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Half‐sandwich iridium complexes of the type [(η5‐C5Me5){(NHC)E}IrCl] (E=P, As) were prepared by the reactions of N‐heterocyclic carbene (NHC) adducts of trimethylsilylphosphinidene and trimethylsilylarsinidene, (IDipp)ESiMe3 and (IMes)ESiMe3, with [(η5‐C5Me5)IrCl2]2 (IDipp=bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene; IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene). The molecular structure of [(η5‐C5Me5){(IDipp)As}IrCl] was established by X‐ray diffraction analysis, affording the first structurally authenticated NHC‐arsinidenide complex with a short Ir−As bond length that reveals a significant degree of metal‐arsenic π‐interaction as also confirmed by theoretical calculations. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Chloride abstraction from the complexes [(η6‐p‐cymene){(IDipp)P}MCl] (2 a, M=Ru; 2 b, M=Os) and [(η5‐C5Me5){(IDipp)P}IrCl] (3 b, IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) with sodium tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate (NaBArF) in the presence of trimethylphosphine (PMe3), 1,3,4,5‐tetramethylimidazolin‐2‐ylidene (MeIMe) or carbon monoxide (CO) afforded the complexes [(η6‐p‐cymene){(IDipp)P}M(PMe3)]BArF] (4 a, M=Ru; 4 b, M=Os), [(η6‐p‐cymene){(IDipp)P}Os(MeIMe)]BArF] (5) and [(η5‐C5Me5){(IDipp)P}IrL][BArF] (6, L=PMe3; 7, L=MeIMe; 8, L=CO). These cationic N‐heterocyclic carbene‐phosphinidene complexes feature very similar structural and spectroscopic properties as prototypic nucleophilic arylphosphinidene complexes such as low‐field 31P NMR resonances and short metal‐phosphorus double bonds. Density functional theory (DFT) calculations reveal that the metal‐phosphorus bond can be described in terms of an interaction between a triplet [(IDipp)P]+ cation and a triplet metal complex fragment ligand with highly covalent σ‐ and π‐contributions. Crystals of the C−H activated complex 9 were isolated from solutions containing the PMe3 complex, and its formation can be rationalized by PMe3 dissociation and formation of a putative 16‐electron intermediate [(η5‐C5Me5)Ir{P(IDipp)}I][BArF], which undergoes C−H activation at one of the Dipp isopropyl groups and addition along the iridium‐phosphorus bond to afford an unusual η3‐benzyl coordination mode. [ABSTRACT FROM AUTHOR]

Arsenic monophosphide (AsP) species supported by two different N‐heterocyclic carbenes were prepared by reaction of (IDipp)PSiMe3 (1) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) with (IMes)AsCl3 (2) (IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene) to afford the dichloride [(IMes)As(Cl)P(IDipp)]Cl (3), which upon reduction with KC8 furnished heteroleptic [(IMes)AsP(IDipp)] (4). The corresponding mono‐ and dications [(IMes)AsP(IDipp)][PF6], [5]PF6, and [(IMes)AsP(IDipp)][GaCl4]2, [6][GaCl4]2, respectively, were prepared by one‐electron oxidation of 4 with ferrocenium hexafluorophosphate, [Fc]PF6, or by chloride abstraction from 3 with two equivalents of GaCl3, respectively. Compounds 4–6 represent rare examples of heterodiatiomic interpnictogen compounds, and X‐ray crystal structure determinations together with density functional theory (DFT) calculations reveal a consecutive shortening of the As−P bond lengths and increasing bond order, in agreement with the presence of an arsenic–phosphorus single bond in 4 and a double bond in 62+. The EPR signal of the cationic radical [5]+. indicates a symmetric spin distribution on the AsP moiety through strong hyperfine coupling with the 75As and 31P nuclei. [ABSTRACT FROM AUTHOR]

Keywords: iridium; N-heterocyclic carbenes; arsenic; arsinidenes; phosphinidenes EN iridium N-heterocyclic carbenes arsenic arsinidenes phosphinidenes 1 1 1 04/18/23 20230414 NES 230414 The cover picture shows the crystal structure of an iridium complex with an N-heterocyclic carbene-arsinidenide ligand. This complex represents an N-heterocyclic carbene analogue of rare transition metal-arsinidene complexes and has the shortest iridium-arsenic bond length reported to date, indicating the presence of strong metal-arsenic -interaction. Front Cover: N-Heterocyclic Carbene-Arsinidenide Iridium Complexes (Z. Anorg. [Extracted from the article]

The reaction of the 2-(trimethylsilyl)imidazolium triflate 9 with diarylboron halides (4-R-C6H4)2BX (R=H, X=Br; R=CH3, X=Cl; R=CF3, X=Cl) afforded the NHC-stabilized borenium cations 10 a- c. Cyclic voltammetry revealed a linear correlation between the Hammett parameter σp of the para substituent and the half-wave potential. Chemical reduction with decamethylcobaltocene, [(C5Me5)2Co], furnished the corresponding radicals 11 a- c; their characterization by EPR spectroscopy confirmed the paramagnetic character of 11 a- c, with large hyperfine coupling constants to the boron isotopes 11B and 10B, while delocalization of the unpaired electron into the NHC is negligible. DFT calculations of the percentage of spin density distribution between the carbene (NHC) and the boryl fragments (BR2) revealed for 11 a- c a spin density ratio (BR2/NHC) of ca. 9:1, which underlines their distinct boryl radical character. The molecular structure of the most stable species 11 c was established by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The N-heterocyclic carbene-phosphinidene adduct IPr=PSiMe3 is introduced as a synthon for the preparation of terminal carbene-phosphinidyne transition metal complexes of the type [(IPr=P)MLn] (MLn=(η6-p-cymene)RuCl) and (η5- C5Me5)RhCl). Their spectroscopic and structural characteristics, namely low-field 31P NMR chemical shifts and short metal-phosphorus bonds, show their similarity with arylphosphinidene complexes. The formally mononegative IPr=P ligand is also capable of bridging two or three metal atoms as demonstrated by the preparation of bi- and trimetallic RuAu, RhAu, Rh2, and Rh2Au complexes. [ABSTRACT FROM AUTHOR]

Keywords: halogen bonding; hypervalency; iodine; London dispersion; N-heterocyclic carbenes EN halogen bonding hypervalency iodine London dispersion N-heterocyclic carbenes 4214 4214 1 03/03/21 20210301 NES 210301 B Iodine complexes of anionic N-heterocyclic carbenes b (NHC) act as electrophiles towards a variety of nucleophiles, with the interactions ranging from noncovalent charge-transfer or halogen bonding to covalent 3-center, 4-electron bonding. Cover Feature: Halogen Complexes of Anionic N-Heterocyclic Carbenes (Chem. Eur. J. 13/2021) Halogen bonding, hypervalency, iodine, London dispersion, N-heterocyclic carbenes. [Extracted from the article]

Cover Feature: N-Heterocyclic Carbene Analogues of Nucleophilic Phosphinidene Transition Metal Complexes (Chem. Eur. J. 65/2020) Keywords: iridium; N-heterocyclic carbenes; osmium; phosphinidenes; phosphorus ligands EN iridium N-heterocyclic carbenes osmium phosphinidenes phosphorus ligands 14773 14773 1 11/28/20 20201120 NES 201120 B N-Heterocyclic carbene-phosphinidene complexes b can be conceived as new and true members of the class of nucleophilic phosphinidene complexes according to their spectroscopic, structural, and electronic properties, since substitution of the aryl moiety in authentic neutral arylphosphinidene complexes of the type [ArP=ML SB I n i sb ] by an N-heterocyclic carbene affords the corresponding cationic complexes [(NHC)P=ML SB I n i sb ] SP + sp with equally short and covalent metal-phosphorus double bonds. Iridium, N-heterocyclic carbenes, osmium, phosphinidenes, phosphorus ligands. [Extracted from the article]

Abstract: Replacement of THF in [(η7-C7H7)Zr{C3H3(TMS)2}(thf)] (1) by trimethylphosphine (PMe3), 4-(dimethylamino)pyridine (DMAP), 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe) or 1,3,4,5-tetramethyl-2-methyleneimidazoline (H2C–IMe) resulted in the new 16-electron cycloheptatrienyl zirconium allyl complexes [(η7-C7H7)Zr{C3H3(TMS)2}(L)] (2: L = PMe3, 3: L = DMAP, 4: L = IMe, 5: L = H2C–IMe), which were all structurally characterized by X-ray diffraction analysis. The two-electron donor ligands are coordinated at the open edge of the 1,3-bis(trimethylsilyl)allyl ligand, which requires the TMS-substituents to point away from the metal (syn–syn orientation). In 5, the ylidic character of the exocyclic sp2 carbon atom of the ligand led to end-on coordination accompanied by a pronounced elongation of the C–C bond distance. According to DFT calculations on 1, 2 and 4 and a variable temperature NMR study on 2, the Zr–L bonds feature significantly higher stabilities than in the corresponding 18-electron adducts of [(η7-C7H7)Zr(η5-C5H5)]. [Copyright &y& Elsevier]

Arsenic monophosphide (AsP) species supported by two different N‐heterocyclic carbenes were prepared by reaction of (IDipp)PSiMe3 (1) (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) with (IMes)AsCl3 (2) (IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene) to afford the dichloride [(IMes)As(Cl)P(IDipp)]Cl (3), which upon reduction with KC8 furnished heteroleptic [(IMes)AsP(IDipp)] (4). The corresponding mono‐ and dications [(IMes)AsP(IDipp)][PF6], [5]PF6, and [(IMes)AsP(IDipp)][GaCl4]2, [6][GaCl4]2, respectively, were prepared by one‐electron oxidation of 4 with ferrocenium hexafluorophosphate, [Fc]PF6, or by chloride abstraction from 3 with two equivalents of GaCl3, respectively. Compounds 4–6 represent rare examples of heterodiatiomic interpnictogen compounds, and X‐ray crystal structure determinations together with density functional theory (DFT) calculations reveal a consecutive shortening of the As−P bond lengths and increasing bond order, in agreement with the presence of an arsenic–phosphorus single bond in 4 and a double bond in 62+. The EPR signal of the cationic radical [5]+. indicates a symmetric spin distribution on the AsP moiety through strong hyperfine coupling with the 75As and 31P nuclei. [ABSTRACT FROM AUTHOR]

Abstract: The reactions of the half-open trozircene [(η7-C7H7)Zr(η5-2,4-C7H11)] (1) with the two-electron donor ligands tert-butyl isocyanide (CN-tBu), 1,2-bis(dimethylphosphino)ethane (dmpe), trimethylphosphine (PMe3) and 1,3,4,5-tetramethylimidazolin-2-ylidene (IMe, :C[N(Me)C(Me)]2) have led to the 1:1 adducts 3, 4, 5 and 6, respectively. The latter three were structurally characterized by X-ray diffraction analysis. Additionally, the stability of the adducts was probed by DFT calculations employing the B3LYP and M05-2X functionals showing that the strongly σ-basic N-heterocyclic carbene forms a thermodynamically much more stable adduct than the other three. [ABSTRACT FROM AUTHOR]