Synthesis and structure of trans-bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride and diacetate. Suzuki–Miyaura coupling of polybromoarenes with high catalytic turnover efficiencies

trans-Bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride has been shown to be an excellent catalyst for the multiple Suzuki–Miyaura coupling reactions of polybromoarenes to the corresponding fully substituted polyarylarenes. The reactions proceeded in excellent yields and with high turnover numbers. With 1,4-dibromobenzene the catalyst was found to be active for up to 13 consecutive cycles with a turnover number of 1260. The polyarylarenes were obtained in pure form after crystallization once without recourse to chromatographic purification. The single-crystal X-ray structures of the chloro (1) as well as the corresponding acetato (2) complexes are also reported and compared with the corresponding complexes of 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene as the ligand

p-Tolyl­methanaminium cyclo­hexane-1,2-diyl phosphate

In the title mol­ecular salt, C8H12N+·C6H10O4P−, the cation and anion are connected by N—H⋯O hydrogen bonds. The C atoms of the cyclo­hexane ring are disordered over two sets of sites in a 0.51 (4):0.49 (4) occupancy ratio to generate two superimposed chair conformations. One of the terminal phosphate O atoms is also disordered in a 0.62 (2):0.38 (2) ratio

1,1′-Binaphthyl-2,2′-diyl benzyl­phos­phoramidate

In the title compound, C27H20NO3P, the P atom exhibits a somewhat distorted PNO3 tetra­hedral geometry, with the O—P—O angle for the binaphthyl fragment being 102.82 (6)°. The dihedral angle between the naphthyl ring systems is 59.00 (2)°. In the crystal, inversion dimers linked by pairs of N—H⋯O hydrogen bonds generate R 2 2(8) loops

Synthesis and structural characterization of cis isomer of 1,2,3-triazol-5-ylidene based palladium complexes

A palladium complex (3) of abnormal N-Heterocyclic Carbene (NHC) namely, 4-(hydroxymethyl)-3-methyl-1-phenyl-1H-1,2,3-triazol-5-ylidene was prepared via silver carbene transmetalation method and characterized by spectroscopic and single crystal XRD data. Single crystal analysis revealed the structure of the complex 3 to be a cisisomer. The synthesis of palladium complex 6via silver carbene transmetalation method led to a mixture of cis–trans isomers. In this case trans isomer was formed as major product. We have reported earlier the synthesis and structural characterization of transisomer (trans-6). However, the presence of cis isomer was not recognized until the crude reaction mixture was recrystallized from acetonitrile. Pure cis isomer (cis-6) was obtained by washing the cis–trans mixture with acetonitrile followed by slow evaporation of acetonitrile solution at 35°C. Structure of cis (cis-6) isomer was unambiguously established by single crystal XRD data

Synthesis and structure of 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene palladium complexes and application in catalytic hydroarylation of alkynes

An abnormal or mesoionic N-heterocyclic carbene (NHC), namely 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene (Tz), formed from 1,4-diphenyl-3-methyl-1,2,3-triazolium iodide and silver oxide, gave the corresponding silver carbene complex. The transmetalation reaction of the silver carbene complex with PdCl2(CH3CN)2 gave a trans mononuclear complex, [(Tz)2PdCl2]. Reaction of the silver carbene complex with Pd(OAc)2 gave an acetate-bridged binuclear complex in which the palladium had undergone a C−H insertion at the ortho position of the phenyl group attached to the triazole nitrogen (1-position). The structures of these two complexes were established by single-crystal XRD data and spectroscopic data. The acetate complex was used as a catalyst for the stereoselective hydroarylation of alkynes

Bite-Angle-Regulated Coordination Geometries: Tetrahedral and Trigonal Bipyramidal in Ni(II) with Biphenyl-Appended (2-Pyridyl)alkylamine <i>N</i>,<i>N</i>′‑Bidentate Ligands

Two simple biphenyl-appended (2-pyridyl)­alkylamine <i>N</i>-bidentate ligands, L^e and L^m, having ethylene and methylene spacers between donor groups, with bite angles L^e ≈ 100° and L^m ≈ 80°, dictate pseudotetrahedral and trigonal-bipyramidal geometries in six high-spin Ni­(II)-halide complexes, [Ni­(L^e)­X₂] and [Ni­(L^m)₂X]­(ClO₄) (where X = Cl^–, Br^–, I^–), respectively. The structures in the solid state, determined using X-ray crystallography, and in solution, determined using spectroscopic methods (UV–vis–NIR and paramagnetic ¹H NMR), which complement each other, are described

Bite-Angle-Regulated Coordination Geometries: Tetrahedral and Trigonal Bipyramidal in Ni(II) with Biphenyl-Appended (2-Pyridyl)alkylamine <i>N</i>,<i>N</i>′‑Bidentate Ligands

Two simple biphenyl-appended (2-pyridyl)­alkylamine <i>N</i>-bidentate ligands, L^e and L^m, having ethylene and methylene spacers between donor groups, with bite angles L^e ≈ 100° and L^m ≈ 80°, dictate pseudotetrahedral and trigonal-bipyramidal geometries in six high-spin Ni­(II)-halide complexes, [Ni­(L^e)­X₂] and [Ni­(L^m)₂X]­(ClO₄) (where X = Cl^–, Br^–, I^–), respectively. The structures in the solid state, determined using X-ray crystallography, and in solution, determined using spectroscopic methods (UV–vis–NIR and paramagnetic ¹H NMR), which complement each other, are described

Toppled Molecular-Domino Sets by Self-Assembly of Self-assembly: The π‑Polymers

A series of designed binuclear palladium­(II)-based self-assemblies, [Pd₂­(en)₂­(<b>L</b>)₂]­(NO₃)₄, <b>1a</b>; [Pd₂­(tmeda)₂­(<b>L</b>)₂]­(NO₃)₄, <b>2a</b>; [Pd₂­(bpy)₂­(<b>L</b>)₂]­(NO₃)₄, <b>3a</b>; and [Pd₂­(phen)₂­(<b>L</b>)₂]­(NO₃)₄, <b>4a</b>, are synthesized. These complexes are obtained in good to excellent yields by equimolar combination of the nonchelating bidentate ligand bis­(4-pyridyl­methyl)­piperazine, <b>L</b>, with the corresponding <i>cis</i>-protected palladium­(II) component, that is, Pd­(N-N)­(NO₃)₂, under suitable reaction conditions. The <i>cis</i>-protecting N-N units used are ethylenediamine (en), tetramethylethylenediamine (tmeda), 2,2′-bipyridyl (bpy), and 1,10-phenanthroline (phen). The complexes <b>1a</b>–<b>4a</b> are well-characterized by ¹H NMR, H–H COSY, and HSQC, and the molecular compositions have been established by ESI-MS. The molecular structures are confirmed for the complexes [Pd₂­(tmeda)₂­(<b>L</b>)₂]­(ClO₄)₄, <b>2b</b>; [Pd₂­(bpy)₂­(<b>L</b>)₂]­(ClO₄)₄, <b>3b</b>; and [Pd₂­(phen)₂­(<b>L</b>)₂]­(NO₃)₄, <b>4a</b>, by the single-crystal X-ray diffraction technique. In the cases of the complexes <b>3b</b> and <b>4a</b>, the crystal packing diagrams display a unique one-dimensional predefined organization of molecules by intermolecular π–π interactions using the strategically located π-surfaces of the <i>cis</i>-protecting units. This organization resembles a set of toppled dominos. A given set exhibits further interactions with the neighboring sets in the packing pattern that are influenced by the nature of the N-N moiety, for example, bpy or phen. However, no such arrangement is observed in the case of the complex <b>2b</b> due to the lack of a π-surface at the <i>cis</i>-protecting moiety

A new class of MPV type reduction in group 4 alkoxide complexes of salicylaldiminato ligands: Efficient catalysts for the ROP of lactides, epoxides and polymerization of ethylene

New titanium (IV), zirconium (IV) and hafnium (IV) alkoxide complexes supported by the tridentate [O,N,N] salicylaldiminato ligands were synthesized in high yields and characterized by conventional spectroscopic techniques and single crystal X-ray analysis. The structural composition for some of these complexes was as a result of in situ intramolecular Meerwein–Ponndorf–Verley (MPV) type reduction of the imine moiety from the ligand, resulting in the formation of unexpected amido compounds. Theoretical calculations were performed at the DFT level to calculate the energy barrier for this reduction and rationalize the reactivity pattern. These complexes were found to be active towards the bulk ring opening polymerization (ROP) of rac-lactide (rac-LA), l-lactide (l-LA) and ε-caprolactone (CL), resulting in polymers with good number average molecular weight (Mn) and controlled molecular weight distributions (MWDs). The poly(lactic acid) (PLA) resulting from rac-LA were predominately heterotactic. Interestingly, these compounds were found to catalyze the ROP of epoxides such as rac-cyclohexene oxide (rac-CHO), rac-styrene oxide (rac-SO) and rac-propylene oxide (rac-PO) under solvent free condition. The kinetic and mechanistic studies associated with the polymerization have been included. In addition, these compounds were found to be useful as precatalysts for the polymerization of ethylene