Methylene-bridged, intramolecular donor–acceptor systems based on rare-earth metals and phosphinomethanides

Abstract

New geminally bonded intramolecular donor-acceptor systems, CpLnCHPR (Ln = Y, Ho, Er, R = CHMe, CMe), were prepared by salt elimination reactions between the dicyclopentadienyl-element chlorides (CpLnCl, Ln = Y, Ho, Er) and diorganylphosphinomethanides (RPCHLi; R = CHMe, CMe). These compounds, 1-6, were characterized by elemental analyses, mass spectrometry and X-ray diffraction experiments and the yttrium species additionally by NMR spectroscopy. In the solid state the molecular structures differ from each other, depending on the steric demand of the phosphorus substituents. For all iso-Pr-substituted compounds, dimers [CpLnCHP(CHMe)] with six-membered Ln-C-P-Ln-C-P rings in a chair-like conformation were observed. The sterically more demanding tert-butyl groups prevent dimerization but instead lead to species that undergo complexation of LiCl units by two monomers: [CpLnCHP(CMe)·LiCl]. The solution NMR data for the yttrium compounds are consistent with the solid-state structures. Conversion with phenylacetylene afforded heteroleptic cyclobutane-like alkynyl-rare-earth metal complexes [CpLn(μ-C[triple bond, length as m-dash]CPh)] [Ln = Y (7), Ho (8), Er (9)]. Treatment of compounds 1-6 with 1,8-diethynylanthracene led to single metalation and dimerization and products with similar structural motifs as observed for complexes 7-9. Reactions with dihydrogen and carbon dioxide resulted in Y-C bond breaking, yielding CpYH/RPCH and CO insertion products, respectively.

A Neutral Geminal Tin/Phosphorus Frustrated Lewis Pair

“…Most frequently studied are combinations of Group 13 Lewis acids (B, Al) and Group 15 Lewis bases (N, P) . Far less common are systems containing Si, Ge, Sn, rare‐earth metals, or transition metals (e.g. Zr, Zn, Sc) as Lewis acid functions.…”

“…[4] FLP reactivity is found for inter-a nd intramolecular combinations of Lewis acids and bases.Most frequently studied are combinations of Group 13 Lewis acids (B,A l) and Group 15 Lewis bases (N,P). [1,5] Farl ess common are systems containing Si, [6] Ge, [7] Sn, [7,8] rare-earth metals, [9] or transition metals (e.g.Z r, [10] Zn, [11] Sc [12] )a sLewis acid functions.T etrel Lewis acids were typically limited to silylium [6a-c] or stannylium [8d] ions and stannylenes. [8a-c, 13] Binding small molecules like CO 2 and SO 2 has recently sparked growing interest, in the context of the reduction and conversion of greenhouse and pollutant gases.…”

A Neutral Germanium/Phosphorus Frustrated Lewis Pair and Its Contrasting Reactivity Compared to Its Silicon Analogue

“…Nitrogen bases are also frequently used. Far less common are systems containing Al, C, Si, Ge, Sn, rare‐earth or transition elements (e.g. Zr, Zn, Sc) as acid functions.…”

Ein neutrales geminales frustriertes Zinn/Phosphor‐Lewis‐Paar

“…Am besten untersucht sind dabei Kombinationen aus Gruppe 13‐Lewis‐Säuren (B, Al) und Gruppe 15‐Lewis‐Basen (N, P) . Weitaus weniger verbreitet sind Systeme mit den Säurefunktionen Si, Ge, Sn, den Seltenerd‐ oder Übergangsmetallen (z. B. Zr, Zn, Sc).…”