Reactions of Nitro and Halonitro Derivatives of Aluminum(III) and Copper(II) Phthalocyanines with Concentrated Sulfuric Acid

Transformations of the complexes CuPc(4-NO₂)₄, CuPc(4-Br)₄(5-NO₂)₄, (OH)AlRs(4-NO₂)₄, and (OH)AlPc(4-Cl)₄(5-NO₂)₄ in concentrated sulfuric acid were studied by spectrophotometry. One protonated form of CuPc(4-Br)₄(5-NO₂)₄ and (OH)AlPc(4-NO₂)₄ and two protonated forms of CuPc(4-NO₂)₄ and (OH)AlPc(4-Cl)₄(5-NO₂)₄ were detected experimentally and also by ZINDO1 calculations. Step protonation constants of CuPc(4-NO₂)₄ and (OH)AlPc(4-Cl)₄(5-NO₂)₄ were determined by quantum-chemical calculations and acid-base titration; these complexes can be regarded as weak bases with respect to H₂SO₄. The kinetics of dissociation of the complexes at the MÄN bonds were studied. The rate of dissociation of the Cu(II) complexes and (OH)AlPc(4-NO₂)₄ is proportional to [MPc(R) _n ] and [H₃O⁺]². The rate of dissociation of (OH)AlPc(4-Cl)₄(5-NO₂)₄ showed a weak extremal dependence on the composition of the medium, which was explained by change of its structure in 17.0 M H₂SO₄. The electronic effect of substituents on the reaction center was considered with account taken of a complex mechanism of activation and fine details of the molecular structure of macrocyclic complexes.     

Darstellung und Eigenschaften von Kupfer(II)-Hypophosphit

Thermal Behaviour of the Mixtures Na₂S? P₄S₁₀ and Na₄Ge₄S₁₀? P₄S₁₀ of the System Na₂S? GeS₂? P₄S₁₀ The mixtures of Na₂S? P₄S₁₀ and Na₄Ge₄S₁₀? P₄S₁₀ were investigated by DTA and DSC. In the system Na₂S? P₄S₁₀ the congruently melting compounds Na₃PS₄ and (NaPS₃)_x and the peritectic phase Na₄P₂S₇ were found. The IR-spectra are given. Glassy, anhydrous and hydrated Na₄Ge₄S_l0 were prepared and thermochemically characterized. The section Na₄Ge₄S₁₀? P₄S₁₀ is not quasibinary, the mixed cage-anion Ge_4?xP_xS₁₀^(4?x)? thus cannot be prepared by heating and annealing mixtures of Na₄Ge₄S₁₀ and P₄S₁₀.     

A gas electron diffraction study of the molecular structures of methyl allenyl sulphide and methyl vinyl sulphide and their relation to other organic s

The vibrational and electronic spectra as well as the magnetic properties of the ion [Co(NH₃)₄]²⁺are given and discussed. [Co(NH₃)₄](ReO₄)₂ crystallizes cubically and is isostructural with the compounds [Zn(NH₃)₄](ReO₄)₂, [Zn(NH₃)₄](MnO₄)₂, [Cd(NH₃)₄](ReO₄)₂, [Cd(NH₃)₄](MnO₄)₂, [Zn(NH₃)₄]- (OsO₃N)₂ and [Cd(NH₃)₄](OsO₃N)₂.     

Thermal decomposition of some ruthenium carbonyl hydrides

The thermal stability of α-H₄Ru₄(CO)₁₂, H₄Ru₄(CO)₁₀P₂, H₄Ru₄(CO)₉P₃, H₄Ru₄(CO)₈P₄ (where P=triphenylphosphine) has been investigated by differential scanning calorimetry and by thermogravimetric analysis under argon dynamic atmosphere.The TG curves of the triphenylphosphine substituted derivatives of α-H₄Ru₄(CO)₁₂ suggest the release of the carbonyl and of the phenyl groups through a not well-defined pattern and overlapping decomposition reactions up to the retention of phosphorus in the residue, while α-H₄Ru₄(CO)₁₂ decomposes to metallic ruthenium. The decomposition heat of α-H₄Ru₄(CO)₁₂ and the isomerization heat of H₄Ru₄(CO)₈P₄ have been evaluated.     

Tetrapnictidotitanate(IV) M4TiX4 (M = Sr,Ba; X = P,As), hierarchische Derivate der KGe-Struktur K4□Ge4

Tetrapnictidotitanates(IV) M₄TiX₄ (M = Sr, Ba; X = P, As), hierarchical Derivatives of the KGe Structure K₄□Ge₄ The four new tetrapnictidotitanates(IV) Sr₄TiP₄, Sr₄TiAs₄, Ba₄TiP₄ and Ba₄TiAs₄ are synthesized from the binary pnictides MX (M = Sr, Ba and X = P, As) and elementary titanium in tantalum ampoules. The compounds are isotypic and isoelectronic with Ba₄SiAs₄ (space group P4 3n (no. 218); cP72; Z = 8; Sr₄TiP₄: a = 1259.0(1) pm; Sr₄TiAs₄: a = 1288.3(4) pm; Ba₄TiP₄: a = 1316.6(2) pm; Ba₄TiAs₄: a = 1346.9(2) pm). The transition metal compounds form cubic, metallic reflecting crystals (Sr₄TiP₄ (green); Sr₄TiAs₄ (silver coloured); Ba₄TiP₄ (silver coloured); Ba₄TiAs₄ (violet). They are semiconducting and very sensitive against air and moisture. The structure is a hierarchical derivative of Cr₃Si (A15) and KGe type: Cr₆Si₂ ? (□Ge₄K₄)₆(□Ge₄K₄)₂ ? (TiX₄M₄)₆(TiX₄M₄)₂, where Ti occupies the positions of the Cr₃Si structure, and the alkaline-earth metal and pnicogen atoms occupy the positions of the KGe structure. Therefore, Ti is surrounded by four X and four more distant M atoms forming a heterocubane. The mean bond lengths are: d (Ti? P) = 238.0(5) pm; 307 ? d(Sr? P) ? 333 pm; d (Ti? As) = 245.9(4); 313 ? d(Sr? As) ? 341 pm; d (Ti? P) = 240.5(5); 324 ? d(Ba? P) ? 348 pm; d (Ti? As) = 248.3(3) pm; 331 ? d(Ba? As) ? 355 pm.     

Oxo-fluoro-aluminates and -gallates

The preparations of (NH₄)₂HAl₂OF₇, (NH₄)H₂AlOF₄, (NH₄)₂HGa₂OF_7^·3.5H₂O and (NH₄)₂HGaOF₄ are described. IR spectra suggest the presence of MOMO chains in these compounds. On isothermal heating at 180°C (NH₄)H₂AlOF₄ decomposes to give (NH₄)HAlOF₃, and at 150°C (NH₄)₂HGaOF₄ yields (NH₄)H₂GaOF₄. At 18°C (NH₄)₂HGa₂OF_7^·3.5H₂O yields the anhydrous compound.     

Syntheses and Structures of S4N4(OCH3)2 and CH3OS4N4(O)Cl

The reaction of S₄N₄Cl₂ with CH₃OH gives S₄N₄(OCH₃)₂, a simple dimethoxoderivative of S₄N₄. Its overall geometry is analogous to other compounds of the S₄N₄X₂ type. The chlorination of S₄N₄(OCH₃)₂ leads to the oxidation of one sulfur atom to S^VI and CH₃OS₄N₄(O)Cl is formed. The compounds were characterized by ir spectroscopy and their crystal structures were determined from single crystal diffraction data collected at ?153°C. The presence of S^VI in the molecule of CH₃OS₄N₄(O)Cl is manifested by a marked shortening of the bonds formed by this atom as compared with S₄N₄Cl₂ and S₄N₄(OCH₃)₂.     

Synthese und Röntgenstrukturanalyse von S4N4-Derivaten mit drei- und vierfach koordinierten Schwefelatomen

CF₃SO₂N?SCl₂ reagiert mit (CH₃)₂S[NSi(CH₃)₃]₂, (C₄H₈)S[NSi(CH₃)₃]₂ oder (C₅H₁₀)S[NSi(CH₃)₃]₂ unter Trimethylchlorsilanabspaltung zu den achtgliedrigen S₄N₄-Derivaten S₄N₄(NSO₂CF₃)₂(CH₃)₄ 3 , S₄N₄(NSO₂CF₃)₂(C₄H₈)₂ 4a und S₄N₄(NSO₂CF₃)₂(C₅H_{1 0})₂ 4b . In den achtgliedrigen SN-Ringen haben die Schwefelatome die Koordinationszahl 3 und 4. Die Röntgenstrukturanalyse von 4a ergab eine Sessel-Konformation. 4a kristallisiert orthorhombisch in der Raumgruppe Pna2₁ mit a = 17,641(4), b = 6,406(2), c = 19,130(4) Å, d_x = 1,815 g cm^?3 und Z = 4. Die mittleren S? N-Abstände betragen an den vierfach koordinierten Schwefelatomen 1,597 Å und an den Schwefelatomen mit der Koordinationszahl 3 1,650 Å. CF₃SO₂N? SCl₂ reagiert mit trimethylzinnhaltigen S? N-Verbindungen zum bekannten CF₃SO₂N[Sn(CH₃)₃]S(CH₃)NSO₂CF₃ und Dimethylzinndichlorid. Synthesis and X-Ray Structure Analysis of S₄N₄-Derivatives with Threefold and Fourfold Coordinated Sulfur Atoms CF₃SO₂N?SCl₂ reacts with (CH₃)₂S[NSi(CH₃)₃]₂, (C₄H₈)S[NSi(CH₃)₃]₂ or (C₅H₁₀S[NSi(CH₃)₂]₂ under elimination of (CH₃)₃SiCl to yield the eight-membered S₄N₄ derivatives S₄N₄?NSO₂CF₃)₂(CH₃)₄, 3 , S₄N₄(NSO₂CF₃)₂(C₄H₈)₂ 4a und S₄N₄(NSO₂CF₃)₂(C₅H_{1 0})₂ 4b . In the eight-membered SN-rings the sulfur atoms have the coordination number 3 and 4. The X-ray structure analysis of 4a revealed a chair conformation. 4a crystallizes in the orthorhombic space group Pna2₁ with a = 17.641(4), b = 6.406(2), c = 19.130(4) Å, d_x = 1.815 g cm^?3, and Z = 4. The average S? N distance was found to be 1.597 Å at fourfold coordinated sulfur atoms and 1.650 Å at sulfur with coordination number 3. CF₃SO₂N=SCl₂ reacts with trimethyl tin-containing S? N compounds to the known CF₃SO₂N[Sn(CH₃)₃]S(CH₃)NSO₂CF₃ and dimethyl tin dichloride.     

Schwingungsspektren von β-P4S5 und P4S7

Vibrational Spectra of β-P₄S₅ and P₄S₇ The vibrational spectra of the solid and liquid cage compounds β-P₄S₅ and P₄S₇ have been recorded. The assignments of the frequencies are proposed mainly based on polarization data. β-P₄S₅ decomposes during melting into P₄S₃ α-P₄S₇ and β-P₄S₆. Molten α-P₄S₇ dissociates to some extent into β-P₄S₆ and sulphur. An association of β-P₄S₆ with α-P₄S₇ is discussed for the molten state. All reactions in molten P₄S₇ are reversible.     

Comparison of the crystal structures of sodium orthosilicate,Na4SiO4, and sodium orthogermanate,Na4GeO4

The crystal structures of Na₄SiO₄ and Na₄GeO₄ are isotypic, despite a difference in coordination numbers: in Na₄SiO₄ only one of the four symmetrically independent sodium atoms is four coordinated, in Na₄GeO₄ two of them are.

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Vergleich der Kristallstrukturen von Natriumorthosilikat, Na₄SiO₄, und Natriumorthogermanat, Na₄GeO₄ (Kurze Mitteilung)

Zusammenfassung Die Kristallstrukturen von Na₄SiO₄ und Na₄GeO₄ sind isotyp, trotz eines Unterschiedes in den Koordinationszahlen: im Na₄SiO₄ ist nur eines der symmetrisch unabhängigen Natriumatome vierfach koordiniert, während es im Na₄GeO₄ derer zwei sind.

     

Synthesis and Structures of Silver(I) Complexes of 4-Amino-3,5-dipropyl-4H-1,2,4-triazole and 4-Amino-3,5-dibutyl-4H-1,2,4-triazole: A Possible Mechanism of Formation of Ag4tz6 Cluster

Five silver(I) complex of 4-amino-3,5-dipropyl-4H-1,2,4-triazole (4-NH₂-3,5-Pr₂tz) or 4-amino-3,5-dibutyl-4H-1,2,4-triazole (4-NH₂-3,5-Bu₂tz), namely [Ag₂(4-NH₂-3,5-Bu₂tz)₂(NO₃)₂] (1), [Ag₄(4-NH₂-3,5-Pr₂tz)₆(NO₃)₂](NO₃)₂ (2), [Ag₄(4-NH₂-3,5-Pr₂tz)₆](ClO₄)₄ (3), [Ag₄(4-NH₂-3,5-Pr₂tz)₆](CF₃SO₃)₄ (4) and [Ag₄(4-NH₂-3,5-Bu₂tz)₆](BF₄)₄ (5), have been prepared and structurally characterized by X-ray single crystal diffractions. Based on the structural data, a possible mechanism for the formation of Ag₄tz₆ cluster has been proposed, involving the formation of a dimer of dimer—(Ag₂tz₂)₂, followed by the replacement of counterions by two additional triazoles.     

Synthesis and crystal structure of the double cluster [Cp3Fe4(CO)4(C5H4)]2(p-C6H4)

[Cp₄Fe₄(CO)₄] (1) reacts with p-BrC₆H₄Li and MeOH in sequence to afford the functionalized cluster [Cp₃Fe₄(CO)₄(C₅H₄-p-C₆H₄Br)] (2), while the reaction of 2 with n-BuLi and MeOH produces [Cp₂Fe₄(CO)₄(C₅H₄Bu)(C₅H₄-p-C₆H₄Br)] (3). The double cluster [Cp₃Fe₄(CO)₄(C₅H₄)]₂(p-C₆H₄) (4) has been prepared by treatment of [Cp₄Fe₄(CO)₄] with p-C₆H₄Li₂ and MeOH in sequence. The electrochemistry of 2 and 4, as well as the crystal structure of 4 have been investigated.     

Metal‐Borohydride‐Modified Zr(BH4)4⋅8 NH3: Low‐Temperature Dehydrogenation Yielding Highly Pure Hydrogen

Due to its high hydrogen density (14.8 wt %) and low dehydrogenation peak temperature (130 °C), Zr(BH₄)₄ ? 8 NH₃ is considered to be one of the most promising hydrogen‐storage materials. To further decrease its dehydrogenation temperature and suppress its ammonia release, a strategy of introducing LiBH₄ and Mg(BH₄)₂ was applied to this system. Zr(BH₄)₄ ? 8 NH₃–4 LiBH₄ and Zr(BH₄)₄ ? 8 NH₃–2 Mg(BH₄)₂ composites showed main dehydrogenation peaks centered at 81 and 106 °C as well as high hydrogen purities of 99.3 and 99.8 mol % H₂, respectively. Isothermal measurements showed that 6.6 wt % (within 60 min) and 5.5 wt % (within 360 min) of hydrogen were released at 100 °C from Zr(BH₄)₄ ? 8 NH₃–4 LiBH₄ and Zr(BH₄)₄ ? 8 NH₃–2 Mg(BH₄)₂, respectively. The lower dehydrogenation temperatures and improved hydrogen purities could be attributed to the formation of the diammoniate of diborane for Zr(BH₄)₄ ? 8 NH₃–4 LiBH₄, and the partial transfer of NH₃ groups from Zr(BH₄)₄ ? 8 NH₃ to Mg(BH₄)₂ for Zr(BH₄)₄ ? 8 NH₃–2 Mg(BH₄)₂, which result in balanced numbers of BH₄ and NH₃ groups and a more active H^δ+ ??? ^?δH interaction. These advanced dehydrogenation properties make these two composites promising candidates as hydrogen‐storage materials.     

Neue phosphidoverbrückte Mehrkernkomplexe des Ag und Zn. Die Kristallstrukturen von [Ag3(PPh2)3(PnBu2tBu)3], [Ag4(PPh2)4(PR3)4] (PR3 = PMenPr2, PnPr3), [Ag4(PPh2)4(PEt3)4]n, [Zn4(PPh2)4Cl4(PRR2)2] (PRR′2 = PMenPr2, PnBu3, PEt2Ph), [Zn4(PhPSiMe3)4Cl4(C4H8O)2] und [Zn4(PtBu2)4Cl4]

New Phosphido-bridged Multinuclear Complexes of Ag and Zn. The Crystal Structures of [Ag₃(PPh₂)₃(PⁿBu₂^tBu)₃], [Ag₄(PPh₂)₄(PR₃)₄] (PR₃ = PMeⁿPr₂, PⁿPr₃), [Ag₄(PPh₂)₄(PEt₃)₄]_n, [Zn₄(PPh₂)₄Cl₄(PRR′₂)₂] (PRR′₂ = PMeⁿPr₂, PⁿBu₃, PEt₂Ph), [Zn₄(PhPSiMe₃)₄Cl₄(C₄H₈O)₂] and [Zn₄(P^tBu₂)₄Cl₄] AgCl reacts with Ph₂PSiMe₃ in the presence of tertiary Phosphines (PⁿBu₂^tBu, PMeⁿPr₂, PⁿPr₃ and PEt₃) to form the multinuclear complexes [Ag₃(PPh₂)₃(PⁿBu₂^tBu)₃] 1 , [Ag₄(PPh₂)₄(PR₃)₄] (PR₃ = PMeⁿPr₂ 2 , PⁿPr₃ 3 ) and [Ag₄(PPh₂)₄(PEt₃)₄]_n 4 . In analogy to that ZnCl₂ reacts with Ph₂PSiMe₃ and PRR′₂ to form the multinuclear complexes [Zn₄(PPh₂)₄Cl₄(PRR′₂)₂] (PRR′₂ = PMeⁿPr₂ 5 , PⁿBu₃ 6 , PEt₂Ph 7 ). Further it was possible to obtain the compounds [Zn₄(PhPSiMe₃)₄Cl₄(C₄H₈O)₂] 8 and [Zn₄(P^tBu₂)₄Cl₄] 9 by reaction of ZnCl₂ with PhP(SiMe₃)₂ and ^tBu₂PSiMe₃, respectively. The structures were characterized by X-ray single crystal structure analysis. Crystallographic data see “Inhaltsübersicht”.     

Syntheses and structures of silver(I) complexes of 4-amino-3,5-dimethyl-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole and 4-amino-3,5-diethyl-4<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazole: role of the substituents

Five silver(I) adducts of 4-amino-3,5-diethyl-4H-1,2,4-triazole (4-NH₂-3,5-Et₂-tz) or 4-amino-3,5-dimethyl-4H-1,2,4-triazole (4-NH₂-3,5-Me₂-tz), namely [Ag₄(4-NH₂-3,5-Et₂-tz)₆](ClO₄)₄ (1), [Ag(4-NH₂-3,5-Et₂-tz)₂] _n ·n(ClO₄) (2), [Ag₄(4-NH₂-3,5-Et₂-tz)₆](CF₃SO₃)₄ (3), [Ag₄(4-NH₂-3,5-Me₂-tz)₆](ClO₄)₄·4H₂O (4) and [Ag₄(4-NH₂-3,5-Me₂-tz)₆](CF₃SO₃)₄·2H₂O (5), have been prepared and structurally characterised by X-ray single crystal diffraction. Two types of Ag₄tz₆ cluster have been observed in the structures of compound 1, 3, 4 and 5, which is rationalised based on the minimisation of the steric repulsions between the substituents on the 3,5-positions of triazole ring. Compound 2 displays an infinite chain structure and may be an intermediate or a minor product in the preparation.     

Preparation and Reactivity of Mo(NCMe)(η2‐C2Ph2)2(η4‐C4Ph4)

Reaction of Mo(CO)(η²‐C₂Ph₂)₂(η⁴‐C₄Ph₄) and Me₃NO in acetonitrile solvent affords Mo(NCMe)(η²‐C₂Ph₂)₂(η⁴‐C₄Ph₄) 1 . Compound 1 reacts with trimethylphosphine to produce Mo(PMe₃)(η²‐C₂Ph₂)₂(η⁴‐C₄Ph₄) 2 , or reacts with diphenylacetylene to produce (η⁵‐C₅Ph₅)₂Mo 3 and Mo(η²‐O₂CPh)(η⁴‐C₄Ph₄H)(η⁴‐C₄Ph₄) 4 . The molecular structures of 1, 2 and 4 have been determined by an X‐ray diffraction study.     

Synthesen und Kristallstrukturen von [(t-Bu4Sb4)Fe(CO)4], [(t-Bu4Sb4)Mo(CO)5] und [(t-Bu3Sb4)Mo(η5-C5Me5)(CO)3]

Syntheses and Crystal Structures of [( t -Bu₄Sb₄)Fe(CO)₄], [( t -Bu₄Sb₄)Mo(CO)₅], and [( t -Bu₃Sb₄)Mo(η⁵-C₅Me₅)(CO)₃] t-Bu₄Sb₄ reacts with Fe₂(CO)₉ to form [(t-Bu₄Sb₄)Fe(CO)₄] ( 1 ). [(t-Bu₄Sb₄)Mo(CO)₅] ( 2 ) is formed from (thf)Mo(CO)₅ and t-Bu₄Sb₄. [(t-Bu₃Sb₄)Mo(η⁵-C₅Me₅)(CO)₃] ( 3 ) is a product of the reaction of t-Bu₄Sb₄ with [(η⁵-C₅Me₅)Mo(CO)₃]₂. The crystal structures of 1–3 are reported.     

Etude des Phases Na4XO4 (X = Sn,Pb) et de K4SnO4 par Spectrophotométrie d′Absorption Infrarouge et Diffusion Raman

Infrared and Raman Studies of the Na₄SnO₄, Na₄PbO₄, and K₄SnO₄ phases The vibrational spectra of the Na₄SnO₄, Na₄PbO₄, and K₄SnO₄ phases have been studied for the first time. They characterize isolated tetrahedral XO₄ groups. The assignments of the i.r. and Raman frequencies have been made by a factor group analysis. The force constants, calculated for K₄SnO₄ using the obtained spectroscopic data, show the covalent character of the Sn? O bond.     

Reaktionen von Oxiden der Elemente der V. Hauptgruppe mit Trithiazylchlorid Kristallstruktur von (S5N5)4[As8Cl28] · 2 S4N4

Reactions of Element Oxides of the Fifth Main Group with Trithiazyl Chloride. Crystal Structure of (S₅N₅)₄[As₈Cl₂₈] · 2 S₄N₄ Whereas P₄O₁₀ does not react with (NSCl)₃, the oxides As₂O₃, Sb₂O₃, and Bi₂O₃ react under formation of (S₅N₅)₄[As₈Cl₂₈] · 2 S₄N₄, S₅N₅[SbCl₆] and a mixture of S₄N₅[BiCl₄] and S₄N₄Cl[BiCl₄], respectively. The products were characterized by their IR spectra. The crystal structure of (S₅N₅)₄[As₈Cl₂₈] · 2 S₄N₄ was determined by means of X-ray diffraction (1168 independent observed reflexions, R = 0.059). Crystal data: tetragonal, space group P4 2₁c, Z = 2, a = 1596.6, c = 1520.1 pm. The compound consists of planar S₅N₅^⊕ cations, octameric anions [As₈Cl₂₈]^4? and S₄N₄ molecules. The S₅N₅^⊕ ions and the S₄N₄ molecules show positional disorder, which very probably is of dynamical type for the S₅N₅^⊕ ion. The [As₈Cl₂₈]^4? ions can be described as a (so far unknown) [As₄Cl₁₆]^4? ion with cubane-like structure (As? Cl bridging distances between 286 and 305 pm) to which four AsCl₃ molecules are attached via chloro bridges with As? Cl bond lengths between 314 and 328 pm.     

A topological equivalent-orbital approach to the bonding in some tetrahedral molecules

The electronic structures of the tetrahedral molecules P₄, Be₄(OAc)₆O, [PtMe₃Cl]₄, [Cu I As Me₃]₄, [Tl OR]₄, [Li Me]₄ and B₄ are discussed using a simple topological equivalent(-)orbital approach.

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Zusammenfassung Die Elektronenstrukturen der tetraedrischen Moleküle P₄, Be₄(OAc)₆O, [PtMe₃Cl]₄, [Cu I As Me₃]₄, [Tl OR]₄, [Li Me]₄ und B₄ werden diskutiert unter Benutzung einer einfachen Näherung topologisch äquivalenter Orbitale.

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Résumé Les structures électroniques des molécules tétraédriques P₄, Be₄(OAC)₆O, [PtMe₃Cl]₄, [Cu I As Me₃]₄, [Tl OR]₄, [Li Me]₄ et B₄ sont discutées en usant d'une approche simple par des orbitales équivalentes topologiques.