Dalton Transactions Blog

In this HOT article, Layfield and coworkers have studied the reactions of the heteroleptic lithium amide [Li₃(μ-hmds)₂(μ,μ-hpp)], where [hmds]^– =
hexamethyldisilazide and [hpp]^– = hexahydropyrimidopyrimidide, with MnCl₂, CoCl₂ or ZnBr₂ resulting in the formation of the separated ion-pairs [MLi₇(μ₈-O)(μ,μ-hpp)₆]+[A]^–, which each consists of a {MLi₇} oxo-centred cube structural motif (M = Mn, Co, Zn), with each face of the cube being bridged by an [hpp]^– ligand. The method potentially could permit access to a range of cage compounds with magnetic properties that are influenced by μ-amido ligands rather than by μ-(O-donor) ligands.

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Synthesis and structure of cationic guanidinate-bridged bimetallic {Li₇M} cubes (M = Mn, Co, Zn) with inverse crown counter anions
Daniel Woodruff, Michael Bodensteiner, Daniel O. Sells, Richard. E. P. Winpenny and Richard A. Layfield
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10999E

In this HOT article, Yuliang Li and coworkers synthesized p–n axial heterojunction inorganic/organic semiconductor nanowire arrays on porous anodic aluminum oxide (AAO) templates via electrochemical deposition. This novel synthesis is based on a common concept of using an AAO template. The electrical properties of the heterojunctions of these organic–inorganic materials were investigated, indicating a diode nature and a rectifying feature. These heterojunction nanowire arrays are at the frontier of the materials field, for next-generation electrical and optoelectronic devices.

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Synthesis and characterization of axial heterojunction inorganic–organic semiconductor nanowire arrays
Nan Chen, Xuemin Qian, Haowei Lin, Huibiao Liu, Yongjun Li and Yuliang Li
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10926J

The formation of peptide or protein aggregates is a common feature of many different forms of neurodegenerative disorders including Alzheimer’s disease, Parkinson’s disease and prion diseases. It is also widely accepted that various metal ions can play a significant role in the conformational changes of these peptides/proteins.

In this HOT article, Kállay and co-workers report on the synthesis and study of the copper complexes of rIAPP fragments. First of all the terminally protected tridecapeptide rIAPP(17–29) was investigated in which the potentially metal binding amino acid residues are located in the N-terminus. The surprisingly high affinity of this peptide towards complexation with copper(II) promoted a systematic study on the shorter fragments including rIAPP(17–22) (Ac-VRSSNN-NH₂), rIAPP(17–20) (Ac-VRSS-NH₂), its mutant peptides (Ac-VASSNH₂ and Ac-VRAA-NH₂) and rIAPP(19–22) (Ac-SSNN-NH₂). The peptides can be classified into two different categories: (i) the tetrapeptides Ac-VRSS-NH₂, Ac-VASS-NH₂ and Ac-VRAA-NH₂ can interact with copper(II) only under strongly alkaline conditions (pH > 10.0) and the formation of only one species with four amide nitrogen coordination can be detected; (ii) the peptides Ac-VRSSNNLGPVLPP-NH₂, Ac-VRSSNN-NH₂ and Ac-SSNN-NH₂ can form complexes above pH 6.0 with the major stoichiometries [CuH₋₂L], [CuH₋₃L]⁻ and [CuH₋₄L]²⁻. The data supports the idea that  rIAPP(17–29) can interact with copper(II) ions under physiological conditions and the SSNN tetrapeptide fragment can be considered as the shortest sequence responsible for metal binding.

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Copper(II) complexes of rat amylin fragments
Csilla Kállay, Ágnes Dávid, Sarolta Timári, Eszter Márta Nagy, Daniele Sanna, Eugenio Garribba, Giovanni Micera, Paolo De Bona, Giuseppe Pappalardo, Enrico Rizzarelli and Imre Sóvágó
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10835B

This HOT article describes the synthesis and crystal structures of four mono- or bi-cyclic Mo/S/Cu clusters from a pre-designed cluster [(η⁵-C₅Me₅)₂Mo₂(µ₃-S)₄(CuMeCN)₂]²⁺ with tetraphosphine or N,P mixed ligands.  The femtosecond third order non-linear optical (NLO) performances of the products are enhanced due to the increased number of cluster cores.  As both the cluster-based building blocks and the multiple organic linkers are pre-designed, it could be useful for the rational design and assembly of coordination frameworks, possibly allowing the preparation of other new materials with enhanced NLO performance.

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Assembly of bicyclic or monocyclic clusters from [(η⁵-C₅Me₅)₂Mo₂(µ₃-S)₄(CuMeCN)₂]²⁺ with tetraphosphine or N,P mixed ligands: syntheses, structures and enhanced third-order NLO performances
Zhi-Gang Ren, Sha Sun, Min Dai, Hui-Fang Wang, Chun-Ning Lü, Jian-Ping Lang and Zhen-Rong Sun
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10685F

In this HOT article, Harder and Spielmann describe some alkaline earth metal aminoborane ligands and their thermal behaviour.  By using their new ditopic bis(ketiminate) ligands, they have been able to synthesize binuclear complexes that are pre-organised for constructing bridging aminoborane oligomers as ligands. By heating the initial non-bridging complexes, the aminoboranes couple and lose H₂. The loss of hydrogen from aminoborane ligands has practical relevance to hydrogen storage chemistry and also to the fields of solid state and metal-organic chemistry.

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Binuclear magnesium amidoborane complexes: characterization of a trinuclear thermal decomposition product
Jan Spielmann and Sjoerd Harder
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10694E

In this HOT article,  Fornies and co-workers describe the efficient stereoselective synthesis of salts of any of the following trifluoromethylplatinum(IV) isomeric couples: cis-/trans-[Pt(CF₃)₄Cl₂]^2- and fac-/mer-[Pt(CF₃)₃Cl₃]^2-. All these compounds can be isolated in high yields and have been characterised by a combination of analytical, spectroscopic and X-ray diffraction methods.

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Efficient and stereoselective syntheses of isomeric trifluoromethyl-platinum(IV) chlorides
Sonia Martínez-Salvador, Pablo J. Alonso, Juan Forniés, Antonio Martín and Babil Menjón
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10557D

In this HOT article, Ribas and co-workers build on previous studies on the mechanism of Ullmann cross coupling reactions using a well-defined aryl-copper(III) complex. Fundamental mechanistic knowledge of these couplings is still scarce but is gaining renewed interest due to the cost and toxicity benefits in comparison to Pd-based methodologies for the synthesis of key intermediates in the pharmaceutical industry. The reactivity of well defined aryl–Cu^III species in front of phenol-type nucleophiles was found to differ substantially from the reactivity with corresponding phenolates, and a significant enhancement was found to produce the same aryl–O coupling product. Mechanistic studies showed that easy deprotonation of coordinated secondary amines was responsible for the intense LMCT band at 545 nm; indeed, this pH-dependent reactivity of the pincer-like coordinated ligand somewhat enhanced its reactivity.

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Aryl–O reductive elimination from reaction of well-defined aryl–Cu^III species with phenolates: the importance of ligand reactivity
Alicia Casitas, Nikolaos Ioannidis, George Mitrikas, Miquel Costas and Xavi Ribas
Dalton Trans., 2011, Advance Article
DOI: 10.1039/C1DT10428D