Mono- versus Bis-chelate Formation in Triazenide and Amidinate Complexes of Magnesium and Zinc

Abstract

Magnesium and zinc complexes of the monoanionic ligands N,N'-bis(2,6-di-isopropylphenyl)triazenide, L1, N,N'-bis(2,6-di-isopropylphenyl)acetamidinate, L2, and N,N'-bis(2,6-di-isopropylphenyl)tert-butylamidinate, L3, have been synthesized, but only L3 possesses sufficient steric bulk to prevent bis-chelation. Hence, the reaction of L1H with excess ZnEt2 leads to the isolation of (L1)2Zn, 1; L1H also reacts with Bu2Mg in Et2O to afford (L1)2Mg(Et2O), 2. Similar reactivity is observed for L2H, leading to the formation of (L2)2Zn, 3, and (L2)2Mg, 4. The reaction of L2H with ZnR2 may also afford the tetranuclear aggregates {(L2)Zn2R2}2O, 5 (R=Me) and 6 (R=Et). By contrast, the tert-butylamidinate ligand was found to exclusively promote mono-chelation, allowing (L3)ZnCl(THF), 7, [(L3)Zn(micro-Cl)]2, 8, (L3)ZnN(SiMe3)2, 9, (L3)MgiPr(Et2O), 10, and (L3)MgiPr(THF), 11, to be isolated. X-ray crystallographic analyses of 1, 2, 3, 4, 5, 6, 8, and 10 indicate that the capacity of L3 to resist bis-chelation is due to greater occupation of the metal coordination sphere by the N-aryl substituents.

Design, synthesis and properties of a trinuclear copper(I) cluster with a triazenide ligand

“…The use of different bridging and well-designed polydentate ligands has afforded an impressive array of nuclear coordination complexes with new architectures. Among them, the triazenide ligands have attracted our attention, as these compounds can serve as a monodentate (a) [1,2], a bidentate chelating (b) [3][4][5][6][7], and a bridging ligands (c) [8-12] (Scheme 1).With this mind, our work focuses on the sign, synthesis and their reactivity with transition metals of new bridging ligands (Scheme 1d) which can delocalize electron density through their B-bonding network and strongly donate π electron density to the metal atoms and control the organization of polynuclear metal complexes [13].We have synthesized a new triazenide ligand, 1-[(2-carboxymethyl)benzene]-3-[benzothiazole]triazene (HL) by modification of a literature procedure [14]. The reaction of HL and CuCl in THF/ methanol gives a trinuclear copper(I) cluster 1.…”

“…The use of different bridging and well-designed polydentate ligands has afforded an impressive array of nuclear coordination complexes with new architectures. Among them, the triazenide ligands have attracted our attention, as these compounds can serve as a monodentate (a) [1,2], a bidentate chelating (b) [3][4][5][6][7], and a bridging ligands (c) [8][9][10][11][12] (Scheme 1).…”

Hetero- and Homoleptic Magnesium Triazenides

“…The different coordination is reflected by the interplanar angle γ, which is defined as the angle between the two MgNN planes (e.g., for 4c, angle between the plane normals through the atoms Mg/N1/N3 and Mg/N4/N6), of 83.6° (4c) and 9.6° (4b), or alternatively, by the τ4 parameter of 0.51 (4c) and 0.20 (4b). These values may be compared with the corresponding parameters in previously-published homoleptic magnesium amidinates [16,[26][27][28][29][30], guanidinates [20] and β-diketiminates [31][32][33], as summarized in Table 1. For the six known magnesium amidinates, considered to possess tetrahedral metal coordination, γ angles and τ4 parameters are observed in the range of 54.1°-89.5° and 0.40°-0.60°, respectively.…”

“…The latter are the first examples of unsolvated magnesium triazenides, whereas the former are potential precursors for magnesium(I) triazenides. A small number of magnesium triazenides, mainly using less bulky substituents, has been reported before [11,[14][15][16]. With relatively 1 H NMR data indicate free (for 4c at 373 K) or almost free (for 4b at 338 K) rotation around the N-C(aryl) bonds since some broadening of the resonances is still observed (cf.…”

Copper complexes of 1-[(2-carboxyethyl)benzene]-3-[2-pyridine]triazene

“…The triazenide anion is a ''small bite'' three-atom donor that can act as a monodentate ligand (a) [2], a bidentate chelating ligand (b) [3], or a bridging ligand (c) [4][5][6] (Scheme 1). Complexes with 1,3-(aryl) triazines have been well studied [7,8].…”