Trispyrazolyl borate

In addition to these, amide complexes 68, 71, and 72 bearing bulkier trispyrazolyl borate (Tp) were allowed to react with 200 equiv. of rac-lactide in THF, and a similar reaction ran using the chiral 9-BBN-Bp(+)-Cam-supported complex 75. In all cases, polymerization was rapid (90% conversion within 5 min), with complex 68 displaying an extremely rapid >90% conversion of lactide in less than 1 min with a PDI of 1.74 and = 37.8 kg moP of the PLA. The complex (Tp Bu)Ca(OC6H3-2,6- Pr2)(THF) 70 was very active in the polymerization of rac-lactide in THF, with stereoselectivity and rate of polymerization similar to those observed for the amide complex 68. 

Base for C-H or N-H Deprotonation of Precursors to Carbene or Amide Ligands in the Preparation of Metal Complexes. KHMDS has been used as a base for the deprotonation of N-H or B-H bonds in imine-based ligands or trispyrazolyl borate-derived ligands to synthesize calcium complexes, which were used as initiators of the ring-opening polymerization of lactides. A first example of a two-coordinate, neutral In singlet carbene complex has been prepared via an in situ deprotonation of the imine ligand precursor with KHMDS in the presence of In I to afford the In(I) complex in 36% unoptimized yield as pale yellow, thermally stable crystals. ... 

The synthesis described below for the Tm ligand is based on Trofimenko s literature reports of trispyrazolyl borate and the trismethimazole borate synthesis of Lobbia et al., with modifications in temperature and solvent washes. Hydrogen evolution is monitored at a lower temperature, starting around 100°C. In this way we obtain very pure Tm in better yields. 

Tp = hydro(trispyrazolyl)borate). Reaction of TpRu(PPh3)(CH3CN)H with water to form acetamido complex TpRu(PPh3)(H20)(NHC(0)CH3). Organometallics 26 1924... 

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