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Alcock NW Clarkson G Glover PB Lawrance GA Moore P Napitupulu M 《Dalton transactions (Cambridge, England : 2003)》2005,(3):518-527
The potentially pentadentate ligand 2,6-bis[N-(2'-pyridylmethyl)carbamyl]pyridine (H2L1), readily prepared from reaction of a diester of pyridine-2,6-dicarboxylic acid (H2dipic) and 2-aminomethylpyridine (ampy), shows limited tendency to form 1:1 M:L complexes with labile metal ions, although [CuL1] and [NiL1] were observed as minor species, the latter characterized by a crystal structure analysis. A mononuclear complex formed with inert Co(III) was characterized by a crystal structure as the neutral 1:2 complex [Co(L1)(HL1)] with two ligands acting as tridentate ligands, one coordinated by the central pyridine and its two flanking deprotonated amido groups, and the other by the central pyridine, one amido and one terminal pyridine group, with the remaining poorly coordinating protonated amide remaining unbound along with other terminal pyridine groups. Fe(III) is known to form a symmetrical 1:2 complex, but that complex is anionic due to binding of all four deprotonated amido groups; the unsymmetrical neutral Co(III) complex converts into a symmetrical anionic species only on heating for hours in aqueous base in the presence of activated carbon. The most remarkable tendency of H2L1, however, is towards the formation of robust double helical complexes: a dinuclear Cu(II) complex [Cu2L1(2)] forms, as well as a trinuclear Ni(II) complex [Ni(3)(L1)2(OAc)2(MeOH)2]. Moreover, in the presence of added H2dipic, the tetranuclear complex [Cu4(L1)2(dipic)2(OH2)2] is obtained. All helical complexes have been characterized by X-ray crystal structure analyses, and all crystals feature a racemic mixture of left- and right-handed double helices stabilized by inter-ligand pi-stacking (inter-ring distances of 3.2-3.8 A) of ligands which each span several metal ions. Using the chelating ligand pentane-2,4-dione (acac), each of the two pairs of adjacent monodentate ligands in [Ni3(L1)2(OAc)2(OH2)2] have been shown to be available for substitution without destroying the helical structure, to form [Ni3(L1)2(acac)2], also characterized by a crystal structure. 相似文献
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Mery Napitupulu Monica Rossignoli Geoffrey A. Lawrance Marcel Maeder Peter Turner 《Transition Metal Chemistry》2007,32(3):287-291
Reaction of [Mo(CO)3(3-azahexane-1,6-diamine)] with formaldehyde and the carbon acid nitroethane leads to cyclisation involving one terminal amine
and either the internal secondary amine (minor product) or the other terminal primary amine (major product), with zinc/acid
reduction yielding new cyclic tetraamines, also characterised as their cobalt(III) complexes. This is the first example of
Mannich-style formation of a pendant-arm triazamacrocycle around a molybdenum(0) template. The unexpected N-(1′-aminopropyl)-6-methyl-1,4-diazacycloheptan-6-amine minor product has been characterised by an X-ray structure as its
cis-dichlorocobalt(III) complex. 相似文献
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Possession of a unique nonidentity commutator/associator is a property that dominates the theory of loops whose loop rings, while not associative, nevertheless satisfy an “interesting” identity. For instance, until now, all loops with loop rings satisfying the right Bol identity (such loops are called SRAR) have been known to have this property. In this paper, we present various constructions of other kinds of SRAR loops. 相似文献
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Summary An RA loop is a (necessarily Moufang) loop whose loop rings in any characteristic are alternative, but not associative. There
are seven classes of finite indecomposable RA loops. In this paper, we find the indecomposable subloops and the indecomposable
nonabelian groups which can appear inside the loops in each class. 相似文献
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