Vaska-type complex

Carbonyl derivatives can be made similarly, either by abstracting CO from the solvent, by direct introduction or by oxidative addition to a Vaska-type complex ... 

Molecular oxygen adducts. Despite many physical studies, the bond length of co-ordinated oxygen can still be interpreted as either superoxide (or peroxide) ion, or an electronically excited state of molecular oxygen. In order to establish the bond character more clearly, a n.m.r. study has been carried out on several complexes, including [Rh(02)(Ph2PC2H4PPh2)]Cl. Unfortunately, no resonance attributable to O2 could be found, suggesting that Vaska type complexes tumble at a rate which broadens the resonances beyond... 

The iridium(I) Vaska-type complexes (rans-[Ir(X)(CO)(PPh3)2] readily undergo oxidative addition with a wide variety of reagents to yield iridium(III) products.81 Kinetic data for oxidative addition to rans-[Ir(Cl)(CO)(PPh3 )2] are usually interpreted in terms of two limiting mechanisms ... 

The iridium(I) species [Ir(CO)(t/2-CSNMe2)(PPh3)(S2CNMe2)](X) (66 X = Cl, PF6) is formed upon reaction of [Ir(Cl)(CO)(PPh3)2] with (MeNCS)2.165 Vaska-type complexes presumably react with Me2NCSCl in a similar manner to yield (ra s-[Ir(Cl)(CO)(f/2-CSNMe)2(PPh3)2]+. 

Mechanistic and kinetic studies have been carried out on some oxygenated Vaska-type complexes. Using 0-labeled complexes shows that insertion occurs into the Ir—O rather than into the O—O bond (23). 

Steric effects also play a role in thermodynamics and kinetics of dioxygen binding to Vaska-type complexes. For example, ort/zo-substituents on arylphosphine ligands significantly decrease the oxygenation rate or even completely shut down the... 

Tuning Rhodium (I) Metal Centre A ccessibility in lodomethane Oxidative Addition to Vaska-type Complexes by Interchanging Tertiary Phosphine for Arsine and Stibine... 

As shown in Table 1, the As-Rh-As moiety in 2 (4.824(1) A) is significantly longer than that of P-Rh-P in 1 (4.665(1) A). This in turn means there is a larger cavity for entering nucleophiles in the arsine Vaska-type complex compared to the sterically more hindered phosphine analogue. 

It was shown that these Vaska-type complexes of rhodium(i) are excellent model complexes to study basic effects, including the use of molecular structure information to explain solution effects on reaction mechanisms. However, additional research is still required to aid in understanding solution behaviour of these systems. 

To determine whether CO exchange occurs between Vaska type complexes [MX(CO)(PR3)2, M = Rh, Ir], 13C enriched RhCl(CO)(PPh3)2 was allowed to react at room temperature with several Rh(I) and Ir(I) complexes (3). In <60 seconds the intensity of the 13CO IR absorption due to RhCl(CO)(PPh3)2 and the l3CO absorption due to the other reactant species were of equal intensity indicating random redistribution had occurred. Values for v(12CO) and v(,3CO) are shown in Table II. 

In a work which is relative to the problem of C-H bond addition, Goldman and coworkers have investigated the thermolysis of fra -Ir( Pr3)2(CO)-C1(H) C6H5) affording benzene and the Vaska-type complex IrL2(CO)Ct [41J. 

The reactivity of Qo comparable to that of electron deficient conjugated olefins is nicely reflected by reactions with transition metal complexes. A variety of single crystal structures and spectroscopic studies show that the complexation of transition metals to the fullerene core proceeds in a dihapto manner or as hydrometalation reactions rather than in rf- or ] -binding mode. This was elegantly demonstrated by the reaction of Cgg with ruthenium complexes (Scheme 8) [144]. A variety of iridium complexes ( ] -Cgo)Ir(CO)Cl(PR R R )2 were synthesized by allowing Cgg to react with different Vaska-type complexes Ir(CO)Cl(PR R R )2 [145]. ] -Complex formation was also observed upon reaction of Cgo with other Ir [146] as well as Rh [147] complexes. Hydro-metallation was obtained with Cp2Zr(H)Cl [140]. 

Table 1 Calculated energies for addition of H2 to rhodium Vaska-type complexes...

See also Factors influencing the thermodynamics of molecular hydrogen oxirlation addition to Vaska-type complexes (/rnar-Ir(PR3)2(CO)X) predictions from ab initio calculations and experimental verification. Abu-Hasanayn, F. Krogh-Jespersen, K. Goldman, A. S. Inorg. Chem. 1993,... 

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