Reductive Catenation of Phosphine Antimony Complexes

Reactions of triarylphosphines with fluoroantimony(III) triflates give phosphine antimony(III) complexes, which undergo spontaneous reductive elimination of fluorophosphonium cations. The resulting phosphine antimony(I) complexes catenate to give the first examples of cationic antimony bicyclic compounds, [(R₃P)₄Sb₆]⁴⁺, featuring a bicyclo[3.1.0]hexastibine framework stabilized by four phosphine ligands. The unprecedented 14‐electron redox process illustrates the generality of the reductive catenation method.     

Molecular iodine catenation in the anionic chains [Pd2I6(I2)]2–

In the easily accessible salt [(H₅O₂)(db24c8)]₂[Pd₂I₆(I₂)], iodine molecules are catenated in linear anionic chains [^…I₂PdI₂PdI₂^…I–I^…]^2– which are separated by bulky cations consisting of two (H₅O₂)⁺ cations sequestered in dibenzo‐24‐crown‐8 (db24c8) molecules. The new compound is obtained as black single crystals (triclinic, P1, a = 1001.8(2), b = 1185.8(2), c = 1503.7(3) pm, α = 102.97(1), β = 107.65(1), γ = 90.85(1)°, V = 1652.3(5) 10⁶·pm³, Z = 1) from a moist 1:1 dichloromethane/ethanol solution of PdCl₂, iodine and db24c8. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Equilibrium constant for the catenation of two hard tori

The equilibrium constant and Gibbs energy for the catenation reaction of two hard tori were calculated at several values of the ratio of minor radius to major radius -r _t /R _t . The results were used to 1) estimate the fraction of catenated molecules formed in a statistical synthesis, and 2) estimate the theoretical maximum increase in complexing ability obtained by catenation of two complexing ligands. The catenated complexing ligands synthesized by Dietrich-Buchecker et al. do not realize the theoretical enhancement due to confinement of the ring motions in the metal complex. Theoretical arguments show that, in the case of ideal gas and colligative properties, the catenated molecule must be considered as one molecule even though it is only held together by topological bonds.     

Reversible pH-Controlled Catenation of a Benzobisimidazole-Based Tetranuclear Rectangle

The development of methodologies to control on demand and reversibly supramolecular transformations from self-assembled metalla-structures requires the rational design of architectures able to answer to an applied stimulus. While solvent or concentration changes, light exposure or addition of a chemical have been largely explored to provide these transformations, the case of pH sensitive materials is less described. Herein, we report the first example of a pH-triggered dissociation of a coordination-driven self-assembled interlocked molecular link. It incorporates a pH sensitive benzobisimidazole-based ligand that can be selectively protonated on its bisimidazole moieties. This generates intermolecular electrostatic repulsions that reduces drastically the stability of the interlocked structure, leading to its dissociation without any sign of protonation of the pyridine moieties involved in the coordination bonds. Importantly, the dissociation process is reversible through addition of a base.     

Controlled Synthesis of Oligomers Containing Main-Chain B(sp2)-B(sp2) Bonds

A number of novel alkynyl-functionalized diarylbis(dimethylamino)diboranes(4) are prepared by salt metathesis, and the appended alkynyl groups are subjected to hydroboration. Their reactions with monohydroboranes lead to discrete boryl-appended diborane(4) species, while dihydroboranes induce their catenation to oligomeric species, the first known examples of well-characterized macromolecular species with B−B bonds. The oligomeric species were found to comprise up to ten repeat units and are soluble in common organic solvents. Some of the oligomeric species have good air stability and all were characterized by NMR and vibrational spectroscopy and size-exclusion chromatography techniques.     

catena‐Phosphorus Cations

Recent advances towards a systematic development of catena‐phosphorus cations are reviewed. The cations represented in this new and developing chapter in fundamental phosphorus chemistry complement the series of neutral and anionic polyphosphorus compounds.     

Stabilizing and Activating Nitrogen Catenates

The remarkably stable catenated hexa‐nitrogen chain in bis(benzotriazene‐4‐one) is structurally, theoretically, and spectroscopically characterized to illustrate the durability of the central N?N bond in this hexaazo chain. The reactions of this species illustrate the potential of these nitrogen catenates for the preparation of other condensed heterocycles, such as bispyrazolones, by thermal nitrogen exclusion or by trapping the single ring‐opened Dimroth intermediates. In these latter reactions, 2‐naphtholate anion condenses with bis(benzotriazene‐4‐one) to trap and retain a zwitterionic diazonium intermediate as an isolated diazo product, whereas transition metals ring effect ring‐extrusion of dinitrogen from the Dimroth intermediate to generate chelating σ‐aryls. The catenated nitrogen species can be stabilized by incorporating strong formal sp²?sp² N?N σ bonds with orthogonal orientations. Extending these stabilization and activation principles may allow these types of nitrogen catenates to be useful synthons for other polyaza species.