Tris(pyrazolyl)borate carbosilane dendrimers and metallodendrimers

Abstract

The substituted ligands Me3SiC(pz)3 (1) and Me3SiOCH2C(pz)3 (2) have been prepared starting from HC(pz)3 and HOCH2C(pz)3. The molecular structure of compound 1 has been determined by X-ray diffraction studies, which show a propeller-like conformation of the pyrazolyl rings. Compound 2 has been found to be useful for the synthesis of [Mo(CO)3{Me3SiOCH2C(pz)3}] (3), [TiCl2(NtBu){Me3SiOCH2C(pz)3}] (4), and [PdCl2{Me3SiOCH2C(pz)3}] (5), through ligand exchange reactions. The characterization of the new complexes is compatible with a tridentate coordination of the ligands in complexes 3 and 4, and a bidentate coordination in 5 as confirmed by an X-ray analysis carried out with the palladium complex. The procedure has been extended for the synthesis of the carbosilane G1-[OCH2C(pz)3]4 (6) and the tetrametallic compound G1-[OCH2C(pz)3Mo(CO)3]4 (7) (G1 = Si(CH2CH2CH2Me2Si)4-).