Platinum complexes alkenyl

Platinum complexes (continued) with aryls, thallium adducts, 3, 399 with bis(alkynyl), NLO properties, 12, 125 with bisalkynyl copper complexes, 2, 182-186 with bis(3,5-dichloro-2,4,6-trifluorophenyl), 8, 483 and C-F bond activation, 1, 743 in C-H bond alkenylations, 10, 225 in C-H bond electrophilic activation studies, 1, 707 with chromium, 5, 312 with copper, 2, 168 cyclometallated, for OLEDs, 12, 145 in diyne carbometallations, 10, 351-352 in ene-yne metathesis, 11, 273 in enyne skeletal reorganization, 11, 289 heteronuclear Pt isocyanides, 8, 431 inside metallodendrimers, 12, 400 kinetic studies, 1, 531 on metallodendrimer surfaces, 12, 391 mononuclear Pt(II) isocyanides, 8, 428 mononuclear Pt(0) isocyanides, 8, 424 overview, 8, 405-444 d -cP oxidative addition, PHIP, 1, 436 polynuclear Pt isocyanides, 8, 431 polynuclear Pt(0) isocyanides, 8, 425 Pt(I) isocyanides, 8, 425 Pt(IV) isocyanides, 8, 430... 

Hexachloroplatinic acid and other platinum complexes are mainly used as soluble catalysts for the additive cure. The most active catalyst used recently for vulcanization of silicon rubber is the platinum-alkenylsiloxanes complex, mainly the platinum-vinylsiloxane complex (Karstedt s catalyst) (4). One important approach to the activated cure of silicone rubber makes use of various inhibitors or moderators added to the platinum catalyst to reduce, or temporarily inhibit, its catalytic activity in the presence of the alkenyl- and hydropolysiloxanes (see catalysis by Pt complexes). The catalyst is usually added to the reaction mixture in quantities related to the number of unsaturated (e.g., vinyl) substituents in the polysiloxane. Vinyl-terminated polydimethylsiloxane polymers (viscosity > 200 cSt) are typically cross-linked by methylhydrosiloxane-dimethylsiloxane copolymer with 15-50 mol% of polymethylhydrosiloxane. A typical catalyst is a platinum complex in alcohol, xylene, divinylsiloxanes, or cyclic vinylsiloxanes. The system is usually prepared in two parts (part A, vinylsiloxane -I- Pt (5-10 ppm) part B, hydrosiloxane -I- vinylsiloxane). Inhibitors stop the platinum catalyst they are volatile or react with silicone hydride cross-linker to become a part of the polymer network. Some of them are decomposed by heat or light (UV). A single-component system contains fugitive inhibitors of Pt. 

Formation of a siloxane network via hydrosilylation can also be initiated by a free-radical mechanism (300-302). A photochemical route makes use of photosensitizers such as peresters to generate radicals in the system. Unfor-timately, the reaction is quite sluggish. Several complexes of platinum such as (jj-cyclopentadienyl)trialkylplatinum(rV) compoimds have been found to be photoactive. The mixture of silicone polymer containing alkenyl functional groups with silicon hydride cross-linker materials and a catalytic amoimt of a cy-clopentadienylplatinum(IV) compound is stable in the dark. Under UV radiation, however, the platinum complex imdergoes rapid decomposition with release of platinum species that catalyze rapid hydrosilylation and network formation (303-308). Other UV-active hydrosilylation catalyst precursors include (acetylacetonate)Pt(CH3)3 (309), (acetylacetonate)2Pt (310-312), platinum tri-azene compounds (313,314), and other sytems (315,316). 

The treatment of cyclopentadienyI-metal-2-alkenyl carbonyl complexes, such as 274 and 275, with SO2 leads to the formation of thietane 1,1-dioxide as ligand (Eqs. 73 and 74). Thietane and platinum(II) have also been found... 

Platinum(II) complexes with alkenyls, characteristics, 8, 471 with alkynyls, characteristics, 8, 538 into 7 3-allyl complexes, 8, 652 with arylenes, bisaryls, macrocycles, 8, 491 with aryls... 

After these pioneering studies, a number of other research groups reported on the cleavage of C-H bonds via the use of a stoichiometric amount of transition-metal complexes [7]. To date, several types of catalytic reactions involving C-H bond cleavage, for example, alkyl, alkenyl, aryl, formyl, and active methylene C-H bonds have been developed [8]. In many cases,for these types of catalytic reactions, ruthenium, rhodium, iridium, platinum, and palladium complexes all show catalytic activity. 

Borylation of 1-alkenyl iodides and triflates with HBpin was catalyzed by palladium catalyst in the presence of Et3N (Equation (61)).330 Platinum(0)-AsPPh3 complexes catalyzed the borylation of allyl chlorides (Equation (62)).331,332... 

A general approach to alkenylplatinum(II) complexes involves the use of alkenyl triflates. Reaction of [Pt(PPh3)4] produces an alkenyltris(triphenylphosphine)-platinum(II) cation, whereas with [Pt(PPh3)2(C2H4)] a complex with coordinated triflate is obtained ... 

As outlined in previous volumes, the chemistry of ylides coordinated to noble metals, particularly palladium, platinum and gold continues to attract most attention. Refluxing (dppm)palladium(II) dichloride [dppm = bis(diphenylphosphino)methane] with alkynes in mixtures of 1,2-dichloro-ethane/l,4-dioxane provides a novel route to palladium-bound alkenyl phosphorus ylide complexes (53) (Scheme 1)P The reaction represents the... 

Furthermore, the reaction of Pt[(p-tol-C=CH)](PPh3)2 with DCl forms an alkenyl complex in which the deuterium is exclusively cis to platinum. 

Cationic platinum(II) acetylene complexes react with a variety of nucleophiles. Chisholm and Clark showed that the reaction of methanol with coordinated disubsti-tuted acetylenes (generated in situ) affords trans u-bonded vinyl ether complexes (Equation 11.35). The trans stereochemistry of the cr-vinyl group of the product suggests that the nucleophilic attack occurs external to the metal and does not involve prior coordination of methanol, Reger has shown that stable cationic iron-alkyne complexes undergo reaction with a wide variety of nucleophiles to give stable cr-alkenyl complexes resulting from trans attack of the nucleophile on the coordinated acetylene (Equation 11.36). A variety... 

Several independent protocols using a combination of transition metal-catalyzed stereoselective hydrosilylation, such as palladium-catalyzed crosscoupling sequence leading to stereodefined r-conjugated alkene derivatives, have been successfully developed in the last decade (4). Alkenylsilanes or siloxanes, prepared via platinum or rhodium complex-catalyzed intermolecular hydrosilylation of terminal alkynes have been highly stereospecifically cross-coupled with aryl and alkenyl halides to give unsymmetrical stilbenes, alkenylbenzenes, and conjugated dienes (Scheme 24) (4). 

Indole derivatives tethered by alkenyl or allenyl groups undergo efficient intramolecular hydroarylation. Treatment of 2-(4-pentenyl)indoles with a catalytic platinum/chiral phosphine complex induced intramolecular hydroarylation to give tetrahydrocarbazole in 93% yield with 90% ee (Scheme 18.14) [13], The similar intramolecular asymmetric hydroarylation was applied to indoles having internal olefins by use of a highly strained planar chiral platinacycle (Scheme 18.15) [14],... 

Unique 30-membered diphosphine 40 and 45-membered triphosphine 41 macrocycles were obtained via a Grubbs type methathesis coupling of the terminal unsaturated groups at the ends of lengthy alkenyl substituents of coordinated phosphines in trans square-planar platinum and facial octahedral tungsten complexes (Scheme 12.17) [56]. 

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