Tris(dithiolene) complexes of neodymium and cerium: mononuclear species, chains, and honeycomb networks.
Reactions of Ln(BH4)3(THF)3 (Ln = Nd, Ce) and M2dddt (M = Na, K; dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate) in THF or pyridine gave, after addition of 18c6 (18-crown-6), several crystalline compounds which all contain the tris(dithiolene) Ln(dddt)3 unit. Crystals of [Na(18c6)(py)2]2[Na(18c6)(py)][Nd(dddt)3(py)].3py (1.3py) are built up from discrete mononuclear cationic and anionic species whereas crystals of {[Na(18c6)(py)2](0.5)[Na(18c6)(py)(1.5)][Na(1.5)Nd(dddt)3]}(infinity) (2) are composed of discrete [Na(18c6)(py)x]+ cations and polymeric anionic two-dimensional layers in which the Nd(dddt)3 units are linked to three neighbors by sodium atoms to form a honeycomb network. Analysis of the temperature dependence of the molar magnetic susceptibility of 2 shows that chiMT decreases from 1.63 cm3 K mol(-1) at 300 K down to 0.6 cm3 K mol(-1) at 5 K, due to the crystal-field splitting of the (4)I(9/2) free-ion state. Complexes {[Na3(18c6)(1.5)Nd(dddt)3(THF)].3THF}(infinity) (3.3THF) and {[K3(18c6)(1.5)Nd(dddt)3(py)].3py}(infinity) (4.3py) exhibit neutral polymeric layers with the Nd(dddt)3 units linked by M2(18c6) fragments. In the cerium compound {[Na2(18c6)Na(py)2Ce(dddt)3(py)].3py}(infinity) (5.3py), each Ce(dddt)3 unit is linked to two neighbors only by Na2(18c6) moieties, giving infinite zigzag chains.
Roger
Mathieu
M
Service de Chimie Moléculaire, DSM, DRECAM, CNRS URA 331, CEA/Saclay, 91191 Gif-sur-Yvette, France.
Arliguie
Thérèse
T
Thuéry
Pierre
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Fourmigué
Marc
M
Ephritikhine
Michel
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