| Summary: | Synthesis of new chromium(II) complexes with chelating bis(alkoxide) ligand [OO]<sup>Ph</sup> (H<sub>2</sub>[OO]<sup>Ph</sup> = [1,1′:4′,1′’-terphenyl]-2,2′’-diylbis(diphenylmethanol)) and their subsequent reactivity in the context of catalytic production of carbodiimides from azides and isocyanides are described. Two different Cr(II) complexes are obtained, as a function of the crystallization solvent: mononuclear Cr[OO]<sup>Ph</sup>(THF)<sub>2</sub> (in toluene/THF, THF = tetrahydrofuran) and dinuclear Cr<sub>2</sub>([OO]<sup>Ph</sup>)<sub>2</sub> (in CH<sub>2</sub>Cl<sub>2</sub>/THF). The electronic structure and bonding in Cr[OO]<sup>Ph</sup>(THF)<sub>2</sub> were probed by density functional theory calculations. Isolated Cr<sub>2</sub>([OO]<sup>Ph</sup>)<sub>2</sub> undergoes facile reaction with 4-MeC<sub>6</sub>H<sub>4</sub>N<sub>3</sub>, 4-MeOC<sub>6</sub>H<sub>4</sub>N<sub>3</sub>, or 3,5-Me<sub>2</sub>C<sub>6</sub>H<sub>3</sub>N<sub>3</sub> to yield diamagnetic Cr(VI) bis(imido) complexes; a structure of Cr[OO]<sup>Ph</sup>(N(4-MeC<sub>6</sub>H<sub>4</sub>))<sub>2</sub> was confirmed by X-ray crystallography. The reaction of Cr<sub>2</sub>([OO]<sup>Ph</sup>)<sub>2</sub> with bulkier azides N<sub>3</sub>R (MesN<sub>3</sub>, AdN<sub>3</sub>) forms paramagnetic products, formulated as Cr[OO]<sup>Ph</sup>(NR). The attempted formation of a Cr−alkylidene complex (using N<sub>2</sub>CPh<sub>2</sub>) instead forms chromium(VI) bis(diphenylmethylenehydrazido) complex Cr[OO]<sup>Ph</sup>(NNCPh<sub>2</sub>)<sub>2</sub>. Catalytic formation of carbodiimides was investigated for the azide/isocyanide mixtures containing various aryl azides and isocyanides. The formation of carbodiimides was found to depend on the nature of organoazide: whereas bulky mesitylazide led to the formation of carbodiimides with all isocyanides, no carbodiimide formation was observed for 3,5-dimethylphenylazide or 4-methylphenylazide. Treatment of Cr<sub>2</sub>([OO]<sup>Ph</sup>)<sub>2</sub> or H<sub>2</sub>[OO]<sup>Ph</sup> with NO<sup>+</sup> leads to the formation of [1,2-b]-dihydroindenofluorene, likely obtained via carbocation-mediated cyclization of the ligand.
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