Retention of the Zn−Zn bond in [Ge9Zn−ZnGe9]6− and Formation of [(Ge9Zn)−(Ge9)−(ZnGe9)]8− and Polymeric [−(Ge9Zn)2−−]

Reactions of Zn^I₂L₂ (where L=[HC(PPh₂NPh)]⁻) with solutions of the Zintl phase K₄Ge₉ in liquid ammonia lead to retention of the Zn−Zn bond and formation of the anion [(η⁴‐Ge₉)Zn−Zn(η⁴‐Ge₉)]⁶⁻, representing the first complex with a Zn−Zn unit carrying two cluster entities. The trimeric anion [(η⁴‐Ge₉)Zn{μ₂(η¹:η¹Ge₉)}Zn(η⁴‐Ge₉)]⁸⁻ forms as a side product, indicating that oxidation reactions also take place. The reaction of Zn₂Cp*₂ (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) with K₄Ge₉ in ethylenediamine yielded the linear polymeric unit {[Zn[μ₂(η⁴:η¹Ge₉)]}²⁻ with the first head‐to‐tail arrangement of ten‐atom closo ‐clusters. All anions were obtained and structurally characterized as [A (2.2.2‐crypt)]⁺ salts (A =K, Rb). Copious computational analyses at a DFT‐PBE0/def2‐TZVPP/PCM level of theory confirm the experimental structures and support the stability of the two hypothetical ten vertex cluster fragments closo ‐[Ge₉Zn]²⁻ and (paramagnetic) [Ge₉Zn]³⁻.     

Darstellung und Charakterisierung von Thiocyanatderivaten der Hydroboratanionen B10H102− und B12H122−

Preparation and Characterization of Thiocyanate Derivatives of the Hydroborate Anions B₁₀H₁₀^2? and B₁₂H₁₂^2? The reaction of B₁₀H₁₀^2? or B₁₂H₁₂^2? with (SCN)₂ in dichloromethane yields mixtures of thiocyanatohydroborates from which the pure isomers 1-and 2-(SCN)B₁₀H₉^2?, 1, 10-(SCN)₂B₁₀H₈^2?, and 1-(SCN)B₁₂H₁₁^2? are isolated by ion exchange chromatography on diethylaminoethyl cellulose. The structures are determined by ¹¹B and ¹¹B{¹H}NMR spectroscopy. There are characteristic chemical shifts due to apical and equatorial substituents, respectively. In B₁₀H₁₀^2? the substitution at apical positions is prefered. The IR and Raman spectra are similar to those of isosteric halogeno derivatives in the region of ν(BH) and of the borate cages. Because of the high frequencies of ν(CN): 2120–2140 cm^?1 S coordination of SCN^? is supposed.     

Pr10[Si10−xAlxO9+xN17−x]Cl with x ≈ 1 – an Oxonitridoaluminosilicate Chloride

The oxonitridoaluminosilicate chloride Pr₁₀[Si_10?xAl_xO_9+xN_17?x]Cl was obtained by the reaction of praseodymium metal, the respective chloride, AlN and Al(OH)₃ with “Si(NH)₂” in a radiofrequency furnace at temperatures around 1900 °C. The crystal structure was determined by single‐crystal X‐ray diffraction (Pbam, no. 55, Z = 2,a = 10.5973(8) Å, b = 11.1687(6) Å, c = 11.6179(7) Å, R1 = 0.0337). The sialon crystallizes isotypically to the oxonitridosilicate halides Ce₁₀[Si₁₀O₉N₁₇]Br, Nd₁₀[Si₁₀O₉N₁₇]Br and Nd₁₀[Si₁₀O₉N₁₇]Cl, which represent a new layered structure type. The structure refinement was performed utilizing an O/N‐distribution model according to Paulings rules, i.e. nitrogen was positioned on all bridging sites and mixed O/Noccupation was assumed on the terminal sites resulting in charge neutrality of the compounds. The Si and Al atoms were refined equally distributed on their three crystallographic sites, due to their poor distinguishability by X‐ray analysis. The tetrahedra layers of the structure consist of condensed [(Si,Al)N₂(O,N)₂] and [(Si,Al)N₃(O,N)] tetrahedra of Q² and Q³ type. The chemical composition of the compound was derived from electron probe micro analyses (EPMA).     

Asymmetric Total Synthesis of (−)‐Cladospolide B

An enantioselective total synthesis of (?)‐cladospolide B was described. The key steps in this synthesis include(a) a Sharpless asymmetric dihydroxylation to elaborate syn diol at C‐4 and C‐5 positions; (b) a Mitsunobu esterification to reverse the configuration at C‐11 from (S) to (R); and (c) a ring‐closing metathesis to access the 12‐membered macrocyclic ring.     

Short communication: Thermal stability of the diazohydroborate [1‐N2B10H9]−: degradation to [B20H18]2− anion

The thermal stability of the monodiazohydroborate NMe₄[1‐N₂B₁₀H₉] was studied by thermogravimetric analysis. Under two different atmospheres (air and argon), the thermal decomposition starts at a temperature between 140 and 160 °C. The decomposition residue obtained was separated on a silica gel column. ¹¹B NMR, IR and electrospray mass spectroscopy analyses of the different fractions separated showed that the above decomposition produces (NMe₄)₂[B₂₀H₁₈] as major product (90%), along with smaller amounts of residual NMe₄[1‐N₂B₁₀H₉] (5%), (NMe₄)₂[B₁₂H₁₂] and boric acid. Copyright © 2003 John Wiley & Sons, Ltd.     

Packing considerations of 10‐oxa‐9‐boraphenanthrene derivatives

The crystal structures of three products of the reaction of 2‐phenylphenol and BCl₃ have been determined. The structures show intriguing packing patterns and an interesting case of pseudosymmetry. In addition, one of the two polymorphs has a primitive monoclinic crystal system, but it is twinned and emulates an orthorhombic C‐centred structure. Tris(biphenyl‐2‐yl) borate, C₃₆H₂₇BO₃, ( III ), crystallizes with only one molecule in the asymmetric unit. The dihedral angles between the planes of the aromatic rings in the biphenyl moieties are 50.47 (13), 44.95 (13) and 42.60 (13)°. The boron centre is in a trigonal planar coordination with two of the biphenyl residues on one side of the BO₃ plane and the remaining biphenyl residue on the other side. One polymorph of 10‐oxa‐9‐boraphenanthren‐9‐ol, C₁₂H₉BO₂, ( V a ), crystallizes with two almost identical molecules (r.m.s. deviation of all non‐H atoms = 0.039 Å) in the asymmetric unit. All non‐H atoms lie in a common plane (r.m.s. deviation = 0.015 Å for both molecules in the asymmetric unit). The two molecules in the asymmetric unit are connected into dimers via O—H...O hydrogen bonds. A second polymorph of 10‐oxa‐9‐boraphenanthren‐9‐ol, ( V b ), crystallizes as a pseudo‐merohedral twin with two almost identical molecules (r.m.s. deviation of all non‐H atoms = 0.035 Å) in the asymmetric unit. All non‐H atoms lie in a common plane (r.m.s. deviation = 0.012 Å for molecule 1 and 0.014 Å for molecule A). Each of the two molecules in the asymmetric unit is connected into a centrosymmetric dimer via O—H...O hydrogen bonds. The main difference between the two polymorphic structures is that in ( V a ) the two molecules in the asymmetric unit are hydrogen bonded to each other, whereas in ( V b ), each molecule in the asymmetric unit forms a hydrogen‐bonded dimer with its centrosymmetric equivalent. 9‐[(Biphenyl‐2‐yl)oxy]‐10‐oxa‐9‐boraphenanthrene, C₂₄H₁₇BO₂, ( VI ), crystallizes with four molecules in the asymmetric unit. The main differences between them are the dihedral angles between the ring planes. Apart from the biphenyl moiety, all non‐H atoms lie in a common plane (r.m.s. deviations = 0.026, 0.0231, 0.019 and 0.033 Å for molecules 1, A, B and C, respectively). This structure shows pseudosymmetry; molecules 1 and A, as well as molecules B and C, are related by a pseudo‐translation of about in the direction of the b axis. Molecules 1 and B, as well as molecules A and C, are related by a pseudo‐inversion centre at ,,. Neither between molecules 1 and C nor between molecules A and B can pseudosymmetry be found.     

Li47B3P14N42—A Lithium Nitridoborophosphate with [P3N9]12−, [P4N10]10−, and the Unprecedented [B3P3N13]15− Ion

Li₄₇B₃P₁₄N₄₂, the first lithium nitridoborophosphate, is synthesized by two different routes using a Li₃N flux enabling a complete structure determination by single‐crystal X‐ray diffraction data. Li₄₇B₃P₁₄N₄₂ comprises three different complex anions: a cyclic [P₃N₉]¹²⁻, an adamantane‐like [P₄N₁₀]¹⁰⁻, and the novel anion [P₃B₃N₁₃]¹⁵⁻. [P₃B₃N₁₃]¹⁵⁻ is the first species with condensed B/N and P/N substructures. Rietveld refinement, ⁶Li, ⁷Li, ¹¹B, and ³¹P solid‐state NMR spectroscopy, FTIR spectroscopy, EDX measurements, and elemental analyses correspond well with the structure model from single‐crystal XRD. To confirm the mobility of Li⁺ ions, their possible migration pathways were evaluated and the temperature‐dependent conductivity was determined by impedance spectroscopy. With the Li₃N flux route we gained access to a new class of lithium nitridoborophosphates, which could have a great potential for unprecedented anion topologies with interesting properties.     

Highly Diastereoselective Total Syntheses of (+)‐7‐Epigoniodiol, (−)‐8‐Epigoniodiol,and (+)‐9‐Deoxygoniopypyrone

An expedient concise total synthesis of (+)‐7‐epigoniodiol, (?)‐8‐epigoniodiol, and (+)‐9‐deoxygoniopypyrone is accomplished. The key transformations include a catalytic hydroxylation and base‐mediated N‐(acetyl)oxazolidinone addition reactions, which could set the consecutive OH motif that is either syn,syn or syn,anti with high diastereoselectivity. Moreover, this approach envisioned to facilitate the synthesis of other representatives of the family with structural and stereochemical variation.     

Enantioselective Total Syntheses of (−)‐Rhazinilam, (−)‐Leucomidine B,and (+)‐Leuconodine F

A divergent total synthesis of three structurally distinct natural products from imine 9 was accomplished through an approach featuring: 1) a Pd‐catalyzed decarboxylative cross‐coupling, and 2) heteroannulation of 9 with bromoacetaldehyde and oxalyl chloride to give tetrahydroindolizine 6 and dioxopyrrole 7 , respectively. The former was converted into (−)‐rhazinilam, while the latter was converted into (−)‐leucomidine B and (+)‐leuconodine F. A substrate‐directed highly diastereoselective reduction of a sterically unbiased double bond by using a homogeneous palladium catalyst was developed. A self‐induced diastereomeric anisochronism (SIDA) phenomenon was observed for leucomidine B.     

The formation of [C9H10]+˙ ions by loss of a molecule of water from molecular ions of 3-phenylpropanol with lifetimes of 10−11 to 10−5 s

Field ionization kinetic experiments in conjunction with deuterium labelling have been shown that the molecular ions of 3-phenylpropanol with lifetimes as short as 10^?11s lose a molecule of water via a specific 1,3 elimination. At times > 10^?11s two distinct hydrogen interchange processes in the molecular ions appear to complete with this reaction. One of the intechange processes involves the benzylic and hydroxylic hydrogen atoms and starts to complete with the elimination of water at shorter molecular ion lifetimes than the other interchange process in which the ortho hydrogen atoms also participate. Decomposing [C₉H₁₀]^+˙ ions generated by elimination of water from the molecular ions of 3-phenylpropanol or by direct ionization of various isomeric C₉H₁₀ compounds could not be distinguished adequately, illustrating isomerization either to a common ion structure or to a set of ions with rapidly interconverting structures. A consideration of the energetics of the elimination of water from 3-phenylpropanol suggests that at threshold energies 1-phenylpropene or indane type structures can be formed. Arguments for the latter have been obtained from the observation that a labile fluorine atom is present in the [M – H₂O]^+˙ ions generated from 3-pentafluoro-phenylpropanol.