Pd complexes with trans-chelating ligands composed of two pyridyl groups and rigid π-conjugated backbone

Are bis(pyridine)iodine(I) complexes applicable for asymmetric halogenation?

Enantiopure halogenated molecules are of tremendous importance as synthetic intermediates in the construction of pharmaceuticals, fragrances, flavours, natural products, pesticides, and functional materials. Enantioselective halofunctionalizations remain poorly understood and generally applicable procedures are lacking. The applicability of chiral trans-chelating bis(pyridine)iodine(i) complexes in the development of substrate independent, catalytic enantioselective halofunctionalization has been explored herein. Six novel chiral bidentate pyridine donor ligands have been designed, routes for their synthesis developed and their [N–I–N]⁺-type halogen bond complexes studied by ¹⁵N NMR and DFT. The chiral complexes encompassing a halogen bond stabilized iodenium ion are shown to be capable of efficient iodenium transfer to alkenes; however, without enantioselectivity. The lack of stereoselectivity is shown to originate from the availability of multiple ligand conformations of comparable energies and an insufficient steric influence by the chiral ligand. Substrate preorganization by the chiral catalyst appears a necessity for enantioselective halofunctionalization.

The enantioselectivity of the iodine(i) transfer process from chiral bis(pyridine)iodine(i) complexes to alkenes is explored.

Catalytic Activity of trans-Bis(pyridine)gold Complexes

Gold catalysis has become one of the fastest growing fields in chemistry, providing new organic transformations and offering excellent chemoselectivities under mild reaction conditions. Methodological developments have been driven by wide applicability in the synthesis of complex structures, whereas the mechanistic understanding of Au(III)-mediated processes remains scanty and have become the Achilles’ heel of methodology development. Herein, the systematic investigation of the reactivity of bis(pyridine)-ligated Au(III) complexes is presented, based on NMR spectroscopic, X-ray crystallographic, and DFT data. The electron density of pyridines modulates the catalytic activity of Au(III) complexes in propargyl ester cyclopropanation of styrene. To avoid strain induced by a ligand with a nonoptimal nitrogen–nitrogen distance, bidentate bis(pyridine)–Au(III) complexes convert into dimers. For the first time, bis(pyridine)Au(I) complexes are shown to be catalytically active, with their reactivity being modulated by strain.

A trans-bidentate bis-pyridinyl ligand with a transition metal hinge

A titanocene based metalloligand, Cp*₂Ti(C₂2-py)₂, was synthesized and ligated to either Cu(i) or Pd(ii), binding Cu(i) between its alkynes and Pd(ii) between its pyridinyl rings.

1,4-Bis(2'-pyridylethynyl)benzene as a ligand in heteronuclear gold-thallium complexes. Influence of the ancillary ligands on their optical properties

The reaction of 1,4-bis(2'-pyridylethynyl)benzene (L) with [{Au(C6X5)2}Tl]n affords new heterometallic Au(I)/Tl(I) complexes with different stoichiometries, structural arrangements and optical properties depending on the halogens present in the aryl group. The chlorinated derivative [{Au(C6Cl5)2}Tl(L)]n () displays polymeric chains built thanks to unsupported AuTl interactions and bridging bidentate ligands between adjacent chains, while in the fluorinated species [{Au(C6F5)2}2Tl2(L)2]n (), also containing N-donor bridging ligands and AuTl contacts, polymerization occurs via TlCaryl non-bonding interactions between neighbouring molecules. The optical properties of and have been studied experimentally and theoretically, concluding that the luminescence of in the solid state has its origin in the AuTl interactions, and that the TlCaryl interactions in favour a non-radiative deactivation pathway that avoids luminescence. The strength of the non-bonding interactions present in has also been theoretically studied at the HF and MP2 levels, revealing the metallophilic contact as the strongest one.

Interfacial mass transfer by controlled multilayer disassembly

We demonstrated the one-pot disassembly of self-propagating molecular assemblies (SPMAs) by ligand exchange and the subsequent covalent binding of the molecular components to other surfaces. These functionalized surfaces are suitable for regenerating the SPMAs.

A rhomboid-shaped organic host molecule with small binding space. Unsymmetrical and symmetrical inclusion of halonium ions

A shape persistent rhomboid-shaped organic host molecule having two pyridyl units was synthesized which induces size selective halonium inclusion.