Hydrido-vinyl complex

Reactions of the hydrido(hydroxo) complex 2 with several substrates were examined (Scheme 6-14) [6]. The reactions are fairly complicated and several different types of reachons are observed depending on the substrate. Methyl acrylate and small Lewis bases such as CO, P(OMe)3, BuNC coordinate to the five-coordinated complex 2 affording the corresponding six-coordinate complexes. In reactions with the unsaturated bonds in dimethylacetylenedicarboxylate, carbon dioxide, phenylisocyanate indications for the addition across the O-H bond but not across the Os-OH bond were obtained. In reactions with olefins such as methyl vinyl ketone or allyl alcohol, elimination of a water molecule was observed to afford a hydrido metalla-cyclic compound or a hydrido (ethyl) complex. No OH insertion product was obtained. 

The main species in solution has been identified to be the hydrido-alkynyl complex [IrH(C2Ph)(cod)(//2-iPrPCH2CH2OMe)]+BF4 (23). This is, however, only a sink that results from direct reaction of 22 with the 1-alkyne, draining the active catalyst from the system. The catalysis proceeds via the dihydrido-diene intermediate [IrH2(cod)(//2- PrPCH2CH2OMe)]+ BF4 (24), which reacts reversibly with the alkyne to yield the hydrido-iridium-styryl complex 25, followed by a rate-determining reaction of this hydrido-vinyl species with hydrogen to re-... 

Electron-rich iridium(l) complexes can perform C—H activation reactions under mild conditions [13]. In this line, acetone-dis solutions of the [(ri -l,3,5-C 5H3Me3)) lr(Ti -C2H4)(P Pr3)]BF4 complex, at room temperature, show deuterium incorporation to the ethane ligand, most likely due to the participation of hydrido vinyl iridium(lll) species, formed by the C—H activation of ethane, according to Scheme 2.25 [21]. 

The hydrido-/i2-q, q2-vinyl complex (79), which is obtained from reactions between H2Os3(CO),0 and acetylene (124) or ethylene (125) under mild conditions, loses a molecule of CO on heating to give the pale yellow 3-vinylidene derivative (80). 

The transition metal complex-catalyzed formation of 1,3-dioxepanes from vinyl ethers has also been described. For example, reaction of allyl vinyl ether 157 with a nonhydridic ruthenium complex at higher temperatures and without any solvent produced 1,3-dioxepane 159 whereas, the use of a hydridic ruthenium complex resulted in the formation of vinyl ether 158 by double-bond isomerization (Scheme 43). It was suggested that cyclic acetal formation proceeds via a 7i-allyl-hydrido transient complex, which undergoes nucleophilic attack of the OH group at the coordinated Jt-allyl <2004SL1203>. 

The hydrido-vinyl species of iridium(III), Ir(acac)(H)(C2H3)L(Pi-Pr3), L = py, j-Pts, obtained from Ir(acac)(C2H4)(Pi-Pr3) via intramolecular oxidative addition of a coordinated ethylene ligand under UV irradiation , represents a useful starting material for the preparation of vinylidene iridium complexes. 

Reactions between hydrido complexes and unsaturated hydrocarbons generally proceed in two steps. The first step involves coordination of the hydrocarbon to form a 7r-complex followed by hydrido ligand migration and the formation of the product possessing metal-carbon bond. Dependent upon the hydrocarbon alkyl, alkenyl, allyl, or vinyl complexes may be formed ... 

Oxidation of C2D4 leads to CD3CDO, and therefore, most probably in the transition state, hydrido palladium complex containing coordinated vinyl alcohol molecule is formed [equation (6.112)]. 

Trimethyl- and dimethyl-tin hydrides react photochemically with penta-carbonyltrifluorovinylrhenium to give reduced vinyl complexes (88)— (90) the rrawj ifluorovinyl complex (90) is the major product, and a free-radical addition-elimination mechanism has been postulated. Hydrido-pentacarbonylmanganese reacts with bis(trifluoromethyl)diazomethane to form the complex (CF3)2CH Mn(CO)j. The reaction of HMnCCX)) with... 

Type n mechanism starts from oxidative addition of REH to transitimi metal complex ([M]) to give chalcogenolato-hydrido metal complex, [M]H(ER) (Scheme 2). In the next step of alkyne insertion, there are two possible pathways, [M]-H insertion (hydrometalatiOTi) to give [M](ER)(vinyl) and [M]-E insertion (chalcogenometalation) to give [M]H(2-RE-vinyl). In the final stage, reductive... 

Finally, the unusual ruthenium hydrido complex HRu(PPh3)3[HC=C(Me)C(0)0C4H9] is formed in the reaction between H2Ru(PPh3)4 and n-butylmethacrylate77). The Ru atom has oxidatively added to a vinylic C-H bond, and this compound represents the first example of such a structure. 

It is noteworthy that computational and experimental studies have shown that the formation of ruthenium-vinylidenes from terminal alkynes and ruthenium hydride complexes also proceeds via the formation of t -vinyl intermediate (Scheme 8.4) [14]. Thus, in this case the vinylidene ligand is not formed directly from the alkyne, and its /3-hydrogen atom arises from the hydrido ligand. 

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