The lithium complexes [(WCA‐NHC)Li(toluene)] of anionic N‐heterocyclic carbenes with a weakly coordinating anionic borate moiety (WCA‐NHC) reacted with iodine, bromine, or CCl4 to afford the zwitterionic 2‐halogenoimidazolium borates (WCA‐NHC)X (X=I, Br, Cl; WCA=B(C6F5)3, B{3,5‐C6H3(CF3)2}3; NHC=IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene, or NHC=IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene). The iodine derivative (WCA‐IDipp)I (WCA=B(C6F5)3) formed several complexes of the type (WCA‐IDipp)I⋅L (L=C6H5Cl, C6H5Me, CH3CN, THF, ONMe3), revealing its ability to act as an efficient halogen bond donor, which was also exploited for the preparation of hypervalent bis(carbene)iodine(I) complexes of the type [(WCA‐IDipp)I(NHC)] and [PPh4][(WCA‐IDipp)I(WCA‐NHC)] (NHC=IDipp, IMes). The corresponding bromine complex [PPh4][(WCA‐IDipp)2Br] was isolated as a rare example of a hypervalent (10‐Br‐2) system. DFT calculations reveal that London dispersion contributes significantly to the stability of the bis(carbene)halogen(I) complexes, and the bonding was further analyzed by quantum theory of atoms in molecules (QTAIM) analysis.

A series of neutral iridium(I) complexes of the general type [(WCA−NHC)]IrL(COD)] (COD=1,5‐cyclooctadiene; L=phosphine, pyridine), bearing anionic N‐heterocyclic carbenes (WCA−NHC) with a weakly coordinating anionic (WCA) borate moiety, were prepared by addition of phosphines and pyridine to [(WCA−NHC)]Ir(COD)], in which the available coordination site is stabilized by intramolecular metal‐arene interaction (π‐face donation). The solvent and substrate scope of the neutral complexes as catalysts for H/D exchange was investigated, revealing their suitability for promoting efficient deuteration in nonpolar solvents such as cyclohexane.

Anionic N-heterocyclic carbenes with weakly coordinating borate, aluminate, and gallate moieties of the type [(F 5 C 6 ) 3 E-NHC] − (E = B, Al, Ga) were isolated as lithium salts by the lithiation of 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (IMes) or 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene (IDipp) followed by the addition of E(C 6 F 5 ) 3 (E = B, Al, Ga). Treatment with elemental selenium afforded the lithium salts of the corresponding anionic selenourea derivatives [{(F 5 C 6 ) 3 E-NHC}Se] − (NHC = IMes, E = B; NHC = IDipp, E = B, Al, Ga), which were examined, among other things, by means of 77 Se{ 1 H} NMR spectroscopy to assess the π-accepting properties of the WCA-NHC ligands in comparison with their neutral NHC congeners.

The lithium complexes [(WCA-NHC)Li(toluene)] of anionic N-heterocyclic carbenes with a weakly coordinating borate moiety (WCA-NHC, WCA = B(C 6 F 5 ) 3 , NHC = IDipp = 1,3bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) were used for the preparation of silver(I) or copper(I) WCA-NHC complexes. While the reactions in THF with AgCl or CuCl afforded anionic mono-and dicarbene complexes with solvated lithium counterions [Li(THF) n ] + (n = 3, 4), the reactions in toluene proceeded with elimination of LiCl and formation of the neutral phosphine and arene complexes [(WCA-NHC)M(PPh 3 )] and [(WCA-NHC)M(η 2 -toluene)] (M = Ag, Cu). The latter were used for the preparation of chlorido-and iodido-bridged heterobimetallic Ag/Ru and Cu/Ru complexes [(WCA-NHC) M(μ-X) 2 Ru(PPh 3 )(η 6 -p-cymene)] (M = Ag, Cu, X = Cl; M = Ag, X = I). Surprisingly, these complexes resisted the elimination of CuCl, AgCl, or AgI, precluding WCA-NHC transmetalation.

The known compound diphenyl([2.2]paracyclophanyl)phosphane 1 reacted smoothly with elemental sulfur or selenium to give the phosphane chalcogenides 3 and 4. The corresponding chlorido- or bromido-gold(I) complexes were however not obtained by the usual reaction with (tht)AuCl or (tht)AuBr. For the latter, direct oxidation of the reaction mixture with elemental bromine led to small quantities of {(PCP)PPh2Br}+ [AuBr4]−5 (PCP = [2.2]paracyclophanyl). Attempts to obtain the alkyl phosphane di-isopropyl([2.2]paracyclophanyl)phosphane 2 were at first unsuccessful because of contamination by the phosphonium derivatives [iPr2(PCP)PH]+X− (X = Cl 6, X = Br 7), but the mixture was found to react with elemental sulfur or selenium to give the phosphane chalcogenides 8 and 9. The gold(I) complexes (PCP)iPr2PEAuX [E = S, X = Cl (10), Br (11); E = Se, X = Cl (12), Br (13)] were obtained by the reactions of 8 and 9 with (tht)AuX. The chlorido complexes 10 and 12 were oxidized by PhICl2 to the gold(III) complexes (PCP)iPr2PEAuCl314 (E = S) and 15 (E = Se). An excess of PhICl2 led to the fully oxidized compound {(PCP)iPr2PSeCl}+[AuCl4]−16. The bromido complexes 11 and 13 were oxidized by elemental bromine to (PCP)iPr2PEAuBr317 (E = S) und 18 (E = Se), the latter however with a poor yield. Further oxidation was not achieved. The reactions of the chalcogenides 3, 4, 8 and 9 with elemental iodine led to the products 19, 20, 21 (1:1 adducts) and 22 (1:1 adduct with additional disordered diiodine), respectively.