Comparison of divalent dimethoxyethane-solvated thulium and samarium diiodides in hexamethylphosphoramide and pyridine:: Isolation of the cations {[TmI2(HMPA)4][I](pyridine)5} and {[TmI(HMPA)4(pyridine)][I]2} and a single crystal containing both linear and bent dimethoxyethane-solvated SmI2

The highly reducing nature TmI2(DME)(3) is shown by comparison with SmI2 in its reactions in hexamethylphosphoramide (HMPA) and pyridine. Addition of 4 equiv of HMPA to green TmI2(DME)(3) in dimethoxyethane (DME) forms pale yellow solids which dissolve in pyridine and can be isolated as TmI3(HMPA)(4), 1. Recrystallization of 1 from pyridine yields {[TmI2(HMPA)(4)][I](pyridine)s}, 2, or {[TmI(HMPA)(4)(pyridine)][I](2)}, 3, depending upon conditions. Both 2 and 3 crystallize with distorted octahedral geometries around thulium. Addition of HMPA to TmI3 in DME also forms 1. TmI2(DME)(2), formed by the loss of DME from TmI2(DME)(3) under vacuum, reacts with pyridine to form intensely colored materials, which have magnetic moments consistent with the presence of Tm(III). In comparison, SmI2(THF)(2) dissolves in a mixture of pyridine and DME and can be recrystallized as divalent SmI2(DME)(3), 4. 4 crystallizes with both lenear and bent I-Sm-I arrangements in the same crystal. In the former case a hexagonal bipyramidal coordination geometry is present and in the latter a dodecahedral geometry is observed. (C) 1998 Elsevier Science Ltd. All rights reserved.