Vaska complex, reaction with

Reactivity with thiolates 6, 3.8.3.6.3 IrCl(CO)(PPh3)2, Vaska s Complex Reaction with ArN2 8,4.8.2.13.1 Reaction with N2O4 8, 4.8.2.1 Reaction with NaSeCN 8, 4.8,2.20.3 C37H3 ClIrOP2 IrCl(CO)[P(C6H5),l2... 

An unusual sulfur-nitrogen donor, benzothiazole-2-thiolate (58), has been reacted with Vaska s complex to produce 59 in high yield no bidentate adducts of 58 are produced even in refluxing solvent (156). Upon reaction with dioxygen, the extremely sensitive and reactive complex 60 is produced. Addition of water to 60 caused rearrangement to the carboxylate complex 61, while the addition of sulfur dioxide to 60 produces 62 (see Scheme 11). A proposed mechanism for the reaction of water with 60, based on labeling experiments, was outlined and can be found in Scheme 12. 

Silylation of arenes was reported to take place with rhodium and iridium complexes as the catalyst. The Vaska complex effects the reaction of benzene with pen-tamethyldisiloxane,230 whereas [RhCl(CO)(PMe3)2] catalyzes the formation of C—Si bonds under irradiation231 [Eq. (10.39)] 232... 

In 1982, Curtis and co-workers reported that Vaska s complex promotes the formation of phenylsiloxanes from the reaction of hydridosiloxanes and benzene in a catalytic, albeit low-yield, process.93 Catalytic arylsilane formation has also been reported by Tanaka and co-workers. Under photo-lytic conditions, RhCl(CO)(PMe3)2 catalyzes the C-H bond activation of arenes in reactions with hydrosilanes or disilanes, leading to the formation of new silicon-carbon bonds.94 More recently, C-H bond activation of arenes resulting in arylsilane formation has been observed in the... 

L. Vaska and J. W. DiLuzio, On the origin of hydrogen in metal hydride complexes formed by reaction with alcohols, J. Am. Chem. Soc., 8 (1962) 4989 1990. 

The main problem with the reaction of metal centres with 02 is its tendency to react irreversibly with oxidation of the metal centre, to form either cis dioxo species or pi oxo bridged binuclear complexes (Scheme 2.4a). However, in cases where there is a strong driving force towards lower oxidation states, the reaction is somewhat reversible, e.g. reaction with Vaska s compound (Scheme 2.4b). The role of the haem centre in haemoglobin is to ensure not only that is 02 binding reversible, but that both its complexation and release occur rapidly and at the correct concentrations. These concentrations, or partial pressures, must correspond to those found in the lung and intracellular medium, respectively. 

The X-ray structure of 170 has been reported (56). Generally only unsubstituted sp -hybridized carbon atoms of butadiene ligands are attacked by HFA (133). Different behavior has been found in the reactions of iridium complexes with HFA. With tris(triphenylphosphane)nitrosyliridium the geometry is retained [Eq. (139)] (63). However, the Vaska complexes lead to... 

A similar situation is encountered in reactions with transition metal complexes where the fullerenes behave much like large olefins. For example, the addition of Vaska-type iridium complexes, such as Ir(CO)Cl(PR3)2, to fullerenes which has proven to be an effective way of obtaining materials that are suitable for crystallographic studies 88... 

The most important lr(I) complexes are rra/ 5-IrCl(CO)(PPh3)2 (Vaska s complex) and its phosphine derivatives, since they provide clear examples of oxidative addition reactions. Scheme 11.5 summarizes the addition reactions to IrCl(CO)(PPh3)2 [72]. Alkyl halides, acyl halides. H.. and SnCl4 oxidatively add to the Ir center, and reactions with O2. alkyne. CO. and SO2 give their coordinated complexes without complete cleavage of the appropriate bond. 

The great majority of o-acetylide transition metal complexes are prepared by interaction of a metal halide with acetylide, RC C", or the formal oxidative addition of terminal alkynes or alkynyl stannanes to the metal center. As amply demonstrated in the previous section, alkynyliodonium salts may serve as electrophilic acetylene equivalents. In other words, transition metal complexes may act as nucleophiles in reactions with alkynyliodonium species. Indeed, the reaction [81] of the square planar Vaska s complex, 106, and its Rh analog, 107, with a variety of alkynyliodonium triflates in toluene results in 89-96% isolated yield of the hexa-coordinate o-acetylide complexes, 108 and 109 [Eq. (58)]. Reaction is essentially instantaneous and occurs with retention of stereochemistry around the metal center. 

---