A Zwitterionic Heterobimetallic Gold–Iron Complex Supported by Bis(N‐Heterocyclic Imine)Silyliumylidene

Abstract

The facile synthesis of the first bis‐N‐heterocyclic imine‐stabilized chlorosilyliumylidene 1 is reported. Remarkably, consecutive reaction of 1 with PPh3AuCl and K2Fe(CO)4 gives rise to the unique heterobimetallic complex 1,2‐(MesNHI)2‐C2H4‐ClSiAuFe(CO)4 (4). The overall neutral complex 4 bears an unusual linear Si−Au−Fe structure and a rare anagostic interaction between the d10‐configured gold atom and a CH bond of the mesityl ligand. According to the computational analysis and 57Fe Mössbauer spectroscopy, the formal Fe‐oxidation state remains at −II. Thus, the electronic structure of 4 is best described as an overall neutral—yet zwitterionic—heterobimetallic “Si(II)+‐Au(I)+‐Fe(‐II)2−”‐silyliumylidene complex, derived from double anion exchange. The computational analysis indicates strong hyperconjugative back donation from the gold(I) atom to the silyliumylidene ligand.

Chemistry of the Bis(imine)‐Based Tetradentate Ligand Stabilized Group 14 E(II) Cations (E=Ge and Sn)

“…The presence of such π‐back donation from Au(I) to bis( N ‐Heterocyclic Imine)silyliumylidene heterobimetallic Au−Fe complex has been reported by Inoue et al. very recently [26] . It is important to note that in our case, the structural non‐rigidity of the supporting ligand backbone allows the availability of the vacant orbitals on the Ge(II) dication in order to accommodate electron density from the metal center through π‐back donation.…”

“…The presence of such π-back donation from Au(I) to bis(N-Heterocyclic Imine)silyliumylidene heterobimetallic AuÀ Fe complex has been reported by Inoue et al very recently. [26] It is important to note that in our case, the structural non-rigidity of the supporting ligand backbone allows the availability of the vacant orbitals on the Ge(II) dication in order to accommodate electron density from the metal center through π-back donation. Thus, we have established the first example of lowvalent Group 14 E(II) cationic donor ligand that enhances the π-acidity at the bound transition metal center and hence their proclivity towards efficient Lewis acid catalysis.…”

Low Valent N‐Coordinated Cations and Dications of Heavier Group 14 Elements: Lewis Acids or Bases?

“…While there is no information for reactivity of 2 and 3 with heavier chalcogens, Inoue also extended the study of oxidative reactions to selenium and tellurium. The corresponding chlorosilaselenonium ( 12 ) and chlorosilatelluronium ( 13 ) salts are formed based on NMR analysis [12b] …”

“…investigated the coordination ability of 4 toward coinage metal salts CuCl, AgCl and Me 2 S⋅AuCl leading to the formation of desired complexes [{ L NHI−1 SiCl}CuCl][Cl] ( 16 ), [{ L NHI−1 SiCl}AgCl][Cl] ( 17 ) and [{ L NHI−1 SiCl}AuCl][Cl] ( 18 ) (Scheme 8). [12b] …”

N-Heterocyclic imine-based bis-gallium(i) carbene analogs featuring a four-membered Ga2N2 ring

“…43,44 An ethylene-bridged bidentate bis-NHI ligand, acting as a π-four-electron donor, was used to stabilize heavier tetryliumylidenes (III: E = Si, Ge, or Sn). 45,46 In contrast to monomeric I, dimeric IV and V both feature a four-membered E 2 N 2 (E = Ge or Sn) ring, in which V is derived from the reaction of a tin analog of carbenoid V′ with Me 3 SiCl. [47][48][49][50] Whereas NHIbased complexes of group 14 elements are well-documented, NHI complexes involving group 13 elements have only recently been revealed with the discovery of the neutral cyclic carbene analog VI (E = Ga, In, or Tl).…”