Hydridoruthenium complexes

An efficient method for the preparation of tetrafluoroborato complexes is hydride abstraction from metal hydrides using triphenylmethylium tetrafluoroborate.1" This method has been first reported by Sanders for hydridoruthenium complexes.2... 

Sixteen-electron ruthenium(O) species of type (rj6-arene)(L)Ru(0) and containing two-electron ligands are probable intermediates for C—H bond activation and formation of metallacyclic complexes (Section II,A,3,c). A variety of 18-electron complexes of general formula (arene)(L1)(L2)Ru(0) have been prepared by H. Werner and co-workers either by deprotonation of hydride ruthenium(II) complexes or by reduction of cations RuX(L)2-(arene)+. Some of these Ru(0) complexes have already been discussed with the formation of alkyl or hydridoruthenium complexes (Sections... 

Allyl trimethylsilyl ethers have been shown to isomerize in good yields to silyl enol ethers in the presence of various hydridoruthenium complexes such as [H2Ru(PPh3)4] [equation (6)], thus making allyl alcohols potential synthetic... 

A most significant advance in the alkyne hydration area during the past decade has been the development of Ru(n) catalyst systems that have enabled the anti-Markovnikov hydration of terminal alkynes (entries 6 and 7). These reactions involve the addition of water to the a-carbon of a ruthenium vinylidene complex, followed by reductive elimination of the resulting hydridoruthenium acyl intermediate (path C).392-395 While the use of GpRuGl(dppm) in aqueous dioxane (entry 6)393-396 and an indenylruthenium catalyst in an aqueous medium including surfactants has proved to be effective (entry 7),397 an Ru(n)/P,N-ligand system (entry 8) has recently been reported that displays enzyme-like rate acceleration (>2.4 x 1011) (dppm = bis(diphenylphosphino)methane).398... 

The mechanism of the homocoupling of dienes is one of the representative reactions proceeding through a n-allylruthenium intermediate. Indeed, a bis 7r-allylruthenium complex was produced by oxidative cyclization of two dienes and the coupling of the terminal carbon atoms led to a cationic (diene) (allyl)hydridoruthenium species. 

Other ruthenium-based catalysts for the aerobic oxidation of alcohols have been described where it is not clear if they involve oxidative dehydrogenation by low-valent ruthenium, to give hydridoruthenium intermediates, or by high-valent oxoruthenium. Masutani et al. [107] described (nitrosyl)Ru(salen) complexes, which can be activated by illumination to release the NO ligand. These complexes demonstrated selectivity for oxidation of the alcoholic group versus epoxidation, which was regarded as evidence for the intermediacy of Ru-oxo moieties. Their excellent alcohol coordination properties led to a good enantiomer differentation in the aerobic oxidation of racemic secondary alcohols (Fig. 19) and to a selective oxidation of primary alcohols in the presence of secondary alcohols [108]. 

Apart from hydridoruthenium carbonyl cluster compounds (see Sections 45.10.3.3 and 45.10.4) the only Ru° hydride complexes are the deep brown [RuH(NO)(PR3)3] (R3 = Ph3, Ph2Me, Ph2Pr , Ph2Cy) w hich are fully discussed in Section 45.5.1.2. 

As yet, the C-N bond-cleavage reaction is relatively rare. A (pentamethylcyclopen-tadienyl)ruthenium complex RuCp X2 and a hydridoruthenium(II) complex RuHCl(CO)(PPh3)3 are reported to cleave the C-N bond in allylamine to give corresponding -allylmthenium(II) complexes [68, 69]. The major driving force for this... 

This is the rate-determining step involving heterolytic splitting of the hydrogen molecule and formation of an hydridoruthenium(II) complex. The next step involves rearrangement of the hydrido-7r-olefin complex to a (T-alkyl complex via insertion of the olefin into the metal hydride bond. Finally, electrophilic attack occurs on the metal-bonded carbon... 

Similar C-N bond cleavage of allylamine by hydridoruthenium(II) is also reported to give an J7 -allylruthenium(II) complex (Eq. 3.40) [157]. 

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