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

In the domain of N-2 activation, hetero-bimetallic dinitrogen complexes are garnering substantial interest due to their potential to induce polarization in nonpolar N-2 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)N-2](2)Ti-Tipp[O, P, O] 7. These complexes were synthesized via a transmetalation process involving the treatment of [Cr-0-N-2](-) 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 N-2 ligands concurrently coordinated to two chromium and one titanium atoms. Raman spectroscopic data show that the N-N stretching vibration of the N-2 moiety is clearly downshifted relative to free N-2 and to mononuclear [Cr-0-N-2](-) complex 4.