The reactivity of Samarium(II) in a Bis(indenyl) coordination environment

Abstract

AbstractThe reactivity of the organosamarium(II) indenyl complex (C9H7)2Sm(THF)x, 1, has been compared with that of (C5Me5)2Sm(THF)2, 2, and (C5Me5)2Sm, 3, by examination of characteristic organosamarium(II) reactions which form trivalent oxide, iodide, cyclo‐octatetraenyl and azobenzene complexes. Complex 1 reacts with excess N2O to form [(C9H7)2Sm(THF)]2(μ‐O), 4, and (C9H7)3Sm(THF), 5, as the major products. Two equivalents of 1 react with one equivalent of 1,2‐di‐iodoethane in THF to give (C9H7)SmI2(THF)2, 6, as well as 5. Complex 1 reacts with 1,3,5,7‐cyclo‐octatetraene in a 2:1 ratio in THF to form 5 and (C9H7)Sm(C8H8)(THF)x, 7, which has been fully characterized as the 2,2′‐bipyridine adduct (C9H7)Sm(C8H8)(C10H8N2), 7a. The reaction of 1 with azobenzene in a 2:1 ratio forms [(C9H7)Sm(N2Ph2)(THF)]x, 8, and 5. Complexes 4–6 and 7a have been definitively identified by X‐ray crystallography.Complex 4 crystallizes from THF in space group P1― [C; No. 2] with unit cell parameters at 163 K of a = 8.072(2) Å, b = 9.502(2) Å, c = 12.250(3) Å, α = 101.42(2)°, β = 90.71(2)°, γ = 102.50(2)°, V = 897.7(4) Å3 and Z = 1 for Dcalcd = 1.704 Mgm−3. Least‐squares refinement of the model based on 3924 reflections (|F0|)>3.0 σ (|F0|)) converged to a final RF=2.4%. The geometry around each Sm atom is a distorted tetrahedron and the Sm–O–Sm angle is 180°.Complex 5 crystallizes from THF/hexanes at −35°C in space group P63 [C; No. 173] with unit cell parameters at 163 K of a = 11.7370(14) Å, c = 10.1994(12) Å, V = 1216.8(3) Å3 and Z = 2 for Dcalcd = 1.550 Mg m−3. Least‐squares refinement of the model based on 976 reflections (|F0|> 3.0σ (|F0|) converged to a final RF = 2.3%. The three ring centroids and the THF oxygen atom define a distorted tetrahedron around samarium with a (ring centroid)–Sm–(ring centroid) angle of 116.0°.Complex 6 crystallizes from THF/hexanes as the trisolvate (C9H7)SmI2(THF)3, 6a, in space group P21/n [C; No. 14] with unit cell parameters at 163 K of a = 8.3969(12) Å, b = 17.165(5) Å, c = 33.592(7) Å, β = 96.468(15)°, V = 4811(2) Å3 and Z = 8 for Dcalcd = 2.031 Mg m−3. Least‐squares refinement of the model based on 5664 reflections (|F0|> 2.0 σ (|F0|)) converged to a final RF = 3.3%. The six ligands around Sm in 6a describe a distorted octahedron. The iodide ligands are trans to each other with a 153.8(1)° I–Sm–I angle.Adduct 7a crystallizes from hot THF/toluene in space group P1 [C; No. 2] with a unit cell parameters at 163 K of a = 7.886(7) Å, b = 16.72(2) Å, c = 17.48(2) Å, α = 62.96(7)°, β = 85.17(7)°, γ = 85.23(9)°, V = 2042(3) Å3 and Z = 4. The cyclooctateraenyl and indenyl ligands generate a bent metallocene structure for 7a which contains a chelating bipyridyl group in the plane bisecting the two rings.