Syntheses and Characterizations of Hetero-Bimetallic Chromium-Dinitrogen Transition-Metal Complexes

Xueli Wang, Yixi Wang, Yue Wu, Gao-Xiang Wang, Junnian Wei*, Zhenfeng Xi

Inorg. Chem., 2023. DOI: 10.1021/acs.inorgchem.3c02944.

        In the domain of N₂ activation, hetero-bimetallic dinitrogen complexes are garnering substantial interest due to their potential to induce polarization in nonpolar N₂ gas. Herein, we present the syntheses and characterizations of three novel hetero-multimetallic dinitrogen complexes: Cp*Cr(depe)N₂V(depe)^Me[O,P,O] 5, Cp*Cr(depe)N₂V(depe)^Tipp[O,P,O] 6, and [Cp*Cr(depe)N₂]₂Ti^Tipp[O,P,O] 7. These complexes were synthesized via a transmetalation process involving the treatment of [Cr⁰–N₂]⁻ complex 4 with vanadium and titanium chloride complexes bearing alkyl or aryl substituted bis(o-hydroxyphenyl)-phenyl phosphine ^R[O,P,O] ligand (alkyl = methyl, aryl = 2,4,6-tri-isopropylbenzene). X-ray analysis shows that complexes 5 and 6 exhibit heterodinuclear structures, while complex 7 exhibits a heterotrinuclear core with two N₂ ligands concurrently coordinated to two chromium and one titanium atoms. Raman spectroscopic data show that the N–N stretching vibration of the N₂ moiety is clearly downshifted relative to free N₂ and to mononuclear [Cr⁰–N₂]⁻ complex 4.