Influence of ligand rigidity and steric bulk on reductions of tridentate NON-diamido alkaline earth metal complexes.

Authors

Dat T Nguyen, Corinna Czernetzki, Joseph M Parr, Cameron Jones

Published in

Dalton transactions (Cambridge, England : 2003). Sep 15, 2026. Epub Sep 15, 2026.

Abstract

Structural modifications to tridentate NON ligands have been shown to play a key role in controlling the outcomes of group 2 metal diamide reduction reactions. Herein, two bulky, geometrically flexible diamines, ^FNON^ArH₂ (^FNON^ArH₂ = O{2-N(H)Ar-4-^tBuC₆H₃}₂; Ar = 2,4,6-ⁱPr₃C₆H₂ (Trip); 2,4,6-Cy₃C₆H₂ (TCHP)), have been synthesised. Treatment of ^FNON^TripH₂ with one equivalent of either BePh₂, Mg{CH₂(SiMe₃)}₂, or Ca{N(SiMe₃)₂}₂ in methylcyclohexane yielded group 2 metal diamide complexes. In the solid-state, monomeric [Be(^FNON^Trip)] features a T-shaped beryllium geometry, whereas the magnesium and calcium analogues [{Ae(^FNON^Trip)}₂] (Ae = Mg or Ca) are dimeric with distinct aggregation modes in the solid state. Although the strontium and barium counterparts could not be isolated, their treatment with THF led to structurally characterised [Ae(^FNON^Trip)(THF)_n] (Ae = Sr, n = 3; Ae = Ba, n = 4). Analogous deprotonations of the super-bulky ^FNON^TCHPH₂ pro-ligand in toluene afforded donor-free [Be(^FNON^TCHP)], the toluene adduct complexes, [Ae(^FNON^TCHP)(PhMe)] (Ae = Mg, Ca), and the N-bridged dimeric barium system, [{Ba(^FNON^TCHP)}₂]. Potassium reductions of these group 2 metal diamides led to a variety of outcomes, including reductive ligand C-O cleavage processes, yielding K₂[Mg{OC₆H₃^tBu-4-N(Trip)-2}{C₆H₃^tBu-4-N(Trip)-2}{Mg(^FNON^Trip)}], K₂[Be{OC₆H₃^tBu-4-N(TCHP)-2}{N(TCHP)(C₆H₄^tBu-3)}]₂, possible O₂ activation giving trace yields of [K₂{Mg(^FNON^TCHP)}₂(μ-O)], and metal hydride formation via solvent hydrogen abstraction, leading to [K₂{Ca(^FNON^TCHP)(μ-H)}₂]. All of these reduction reactions are thought to proceed via transient, reactive metal(I) radical species K[Ae(^FNON^Ar)˙].

PMID:
42742104
Bibliographic data and abstract were imported from PubMed on 15 Sep 2026.

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