Volume 68, Issue 1

By heating of FeCl 2 and MnCl 2 in the ionic liquid [BMIm][OTf] (BMIm: 1-butyl-3- methylimidazolium, OTf: trifluoromethanesulfonate), the compounds [BMIm][M(OTf) 3 ] (M: Fe +II , Mn +II ) have been obtained as colorless crystals. Similarly, [BMIm][Li(OTf) 2 ] was synthesized by heating of LiCl in [BMIm][OTf]. While the crystal quality of the [BMIm][M(OTf) 3 ] (M: Fe +II , Mn +II ) products thus obtained is low, mild oxidation of Fe(CO) 5 or Mn2(CO) 10 with GeI 4 applied as an alternative in the same ionic liquid allowed a slow growth of well-formed, needle-shaped crystals. According to X-ray structure analysis based on single crystals, [BMIm][M(OTf) 3 ] (M: Fe +II , Mn +II ) crystals are monoclinic, and [BMIm][Li(OTf) 2 ] crystals are triclinic. All compounds form infinite 1 ∞ [M(OTf) 3 ] (M=Fe, Mn) and 1 ∞ [Li(OTf) 2 ] chains. The compounds have further been characterized by FT-IR spectroscopy, energy-dispersive X-ray analysis (EDX), differential thermal analysis (DTA), thermogravimetry (TG), and magnetic measurements. Graphical Abstract [BMIm][Fe(OTf) 3 ], [BMIm][Mn(OTf) 3 ], [BMIm][Li(OTf) 2 ] – Three One-dimensional Infinite Coordination Polymers

The stannides RE 2 Ni 2 Sn (RE=Pr, Ho, Er, Tm) were synthesized by arc-melting of the elements and characterized by powder X-ray diffraction. Pr 2 Ni 2 Sn crystallizes with the orthorhombic W 2 B 2 Co-type structure, Immm, a=443.8(1), b=572.1(1), c=855.1(2) pm, wR2=0.0693, 293 F 2 values, 13 variables. A structural transition to the tetragonal Mo 2 B 2 Fe type occurs for the heavier rare earth elements. The structures of Ho 2 Ni 2 Sn (a=729.26(9), c=366.66(7) pm, wR2=0.0504, 250 F 2 values, 12 variables), Er 2 Ni 2 Sn (a=727.2(2), c=364.3(1) pm, wR2=0.0397, 262 F 2 values, 12 variables), and Tm 2 Ni 2 Sn (a=725.2(1), c=362.8(1) pm, wR2=0.0545, 258 F 2 values, 12 variables) were refined from single-crystal diffractometer data. The switch in structure type is driven by the size of the rare earth element. The [Ni 2 Sn] substructures are composed of Ni 2 Sn 2 squares and Ni 4 Sn 2 hexagons in Pr 2 Ni 2 Sn, and of Ni 3 Sn 2 pentagons in Er 2 Ni 2 Sn. The Ni 4 Sn 2 hexagons and Ni 3 Sn 2 pentagons exhibit Ni 2 pairs with Ni-Ni distances of 247 pm in Pr 2 Ni 2 Sn, and of 250 pm in Er 2 Ni 2 Sn. Graphical Abstract The Stannides RE 2 Ni 2 Sn (RE = Pr, Ho, Er, Tm) – Structural Transition from the W 2 B 2 Co to the Mo 2 B 2 Fe Type as a Function of the Rare Earth Size

The tin-rich stannides SrCo 2 Sn 8 and BaCo 2 Sn 8 were synthesized from the elements in sealed tantalum tubes. They crystallize with a new structure type, space group Cccm with a=1006.0(3), b=1514.4(6), c=1385.0(6) pm for SrCo 2 Sn 8 and a=1032.8(2), b=1516.8(3), c=1405.1(3) pm for BaCo 2 Sn 8 . The structure of the barium compound was refined on the basis of single-crystal Xray diffractometer data: wR2=0.0450, 1715 F 2 values, 57 variables. The cobalt atoms have seven nearest tin neighbors with Co-Sn distances ranging from 257 to 273 pm. These CoSn 7 units are condensed via common rectangular faces to [Co2Sn10] double units which build up a covalently bonded three-dimensional network through Sn-Co-Sn bridges. Larger voids left by this network are filled by the barium and the Sn 2 atoms. The latter have distorted octahedral tin coordination with Sn2- Sn distances of 311 - 315 pm. The barium atoms have 13 nearest tin neighbors (352 - 399 pm Ba-Sn). Temperature-dependent magnetic susceptibility data of BaCo 2 Sn 8 show Pauli paramagnetism. Graphical Abstract SrCo 2 Sn 8 and BaCo 2 Sn 8 : Tin-rich Stannides with Distorted SnSn 6 Octahedra within Three-dimensional [Co 2 Sn 8 ] Networks

The gallium-rich ternary intermetallic compound YTi 2 Ga 4 is isotypic with YbMo 2 Al 4 , I4/mmm, Z =2. Yttrium is located in a large cage built up by 12 gallium atoms. Chains of condensed Y@Ga 12 polyhedra and linear titanium chains build up a tetragonal rod packing. The gallium atoms are bonded within Ga4 squares (265 pm Ga-Ga) which are condensed via longer Ga-Ga bonds (292 pm) to a three-dimensional gallium substructure with formally four-connected gallium, in agreement with a Bader charge partitioning scheme [YTi 2 ] 4+ [Ga 4 ] 4- . These features are addressed with electronic structure and chemical bonding considerations. The metallic behavior of YTi 2 Ga 4 is found to be of the itinerant electron type within the valence band and Ti d-like states at E F . Ga-Ga and Ti-Ga bonding characteristics provide mechanical properties derived from the full set of elastic constants leading to a brittle material. Graphical Abstract Electronic Structure and Bonding in YTi2Ga4 – A Gallide with Linear Titanium Chains and Four-bonded Gallium Atoms

The new rare earth fluoride borates RE 5 (BO 3 ) 2 F 9 ( RE =Ho, Dy) were synthesized under high-pressure/high-temperature conditions of 1:5 GPa, 1250°C for Dy 5 (BO 3 ) 2 F 9 and 2:5 GPa, 1200°C for Ho 5 (BO 3 ) 2 F 9 in a Walker-type multianvil apparatus from the corresponding rare earth oxides, rare earth fluorides, and boron oxide. The single-crystal structure determinations have revealed that both compounds are isotypic to the known rare earth fluoride borates RE 5 (BO 3 ) 2 F 9 ( RE =Er, Tm, Yb). The new fluoride borates crystallize monoclinically in the space group C 2/ c ( Z =4) with the lattice parameters a =2046.7(4), b =615.9(2), c =829:6(2) pm, β =100.1(1)° for Dy 5 (BO 3 ) 2 F 9 and a =2039.5(4), b =612.7(2), c =827:1(2) pm, β =100.2(1)° for Ho 5 (BO 3 ) 2 F 9 . Three crystallographically different nine-fold coordinated rare earth cations can be identified in the crystal structure. All boron atoms build up isolated trigonal-planar [BO 3 ] 3– groups. In addition to the Raman and IR spectroscopic investigations, DFT-calculations were performed to support the assignment of the vibrational bands. Graphical Abstract High-pressure Syntheses and Characterization of the Rare Earth Borates RE5(BO 3 ) 2 F 9 (RE=Dy, Ho)

Colorless, transparent single crystals of CaBa 8 [CN 2 ] 6 O 2 (N 0.5 H 0.5 ) (R3̄ (no. 148), a = 996.94(4) and c = 1803.18(8) pm, Z = 3) were obtained by the reaction of Ca 3 N 2 , Ba 2 N and NaHCN 2 (of which one of the latter two most likely was contaminated with some oxygen impurity) in arcwelded Nb ampoules at 1200 K. The title compound consists of distorted (H/N)Ba 6 octahedra which share two of their opposite faces with OBa 4 tetrahedra interconnected by [N=C=N] 2- units of Ca(N=C=N) 6 octahedra with C=N bond lengths of 121.9(6) and 124.3(6) pm and with a bond angle deviating from linearity with (N-C-N) = 175:9(5)°. A Raman spectrum obtained from the crystal used for the structure determination indicates the presence of the [N=C=N] 2- unit. Graphical Abstract Synthesis, Raman Spectrum and Single-Crystal Structure of CaBa 8 [CN 2 ] 6 O 2 (N 0.5 H 0.5 )

For equiatomic MgNi which can be hydrogenated up to the composition MgNiH 1.6 at an absorption/ desorption temperature of 200 °C, the effects of hydrogen absorption are approached with the model structures MgNiH, MgNiH 2 and MgNiH 3 . From full geometry optimization and calculated cohesive energies obtained within DFT, the MgNiH 2 composition close to the experimental limit is identified as most stable. Charge density analysis shows an increasingly covalent character of hydrogen: MgNiH (H -0.67 ) → MgNiH 2 (H -0.63 ) ! MgNiH 3 (H -0.55 ). While Mg-Ni bonding prevails in MgNi and hydrogenated model phases, extra itinerant low-energy Ni states appear when hydrogen is introduced signaling Ni-H bonding which prevails over Mg-H as evidenced from total energy calculations and chemical bonding analyses. Graphical Abstract Hydrogen Insertion Effects on the Electronic Structure of Equiatomic MgNi Traced by ab initio Calculations

Nanoparticles of zirconium(IV) oxide catalyze the three-component coupling of aromatic aldehydes, b-diketones and urea to afford the correspo nding 3,4-dihydropyrimidinones (Biginelli compounds) in moderate to good yields under mild conditions. Graphical Abstract Study of the Synthesis of Some Biginelli-type Products Catalyzed by Nano-ZrO 2

A series of stable acyclic aminals derived from L-(+)-aspartic acid were synthesized in excellent yields (up to 96%) and characterized by spectroscopic methods. They were applied as enantioselective catalysts in Henry reactions of nitromethane with various aldehydes in the presence of Cu(II) ions, affording the corresponding adducts in high yields (up to 90%) and enantioselectivities (up to 92% ee). Graphical Abstract Synthesis of Stable Acyclic Aminals Derived from L-(+)-Aspartic Acid and Their Application in Asymmetric Henry Reactions

The vicinity of a hydrogen bond donor (O-H) and a hydrogen bond acceptor (C=O or C=N- R) in salicylaldehydes and ortho-Schiff bases results in significant structural variations compared to the monosubstituted derivatives that are reflected in the electronic structure and thus in the spectroscopic properties. This interplay between intramolecular hydrogen bonding and multicenter p- electron delocalization is the origin of the concept of resonance-assisted hydrogen bonding (RAHB). Herein, the complexity is extended from one hydrogen bond donor-acceptor pair in salicylaldehyde and ortho-Schiff bases to three hydrogen bond donor-acceptor pairs in 2,4,6-tricarbonyl- and 2,4,6- triimine-substituted phloroglucinols (1,3,5-trihydroxybenzene), respectively. To evaluate the changes in the molecular and electronic structures, we have performed a comprehensive computational, spectroscopic, and structural study starting from monosubstituted benzene derivatives as references over ortho-disubstituted derivates to the sixfold-substituted derivatives. Whereas in salicylaldehydes, ortho- Schiff bases, and 2,4,6-tricarbonyl-phloroglucinols the phenolic O-protonated tautomers represent the energy minima, the N-protonated tautomers represent the energy minima in 2,4,6-triiminephloroglucinols. The analysis provides a keto-enamine resonance structure with six exocyclic double bonds to be dominant for these species reminiscent of [6]radialenes, which were termed heteroradialenes. These heteroradialenes are non-aromatic alicycles. However, the predominance of this resonance structure does not represent a sudden change going from the 2,4,6-tricarbonyl- to the 2,4,6-triimine-phloroglucinols, but a gradual increase of analogous resonance structure contributions is observed even in salicylaldehyde and ortho-Schiff bases demonstrating some hetero-orthoquinodimethane character. These changes are, besides in the molecular structures, well reflected in the IR spectra, which can therefore be used as a simple tool to probe the electronic structures in these systems. Interruption of the delocalized p system supporting the intramolecular hydrogen bond, i. e. going from 2,4,6-triimine- to 2,4,6-triamine-substituted phloroglucinols, reestablishes an O-protonated aromatic phloroglucinol system. Graphical Abstract Electronic and Molecular Structures of Heteroradialenes: A Combined Synthetic, Computational, Spectroscopic, and Structural Study Identifying IR Spectroscopy as a Simple but Powerful Experimental Probe

The formation and the structure of [(CO) 4 Mo(Et 4 Sb 2 )] 2 (1) and of a complex with distibane and distibane oxide ligands (2) are reported. Graphical Abstract Formation and Structure of [(CO) 4 Mo(Et 4 Sb 2 )] 2

In an attempt to prepare the tris(selenoureato)gallium(III) complex [Ga(4-O 2 NC 6 H 4 C(O)NC(Se)NEt 2 ) 3 ] from the reaction of the nitro-substituted acylselenourea 4-O 2 NC 6 H 4 C(O)NHC(Se)NEt 2 with [Ga(NO 3 ) 3 ] in EtOH we obtained a crystalline compound from a CH 2 Cl 2 solution which was identified as the bis(selenoureato)gallium(III)chlorido complex [GaCl(4- O 2 NC 6 H 4 C(O)NC(Se)NEt 2 ) 2 ] by single-crystal X-ray diffraction. This compound is a rare example of a metal complex containing chelating selenoureato ligands in a trans arrangement. Graphical Abstract Synthesis and Structural Characterization of a Gallium(III) Bis(selenoureato) Complex

Ca 2 Pd 2 Cd was synthesized by high-frequency melting of the elements in a sealed niobium ampoule. Its structure was refined from single-crystal X-ray diffractometer data: W 2 B 2 Co type, Immm, a=444.58(6), b=590.25(6), c=863.07(10) pm, wR2=0.0252, 305 structure factors, 13 variables. The palladium and cadmium atoms build up twodimensional [Pd 2 Cd] networks which consist of Pd 4 Cd 2 hexagons and Pd 2 Cd 2 rectangles with 272.7 pm Pd-Pd and 273.2 pm Pd-Cd. The calcium atoms are coordinated by one Pd 4 Cd 2 and one Pd 2 Cd 2 unit. The structure of Ca 2 Pd 2 Cd is compared to that of Ce 2 Pd 2 Cd with its tetragonal Mo 2 B 2 Fe type. Graphical Abstract Ca 2 Pd 2 Cd with W 2 B 2 Co-type Structure

threo-4-Diazo-1,2-diphenyl-3-oxo-butyl acetate (15) could be prepared via the classical route 6→8→10→12→13→15. However, its alkaline hydrolysis to the bifunctional hydroxy compound 17 led to a spontaneous dehydration to the diazoketone (E)-18 and to a fragmentation to acetic acid, benzaldehyde (8) and diazoketone 19. Graphical Abstract Formation and Fragmentation of 4-Diazo-1,2-diphenyl-3-oxo-butyl Acetate