Calixarenes grafted with Bu2P(O)CH2O binding groups at the narrow rim: synthesis, structure and extraction of heterometallic Ru/Zn complexes

Calix[n]arenes (n?=?4, 6) existing in the cone, 1,3-alternate or 1,3,5-alternate conformations and functionalized by two, four or six Bu₂P(O)CH₂O groups have been synthesized by the alkylation of hydroxycalix[4,6]arenes with tosylate of dibutylhydroxymethylphosphine oxide. Their molecular and crystal structures as well as binding properties towards of heterometallic Ru/Zn complexes were investigated. Due to the ??calixarene effect?? the phosphine oxides are effective extractants for the Ru/Zn complexes.     

A <Superscript>31</Superscript>P NMR study of ligand substitution in heterometallic Ru/Zn complexes

Based on the ³¹P NMR data, equilibriums in the [RuNO(NO₂)₄OHZn(TPPO)₃]-Py system are quantitatively described, and equilibrium constants of dissociation of the initial complex and organic ligand substitution are determined. The stability of heterometallic complexes is found to increase in passing from TPPO to pyridine. The mixed ligand [RuNO(NO₂)₄OHZn(TPPO)₂Py] complex is structurally characterized, and it is shown that the TPPO molecule in the trans-position to the μ²-bridging hydroxo group is substituted first.     

Using photoelectron spectroscopy for the investigation of substituent effects in N‐ and P‐centered radical cations

The information concerning the peculiarities of the intramolecular interactions in the radical cations which is currently available is very sketchy. In this work, a new approach to the investigation of the substituent effects in N‐ and P‐centered radical cations has been developed. It is based on a consideration of the core‐electron binding energies E and ionization potentials I of the 15 series of the neutral molecules measured by photoelectron spectroscopy. Properties E and I obey the linear free energy relationship. By using the correlation analysis, in radical cations the inductive, resonance, and polarizability effects were first established to be in operation. The polarizability effect is caused by the charge on the radical cation centers N^?+ and P^?+. The contribution of this effect ranges from 10 to 55%. In the radical cations containing the moieties with N^?+?X and P^?+?X bonds, the standard resonance constants σ_R and σ of the substituents X are of limited utility. An understanding of the substituent effects may give a better insight into the mechanisms of both: radical ions and heterolytic reactions. Copyright © 2010 John Wiley & Sons, Ltd.     

A New Class of Two-Deck Dicationic Heteropentalenes Existing by the Balance between Interdeck Aromaticity and Covalent P−P Bonding

A number of two-deck dicationic 3a,6a-diaza-1,4-diphosphapentalenes (DDP)₂X₂ (X=halogen or complex ion) have been characterized. Interdeck distances P(1)⋅⋅⋅P(3) and P(2)⋅⋅⋅P(4) in crystal structures, as a rule, significantly exceed the sum of covalent radii, however they are still within the sum of van der Waals radii. The ³¹P NMR data indicate that phosphorus atoms are equivalent in solution even at low temperatures (233 K). Based on DFT calculations, the formation of two equivalent P−P covalent bonds (<2.4 Å) is energetically unfavorable, despite the absence of steric barriers. The total energy of the model dication as a function of the P⋅⋅⋅P separation has a minimum at the P−P distance of 2.85 Å. This distance corresponds to the highest aromaticity index in the interdeck space (NICS(1.0)=−20.72). The energy of interdeck interactions is estimated at 10–15 kcal/mol.