Pyrazolylborato-complexes

In addition to tin alkyl derivatives with one poly(pyrazolyl)borato ligand, bis[(poIy)pyrazolylborato] complexes of the types [Tp]2SnR2 and [R2Bp]2SnR2 have also been prepared (123,124). 

The possibility of formation of an O—O bond at a single Mn site of the OEC, on the other hand, seems remote, but nevertheless, two mononuclear model Mn-peroxo complexes, a peroxo-Mnm porphinato 64 [157] and a peroxo-Mn111 pyrazolylborato complex 65 [158], have been structurally characterized. Both complexes contain side-on peroxo groups. Complex 65 has been crystallized in two forms, one brown and one blue. A peroxo-H—N (pyrazole) hydrogen bond is found only in the blue form (Figure 29). 

Prior to a consideration of oxo-molybdenum and oxo-tungsten bis(dithiolene) complexes, and as a link to the pyrazolylborato complexes discussed in the latter part of Section II, mention will be made of the dithiolene complexes, [(L-... 

J. Sundermeyer et al., Chem. Ber. 1994,127, 1201 M. Etienne, Coord. Chem. Rev. 1996, 156, 201 (this review has many references to other hydridotris(pyrazolylborato)vanadium complexes in oxidation states II-V). 

A lanthanide superoxide complex, [HB(3,5-Me2pz)3]2Sm(7j2-02), has recently been reported.15 It is simply made by the reaction of the pyrazolylborato compound of Sm11 with 02. 

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