COORDINATIONALLY OVERSATURATED METALLOCENE DERIVATIVES - THE CRYSTAL AND MOLECULAR-STRUCTURE OF [(ETA-5-C5H5)2SM(MU-3-H)]2[(MU-2-H)2ALH.N(C2H5)3]2 AND [(ETA-5-C5H4-TERT-BU)2SM]2-(MU-2-H)MU-[(MU-3-H)2AL(MU-2-H)2.ME2NC2H4NME2] COMPLEXES

The interaction of Cp'2SmCl (Cp' = C5H5, C5H4tBu) with LiAlH4 at the reagent ratio 1:1 yields compounds of composition [(eta-5-C5H5)2Sm(mu-3-H)]2[(mu-2-H)2AlH.N(C2H5)3]2 (I) and [(eta-5-C5H4tBu)2Sm]2(mu-2-H)mu-[(mu-3-H)2Al(mu-2-H)2.Me2NC2H4NMe2] (II) depending on the nature of the solvating Lewis base. Crystals of I are triclinic, a = 11.012(3), b = 11.911(3), c = 14.314(4) angstrom, alpha = 88.76(2), beta = 78.65(2), gamma = 96.17(2)-degrees, space group P1BAR, Z = 4, rho-calc = 1.47 g/cm3. Crystals of II are monoclinic, a = 16.652(5), b = 18.720(5), c = 16.499(5) angstrom, gamma = 91.77(2)-degrees, space group B2b, Z = 8, rho-calc = 1.18 g/cm3. In both complexes samarium atom is coordinated by four hydrides and has a formal 20e configuration. Probable reasons for this coordinational oversaturation are discussed. The novel type of bridging alumohydride group coordination with two mu-3- and two mu-2-hydrogen atoms is described for II.