Triamidotriazacyclononane Complexes of Group 3 Metals. Synthesis and Crystal Structures

Abstract

Reaction of yttrium and lanthanide trichlorides (Ln = La, Eu, Yb) with 1 equiv of the trisodium salt of 1,4,7-tris(dimethylsilylaniline)-1,4,7-triazacyclononane (Na(3)[(SiMe(2)NPh)(3)-tacn](THF)(2)) gives good yields of the compounds [M[(SiMe(2)NPh)(3)-tacn]] (M = Y (1), Eu (3), Yb (4)) and [La[(SiMe(2)NPh)(3)-tacn](THF)] (2). Reduction of 3 with Na/Hg followed by recrystallization in the presence of diglyme yielded crystals of [Eu[(SiMe(2)NPh)(3)-tacn]][Na(diglyme)(2)] (5). Synthesis of the uranium(III) complex [U[(SiMe(2)NPh)(3)-tacn]] (6) is achieved by reaction of 1 equiv of Na(3)[(SiMe(2)NPh)(3)-tacn](THF)(2) with uranium triiodide. The U(IV) complexes, [U[(SiMe(2)NPh)(3)-tacn]X] (X = Cl (7); I (8)), were prepared via oxidation of 6 with benzyl chloride or I(2), but salt metathesis from UCl(4) provided a higher yield route for 7. The solid-state structures of 1-7 were determined by single-crystal X-ray diffraction. The ligand [(SiMe(2)NPh)(3)-tacn] generates a trigonal prismatic coordination environment for the metal center in the neutral complexes 1, 3, 4, and 6 and the ionic 5. In 2 the six nitrogen atoms of the ligand are in a trigonal prismatic configuration with the oxygen atom of the THF capping one of the triangular faces of the trigonal prism. In 7 the coordination geometry around the uranium atom is best described as bicapped trigonal bipyramidal.

A Mononuclear Uranium(IV) Single‐Molecule Magnet with an Azobenzene Radical Ligand

“…This coordination geometry is quite different from that of the precursor compound 1,w hich hasa na lmost perfect trigonal-prismatic coordination geometry (Figure 1c and d). [48] Relevantb ondl engths and angles and as ummary of the crystal data and refinement parameters are given in Ta ble 1 and Ta ble S1 (Supporting Information), respectively.T he two independentm olecules, Ia nd II, in the asymmetric unit feature similar metricp arameters and form an enantiomeric pair (Figure S2 in the Supporting Information). The bond lengths observed are consistent with the presence of aU IV centre coordi-nated to am onoanionic azobenzene ligand, and furtherc onfirm the evidencep rovided by the proton NMR spectrum.…”

“…Hydrogen atoms, the second independent molecule for 2 and solvent molecule for 1 were omitted for clarity.Bond lengths [] for 1:U ÀN amido 2.326(19)-2.367(15) ; UÀN amine 2.640(18)-2.677 (19) . [48] (9) N7A-U2-N8A 32.96(9) (N7/N8)-U1-N3 [a] 173.13(9)( N7A/N8A)-U2-N3A [a] 172.41 (8) [a] The midpoint between the atoms N7/N8 and N7A/N8A was considered.…”

“…This compound is obtained from aone-electron reduction of azobenzene by the previously described trivalent uranium compound [U III {(SiMe 2 NPh) 3 -tacn}] (1). [48] The magnetic properties of 1 were also studied. In the light of the results reported so far,c omplex 1 is the first example of aU III compound that does not exhibit slow relaxation of the magnetization.…”

Titanium Triamidotriamine Compounds: Syntheses, Structures and Redox Properties

“…[4][5][6][7][8] In this context we have reported the synthesis of a new sixdonor triamidotriamine ligand precursor derived from tacn by introducing three Si(Me) 2 N(H)Ph pendant arms on the nitrogen atoms, and the preparation and characterisation of several triamide-tacn metal derivatives. [9,10] The ligand is hexacoordinate in all these complexes, irrespective of the size or oxidation state of the metals used (Ti, lanthanides, U). With the aim of modifying the donor properties of the original set and reduce the ligands' hapticity, with concomitant release of coordination positions at the metal centres, we introduced ortho-fluorine substituents in the phenyl rings and increased the macrocyclic framework and re-[Ti{N 3 [11]N 3 }]I.…”

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

“…Moreover, suitable synthetic methods for selective functionalisation of cyclic polyamines still represent a challenge [18,19] and therefore, the study of metal derivatives of such compounds is still facing its early years. Following our interest in the reactivity of Group 4 metal centres supported by saturated azamacrocycle ligands [20][21][22][23][24], we turned our attention to cross-bridged and trans-disubstituted cyclam ligand precursors. Herein, we present our initial results concerning coordination of zirconium and hafnium to trans-N,N 0 -dibenzyl cyclam and C 2 -cross-bridged cyclam.…”