Amido complexes formation

The proposed reaction mechanism was similar to that of the general carboamination reaction that involves oxidative addition to Pd(aryl)amido complex formation followed by... 

PhNHC(NPh)2]2Ru(CO)(PPh3) The Ru(n) amido complex (PCP)Ru(CO) (PMesllNHPh) (PCP = CgH3(CH2PBu2)2-2,6) reacts with nitriles under formation... 

Noyori and coworkers reported well-defined ruthenium(II) catalyst systems of the type RuH( 76-arene)(NH2CHPhCHPhNTs) for the asymmetric transfer hydrogenation of ketones and imines [94]. These also act via an outer-sphere hydride transfer mechanism shown in Scheme 3.12. The hydride transfer from ruthenium and proton transfer from the amino group to the C=0 bond of a ketone or C=N bond of an imine produces the alcohol or amine product, respectively. The amido complex that is produced is unreactive to H2 (except at high pressures), but readily reacts with iPrOH or formate to regenerate the hydride catalyst. 

This transformation is in contrast to the corresponding more sterically crowded [Mo N (Bu )Ar 3] which does not exhibit this type of behaviour. Initially it was assumed that the cyclometallated structure would inhibit the type of reactions (e.g. with N2 or N2O) shown by the t-Bu substituted tris-amido complex. Investigation of the chemistry, however, showed that this is not the case and the imine-hydrido product behaves as an effective source of [Mo N(Pr )Ar 3] which, because of its less sterically encumbered nature, exhibits reactivity not observed for its more hindered [Mo N(Bu )Ar 3] counterpart. A simple example is provided by complex formation with benzophenone to give [Mo N(Pr )Ar 3(r 2-OCPh2)], whereas the Bu analogue did not react with this reagent. ... 

There is one example of an inorganic analogue of ketimine formation (equation 96). If requisite, primary amido complexes were available, this could be a useful synthetic method. 

When aqueous solutions of the complexes [Co(NH3)5(N=CR)]3+ (R=Me or Ph) are treated with an excess of NaN3 at pH 5-6 (to prevent base hydrolysis to the amido complex) tetrazole complexes are formed (Scheme 17).32 The formation of 5-methyltetrazoIe from sodium azide and acetonitrile requires a reaction time of 25 h at 150 °C323 compared with only 2 h at ambient temperature for coordinated acetonitrile. The subsequent conversion of the N -bonded complex to an N2-bonded complex has been confirmed as the latter complex has been prepared and its crystal structure determined.324... 

A direct consequence of the enhanced acidity of co-ordinated amines is seen in the reactions with chlorine in aqueous solution of some platinum(iv) complexes. In these reactions the nucleophilic attack of an intermediate amido complex upon chlorine leads to the formation of dichloroamido complexes (Fig. 5-29). 

Another mechanistically interesting example was reported by Ikariya et al. in 2003 (Scheme 10) [12], The authors focused on the basic character of the Ru-amido complex 21. The reaction of dimethyl malonate with 21 afforded a C-bound Ru-enolate, the structure of which was supported by X-ray analysis. It was considered that the N-H moiety plays a role in bringing the enones to the optimum position by hydrogen bonding, as shown in 22 C-C bond formation then occurs at relatively high reaction temperature, affording the desired adduct in 97 % ee. Before this report appeared, a related catalyst system had been examined by Suzuki et al. for the Type I reaction [4f]. 

The protonation and complex formation of a number of poly(amido-amine)s in aqueous solution have been studied by potentiometric, calorimetric, viscosimetric, spectrophotometric, esr, 13C nmr, and quantum chemical techniques. 

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