Osmium complexes amido

These species, in which the l,2-ethanediaminato-(l —) and -(2—) ligands, (HN(CH2)2NH2) and (HN(CH2)2NH)2", are denoted by (en — H) and (en — 2H) respectively are relatively common for the higher oxidation states of osmium indeed the normal preparation of the simple [Os(en)3]3+ cation is by reduction of [Os(en — H)2en]2+, They are in effect 7i-donating amido ligands and so it is perhaps not surprising that osmium(IV) and osmium(VI) complexes should be formed with them. Precise characterization of some of them is lacking, however, particularly those of osmium(III), but there is a recent X-ray crystal structure of [Oslv(en — H)2en]Br2.76... 

Remarkably, both alkyl and aryl C-H activations have been described in the formation of the metallacyclic osmium(iv)-hydride complex 25, generated as the minor component (12%) of a mixture with the deprotonated methylene-amido complex [Os(=N=CH2)Gp(GH2SiMe3)2], from the reaction of the imido complex [Os(=NMe)Cp(CH2SiMe3)2][OTf] with PPhs. ... 

These bis(amido)ruthenium(IV) and bis(amido)osmium(IV) porphyrin complexes show well-resolved H NMR spectra with the signals of the porphyrinato ligands appearing at normal fields, indicating that they are all diamagnetic. 

Os(v), Re(v) Tp, Tp Rhenium/osmium oxo, amido, nitride complexes 1999JOM(591)96... 

The synthetic procedure is very critical. In our case, we believe that the imido-lithium compound (Li2NR) is present in the solution of butyl lithium and para-toluidine, in diethyl ether, as reported for the dilithiated a-naphtylamine. This is a noticeable difference in comparison to typical preparations of ruthenium, osmium, and iridium imido complexes, " in which a dichlorometal complex and the monolithium salt (LiNHR) in a molar ratio 1 2, appropriate for a ftA-amido precursor, are used. In these cases a subsequent removal of amine, or a dehydro-halogenation step with LiNHR, is required to afford the products and free amine. Equation (1) summarizes our synthetic procedure ... 

Osmium complexes, 519-619 alkaloids, 569 alkoxo, 596 amido, 557 amines, 557 bidentate, 530 monodentate. 530 amino acids, 602... 

Following the isolation of these complexes, all of the mechanistic studies on the carbonylation and reduction reactions of nitroarenes catalysed by Ru3(CO)i2, even in the presence of several promoters, have focused on the reactivity of these or related clusters [157-164]. Moreover, many studies have been also conducted on analogous osmium [165-172] and iron (see paragraph 6.6.) clusters, including insertion reactions of isocyanates, which yield potential intermediates in the carbonylation reaction (Insertion reaction of other cumulenes into the Ru-N bond will not be discussed here. However, see the paragraph of the synthesis of heterocycles later in this chapter). Although not all of the previously mentioned studies were intended to be a basis for a mechanistic understanding of the reactions here discussed, they still contain a lot of information on the possible transformations of amido or imido moieties on a trinuclear cluster. 

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