Kieran Griffiths

Heteronuclear 3 d/DyIII Coordination Clusters as Catalysts in a Domino Reaction

Three isoskeletal tetranuclear coordination clusters with general formula [M(II) 2 Dy(III) 2 L4 (EtOH)6 ](ClO4 )2 ⋅2 EtOH, (M=Co, 1; M=Ni, 2) and [Ni(II) 2 Dy(III) 2 L4 Cl2 (CH3 CN)2 ]⋅2 CH3 CN (3), have been synthesized and characterized. These air-stable compounds, and in particular 3, display efficient homogeneous catalytic behavior in the room-temperature synthesis of trans-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere.

Efficient NiII2LnIII2 Electrocyclization Catalysts for the Synthesis of trans-4,5-Diaminocyclopent-2-enones from 2-Furaldehyde and Primary or Secondary Amines

A series of heterometallic coordination clusters (CCs) [Ni(II)2Ln(III)2(L1)4Cl2(CH3CN)2] 2CH3CN [Ln = Y (1Y), Sm (1Sm), Eu (1Eu), Gd (1Gd), or Tb (1Tb)] were synthesized by the reaction of (E)-2-(2-hydroxy-3-methoxybenzylidene-amino)phenol) (H2L1) with NiCl2·6(H2O) and LnCl3·x(H2O) in the presence of Et3N at room temperature. These air-stable CCs can be obtained in very high yields from commercially available materials and are efficient catalysts for the room-temperature domino ring-opening electrocyclization synthesis of trans-4,5-diaminocyclopent-2-enones from 2-furaldehyde and primary or secondary amines under a non-inert atmosphere. Structural modification of the catalyst to achieve immobilization or photosensitivity is possible without deterioration in catalytic activity.

Cobalt(II/III), nickel(II) and copper(II) coordination clusters employing a monoanionic Schiff base ligand: synthetic, topological and computational mechanistic aspects

Nine mono-, di- and tetranuclear coordination clusters (M = CoII/III, NiII, CuII) using a monoanionic Schiff base ligand were synthesized and characterized by X-ray crystallography. A series of transformations occur in the ligand in certain compounds for which theoretical studies are presented. Synthetic aspects, topological issues and magnetic studies are discussed.

3d/4f Coordination Clusters as Cooperative Catalysts for Highly Diastereoselective Michael Addition Reactions

Michael addition (MA) is one of the most well studied chemical transformation in synthetic chemistry. Here, we report the synthesis and crystal structures of a library of 3d/4f coordination clusters (CCs) formulated as [ZnII2YIII2L4(solv)X(Z)Y] and study their catalytic properties toward the MA of nitrostyrenes with barbituric acid derivatives. Each CC presents two borderline hard/soft Lewis acidic ZnII centers and two hard Lewis acidic YIII centers in a defect dicubane topology that brings the two different metals into a proximity of ∼3.3 Å. Density functional theory computational studies suggest that these tetrametallic CCs dissociate in solution to give two catalytically active dimers, each containing one 3d and one 4f metal that act cooperatively. The mechanism of catalysis has been corroborated via NMR, electron paramagnetic resonance, and UV-vis. The present work demonstrates for the first time the successful use of 3d/4f CCs as efficient and high diastereoselective catalysts in MA reactions.

Isoskeletal Schiff base polynuclear coordination clusters: synthetic and theoretical aspects

This work addresses and enlightens synthetic aspects derived from our effort to systematically construct isoskeletal tetranuclear coordination clusters (CCs) of the general formula [TR2Ln2(LX)4(NO3)2(solv)2] possessing a specific defected dicubane topology, utilizing various substituted Schiff base organic ligands (H2LX) and NiII/CoII and Dy(OTf)3 salts. Our synthetic work is further supported by DFT studies.

Tetranuclear Zn2Ln2 coordination clusters as catalysts in the Petasis borono-Mannich multicomponent reaction

We report herein for the first time the efficiency of heteronuclear Zn/Ln coordination clusters (CCs) as catalysts for the multicomponent Mannich-type condensation that involves amines, aldehydes and boronic acids, known as the Petasis borono-Mannich (RBR) reaction. The reaction proceeds in very good to excellent yields (84–98%, 17 products) at room temperature with catalyst loadings as low as 1.0 mol%.

Topological insights in polynuclear Ni/Na coordination clusters derived from a schiff base ligand

This article presents the syntheses, crystal structures, topological features and magnetic properties of two NiII/NaI coordination clusters formulated [Ni3IINa(L1)3(HL1)(MeOH)2] (1) and [Ni6IINa(L1)5(CO3)(MeO)(MeOH)3(H2O)3]·4(MeOH) 2(H2O) [2 4(MeOH) 2(H2O)] where H2L1 is the semi-rigid Schiff base ligand (E)-2-(2-hydroxy-3-methoxybenzylideneamino)-phenol). Compound 1 possesses a rare Ni3IINaI cubane (3M4-1) topology, and compound 2 is the first example in polynuclear Ni/Na chemistry that exhibits a 2,3,4M7-1 topology.

Cation binding, transport and theoretical calculations of cone-p-tert-butylhexahomotrioxacalix[3]arene tris(acetic acid)

The metal cation binding ability of cone-p-tert-butylhexahomotrioxacalix[3]arene tris(acetic acid) was investigated by 1H NMR and complementary semi-empirical calculations. NMR showed significant shifts with Na+, K+, Ag+ and, to a lesser extent, Pb2+. The macrocyclic protons undergoing the greatest shifts imply that these cations bind inside the cavity composed of the phenoxy and carbonyl oxygen atoms. Metal complexes were modelled using a semi-empirical approach and, in general, their geometry optimised structures were in agreement with NMR data. U-tube transport experiments demonstrated that the macrocycle actively transported Cr3+, Fe3+, Co2+ and Cu2+ through the organic phase.

Polynuclear ampyrone based 3d coordination clusters

The use of the monoanionic Schiff base ligand (E)-4-(2-hydroxybenzylideneamino)-2,3-dimethyl-1-phenyl-1,2-dihydropyrazol-5-one in transition (Co, Ni and Cu) coordination chemistry yields mono-, tetra- and pentanuclear coordination clusters (CCs) with different structural motifs. An organic transformation occurs in the ligand in the Cu compound for which theoretical studies are presented. Solution studies, topological issues and magnetic studies are discussed. The present results demonstrate the richness of the coordination chemistry of this monoprotic organic ligand, which promotes the formation of high-nuclearity CCs.