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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]

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]

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]

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]

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]