Synthesis and crystal structures of the samarium complexes [SmI2(DME)(3)] and [Sm2I(NPPh3)(5)(DME)]

When treated with ultrasound, the reaction of samarium metal with N-iodine- triphenylphosphaneimine in 1,2-dimethoxyethane (DME) leads to the two samar ium complexes [SmI2(DME)(3)] (1) and [Sm2I(NPPh3)(5)(DME)] (2), which are s eparated from each other by fractional crystallization. 1 could be isolated in two different crystallographic forms, namely as brownish black crystals (1a) and as violet-black crystals (1b), both of them are characterized by crystal structure analyses. 1a: Space group P2(1)/c, Z = 4, lattice dimensions at -80 degrees C: a = 14 59.4(1), b = 1314.4(1), c = 2293.6(2) pm, beta = 99.245(8)degrees R = 0.034 4. The structure of 1a holds two crystallographically independent molecules [SmI2(DME)(3)], in which the samarium atoms have coordination number eight . The two individuals differ from each other particularly in their I-Sm-I b ond angles, which are 157.94 and 178.45 degrees. 1b: Space group P2(1), Z = 2, lattice dimensions at -80 degrees C: a = 849.4(3), b = 1060.1(3), c = 1 235.1(6) pm, beta = 93.86(5)degrees, R = 0.0251. 1b has a molecular structu re similar to that of 1a with a bond angle I-Sm-I of 158.40 degrees. The phosphoraneiminato complex [Sm2I(NPPh3)(5)(DME)] (2) forms colourless, moisture sensitive crystals which contain two molecules DME per formula uni t. 2 2 DME: Space group <P(1)over bar >, Z = 2, lattice dimensions at -80 d egrees C: a = 1405.0(4), b = 1656.5(3), c = 2208.3(7) pm, alpha = 89.60(3)d egrees: beta = 72.96(4)degrees, gamma = 78.70(3)degrees, R = 0.0408. In 2 t he two samarium atoms are linked via the mu-N atoms of two phosphoraneimina to ligands to form a planar Sm2N2 four-membered ring. One of the Sm atoms i s terminally coordinated by the N atoms of two (NPPh3)(-) groups, thus achi eving a distorted tetrahedral surrounding. The second Sm atom is coordinate d by the N atom of one (NPPh3)- group, by the terminally bonded iodine atom , and by the O atoms of the DME chelate, thus achieving a distorted octahed ral surrounding.