Structural diversity in the borohydrido lanthanides series: First isolation and X-ray crystal structure of ionic [Sm(BH4)2(THF)5]+[Cp∗′Sm(BH4)3]-[Sm(BH4)2(THF)5]+[Cp∗′Sm(BH4)3]-

The reaction of Sm(BH4)3(THF)3Sm(BH4)3(THF)3 with a half equivalent of KCp∗′KCp∗′(Cp∗′=C5Me4nPr) affords a compound comprising one Cp∗′Cp∗′ ligand and three THF molecules per two Sm atoms, [Cp∗′Sm2(BH4)5(THF)3][Cp∗′Sm2(BH4)5(THF)3], according to analytical data. Crystals of penta-THF adduct 1, showing the same 1H NMR spectrum except for the quantity of THF, could be isolated from a solution of half-samarocene Cp∗′Sm(BH4)2(THF)Cp∗′Sm(BH4)2(THF) (2). X-ray structure determination of 1 revealed an ionic compound [Sm(BH4)2(THF)5]+[Cp∗′Sm(BH4)3]-[Sm(BH4)2(THF)5]+[Cp∗′Sm(BH4)3]- with two discrete mononuclear Sm polyhedrons. The expected neutral samarocene Cp2∗′Sm(BH4)(THF)(3) could be obtained from the reaction of Sm(BH4)3(THF)3Sm(BH4)3(THF)3 with two equivalents of KCp∗′KCp∗′. X-ray structure analysis showed that 3 is a monomeric complex bearing a terminal borohydride ligand. All BH4- ligands in 1 and 3 exhibit an η3-H3BHη3-H3BH bonding mode.

Graphical abstractTwo new borohydrido complexes of samarium were prepared: [Sm(BH4)2(THF)5]+[Cp∗′Sm(BH4)3]-[Sm(BH4)2(THF)5]+[Cp∗′Sm(BH4)3]- (1) and Cp2∗′Sm(BH4)(THF) (3) (Cp∗′=C5Me4nPr). X-ray studies revealed that 1 displays an unprecedented ionic structure comprising a half samarocene moiety, whereas 3 is monomeric and bears a terminal BH4 ligand.Figure optionsDownload full-size imageDownload as PowerPoint slide