Borohydride complexes of rare earths, and their applications in various organic transformations

Syntheses of lanthanide monochloride and monoborohydride complexes supported by bridged bis(guanidinate) ligand and the use of borohydride complexes in polymerization of cyclic esters

“…The active sequence of Y < Yb << Nd observed is often found in various lanthanide initiators systems. The much higher activity of Nd than (1) 1.329 (7) 1.313 (1) 1.325 (7) 1.314(9) N(2)eC (1) 1.314 (8) 1.327 (1) 1.330 (7) 1 (2) 171.4 (2) 176.1 (7) 176.3(0) 67.1(5) N(1)eC(1)eN (2) 114.1 (5) 114.3 (7) 114.0(5) 113.6 (6) those of Yb and Y may be attributed to the more open coordination sphere around the larger Nd metal, which makes the coordination and then insertion of L-LA and/or 3-CL more facilitate. Such a high activity shown by 6 has not been found in the ROP of 3-CL with borohydride lanthanide complexes reported previously.…”

“…As guanidinate and amidinate groups possess similar coordination and chemical properties, we focused on the synthesis of a new bulky bis(guanidinate) ligand framework with a (CH 2 ) 3 bridge and the related chloro and borohydride complexes of lanthanide metals supported by this new ligand and their evaluation in ROP of cyclic esters with an aim of addressing the potential of these ligands in organolanthanide chemistry. Herein we report the synthesis and structural characterization of lanthanide monoborohydride complexes bearing the bridged bis(guanidinates) ligand L (L ¼ iPr(Me 3 Si) NC(NiPr)N(CH 2 ) 3 NC(NiPr)N(SiMe 3 )iPr), LLnBH 4 (DME) (Ln ¼ Nd (6), Yb (7), Y (8)), and the studies of their catalytic performance of 6e8 in ROP of 3eCL, L-LA and rac-LA are reported in this contribution. The synthesis and molecular structures of the chloro complexes LLnCl(THF) 2 (Ln ¼ Nd (2), Yb (3), Y (4)) and LYbCl(DME) (5) are also included.…”

Hydrogen Sorption in Erbium Borohydride Composite Mixtures with LiBH4 and/or LiH

“…The established technique to synthesize RE borohydrides is the solid state metathesis approach, as it has the advantage of direct synthesis of a RE borohydride without complicated in vacuo manipulations or possible decomposition [28,29]. The RE chloride and an alkali metal borohydride (i.e., Li, Na, K) are mixed in a one-step mechanochemical synthesis to form the RE borohydride and the alkali metal chloride via a metathesis reaction.…”

Catalytic Behavior of Rare-Earth Borohydride Complexes in Polymerization of Polar Monomers

“…Following the developments in organometallic synthesis of rare-earth complexes, original neutral or cationic initiators, either monoor bicomponent catalytic systems, showed novel activity and regio-and/or stereo-selectivity in (co)polymerization; these include half-metallocene complexes bearing mixed Cp*-monodentate anionic ligands or cyclopentadienyl (Cp)-amido and -phosphido linked ligands, as well as Cp-free complexes such as [(COT)RCl] (COT ¼ cyclooctatetraenyl). Tetrahydroborate -namely tetrahydridoborato, commonly referred to as borohydride -complexes of transition metals, including of f-elements, have not been that extensively studied as reflected by the limited number of reviews dedicated to this topic (Makhaev, 2000;Marks and Kolb, 1977;Visseaux and Bonnet, 2011;Xhu and Lin, 1996) or addressing it within a more general context of the related hydride complexes Edelmann, 2009;Ephritikhine, 1997). Indeed, although highly efficient in polymerization, hydride complexes of the rare-earth metals are, in comparison to other species, more sensitive and require good expertise for their isolation and subsequent handling (Ephritikhine, 1997;Konkol and Okuda, 2008;Schumann et al, 1995).…”