Isolation of Transient Acyclic Germanium(I) Radicals Stabilized by Cyclic Alkyl(amino) Carbenes

Mesoionic imidazolylidenes are recognized as excellent electron‐donating ligands in organometallic and main group chemistry. However, these carbene ligands typically show poor π‐accepting properties. A computational analysis of 71 mesoionic imidazolylidenes that bear different aryl or heteroaryl substituents in C2 position was performed. The study has revealed that a diphenyltriazinyl (Dpt) substituent renders the corresponding carbene particularly π‐acidic. The computational results could be corroborated experimentally. A mesoionic imidazolylidene with a Dpt substituent was found to be a better σ‐donor and a better π‐acceptor compared to an Arduengo‐type N‐heterocyclic carbene. To demonstrate the utility of the new carbene, the ligand was used to stabilize a low‐valent paramagnetic tin compound.

Section: Introductionmentioning

confidence: 98%

“…The good electron‐accepting properties of CAAC ligands have also enabled the preparation of low‐valent main group element compounds. A recent example is the synthesis of a Ge(I) radical containing a CAAC and a silylamide ligand [40] . Pronounced spin density is found at the CAAC ligand.…”

Section: Introductionmentioning

confidence: 99%

Tuning the π‐Accepting Properties of Mesoionic Carbenes: A Combined Computational and Experimental Study

Dong

Blaskovits

Fadaei‐Tirani

et al. 2021

“…[17,18] There are ah andful of compounds containing heavy tetrel elements with an oxidation state of (I). Aside from some exceptions, [19][20][21] the field has been dominated by two main classes, the heavy alkyne analogues [22][23][24][25] and those supported by monoanionic chelating ligands (A-E in Figure 1). [26][27][28][29] Twoo utliers from this group are the Ge centered1 ,2-dications F and G,s upported by neutrald onors with the anionic charge insulated in the ligand backbone.…”

Section: Introductionmentioning

confidence: 99%

A Comprehensive Investigation of a Zwitterionic Ge^I Dimer with a 1,2‐Dicationic Core

Béland

Wang

Macdonald

et al. 2019

The reductive dehalogenation of a zwitterionic GeII species to make a zwitterionic GeI dimer with a 1,2‐dicationic core is reported herein. To the root of the stability of this compound, the molecular and electronic structures were comprehensively characterized and investigated using crystallographic, spectroscopic, and computational methods. It was determined that the Ge centers are attracted because they are both electron‐rich and positively charged. A comparison to the electronic structure in triphosphenium cations revealed varying degrees of covalent bonding and that this difference can be distinguished spectroscopically.

“…This is surprising given the popularity of low‐valent anionic aluminium nucleophiles [37–43] and is perhaps associated with the limited profile of anionic ligands in the chemistry of zero‐valent germanium. Replacing a neutral cAAC unit in germylone A for a charge bearing amido ligand allows the stabilization of radicals B [44] . Although electrochemical evidence suggests that anions may be obtained by reduction of B , [44] the only known example, C , has been independently reported and its reactivity remains unexplored [45] …”

Section: Figurementioning

confidence: 99%

“…Replacing a neutral cAAC unit in germylone A for a charge bearing amido ligand allows the stabilization of radicals B. [44] Although electrochemical evidence suggests that anions may be obtained by reduction of B, [44] the only known example, C, has been independently reported and its reactivity remains unexplored. [45] Aiming to develop the chemistry of low-valent germanium further, we deployed the electronic stabilization afforded by Me 2 -cAAC (1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidine-2-ylidene, 2,6-diisopropylphenyl = Dipp) in combination with sterically encumbering hypermetallyl ligands E-(SiMe 3 ) 3 (E = Si, Ge) that are not significantly π-withdrawing; cf.…”

mentioning

confidence: 99%

Low‐Valent Germanylidene Anions: Efficient Single‐Site Nucleophiles for Activation of Small Molecules

Gendy

Rautiainen

Mailman

et al. 2021

Rare mononuclear and helical chain low-valent germanylidene anions supported by cyclic (alkyl)(amino) carbene and hypermetallyl ligands were synthesised by stepwise reduction from corresponding germylene precursors via stable and isolable germanium radicals. The electronic structures of the anions can be described with ylidene and ylidone resonance forms with the GeÀ C πelectrons capable of binding even weak electrophiles. The germanylidene anions reacted with CO 2 to give μ-CO 2 -kC: kO complexes, a rare coordination mode for low-valent germanium and inaccessible for the related neutral germylones. These results implicate low-valent germanylidene anions as efficient single-site nucleophiles for activation of small molecules.