Frustrated Lewis Pair Chemistry with Magnesium Lewis Acids

Abstract

Anilido imine–magnesium bromide complexes, (LHMgBr)2 and (LMeMgBr)2, have been prepared [LH = DIPP‐N(C6H4)C(H)N‐DIPP and LMe = DIPP‐N(C6H4)C(Me)N‐DIPP (DIPP = 2,6‐iPr2C6H3)]. Their dimeric crystal structures are compared to the dimer (DIPP‐nacnacMgBr)2 [DIPP‐nacnac = DIPP‐NC(Me)C(H)C(Me)N‐DIPP]. The anilido imine ligands show some degree of charge delocalization but are clearly more asymmetric than the DIPP‐nacnac complex: one of the N atoms has considerable anilido character, whereas the other one is close to an imine. Calculated natural population analysis (NPA) charges (B3PW91/6‐311++G**) and an atoms‐in‐molecules (AIM) study on model systems quantify the asymmetry in charge distribution. Quantification of the Lewis acidity of LHMgBr and LMeMgBr by the Gutmann–Beckett test gave acceptor numbers of 58.9 and 58.3, respectively. The complexes themselves are inert to a number of electrophiles; however, in combination with PPh3 the substrate 1‐butene oxide was ring‐opened. The resulting betaine‐type alkoxide complex is unstable and decomposes at room temperature through a Wittig‐type reaction. At higher temperatures also a reverse Wittig‐type decomposition is observed.

A Highly Lewis Acidic Strontium ansa‐Arene Complex for Lewis Acid Catalysis and Isobutylene Polymerization

“…In the literature, FLP systems incorporating Ae metals are scarce. In 2017, the group of Harder used a Mg‐based Lewis acid of type (NacNacMgBr) 2 in combination with PPh 3 for substrate activation of polar substrates, for example, acetone [11] . Moreover, the same group published a Ca II /Al I ‐FLP for stoichiometric benzene reduction, which heavily relied on the substantial reactivity of the Al I species [12] .…”

Schlenk‐Vorlesung: S. Harder / Kabiller‐Preis: R. S. Langer / Kabiller‐Preis für Nachwuchsforscher: L. Zhang / Wilhelm‐Manchot‐Professur: P. S. Baran

“…Im Zentrum seiner Forschung steht die Organometallchemie der frühen Hauptgruppenmetalle, wobei der Schwerpunkt auf der Katalyse und der Wasserstoffspeicherung liegt. In der Angewandten Chemie hat er Calcium‐ und Strontiumhydridcluster vorgestellt und im European Journal of Inorganic Chemistry Magnesium‐Lewis‐Säuren …”

Diverse Uses of the Reaction of Frustrated Lewis Pair (FLP) with Hydrogen

“…At the same time, the generality of such reactivity has been extended to a range of Lewis acid/Lewis base combinations. While many studies in this area focused on traditional main group acceptors and donors, the range of species exhibiting FLP reactivity has been extended to transition metals, rare earth metals, and group 1 and 2 metals . Thus, indeed FLP chemistry has implications across the periodic table.…”