Unsolved dimeric organometallic samarium hydride versus solvated trisalkylborane supported monomeric hydride

Abstract The dimeric hydride [Cp′ 2 SmH] 2 and the monomeric trisalkylborohydride Cp′ 2 SmHBEt 3 (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: NaHBEt 3 . By hydrogenolysis of Cp′ 2 SmR (R  CH 2 SiMe 3 or CH(SiMe 3 ) 2 ) in the presence of an ancillary ligand as PMe 3 , a monomeric hydride: Cp′ 2 SmH(PMe 3 ) 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 hydrideds react with propanone to give the corresponding alkoxide: [Cp′ 2 SmOCHMe 2 ] 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 NaHBEt 3 with the dimer [Cp′ 2 SmCl] 2 , mixed bridged hydrides of the general formula Cp′ 2 Sm(μ−H)(μ−X)SmCp′ 2 (X  Me or Cl) are formed. A mixed bridged chloroalkoxy complex Cp′ 2 Sm(μ-OCHR 2 )(μ-Cl)SmCp′ 2 is also obtained.