Scorpionate poly pyrazolyl borate Features

Two families of scorpionate ligands (pyrazole-based) may be distinguished  

A progressive increase in the steric hindrance of Tpx ligands influences the depth of the hydrophobic pocket around the metal as shown in Fig. 1.6. 

On the other hand, the tethering of the 3-phenyl group leads to an increase or decrease of the cone angle of the ligand, depending on 

The highly fluorinated Tp(Cp3)2 ligand (Fig. 1.9) essentially serves as a protective Teflon coated container for M(I)-L (L = CO, C2H4) fragments.22,23 

Some Bp and Tp ligands with expanded denticity via potential oxygen donors on the 3-phenyl substituent were able to coordinate through the o-methoxy substituent. These ligands may be particularly useful in lanthanide and actinide coordination chemistry.24 

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The book Scorpionates The Coordination Chemistry of Polypyra-zolylb orate Ligands, organized according to the ligand type and to the coordinated metal, is the reference work for the papers published on poly(pyrazolyl)borates until April 1999.75 A review on this book by Templeton appeared in Journal of American Chemical Society in 2000.76 More recently, Trofimenko described also the most important features of poly(pyrazolyl)borates, from their synthesis and naming to their main applications.77... 

Up to March 2006 the molecular structures of about 40 alkylidyne complexes ligated by poly(pyrazolyl)borates had been reported, and structural data for the crystallographically characterised alkylidyne-metal complexes are compiled in Table II. Of these, Tp- and Tp -ligated complexes represent more than 80%, with one third of the total known structures being bi- and polymetallic complexes. Structural features of alkylidyne complexes in general have been discussed elsewhere and, accordingly, an attempt to restrict this discussion to features which are unique or characteristic of the scorpionate alkylidyne complexes has been made. 

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