UTILITY OF ORGANOSAMARIUM(II) REAGENTS IN THE FORMATION OF POLYATOMICGROUP-16 ELEMENT ANIONS - SYNTHESIS AND STRUCTURE OF [(C5ME5)2SM]2(E3)(THF), [(C5ME5)2SM(THF)]2(E), AND RELATED SPECIES (E=S, SE, TE)

(C5Me5)2Sm(THF)2 reacts with Te and Se in a 2:1 ratio at room temperat ure in THF to form [(C5Me5)2Sm-((THF)]2(mu-Te), 1, and [(C5Me5)2Sm(THF )]2(mu-Se), 2, respectively. (C5Me5)2Sm(THF)2 reacts with Ph3P=Se and Ph3P=S in a 2:1 ratio at room temperature in THF to form 2 and [(C5Me5 )2Sm(THF)]2(mu-S), 3, respectively. (C5Me5)2Sm(THF)2 reacts with exces s Te and Se at room temperature in THF to form [(C5Me5)2Sm]2(Te3)(THF) , 4, and [(C5Me5)2Sm]2(mu-eta1:eta3-Se3)(THF), 5. The sulfur analog, [ (C5Me5)2Sm]2(Se)(THF), 6, can be prepared from (C5Me5)2Sm(THF)2 and S8 in a 2:3 ratio. Triselenide 5 can also be prepared from monoselenide 2 and 2 equiv of Se and monotelluride 1 reacts with excess Te to form tritelluride 4. Both of these reactions occur in THF but not in toluen e. Selenium reacts with monotelluride 1 to form a mixture containing a mixed chalcogen complex 7, but this product is not generated from com plex 2 by reaction with excess Te. The trichalcogenides 5 and 6 can be converted back to the monochalcogenides 2 and 3, respectively, with 2 equiv of PPh3. 4 reacts with PMe3 in THF to form [(C5Me5)2Sm]2(mu-eta 2:eta2-Te2), 8. X-ray crystallographic studies revealed that 2 and 3 a re isostructural and differ from 1 only in that 1 has benzene in the l attice instead of toluene. In each complex, a bent metallocene moiety is attached to one THF ligand and a bridging E group. The Sm-E distanc es are 2.988(2)/2.987(2) (Te), 2.782(1)/2.779(1) (Se), and 2.663(1)/2. 665(1) angstrom (S) and the Sm-E-Sm angles are 170.2(1) (Te), 169.7(1) (Se), and 170.0(1)(S). The(Se-Se-Se)2- unit in [(C5Me5)2Sm]2(mu-eta1: Se3)(THF), 5, contains Se-Se distances of 2.377(1) angstrom and 2.326( 1) angstrom with an angle of 107.7(1)degrees. The samarium of one of t he bent metallocene units in 5 is attached to THF and a bridging selen ium atom with a Sm-Se(1) distance of 2.963(1) angstrom. The other (C5M e5)2Sm unit is 3.007(1) angstrom from Se(1) and 3.198(1) and 2.917(1) angstrom, respectively, from Se(2) and Se(3), which are sequentially c onnected to Se(1). The plane of three selenium atoms forms an angle of 57.9-degrees with the Sm2Se(1) plane. A mixed Se/Te complex, 7, was i solated from the reaction of 1 with Se. 7 is analogous to and isostruc tural with 5 and contains some Te distributed over at least two of the three chalcogen sites in the molecule. In 8, two bent metallocene uni ts are side on coordinated to a Te2 unit with a 2.773(1) angstrom Te-T e bond such that the four C5Me5 rings define a square plane. 1 crystal lizes from benzene in space group P2(1)/c [C2h5; No. 14] with unit cel l parameters at 173 K of a = 10.832(2) angstrom, b = 15.140(3) angstro m, c = 32.330(7) angstrom, beta = 95.753(16)degrees, and V = 5276(2) a ngstrom3 with Z = 4 for D(calcd) = 1.854 g 1.50 g cm-3. Least-squares refinement of the model based on 4479 observed reflections (\F(o)\ > 3 .0sigma(\F(o)\) converged to a final R(F) = 6.0%. 2 crystallizes from toluene in space group P2(1)/c [C2h5; No. 14] with unit cell parameter s at 168 K of a = 10.8717(13) angstrom, b = 14.971(2) angstrom, c = 32 .856(5) angstrom, 0 = 96.055(11)degrees, and V = 5317.8(12) angstrom3 with Z = 4 for D(calcd) = 1.445 g cm-3. Least-squares refinement of th e model based on 5682 observed reflections (\F(o)\ > 3.0sigma(\F(o)\)) converged to a final R(F) = 4.3%. 3 crystallizes from toluene in spac e group P2(1)/c [C2h5; No. 14] with unit cell parameters at 168 K of a = 10. 874(4) angstrom, b = 14.824(4) angstrom, c = 32.880(11) angstro m, beta = 95.82(3)degrees, and V = 5273(3) angstrom3 with Z = 4 for D( calcd) = 1.398 g cm-3. Least-squares refinement of the model based on 10850 observed reflections (\F(o)\ > 3.0sigma(\F(o)\)) converged to a final R(F) = 4.2%. 5 crystallizes from toluene in space group P2(1)/n [C2h5; No. 14] with unit cell parameters at 168 K of a = 15.316(3) ang strom, b = 16.355(2) angstrom, c = 23.963(3) angstrom, beta = 97.641(1 1)degrees, and V = 5949.0(13) angstrom3 with Z = 4 for D(calcd) = 1.54 2 g cm-3. Least-squares refinement of the model based on 10330 observe d reflections (\F(o)\ > 3.0sigma(\F(o)\)) converged to a final R(F) = 6.9%. 7 crystallizes from toluene in space group P2(1)/n [C2h5; No. 14 ] with unit cell parameters at 158 K of a = 15.297(3) angstrom, b = 16 .386(3) angstrom, c = 24.016(4) angstrom, beta = 97.347(14)degrees, an d V = 5970.6(17) angstrom3 with Z = 4 for D(calcd) = 1.525 g cm-3. Lea st-squares refinement of the model based on 5855 observed reflections (\F(o)\ > 3.0sigma([F(o)\)) converged to a final R(F) = 7.4%. 8 crysta llizes from benzene in space group P2(1)/c [C2h5; No. 14] with unit ce ll parameters at 163 K of a = 13.163(2) angstrom, b = 10.644(2) angstr om, c = 15.376(2) angstrom, beta = 114.19(11)degrees, and V = 1965.1(5 ) angstrom3 with Z = 2 for D(calcd) = 1.854 g cm-3. Least-squares refi nement of the model based on 5268 observed reflections (\F(o)\ > 3.0si gma(\F(o)\)) converged to a final R(F) = 3.8%.