Neue mehrkernige Indium–Stickstoff‐Verbindungen – Synthese und Kristallstrukturen von [In4X4(NtBu)4] (X = Cl,Br, I) und [In3Br4(NtBu)(NHtBu)3]

New Polynuclear Indium Nitrogen Compounds – Synthesis and Crystal Structures of [In₄X₄(N^tBu)₄] (X = Cl, Br, I) and [In₃Br₄(N^tBu)(NH^tBu)₃] The reaction of the indium trihalides InX₃ (X = Cl, Br, I) with LiNH^tBu in THF leads to the In₄N₄‐heterocubanes [In₄X₄(N^tBu)₄] (X = Cl 1 , Br 2 , I 3 ). Additionally [In₃Br₄(N^tBu)(NH^tBu)₃] ( 4 ) was obtained as a by‐product in the synthesis of 2 . 1 – 4 have been characterized by x‐ray crystal structure analysis. 1 – 3 consist of In₄N₄ heterocubane cores with an alternating arrangement of In and N atoms. The In atoms are coordinated nearly tetrahedrally by three N‐atoms and a terminal halogen atom. 4 contains a tricyclic In₃N₄ core which can be formally derived from an In₄N₄‐heterocubane by removing one In atom.     

Ein neuer Aluminium/Nickel/Oxo‐Cluster: [Ni(acac)OAl(OtBu)2]4

A New Aluminum/Nickel/Oxo‐Cluster: [Ni(acac)OAl(OtBu)₂]₄ When bis(tert‐butoxy)alane (tBu‐O)₂AlH is allowed to react with nickeldiacetylacetonate at elevated temperature a new nickel/aluminum/oxo cluster [Ni(acac)OAl(OtBu)₂]₄ is formed together with aluminum acetylacetonate Al(acac)₃ and some other products. The metal/oxo cluster is isolated by crystallization and structurally fully characterized by X‐ray diffraction analysis. The molecule [Ni(acac)OAl(OtBu)₂]₄ contains an eight membered Al₄O₄ cycle, to which eight mutually edge sharing NiO₂Al cycles are fused. The overall point symmetry of the metal/oxo cluster is almost S₄. While the aluminum atoms are tetrahedrally surrounded by oxygen ligands (mean distances Al‐O in‐between 1, 730(6) and 1, 789(6) Å)), the nickel atoms are in a square pyramidal coordination sphere of oxygen atoms (Ni‐O_axial = 1.938(6) Å, Ni‐O_basal = 2.056(9) Å; all polyhedra are distorted). The nickel atoms have a d⁸ high spin electron configuration (μ_eff = 3.32 B.M.).     

Facile, aprotic degradation of η-CpZrCl3·dme by ternary sodium/group 14 tert-butoxides: From η-CpZrCl3·dme back to NaCp in two easy steps

CpZrCl₃·dme was treated with Na[El(O^tBu)₃], El = Ge, Sn, Pb, respectively. The addition of Na[Sn(O^tBu)₃] to CpZrCl₃·dme caused rapid cyclopentadienide loss and the equally rapid appearance of CpSnCl, half of which crystallized as the trinuclear complex {[ZrCl(O^tBu)₃]₂·CpSnCl}. Pristine CpSnCl reacted almost instantly with NaO^tBu to give NaCp and Na[Sn(O^tBu)₃], which co-crystallized as a coordination polymer. Na[Ge(O^tBu)₃] also displaced Cp from zirconium, but with a different product distribution, giving Cp₂Ge, fac-[Ge(μ-^tBuO)₃ZrCl(O^tBu)₂], and ZrCl(O^tBu)₃. By contrast, Na[Pb(O^tBu)₃] only exchanged its tert-butoxide groups with zirconium to furnish CpZr(O^tBu)₃ and PbCl₂. The solid-state structures of {[ZrCl(O^tBu)₃]₂·CpSnCl}, fac-[Ge(μ-^tBuO)₃ZrCl(O^tBu)₂], and {NaCp·Na[Sn(O^tBu)₃]}_n were determined.     

Ein ungewöhnlicher ambivalenter Zinn(II)‐oxo‐Cluster

An Unusual Ambivalent Tin(II)‐oxo Cluster The reaction of the copper aryl CuDmp (Dmp = 2, 6‐Mes₂C₆H₃; Mes = 2, 4, 6‐Me₃C₆H₂) with the stannanediyl Sn{1, 2‐(tBuCH₂N)₂C₆H₄} followed by hydrolysis affords in the presence of lithium‐tert‐butoxide the tin(II)‐oxo cluster {(Et₂O)(LiOtBu)(SnO)(CuDmp)}₂ ( 5 ) in small yield. The solid state structure of the colorless compound shows a central Li₂Sn₂O₂(OtBu)₂ fragment with heterocubane structure. In addition, the Li‐acceptor and O(Sn)‐donor atoms are used for the coordination of one molecule diethylether and copper aryl CuDmp, respectively.     

Synthese und Charakterisierung von InIII–SnII‐Halogenido‐Alkoxiden und von Indiumtri‐tert‐butoxid

Synthesis and Characterization of In^III–Sn^II‐Halogenido‐Alkoxides and of Indiumtri‐ tert ‐butoxide Through sodium halide elimination between Indium(III) halides and sodium‐tri‐tert‐butoxistannate(II) or sodium‐tri‐tert‐butoxigermanate(II) the three new heterometallic and heteroleptic alkoxo compounds THF · Cl₂In(OtBu)₃Sn ( 1 ), THF · Br₂In(OtBu)₃Sn ( 2 ), and THF · Cl₂In‐ (OtBu)₃Ge ( 3 ), have been synthesized. The molecular structures of 1 and 2 in the solid state follow from single crystal X‐ray structure determinations while structural changes in solution may be derived from temperature dependant NMR spectroscopy. The crystal structures of compounds 1 and 2 are despite different halide atoms isostructural. Both crystallize in the ortho‐rhombic crystal system in space group Pbca with eight molecules per unit cell. The heavy atoms occupy the apical positions of empty trigonal bipyramids of almost point symmetry C_s(m) and are connected through oxygen atoms occupying the equatorial positions. The indium atoms in both compounds are in the centers of distorted octahedra from 4 oxygen and 2 halogen atoms whereas the tin atoms are coordinated by three oxygen atoms in a trigonal pyramidal fashion. Although the coordinative bonding of THF to indium leads to an asymmetry of the molecule the NMR spectra in solution are simple showing a more complex pattern at lower temperatures. Tri(tert‐butoxi)indium [In(OtBu)₃]₂ ( 4 ), is obtained through alcoholysis of In(N(Si(CH₃)₃)₂)₃ using tert‐butanol in toluene and is crystallized from hexane. The X‐ray structure determination of 4 seems to be the first one of a homoleptic and homometallic indiumalkoxide. Compound 4 crystallizes in the monoclinic crystal system in a dimeric form with eight molecules in the unit cell of space group C2/c. The dimeric units have C₂ symmetry and an almost planar In₂O₂ ring which originates from oxygen bridging of the monomers. Through this mutual Lewis acid base interaction the indium atoms get four oxygen ligands in a distorted tetrahedral environment.     

Chalcogenide Derivatives of Imidotin Cage Complexes

Reaction of the secocubane [Sn₃(μ₂‐NHtBu)₂(μ₂‐NtBu)(μ₃‐NtBu)] ( 1 ) with dibutylmagnesium produces the heterobimetallic cubane [Sn₃Mg(μ₃‐NtBu)₄] ( 4 ) which forms the monochalcogenide complexes of general formula [ESn₃Mg(μ₃‐NtBu)₄] ( 5 a , E=Se; 5 b , E=Te) upon reaction with elemental chalcogens in THF. By contrast, the reaction of the anionic lithiated cubane [Sn₃Li(μ₃‐NtBu)₄]^? with the appropriate quantity of selenium or tellurium leads to the sequential chalcogenation of each of the three Sn^II centres. Pure samples of the mono‐ or dichalcogenides are, however, best obtained by stoichiometric redistribution reactions of [Sn₃Li(μ₃‐NtBu)₄]^? and the trichalcogenides [E₃Sn₃Li(μ₃‐NtBu)₄]^? (E=Se, Te). These reactions are conveniently monitored by using ¹¹⁹Sn NMR spectroscopy. The anion [Sn₃Li(μ₃‐NtBu)₄]^? also acts as an effective chalcogen‐transfer reagent in reactions of selenium with the neutral cubane [{Snμ₃‐N(dipp)}₄] ( 8 ) (dipp=2,6‐diisopropylphenyl) to give the dimer [(thf)Sn{μ‐N(dipp)}₂Sn(μ‐Se)₂Sn{μ‐N(dipp)}₂Sn(thf)] ( 9 ), a transformation that results in cleavage of the Sn₄N₄ cubane into four‐membered Sn₂N₂ rings. The X‐ray structures of 4 , 5 a , 5 b , [Sn₃Li(thf)(μ₃‐NtBu)₄(μ₃‐Se)(μ₂‐Li)(thf)]₂ ( 6 a ), [TeSn₃Li(μ₃‐NtBu)₄][Li(thf)₄] ( 6 b ), [Te₂Sn₃Li(μ₃‐NtBu)₄][Li([12]crown‐4)₂] ( 7 b′′ ) and 9 are presented. The fluxional behaviour of cubic imidotin chalcogenides and the correlation between NMR coupling constants and tin–chalcogen bond lengths are also discussed.     

Neue Zinn‐reiche Stannide der Systeme AII‐Al‐Sn (AII = Ca,Sr, Ba)

New Tin‐rich Stannides of the Systems A^II‐Al‐Sn (A^II = Ca, Sr, Ba) Four new tin‐rich intermetallics of the ternary systems Ca/Sr/Ba‐Al‐Sn were synthesized from stoichiometric amounts of the elements at maximum temperatures of 1200 °C. Their crystal structures, representing two new types, have been determined using single crystal x‐ray diffraction. Close to the 1:1 composition, the structures of the two isotypic compounds A₁₈[Al₄(Al/Sn)₂Sn₄][Sn₄][Sn]₂ (overall composition A₉M₈; A = Sr/Ba, tetragonal, space group P4/mbm, a = 1325.9(1)/1378.6(1), c = 1272.8(2)/1305.4(1) pm, Z = 4, R1 = 0.0430/0.0293) contain three different anionic Sn/Al building units: Isolated Sn atoms (motif I) coordinated by the alkaline earth cations only (comparable to Ca₂Sn), linear Sn chains (II), which are comparable to the anions in trielides related to the W₅Si₃ structure type and finally octahedral clusters [Al₄M₂Sn₄] (III), composed of four Al atoms forming the center plane, two statistically occupied Al/Sn atoms at the apexes and four exohedral Sn attached to Al. Close to the AM₂ composition, two isotypic tin‐rich intermetallics A₉[Al₃Sn₂][(Sn/Al)₄]Sn₆ (overall composition A₉M₁₅; A = Ca/Sr; space group C2/m, a = 2175.2(1)/2231.0(2), b = 1210.8(1)/1247.0(1), c = 1007.4(1)/1042.0(2) pm, β = 103.38(1)/103.42(1)°, Z = 2, R1 = 0.0541/0.0378) are formed. Their structure is best described as a complex three‐dimensional network, that can be considered to consist of the building units of the binary border phases too, i.e. linear zig‐zag chains of Sn (motif I) like in CaSn, ladders of four‐bonded Sn/Al atoms (II) like in SrAl₂ and trigonal‐bipyramidal clusters [Al₃Sn₂] (III) also present in Ba₃Al₅. Despite the complex structures, some statistically occupied Al/Sn positions and the small disorder of one building unit, the bonding in both structure types can be interpreted using the Zintl concept and Wade's electron counting rules when taking partial Sn‐Sn bonds into account.     

Synthesen und Reaktionen von Aluminiumalkoxid‐Verbindungen

Syntheses and Reactions of Aluminium Alkoxide Compounds Al(O^cHex)₃ ( 1 ) can be synthesized by the reaction of Al with cyclohexanol under evolving of H₂ in boiling xylene. [Li{Al(OCH₂Ph)₄}] ( 2 ) was obtained by treatment of PhCH₂OH with a 1 M solution of LiAlH₄ in THF. [{(THF)Li}₂{Al(O^tBu)₄}Cl] ( 3 ) is the result of the reaction of four equivalents of LiO^tBu on AlCl₃ in THF. 3 is the educt for the reactions with the Lewis‐acids InCl₃ and FeCl₃ in THF leading to the metalates [{(THF)₂Li}₂{Al(O^tBu)₄}] · [MCl₄] [M = In ( 4 ), Fe ( 5 )]. The attempt to react InCl₃ with four equivalents of LiO^tBu leads to only one isolated and characterized product, the complex [Li₄(O^tBu)₃(THF)₃Cl]₂ · THF ( 6 · THF), which can also be synthesized by the treatment of LiCl with three equivalents of LiO^tBu in THF. 1–6 · THF were characterized by NMR, IR and MS techniques as well as by X‐ray structure determinations. According to them, 1 , which is tetrameric in solution, is the first structurally characterized example of the proposed trimer form of aluminium alkoxides [ROAl{Al(OR)₄}₂] with a central trigonal bipyramidal coordinated Al atom. 2 forms a coordination polymer with a distorted tetrahedral coordination sphere of Li and Al, running along [100]. The trinuclear structure skeleton [{(THF)₂Li}₂{Al(O^tBu)₄}]⁺ is still present in the isotypical metalates 4 and 5 . The counter ions [MCl₄]^– possess nearly T_d symmetry. The remarkable structural motif of 6 · THF are two heterocubanes [Li₄(O^tBu)₃(THF)₃Cl] dimerized by Li–Cl bonds.     

Chalcogenide Derivatives of the seco‐Cubane [Sn3(μ2‐NHtBu)2(μ2‐NtBu)(μ3‐NtBu)]

A series of monochalcogenide derivatives of the seco‐cubane [Sn₃(μ₂‐NHtBu)₂(μ₂‐NtBu)(μ₃‐NtBu)] has been prepared and characterized by NMR and X‐ray crystallographic studies. These complexes exhibit different tin‐chalcogen bonding modes. In the case of the monotelluride, a terminal Sn=Te bond was observed in solution and in the solid state, whereas for the monosulfide, a μ₂ bridging mode was adopted by the sulfur atoms. The monoselenide was found to employ both bonding modes in solution, although only the terminal Sn=Se bonding mode was structurally characterized. The complexes undergo chalcogen exchange between tin atoms in solution, and this process was studied by variable temperature NMR.     

LSn(OCH2CH2)2NR (L = lone pair,W(CO)5; R = Me,t‐Bu). The Molecular Structures of 5‐Aza‐2,8‐dioxa‐1‐stannabicyclo[3.3.0]1.5octanes and Their Tungstenpentacarbonyl Complexes

Single crystal X‐ray diffraction analyses of LSn(OCH₂CH₂)₂NR [ 1 , R = Me, L = lone pair; 2 , R = Me, L = W(CO)₅; 3 , R = t‐Bu, L = W(CO)₅] reveal these compounds to be dimeric and cis‐configurated. The dimerization is realized by intramolecular O→Sn interactions to give four‐membered Sn₂O₂‐rings. In addition, there are intramolecular N→Sn interactions ranging in between 2.356(5) ( 2 ) and 2.549(4) Å ( 3 ).     

The [Sn5]2– Cluster Compound [K‐(2,2,2‐crypt)]2Sn5 – Synthesis,Crystal Structure,Raman Spectrum,and Hierarchical Relationship to CaIn2

Dark red crystals of [K‐(2,2,2)‐crypt)]₂Sn₅ precipitate after the reaction of (2,2,2)‐crypt with a solution of K_1.33Sn in liquid ammonia at room temperature. The compound is sensitive to oxidation and hydrolysis. The sequence of Raman bands (104, 120, 133 and 180 cm^–1) is characteristic for the trigonal bipyramidal closo‐[Sn₅]^2– cluster anion. The wave numbers correspond with the data from Hartree‐Fock calculations (114, 128, 142 and 187 cm^–1). The compound crystallizes trigonally (a = 11.736 Å, c = 22.117 Å, Z = 2, space group P3c1 (No. 165); Pearson code hP262), isotypic with [Na‐(2,2,2)‐crypt)]₂Pb₅. The atoms of the cluster show strange anisotropic displacements, which are perfectly reducible to a helical rigid‐body motion around and along [001] (libration: ± 9.5°; translation ± 0.29 Å). The structure can be described as a hierarchical derivative of the initiator CaIn₂ (P6₃/mmc, hP6), generated by an atom‐to‐aggregate replacement: [Ca][In]₂ = [Sn₅][K @ C₃₆H₇₂N₄O₁₂]₂. Thus, the distribution of the [Sn₅]^2– Zintl anions is hexagonal primitive, and the cation complexes are located close to the centers of trigonal superprisms formed by Sn₅ clusters.     

Oxygen‐Atom Transfer Chemistry and Thermolytic Properties of a Di‐tert‐Butylphosphate‐Ligated Mn4O4 Cubane

[Mn₄O₄{O₂P(OtBu)₂}₆] ( 1 ), an Mn₄O₄ cubane complex combining the structural inspiration of the photosystem II oxygen‐evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen‐atom acceptor (PEt₃), to give the butterfly complex [Mn₄O₂{O₂P(OtBu)₂}₆(OPEt₃)₂]. The cubane structure is restored by reaction of the latter complex with the O‐atom donor PhIO. Complex 1 was investigated as a precursor to inorganic Mn metaphosphate/pyrophosphate materials, which were studied by X‐ray absorption spectroscopy to determine the fate of the Mn₄O₄ unit. Under the conditions employed, thermolyses of 1 result in reduction of the manganese to Mn^II species. Finally, the related butterfly complex [Mn₄O₂{O₂P(pin)}₆(bpy)₂] (pin=pinacolate) is described.     

Synthesis,structure and antitumor activity of dibutyltin oxide complex with 5‐fluorouracil derivatives

The dibutyltin(IV) oxide complex reacts with 5‐fluorouracil‐l‐propanonic or5‐fluorouracil‐1‐acetic acid to give the potential antitumor activity complexes [(5‐fluorouracil)‐1‐(CH₂)_mCOOSn(Bu‐n)₂]₄O₂[m = 1, (1); m = 2, (2)] which were determined by IR and ¹H NMR. The crystal structure determination shows that complex 2 is a dimmer, in which two [(5‐fluorouracil)‐1‐CH₂CH₂COOSn(Bu‐n)₂]₂O units are linked by bridging oxygen atom, and the tin atoms adopt distorted trigonal bipyramids via two carbons from dibutyl group and three oxygen atoms from 5‐fluorouracil and bridging oxygen. In vitro test shows complexes 1 and 2 exhibit high cytotoxicity against OVCAR‐3 and PC‐14.     

Tetrakis(μ2‐4‐aminobenzoato)di‐μ3‐oxido‐tetrakis[dibutyltin(IV)]

The molecule of the title compound, [Sn₄(C₄H₉)₈(C₇H₆NO₂)₄O₂], lies about an inversion centre and is a tetranuclear bis(tetrabutyldicarboxylatodistannoxane) complex containing a planar Sn₄O₂ core in which two μ₃‐oxide O atoms connect an Sn₂O₂ ring to two exocyclic Sn atoms. Each Sn atom has a highly distorted octahedral coordination. In the molecule, the carboxylate groups of two aminobenzoate ligands bridge the central and exocyclic Sn atoms, while two further aminobenzoate ligands have highly asymmetric bidentate chelation to the exocyclic Sn atoms plus long O...Sn interactions with the central Sn atoms. Each Sn atom is also coordinated by two pendant n‐butyl ligands, which extend roughly perpendicular to the plane of the Sn₄O₁₀ core. Only one of the four unique hydrogen‐bond donor sites is involved in a classic N—H...O hydrogen bond, and the resulting supramolecular hydrogen‐bonded structure is an extended two‐dimensional network which lies parallel to the (100) plane and consists of a checkerboard pattern of four‐connected molecular cores acting as nodes. The amine groups not involved in the hydrogen‐bonding interactions have significant N—H...π interactions with neighbouring aminobenzene rings.     

Site Preference in Multimetallic Nanoclusters: Incorporation of Alkali Metal Ions or Copper Atoms into the Alkynyl‐Protected Body‐Centered Cubic Cluster [Au7Ag8(C≡CtBu)12]+

The synthesis, structure, substitution chemistry, and optical properties of the gold‐centered cubic monocationic cluster [Au@Ag₈@Au₆(C≡C^tBu)₁₂]⁺ are reported. The metal framework of this cluster can be described as a fragment of a body‐centered cubic (bcc) lattice with the silver and gold atoms occupying the vertices and the body center of the cube, respectively. The incorporation of alkali metal atoms gave rise to [M_nAg_8?nAu₇(C≡C^tBu)₁₂]⁺ clusters (n=1 for M=Na, K, Rb, Cs and n=2 for M=K, Rb), with the alkali metal ion(s) presumably occupying the vertex site(s), whereas the incorporation of copper atoms produced [Cu_nAg₈Au_7?n(C≡C^tBu)₁₂]⁺ clusters (n=1–6), with the Cu atom(s) presumably occupying the capping site(s). The parent cluster exhibited strong emission in the near‐IR region (λ_max=818 nm) with a quantum yield of 2 % upon excitation at λ=482 nm. Its photoluminescence was quenched upon substitution with a Na⁺ ion. DFT calculations confirmed the superatom characteristics of the title compound and the sodium‐substituted derivatives.     

Synthesis,properties and crystal structural characterization of diorganotin(IV) derivatives of 2‐mercapto‐6‐nitrobenzothiazole

The diorganotin(IV) dichlorides R₂SnCl₂ (R: Ph, PhCH₂ or n‐Bu) react with 2‐mercapto‐6‐nitrobenzothiazole (MNBT) in benzene to give [Ph₂SnCl(MNBT)] ( 1 ), [(PhCH₂)₂Sn(MNBT)₂] ( 2 ) and [(n‐Bu)₂Sn(MNBT)₂] ( 3 ). The three complexes have been characterized by elemental analysis and IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopies. X‐ray studies of the crystal structures of 1 , 2 and 3 show the following. The tin environment for complex 1 is distorted cis‐trigonal bipyramid with chlorine and nitrogen atoms in apical positions. The structure of complex 2 is a distorted octahedron with two benzyl groups in the axial sites. The geometry at the tin atom of complex 3 is that of an irregular octahedron. Interestingly, intra‐molecular non‐bonded Cl…S interactions and S…S interaction were recognized in the crystallographic structures of 1 and 3 respectively. As a result, complex 1 is a polymer and complex 3 is a dimer. Copyright © 2003 John Wiley & Sons, Ltd.     

Indium‐Bridged [1]Ferrocenophanes

Indium‐bridged [1]ferrocenophanes ([1]FCPs) and [1.1]ferrocenophanes ([1.1]FCPs) were synthesized from dilithioferrocene species and indium dichlorides. The reaction of Li₂fc?tmeda (fc=(H₄C₅)₂Fe) and (Mamx)InCl₂ (Mamx=6‐(Me₂NCH₂)‐2,4‐tBu₂C₆H₂) gave a mixture of the [1]FCP (Mamx)Infc ( 4₁ ), the [1.1]FCP [(Mamx)Infc]₂ ( 4₂ ), and oligomers [(Mamx)Infc]_n ( 4 _n ). In a similar reaction, employing the enantiomerically pure, planar‐chiral (S_p,S_p)‐1,1′‐dibromo‐2,2′‐diisopropylferrocene ( 1 ) as a precursor for the dilithioferrocene derivative Li₂fc^iPr2, equipped with two iPr groups in the α position, gave the inda[1]ferrocenophane 5₁ [(Mamx)Infc^iPr2] selectively. Species 5₁ underwent ring‐opening polymerization to give the polymer 5 _n . The reaction between Li₂fc^iPr2 and Ar′InCl₂ (Ar′=2‐(Me₂NCH₂)C₆H₄) gave an inseparable mixture of the [1]FCP Ar′Infc^iPr2 ( 6₁ ) and the [1.1]FCP [Ar′Infc^iPr2]₂ ( 6₂ ). Hydrogenolysis reactions (BP86/TZ2P) of the four inda[1]ferrocenophanes revealed that the structurally most distorted species ( 5₁ ) is also the most strained [1]FCP.     

Dioxygen Activation by Non‐Adiabatic Oxidative Addition to a Single Metal Center

A chromium(I) dinitrogen complex reacts rapidly with O₂ to form the mononuclear dioxo complex [Tp^tBu,MeCr^V(O)₂] (Tp^tBu,Me=hydrotris(3‐tert‐butyl‐5‐methylpyrazolyl)borate), whereas the analogous reaction with sulfur stops at the persulfido complex [Tp^tBu,MeCr^III(S₂)]. The transformation of the putative peroxo intermediate [Tp^tBu,MeCr^III(O₂)] (S=³/₂) into [Tp^tBu,MeCr^V(O)₂] (S=¹/₂) is spin‐forbidden. The minimum‐energy crossing point for the two potential energy surfaces has been identified. Although the dinuclear complex [(Tp^tBu,MeCr)₂(μ‐O)₂] exists, mechanistic experiments suggest that O₂ activation occurs on a single metal center, by an oxidative addition on the quartet surface followed by crossover to the doublet surface.     

Synthesis,Spectroscopic, and X‐Ray Diffraction Studies of cis‐Dichlorobis(4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl3 H‐pyrazol‐3‐onato) Tin(IV)

Reaction between an aqueous ethanol solution of tin(II) chloride and that of 4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl‐3 H‐pyrazol‐3‐one in the presence of O₂ gave the compound cis‐dichlorobis(4‐propanoyl‐2,4‐dihydro‐5‐methyl‐2‐phenyl‐3 H‐pyrazol‐3‐onato) tin(IV) [(C₂₆H₂₆N₄O₄)SnCl₂]. The compound has a six‐coordinated Sn^IV centre in a distorted octahedral configuration with two chloro ligands in cis position. The tin atom is also at a pseudo two‐fold axis of inversion for both the ligand anions and the two cis‐chloro ligands. The orange compound crystallizes in the triclinic space group P 1 with unit cell dimensions, a = 8.741(3) Å, b = 12.325(7) Å, c = 13.922(7) Å; α = 71.59(4), β = 79.39(3), γ = 75.18(4); Z = 2 and D_x = 1.575 g cm^–3. The important bond distances in the chelate ring are Sn–O [2.041 to 2.103 Å], Sn–Cl [2.347 to 2.351 Å], C–O [1.261 to 1.289 Å] and C–C [1.401 Å] the bond angles are O–Sn–O 82.6 to 87.7° and Cl–Sn–Cl 97.59°. The UV, IR, ¹H NMR and ¹¹⁹Sn Mössbauer spectral data of the compound are reported and discussed.     

Synthese und Charakterisierung der Siloxialane [H2AlOSiMe3]n und [HAl(OtBu)(OSiMe3)]2 sowie Redoxreaktionen von [H2AlOSiMe3]n und [H2AlOtBu]2 mit einem Zinn(II)‐amid

Synthesis and Characterisation of the Siloxialanes [H₂AlOSiMe₃]_n and [HAl(O^tBu)(OSiMe₃)]₂ as well as the Use of [H₂AlOSiMe₃]_n and [H₂AlO^tBu]₂ as Reducing Agents for a Tin(II) Amide Following the synthesis of [H₂AlO^tBu]₂ ( 1 ) and [HAl(O^tBu)₂]₂ ( 2 ) the siloxialane [H₂AlOSiMe₃]_n ( 3 ) was synthesized and has been subject to single crystal X‐ray analysis for the first time. The molecule 3 is tetrameric (n = 4) in solution and polymeric (n = ∞) in the solid state. 3 is also obtained together with the siloxide [Al(OSiMe₃)₃]₂ ( 5 ) by the reaction of the aluminiumhydride with the double molar amount of trimethylsilanol. The expected monohydride [HAl(OSiMe₃)₂]₂ ( 4 ) was not formed. The heteroleptic monohydride [HAl(O^tBu)(OSiMe₃)]₂ ( 6 ) was synthesized by the reaction of 3 with an equimolar amount of tert‐butanol and was also generated by the addition of trimethylsilanol to an equimolar amount of the alkoxialane [H₂AlO^tBu]₂ ( 1 ). Compound 6 was characterized by single crystal X‐ray diffraction analysis. Additionally we investigated the reducing force of the dihydrides 1 and 3 towards the cyclic diazastannylene Me₂Si(N^tBu)₂Sn ( 7 ). In the course of this reaction Sn^II in 7 was reduced to elementary tin whereas the hydrides were oxidized to hydrogene. Tin is obtained in its β‐form as found by powder‐X‐ray diffraction. The shapes of the metal precipitates (porous, sponge‐like pieces or nanoscaled powders) depend on the conditions of reactions. Besides the elements the spirocyclic aminoalkoxialane [Me₂Si(N^tBu)₂AlO^tBu]₂ ( 8 ) or aminosiloxialane [Me₂Si(N^tBu)₂AlOSiMe₃]₂ ( 9 ) are formed. Structural details of the molecules 8 and 9 can be derived from single crystal X‐ray analyses.