Martin Stanford

LS–HS switch: High‐pressure single‐crystal X‐ray diffraction has been used to trap both the low‐spin (LS) and high‐spin (HS) states of the iron(II) Hofmann spin crossover framework, [Fe^II(pdm)(H₂O)[Ag(CN)₂]₂⋅H₂O, under identical experimental conditions, allowing the structural changes arising from the spin‐transition to be deconvoluted from previously reported thermal effects.

Abstract

High‐pressure single‐crystal X‐ray diffraction has been used to trap both the low‐spin (LS) and high‐spin (HS) states of the iron(II) Hofmann spin crossover framework, [Fe^II(pdm)(H₂O)[Ag(CN)₂]₂⋅H₂O, under identical experimental conditions, allowing the structural changes arising from the spin‐transition to be deconvoluted from previously reported thermal effects.

Back to bases: The first parent phosphanylalanes and ‐gallanes stabilized only by a Lewis base were synthesized. These compounds are accessible via a salt metathesis reaction of LB⋅E′H₂Cl and LiPH₂⋅DME and a H₂ elimination reaction between LB⋅E′H₃ and PH₃, respectively.

Abstract

The synthesis and characterization of the first parent phosphanylalane and phosphanylgallane stabilized only by a Lewis base (LB) are reported. The corresponding substituted compounds, such as IDipp⋅GaH₂PCy₂ (1) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐ylidene) were obtained by the reaction of LiPCy₂ with IDipp⋅GaH₂Cl. However, the LB‐stabilized parent compounds IDipp⋅GaH₂PH₂ (3) and IDipp⋅AlH₂PH₂ (4) were prepared via a salt metathesis of LiPH₂⋅DME with IDipp⋅E′H₂Cl (E′=Ga, Al) or by H₂‐elimination reactions of IDipp⋅E′H₃ (E′=Ga, Al) and PH₃, respectively. The compounds could be isolated as crystalline solids and completely characterized. Supporting DFT computations gave insight into the reaction pathways as well as into the stability of these compounds with respect to their decomposition behavior.

Nature Chemistry, Published online: 25 November 2019; doi:10.1038/s41557-019-0365-z

Good to Si you: The first example of a genuine silanone, that is, an isolable silicon analogue of a ketone that contains an unperturbed Si=O bond, was synthesized. The structure and properties of this silanone were examined by a single‐crystal XRD analysis, NMR spectroscopy, and theoretical calculations. Bimolecular reactions revealed high electrophilicity on the Si atom and high nucleophilicity on the O atom of the Si=O bond.

Abstract

Despite tremendous efforts to synthesize isolable compounds with an Si=O bond, silicon analogues of ketones that contain an unperturbed Si=O bond have remained elusive for more than 100 years. Herein, we report the synthesis of an isolable silicon analogue of a ketone that exhibits a three‐coordinate silicon center and an unperturbed Si=O bond, thus representing the first example of a genuine silanone. Most importantly, this silanone does not require coordination by Lewis bases and acids and/or the introduction of electron‐donating groups to stabilize the Si=O bond. The structure and properties of this unperturbed Si=O bond were examined by a single‐crystal X‐ray diffraction analysis, NMR spectroscopy, and theoretical calculations. Bimolecular reactions revealed high electrophilicity on the Si atom and high nucleophilicity on the O atom of this genuine Si=O bond.

Uneasy lies the head that wears a crown: The initial product from the reaction of a two‐coordinate aluminyl anion with 1,3,5,7‐cyclooctatetraene (COT) contains the reduced COT‐ligand with pronounced aromatic character. Addition of 18‐crown‐6 to K[Al(NON^Ar)(COT)] promotes isomerization of the carbocycle to afford the 9‐aluminabicyclo[4.2.1]nona‐2,4,7‐triene anion.

Abstract

The potassium aluminyl complex K[Al(NON^Ar)] (NON=NON^Ar=[O(SiMe₂NAr)₂]²⁻, Ar=2,6‐iPr₂C₆H₃) reacts with 1,3,5,7‐cyclooctatetraene (COT) to give K[Al(NON^Ar)(COT)]. The COT‐ligand is present in the asymmetric unit as a planar μ₂‐η²:η⁸‐bridge between Al and K, with additional K⋅⋅⋅π‐aryl interactions to neighboring molecules that generate a helical chain. DFT calculations indicate significant aromatic character, consistent with reduction to [COT]²⁻. Addition of 18‐crown‐6 causes a rearrangement of the C₈‐carbocycle to form the isomeric 9‐aluminabicyclo[4.2.1]nona‐2,4,7‐triene anion.

Abstract

Abstract