Construction of heterometallic M2Pd3 supramolecular cages via a metalloligand strategy as heterogeneous catalyst for Suzuki–Miyaura coupling reaction

Heterometallic cages: synthesis and applications

High symmetry metallosupramolecular architectures (MSAs) have been exploited for a range of applications including molecular recognition, catalysis and drug delivery. Recently there have been increasing efforts to enhance those applications by generating reduced symmetry MSAs. While there are several emerging methods for generating lower symmetry MSAs, this tutorial review examines the general methods used for synthesizing heterometallic MSAs with a particular focus on heterometallic cages. Additionally, the intrinsic properties of the cages and their potential emerging applications as host-guest systems and reaction catalysts are described.

Cellulose derived Pd nano-catalyst for efficient catalysis

Using green, environmentally friendly and resource-rich cellulose as a raw material, a ligand-free and highly dispersed palladium (Pd) nano-catalyst was successfully prepared in a facile way. A variety of characterization results showed that the Pd nanoparticles (NPs) were uniformly spread on the cellulose nanoporous microspheres, with an average particle size of ∼2.75 nm. As a carrier, cellulose microspheres with nanoporous structure and rich -OH groups greatly promoted the attachment and distribution of the highly dispersed Pd NPs, along with the diffusion and exchange of reactants, so as to greatly promote the catalytic activity. In the Suzuki-Miyaura coupling reaction, the catalyst of C-Pd exhibited excellent catalytic activity (TOF up to 2126 h-1), broad applicability, and good recyclability with almost no active loss in 6 continuous runs. This utilizing of bioresources to build catalyst materials is important for sustainable chemistry.

Lanthanide induced variability in localised CoII geometries of four triangular L3Co3 IILnIII complexes

Four tetranuclear heterobimetallic triangle complexes [L3Co3Dy(NO3)2(H2O)(MeOH)5](NO3) (C1), [L3Co3Gd(NO3)3(MeOH)4] (C2), [L3Co3La(NO3)2(H2O)6](NO3)(H2O) (C3), and [L3Co3TbCl(NO3)2(H2O)0.5(MeOH)3.5] (C4), where H2L = 1,4-bisformylnaphthalene-2,3-diol, have been synthesised and structurally characterised. Each complex crystallises with a complete molecule in the asymmetric unit (Z' = 1) and displays near perfect octahedrality in two out of three CoII centres. The third CoII ion assumes a different coordination geometry in each complex: six-coordinate octahedral in C1, six-coordinate with a distortion towards trigonal prismatic in C2, five-coordinate trigonal bipyramidal in C3, and five-coordinate square pyramidal in C4; which has been attributed to increasing lanthanide cation size, coupled with a non-macrocyclic coordination environment. Continuous Shape Measurement (CShM) calculations and octahedral distortion parameter calculations were performed, using the SHAPE and OctaDist software packages, respectively, in order to aid in the assessment of each metal centre's local coordination geometry. The preliminary magnetic investigation of C3 found χ m T = 9.4 cm3 K mol-1 at 300 K and M = 7.1 μ B at 1.8 K, which are approximately two thirds the maximum theoretical values for three CoII ions and indicates the presence of a relatively large zero-field splitting parameter (D/k B = 65 K) operative in each CoII ion rather than exchange coupling between the CoII centres.

Emerging Spacers-Based Ligands for Supramolecular Coordination Complexes

The design and self-assembly of supramolecular coordination complexes (SCCs) i. e., discrete cyclic metalloarchitectures such as cycles, cages, mesocates, and helicates with desired size, shape, and properties have been increasing exponentially owing to their potential applications in molecular sensors, molecular cargos, molecular recognition, and catalysis. The introduction of the organic motifs and metal complexes as a spacer provides functionality to the metalloarchitecture. This review mainly focusses on newly evolving spacer based ligands employed to yield simple to high-order metallosupramolecular assemblies using straight-forward approaches. The new spacers including corannulene, organic cyclic framework, bicyclic organic motifs, aliphatic chain, metalloligands, triarylboron, BODIPY, azaphosphatrane, phosphine, and thio/selenophosphates offer a great set of properties and in-built functionalities to the metalloarchitectures which are discussed in this review.

Metalloligand Strategies for Assembling Heteronuclear Nanocages – Recent Developments

The use of metalloligands as building blocks for the assembly of metallo-organic cages has received increasing attention over the past two decades or so. In part, the popularity of this approach reflects its stepwise nature that lends itself to the predesigned construction of metallocages and especially heteronuclear metallocages. The focus of the present discussion is on the use of metalloligands for the construction of discrete polyhedral cages, very often incorporating heterometal ions as structural elements. The metalloligand approach uses metal-bound multifunctional ligand building blocks that display predesigned structural properties for coordination to a second metal ion such that the rational design and construction of both homo- and heteronuclear metal–organic cages are facilitated. The present review covers published literature in the area from early 2015 to early 2019.

Efficient Suzuki⁻Miyaura C-C Cross-Couplings Induced by Novel Heterodinuclear Pd-bpydc-Ln Scaffolds

An easy access to a series of previously unreported heterodinuclear Pd-Ln compounds, Pd-bpydc-La, Pd-bpydc-Ce and Pd-bpydc-Nd (bpydc = 2,2'-bipyridine-5,5'-dicarboxylate) has been developed. The Pd-Ln hybrid networks were effectively applied as catalysts in Suzuki⁻Miyaura C-C cross-coupling reactions of 4-bromoanisole and 4-bromobenzonitrile with phenylboronic acid, under mild conditions. A systematic investigation revealed Pd-bpydc-Nd as the most active catalyst. In all cases, reaction yields varied with the base, catalyst loading and substantially augmented with temperature (from 30 to 60 °C). Substituent effects were operative when changing from 4-bromoanisole to 4-bromobenzonitrile. The key role played by the lanthanides, aromatic substrate and base, in modulating the Pd-catalytic cycle has been highlighted. Importantly, the new catalysts proved to be stable in air and vs. functionalities and are quite efficient in Suzuki⁻Miyaura carbon-carbon bond formation conducted in protic solvents.