A Pair of Remarkably Stable Mononuclear Chromium(III) and Chromium(IV) Hydrides

Abstract

Often regarded as rare and unstable species, mononuclear CrIII and CrIV hydrides (2 and 3, respectively; see scheme) have been prepared by various methods, and their interplay is illustrated by various reactions. The electronic structures of the hydrides were elucidated by utilizing several theoretical methods.

Density functional studies on chromium catalyzed ethylene trimerization

“…The Cr(IV)-H distances in the intermediates N2-N4 and the TSs NTS2-NTS4 are all in the range of 1.524-1.548 Å, which are in accordance with those reported in the literature [70,71]. In the Cr(II)-1-hexene complex N6, the short Cr(II)Á Á ÁH(CH 3 ) distance, 1.977 Å and one long C-H bond of CH 3 , 1.117 Å as against 1.098 Å each for the other two C-H bonds, are indicative of reasonable a-agostic stabilizing interactions.…”

“…The Cr(IV)-H distances in the intermediates C2-C4, and the TSs CTS2-CTS4 are in the range 1.508-1.561 Å and for CTS5 it's the longest, 1.648 Å which are in accordance with those reported in the literature [70,71]. The overall structural features are broadly similar to those discussed for the Cossee path with the neutral model (cf.…”

Systematic Study of Open‐Shell Trigonal Pyramidal Transition‐Metal Complexes with a Rigid‐Ligand Scaffold

“…Additionally, the presence of the [Li(THF)] + cations attached to the [M II (N 3 N)] − core through electrostatic interactions causes significant distortion from the ideal trigonal pyramid towards pseudo‐ C s symmetry . This situation affects the arrangement and lifts the degeneracy of the d orbitals in a manner that is depicted in Figure S2 in the Supporting Information .…”

A modular synthesis of tris(aryl)tren ligands: Synthesis, structure and lithiation chemistry

“…The ligand set binds transition metals in the +3 oxidation state, with tetradentate N4 coordination and favors a C 3 -symmetric environment around the metal center. Though many different variations of the tren ligand have been prepared, the majority of the metalation work performed to date has been on tris(silyl)tren derivatives [2,[4][5][6][7][8][9][10][11]. The tris(aryl)tren ligand set has been explored to a lesser extent [12][13][14][15][16][17][18][19], but has shown great promise in the areas of nitrogen fixation [3] and in metal cluster formation [20].…”