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Borrowing hydrogenation (BH) is a powerful methodology, which is widely adopted for the N-alkylation of amines with alcohols using homogeneous molecular catalysts. To explore the chemistry, herein two novel monomeric Ru(II) complexes [(η6-p-cymene)Ru(L1)Cl2] [Ru-1] bearing 4-trifluromethoxyaniline (L1) and [(η6-p-cymene)Ru(L2)Cl] [Ru-2] bearing quinaldic acid (L2) were synthesized and their structural features were revealed by utilizing analytical and spectroscopic methods like FTIR, 1H and 13C NMR, ESI-MS, and elemental analysis. The lattice structures of both [Ru-1] and [Ru-2] were elucidated by Single Crystal XRD (SC-XRD). Also, aniline-based complex [Ru-3] was synthesized according to the literature and used for comparison. The catalytic efficacy of [Ru-(1–3)] was examined for N-alkylation of amines utilizing alcohols as alkylating agents in benign and solvent-free conditions. The catalytic performance was monitored by GC–MS and HPLC analyses. The primary amine-based (L1) complex [Ru-1] showed a very impressive and efficient conversion of 96%, whereas –N, O donor ligand based (L2) complex [Ru-2] and the unsubstituted aniline based [Ru-3] were able to achieve 25% and 90% conversion, respectively in similar reaction conditions. This drastic variation in catalytic performance was observed due to the co-operative effect of –NH2 in [Ru-1] and [Ru-3]. Metal–ligand cooperation (MLC) in both the complexes stabilizes the intermediate transition state and also the electron deficient Ru(II) center in [Ru-1] has very good binding affinity towards the substrate, which leads to superior catalytic conversion with [Ru-1] compared to [Ru-2] and [Ru-3]. [ABSTRACT FROM AUTHOR]

The reactivity of a bicyclic (alkyl)(amino)carbene (BICAAC) towards different boranes has been examined in the present work. The reactions with boranes BX3·SMe2 (X = H, Cl, Br), BF3·OEt2 and BCl3 yield Lewis adducts [BICAAC·BH3] (1), [BICAAC·BHCl2] (2), [BICAAC·BH2Cl] (3), [BICAAC·BF3] (4), [BICAAC·BCl3] (5) and [BICAAC·BBr3] (6) respectively, whereas more hydridic boranes, 9-borabicyclo[3.3.1]nonane (9-BBN) and catecholborane (HBcat), enable the insertion of the carbene carbon into the B–H bond to form [BICAAC(H)-(9-BBN)] (7) and [BICAAC(H)-Bcat] (8). These complexes are the first examples of BICAAC–boron compounds and have been characterized using IR, multinuclear NMR spectroscopy, HRMS spectrometry and single crystal X-ray diffraction. Computational analyses were also performed to gain insight into the mechanism of B–H bond activation and adduct formation. Furthermore, the reactions of the BICAAC with boranes have been compared with the known reactions of CAACs and NHCs. [ABSTRACT FROM AUTHOR]

The first examples of group 13 element containing pyridinophanes have been assembled using heteroatom N–E–N bridges (E = B, Al). The presence of B and Al as acceptor atoms in the bridges and their coordination with pyridine nitrogen has a very strong influence on the conformational rigidity of the pyridinophanes. [ABSTRACT FROM AUTHOR]

A mononuclear iron(II) complex, [Fe(phen)3]Cl2 ( 1) (phen =1,10-phenanthroline), has been synthesized in crystalline phase and characterized using various spectroscopic techniques including single crystal X-ray diffraction. Crystal structure analysis revealed that 1 crystallizes in a monoclinic system with C2/m space group. Complex 1 acts as a functional model for a biomimetic catalyst promoting the aerobic oxidation of 3,5-di- tert-butylcatechol (3,5-DTBC) through radical pathways with a significant turnover number ( kcat =3.55 × 103 h−1) and exhibits catechol dioxygenase activity towards the same 3,5-DTBC substrate at room temperature in oxygen-saturated ethanol medium. The existence of an isobestic point at 610 nm from spectrophotometric data indicates the presence of Fe3+ −3,5-DTBC adduct favouring an enzyme-substrate binding phenomenon. Upon stoichiometric addition of 3,5-DTBC pretreated with two equivalents of triethylamine to the iron complex, two catecholate-to-iron(III) ligand-to-metal bands (575 and 721 nm) are observed and the in situ generated catecholate reacts with dioxygen ( kobs =9.89 × 10−4 min−1) in ethanol medium to afford exclusively intradiol cleavage products along with a small amount of benzoquinone, and a small amount of extradiol cleavage products, which provide substantial evidence for a mechanism. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The azobenzenes, known for theirvarious importance in the industry,have been chosen as model compounds to understand the role of weakinteractions involving the C–X (X = F, Cl, and Br) bond usingsingle-crystal X-ray diffraction technique, especially in the absenceof other stronger intermolecular forces such as hydrogen bonds. Thefluorinated compounds have been found to pack in the lattice by utilizingC–H···F hydrogen bonds, whereas the chlorinatedand brominated analogues have been found to prefer C–X···X–C,C–X···π, and π···πinteractions while packing in the lattice. The stabilization energyoffered by the C–H···F hydrogen bonds and theC–X···X–C interactions have been estimatedby computational methods using Gaussian 09, and the topological propertieshave been determined by using the AIM2000 package. The lattice energydecomposition has been done using semiclassical density sums (SCDS)PIXEL method. Our studies indicate that the stabilization energy offeredby each C–H···F hydrogen bond lies in the rangefrom −0.8 to −1.0 kcal/mol, while that for the C–X···X–Cinteraction has been found to be −0.35 kcal/mol for the X =Cl interaction and −0.73 kcal/mol for the X = Br interaction.Further, the analysis of these interaction by atoms in molecules (AIM)theory indicates that the electron densities (ρc)at the bond critical points (BCP) for C–H···Fand C–X···X–C (X = Cl and Br), calculatedusing the AIM2000 package, are small (<0.007 eÅ–3), and the values of Laplacian (∇2ρc) are positive. This indicates that these interactions are of thehydrogen bond type. A detailed study of these interactions by experimentaland computational methods has been described in the manuscript. [ABSTRACT FROM AUTHOR]

Abstract A non-heme tetra-iron cluster, [Fe 4 III(μ- O) 2 (μ- OAc) 6 (2,2′-bpy) 2 (H 2 O) 2 ](NO 3 −)(OH−) (1), [OAc = acetate; 2,2′-bpy = 2,2′-bipyridine] containing oxido- and acetato-bridges was synthesized and structurally characterized by different spectroscopic methods including single crystal X-ray diffraction studies. X-ray crystal structure analysis of 1 revealed that tetra-iron complex was crystallized in monoclinic system with C 2/ c space group. Each of the Fe centres in 1 was found to exist in octahedral geometry and interconnected by oxido- and acetato-bridges. Bond valence sum (BVS) calculation recommended the existence of iron centres in +3 oxidation state. Variable temperature magnetic measurement authenticated the dominating antiferromagnetic ordering among the iron centres in the solid state of 1. This tetra-iron cluster was also evaluated as an efficient catalytic system towards the oxidation of both linear & cyclic alkanes without production of primary C H bond oxidation products. Oxidation of secondary C H bonds attested the formation of both the corresponding alcohols & ketones in 27–900 TONs. The tetra-iron catalytic system with Alcohol/Ketone values 0.2–1.7 indicated the involvement of freely diffusing carbon-centered radicals rather than metal based oxidant. Graphical abstract This paper represents synthesis of a new oxido-acetato-bridged tetra-iron(III) complex, [Fe 4 III(μ- O) 2 (μ- OAc) 6 (2,2′-bpy) 2 (H 2 O) 2 ](NO 3 −)(OH−) which displays excellent catalytic activity towards C H activation property based on carbon centered radical in solution. Image 1 Highlights • Synthesis and characterization of an oxido-acetato-bridged tetrairon(III)-bipyridine complex. • The iron(III) complex displays antiferromagnetic ordering of iron centres in the solid state. • The iron complex efficiently activate C H bond of both linear & cyclic alkanes. • Probably generation of freely diffusing carbon-centered radical account for such activity. [ABSTRACT FROM AUTHOR]

Graphical abstract Herein, the synthesis, structural characterisation and potential catalytic activity of a tetrazinc(II) complex were investigated with experimental techniques and DFT calculations. The diverse coordination aspect of methanol in the architect of the complex and it's crucial role in oxidative coupling of 2-aminophenol through ligand centred radical pathway were comprehensively ascertained. Abstract Herein, the synthesis, structural characterization and catalytic activity of a novel tetranuclear zinc(II)–Schiff base complex, [Zn 4 (L) 2 (µ 3 -OCH 3) 2 (CH 3 OH) 2 ]·2CH 3 OH (1), [ L = N,N′- bis(3-methoxysalicylidene)-1,3-diamino-2-propanol] was presented. Single crystal X-ray diffraction structural analysis revealed that the tetra-zinc(II) cluster crystallized in a monoclinic system with P 2 1 / c space group. Interestingly, three different molecular bridges (methoxido-, alkoxido- and phenoxido-) simultaneously co-existed in assembling tetra-zinc(II) core, which was a very rare observation. To the best of our knowledge, this compound would be the first compound where a diverse coordination aspect was covered by a single solvent as terminal coordinator (CH 3 OH), bridging (µ 3 -CH 3 OH) and solvent for crystallization in the existing scientific literature. The compound showed good photo-stability and excellent luminescence property with higher lifetime at transition state in ethanol. This zinc(II) complex revealed crucial role as an effective catalytic system towards oxidation of 2-aminophenol (2-AP) in ethanol. Additionally, the tetra-zinc(II) complex displayed potential phenoxazinone synthase like activity with momentous turn over number, k cat (h−1) = 6.19 × 102 in ethanol under aerobic condition. ESI-MS and EPR spectral analysis of the reaction mixture between Zn(II) complex and 2-AP recommended that the course of catalysis proceeded through substrate–catalyst adduct formation and authenticated the radical mechanistic pathway in favor of oxidative coupling product. This tetranuclear zinc(II)–Schiff base complex would be considered as the first example that catalyzed the oxidative coupling of 2-aminophenol to aminophenoxazino compound under usual aerobic condition. As complementary, detailed quantum chemical computations, performed with density functional theory (DFT) were well corroborated with the experimental results. This was the first and rarest example where a tetrazinc(II)–Schiff base cluster exhibited catalytic oxidation of 2-AP through ligand centered radical activity. [ABSTRACT FROM AUTHOR]

A mononuclear nickel(II) complex, [Ni(bpy) 2 (OH 2 )(NO 3 )](NO 3 ) ( 1 ) [bpy = 2,2′-bipyridine], has been synthesised and structurally characterised by routine analytical techniques including a single crystal X-ray diffraction study. X-ray crystal structure analysis shows that 1 crystallises in the triclinic system with the P 1 ¯ space group and adopts an octahedral geometry. The nickel(II) complex has been evaluated as a functional model for phosphatase and catechol dioxygenase enzymes by using 4-nitrophenylphosphate (PNPP) and 3,5-di- tert -butylcatechol (DTBC) as model substrates in aqueous-DMF and acetonitrile media respectively. This mononuclear nickel complex exhibits good hydrolytic phosphoester cleavage efficiency, viz. a k cat value of 8.42 × 10 3 h −1 , and produces mostly benzoquinone ( k obs = 2.3 × 10 −3 min −1 ) and intradiol cleavage products during an investigation of catechol dioxygenase activity. [ABSTRACT FROM AUTHOR]

By varying the relative stoichiometry of the building block bis(trimethylsilyl)–N,N′–2,6–diaminopyridine (bap) and EtAlCl 2 or AlCl 3 , different molecular entities (mononuclear and dinuclear complexes, pyridinophane and molecular bowl) containing aluminum centres have been synthesized. Efforts to extend the approach to synthesize triazinophanes with bis(trimethylsilyl)-N,N′-2,4-diamino‒6‒(R)‒triazines (R = Me, NH(SiMe 3), Ph) in their reactions with AlMe 3 showed strong preference for the formation of dinuclear aluminum complexes over the analogous pyridinophane like structures. All the new compounds have been fully characterized using multinuclear NMR, HRMS and single crystal X-ray diffraction. Image 1 • Pyridinophanes containing aluminum bridged bis(SiMe 3)–N,N'–2,6–diamidopyridine (bap) have been assembled. • By varying the relative stoichiometry of bap and EtAlCl 2 , mononuclear and dinuclear Al complexes have been synthesized. • Dinuclear Al complexes are obtained with bis(SiMe 3)-N,N'-2,4-diamino‒6‒(R)‒triazine (R = Me, NH(SiMe 3), Ph) and AlMe 3. • All the compounds have been characterized by multinuclear NMR, HRMS and single crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]