Synthesis and Reactivity of Cationic Group 4 Tropocoronand Complexes

Abstract

The tropocoronand complexes [M(TC-3,3)(CH2Ph)2] (M = Zr, Hf) react with either oxidants or protic reagents to afford the five-coordinate cations [M(TC-3,3)(CH2Ph)]+, in which the benzyl ligand interacts weakly in an η2 manner with the group 4 metal center. Isocyanides react with the resulting cations to afford ketenimine complexes, whereas benzophenone inserts into the M−C bond to yield [M(TC-3,3){η1-OCPh2(CH2Ph)}]+. These properties reflect the greater electron-releasing character of the tropocoronand ligands compared to cationic zirconium complexes of other tetraaza macrocyclic ligands and to zirconocenes.

Controlled nitrene transfer from a tyrosinase-like arylnitroso–copper complex

“…This proposal is based on the significantly lengthened N-O bond in 1 at 1.457(9) Å compared with 1.244(7)-1.253(7) Å in the organic ArNO dimer, 14 or other uncoordinated arylnitroso molecules (1.131(11)-1.343(47) Å). 9,18,19 The degree of reduction of the ArNO moiety in 1 was further probed by vibrational analysis. 16 In addition, the square-pyramidal geometry of the Cu centers is consistent with a Cu II oxidation state.…”

“…3 Quite remarkably, 1 is one of the few crystallographically characterized complexes exhibiting a m-Z 2 :Z 2bonded C-nitroso/hydroxylamine core. 9,18,19 The degree of reduction of the ArNO moiety in 1 was further probed by vibrational analysis. Thus, IR spectra of solid 1 and its analogue with an Ar 15 NO moiety reveal the presence of several isotope-sensitive bands (Fig.…”

Diamido/diamine cyclam-based zirconium and hafnium complexes: Synthesis and characterization

“…The solution was then filtered and the solvent evaporated to dryness leading to an off-white oil that was further dried to give a white solid in quantitative yield. NMR (C 6 D 6 ): 1 (9). A stirred solution of 1,4,8,11-tetraazabicyclo[6.6.2]hexadecane 6 (0.23 g, 1.02 mmol) in 20 mL of THF, at À40°C, was treated with a 1.6 M solution of LiBu in hexanes (1.4 mL; 2.24 mmol).…”

“…The association of neutral and anionic nitrogen donor moieties has proved to be a versatile path to follow as attested by the variety of reactions promoted by its transition metal derivatives. In this context, new classes of Group 4 metal complexes having as ancillary ligands tetraazamacrocycles derived from porphyrins, tetraazaannulenes and tropocoronands have been recently reported [2][3][4][5][6][7][8][9]. Some of these complexes showed unprecedented reactivity and structures [10][11][12][13][14].…”

Synthesis, Characterization, and Magnetic Properties of Iron Complexes Bearing Polydentate Nitrogen Ligands

“…A more sterically hindered amidinate is required or amidinates that can give additional electronic stabilization to the highly electronically unsaturated central metal atoms are required. In this general scenario, nitrogen‐based ligands have been found to be particularly attractive in early and late transition metal systems …”