Peter J. Steel

Aromatic nitrogen heterocycles as bridging ligands; a survey

Revue synthetique concernant une serie de coordinats bidentes et tridentes, heterocycliques azotes. Synthese bibliographique

The First Coordinatively Saturated, Quadruply Stranded Helicate and Its Encapsulation of a Hexafluorophosphate Anion.

Incarcerated in a helical prison: The encapsulation of a PF6- ion within a quadruply stranded helicate (shown schematically) results from the self-assembly of four molecules of 1,4-bis(3-pyridyloxy)benzene and two PdII ions. This represents not only the first example of a coordinatively saturated quadruple helicate, but also the first example of the encapsulation of a complex anion by a helicate.

Chiral heterocyclic ligands. Part IV. Synthesis and metal complexes of 2,6-Bis(pyrazol-1-ylmethyl)pyridine and chiral derivatives

Synthesis of the new tridentate ligand, 2,6-bis(pyrazol-1-ylmethyl)pyridine ( 6 ) and its chiral derivatives ( 11–15 ) are described. The preparations of complexes of these ligands with several divalent transition metal ions (Fe 2+ , Ni 2+ , Cu 2+ , Ru 2+ , Pd 2+ ) are reported. X-ray crystal structures have been determined for the [Ni( 6 ) 2 ](ClO 4 ) 2  16 and [Cu( 13 )(NCS) 2 ] 17 complexes. The salt 16 crystallises in the orthorhombic space group P 2 1 2 1 2 with a = 10.125(1), b = 17.657(4), c = 8.579(2) A and Z = 2. The structure was refined to a conventional R factor of 3.9% and shows the nickel atom to lie on a crystallographic two-fold rotation axis in a ‘symmetrical’ octahedral environment. The complex 17 crystallises in the orthorhombic space group P 2 1 2 1 2 1 with a = 15.795(3), b = 20.433(3), c = 9.618(1) A and Z = 4. The structure was refined to R = 4.7% and shows the bonding geometry at the five-coordinate copper atom to be intermediate between square pyramidal and trigonal bipyramidal. In both structures the six-membered chelate rings exist in boat conformations.

Cyclometallated compounds V. Double cyclopalladation of diphenyl pyrazines and related ligands

Abstract 2,3-Diphenylpyrazine and four structurally related ligands have each been singly and doubly cyclopalladated and the products characterised by 1H and 13C NMR studies of their acetylacetonate complexes. The structure of a doubly cyclometallated Pd(acac) complex of 2,3-diphenylpyrazine has been determined by an X-ray diffraction study (R = 0.039). A strong steric interaction between the two cyclopalladated phenyl rings is relieved by twisting; the two chelate ring mean-planes are mutually inclined at an angle of 19.6(5)°.

Cyclometallated compounds II. Proton and carbon-13 nuclear magnetic resonance spectral assignments of cyclopalladated compounds☆

The 1H and 13C NMR spectra of nineteen cyclopalladated acetylacetonate complexes are reported. Definitve spectral assignments are made on the basis of selective proton decoupling experiments, difference NOE spectra and both homo- and hetero-nuclear two-dimensional correlation spectroscopy. The Pd(acac) substituent is shown to induce characteristic chemical shift changes in both proton and carbon spectra. These effects, however, vary from those of differently substituted palladium and other metal substituents.

4,5-Di(2-pyridyl)-1,2,3-triazolate: the elusive member of a family of bridging ligands that facilitate strong metal–metal interactions

The new click-adduct 4,5-di(2-pyridyl)-1,2,3-triazole acts as a doubly-chelating anionic bridging ligand that forms dinuclear ruthenium(II) complexes which exhibit strong metal-metal interactions.

Chiral heterocyclic ligands: III. A structural study of the cyclopalladation of (4S, 7R)-7,8,8-trimethyl-1-phenyl-4,5,6,7-tetrahydro-4,7-methano-1H-indazole

Abstract Reaction of the ligand (4 S , 7 R )-7,8,8-trimethyl-1-phenyl-4,5,6,7-tetrahydro-4,7-methano-1 H -indazole, LHV, with lithium tetrachloropalladate gives a trans -Pd(LH) 2 Cl 2 complex, which on further reaction undergoes cyclopalladation to [PdLCl] 2 . These compounds were characterised spectroscopically and their structures confirmed by single crystal X-ray analyses, with refinement to R values of 0.028 and 0.036 respectively.

Redox active electrochromic polymers from low oxidation monomers containing 3,4-ethylenedioxythiophene (EDOT)

Abstract Here we report the synthesis of several new low oxidation monomers with the external rings being 3,4-ethylenedioxythiophene (EDOT). These monomers were prepared via NiCI2(dppp) catalyzed Grignard coupling in good yields and were found to exhibit low oxidation potentials with the lowest having an onset of 0.14 V for 2,2′:5′,2″-ter(3,4-ethylenedioxythienyl)thiophene (TER-EDOT). The polymers were found to be stable electrical conductors and were found to exhibit band gaps ranging from 1.4 eV for trans-1,2-bis(2-(3,4-ethylenedioxy)thienyl)vinylene (BEDOT-V) to 2.5 eV for the series of 3,6-bis(2-(3,4-ethylenedioxy)-thienyl)N-substituted carbazoles (BEDOT-NCz). BEDOT-V was found to be opaque purple in the reduced state and transmissive sky blue in the oxidized state while the BEDOT-NCzs are transmissive yellow in the reduced state, green upon mild oxidation and deep opaque blue in the oxidized state. Both the BEDOT-V and BEDOT-NCzs were found to exhibit fast response times and high contrast ratios upon redox stepping, thereby proving them useful for electrochromic coatings.

Chiral heterocyclic ligands. Part 9. Homoconfigurational coordination polymers based on a C2-symmetric, linear-bridging ligand

The fusion of two bornane units to a pyrazine ring gives a sterically hindered C2-symmetric linear bridging ligand that readily assembles into one-dimensional coordination polymers; X-ray crystal structures are described for the free ligand and metallopolymers formed by reaction with silver(I) nitrate and copper(I) iodide.

Cyclometallated compounds IV. Cyclopalladation of phenylpyrimidines and X-ray structure of a doubly cyclopalladated derivative of 4,6-diphenylpyrimidine

Abstract Seven phenylpyrimidines have been cyclopalladated with lithium tetrachloropalladate and the products characterised by 1H and 13C NMR studies of their acetylacetonate complexes. 6-Methyl-2,4-diphenylpyrimidine and 2,4,6-triphenylpyrimidine undergo preferential metallation of the 2-phenyl ring. 4-(para-Nitrophenyl)-6-phenylpyrimidine is selectively monopalladated in the unsubstituted phenyl ring. 4,6-Diphenylpyrimidine has been doubly cyclopalladated, and an X-ray crystal structure of its acetylacetonate complex refined to an R value of 0.053.