Bis(pyrazolyl)carbazole as a Versatile Ligand for Supporting Lutetium Alkyl and Hydride Complexes

Two derivatives of a new bis­(pyrazolyl)­carbazole
pincer
ligand H­(Cz­PzR), R = iPr and Me, and their syntheses are reported. Lutetium dialkyl complexes
of the ligand (CzPzR)­Lu­(CH2­SiMe3)2, R = iPr and Me,
have been prepared and found to exhibit high thermal stability in
solution. These organolutetium compounds are Lewis base free, and
the solid-state structure of (CzPziPr)­Lu­(CH2­SiMe3)2 revealed that the complex
is monomeric with a trigonal-bipyramidal geometry. Hydrogenolysis
of (CzPziPr)­Lu­(CH2­SiMe3)2 afforded a trimetallic lutetium
hydride complex that possesses five bridging hydride ligands. Notably,
intramolecular C–H bond activation of the CzPziPr ligand was found to occur during the formation
of this latter hydride complex, with metalation of a pyrazole carbon
atom.