Dalton Transactions

doi: 10.1039/b613249apmid: N/A

doi: 10.1039/b613368cpmid: N/A

doi: 10.1039/b613250mpmid: N/A

Itoh, Shinobu; Tachi, Yoshimitsu

doi: 10.1039/b607964dpmid: 17016563

The structure and O-reactivity of a series of copper() complexes supported by the pyridylalkylamine ligands are summarized, and the ligand effects such as the chelate ring size effect (five- six-membered ring), the denticity effect (tetradentate tridentate didentate), the steric effect of 6-methylpyridine and the steric and/or electronic effects of -alkyl substituents are discussed in detail.

Babushkin, Dmitrii E.; Naundorf, Corinna; Brintzinger, Hans H.

doi: 10.1039/b611028mpmid: 17016564

Zirconocenium cations of the type [(MeCH)ZrMe], formed by excess methylalumoxane (MAO) from (MeCH)ZrCl or (MeCH)ZrMe with C-labelled ring ligands, are found to form ion pairs with two types of anions, Me–MAO and Me–MAO, which differ in their coordinative strengths: More strongly coherent ion pairs [(MeCH)ZrMe⋯Me–MAO] are converted to more easily separable ion pairs [(MeCH)ZrMe⋯Me–MAO] by a sufficient excess of MAO. These react with AlMe to form outer-sphere ion pairs containing the cationic AlMe adduct [(MeCH)Zr(µ-Me)AlMe]; formation of the more easily separable ion pairs might be required also for polymerisation catalysis.

Kállay, Csilla; Várnagy, Katalin; Malandrinos, Gerasimos; Hadjiliadis, Nick; Sanna, Daniele; Sóvágó, Imre

doi: 10.1039/b608190hpmid: 17016565

Copper() complexes of the pentapeptides Ac-HisAlaHisValHis-NH, Ac-HisValHisAlaHis-NH, Ac-HisProHisAlaHis-NH, Ac-HisAlaHisProHis-NH, Ac-HisGlyHisValHis-NH and Ac-HisValHisGlyHis-NH have been studied by potentiometric, UV-Vis, CD and EPR spectroscopic methods. It has been found that the pentapeptides are efficient ligands for the complexation with copper() and exhibit an outstanding versatility in the co-ordination geometry of complexes. The presence of three histidyl residues provides a high possibility for the formation of macrochelates the exclusive binding of imidazole-N donor atoms. The macrochelation suppresses, but cannot preclude the deprotonation and metal ion co-ordination of amide functions and the species [CuHL] and [CuHL] predominate at physiological pH in equimolar solutions and in the presence of excess metal ions, respectively. It is also clear from the data that both C-terminal and internal histidyl residues can work as the anchoring sites for metal binding and subsequent amide deprotonation resulting in the formation of co-ordination isomers and dinuclear species in equimolar solutions and in the presence of excess metal ions, respectively. In more alkaline solutions (pH ∼10) a third amide function can be deprotonated and co-ordinated in the species [CuHL] with (N,N,N,N) co-ordination. The dinuclear species [CuHL] and [CuHL] containing hydroxide ions and/or imidazolato bridges are formed at high pH in the presence of excess of metal ions. The insertion of one proline into the sequence preceding histidyl residues hinders the deprotonation of amide functions at that site and the formation of only mononuclear complexes was observed with these peptides.

Gannaz, Benoît; Antonio, Mark R.; Chiarizia, Renato; Hill, Clément; Cote, Gérard

doi: 10.1039/b609492apmid: 17016566

The coordination of the trivalent 4f ions, Ln = Nd, Eu and Yb, as well as the trivalent 5f ion, Am, with diamide and dialkylphosphoric acid extractants, individually and in combination, was studied by use of X-ray absorption spectroscopy. These studies provide metrical information about the interatomic interactions between the f-ions (M) and the ligands, dihexylphosphoric acid (HDHP) and ,′-dimethyl-,′-dioctylhexylethoxymalonamide (DMDOHEMA), that is of practical relevance to the control of metal–ligand binding in liquid–liquid extraction systems for the separation of trivalent actinide ions, An, from trivalent lanthanide ions, Ln. Through systematic variations of extraction conditions and extractant combinations, we have found that the HDHP complexes with M involve MO coordination and distant M⋯P interactions, whereas the DMDOHEMA complexes with M involve MO coordination. The combination of the EXAFS results with ancillary extraction data and IR results facilitates descriptions of the stoichiometries and structures of the molecular species formed in solution upon liquid–liquid extraction and leads to a new understanding of the binary extraction systems in terms of the strength and selectivity of An- Ln-ligand interactions. This fundamental structure information affords insight into solvent extraction processes that are of contemporary and practical importance in heavy element chemistry and to environmentally related issues arising from the separation and disposal of radioactive materials, particularly actinides and selected fission products, in the field of nuclear waste reprocessing research.

Wu, Chuan-De; Lin, Wenbin

doi: 10.1039/b606817kpmid: 17016567

Six homochiral coordination polymers based on an enantiopure elongated and bent bipyridine ligand were synthesized and characterized by single-crystal X-ray diffraction studies. The framework structures of all six compounds were built up from similar 1D polymeric chains composed of 46-membered metallomacrocycles. Four distinct packing patterns were observed for this family of coordination polymers. With the exception of , the anions do not coordinate to the metal centers and reside in the open channels. Single-crystal X-ray diffraction studies show that the structures of these coordination polymers are sensitive to the anions even though they do not coordinate to the metal centers. The framework structures are somewhat tolerant of the change of metal centers and their local coordination environments. Gas sorption measurements on suggest that chiral porous solids can be obtained with the present 1D coordination polymeric building blocks.

Farrer, Nicola J.; McDonald, Robert; McIndoe, J. Scott

doi: 10.1039/b609561epmid: 17016568

Attachment of a proton sponge to a phosphine ligand renders neutral complexes of the ligand highly amenable to analysis by electrospray ionisation mass spectrometry (ESI-MS). The ligand 1,8-bis(dimethylamino)naphthyldiphenylphosphine () is extremely efficient and highly selective in forming exclusively [M + H] ions, which may be detected at very low concentration. Ionisation efficiency of in the presence of H approached 100%. The bis-substituted ligand bis{1,8-bis(dimethylamino)naphthyl}phenylphosphine () was also prepared and characterised, as were Fe(CO)- (), Mn(η-CHMe)(CO)- () and W(CO)- () complexes of . Compounds , ·HBr·EtOH, and were all structurally characterised.

Raubenheimer, Helgard G.; Esterhuysen, Matthias W.; Frenking, Gernot; Timoshkin, Alexey Y.; Esterhuysen, Catharine; Horvath, Ulrike E. I.

doi: 10.1039/b607613kpmid: 17016569

Deprotonated Fischer-type aminocarbene complexes, (CO)MC(NR)CH (M = Cr or W; R = Me or propyl), react with PhPAu by metal group substitution – (CO)M for PhPAu– and attachment of the extricated M(CO) to the deprotonated methyl group. (The products may also be seen as aminovinylgold compounds coordinated to M(CO) moieties.) DFT calculations at the B3LYP level of theory using model compounds indicate a clear preference of the gold unit for central C to terminal coordination in the ligand [NMeCCH], whereas the Cr(CO) has a 7 kcal mol preference for C(vinyl) coordination compared to N-coordination. In related thiocarbenes, the sulfur donor atom should be the preferred point of attachment for the metal carbonyl unit. The latter prediction is borne out in practice, and in the three products isolated, including PhPAu{C(CH)SPh}Cr(CO) in a mixed crystal with [PhPAuSPh]Cr(CO), precisely this coordination mode is present. The latter component of the mixed crystal has also been prepared independently of the vinyl one.