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 = i Pr and Me, and their syntheses are reported. Lutetium dialkyl complexes of the ligand (CzPzR)­Lu­(CH2­SiMe3)2, R = i Pr 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 (CzPz iPr)­Lu­(CH2­SiMe3)2 revealed that the complex is monomeric with a trigonal-bipyramidal geometry. Hydrogenolysis of (CzPz iPr)­Lu­(CH2­SiMe3)2 afforded a trimetallic lutetium hydride complex that possesses five bridging hydride ligands. Notably, intramolecular C–H bond activation of the CzPz iPr ligand was found to occur during the formation of this latter hydride complex, with metalation of a pyrazole carbon atom.