Rationalizing the Reactivity of Mixed Allyl Rare-Earth Borohydride Complexes with DFT Studies

Abstract

The reactivity of rare-earth complexes RE(BH4)2(C3H5)(THF)x (RE = La, Nd, Sm, Y, Sc) toward the Ring-Opening Polymerization (ROP) of ε-caprolactone (ε-CL) was rationalized by Density Functional Theory (DFT) calculations. Even if the polymerization reaction can be initiated by both RE-(BH4) and RE-allyl bonds, experimental investigations have shown that the initiation via the borohydride ligand was favored, as no allyl group could be detected at the chain-end of the resulting polymers. DFT studies could confirm these observations, as it was highlighted that even if the activation barriers are both accessible, the allyl group is not active for the ROP of ε-CL due to the formation of a highly stable intermediate that disfavors the subsequent ring-opening.

Incorporation of expanded organic cations in dysprosium(III) borohydrides for achieving luminescent molecular nanomagnets

“…Synthesis of new systems was also stimulated due to their various other properties, as metal borohydrides can serve as e.g. solid-state electrolytes in Li + batteries 55 – 58 , organic catalysts 59 , 60 , precursors of metal borides 61 – 65 , or even boron nitride 66 . Lately, borohydrides of rare earth metal (RE) ions have been reported.…”

Alkenes and Allyl Complexes of the Group 3 Metals and Lanthanides

“…This experimental result was just recently corroborated by DFT studies, where the peculiar reactivity of the borohydride vs. the allyl group was explained by the lower stability of the product resulting from monomer insertion into Ln-allyl rather than Ln-(BH4) in 61Ln complexes. 87 In contrast, the metal-allyl bond was found to be more reactive than the metal-borohydride one towards the insertion of benzophenone, as expected from the literature, 6 and towards the protonation reaction with [HNMe2Ph][B(C6F5)4] and HC5Me4R (R = Me, Et, Scheme 37).…”

Molecular Ln(III)−H−E(II) Linkages (Ln=Y, Lu; E=Ge, Sn, Pb)

“…Besides the importance of parent hydride complexes, tetrahydridoborato, [6] organohydridoborato, [6f,7] and polydentate amino‐ or phosphinodiboranato derivatives emerged as prominent ligand classes [8] . Many of such highly reactive rare‐earth‐metal compounds draw on the stabilizing effect of B–H coordination [6i,7c,9] . Though of relevance for catalytic applications, the corresponding molecular Ln/Al‐bimetallic hydrides have not been as well studied.…”