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Boydston, Andrew J.; Bielawski, Christopher W.
doi: 10.1039/b607696npmid: 16924285
The synthetic and structural progression surrounding -heterocyclic carbenes has given rise to great functional and architectural diversity in organometallic chemistry, catalysis, and materials science. The development of new, modular scaffolds for bridging transition metals is essential in order to expand the boundaries of these scientific areas. This Frontier article summarizes recent advances in the synthesis and study of ditopic ligands displaying two linearly opposed carbene moieties and emphasizes their versatility in the preparation of new organometallic and macromolecular materials. The conclusion previews their utility in conjugated organic/inorganic hybrid materials with potential applications in the emerging fields of molecular- and nanoelectronics.
Adams, Christopher J.; Crawford, Paul C.; Guy Orpen, A.; Podesta, Thomas J.
doi: 10.1039/b604319dpmid: 16924286
A series of crystalline salts based on the [M(dto)] (dto = 1,2-dithiooxalate, M = Ni, Pt, Cu) dianion with hydrogen-bond donor cations have been synthesised following a molecular tectonics approach. The chelating M(dto)⋯HN supramolecular synthon has been exploited in a systematic study of its robustness. The effects of competition between hydrogen-bond acceptors, of the shape and functionality of the cations and of varying the metal in the anion are discussed. The preparation and structural characterisation of the new crystalline phases [4,4′-Hbipy][Pt(dto)] (), [HNCHCOH-4][Pt(dto)] (), [HNCHCOH-3][Pt(dto)] (), [HNCHCHCOH-4][Ni(dto)] (), [HNCHCHCOH-3][Ni(dto)] (), [HNCHCONH-4][Ni(dto)] (), [HNCHCHNOH-4][Ni(dto)] (), [HNCHCHNOH-3][Ni(dto)] (), [4,4′-Hbipip][Ni(dto)] (), [HNCHCOH-4][Pt(dto)] (), [HNCHCOH-4][Cu(dto)] (), [HNCHCOH-3][Ni(dto)][HO] (), [HNCHCOH-3][Pt(dto)][HO] (), [HNCHCOH-3][Cu(dto)][HO] (), [H(Me)NCHCOH-4][Ni(dto)][HO] () is reported. The charge-assisted NH⋯dto synthon is formed in each of compounds , and is apparently much more robust than the conventional synthons used (such as the carboxylic acid dimer), which have a much lower rate of occurrence. The NH⋯dto synthon may be generalised to 3- and 4-pyridinium species and 3- and 4-piperidinium derivatives. In the latter cases branching of the hydrogen-bond networks through the NH groups arises. The robustness of the NH⋯dto synthon allows structures of the form [NH cation][M(dto)] to be regarded as being formed by the packing of neutral supermolecules. Cases of isomorphism (as in ) and latent polymorphism ( in and ) are noted.
Bettencourt-Dias, Ana de; Viswanathan, Subha
doi: 10.1039/b606970cpmid: 16924287
In our pursuit of luminescent lanthanide ion-based coordination polymers, we have isolated several complexes with nitrobenzoic acid ligands and characterized these by X-ray crystallography and luminescence spectroscopy. 2-Nitrobenzoic acid reacts with Eu() to form , which crystallizes in the -1 space group, with = 12.385(3), = 12.912(3), = 17.889(4) Å, = 97.49(3), = 109.64(3) and = 101.99(3)°. 3-Nitrobenzoic acid forms a one-dimensional coordination polymer with Eu(), , which crystallizes in the triclinic space group -1 with = 9.7100(19), = 10.579(2), = 13.361(3) Å, = 77.41(3), = 88.78(3) and = 88.16(3)°. Structures and correspond to the isostructural one-dimensional coordination polymers of Eu() and Tb(), respectively, with the 4-nitrobenzoato anion. These crystallize in the triclinic space group -1 with = 9.2242(18), = 15.102(3), = 18.587(4) Å, = 75.93(3), = 82.88(3) and = 79.00(3)° for and = 9.2692(19), = 15.369(3), = 18.353(4) Å, = 75.37(3), = 81.32(3) and = 78.15(3)° for . Potentiometry, absorption and NMR spectroscopy indicate that in solution only 1 : 1 species are present. All compounds are weakly luminescent as solids and the photophysics of solutions of ligands with Ln() in 1 : 1 stoichiometry were studied. Quantum yields around 1 and 3% for Eu()-and Tb()-containing methanolic solutions were measured.
José Calhorda, Maria; Costa, Paulo J.; Crespo, Olga; Gimeno, M. Concepción; Jones, Peter G.; Laguna, Antonio; Naranjo, Mar; Quintal, Susana; Shi, Yu-Jun; Villacampa, M. Dolores
doi: 10.1039/b605034d
Copsey, May C.; Chivers, Tristram
doi: 10.1039/b606527apmid: 16924289
The lithium (imido)diphosphineimide Li(EtO)[DippNPhP–P(Bu)PhNDipp] () (Dipp = 2,6-PrCH) undergoes simple metathesis reactions with equimolar amounts of zinc halides, ZnCl and BuZnBr, to give the respective N,N′-chelated complexes {Zn(μ-Cl)[DippNPhP–P(Bu)PhNDipp]} () and BuZn[NDippPhP–P(Bu)PhNDipp] (). In contrast, the reaction of two equivalents of complex with HgCl affords the rearranged bis(imidodiphosphinoamine) complex, Hg[PhP(NDipp)(μ-NDipp)P(Bu)Ph] (), where the ligand acts as a P-centered anion. The (imido)diphosphineimide backbone of remains intact on oxidation with elemental sulfur to afford the lithium (imido)diphosphineimine sulfide complex, Li(EtO)[DippNPhP(S)–P(Bu)PhNDipp] (). Reactions of with group 12 metal halides show similar behaviour to those of complex . The N,N′ chelated metathesis products RZn[DippNPhP(S)–P(Bu)PhNDipp] (, R = Cl; , R = Bu) are obtained on reaction with ZnCl and BuZnBr, respectively. Isomerization of the ligand backbone occurs on reaction of with HgCl to form the homoleptic P,S-chelated mercury complex Hg[Ph(S)P(NDipp)(μ-NDipp)P(Bu)Ph] (). Complexes , , , , and have been characterized by X-ray crystallography.
Guerra, Krassimira P.; Delgado, Rita; Drew, Michael G. B.; Félix, Vítor
doi: 10.1039/b603484epmid: 16924290
New -(3-aminopropyl) (L, L) and (2-cyanoethyl) (L, L) derivatives of a 14-membered tetraazamacrocycle containing pyridine have been synthesized. The protonation constants of L and L and the stability constants of their complexes with Ni, Cu, Zn and Cd metal ions were determined in aqueous solutions by potentiometry, at 298.2 K and ionic strength 0.10 mol dm in KNO. Both compounds have high overall basicity due to the presence of the aminopropyl arms. Their copper() complexes exhibit very high stability constants, which sharply decrease for the complexes of the other studied metal ions, as usually happens with polyamine ligands. Mono- and dinuclear complexes are formed with L as well as with L, but the latter exhibits mononuclear complexes with slightly higher values while the dinuclear complexes of L are thermodynamically more stable. The presence of these species in solution was supported by UV-VIS-NIR and EPR spectroscopic data. The single crystal structures of [Cu(HL)(ClO)] and [CoLCl] revealed that the metal centres are surrounded by the four nitrogen atoms of the macrocycle and one monodentate ligand, adopting distorted square pyramidal geometries. In the [CoLCl] complex, the macrocycle adopts a folded arrangement with the nitrogen atom opposite to the pyridine at the axial position while in the [Cu(HL)(ClO)] complex, the macrocycle adopts a planar conformation with the three aminopropyl arms located at the same side of the macrocyclic plane.
Anderson, Carly E.; Apperley, David C.; Batsanov, Andrei S.; Dyer, Philip W.; Howard, Judith A. K.
doi: 10.1039/b605995cpmid: 16924291
A straightforward methodology for the high-yielding synthesis of the di-functionalised phosphines {PhP(CH)NCHE, E = NMe (), O (), S ()}base-catalysed Michael addition is described. Reaction of the functionalised tertiary phosphines with PdCl(MeCN) affords complexes in which the ligands are bound in a tridentate fashion, namely [PdCl(κ-PNE)]Cl (, ) as the predominant products. A κ-PN coordination mode was also identified crystallographically for ligand following its reaction with PdCl(MeCN), which afforded [PdCl(-κ-PN)] () in 5% yield. Conductivity studies of solutions of are consistent with an ionic formulation, however the poor solubility of and precluded their study in a similar fashion. Analysis of bulk samples of [PdCl()] () and [PdCl()] () by N and P NMR spectroscopy in the solid state as consistent with exclusive tridentate binding of the PNE ligands. An X-ray crystallographic study has probed the coordination of in the unusual salt [PdCl(-κ-PNN)][Mg(SO)(OH)] () prepared by treating a methanolic solution of with excess MgSO. No data could be obtained to support the transformation of into on addition of excess chloride. In contrast, reacts regioselectively with the water-soluble phosphine CyPCHCHNMeCl to afford the -diphosphine complex -[PdCl(CyPCHCHNMeCl)(-κ-PN)]Cl (). Reaction of with PdCl(Me)(COD) results in the formation of the κ-PN dichloride complex [PdCl(Me)(-κ-PN)] (). Attempts to prepare [Pd(Me)(MeCN)(-κ-PN)][PF] () through reaction of with NaPF in MeCN led to decomposition. Treatment of PdMe(TMEDA) with at low temperature initially affords [PdMe(-κ-NN)], which isomerises to afford [PdMe(-κ-PN)] (); at temperatures greater than 10 °C complex decomposes rapidly.
Hitchcock, Peter B.; Lappert, Michael F.; Sablong, Rafaël
doi: 10.1039/b601881epmid: 16924292
A number of metal complexes containing one of the following ligands: the 1-azaallyl [N(R)C(Ph)C(H)R] (L), the 1,3-diazaallyl(≡ LL′) and the isomeric β-diketiminate [{N(R)C(Ph)]}CH] (≡ LL) have been prepared (R = SiMe). These are the crystalline compounds H(LL) (), Na(LL) (), [Na(LL)(thf)] (), Na(L) (), [Na(µ-LL′)] (), [K(µ-L)(η-CH)] (), [K(µ-LL′)(thf)] (), [K(thf)(µ-LL)] () and [Ni(LL′)] (). A new synthesis of Na[C(H)R] () involved Hg[C(H)R] and Na/Hg as reagents. The β-diketimine was obtained from Li(LL) and cyclopentadiene. Under different conditions compounds , and were isolated from and benzonitrile, and compounds , and from K[C(H)R] and PhCN. Complex was derived from [Li(LL′)] and [NiBr(dme)]. The solution obtained from + 2 PhCN in EtO at ambient temperature was a mixture () of (predominantly) and . The 1-azaallyl complex has the ligand bound to the metal as the enamide, and this is also probably (NMR) the case for . The molecular structures of the crystalline complexes , and are presented; that of was published earlier. Compound , a cyclooctamer, is particularly interesting, in that each LL′ ligand is bridging one of its N atoms to two neighbouring sodium ions and is not only N,N′- but also (η-CC)-chelating to one of them.
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The complexation properties of the ligand bis(3,5-dimethylpyrazol-1-yl)methane () towards group 11 metals have been studied. The reaction in a 1 : 1 molar ratio with [Cu(NCMe)]PF or Ag(OTf) complexes gives the mononuclear [CuL(NCMe)]PF (), with crystallographic mirror symmetry, or dinuclear [Ag(µ-L)](OTf) () (OTf = trifluoromethanesulfonate) in which the ligand bridges both silver centres, an unprecedented mode of coordination for this type of ligands. Compound crystallizes with two water molecules and forms a supramolecular structure through classical hydrogen bonding. The reaction in a 2 : 1 ratio affords in both cases the four-coordinated derivatives [ML]X (M = Cu, X = PF (); Ag, X = OTf ()). The treatment of [Ag(OTf)(PPh)] with the ligand L gives [AgL(PPh)]OTf (). The gold() derivative [Au(CF)(µ-L)] () has also been obtained by reaction of L with two equivalents of [Au(CF)(tht)]. These complexes present a luminescent behaviour at low temperature; the emissions being mainly intraligand but enhanced after coordination of the metal. Compounds have been characterized by X-ray crystallography. DFT studies showed that, in the silver complex , coordination of HO to Ag in the binuclear complex is favoured by formation of a hydrogen-bonding network, involving the triflato anion, and releasing enough energy to allow distortion of the Ag framework.