Synthesis, Reactivity, and Stability of Di- and Trivalent Samarium Amides

SmCl3(THF)3 (THF = tetrahydrofuran) reacts with anionic dialkylamides R2N- [R = Cy (cyclohexyl), i-Pr (isopropyl), Ph (phenyl)] to give different products, depending on the nature of the R substituents. Reaction with Cy2NLi in a 1:2 molar ratio formed [(Cy2N)2Sm(μ-Cl)(THF)]2 (1) in 80% yield, whereas reaction with (i-Pr)2NLi under similar conditions gave [(i-Pr2N)2SmCl3(Li(TMEDA))2] (2). Partial loss of THF from complex 1 reorganized the molecule into the tetranuclear (Cy2N)6Sm4Cl6(THF)2 (3). Attempts to reduce complex 1 with a number of reagents gave [(Cy2N)3SmTHF]·toluene (5), while [(Cy2N)4SmLi(THF)] (4) was isolated upon alkylation reactions carried out with either NpLi or NfLi [Np = CH2C(CH3)3; Nf = CH2C(CH3)2Ph]. Direct synthesis of Sm(II) amides from SmI2(THF)2 starting material was successful only in the case of diphenylamide anion (Ph2N-). Depending on the stoichiometry, -ate (Ph2N)4Sm[Na(TMEDA)]2 (6) or neutral [(Ph2N)2Sm(THF)4]·THF (7) was obtained. The crystal structures of 17 were demonstrated by X-ray diffraction analysis. Crystal data are as follows. 1:  C56H105N4O2Sm2Cl2, triclinic, P1̄, a = 14.344(1) Å, b = 23.897(2) Å, c = 10.2031(9) Å, α = 88.479(9)°, β = 121.83(1)°, γ = 93.73(1)°, Z = 2. 2:  C24H60N6SmCl3Li2 triclinic, P1̄, a = 11.552(1) Å, b = 15.483(1) Å, c = 11.330(1) Å, α = 101.69(1)°, β = 106.13(1)°, γ = 88.89(2)°. 3:  C80H148N6Cl6O2Sm4, triclinic, P1̄, a = 16.508(1) Å, b = 16.7795(9) Å, c = 16.4030(8) Å, α = 89.794(1)°, β = 88.688(2)°, γ = 79.531(1)°, Z = 2. 4:  C56H106N4O2LiSm, orthorhombic, Pna21, a = 16.6145(9) Å, b = 17.5858(9) Å, c = 19.7754(9) Å, V = 5778.0(9) Å3, Z = 4. 5:  C47H82N3OSm, monoclinic, P21/c, a = 10.250(2) Å, b = 23.305(2) Å, c = 19.088(1) Å, β = 100.90(1)°, Z = 4. 6:  C60H72N8SmNa2, tetragonal, I41/acd, a = 18.0004(9) Å, c = 34.106(1) Å, Z = 8. 7:  C44H60N2O5Sm, monoclinic, C2, a = 19.066(1) Å, b = 11.932(1) Å, c = 9.200(1) Å, β = 93.89(1)°, Z = 2.