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Bis-ADC complexes cis-[Pd{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 4a, Cy 4b, C6H4-4-F 4c) and cis-[Pt{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 5a, Cy 5b, C6H4-4-F 5c) were synthesized via the metal-mediated coupling of two isocyanide ligands in cis-[MCl2(CNR)2] (M = Pd, Pt; R = Xyl, Cy, C6H4-4-F) and 1,2-diaminobenzene. New compounds 4c and 5a–c were characterized by HR ESI+-MS, IR, and 1H, 13C{1H} and 195Pt{1H} NMR spectroscopy; the structures of 4a and 5a were elucidated by single-crystal X-ray diffraction. The stability of the ADC complexes in aqueous media (5 mM NaCl) was monitored by UV absorption spectroscopy, HR ESI+ mass spectrometry, and 195Pt{1H} NMR spectroscopy (for 5a). Molar conductivity measurements in MeOH (ΛM = 167–173 Ω−1 mol−1 cm2) indicate that, in this solvent, the ADC complexes exist as dicationic species of [A][Q]2 type. The ADC complexes binding to CT DNA was investigated by means of spectroscopic and hydrodynamic techniques including UV absorption and circular dichroism spectroscopy, fluorescence spectroscopy, low-gradient viscometry, flow birefringence, and AFM imaging. As a result, complexes 4a and 5a were shown to bind double-stranded DNA predominantly via the formation of monofunctional adducts in the major groove of the macromolecule. Binding of the ADC complexes also provokes the formation of a large number of intermolecular DNA–DNA contacts in solution. The antiproliferative activity of all prepared ADC complexes 4a–c and 5a–c was evaluated in vitro against three human carcinoma cell lines (HT-29, MDA-MB-231, and MCF-7) and two non-tumorigenic cell lines (L929 and RC-124) and compared to that of cisplatin. Among the compounds studied, complexes 4a and 5a appeared to be the most active species with IC50 values in MCF-7 cells of about 10 μM. [ABSTRACT FROM AUTHOR]

The dihalomethanes CH2X2 (X=Cl, Br, I) were co‐crystallized with the isocyanide complexes trans‐[MXM2(CNC6H4‐4‐XC)2] (M=Pd, Pt; XM=Br, I; XC=F, Cl, Br) to give an extended series comprising 15 X‐ray structures of isostructural adducts featuring 1D metal‐involving hexagon‐like arrays. In these structures, CH2X2 behave as bent bifunctional XB/XB‐donating building blocks, whereas trans‐[MXM2(CNC6H4‐4‐XC)2] act as a linear XB/XB acceptors. Results of DFT calculations indicate that all XCH2–X⋅⋅⋅XM–M contacts are typical noncovalent interactions with estimated strengths in the range of 1.3–3.2 kcal mol−1. A CCDC search reveals that hexagon‐like arrays are rather common but previously overlooked structural motives for adducts of trans‐bis(halide) complexes and halomethanes. [ABSTRACT FROM AUTHOR]

Reaction of [Ir(μ-Cl)(ppy)2]2 (1) with 4 equivs of CNC6H4X (X = F 2a, Cl 2b, Br 2c, I 2d) in the presence of 2 equivs of AgOTf in dichloromethane at 20–25 °C furnished the bisisocyanide complexes [Ir(ppy)2(CNC6H4X)2](OTf) ([3a–d](OTf); 72–87%). Reaction of [3a–d](OTf) with an excess of gaseous ammonia at room temperature gave the bisdiaminocarbene species [Ir(ppy)2{C(NH2)NHC6H4X}2](OTf) [5a–d](OTf) (73–83%); the two-step addition proceeds through an intermediate formation of appropriate monocarbene complexes [4a–d](OTf). Further reaction of [5a–d](OTf) with an excess of gaseous ammonia at 50 °C led to the cleavage of one diaminocarbene ligand to the cyanide ligand in [Ir(ppy)2(CN){C(NH2)NHC6H4X}] (6a–d) and this transformation is accompanied with the elimination of a substituted aniline. Treatment of [5a–d](OTf) with N(CH2CH2OH)3 at 50 °C resulted in the cleavage of the diaminocarbene ligand to the isocyanide and uncomplexed NH3; isocyanide remains bound to the iridium(iii) center in [Ir(ppy)2{C(NH2)NHC6H4X}(CNC6H4X)](OTf) (4a–d). All isolated compounds were characterized by elemental analyses (C, H, N), molar conductivity measurements, TG/DTA, HRESI+/−-MS, FTIR, 1D (1H, 13C{1H}, 19F{1H}) and 2D (1H,1H-COSY, 1H,13C-HMQC/1H,13C-HSQC, 1H,13C-HMBC) NMR, and also by X-ray diffraction (for the bisisocyanide 3, the diaminocarbene/isocyanide 4, the bisdiaminocarbene 5, and the diaminocarbene/cyanide 6 type complexes). [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]

The neutral cyclometalated iridium(III) complexes [Ir(ppy)2Cl(NCNR2)] [ppy=2‐phenylpyridinato‐C2,N, R=Me 3 a, Et 3 b, 1/2 C5H103 c] were prepared via the reaction of the chloro‐bridged dimer [Ir2(ppy)4(μ‐Cl)2] (1) with corresponding dialkylcyanamides NCNR2 (2 a–c) and 3 a–c were isolated in 74–85% yields. The cationic cyclometalated iridium(III) complex [Ir(ppy)2(NCNMe2)2](OTf) (4) was obtained by replacement of chloride ligands with NCNMe2 in 1 in the presence of AgOTf. UV/Vis absorption and emission properties of 3 a−c and 4 were studied; these complexes exhibit luminescence in the solid state upon photoexcitation (340 nm, 77 K). The characteristic feature of the X‐ray structures of 3 a–c is a deviation of the fragment Ir–N–C from linearity by 13.8(5)–22.8(3)°. Quantum chemical DFT calculations and topological analysis of the electron density distribution within the formalism of Bader's theory (AIM method) performed for 3 a–c demonstrated that the Ir–N–C fragments in the optimized equilibrium structures of [Ir(ppy)2Cl(NCNR2)] significantly deviate from the linearity (by 19.8–30.7°) and indicated that the Ir–N contacts between the metal centers and dialkylcyanamide ligands are relatively weak (24–30 kcal/mol) and have a closed‐shell dative interactions character. The charge decomposition analysis (CDA) shows existence of {M}←L donation with almost negligible contribution of the {M}→L back‐donation in 3 a–c. Thee neutral cyclometalated iridium(III) complexes [Ir(ppy)2Cl(NCNR2)] and one cationic cyclometalated iridium(III) complex [Ir(ppy)2(NCNMe2)2](OTf) were prepared for the first time. X‐ray study revealed deviation of the fragment Ir–N–C(dialkylcyanamide) from linearity by 13.8(5)–22.8(3)° in the structures of [Ir(ppy)2Cl(NCNR2)]. Structural features of Ir–N(dialkylcyanamide) coordination bonds were investigated theoretically. [ABSTRACT FROM AUTHOR]

New cyclometalated dinuclear platinum(II) complex bearing bridged 4,6-dimethylpyrimidine-2(1H)-thiolate (μ-C6H7N2S-κN,S) ligands, [{Pt(ppy)(μ-C6H7N2S-κN,S)}2] (3) (ppy=(2-phenylpyridinato-C2,N)) was prepared via the reaction of chloro-bridged dimer [{Pt(ppy)Cl}2] with 4,6-dimethylpyrimidine-2(1H)-thione (C6H8N2S) in the presence of t-BuOK. The complex holds dinuclear frameworks with short Pt(II)···Pt(II) distance (2.8877(3) Å), and exhibit red intense luminescence from the triplet metal-metal-to-ligand charge-transfer at 697 nm in CH2Cl2 solution and at 649 nm in solid state at RT. Single crystal XRD analysis reveals the metallophilic interactions Pt···Pt with significant covalent contribution in the structure of 3 which were studied by quasi-relativistic and relativistic DFT calculations (viz., M06/MWB60(Pt) and 6-311+G* (other atoms); M06/DZP-DKH levels of theory) and topological analysis of the electron density distribution within the framework of Bader's theory (QTAIM method). Estimated strength of the Pt···Pt contact is 8.1–12.2 kcal/mol and it is mostly determined by crystal packing effects and weak attractive interactions between the adjacent metal centers due to overlapping of their dz2 and pz orbitals. An organic light-emitting diode based on this complex showed red electroluminescence with maximal luminance of 115 cd/m2 and current efficiency of 2.45 cd/A at this luminance. [ABSTRACT FROM AUTHOR]

Abstract: In the current study, we evaluated the solubility of a number of organometallic species and showed that it is noticeably improved in diiodomethane when compared to other haloalkane solvents. The better solvation properties of CH2I2 were associated with the substantially better σ‐hole‐donating ability of this solvent, which results in the formation of uniquely strong solvent–(metal complex) halogen bonding. The strength of the halogen bonding is attenuated by the introduction of additional halogen atoms in the organometallic species owing to the competitive formation of more favourable intermolecular complex–complex halogen bonding. The exceptional solvation properties of diiodomethane and its inertness towards organometallic species make this solvent a good candidate for NMR studies, in particular, for the acquisition of spectra of insensitive spins. [ABSTRACT FROM AUTHOR]

A series of platinum complexes featuring phosphine and isocyanide ligands [PtX2(PPh3)(CNCy)] (X = Cl, Br, and I) as well as their parent phosphine [PtX2(PPh3)2] and isocyanide [PtX2(CNCy)2] analogues have been prepared and evaluated as catalysts for the photocatalytic hydrosilylation of alkynes. Under violet light irradiation (λmax = 400 nm), phosphine–isocyanides complexes [PtX2(PPh3)(CNCy)] gave high yields of silylated products (product yield up to 99%, TONs up to 1.98 × 103). The blue light irradiation (λmax = 450 nm) was more suitable for the parent phosphine complexes [PtX2(PPh3)2], which showed comparable efficiency (product yield up to 99%, TON up to 1.98 × 103), while isocyanide complexes [PtX2(CNCy)2] were not active. [ABSTRACT FROM AUTHOR]

Solvent-rich dichloromethane solvate of cis-[Ir(bptz)2(CNXyl)2]BF4 (3, bptz is cyclometallated 4-(4-bromophenyl)-2-methylthiazole) is prepared via the reaction of chloro-bridged dimer [Ir(bptz)2(μ-Cl)]2 (1) with 2,6-dimethylphenyl isocyanide (CNXyl, 2) and AgBF4. Single crystal X-ray diffraction on the 3 · 3 1/4CH2Cl2 solvate showed the presence of numerous non-covalent interactions, including the C-S…F-B chalogen bonding (ChB), the C-Br…Br-C, C-Cl…Br-C, and C-Cl…S(C)-C halogen bonding (XB), and the C-H…F-B hydrogen bonding (HB). The nature of these short contacts was explored both experimentally by single-crystal X-ray diffraction and theoretically by DFT calculations on the empirical geometries followed by Bader's topological electron density distribution analysis. The evaluated energies of XBs and ChBs are in range 1.3-2.2 kcal/mol indicating the noncovalent nature of the contacts. [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]

Reaction of [AuCl3(CNR1)] (R1 = Xyl, Cy, (S)-CHMePh) with amines unexpectedly proceeds via the redox pathway giving gold(i)–isocyanides and imines, while the addition of benzophenone hydrazone to the isocyanide ligand in [AuCl3(CNR1)] at RT leads to short-lived gold(iii) acyclic diaminocarbene complexes [AuCl3{C(NHNCPh2)NHR1}]. [ABSTRACT FROM AUTHOR]

Weak intermolecular non-covalent H•••Cl- interactions in the solid chelated palladium(II)-diaminocarbene complex cis-[PdCl(CNXyl){C(NHXyl) = NHC6H2Me2NH2}] Cl (3; Xyl = 2,6-Me2C6H3) were studied by XRD followed by appropriate DFT calculations. The N-H•••Cl contacts for both NH groups in the carbene moiety are different (N1-H•••Cl2 3.5258(19), N2-H•••Cl2 3.0797(17) Å). The DFT calculations and topological analysis of the electron density distribution within the formalism of Bader's theory (QTAIM method) were performed for a model cluster of the carbene complex 3. The theoretical data confirmed that the strength of intermolecular HB H•••Cl- is different for two NH-protons of the carbene fragment. The influence of crystal packing effects on the formation of hydrogen bonds in the cluster of 3 is noticeable. [ABSTRACT FROM AUTHOR]

Palladium(II) diaminocarbene complexes trans -[PdI 2 (CNXyl){C(NHXyl) = NHNHC(O)R}] ( 4a – h ) bearing iodide anionic ligands were synthesised via ligands exchange from the corresponding chloride species cis -[PdCl 2 (CNXyl){C(NHXyl) NHNHC(O)R}] ( 3a – h ) and KI in an acetone solution. Complexes 4a – h were isolated and characterized by HRESI + -MS, IR, 1 H and 13 C{ 1 H} NMR spectroscopies, and single-crystal X-ray diffraction (in the case of complexes 4a – e , 4g and 4h ). The entire synthesised compounds exhibit slightly distorted square planar geometry around the metal centre. The carbene and isocyanide ligands in the synthesised iodide complexes are in trans -position each other in contrast to the starting cis -dichloride species. [ABSTRACT FROM AUTHOR]

The dihalomethane-halide H2C(X)-X···X- (X = Cl, Br) halogen bonding was detected in a series of the cis-[PdX(CNCy){C(NHCy) NHC6H2Me2NH2}]X•CH2X2 (X = Cl, Br) associates by single-crystal XRD followed by DFT calculations. Although ESP calculations demonstrated that the σ-hole of dichloromethane is the smallest among all halomethane solvents (the maximum electrostatic potential is only 2.6 kcal/mol), the theoretical DFT calculations followed by Bader's QTAIM analysis (M06/DZP-DKH level of theory) confirmed the H2C(X)-X···X- halogen bond in both the solid-state and gas-phase optimized geometries. The estimated bonding energy in H2C(X)-X···X- is in the 1.9-2.8 kcal/mol range. [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]

The reaction of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with various 1,3-thiazol- and 1,3,4-thiadiazol-2-amines in chloroform gives a mixture of two regioisomeric binuclear diaminocarbene complexes. For 1,3-thiazol-2-amines the isomeric ratio depends on the reaction conditions and kinetically (KRs) or thermodynamically (TRs) controlled regioisomers were obtained at room temperature and on heating, respectively. In CHCl3 solutions, the isomers are subject to reversible isomerization accompanied by the cleavage of Pd–N and C–N bonds in the carbene fragment XylNCN(R)Xyl. Results of DFT calculations followed by the topological analysis of the electron density distribution within the formalism of Bader’s theory (AIM method) reveal that in CHCl3 solution the relative stability of the regioisomers (ΔGexp = 1.2 kcal/mol; ΔGcalcd = 3.2 kcal/mol) is determined by the energy difference between two types of the intramolecular chalcogen bonds, viz. S···Cl in KRs (2.8–3.0 kcal/mol) and S···N in TRs (4.6–5.3 kcal/mol). In the case of the 1,3,4-thiadiazol-2-amines, the regioisomers are formed in approximately equal amounts and, accordingly, the energy difference between these species is only 0.1 kcal/mol in terms of ΔGexp (ΔGcalcd = 2.1 kcal/mol). The regioisomers were characterized by elemental analyses (C, H, N), HRESI+-MS and FTIR, 1D (1H, 13C{1H}) and 2D (1H,1H-COSY, 1H,1H-NOESY, 1H,13C-HSQC, 1H,13C-HMBC) NMR spectroscopies, and structures of six complexes (three KRs and three TRs) were elucidated by 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]

Reaction of organoiridium(III)-2-phenylpyridine complex, [Ir(ppy) 2 ( μ -Cl)] 2 (ppy = 2-phenylpyridinato- C 2 , N ), with 4-(2-bromophenyl)-1,2,3-thiodiazole (X) or 4-(2-bromophenyl)-1,2,3-selenadiazole (Y) in CH 2 Cl 2 yields to [Ir(ppy) 2 Cl(X)]·CH 2 Cl 2 ( 1 ) or [Ir(ppy) 2 Cl(Y)] ( 2 ), respectively. Both compounds were characterized by characterized by elemental analyses (C, H, N), HRESI + -MS, FTIR, and studied by single-crystal X-ray diffraction. The coordination environment of the central iridium(III) has a distorted octahedral geometry, four sites being occupied by two (ppy) − , which chelates in the C,N fashion, while the two other sites are filled with the Cl − and X (or Y) ligands. The intramolecular S ··· N and Se ··· Cl types of chalcogen bonds were found in the structures of 1 and 2 , respectively. Compound 1 is also present intramolecular pnicogen bonding and intermolecular halogen bonding (between CH 2 Cl 2 molecules) with the short N ··· Br (3.160 Å) and Cl ··· Cl (2.187 Å) distances. The crystal structures in 1 and 2 are stabilized by medium-strong intermolecular hydrogen bonding interactions. [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]

The reaction between the equimolar amounts of cis-[PdCl2(CNR¹)2] (R¹ = cyclohexyl (Cy) (1), tBu (2)) and the carbohydrazides R²CONHNH2 (R² = Ph (5), 4-ClC6H4 (6), 3-NO2C6H4 (7), 4-NO2C6H4 (8), 4-CH3C6H4 (9), 3,4-(MeO)2C6H3 (10), naphth-1-yl (11), fur-2-yl (12), 4-NO2C6H4CH2 (13), Cy (14), 1-(4-fluorophenyl)-5-oxopyrrolidin-3-yl (15), (pyrrolidin-1-yl)C(O) (16)) proceeds in refluxing CHCl3 for ca. 4 h. A subsequent workup provided the aminocarbene species cis-[PdCl2{C(NHNHC(O)R²)═N(H)R¹}(CNR¹)] (18-33) in good to excellent (80-95%) isolated yields. The coupling of equimolar amounts of cis-[PdCl2(CNR¹)2] (R¹ = Cy (1), tBu (2), 2,6-Me2C6H3 (Xyl) (3), 2-Cl-6-MeC6H3 (4)) and PhSO2NHNH2 (17) occurs similarly and affords the aminocarbenes cis-[PdCl2{C(NHNHS(O)2Ph)═N(H)R¹}(CNR¹)] (34-37; 60-90%). Complexes 18-37 were characterized by elemental analyses (C, H, N), ESI+-MS, IR, and 1D (¹H, 13C{¹H}) and 2D (¹H,¹H-COSY, ¹H,13C-HMQC/¹H,13C-HSQC, ¹H,13C-HMBC) NMR spectroscopy, as well as by X-ray diffraction for three species (34, 37, and 38). The catalytic properties of 18-37 in Suzuki-Miyaura cross-coupling in aqueous medium were evaluated, and 18-37 showed remarkable activity (0.001-0.01 mol % catalyst loading). The scope of the catalytic process covers sterically unhindered and sterically demanding aryl bromides and aryl iodides bearing donor and/or acceptor substituents and activated aryl chlorides. All organohalides reacted with a range of arylboronic acids at 80 °C within 2 h (100 °C and 3 h for the chlorides), providing target diaryls in yields up to 99% and with maximum TONs of 9.9 × 10³ (for aryl iodides), 4.7 × 104 (for aryl bromides), and 9.2 × 10³ (for aryl chlorides). [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]

Hydrolytically stable PdII and PtII complexes supported by acyclic diaminocarbene ligands represent a novel class of structural organometallic anticancer agents exhibiting nanomolar antiproliferative activity in a panel of cancer cell lines (IC50 0.07–0.81 μM) and up to 300‐fold selectivity for cancer cells over normal primary fibroblasts. The lead drug candidate was 300 times more potent than cisplatin in vitro and showed higher efficacy in reducing the growth of aggressive MDA‐MB‐231 xenograft tumors in mice. [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 isocyanide trans‐[PdBr2(CNC6H4‐4‐X′)2] (X′=Br, I) and nitrile trans‐[PtX2(NCC6H4‐4‐X′)2] (X/X′=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is determined by hitherto unreported four‐center nodes formed by cyclic halogen bonding. Each node is built up by four Type II C−X′⋅⋅⋅X−M halogen‐bonding contacts and include one Type I M−X⋅⋅⋅X−M interaction, thus giving the rhombic‐like structure. These nodes serve as supramolecular synthons to form 2D layers or double chains of molecules linked by a halogen bond. Results of DFT calculations indicate that all contacts within the nodes are typical noncovalent interactions with the estimated strengths in the range 0.6–2.9 kcal mol−1. [ABSTRACT FROM AUTHOR]

The PtII isocyanide complex [Pt(ppy)Cl(CNC6H4-C≡C-Ph)] (1, Hppy=2-phenylpyridine) was co-crystallized with 1,4-diiodotetrafluorobenzene (1,4-DITFB), yielding 1·½(1,4-DITFB) adduct. The I···Cl halogen-bonding and π-π-stacking interactions combined with the rare π-hole(isocyano group)⋅⋅⋅dz2[PtII] interactions were identified via analysis of X-ray diffraction data of the co-crystals. These two types of structure-determining interactions supplemented each other, and the system of I⋯Cl and π-hole(isocyano group)⋅⋅⋅dz2[PtII] contacts achieved a 1D extended ladder-type architecture. The density functional theory calculations, employing a set of computational tools, verified the role of I⋯Cl and π-hole(isocyano group)⋅⋅⋅dz2[PtII] noncovalent bonds in the spectrum of noncovalent forces. The solid-state photophysical study revealed an amplification of luminescence intensity in the co-crystals, which is attributed to the suppression of the nonradiative relaxation pathways due to an increase in the rigidity of the chromophore center. [ABSTRACT FROM AUTHOR]

Inspection of the X‐ray structures of the newly prepared trans‐[MII(CNXyl)2(DAPT)2]Cl(BF4) (M=Pd, Pt; Xyl=2,6‐Me2C6H3; DAPT=4,6‐diaminopyrimidine‐2(1H)‐thione) complexes and the appropriate Hirshfeld molecular surface analysis allowed the recognition of the previously unknown π‐hole⋅⋅⋅metal interactions between a ligated isocyano group (acting as a π‐hole donor) and the positively charged d8‐PtII and d8‐PdII metal centers (acting as nucleophiles); this is the first identification of π‐hole⋅⋅⋅metal interactions with triple‐bond species. Results of DFT calculations followed by the topological analysis of the electron density distribution within the framework of Bader's theory (quantum theory of atoms in molecules, QTAIM) confirmed the presence of these contacts. The electrostatic surface potential calculations indicated that π‐hole⋅⋅⋅metal contacts are formed upon interaction between the electrophilic isocyano C atom (π‐hole donor) and the nucleophilic dz2 orbital of the metal centers, which act as π‐hole acceptors. Available CCDC data were processed from the perspective of the π‐hole⋅⋅⋅metal interactions with isocyanide ligands, and their analysis disclosed the role of metal nucleophilicity in the corresponding π‐hole acceptor ability. [ABSTRACT FROM AUTHOR]

A novel series of cyclometalated platinum(II) complexes bearing acyclic diaminocarbene (ADC) ancillary ligands were designed and prepared. Their photophysical properties were systematically studied through experimental and theoretical investigations. All complexes exhibit green phosphorescence with a quantum efficiency of up to 45% in 2 wt% doped PMMA film at room temperature. The complexes are used as light-emitting dopants for organic light-emitting diode (OLED) fabrication. The devices displayed a green emission with a maximum current efficiency of 2.9 cd A−1 and a luminance of 2700 cd m−2. These results show that these cyclometalated platinum(II) complexes can be used as efficient green emitting components of OLED devices. [ABSTRACT FROM AUTHOR]

Syntheses and characterizations of novel phosphaheterocycles, 1-phenyl-4,4-dimethyl-1,4-dihydrophosphinoline (2a) and 1-phenyl-2-bromo-4,4-dimethyl-1,4-dihydrophosphinoline (2b), and their complexes with Pd(ii) and Pt(ii) are described. Reduction of 1-phenyl-4,4-dimethyl-1,4-dihydrophosphinoline 1-oxide (1a) and 1-phenyl-2-bromo-4,4-dimethyl-1,4-dihydrophosphinoline 1-oxide (1b) using trichlorosilane in refluxing benzene gave the target phosphines in a yield of 83–87%. Reactions of phosphines with acetonitrile complexes of Pd(ii) (3) and Pt(ii) (4) yielded bis(phosphine) species [MCl2L2] (5–8). Complexes 5–8 were characterized by 1H, 13C, 31P, 195Pt NMR and HRMS. The structures of all these new complexes were determined with single crystal X-ray diffraction. The configuration of the complexes in a CDCl3 solution was investigated via comparing of 31P NMR data in solution and solid state. [ABSTRACT FROM AUTHOR]

Invited for the cover of this issue are Tatiyana Serebryanskaya, Mikhail Kinzhalov and co‐workers at St. Petersburg State University, the Research Institute for Physical Chemical Problems, Belarusian State University, Togliatti State University and Blokhin National Medical Research Center of Oncology. The image depicts the shield of Pallas Athena with the structure of a palladium carbene complex that protects against triple‐negative breast cancer. Read the full text of the article at 10.1002/chem.202400101. [ABSTRACT FROM AUTHOR]

The article titled "Metal-(Acyclic Diaminocarbene) Complexes Demonstrate Nanomolar Antiproliferative Activity against Triple-Negative Breast Cancer" discusses the use of a palladium compound to target aggressive tumors while sparing normal cells and tissues. The authors draw inspiration from the protective figure of Pallas Athena, which symbolizes the original meaning of the word "palladium." The research article provides more detailed information on this topic and can be accessed using the provided DOI. [Extracted from the article]

Palladium(II) and platinum(II) complexes featuring metalla-N-heterocyclic carbenes (7–12) were synthesised via metal-mediated coupling between equimolar cis-[MCl2(CNR)2] (R = 2,6-Me2C6H3 (Xyl), 2,4,6-Me3C6H3 (Mes)) and 2-aminopyridine or 2-aminopyrazine. Thiocyanate complexes 13–18 with two thiocyanate ligands were obtained through the ligand exchange in the parent compounds 7–12 with NH4CNS in acetone/CH2Cl2. Complexes 7–18 were isolated and characterised by HRESI+-MS, IR, 1H and 13C{1H} NMR spectroscopy and single-crystal X-ray diffraction (in the case of 11, 16, and 18). The UV-vis properties of 7–18 and the electrochemical properties of 7–12 were also evaluated. To study the electronic structure and bonding nature in the new compounds, the quantum theory of atoms in molecules (QTAIM) and Mayer bond order analysis together with the extended transition state with the natural orbitals for chemical valence (ETS-NOCV) method, were used. X-ray diffraction studies and theoretical considerations indicate that the thiocyanate derivatives 16 and 18 form supramolecular dimers by two symmetrical pairs M1⋯C5 and S1⋯C2 with short intermolecular contacts between an electron-rich MII-center and thiocyanate ligand on the one side and the electron-poor π-system of an azaheterocyclic ring on the other side. Representative carbenes 8, 11 and 12 were evaluated as photocatalysts for the hydrosilylation of diphenylacetylene with triethylsilane giving 1,2-(diphenylvinyl)triethylsilane in 98% yield under visible light irradiation (blue light, 445 nm). [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]

Phosphorescent PtII-based cyclometalated complexes co-crystallise with bromo- and iodosubstituted perfluorinated arenes to give 1 : 1 adducts. X-FArenes in these co-crystals act as both σh and πh donors forming co-operative C–X⋯Cl–Pt XBs and πh⋯dz2[PtII] contacts. The solid-state photophysical study revealed up to a 2-fold luminescence quantum yield increase upon co-crystallisation due to the formation of these co-operative noncovalent interactions. [ABSTRACT FROM AUTHOR]

• PdCl 2 (CNXyl) 2 reacts with benzothiazol-2-amines giving two binuclear complexes. • Both binuclear Pd complexes are regioisomers and able to interconvert. • Electron-withdrawing substituents and polar solvents accelerate isomerization. • Rate-determining step is the C N bond breaking in the diaminocarbene moiety. A series of binuclear PdII carbene complexes were synthesized via the treatment of cis -[PdCl 2 (CNXyl) 2 ] (1) with benzo-1,3-thiazol-2-amines (2 – 6) and structurally characterized. In every case the reaction leads to the mixture of two regioisomers, which are able to interconvert. The study of the regioisomerization of the binuclear diaminocarbene species showed that it is a first-order reaction, that is, it occurs intramolecularly, and was analyzed with the Hammett function. Electron-withdrawing substituents in the benzothiazole moiety of the complexes as well as increasing the solvent polarity accelerate the reaction. The solvent donor strength correlates less well with the isomerization rates. Based on the obtained activation parameters the studied regioisomerization could be defined as the interchange/dissociative process type. A combined approach including kinetic and mass spectrometric studies allowed the conclusion that the rate-determining step of the isomerization is breaking the carbon–nitrogen bond in the carbene fragment of the binuclear complex. [ABSTRACT FROM AUTHOR]

Cover Feature: Four-Center Nodes: Supramolecular Synthons Based on Cyclic Halogen Bonding (Chem. Eur. J. 60/2019) B XB-based nodes as supramolecular synthons b : The X'-aryl isocyanide I trans i -[PdBr SB 2 sb (CNC SB 6 sb H SB 4 sb -4-X') SB 2 sb ] (X'=Br, I) and nitrile I trans i -[PtX SB 2 sb (NCC SB 6 sb H SB 4 sb -4-X') SB 2 sb ] (X/X'=Cl/Cl, Cl/Br, Br/Cl, Br/Br) complexes exhibit similar structural motif in the solid state, which is determined by hitherto unreported four-center nodes formed by cyclic halogen bonding. Crystal engineering, four-center nodes, halogen bonding, noncovalent interactions, supramolecular synthons. [Extracted from the article]

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]

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]