ALBERT

Description: In whatever state of bonding – whether covalent to an organic residue or a heteroatom, or polar to ionic in contact with a metal – the azide moiety N 3 is characterized by its high potential of reactivity which essentially manifests itself in two basic processes: the elimination of dinitrogen and the entry into 1, 3-dipolar cycloadditions with suitable dipolarophiles, the latter of which clearly predominates the chemistry of azide, also that of its metal compounds. In a preceding review entitled “Part I – Metal Azides: Overview, General Trends and Recent Developments” which was meant to lay the foundations for the present paper, these and other reactions have already been touched upon. The present review – Part II – now focusses in great detail on the formation of five-membered heterocycles – tetrazol(at)es, triazol(at)es, triazolin(at)es, thiatriazol(at)es, etc. as well as various consecutive products – from azide and nitriles, isocyanides, alkynes, alkenes and heteroallenes (CS 2 , RN=C=S) in the ligand sphere of the metal. Generally, these [3+2]-cycloadditions are found to proceed under much milder conditions in comparison with the strictly organic case whose triumphant progress since the 1960s is intimately bound up with the name of Huisgen. Mechanistic considerations on the matter are presented. A secondary aspect still occupying quite a part of the discussion is concerned with the role of metals in [3+2]-cycloadditions particularly of the highly topical “click”-type, e.g. (CuAAC), (RuAAC). Likewise, a short chapter deals with the question of pentazol(at)e (N 5 – ) which according to numerous theoretical studies could well be stabilized and isolated in combination with metals, e.g., in the form of azametallocenes. A last chapter is devoted to a cursory survey of related systems, in particular fulminato complexes, metall o nitrile ylides and metall o nitrile imines, in which the metal acts as a substituent on the 1, 3-dipole (metall o -1, 3-dipole). Other systems with a metal substituent on the dipolarophile (metall o -dipolarophile), or, with metal itself in the three- (two-) atom arrangement constituting the dipole (dipolarophile) [metall a -1, 3-dipole, metall a -dipolarophile] are only quoted by way of example.

Description: The organically-templated uranyl selenite, (H 2 en)[(UO 2 )(SeO 3 )(HSeO 3 )](NO 3 ) · 0.5H 2 O ( 1 ) (en = 1,2-ethylenediamine) was synthesized and characterized by elemental analyses, IR spectroscopy, TG, and single-crystal X-ray diffraction. Compound 1 crystallizes in the orthorhombic system, space group Pbca , with a = 13.170(3) Å, b = 11.055(2) Å, c = 18.009(4) Å, V = 2621.8(9) Å 3 , M = 1316.19, Z = 4, D cal = 3.334 g · cm –3 , μ (Mo- K α ) = 17.998 mm –1 , GOF = 1.059, R 1 = 0.0263, wR 2 = 0.0532 [ I 〉2 σ ( I )]. The X-ray diffraction analysis reveals that compound 1 has a three-dimensional (3D) supramolecular structure. It contains negatively charged [UO 2 (HSeO 3 )(SeO 3 )] – inorganic anion layers and is balanced by [H 2 en] 2+ cations and NO 3 – anions located in the interlayers. Furthermore, the photoluminescence properties of 1 were investigated.

Description: The cover picture shows two types of the phosphanegold(I) cluster cations and Keggin polyoxometalate (POM) anions coordinated by two mononuclear phosphanegold(I) cations. These intercluster compounds are formed during carboxylate elimination of monomeric phosphanegold(I) carboxylate precursors in the presence of the POM. The structures of phosphanegold(I) cluster cations show different dimerization arrangements by inter-cationic aurophilic interactions in crossed-edge arrangement (tetrahedral Au 4 structure) or parallel-edge arrangement (rectangular Au 4 structure). This structural difference depends upon the p -substituent, F or Cl, on the aryl group of the triarylphosphanes. Mononulcear phosphanegold(I) cations linked to the POM indicate a transient state in the formation of the phosphanegold(I) cluster cations. More details are discussed in the article by K. Nomiya et al. on pp. 1688ff.

Description: Deprotonation of 1,2-bis(neopentylamino)benzene ( 1 ) with an excess of KH in tetrahydrofuran (thf) yields the singly metalated derivative [(thf)K{C 6 H 4 -1-(NH-CH 2 t Bu)-2-(N-CH 2 t Bu)}] ( 2a ). Performance of the metalation reaction in tetrahydropyran (thp) leads to formation of [(thp) 2 K{C 6 H 4 -1-(NH-CH 2 t Bu)-2-(N-CH 2 t Bu)}] ( 2b ). The second amino group of 2a can be lithiated by butyllithium yielding heterobimetallic [(thf) 2 LiK{C 6 H 4 -1,2-(N-CH 2 t Bu) 2 }] ( 3 ). The structures demonstrate that ethers as well as aromatic π systems represent suitable bases for the rather soft potassium ions. Intermolecular potassium π interactions lead to the formation of strands in the crystalline state. For complex 2a , a dynamic exchange process of the N-bound hydrogen atom with an energy barrier of 45.6 kJ · mol –1 is observed in [D 8 ]THF solution. Heterobimetallic 3 also shows a temperature-dependent dynamic behavior that gives rise to splitting of the methylene and aromatic resonances suggesting overlying metal exchange and aggregation equilibria.

Description: Abstract. Three cyanide-bridged compounds Zn(4, 4′-bpy)(H 2 O) 2 M (CN) 4 (4, 4′-bpy = 4, 4′-bipyridine; M = Ni ( 1 ), Pd ( 2 ), Pt ( 3 )) were synthesized by self-assembly of Zn 2+ ions, pillar ligands 4, 4′-bpy and [ M (CN) 4 ] 2– . Single-crystal X-ray diffraction analysis revealed that compounds 1 – 3 are isostructural and belong to monoclinic space group C 2/ c . The zinc atom is located in a distorted octahedral arrangement, whereas the central nickel atom adopts square-planar arrangement. The central Zn and Ni atoms are linked alternatingly through two cis cyanide groups, generating zigzag chains. The adjacent chains are further connected along two different directions by 4, 4′-bpy ligands to form a three-dimensional framework. Thermal expansion (TE) analyses of compounds 1 – 3 showed that both a and c axes are positive TE coefficients, compared to the near zero TE one along the b axis.

Description: The title compound Ca 3 [BN 2 ]I 3 was obtained from reactions of mixtures of the starting materials Ca 3 [BN 2 ] 2 and CaI 2 in a 1:4 ratio in sealed Nb tubes at 1223 K. The crystal structure was solved from powder synchrotron diffraction data. Ca 3 [BN 2 ]I 3 is the first example of a halide-rich nitridoborate crystallizing in the rhombohedral space group R 32 [no. 155, Pearson code: hR 96; Z = 12; a = 16.70491(2) Å, c = 12.41024(2) Å]. The crystal structure is built up by two interpenetrating networks of condensed edge-sharing [BN 2 ]@Ca 6 and [□]@I 6 trigonal antiprisms (□ = void). In Ca 3 [BN 2 ]I 3 two crystallograhically distinct [BN 2 ] 3– anions are present with d (B1–N) = 1.393(2) Å and d (B2–N) = 1.369(9) Å. Their bond angles are practically linear, varying only slightly: N–B1–N = 179(1)° and N–B2–N = 180°. Vibrational spectra were interpreted based on the D ∞ h symmetry of the discrete linear [N–B–N] 3– moieties, considering the site symmetry reduction and the presence of two distinct [BN 2 ] 3– groups.

Description: Three complexes [Ca(ClO 4 )(H 2 O)Cu 5 (o-picHA-2H) 5 (H 2 O)]ClO 4 ( 1 ), [Pr(NO 3 ) 2 (py)Cu 5 (o-picHA-2H) 5 (py) 5 ]ClO 4 ( 2 ), and [Nd(NO 3 )(H 2 O)(py)Cu 5 (o-picHA-2H) 5 (py) 5 ](ClO 4 ) 2 · 5py ( 3 ) ( o -picHA = 2-picolinehydroxamic acid) were synthesized in order to retrace structural trends caused by the change of the ionic radius of the central metal ion as well as to assess the effect of the axial ligands on the arrangement of metallacrowns. The complexes were characterized by elemental analysis, ESI-mass spectrometry, IR spectroscopy, and single-crystal X-ray analysis. The heterometallic complexes have 15-MC-5 molecular topology with Ca II or Ln III ion in the center of the metallamacrocyclic cavity. The Ca–O and Ln –O bond lengths follow the trend of changes of the corresponding metal ionic radii. While the Ca II complex cation (without axial ligands) in 1 is almost flat, the Ln III containing cations in 2 and 3 have a “partially opened umbrella“ environment.

Description: Cadmium(II) based 2D coordination polymer [Cd(L1) 2 (DMF) 2 ] ( 1 ) (L1 = 4,5-dicyano-2-methylimidazolate, DMF = N,N ′-dimethylformamide) and 2D cobalt(II)-imidazolate framework [Co(L3) 4 ] ( 2 ) (L3 = 4,5-diamide-2-ethoxyimidazolate) were synthesized under solvothermal reaction conditions. The materials were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, powder X-ray diffraction measurement (PXRD) and single-crystal X-ray diffraction. Compound 1 has hexacoordinate Cd II ions and forms a zigzag chain-like coordination polymer structure, whereas compound 2 exhibits a 2D square grid type structure. The thermal stability analysis reveals that 2 showed an exceptional thermal stability up to 360 °C. Also, 2 maintained its fully crystalline integrity in boiling water as confirmed by PXRD. The solid state luminescent property of 1 was not observed at room temperature. Compound 2 showed an independent high spin central Co II atom.

Description: The amino substituted bidentate chelating ligand 2-amino-5-(2-pyridyl)-1,3,4-thiadiazole (H 2 L ) was used to prepare 3:1-type coordination compounds of iron(II), cobalt(II) and nickel(II). In the iron(II) perchlorate complex [Fe II (H 2 L ) 3 ](ClO 4 ) 2 ·0.6MeOH·0.9H 2 O a 1:1 mixture of mer and fac isomers is present whereas [Fe II (H 2 L ) 3 ](BF 4 ) 2 ·MeOH·H 2 O, [Co II (H 2 L ) 3 ](ClO 4 ) 2 ·2H 2 O and [Ni II (H 2 L ) 3 ](ClO 4 ) 2 ·MeOH·H 2 O feature merely mer derivatives. Moessbauer spectroscopy and variable temperature magnetic measurements revealed the [Fe II (H 2 L ) 3 ] 2+ complex core to exist in the low-spin state, whereas the [Co II (H 2 L ) 3 ] 2+ complex core resides in its high-spin state, even at very low temperatures.