UTILITY OF N-METHYLIMIDAZOLE IN ISOLATING CRYSTALLINE LANTHANIDE IODIDE AND HYDROXIDE COMPLEXES - CRYSTALLOGRAPHIC CHARACTERIZATION OF OCTASOLVATED [SM(N-MEIM)8]I3 AND POLYMETALLIC [SMI(MU-I)(N-MEIM)3]2, [(N-MEIM)5SM(MU-OH)]2I4, AND ([(N-MEIM)4SM(MU-OH)]3(MU-3-OH)2)I4

SmI2(THF)2 reacts in THF with 4 equiv of N-methylimidazole (N-MeIm) at room temperature to form a dark green solution from which divalent SmI2(N-MeIm)4 (1) can be isolated in 95% yield. Crystallization of 1 from THF occurs with loss of 1 equiv of N-MeIm per samarium to form the dimer [SmI(mu-I)(N-MeIm)3]2 (2). 2 forms in space group P2(1)/n (C25h; No. 14) with unit cell parameters at 168 K of a = 12.8310(12) angstrom, b = 9.9430(8) angstrom, c = 16.1339(11) angstrom, beta = 109.735(6)degrees, and V = 1937.4(3) angstrom3 with Z = 2 for D(calcd) = 2.23 g cm-3. Least-squares refinement of the model based on 3887 observed reflections (\F(o)\ > 3.0sigma(\F(o)\) converged to a final R(F) = 4.7%. The two six-coordinate samarium centers in 2 are edge-fused octahedra with the two bridging iodides and the terminal iodide attached to each samarium in a meridional orientation. EuI2(THF)2 reacts similarly to form EuI2(N-MeIm)4(3), which crystallizes from THF as [EuI(mu-I)(N-MeIm)3]2 (4). 4 is isostructural with 2 with unit cell parameters at 173 K of a = 12.810(14) angstrom, b = 9.910(9) angstrom, c = 16.121(15) angstrom, beta = 109.90(8)degrees, and V = 1923.8(33) angstrom3 with Z = 2 for D(calcd) = 2.25 g cm-3. Crystallization of divalent 1 from N-MeIm by diffusion of benzene occurs slowly (7-10 days) and leads to the trivalent complexes [Sm(N-MeIm)8]I3 (5) and {[(N-MeIm)4Sm(mu-OH)]3(mu3-OH)2}I4 (6), which are formed by hydrolysis. 5 can be independently synthesized in 95% yield by isolating the solid from the pale yellow solution formed by dissolving SM13(THF)3 in N-MeIm. 5 crystallizes from N-MeIm/benzene in space group P4 (C-4(1); No. 75) with unit cell parameters at 163 K of a = 10.3743(9) angstrom, c = 12.377(2) angstrom, and V = 1332.0(3) angstrom3 with Z = 1 for D(calcd) = 1.676 g cm-3. Least-squares refinement of the model based on 1537 observed reflections (\F(o)\ > 6.0sigma(\F(o)\)) converged to a final R(F) = 3.1%. In 5, eight N-MeIm ligands describe a square antiprismatic geometry around the Sm(III) cation, which is not within bonding distance of the three iodide counterions. 6 crystallizes from N-MeIm/benzene in space group Pbca (D2h15; No. 61) with unit cell parameters at 163 K of a = 21.217(3) angstrom, b = 27.497(6) angstrom, c = 33.497(5) angstrom, and V = 19.543(6) angstrom3 with Z = 8 for D(calcd) = 1.673 g cm-3. Least-squares refinement of the model based on 7546 observed reflections (\F(o)\ > 4.0sigma(\F(o)\)) converged to a final R(F) = 6.5%. 6 is composed of a triangle of Sm(N-MeIm)4 units bridged by three mu-hydroxide ligands in the plane of the metals and two mu3-hydroxides above and below the plane. The geometry around samarium is best described as a dodecahedron. The four iodide counterions do not interact with the samarium centers. 5 is also very soluble in N-MeIm, and crystallization over long time periods leads to a hydroxide complex [(N-MeIm)5Sm(mu-OH)]2I4 (7). 7 crystallizes from N-MeIm/benzene in space group C2/c (C2h6; No. 15) with unit cell parameters at 163 K of a = 21.673(3) angstrom, b = 12.582(2) angstrom, c = 24.534(4) angstrom, beta = 103.515(12)degrees, and V = 6504(2) angstrom with Z = 4 for D(calcd) = 1.778 g cm-3. Least-squares refinement of the model based on 6022 observed reflections (\F(o)\ > 3.0sigma(\F(o)\)) converged to a final R(F) = 3.8%. 7 is composed of a dimeric tetracation which contains seven-coordinate samarium centers. Two Sm(N-MeIm)5 units are bridged by two mu-hydroxide ligands. As in 5 and 6, the iodide counterions do not interact with the samarium centers.