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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]

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]

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]

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]

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]

• 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]