Extreme N⋮N Bond Elongation and Facile N-Atom Functionalization Reactions within Two Structurally Versatile New Families of Group 4 Bimetallic “Side-on-Bridged” Dinitrogen Complexes for Zirconium and Hafnium

Abstract

Chemical reduction of (η 5 -C 5 Me 4 R)M[N(R‘)C(X)N(R‘)]Cl 2 (M = Zr or Hf, X = NMe 2 or Me, R = H or Me, R‘ = i -Pr, Et) with 3 equiv of potassium graphite (KC 8 ) in tetrahydrofuran (THF) provides modest isolated yields of the corresponding “side-on-bridged” dinitrogen complexes, {(η 5 -C 5 Me 4 R)M[N(R‘)C(X)N(R‘)]} 2 (μ-η 2:η 2 -N 2 ) ( 1 − 6 ). Single-crystal X-ray analyses of these compounds provide d (N−N) bond length values of 1.518(2), 1.581(4), 1.600(6), 1.611(4), 1.630(4), and 1.635(5) Å for 1 − 6, respectively, that correlate with an increasing fold angle of the M 2 N 2 core for an increase in d (N−N). Compounds 1 − 6 all undergo hydrosilylation and hydrogenation with PhSiH 3 and H 2 to provide the corresponding N-functionalized products, 7 and 8, resulting from single addition of these reagents at 25 °C. Compounds 5 and 6 reacted with ethylbromide at 25 °C to provide the N-alkylated products 9a and 9b, respectively, while reaction of 5 with 1 equiv of Br 2 provided a near quantitative yield of the diazene dibromide 10 which was obtained as a minor co-product in the N-alkylation of 5 .