Reactivity metallic complexes

Mo(r75-C5H5)2H2] and [MoH dppe ]. Our studies of the di- and trihydride complexes of ruthenium and iridium, described above and published previously (27,35), and those of other workers (discussed at the beginning of this chapter), indicate that photoinduced elimination of molecular hydrogen is a common reaction pathway for di- and polyhydride complexes. To demonstrate the photoreaction s generality and its utility for generating otherwise unattainable, extremely reactive metal complexes, we have begun to study the photochemistry of polyhydride complexes of the early transition metals. We focused initially... 

The mechanism of a homogeneously catalyzed reaction, again in the sense of that part of the chemistry occurring in solution which converts substrate to product, involves a series of highly reactive metal complexes any one of which has as much right as any other to be called the catalyst, and it is therefore more correct to speak of a catalytic cycle or catalyst system than of a catalyst. Since the term catalyst will doubtless remain in use for homogeneous systems, the above should be borne in mind when dealing with the literature. 

Reactions of mononuclear vinylidene complexes with other reactive metal complexes to give binuclear //-vinylidene complexes have been described above. Addition of Fe2(CO)c, to Mn(C=CHPh)(CO)2(i/-C5H5) also gives 31, by addition of a CO group to the a-carbon structural data are consistent with the delocalized formulation (31b), with its obvious resemblances to trimethylenemethane (60) ... 

In the most obvious way, a metal complex can be added to the N terminus of the final peptide on the resin (bottom path in Fig. 3). This requires very similar chemistry as discussed above for solution metallation. The metal complex is treated more or less as another amino acid. HBTU and TBTU are the preferred coupling reagents in this case, also HATU might have advantages in difficult cases. We find that for less reactive metal complexes, e.g., cobaltocenium carboxylic acid, longer activation and coupling times of up to 24 h may be needed. 

Chomitz, W.A. and Arnold, J. (2009) Use of tetradentate monoanionic Ugands for stabiUzing reactive metal complexes. Chemistry-A European Journal, 15, 2020. 

Hydrosilylation of isoprene (57) has been well studied and the results are summarized in Table 2. Since 1,3-dienes are relatively reactive, metal complexes which do not catalyze hydrosilylation of common alkenes may be employed. Pd, Rh, Ni and Cr catalysts prefer 1,4-addition products with the (Z)-configuration. No catalyst is available which prefers 1,2-addition with high selectivity. 

G. Denti, S. Campagna, L. Sabatino, S. Serroni, M. Ciano, V. Balzani, Towards an Artificial Photosynthesis. Di-, Tri-, Tetra-, and Hepta-Nuclear Luminescent and Redox-Reactive Metal Complexes, in Photochemistry, Conversion and Storage of Solar Energy, E. Pelizzetti, M. Schiavello, Eds., pp. 27-45, Kluwer Academic Publishers, Dordrecht, The Netherlands, 1991. 

Phosphoranes have attracted attention as ligands for reactive metal complexes.Riess and coworkers have focused on the distinctive coordination chemistry of the bicyclophosphorane Ph(H)P(OCH2CH2)2N(phoran) which can, in principle, exist in different tautomeric forms (Figure 7.8). The novelty associated with this ligand system concerns its ability to... 

Our group has explored in detail the reactivity of 82 and the dicyclohexylphos-phino analog 84 (Scheme 6.19). These Pt chloride complexes were utiHzed as precursors for the synthesis of Pt alkyl complexes and cations of the type [(PSiP)Pt]", with the goal of accessing highly reactive metal complexes that would engage in E-H bond activation chemistry [77]. Indeed, square planar Pt alkyl and aryl complexes of the type (R -PSiP)PtR (85, R = Ph, R = CH2Ph 86,... 

Gschwend B, Pugin B, Bertogg A, Pfaltz A (2009) P-Chiral ferrocenephospholanes synthesis, reactivity, metal complex chemistry and application in the asymmetric hydrogenation of olefins. ChemEur J 15 12993-13007... 

Example 7 The use of highly reactive metal complexes as electrocatalysts... 

Highly reactive metal complexes serve as electrocatalysts for a number of detoxification reactions. An example is the use of Co(II) N, N -bis(salicylidene)ethylene (CoSalen) to facilitate the electrochemical reductive elimination of chlorine from hexachlorobenzene (HCB) [15]. Even though more environmentally friendly conditions have yet to be developed to scale up this process, the CV voltammogram in Fig. 6 shows separate dehalogenation electrochemical steps from the sequence below. 

Osborn s group has continued its studies on whether alkyl halides add oxidatively to iridium(I) compounds by a radical chain or an S 2 mechanism by using more reactive metal complexes such as [Ir(PMe3)2(CO)Cl]. For simple alkyl (methyl excepted), vinyl, and aryl halides and a-halo-esters, evidence based on the effect of radical initiators and inhibitors, structure-reactivity relationships, the trapping of radicals by acrylonitrile, and the loss of stereospecificity at the reacting carbon atom all indicate a radical chain process, perhaps as in equations (14) and (15) ... 

For metal precursors that do not have a suitably basic ligand, it was often possible to carry out a salt metathesis with a reagent such as sodium ethoxide to form a reactive metal complex in situ, which then deprotonated the azolium salt. For example, Herrmann showed that [M(p,-OEt)(COD)]2 (M = Rh, Ir) complexes could be formed in situ by the reaction of [M(p-Cl)(COD)]2 with sodium ethoxide the former complex deprotonated (two equivalents of) an azolium salt NHC-HX to form two molecules of [(NHC)MX(COD)] (12 or 13) (Scheme 2.3). ... 

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