Group 13 Element Trihalide Complexes of Anionic N‐Heterocyclic Carbenes

Abstract

A series of group 13 complexes of the general type [{(WCA‐IDipp)EX3}Li(solv)] (E=B, Al, Ga, In; X=Cl, Br) that bear an anionic N‐heterocyclic carbene ligand with a weakly coordinating borate moiety (WCA‐IDipp, WCA=B(C6F5)3 and IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) were prepared by the reaction of the respective group 13 trihalides (EX3) with the lithium salt [(WCA‐IDipp)Li ⋅ toluene]. The molecular structures of the BBr3, AlCl3, AlBr3, GaCl3 and InCl3 adducts were established by X‐ray diffraction analyses, revealing the formation of coordination polymers linked by halide‐lithium interactions, except for the indium derivative, which consists of isolated [Li(THF)4]+ and [(WCA‐IDipp)InCl3]− ions in the solid state.

Determination of the π-Accepting Properties of Borate-, Aluminate-, and Gallate-Functionalized N-Heterocyclic Carbenes by 77Se NMR Spectroscopy

“…Anionic N-heterocyclic carbenes are another important variation of classical NHC ligands, and our group introduced a new type that contains a weakly coordinating borate moiety (WCA = B­(C 6 F 5 ) 3 ) at the C4 position of the imidazole ring. These new ligands were termed WCA-NHCs and were used as ancillary ligands in transition-metal complexes and in homogeneous catalysis. − More recently, these anionic carbenes made their first appearance in main group element chemistry and were used for the preparation of neutral dipnictenes (WCA-IDipp) 2 E 2 (IDipp = 1,3-bis­(2,6-diiso­propyl­phenyl)­imidazolin-2-ylidene; E = P, As, Sb, Bi) and cationic dipnictenes [(WCA-IDipp)­EP­(IDipp)] + (E = P, As) together with their related neutral radical species [(WCA-IDipp)­EP­(IDipp)] · . − WCA-NHC complexes containing group 13, 16, and 17 elements were also reported. − Thereby, the selenium derivative within the series of chalcogen complexes [(WCA-Dipp)­E]­Li·(solvent) (E = O, S, Se, Te) offers the possibility to assess the π-accepting properties of the WCA-IDipp ligand by 77 Se NMR spectroscopy . Since lithium coordination could affect the 77 Se chemical shift, its exchange by weakly coordinating counterions such as [PPh 4 ] + should be considered.…”

N‐Heterocyclic Carbenes Carrying Weakly Coordinating Anions

“…( 20 ) feature tetracoordinated boron, aluminum, gallium, or indium atoms in the solid‐state structures, respectively. Furthermore, the lithium atoms initiate the formation of coordination polymers, except for the indium trichloride derivative, where the lithium cation is fully solvated by four THF molecules [49] …”

“…Furthermore, the lithium atoms initiate the formation of coordination polymers, except for the indium trichloride derivative, where the lithium cation is fully solvated by four THF molecules. [49] Halogen complexes of WCA-NHCs were targeted by our group in 2020, [50] since the concept of halogen bonding is an important issue in azolium-based compounds, where the electrophilicity of the polarized halogen atom can be exploited to coordinate nucleophilic compounds (σ-hole interaction). 9), compounds which we regard as important synthons for the "free" anionic Nheterocyclic carbene.…”

Heterobimetallic Coinage Metal‐Ruthenium Complexes Supported by Anionic N‐Heterocyclic Carbenes

“…[12] Related anionic analogues of NHCs in which the borate unit is attached to the heterocycle via a methylene (CH 2 ) spacer were also used in transition metal chemistry. [13] Lately, the lithium salts 1 were employed for the preparation of WCA-NHC complexes of the heavier p-block elements, covering groups 13, [14] 15, [15] 16, [16] and 17. [17] In search for alternative transmetalation reagents, sodium and potassium salts of WCA-NHCs were recently introduced, however, their synthesis through deprotonation of IDipp with It should be noted that formal charges are shown here to illustrate the anionic nature of the N-heterocyclic carbene ligands; in the following, however, formal charges will be omitted to avoid the assignment of awkward charges in transition metal complexes.…”

“…[12] Related anionic analogues of NHCs in which the borate unit is attached to the heterocycle via a methylene (CH 2 ) spacer were also used in transition metal chemistry. [13] Lately, the lithium salts 1 were employed for the preparation of WCA‐NHC complexes of the heavier p‐block elements, covering groups 13, [14] 15, [15] 16, [16] and 17. [17] …”