Reversible P-P bond cleavage at an iridium(III) metal centre.

Treatment of a κ-P-monodentate bicyclic diphosphane iridium(III) complex with a labile gold(I) precursor afforded an unusual Ir/Au complex in which the P-P single bond has been cleaved. This reaction was cleanly reversed upon addition of tertiary phosphine. Carbon-carbon bond activation, across neighbouring PCN rings of the coordinated bicyclic diphosphane, occurred upon thermolysis of the Ir/Au complex.

Exploiting host-guest chemistry to manipulate magnetic interactions in metallosupramolecular ML tetrahedral cages.

Reaction of Ni(OTf) with the bisbidentate quaterpyridine ligand results in the self-assembly of a tetrahedral, paramagnetic cage [Ni ]. By selectively exchanging the bound triflate from [OTf⊂Ni ](OTf) (), we have been able to prepare a series of host-guest complexes that feature an encapsulated paramagnetic tetrahalometallate ion inside this paramagnetic host giving [MX⊂Ni ](OTf), where MX = MnCl (), CoCl (), CoBr (), NiCl (), and CuBr () or [MX⊂Ni ](OTf), where MX = FeCl () and FeBr (). Triflate-to-tetrahalometallate exchange occurs in solution and can also be accomplished through single-crystal-to-single-crystal transformations.

[CrNi] Heterometallic Coordination Cubes.

Three new heterometallic [CrNi] coordination cubes of formulae [CrNiL(HO)](NO) (), [CrNiL(MeCN)(HO)](ClO) (), and [CrNiLCl] () (where HL = 1-(4-pyridyl)butane-1,3-dione), were synthesised using the paramagnetic metalloligand [CrL] and the corresponding Ni salt. The magnetic skeleton of each capsule describes a face-centred cube in which the eight Cr and six Ni ions occupy the eight vertices and six faces of the structure, respectively. Direct current magnetic susceptibility measurements on () reveal weak ferromagnetic interactions between the Cr and Ni ions, with = + 0.

A Stereoselective aza-Prins Reaction: Rapid Access to Enantiopure Piperidines and Pipecolic Acids.

The aza-Prins reaction is a widely employed and highly efficient method for the preparation of saturated nitrogen-containing heterocycles. Its major drawback has always been a lack of diastereoselectivity and the formation of racemic products. Herein, we address these problems and report, for the first time, the synthesis of both diastereomerically and enantiopure multiply substituted piperidines via the aza-Prins reaction.

Hydride Transfer to Gold: Yes or No? Exploring the Unexpected Versatility of Au⋅⋅⋅H-M Bonding in Heterobimetallic Dihydrides.

The potential for coordination and H-transfer from Cp MH (M=Zr, W) to gold(I) and gold(III) complexes was explored in a combined experimental and computational study. [(L)Au] cations react with Cp WH giving [(L)Au(κ -H WCp )] (L=IPr (1), cyclic (alkyl)(amino)carbene (2), PPh (3) and Dalphos-Me (4) [IPr=1,3-bis(diisopropylphenyl)imidazolylidene; Dalphos-Me=di(1-adamantyl)-2-(dimethylamino)phenyl-phosphine], while [Au(DMAP) ] (DMAP=p-dimethylaminopyridine) affords the C -symmetric [Au(κ-H WCp ) ] (5). The Dalphos complex 4 can be protonated to give the bicationic adduct 4 H, showing Au ⋅⋅⋅H -N hydrogen bonding.

Carbon-Phosphorus Coupling from C^N Cyclometalated Au Complexes.

With the aim of exploiting new organometallic species for cross-coupling reactions, we report here on the Au -mediated C -P bond formation occurring upon reaction of C^N cyclometalated Au complexes with phosphines. The [Au(C^N)Cl ] complex 1 featuring the bidentate 2-benzoylpyridine (C N) scaffold was found to react with PTA (1,3,5-triaza-7-phosphaadamantane) under mild conditions, including in water, to afford the corresponding phosphonium 5 through C-P reductive elimination. A mechanism is proposed for the title reaction based on in situ P{ H} NMR and HR-ESI-MS analyses combined with DFT calculations.

Comparative biological evaluation and G-quadruplex interaction studies of two new families of organometallic gold(I) complexes featuring N-heterocyclic carbene and alkynyl ligands.

Experimental organometallic gold(I) compounds hold promise for anticancer therapy. This study reports the synthesis of two novel families of gold(I) complexes, including N1-substituted bis-N-heterocyclic carbene (NHC) complexes of general formula [Au(N1-TBM)]BF (N1-TBM = N1-substituted 9-methyltheobromin-8-ylidene) and mixed gold(I) NHC-alkynyl complexes, [Au(N1-TBM)alkynyl]. The compounds were fully characterised for their structure and stability in aqueous environment and in the presence of N-acetyl cysteine by nuclear magnetic resonance (NMR) spectroscopy.

Mono- and ditopic hydroxamate ligands towards discrete and extended network architectures.

A family of mono- and ditopic hydroxamic acids has been employed in the synthesis and structural and physical characterisation of discrete (0D) and (1- and 2-D) extended network coordination complexes. Examples of the latter include the 1-D coordination polymer {[Zn(ii)(LH)]·2MeOH} (5; LH = 2-(methylamino)phenylhydroxamic acid) and the 2-D extended network {[Cu(ii)(LH)(HO)(NO)]·HO} (5; LH = 4-amino-2-(acetoxy)phenylhydroxamic acid). The 12-MC-4 metallacrown [Cu(ii)(LH)(MeOH)(NO)]·3HO·4MeOH (7) represents the first metal complex constructed using the novel ligand N-hydroxy-2-[(2-hydroxy-3-methoxybenzyl)amino]benzamide (LH).

Crowding out: ligand modifications and their structure directing effects on brucite-like {M(μ-OH)} (M = Co(ii), Ni(ii)) core growth within polymetallic cages.

Previous employment of the ligands 2-methoxy-6-[(methylimino)methyl]phenol (LH) and 2-methoxy-6-[(phenylimino)methyl]phenol (LH) has resulted in the self-assembly of pseudo metallocalix[6]arene complexes of general formulae: [M(μ-OH)(L)](NO) (M = Ni(ii), x = 1, y = 2 (1) and Co(ii/iii), x = 2, y = 3 (2)). Extrapolating upon this work, we report the coordination chemistry of ligands 2-methoxy-6-{[(2-methoxyphenyl)imino]methyl}phenol (LH), 2-[(benzylimino)methyl]-6-methoxyphenol (LH), 2-[(benzylamino)methyl]-6-methoxyphenol (LH) and 2-[(benzylamino)methyl]-4-bromo-6-methoxyphenol (LH), whose structures are modifications of ligands LH. These ligands are employed in the synthesis and characterisation of the dimetallic complex [Ni(ii)(L)(HO)](NO)·2HO·3MeOH (3); the monometallic complexes [Ni(ii)(L)] (4) and [Co(iii)(L)]·HO·MeOH (5a); and the tetranuclear pseudo metallocalix[4]arene complexes: [(NO)⊂Co(ii)(μ-OH)(L)(HO)](NO)·HO (6), [(NO)⊂Ni(ii)(μ-OH)(L)(HO)](NO)·HO (7) and [Ni(ii)(μ-OH)(L)(NO)]·MeCN (8).

The Asymmetric Aza-silyl-Prins Reaction: Synthesis of Enantiopure Piperidines.

The design and development of the first asymmetric aza-silyl-Prins reaction is reported, giving rise to valuable and diverse piperidines and pipecolic acid derivatives in both high yields and as single enantiomers. The creation of a novel chiral auxiliary-homoallylic amine for the aza-silyl-Prins reaction is essential to its success.

Crystal chemistry of mimetite, Pb10(AsO4)6Cl1.48O0.26, and finnemanite, Pb10(AsO3)6Cl2.

The crystal chemistries of synthetic mimetite, Pb(10)(As(5+)O(4))(6)(Cl(2 - x)O(x/2)), a neutral apatite, and finnemanite, Pb(10)(As(3+)O(3))(6)Cl(2), a reduced apatite, were characterized using a combination of X-ray powder diffraction, neutron diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Both phases conform to hexagonal P6(3)/m symmetry; however, the temperature-driven transformation of clinomimetite to mimetite described earlier was not confirmed. The average mimetite structure is best described through the introduction of partially occupied oxygen sites.

Framework 'interstitial' oxygen in La(10)(GeO(4))(5-)(GeO(5))O(2) apatite electrolyte.

Oxygen conduction at low temperatures in apatites make these materials potentially useful as electrolytes in solid-oxide fuel cells, but our understanding of the defect structures enabling ion migration is incomplete. While conduction along [001] channels is dominant, considerable inter-tunnel mobility has been recognized. Using neutron powder diffraction of stoichiometric 'La(10)(GeO(4))(6)O(3)', it has been shown that this compound is more correctly described as an La(10)(GeO(4))(5-)(GeO(5))O(2) apatite, in which high concentrations of interstitial oxygen reside within the channel walls.

Reassessment of large dipole moment enhancements in crystals: a detailed experimental and theoretical charge density analysis of 2-methyl-4-nitroaniline.

The molecular dipole moment of MNA in the crystal has been critically reexamined, to test the conclusion from an earlier experimental charge density analysis that it was substantially enhanced due to a combination of strong intermolecular interactions and crystal field effects. X-ray and neutron diffraction data have been carefully measured at 100 K and supplemented with ab initio crystal Hartree-Fock calculations. Considerable care taken in the measurement and reduction of the experimental data excluded most systematic errors, and sources of error and their effects on the experimental electron density have been carefully investigated.

Enhanced photoluminescence from group 14 metalloles in aggregated and solid solutions.

The unusual photoluminescence characteristics of a series of six group 14 metalloles (1,1-dimethyl-2,3,4,5-tetraphenylmetalloles and 1,1-diphenyl-2,3,4,5-tetraphenylmetalloles) containing silicon, germanium, or tin have been investigated. Although the compounds are weakly luminescent in dilute fluid solution at room temperature, they undergo a substantial enhancement of photoluminescence when forced to aggregate, as in mixed solvent systems. The compounds also exhibit considerable emission when incorporated into rigid room-temperature glasses of sucrose octaacetate.

Hydrogen-bonded polyrotaxane-like structure containing cyclic (H2O)4 in [Zn(OAc)2(mu-bpe)]2.H2O: X-ray and neutron diffraction studies.

The reaction of 4,4'-bipyridylethane (bpe) and 4,4'-dipyridyl disulfide (dpds) with Zn(OAc)2.2H2O has led to the formation of two coordination polymers, [Zn(OAc)2(mu-bpe)].2H2O (1) and [Zn(OAc)2(mu-dpds)] (2).

Neutron Diffraction Study of [Nd(AlMe ) ]⋅0.5 Al Me at 100 K: The First Detailed Look at a Bridging Methyl Group with a Trigonal-Bipyramidal Carbon Atom.

Weak agostic Nd⋅⋅⋅H interactions and Nd-C bonds are involved in the bonding of the bridging methyl groups in the title compound (see sketch on the right): Two of the three H atoms of the methyl group are directed at the Nd center. The C atoms have distorted trigonal-bipyramidal geometry with the Nd atom and one of the H atoms (H ) as axial ligands, and the Al atom and the other two H atoms (H and H ) in equatorial positions. The Al Me "solvate" molecule is disordered.

Syntheses, Spectra, and Structures of (Diphosphine)platinum(II) Carbonate Complexes.

A variety of (diphosphine)platinum(II) carbonate complexes, (LL)Pt(CO(3)), are readily prepared from the corresponding (diphosphine)platinum dichlorides by treatment with silver carbonate in dichoromethane solution provided that water is present. This reaction also permits facile preparation of analogous (13)C-labeled complexes. The carbonate ligands in these complexes have been characterized by IR and (13)C NMR spectroscopy.