Review: Recent advances of one-dimensional coordination polymers as catalysts

This review aims to provide reports of one dimensional (1-D) coordination polymers that have been used as catalysts in various organic reactions in the last decade, covering the literature from 2007 and onwards. The CPs have been mainly categorized into homometallic and heterometallic compounds; additional parameters such as the metal and ligand selection for the CP are discussed to provide a more detailed look into each system

Recent advances in the coordination chemistry of benzotriazole-based ligands

With the use of N-donor ligands in coordination chemistry receiving significant interest and attention in the last few decades, benzotriazole has emerged as an ideal molecule that provides many synthetic advantages and reliable routes towards polynuclear coordination clusters and coordination polymers. In order to fully realise this potential, the current work provides a systematic study of the recent advances on the use of benzotriazole and its derivatives as ligands in coordination chemistry. The reported complexes have been primarily categorized in regards to the exact linker used and its role in the resulting architecture (either as a main or as a secondary ligand). Important structural information, as well as notable properties (such as magnetism, catalysis, luminescence, bio-applications) are also mentioned for the compounds

Employment of semi-rigid N-donor ligands towards the synthesis of functional coordination polymers with low dimensionality

The focus of this thesis is the design of low-dimensional coordination polymers (CPs) using semi-rigid N-donor ligands based on heterocyclic molecules, especially benzotriazole, and the investigation of their potential magnetic and catalytic properties. Chapter 1 serves as a general introduction to the chemistry discussed in the thesis. The first part emphasizes on the synthetic aspects and applications of CPs. The second part presents the unique chemical characteristics of benzotriazole and includes a thorough literature review on its use as a ligand in coordination chemistry, culminating to the development of a ligand system for the design of the targeted materials. Chapter 2 introduces the main family of benzotriazole-based ligands (L1-L3) employed in this thesis, focusing on their coordination chemistry with cobalt salts. The synthesis and characterisation of a series of novel 0D, 1D and 2D compounds with a large structural variety is reported. Synthetic aspects and magnetic properties of selected compounds are discussed. Chapters 3, 4 and 5 report a series of copper coordination compounds employing L1-L3 as well as analogous N-donor ligands (L4-L8). A system of 1D CPs is established and investigated for its catalytic properties in a range of organic transformations that includes the synthesis of 1,4-dihydropyridines through a previously unreported route, the A3 coupling and the ‘click’ azide-alkyne cycloaddition reaction. Investigations into optimising the catalytic behaviour and mechanistic aspects of this system are presented. In Chapter 6 the coordination capabilities of L1-L3 are combined with the rich chemistry of silver salts to generate a structurally diverse family of 0D, 1D and 2D compounds. Investigations of their potential catalytic properties in the A3 coupling and alkyne hydration reactions are additionally presented. Chapter 7 provides an overall conclusion to the work presented in the thesis, including its contributions to the reported literature as well as potential future directions. Finally, experimental and synthetic details as well as crystallographic data are presented in Chapter 8 and Chapter 9 respectively

A 12-fold ths interpenetrated network utilizing a glycine-based pseudopeptidic ligand

We report the synthesis and characterization of a 3D Cu(II) coordination polymer, [Cu3(L1)2(H2O)8]·8H2O (1), with the use of a glycine-based tripodal pseudopeptidic ligand (H3L1 = N,N’,N’’-tris(carboxymethyl)-1,3,5-benzenetricarboxamide or trimesoyl-tris-glycine). This compound presents the first example of a 12-fold interpenetrated ths net. We attempt to justify the unique topology of 1 through a systematic comparison of the synthetic parameters in all reported structures with H3L1 and similar tripodal pseudopeptidic ligands. We additionally explore the catalytic potential of 1 in the A3 coupling reaction for the synthesis of propargylamines. The compound acts as a very good heterogeneous catalyst with yields up to 99% and loadings as low as 3 mol%

Dinuclear Lanthanide (III) coordination polymers in a domino reaction

A systematic study was performed to further optimise the catalytic room-temperature synthesis of trans-4,5- diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere. For this purpose, a series of dinuclear lanthanide (III) coordination polymers were synthesised using a dianionic Schiff base and their catalytic activities were investigated

Exploring the coordination capabilities of a family of flexible benzotriazole-based ligands using Cobalt (II) sources

In this study we focus on the coordination chemistry of a family of three flexible benzotriazole-based ligands (L1-L3) using Cobalt(II) salts. Our efforts have resulted to the formation of ten novel compounds, formulated as [Co2(L1)2Cl4]·2MeCN (1·2MeCN), Co2(L1)2Br4 (2), [Co(L2)Cl2]·MeCN (3·MeCN), Co(L2)Cl2 (4), [Co2(L2)2Br4]·2MeCN (5·2MeCN), [Co(L2)2(NO3)2]·2MeCN (6·2MeCN), [Co2(L3)2Cl4]·2MeCN (7·2MeCN), Co2(L3)2Cl4 (8), Co2(L3)2Br4 (9), and Co(L3)2(NO3)2 (10). The structures have been well characterised through X-Ray crystallography, FT-IR, ESI-MS, PXRD, Elemental Analysis and TGA studies. The compounds show a large structural variety depending on synthetic parameters (ratio, temperature and metal salt) and the ligand selection (various conformations in each ligand). When tuned appropriately, these factors drastically affect dimensionality, metal geometry and the nuclearity of the final product, resulting in a range of 0D dimers (1, 3, 5, 8, 9), 1D (2, 7, 10) and 2D (4, 6) coordination polymers (CPs). A temperature-induced single-crystal to single-crystal transformation of compound 3 to 4 is additionally reported. The magnetic properties of representative compounds (4, 7, 9) are subject to large changes with only minor structural variations, suggesting that tetrahedral Co(II) nodes in CPs or MOFs could function as sensitive reporters of small changes in the local environment

Structural diversity and catalytic properties in a family of Ag(I)-benzotriazole based coordination compounds

In this work we study the coordination chemistry of a series of semi-rigid benzotriazole based ligands (L1-L3) along with the low coordination number but versatile AgI ions. This has led to nine new coordination compounds formulated [Ag(L1)(CF3CO2)] (1), [Ag2(L1T)2(CF3SO3)2]·2Me2CO (2), [Ag(L2T)(ClO4)(Me2CO)] (3), [Ag(L2T)(BF4)(Et2O)] (4), [Ag2(L3T)2(ClO4)2]2 (5), [Ag(L3)(NO3)] (6), [Ag2(L3T)2(CF3CO2)2] (7), [Ag2(L3T)(CF3SO3)2] (8) and [Ag2(L3T)2(CF3CF2CO2)2]·2Me2CO (9). These compounds show structural diversity including dimers (5, 7, 9), one dimensional (1D) (3, 4, 6) and two dimensional (2D) (1, 2, 8) coordination polymers. The presence of the two -CH2- units between the three rigid backbones, benzotriazole/-C6H4-/benzotriazole, provides a limited, but significant, flexibility in L1-L3, influencing their variety coordination abilities. Interestingly, certain structures exhibit an isomerism effect (L1T-L3T) in the benzotriazole unit when in solid state; a series of studies are indicative of the 1,1- form is generally dominant in solution even in cases where the crystal structure does not contain this tautomer. The homogeneous catalytic efficacy of all compounds against the well-known multi component A3 coupling reaction and the hydration of alkynes were investigated. Compound 4 was identified as the optimal catalyst for both reactions, promoting the multicomponent coupling as well as the alkyne hydration reaction under low loadings (0.5 and 3 mol%, respectively) and in high yields (up to 99 and 93% in each case)

Copper-promoted regioselective synthesis of polysubstituted pyrroles from aldehydes, amines and nitroalkenes via1,2-phenyl/alkyl migration

The facile Copper-catalyzed synthesis of polysubstituted pyrroles from aldehydes, amines and β-nitroalkenesis reported. Remarkably, the use of α-methyl substituted aldehydes provide efficient access to a series of tetra- and pentasubstituted pyrroles via an overwhelming 1,2-phenyl/alkyl migration. The present methodology is also accessible to non α-substituted aldehydes yielding the corresponding trisubstituted pyrroles. On the contrary, the use of ketones, in place of aldehydes, does not promote the organic transformation signifying the necessity of α-substituted aldehydes. The reaction proceeds under mild catalytic conditions with low catalyst loading (0.3 – 1 mol %), a broad scope, very good functional-group tolerance, high yields and can be easily scaled up to more than 3 mmol of product, thus highlighting a useful synthetic application of the present catalytic protocol. Based on formal kinetic studies, a possible radical pathway is proposed that involves the formation of an allylic nitrogen radical intermediate, which in turn reacts with the nitroalkene to yield the desired pyrrole framework via a radical 1,2-phenyl or alkyl migration

Cu(II) coordination polymers as vehicles in the A³ coupling

A family of benzotriazole based coordination compounds, obtained in two steps and good yields from commercially available materials, formulated [CuII(L 1 )2(MeCN)2]·2(ClO4)·MeCN (1), [CuII(L 1 )(NO3)2]·MeCN (2), [ZnII(L 1 )2(H2O)2]·2(ClO4)·2MeCN (3), [CuII (L 1 )2Cl2]2 (4), [CuII 5(L 1 )2Cl10] (5), [CuII 2(L 1 )4Br2]·4MeCN·(CuII 2Br6) (6), [CuII(L 1 )2(MeCN)2]·2(BF4) (7), [CuII(L 1 )2(CF3SO3)2] (8), [ZnII(L 1 )2(MeCN)2]·2(CF3SO3) (9), [CuII 2(L 2 )4(H2O)2]·4(CF3SO3)·4Me2CO (10) and [CuII 2(L 3 )4(CF3SO3)2]·2(CF3SO3)·Me2CO (11) are reported. These air stable compounds were tested as homogeneous catalysts for the A3 coupling synthesis of propargyl amine derivatives from aldehyde, amine and alkyne under a non-inert atmosphere. Fine-tuning of the catalyst resulted in a one dimensional (1D) coordination polymer (CP) (8) with excellent catalytic activity in a wide range of substrates, avoiding any issues that would inhibit its performance

Copper(II)-benzotriazole coordination compounds in click chemistry: a diagnostic reactivity study

This diagnostic study aims to shed light on the catalytic activity of a library of Cu(II) based coordination compounds with benzotriazole-based ligands. We report herein the synthesis and characterization of five new coordination compounds formulated [CuII(L4)(MeCN)2(CF3SO3)2] (1), [CuII(L5)2(CF3SO3)2] (2), [CuII(L6)2(MeCN)(CF3SO3)]·(CF3SO3) (3), [CuII(L6)2(H2O)(CF3SO3)]·(CF3SO3)·2(Me2CO) (4), [CuI4(L1)2(L1’)2(CF3SO3)2]2·4(CF3SO3)·8(Me2CO) (5), derived from similar nitrogen-based ligands. The homogeneous catalytic activity of these compounds along with our previously reported coordination compounds (6 -13), derived from similar ligands, is tested against the well-known Cu(I)-catalysed azide-alkyne cycloaddition reaction. The optimal catalyst [CuII(L1)2(CF3SO3)2] (10) activates the reaction to afford 1,4-disubstituted 1,2,3-triazoles with yields up to 98% and without requiring a reducing agent. Various control experiments are performed to optimize the method as well as examine parameters such as ligand variation, metal coordination geometry and environment, in order to elucidate the behaviour of the catalytic system