equimolar mixture of disilane B and diyne A was treated with a catalytic amount of Wilkinson s catalyst, resulting in the formation of polymer C.42 Hydrosilylation of alkynes has also been studied as a means of synthesizing oligo(phenylenevinylene) units with pendant alkoxysilanes to create curable, hole-transporting films.43,43 ... 

Karl Fischer titrators, 23 477 Karmen-vortex street, 11 668 Karr RPC plate, 10 779-780 Karstedt s catalyst, in silicone network preparation, 22 563 Karstenite, 5 785t Karyoplasts, 12 451, 458 Kashin-Beck disease, selenium and, 22 101 Kaspar s dynamic filter, 11 384 Katapinands, 24 44 Kauri-butanol value, 23 89 Kazakhstan... 

Silane redistribution 6 mg of (3-(methylsilyl)propyl) triphenylphosphonium hexafluorophosphate(V) (0.0121 mmol, 1 equivalent), 93 mg of Karstedt s catalyst (Pt 3.91% 0.000954 mmol, 0.8 equivalent), 6 mg of triphenylphosphine (0.0229 mmol, 1.9 equivalent) were dissolved in 20 mL of freshly distilled fluoroben-zene in a 50 mL Schlenk flask in an inert atmosphere glovebox. The flask was equipped with a septum, removed from the glovebox and installed with PEEK tubing leading to the mass spectrometer. The flask was pressurized with N2 and monitored by ESI-MS. Once a steady signal was obtained, 0.15 g of freshly distilled phenylsilane (1.39 mmol, 115 equivalents) was injected into the reaction flask. The reaction was initiated at room temperature and then was heated to reflux after 20 min to drive it to completion. 

Another example of the data provided by our approach is shown in Fig. 4, which tracks the platinum-catalyzed redistribution of two silanes [16], one charge-tagged with a phosphonium group. This demonstrates the ability of the technique to monitor air-sensitive reactions in non-routine solvents in this case, fluorobenzene. The temperature of the reaction was increased from room temperature to reflux at 20 min the catalyst used was Karstedt s catalyst, Pt[(H2C = CHMe2Si)20]2(Fig.5). 

It is likely that more silicon-carbon bonds are produced by the hydrosilylation of olefins than by any other method except the direct process. This deceptively simple addition of an Si-H bond to a C-C multiple bond can be promoted by a variety of means, but transition metal catalysis is by far the most significant. Two relatively old catalysts, H2PtCl6 ( Speier s catalyst ) and Pt2(Me2ViSiOSiMe2Vi)3 ( Karstedt s catalyst ), remain the most effective, and the remarkable rates and turnover numbers observed in these systems are among the most impressive in all of organometallic chemistry. The bulk of the literature on hydrosilylation falls outside the scope of this review, and readers are directed to the comprehensive work on hydrosilylation edited by Marciniec.93... 

Remarkable effects of non-vicinal, proximate polar groups on the reaction rates are disclosed in the hydrosilylation of substituted bicyclo[2.2.1]hept-5-enes (8) catalyzed by Pt[(CH2=CHSiMe2)20]2 (Karstedt s catalyst)1011 or PtCL (equation 6)12. Endo-2,3-dicarboxylic iV-phenylimide 8c does not react at all and the reaction of endo-2,3-dicarboxylic anhydride 8a is unusually slow. On the contrary, the reaction of exo-imide... 

Intramolecular hydrosilylations of functionalized alkenes followed by hydrogen peroxide oxidation provide powerful methods for organic syntheses86-88. The reactions of allylic O-dimethylsilyl ethers 59 promoted by platinum catalysts, e.g. Karstedt s catalyst and Pt(PPh3)2(CH2=CH2), or rhodium catalysts, e.g. Rh(acac)(COD) and [RhCl(CH2=CH2)2]2> proceed via 5-endo cyclization to give oxasilacyclopentanes 60 with a couple of exceptions in which siloxatanes 61 are formed (Scheme ll)87,89. 

Intramolecular hydrosilylation of O-dimethylsilylalkenoate 71, promoted by Karstedt s catalyst, provides an efficient route to cw-4-methyl-5-substituted-y-lactone 73 (cis/trans = 76/24-98/2) in 21-87% yield (equation 29)92. The reaction proceeds through 5-endo cyclization exclusively. The stereoselectivity of the reaction is highly... 

In the reaction of HMe2SiOCMe2CH=CH2 using Karstedt s catalyst in pentane at ambient temperature, an eight-membered ring product 75 is formed (35% yield) besides... 

The reaction of bis(trimethylsilyl)ethyne (118) with a high boiling hydrosilane, HSiMe2C6Hi3-n, promoted by Karstedt s catalyst affords normal ris-addition product... 

The hydrosilylation-polymerization of 1,3-diethenyltetramethyldisiloxane (276) with 1,3-dihydrotetramethyldisiloxane (275) proceeds smoothly in the presence of Karstedt s catalyst to give high molecular weight poly[(l,l,3,3-tetramethyldisiloxanyl)ethylene] (277) (equation 104)273-274. 

Hydrosilylations of buckminsterfullerene (Cgo) with a poly(hydrosiloxane) (301) or H(SiMe20)3SiMe2H in the presence of Karstedt s catalyst (vide supra) proceed smoothly at 29 °C to give the corresponding (1 1) Cgo-polysiloxanes (302) with molecular weights of 5000 and 4000, respectively (equation 112)297. 

Karstedt s catalyst, nickel analog, 8, 138-139 Kedarcidin, via ring-closing diene metathesis, 11, 208-209 Kendomycin, via ring-closing metathesis, 11, 239 KERD, see Kinetic energy release distribution Ketenes, niobium complexes, 5, 84 Ketenimines... 

In a typical synthesis PEO (O.lOg), THE (3.0mL), and 5 x SiH functionalized PDMS elastomer disks (ca. 63.0mg/disk) were combined in a sample vial and stirred for one hour to allow the system to reach equilibrium. Karstedt s catalyst (10 (aL) was added and the vials were left to stir for 16h. The disks were washed with H CCl (3 x5mL), EtOH (3x5mL), water (3x5mL, after which PEO was not detected in the wash water), EtOH (3x5 mL), and H CCl (3x5 mL) and dried under vacuum for 24h. ATR-ET-IR 2961 2873 2163 (Si-H) 1050 (Si-O-Si)... 

Vinyltrimethylsilane (97%), trimethylchlorosilane (98%), chlorodimethylsilane (97%), bromoform (96%), 5-bromo-l-pentene (95%), nBuLi (2.5M solution in hexanes), MeLi (1.6M solution in diethyl ether), n-decane (puriss. p.a., standard for GC, > 99.8%) and hexachloroplatinic(lV) acid hydrate were purchased from Aldrich. Platinum divinyltetramethyldisiloxane complex (Karstedt s catalyst, 3% solution in xylenes), hexamethyl-cyclotrisiloxane (95%), vinylmethyldichlorosilane (97%) and 1,1,3,3-tetramethyldisiloxane (97%) were bought from ABCR. Bromine (puriss) was bought from Eluka. Triethylamine (pure for analysis) and zinc oxide (pure) was purchased from Chempur. Solvents (tetrahydrofurane, diethyl ether, methylene chloride, pentane, ethyl acetate) were supplied by POCh (Polish Chemical Reagents). 

Pt(0) (vinylMe2Si-0-SiMe2vinyl)i 5 Karstedt s catalyst, platinum divinyltetramthyldisiloxane complex Scheme 1 Homogeneous platinum catalysts... 

The influence of temperature was also assessed on these two catalysts. The results are presented in Fig. 4 for M42 and show that decreasing the temperature to 40°C led to a very slow reaction with DCPPtClj whereas the rate remained almost identical for Karstedt s catalyst. 

Fig. 3 Comparison of hydrosilylation kinetics with DCFFtCl ( ) and Karstedt s catalyst ( ). [C = C] = [Si-H](, = 0.1M. Right graph zoom of the beginning of the reaction...

For Karstedt s catalyst, the same calculation showed that the overall kinetic order could be either 2 or 3, both curves F (a)=f(t) presenting similar shapes. We therefore could not express the reaction rate for this system. 

This kinetic study enabled ns to show that both DCPPtCl and Karstedt s catalyst are satisfying catalysts for liqnid crystal moieties, leading to ca. 80% of conversion at 60°C ([C=C](,=[Si-H]jj=0.1M, Pt qnantity 40ppm) after 2 honrs of reaction. In order to ensure a full conversion in silane, the time of reaction had to be increased to 24 h. 

At last, Hamaide et al. described also shortly their attempts for performing directly the hydrosilylation without protective groups. In addition to incompatible solubilities, they observed up to 50% 0-silylation, instead of C-silylation with Karstedt s catalyst (Platinium divinyltetramethyldisiloxane complex) [21]. 

Treatment of Ceo with poly(hydrosiloxane) in the presence of Karstedt s catalyst proceeds to give Ceo-polysiloxanes (equation 20). ... 

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