Cationic Complexes with Au→Ge Bonds – Synthesis and Carbophilic Reactivity

Abstract

As part of our efforts to interface late transition metals with Lewis acidic main group fragments, we have decided to investigate gold complexes bearing halogermanes as Z‐type ligands. Toward this end, we have synthesized complexes of general formula [(o‐(Ph2P)C6H4)2(Ph)(X)GeAuCl] (X = F, Cl). Experimental and computational analyses indicate the presence of an Au→Ge interaction in both cases. Chloride abstraction reactions have also been investigated. In the case of X = Cl, double chloride abstraction with AgSbF6 affords a putative dication that gradually abstracts fluoride from its counterion. This putative dication is also significantly more active as a catalyst than its monocationic analog in alkyne hydroamination reactions.

Sterically Crowded Gold Germylene Compounds with Methyl and Hydride Substituents

“…It is important to notice that germanium dications have shown a remarkable reactivity as highly electrophilic centres [16,17] . Interestingly, Gabbai has just showcased the notably enhanced catalytic potential of a gold‐germylium dication compared to its monocationic analogue [18] . On these grounds, we have attempted the preparation of a sterically congested but low‐coordinate gold‐germylene dication.…”

“…[16,17] Interestingly, Gabbai has just showcased the notably enhanced catalytic potential of a gold-germylium dication compared to its monocationic analogue. [18] On these grounds, we have attempted the preparation of a sterically congested but lowcoordinate gold-germylene dication. Synthetically, we found that the stepwise abstraction of the two chlorides from precursor 1 was required to access such an electrophilic species.…”

Search for Osme Bonds with π Systems as Electron Donors

“…There are other transition metals that have been shown to participate in bonds of this sort. Karimi found a weak interaction between transition metals Au and Ge through theoretical and experimental studies [ 32 ]. After analyzing the X-ray structures of molybdenopterin and tungtrexin and conducting theoretical calculations, Bauzá et al found that there was an attractive interaction between Mo or W atoms and Lewis bases, which they dubbed the Wolfium bond (WfB) [ 33 ].…”

Au → M bonds promote catalytic alkyne hydrofunctionalisation

“…3 More recently, electron-withdrawing Z-type ligands have been used to produce efficient π-acid Au I catalysts. 4 Inagaki et al activated complex [Au I (dpb)Cl] 1 (DPB = d̲ip̲hosphinob̲orane) 5 with AgSbF 6 and employed the product complex 2-H as an efficient catalyst in enyne cycloisomerisation. 4 a Subsequently, electronic finetuning of the borane in 2-F and 2-Cl enabled other Au I -catalysed cycloisomerisation reactions (Fig.…”

“…Gabbaï's complex 4 (Δ δ = 5.6 4 f ) also fits well into this picture (3.5 mol% 4 , r.t., 7.5 h, 100% conversion of 14 , cf. ref. 4 g ).…”