Binuclear complexes, metathesis with

Another interesting castor oil-derived platform chemical is 10-undecenal, which is at the same time a challenging substrate for olefin metathesis. For the SM of 10-undecenal, Dixneuf et al. modified C3 and C5 by insertion of SnCl2 into one Ru-Cl bond [48]. Modification of C3 led to a binuclear complex, which showed a conversion of 70% at a catalyst loading of 0.33 mol%. On the other hand, both the modified and unmodified C5 gave conversions over 70% with catalyst loadings of 1.25 mol%, but also led to formation of a high amount of by-products. 

Bernhard and coworkers [58] have addressed the discovery of ionic iridium(III) and ruthenium(II) complexes by combinatorial luminophore synthesis and screening (Scheme 5.9). Starting from iridium trichloride, cyclometalation with (hetero)arylpyridyl ligands 45 (Fig. 5.17) gives rise to the formation of binuclear iridium complexes 46. Upon complexation with bidentate N,N- or P,P-ligands 47 (Fig. 5.17), the cationic complex 48 is formed, which upon anion metathesis with hexafluorophosphate is transformed into the target complex 49. In this sequence, the step from 46 to 48 was performed in a traditional and a parallel manner, the latter leading to a library of 100 iridium and 10 ruthenium complexes. 

Some examples of single-step metathesis reactions of acetylenes have already been mentioned. This type of reaction can also occur with binuclear complexes eqns. (10-12) (Schrock 1982 Chisholm 1984a,b, 1989 Strutz 1984 Listemann 1985 Latham 1986 Koutsantonis 1991). Reaction (10) proceeds via a fi-C2H2 complex. Reaction (12), in the absence of quinuclidine (quin), gives only [Mo]=CPh. 

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