Unsolvated dimeric organometallic samarium hydride versus solvated trisalkylborane supported monomeric hydride

The dimeric hydride [Cp-2'SmCl](2) and the monomeric trisalkylborohydride Cp-2'SmHBEt3(THF)(n) (Cp' = C(5)H(4)tBu) are obtained from the starting dimeric chloride [Cp-2'SmCl](2) by reaction with a hydridic reagent: NaHBEt3. By hydrogenolysis of Cp-2'SmR (R = CH2SiMe3 or CH(SiMe3)(2)) in the presence of an ancillary ligand as PMe3, a monomeric hydride: Cp-2'SmH(PMe3)(2) is formed. The trisalkylborohydride is fairly stable in solution when other new hydrides are only moderately stable: upon standing at room temperature, an irreversible transformation into Cp-3'Sm is observed. All hydrides react with propanone to give the corresponding alkoxide: [Cp-2'SmOCHMe2](2). The new alkyl complex [Cp-2'SmMe](2) is isolated and characterized by NMR and elemental analysis. After hydrogenolysis of this dimer or by reaction of one equivalent of NaHBEt3 with the dimer [Cp-2'SmCl](2), mixed bridged hydrides of the general formula Cp-2'Sm(mu-H)(mu-X) SmCp2' (X = Me or Cl) are formed. A mixed bridged chloroalkoxy complex Cp-2'Sm(mu-OCHR2)(mu-Cl)SmCp2' is also obtained. (C) 1997 Elsevier Science S.A.