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In X‐ray structures of the isomorphic mer‐[IrX3(THT)(CNXyl)2] (X=Cl 1, Br 2; THT=tetrahydrothiophene; Xyl=2,6‐Me2C6H3−) complexes, we revealed short intermolecular contacts between the C‐atom of an isocyanide methyl group and halide ligands of another molecule. Geometrical consideration of the X‐ray data and analysis of appropriate DFT studies allowed the attribution of these contacts to CMe⋅⋅⋅X−IrIII (X=Cl, Br) tetrel bond. Specifically, through the application of DFT calculations and various theoretical models, the presence of tetrel bonding interactions was validated, and the contribution of the CMe⋅⋅⋅X−IrIII interaction was assessed. The reinforcement of the tetrel bond upon the isocyanide coordination to iridium(III) is substantiated by molecular electrostatic potential (MEP) surface calculations. To distinguish the tetrel bonding characteristics of CMe⋅⋅⋅X−IrIII (X=Cl, Br) interactions from conventional hydrogen bonding, we employed multiple computational methodologies, including Natural Bond Orbital (NBO) analysis and Electron Localization Function (ELF) analysis. Additionally, Energy Decomposition Analysis (EDA) was applied to selected model systems to explore the underlying physical nature of these interactions. [ABSTRACT FROM AUTHOR]

Inspection of the X-ray structure of the newly prepared trans-[PdCl(CNXyl)ADC] (ADC = XylNH–C_;＝N–[5-iodo-2,6-dimethylpyrimidin-4-yl]) complex made it possible to identify for the first time the π-hole interaction involving the nitrogen atom of a coordinated isocyano group with a lone pair. Processing of available CSD data and results of DFT calculations revealed the possibility of two different sites for π-hole interaction involving isocyanides, i.e. both isocyano carbon and nitrogen centers are capable of acting as the π-hole donor toward lone pairs. [ABSTRACT FROM AUTHOR]

The reaction of bis(isocyanide)palladium complex cis-[PdCl2(CNXyl)2] (Xyl=2,6-Me2C6H3) with excess of 4,5-dichlorobenzene-1,2-amine in a C2H4Cl2/MeOH mixture affords monocationic bis(diaminocarbene) complex cis-[PdClC{(NHXyl)=NHC6H2Cl2NH2}{C(NHXyl)=NHC6H2Cl2NH2}]Cl (3) in moderate yield (42%). Complex 3 exists in the solid phase in the H-bonded dimeric associate of two single charged organometallic cations and two chloride anions according to X-ray diffraction data. The Hirshfeld surface analysis for the X-ray structure of 3 reveals that the crystal packing is determined primarily by intermolecular contacts H–Cl, H–H, and H–C. The intermolecular hydrogen bonds N–H···Cl and C–H···Cl in the H-bonded dimeric associate of 3 were studied by DFT calculations and topological analysis of the electron density distribution within the framework of QTAIM method, and estimated energies of these supramolecular contacts vary from 1.6 to 9.1 kcal/mol. Such non-covalent bonding means that complex 3 is an anionic receptor for the chloride anions. [ABSTRACT FROM AUTHOR]

Reaction of the palladium(II) and platinum(II) isocyanide complexes cis-[MCl2(CNR)2] [M = Pd, R = C6H3(2,6-Me2) (Xyl), 2-Cl-6-MeC6H3, cyclohexyl (Cy), t-Bu, C(Me)2CH2(Me)3 (1,1,3,3-tetramethylbuth-1-yl abbreviated as tmbu); M = Pt, R = Xyl, 2-Cl-6-MeC6H3, Cy, t-Bu, and tmbu] with N,N'-diphenylguanidine (DPG) leads to DPG-derived metal-bound deprotonated acyclic diaminocarbene (ADC) species. This reaction occurs via a two-step process, involving the initial coupling of the guanidine with one of the isocyanides and leading to deprotonated monocarbene monochelated species, while the next addition grants the deprotonated bis-carbene bis-chelated metal compounds. DPG behaves as nucleophile, deprotonating base, and chelator. The addition of DPG proceeded with different regioselectivity depending on the metal center and, in a larger extent, on the substituent R in RNCs. The X-ray diffraction studies for the deprotonated mono- and bis-carbene complexes confirmed the regioisomerism of these species and allowed the identification of ADC protolytic forms stabilized in the solid-state. 1D (1H and 13C{1H}) and 2D (1H,1H-NOESY; 1H,15N-HSQC; 1H,15N-HMBC) solution NMR of the obtained systems demonstrated their configuration isomerism accompanied by prototropic tautomerism. Together, the solid-state and solution data provide an insight into the flexible character of ADC species. [ABSTRACT FROM AUTHOR]

The reaction between equimolar amounts of the isocyanide complexes [AuCl3(CNR)] [R = 2,6-Me2C6H3 (Xyl), 1a; 2,4,6-Me3C6H2 (Mes), 1b; Cy, 1c; t-Bu, 1d] and tetrabutylammonium azide (2) proceeds in CH2Cl2 at room temperature for ~10 min to furnish the gold(III) tetrazolates [n-Bu4N][AuCl3(CN4R)] (3a-d), which were obtained in 89-95% yields after purification. Subsequent reaction between equimolar amounts of 3a-d and methyl trifluoromethanesulfonate (MeOTf) proceeds in CH2Cl2 at -70 °C for ~30 min to give the corresponding gold(III) complexes [AuCl3(CaN(Me)N2NbR)]a-b (5a-d) bearing 1,4-disubstituted tetrazol-5-ylidene ligands (69-75%). Complexes 3a-d were obtained as pale-yellow solids and characterized by elemental analyses (C, H, N), HRESI--MS, FTIR, and ¹H and 13C{¹H} NMR spectroscopies. Complexes 5a-d were obtained as colorless solids and characterized by elemental analyses (C, H, N), HRESI+-MS, and 1D (¹H and 13C{¹H}) and 2D (¹H,13C-HMBC) NMR spectroscopies. In addition, the structures of 3a, 3b, 3c, and 5a were established by single-crystal X-ray diffraction. Analysis of the Wiberg bond indices (WI) for gas phase-optimized model structures of 3a-c and 5a computed using the natural bond orbital (NBO) partitioning scheme disclosed a higher degree of electron density delocalization in the CN4 moiety of carbene 5a when compared to tetrazolate 3a-c. Results of DFT calculations for a model system reveal that the mechanism for the cycloaddition of an azide to the isocyanide ligand in [AuCl3(CNMe)] is stepwise and involves nucleophilic attack of N3- on the N atom of CNMe followed by ring closure. The addition is both kinetically and thermodynamically favorable and occurs via the formation of an acyclic NNNCN intermediate, whereas the cyclization is the rate-determining step. [ABSTRACT FROM AUTHOR]

Reactivity of 4-toluidine ( 2 ) and 4,5-dimethylbenzene-1,2-diamine ( 3 ) were compared in coupling with the palladium- bis (isocyanide) complex cis -[PdCl 2 (CNXyl) 2 ] (Xyl = 2,6-Me 2 C 6 H 3 , 1 ), mixed isocyanide/diaminocarbene species cis -[PdCl 2 (CNXyl){C(NHXyl) NH(4-C 6 H 4 CH 3 )}] ( 4 ), and cis -[PdCl(CNXyl){ C (NHXyl) NHC 6 H 2 (Me) 2 N H 2 }]Cl ( 5 ). In these Pd(II)-mediated reactions, 4,5-dimethylbenzene-1,2-diamine ( 3 ) was significantly more reactive than 4-toluidine ( 2 ), leading to the first mixed bis (diaminocarbene) complex cis -[PdCl{ C (NHR) NHC 6 H 2 X 2 N H 2 }{C(NHXyl) NH(4-C 6 H 4 CH 3 )}]Cl ( 6 ) containing two different diaminocarbene ligands. Complex 6 was isolated and characterized by elemental analyses (C, H, N), HRESI + -MS, IR, 1 H and 13 C{ 1 H} NMR spectroscopies, and single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Treatment of gold(III)-isocyanides [AuCl3(CNR¹)] (R¹ = Xyl 1, Cy 2, But 3) with an equimolar amount of 5,5-dimethyl-1-pyrroline-N-oxide (4) in CH2Cl2 at −74 °C leads to the generation of the heterocyclic aminocarbene species [AuCl3{C(ONaCMe2CH2CH2CbH)NeR¹}(Na-Cb)(Cb-Ne)] 8 (for R¹ = But) or gold(III) complexes cis-[AuCl2{Na(CMe2CH2CH2CbNeR¹)CdO}(NaCb)(Ne-Cd)] 9 and 10 (for R¹ = Xyl and Cy) in good isolated yields (75-87%). DFT calculations show that deprotonation of the endocyclic CH group in the carbene ligand leads to spontaneous N-O bond cleavage, and acidity of this group is a factor controlling the different chemical behavior of 1-3 depending on the nature of substituent R¹. The reaction of equimolar amounts of the aldonitrone p-TolCHN+(Me)O- (5) or the ketonitrones Ph2CN+(R²)O- (R² = Ph 6, CH2Ph 7) with 1-3 in CD2Cl2 at −70 °C in air (or under N2) revealed the formation of the carbene complexes [AuCl3{C(ONMeCaH-p-Tol)NbR¹}(Ca-Nb)] (R¹ = Cy 11, Xyl 12, But 13), [AuCl3{C(ONPhCaPh2)NbR¹}(Ca-Nb)] (R¹ = Cy 14, But 15), or [AuCl3{C(ON(CH2Ph)CaPh2)NbR¹}(Ca-Nb)] (R¹ = Cy 16, Xyl 17), as studied by ¹H NMR. The reaction of 6 with 1 and of 7 with 3 did not furnish carbene products. Compounds 8-10 were characterized by ESI-MS, IR, 1D (¹H, 13C{H}) and 2D (¹H,¹H-COSY, ¹H,13C-HSQC, ¹H,13C-HMBC) NMR spectroscopic techniques, and, only for 8, elemental analyses (C, H, N), while compounds 11-17 were characterized by 1D (¹H, 13C{H}) and 2D (¹H,13C-HSQC) NMR. Structures of compounds 8, 9, and 13 were additionally established by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

Coupling of the palladium-bis(isocyanide) complexes cis-[PdCl2(CNR)2] (R = 2,6-Me2C6H3 1, 2-Cl-6-MeC6H3 2) with benzene-1,3-diamine (BDA1) leads to the diaminocarbene species cis-[PdCl2(CNR){C(NHR)═NH(1,3-C6H4NH2)}] (5 and 6, respectively). In this reaction, BDA1 behaves as a monofunctional nucleophile that adds to one of the RNC ligands by one amino group. By contrast, the reaction of 1 and 2 with benzene-1,4-diamine (BDA2) involves both amino functionalities of the diamine and leads to the binuclear species [cis-PdCl2(CNR){μ-C(NHR)═NH(1,4-C6H4)NH═C(NHR)}-(cis)-PdCl2(CNR)] (6 and 7) featuring two 1,4-bifunctional diaminocarbene ligands. The reaction of cis-[PdCl2(CNR)2] (R = cyclohexyl 3) with either BDA1 or BDA2 does not afford any isolable carbene derivatives. The most versatile chemistry was observed when 1-3 were treated with benzene-1,2-diamine (BDA3) and the relevant substituted 1,2-diamines, viz., 4,5-dimethylbenzene-1,2-diamine (BDA4) and 4,5-dichlorobenzene-1,2-diamine (BDA5). The addition of these diamines brings about the formation of the monocarbene cationic complexes cis-[PdCl(CNR){C(NHR)═NHC6H2X2NH2}]Cl (X = H, Me, Cl) (8-16), the Chugaev-type C,C-bound bis-carbenes cis-[PdCl2{C(NHR)═NHC6H2X2NH═C(NHR)}] (17, 18), and the bis(C,N-chelated)carbene complexes cis-[Pd{C(NHR)═NHC6H2X2NH2}2]Cl2 (19-24). All prepared complexes (with the exception of 17 and 18) were isolated as colorless or pale yellow solids and characterized by elemental analyses (C, H, N), HRESI±-MS, IR, 1H and 13C{1H} NMR spectroscopies, and 4, 7, 13, 16, and 24 by X-ray diffraction. Complexes 17 and 18 were characterized by HRESI±-MS and IR spectroscopy, and their structures were established by X-ray crystallography. [ABSTRACT FROM AUTHOR]

Metal-mediated coupling of one isocyanide in cis -[PdCl 2 (CNR 1 ) 2 ] (R 1 = C 6 H 11 (Cy) 1 , t Bu 2 , 2,6-Me 2 C 6 H 3 (Xyl) 3 , 2-Cl-6-MeC 6 H 3 4 ) and various carbohydrazides R 2 CONHNH 2 [R 2 = Ph 5 , 4-ClC 6 H 4 6 , 3-NO 2 C 6 H 4 7 , 4-NO 2 C 6 H 4 8 , 4-CH 3 C 6 H 4 9 , 3,4-(MeO) 2 C 6 H 3 10 , naphth-1-yl 11 , fur-2-yl 12 , 4-NO 2 C 6 H 4 CH 2 13 , Cy 14 , 1-(4-fluorophenyl)-5-oxopyrrolidine-3-yl 15 , (pyrrolidin-1-yl)C(O) 16 , 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propane-1-yl 17 , EtNHC(O) 18 ] or sulfohydrazides R 3 SO 2 NHNH 2 [R 3 = Ph 19 , 4-MeC 6 H 4 20 ] led to a series of (hydrazido)(amino)carbene complexes cis -[PdCl 2 { C (NHNHX) N(H)R 1 }(CNR 1 )]; X = COR 2 , SO 2 R 3 ( 21 – 48 , isolated yields 60–96%). All prepared species were characterized by elemental analyses (C, H, N), HR ESI + -MS, IR, 1 H and 13 C{ 1 H} NMR spectroscopy, and by a single-crystal X-ray diffraction for 38 . Complexes 21 – 48 demonstrated excellent activity as catalysts in copper-free Sonogashira coupling of aryl iodides and a variety of aromatic terminal alkynes. Catalytic system runs in environmentally benign EtOH ensuring product yields of up to 75–96% and TONs of up to 10 4 . Mechanism of the copper-free Sonogashira catalytic cycle involving 21 – 48 as catalysts was proposed upon identification of key intermediates using HRESI-mass. [ABSTRACT FROM AUTHOR]

Highlights: [•] Dibromo-bis-isocyanide Pd complexes are prepared via metathetical reaction from chlorides. [•] Geometry of complexes in solution and solid-state is established on basis of spectroscopic data. [•] trans coordination modes are preferable for dibromo species in solution and in a solid state. [ABSTRACT FROM AUTHOR]

A reaction between equimolar amounts of cis-[PdCl2(CNCy)2] (1) and indazole (HInd, 2) or 5-methylindazole (HIndMe, 3) proceeded in refluxing CHCl3 for ca. 6 h affording the aminocarbene species cis-[PdCl2{C(Ind)=N(H)Cy}(CNCy)] (4) or cis-[PdCl2{C(IndMe)=N(H)Cy}(CNCy)] (5) in good (72–83%) isolated yields. Complexes 4 and 5 were characterized by elemental analyses (C, H, N), HR ESI+-MS, IR, and 1D (1H, 13C{1H}) and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC, 1H,13C-HMBC) NMR spectroscopies, and complex 4 as well by X-ray diffraction. The observed coupling represents the first example of metal-mediated integration between any isocyanide and any aromatic heterocyclic system having an HN center. [ABSTRACT FROM AUTHOR]

The isocyanide complexes cis-[MCl2(CNC6H4-4-X)2] (M = Pd; X = Cl, Br; M = Pt; X = Br) form isomorphous crystal structures exhibiting the Cl/Br and Pd/Pt exchanges featuring 1D chains upon crystallisation. Crystal packing is supported by the C–X···X–C halogen bonds (HaBs), C–H···X–C hydrogen bonds (HB), X···M semicoordination, and C···C contacts between the C atoms of aryl isocyanide ligands. The results of DFT calculations and topological analysis indicate that all the above contact types belong to attractive noncovalent interactions. A projection of the electron localization function (ELF) and an inspection of the electron density (ED) and the electrostatic potential (ESP) reveal the amphiphilic nature of X atoms playing the role of HaB donors, HaB and HB acceptors, and a nucleophilic partner in X···M semicoordination. [ABSTRACT FROM AUTHOR]

• Acyclic diaminocarbene (ADC) ligands exhibit a variety of reactivity modes. • Nucleophilic addition to metal-bound isocyanides is a principal route to metal-ADCs. • Deprotonation of the protic ADCs leads to the formamidinyl derivatives. • Intermolecular metallation of the deprotonated ADCs leads to bimetallic species. • Oxidation of ADCs leads to carbodiimide, amidine or guanidine derivatives. Acyclic diaminocarbenes (ADCs) are powerful ligands with a broad application scope in organometallic chemistry, catalysis, photophysics and crystal engineering. Although the preparation and application of metal-ADC species are discussed in many reports, the reactivity of ADC ligands is much less scrutinised. However, studies emerged indicate that ADC ligands, in particular, those prepared via the metal-mediated nucleophilic addition to isocyanides, can be further converted into various post-functionalised derivatives. In this review, we attempt for the first time to rationalise the most important reactivity modes of metal-ADC species reported up to date. [ABSTRACT FROM AUTHOR]

The metal-mediated coupling between cis -[PdCl 2 (CNR 1 ) 2 ] [R 1 = cyclohexyl (Cy) 1, t -Bu 2, 2,6-Me 2 C 6 H 3 (Xyl) 3, 2-Cl-6-MeC 6 H 3 4] and hydrazones H 2 NN CR 2 R 3 [R 2 , R 3 = Ph 5; R 2 , R 3 = C 6 H 4 (OMe-4) 6; R 2 /R 3 = 9-fluorenyl 7; R 2 = H, R 3 = C 6 H 4 (OH-2) 8] provided carbene complexes cis -[PdCl 2 {C(N(H)N CR 2 R 3 ) N(H)R 1 }(CNR 1 )] ( 9 – 24 ) in good (80–85%) yields. Complexes 9 – 24 showed high activity [yields up to 99%, and turnover numbers (TONs) up to 3.7 × 10 4 ] in the Sonogashira coupling of various aryl iodides with a range of substituted aromatic alkynes without the need of copper co-catalyst. The catalytic procedure runs at 80 °C for 1 h in EtOH using K 2 CO 3 as a base. No formation of homocoupling or acetylene decomposition products was observed. Designed copper-free Sonogashira system can also run at room temperature giving target products with yields up to 87% and TONs up to 87. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Conversions of non-isocyanide substrates under the catalytic action of metal-isocyanide complexes. • Broad range of (metal-isocyanide)-catalyzed reactions of organic substrates. • General overview of reaction routes, mechanisms, and driving forces. Abstract The catalytic applications of isocyanide metal systems (from early to late transition metals) for organic transformations were systematically reviewed, and the studied transformations are also classified by type regardless of the metal center. A broad range of catalytic reactions of organic substrates has been developed including reactions of alkenes and alkynes, functionalization of E–H and E–E to multiple bonds, alkyl- and aryl-halides activation, nucleophilic addition, electron transfer catalysis, and photochemical reactions. This report gives a general overview of reaction routes, mechanisms, and driving forces and highlights the potential of isocyanide metal species, drawing attention to emerging putative targets. [ABSTRACT FROM AUTHOR]

• A series of platinum(II) cyclometalated isocyanide complexes were prepared. • The X-ray diffraction data suggest the presence of (isocyano group)•••PtII interactions. • The isocyano nitrogen atom acts as a π-hole donor toward a d z 2-orbital of PtII atom. • Non-covalent interactions were studied by DFT calculations (NCI and QTAIM methods). • The CSD analysis verified more examples of (isocyano group)•••[ d9 -/ d8 -M] interactions. A series of platinum(II) isocyanide complexes [Pt(ppy)Cl(CNR)] (ppy = 2-phenylpyridinato-C2, N; R = Mes 1 , C 6 H 2 –2,6-Me 2 –4-Br 2 , C 6 H 2 –2-F-3-Cl-4-Br 3 , naphthalen-2-yl 4) were prepared and characterized by high resolution ESI-MS, 1D and 2D NMR, IR, UV–Vis absorption, and photoluminescence spectroscopies, as well as single-crystal X-ray diffraction. Analysis of X-ray diffraction data allowed us to identify (isocyano group)···PtII interactions where the nitrogen atom of the isocyano group acts as a π-hole donor toward a d z 2-orbital of PtII. The presence of these noncovalent interactions was confirmed by DFT calculations followed by NCI analysis and topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method). Processing of CSD data allowed verification of the contacts between coordinated isocyano moieties and various d9 and d8 - metal-centers (AuI, AuIII, AgI, PtII, PdII, NiII, RhI) to be performed. [Display omitted] [ABSTRACT FROM AUTHOR]