Synthesis and Characterization of Tungsten Alkylidene and Alkylidyne Complexes Featuring a New Carbazole-Based Rigid Trianionic ONO^3– Pincer-Type Ligand

The design and synthesis of a rigid carbazole trianionic pincer ligand and its tungsten alkylidene [CBZ-ONO]­WCHtBu­(OtBu) (3) and anionic alkylidyne {Ph3PCH3}­{[CBZ-ONO]­WCtBu­(OtBu)} (4) complexes are reported. Designed to maximize the inorganic enamine effect by constraining the N atom lone pair, the carbazole ligand achieves high planarity. However, the orbital overlap remains similar to that of the flexible ligand [CF3–ONO]­H3 (1). The neutral alkylidyne complex could not be synthesized. The complexes were characterized by multinuclear NMR spectroscopy, combustion analysis, mass spectrometry, and single-crystal X-ray diffraction. DFT calculations reveal an inorganic enamine orbital overlap within the alkylidyne complexes bearing both the rigid and flexible ligands.