Die Reaktion des Digalliumsubiodids R(I)Ga‐Ga(I)R [R = C(SiMe3)3] mit Lithium‐diphenylphosphanid – radikalische Öffnung der Ga‐Ga‐Bindung

The Reaction of the Digallium Subiodide R(I)Ga‐Ga(I)R [R = C(SiMe₃)₃] with Lithium Diphenylphosphanide – Radical Cleavage of the Ga‐Ga Bond The easily available organoelement digallium(II) subiodide R(I)Ga‐Ga(I)R ( 1 ) [R = C(SiMe₃)₃] reacted with two equivalents of lithium diphenylphosphanide in toluene by the replacement of both iodine atoms by two phosphanido groups. The product, [R(H)Ga‐P(C₆H₅)₂]₂ ( 2 ), contains a four‐membered Ga₂P₂ heterocycle without direct Ga‐Ga bonding interactions and the gallium atoms exclusively in an oxidation state of +III. They are attached to hydrogen atoms, which may result from a reaction of a reactive intermediate with the solvent.     

Reaktionen der Digalliumverbindung R2Ga–GaR2 [R = CH(SiMe3)2] mit Wasser und Carbonsäuren – Synthese von μ‐Hydroxo‐μ‐carboxylatodigallium‐Verbindungen unter Erhalt der Ga–Ga‐Bindungen

Treatment of the digallium compound R₂Ga–GaR₂ [ 1 , R = CH(SiMe₃)₂] with a broad variety of functionalized carboxylic acids in the presence of water yielded μ‐hydroxo‐μ‐carboxylatodigallium compounds ( 2 – 10 ) containing intact Ga–Ga bonds in high to moderate yields. The compounds form dimeric formula units in which the unsupported Ga–Ga bonds are bridged by two hydroxo and two carboxylato ligands. Each gallium atom is terminally coordinated by a bulky alkyl group. NMR spectroscopy revealed mixtures of two isomeric compounds in solution in all cases. The second component may show a different bridging mode with each Ga–Ga bond bridged by a bidentate carboxylato ligand to form Ga₂O₂C five‐membered heterocycles.     

Donorstabilisierte Galliumdihalogenide Ga2X4·2D (X = Cl,Br; D = Donormolekül): Ein experimenteller Beitrag zu den Variationsmöglichkeiten der Ga‐Ga‐Einfachbindung

Donor‐stabilized Galliumdihalides Ga₂X₄·2D (X = Cl, Br; D = Donor): An Experimental Contribution on the Variation of the Gallium‐Gallium Single Bond During the disproportionation of metastable GaX‐solutions (X= Cl, Br) donor‐stabilized galliumdihalides are formed as oxidized products. According to X‐ray structure analyses they all exhibit dimeric entities DX₂Ga‐GAX₂D (D= THF, NHEt2, NEt3, 4‐^tButylpyridin or Br^‐), which means these compounds are isoelectronic with ethane and could schematically be regarded as representatives of catenulate or alkane‐like gallium subhalides: Ga_n(X, D)_2n+2. The gallium‐gallium bond in these compounds is shorter than in the organometallic compounds such as R₂Ga‐GaR₂. The comparison of the bonding situation in the galliumdihalides, particularly of the gallium‐gallium bond, shows clearly the influence by donor molecules as well as by halogen ligands.     

1,4‐Di(isopropyl)‐1,4‐diazabutadien als Abfangreagenz für monomere Bruchstücke des Tetragalliumclusters Ga4[C(SiMe3)3]4 – Bildung eines ungesättigten GaN2C2‐Heterocyclus und eines Oxidationsprodukts mit Ga‐O‐O‐Ga‐Gruppe

1,4‐Di(isopropyl)‐1,4‐diazabutadiene as a Reagent for the Trapping of Monomeric Fragments of the Tetragalliumcluster Ga₄[C(SiMe₃)₃]₄ – Formation of an Unsaturated GaN₂C₂ Heterocycle and an Oxidation Product Containing a Ga‐O‐O‐Ga Group The tetrahedral tetragallium cluster Ga₄[C(SiMe₃)₃]₄ ( 1 ) dissociates upon dissolution to yield the monomeric fragments Ga‐R [R = C(SiMe₃)₃]. These monomers could be trapped now by the treatment of their solutions with 1,4‐di(isopropyl)‐1,4‐diazabutadiene. The product of the cycloaddition reaction ( 2 ) possesses a five‐membered GaN₂C₂ heterocycle with a coordinatively unsaturated gallium atom and an endocyclic C=C double bond. 2 is rather sensitive towards oxidation by traces of air. The contact with oxygen yielded a digallium peroxide [(C₂N₂iPr₂)RGa‐O‐O‐GaR(C₂N₂iPr₂)] ( 3 ) which was isolated in a very low yield only and which has a gallium atom attached to each oxygen atom of the inner peroxo group. Both chelating ligands of 3 possess an unpaired electron.     

New Ga/N‐based Active Lewis Pairs,Trifunctional Ga–Ga Compounds,Reactions with Cyanamide and Dual Insertion of Isocyanate

Hydrogallation of Me₃Si–C≡C–NR'₂ with R₂Ga–H (R = tBu, CH₂tBu, iBu) yielded Ga/N‐based active Lewis pairs, R₂Ga–C(SiMe₃)=C(H)–NR'₂ ( 7 ). The Ga and N atoms adopt cis‐positions at the C=C bonds and show weak Ga–N interactions. tBu₂GaH and Me₃Si–C≡C–N(C₂H₄)₂NMe afforded under exposure of daylight the trifunctional digallium(II) compound [MeN(C₂H₄)₂N](H)C=C(SiMe₃)Ga(tBu)–Ga(tBu)C(SiMe₃)=C(H)[N(C₂H₄)₂NMe] ( 8 ), which results from elimination of isobutene and H₂ and Ga–Ga bond formation. 8 was selectively obtained from the ynamine and [tBu(H)Ga–Ga(H)tBu]₂[HGatBu₂]₂. 7a (R = tBu; NR'₂ = 2,6‐Me₂NC₅H₈) and H₈C₄N–C≡N afforded the adduct tBu₂Ga‐C(SiMe₃)=C(H)(2,6‐Me₂NC₅H₈) · N≡C–NC₄H₈ ( 11 ) with the nitrile bound to gallium. The analogous ALP with harder Al atoms yielded an adduct of the nitrile dimer or oligomers of the nitrile at room temperature. The reaction of 7a with Ph–N=C=O led to the insertion of two NCO groups into the Ga–C_vinyl bond to yield a GaOCNCN heterocycle with Ga bound to O and N atoms ( 12 ).     

The Gallides SrRh2Ga2, SrIr2Ga2, and Sr3Ir4Ga4

The gallides SrRh₂Ga₂, SrIr₂Ga₂, and Sr₃Rh₄Ga₄ were obtained from the elements by induction melting and subsequent annealing. They were investigated by powder and single‐crystal X‐ray diffraction: CaRh₂B₂ type, Fddd, a = 573.2(1), b = 1051.3(1), c = 1343.7(2) pm, wR₂ = 0.0218, 398 F² values, 15 variables for SrRh₂Ga₂; a = 576.0(1), b = 1045.5(1), c = 1350.6(3) pm for SrIr₂Ga₂, and Na₃Pt₄Ge₄ type, I$\bar{4}$ 3m, a = 777.4(2) pm, wR₂ = 0.0234, 190 F² values, 11 variables for Sr₃Ir₄Ga₄. The gallides SrRh₂Ga₂ and Sr₃Ir₄Ga₄ exhibit complex, covalently bonded three‐dimensional [Rh₂Ga₂] and [Ir₄Ga₄] networks with short Rh–Ga (241–246 pm) and Ir–Ga (243–259 pm) distances. The strontium atoms fill large cages within these networks. They are coordinated by 8 Rh + 10 Ga in SrRh₂Ga₂ and by 4 Ir + 8 Ga in Sr₃Ir₄Ga₄. The structure of SrRh₂Ga₂ is discussed along with the monoclinic distortion variants HoNi₂B₂ and BaPt₂Ga₂ on the basis of a group‐subgroup scheme.     

Gallium‐Indium Ordering in the Complex [Ni2Ga3In] Network of GdNi2Ga3In

Polycrystalline samples of the isotypic quaternary compounds RENi₂Ga₃In (RE = Y, Gd – Tm) were obtained by arc‐melting of the elements. Crystals of the gadolinium compound were found by slow cooling of an arc‐melted button of the initial composition “GdNiGa₃In”. All samples were characterized by powder X‐ray diffraction. The structure of GdNi₂Ga_2.89In_1.11 was refined from single‐crystal X‐ray diffractometer data: new type, Pnma, a = 2426.38(7), b = 418.17(2), c = 927.27(3) pm, wR₂ = 0.0430, 1610 F² values and 88 variables. Two of the six crystallographically independent gallium sites show a small degree of Ga/In mixing. The nickel atoms show tricapped trigonal prismatic coordination by gadolinium, gallium, and indium. Together, the nickel, gallium, and indium atoms build up a complex three‐dimensional [Ni₂Ga₃In]^δ– network, which leaves cages for the gadolinium atoms. The indium atoms form zigzag chains with In–In distances of 337 pm. The crystal chemical similarities of the polyhedral packing in the GdNi₂Ga₃In and La₄Pd₁₀In₂₁ structures are discussed.     

Umsetzungen der Dielementverbindungen R2E–ER2 [E = Ga,In; R = CH(SiMe3)2] mit Lithium‐phenylethinid – Bildung von Addukten unter Erhalt der E–E‐Bindungen

Reactions of the Dielement Compounds R₂E–ER₂ [E = Ga, In; R = CH(SiMe₃)₂] with Lithium Phenylethynide – Formation of Adducts by Retention of the E–E Bonds Lithium phenylethynide reacted with the dielement compounds tetrakis[bis(trimethylsilyl)methyl]digallane(4) ( 2 ) and diindane(4) ( 3 ) as a Lewis‐base and gave by the addition of one ethynido ligand to one of the Lewis‐acidic central atoms the anionic adducts 4 and 5 with intact Ga–Ga and In–In single bonds. Thus, compounds were formed, in which tricoordinated, coordinatively unsaturated Ga or In atoms are neighbored to tetracoordinated, coordinatively saturated ones. The E–E bonds [255.83 pm in 4 (Ga–Ga) and 285.24 pm in 5 (In–In)] are only slightly lengthened compared to those of the starting compounds 2 and 3 . A dynamic behavior with a fast change of the position of the ethynido ligand was observed for both compounds in solution at room temperature.     

Das Hexagallan [Ga6{SiMe(SiMe3)2}6] und das closo‐Hexagallanat [Ga6{Si(CMe3)3}4(CH2C6H5)2]2— — der Übergang zu einem ungewöhnlichen precloso‐Cluster

The Hexagallane [Ga₆{SiMe(SiMe₃)₂}₆] and the closo‐Hexagallanate [Ga₆{Si(CMe₃)₃}₄ (CH₂C₆H₅)₂]^2— — the Transition to an Unusual precloso‐Cluster The closo hexagallanate [Ga₆R₄(CH₂Ph)₂]^2— (R = Si^tBu₃) as well as the hexagallane Ga₆R₆ (R = SiMe(SiMe₃)₂) with only six cluster electron pairs were isolated from reactions of “GaI” with the corresponding silanides. The structure of the latter is derived from an octahedron by a Jahn‐Teller‐distortion and is different from the capped trigonal bipyramidal one expected by the Wade‐Mingos rules. Both compounds were characterized by X‐ray crystallography. The bonding is discussed with simplified Ga₆H₆ and Ga₆H₆^2— models via DFT methods.     

Terminale und verbrückende Koordination von Indium‐Indium‐Bindungen – bemerkenswerte Polymorphie an der Verbindung In2R2[(OCC6H5)2CH]2 [R = C(SiMe3)3]

Terminal and Bridging Coordination of Indium‐Indium Bonds – Remarkable Polymorphism with the Compound In₂R₂[(OCC₆H₅)₂CH]₂ [R = C(SiMe₃)₃] Treatment of the dimeric indium(II) subhalide (In₂R₂Cl₂)₂ ( 1 ) [R = C(SiMe₃)₃] with four equivalents of lithium dipivaloylmethanide or lithium dibenzoylmethanide afforded by the release of lithium chloride the corresponding diindium diacetylacetonates ( 2 and 3 ). The In‐In single bonds of the products were terminally coordinated by chelating acectylacetonato ligands and the bulky alkyl groups. Three different crystal structures were determined for the dibenzoylmethanide derivative 3 which in the solid state adopted trans and gauche conformations across the In‐In bonds. In contrast to the terminally arranged acetylacetonato ligands of compounds 2 and 3 alkylbenzoato ligands R‐COO^? (3,5‐dimethylbenzoate and p‐tert‐butylbenzoate) gave the bridging coordination of the In‐In bonds by two chelating carboxylato groups ( 4 and 5 ). This particular coordination caused a strong shortening of the In‐In bond length in 4 compared to the unsupported bonds in 2 and 3 (264.6 versus 274.7 to 279.3 pm).     

Hydrogallierungsreaktionen mit den Monoalkinen H5C6‐C≡C‐SiMe3 und H5C6‐C≡C‐CMe3 – cis/trans‐Isomerie und Substituentenaustausch

Hydrogallation Reactions Involving the Monoalkynes H₅C₆‐C≡C‐SiMe₃ and H₅C₆‐C≡C‐CMe₃ – cis/trans Isomerisation and Substituent Exchange Phenyl‐trimethylsilylethyne, H₅C₆‐C≡C‐SiMe₃, reacted with different dialkylgallium hydrides, R₂Ga‐H (R = Me, Et, nPr, iPr, tBu), by the addition of one Ga‐H bond to its C≡C triple bond (hydrogallation). The gallium atoms attacked selectively those carbon atoms, which were also attached to trimethylsilyl groups. The cis arrangement of Ga and H across the resulting C=C double bonds resulted only for the sterically most shielded di(tert‐butyl)gallium derivative, while in all other cases spontaneous cis/trans rearrangement occurred with the quantitative formation of the trans addition products. The diethyl compound Et₂Ga‐C(SiMe₃)=C(H)‐C₆H₅ ( 2 ) gave by substituent exchange the secondary products EtGa[C(SiMe₃)=C(H)‐C₆H₅]₂ ( 7 , Z,Z) and Ga[C(SiMe₃)=C(H)‐C₆H₅]₃ ( 8 ). Interestingly, compound 8 has two alkenyl groups with a Z configuration, while the third C=C double bond has the cis arrangement of Ga and H (E configuration). The reversibility of the cis/trans isomerisation of hydrogallation products was observed for the first time. tert‐Butyl‐phenylethyne gave the simple addition product, R₂Ga(C₆H₅)=C(H)‐CMe₃ ( 9 ), only with di(n‐propyl)gallium hydride.     

Rare Earth Ruthenium Gallides with the Ideal Composition Ln2Ru3Ga5 (Ln = La–Nd,Sm) crystallizing with U2Mn3Si5 (Sc2Fe3Si5) Type Structure

The rare earth ruthenium gallides Ln₂Ru₃Ga₅ (Ln = La, Ce, Pr, Nd, Sm) were prepared by arc‐melting of cold‐pressed pellets of the elemental components. They crystallize with a tetragonal structure (P4/mnc, Z = 4) first reported for U₂Mn₃Si₅. The crystal structures of the cerium and samarium compounds were refined from single‐crystal X‐ray data, resulting in significant deviations from the ideal compositions: Ce₂Ru_2.31(1)Ga_5.69(1), a = 1135.10(8) pm, c = 580.58(6) pm, R_F = 0.022 for 742 structure factors; Sm₂Ru_2.73(2)Ga_5.27(2), a = 1132.95(9) pm, c = 562.71(6) pm, R_F = 0.026 for 566 structure factors and 32 variable parameters each. The deviations from the ideal compositions 2:3:5 are discussed. A mixed Ru/Ga occupancy occurs only for one atomic site. The displacement parameters are relatively large for atoms with mixed occupancy within their coordination shell and small for atoms with no neighboring sites of mixed occupancy. Chemical bonding is analyzed on the basis of interatomic distances. Ln–Ga bonding is stronger than Ln–Ru bonding. Ru–Ga bonding is strong and Ru–Ru bonding is weak. The Ga–Ga interactions are of similar strength as in elemental gallium.     

Rare Earth Metal Ruthenium Gallides R2Ru3Ga9 with Y2Co3Ga9 Type Structure

The twelve isotypic intermetallic compounds R₂Ru₃Ga₉ with R = Y, La–Nd, Sm, Gd–Tm were prepared by arc‐melting of the elemental components. Their crystal structure was determined from single‐crystal X‐ray data of Dy₂Ru₃Ga₉: Cmcm, a = 1279.3(2) pm, b = 755.6(1) pm, c = 964.7(1) pm, Z = 4, R = 0.020 for 671 structure factors and 42 variable parameters. All atomic positions have within two standard deviations ideal occupancies (occupancy values vary between 98.8(5) and 101.2(6)%). The structure is briefly discussed, emphasizing its relation to other structures with a high content of gallium or aluminum.     

Die Kristallstrukturen einer Serie von Verbindungen mit Kationen des Typs [R3PNH2]+, [R3PN(H)SiMe3]+ und [R3PN(SiMe3)2]+

Crystal Structures of a Series of Compounds with Cations of the Type [R₃PNH₂]⁺, [R₃PN(H)SiMe₃]⁺, and [R₃PN(SiMe₃)₂]⁺ The crystal structures of a series of compounds with cations of the type [R₃PNH₂]⁺, [R₃PN(H)SiMe₃]⁺, and [R₃PN(SiMe₃)₂]⁺, in which R represents various organic residues, are determined by means of X‐ray structure analyses at single crystals. The disilylated compounds [Me₃PN(SiMe₃)₂]⁺I^–, [Et₃PN(SiMe₃)₂]⁺I^–, and [Ph₃PN(SiMe₃)₂]⁺I₃^– are prepared from the corresponding silylated phosphaneimines R₃PNSiMe₃ with Me₃SiI. [Me₃PNH₂]Cl (1): Space group P2₁/n, Z = 4, lattice dimensions at –71 °C: a = 686.6(1), b = 938.8(1), c = 1124.3(1) pm; β = 103.31(1)°; R = 0.0239. [Et₃PNH₂]Cl (2): Space group Pbca, Z = 8, lattice dimensions at –50 °C: a = 1272.0(2), b = 1147.2(2), c = 1302.0(3) pm; R = 0.0419. [Et₃PNH₂]I (3): Space group P2₁2₁2₁, Z = 4, lattice dimensions at –50 °C: a = 712.1(1), b = 1233.3(2), c = 1257.1(2) pm; R = 0.0576. [Et₃PNH₂]₂[B₁₀H₁₀] (4): Space group P2₁/n, Z = 4, lattice dimensions at –50 °C: a = 809.3(1), b = 1703.6(1), c = 1800.1(1) pm; β = 96.34(1)°; R = 0.0533. [Ph₃PNH₂]ICl₂ (5): Space group P1, Z = 2, lattice dimensions at –60 °C: a = 825.3(3), b = 1086.4(3), c = 1241.2(4) pm; α = 114.12(2)°, β = 104.50(2)°, γ = 93.21(2)°; R = 0.0644. In the compounds 1–5 the cations are connected with their anions via hydrogen bonds of the NH₂ groups with 1–3 forming zigzag chains. [Me₃PN(H)SiMe₃][O₃S–CF₃] (6): Space group P2₁/c, Z = 8, lattice dimensions at –83 °C: a = 1777.1(1), b = 1173.6(1), c = 1611.4(1) pm; β = 115.389(6)°; R = 0.0332. [Et₃PN(H)SiMe₃]I (7): Space group P2₁/n, Z = 4, lattice dimensions at –70 °C: a = 1360.2(1), b = 874.2(1), c = 1462.1(1) pm; β = 115.19(1)°; R = 0.066. In 6 and 7 the cations form ion pairs with their anions via NH … X hydrogen bonds. [Me₃PN(SiMe₃)₂]I (8): Space group P2₁/c, Z = 8, lattice dimensions at –60 °C: a = 1925.4(9), b = 1269.1(1), c = 1507.3(4); β = 111.79(3)°; R = 0.0581. [Et₃PN(SiMe₃)₂]I (9): Space group Pbcn, Z = 8, lattice dimensions at –50 °C: a = 2554.0(2), b = 1322.3(1), c = 1165.3(2) pm; R = 0.037. [Ph₃PN(SiMe₃)₂]I₃ (10): Space group P2₁, Z = 2, lattice dimensions at –50 °C: a = 947.7(1), b = 1047.6(1), c = 1601.6(4) pm; β = 105.96(1)°; R = 0.0334. 8 to 10 are built up from separated ions.     

Die Insertion von Sauerstoffatomen in Ga–Ga- und In–In-Bindungen – Bildung von monomeren Verbindungen R2E–O–ER2 [R = CH(SiMe3)2] mit stark aufgeweiteten E–O–E-Winkeln

The Insertion of Oxygen Atoms into Ga–Ga and In–In Bonds – Formation of the Monomeric Compounds R₂E–O–ER₂ [R = CH(SiMe₃)₂] with Strongly Enlarged Angles E–O–E The tetraalkyldielement compounds R₂Ga–GaR₂ ( 1 ) und R₂In–InR₂ ( 2 ) [R = CH(SiMe₃)₂] reacted with trimethylamine N-oxide by the insertion of oxygen atoms in their element-element single bonds. The products R₂E–O–ER₂ are monomeric in the solid state due to the high steric shielding by the voluminous bis(trimethylsilyl)methyl groups. As shown by crystal structure determinations, the E–O–E bridges have large angles of 142.7 (E = Ga, 3 ) and 138.6° (E = In, 4 ) and short separations between the oxygen and the coordinatively unsaturated Ga and In atoms. Both products are extremely hygroscopic.     

Yb6Ir5Ga7 – A MgZn2 Superstructure

The gallide Yb₆Ir₅Ga₇ was synthesized by high‐frequency melting of the elements in a sealed niobium ampoule. The structure was refined from single‐crystal X‐ray diffractometer data: Nb_6.4Ir₄Al_7.6 type, P6₃/mcm, a = 930.4(1), c = 843.0(1) pm, wR₂ = 0.0597, 379 F² values and 22 variables. Yb₆Ir₅Ga₇ adopts a superstructure of the MgZn₂ Laves phase by a complete ordering of the iridium and gallium atoms on the zinc substructure, i.e. the network consists of ordered and condensed Ir₃Ga and IrGa₃ tetrahedra with Ir–Ga distances ranging from 260 to 265 pm. The crystal chemical details and the underlying group‐subgroup scheme are discussed.     

Ca3Au6.61Ga4.39 – A New Gallide with a Three‐Dimensional Gold–Gallium Network

Ca₃Au_6.61Ga_4.39 was synthesized by reacting the elements in a glassy carbon crucible under argon in a water‐cooled sample chamber in a high‐frequency furnace. The compound crystallizes with a new hexagonal structure type, space group P6₃/mmc: Z = 2, a = 926.6(2), c = 733.1(2) pm, wR2 = 0.0832, 328 F values and 20 variables. This structure type consists of a remarkably complex three‐dimensional [Au_6.61Ga_4.39] network with significant Au–Au, Au–Ga, and Ga–Ga interactions. The calcium atoms are located within slightly distorted hexagonal channels of the gold–gallium network. The structural relations to the AlB₂ and Er₂RhSi₃ type structures are discussed.     

ZrIV‐ und TaV‐Komplexe mit methanoverbrückten Bis(aryloxy)‐Liganden

Zr^IV and Ta^V Complexes with Methano‐Bridged Bis(aryloxy) Ligands The bis(aryloxy) ligand precursor compounds bis(2‐trimethylsiloxy‐5‐tbutylphenyl)methane (L–SiMe₃) and its bromoderivative (2‐trimethylsiloxy‐3‐bromo‐5‐tbutylphenyl)(2′‐trimethylsiloxy‐5′‐tbutylphenyl)methane (L^Br–SiMe₃) are prepared in analogy to the corresponding calixarenes in excellent yields. X‐ray structure analysis for L^Br–SiMe₃: space group P2₁/c, a = 12.462(7), b = 10.466(6), c = 23.315(14) Å, β = 105.02(4)°, V = 2937(3) ų, Z = 4. L–SiMe₃ and L^Br–SiMe₃ react with Zr^IV and Ta^V chlorides in very good yields forming di‐ and trinuclear complexes. From the reaction of CpZrCl₃ with L^Br–SiMe₃ in the ratio of 3 : 2 a Zr₃ complex ( 7 ) is obtained, with one L^Br ligand only, which Zr atoms are bridged by a μ₃‐oxygen. The X‐ray structure analysis of 7 (space group R 3, a = 33.23(6), c = 24.47(8) Å, V = 23405(128) ų, Z = 18) additionally reveals that one phenolato oxygen atom of the L^Br ligand is terminally bound to a distorted tetragonal‐pyramidal coordinated Zr atom, while the second phenolato oxygen atom of the L^Br ligand forms a bridge to another Zr atom with a distorted octahedral coordination. The third Zr atom is also found in a distorted octahedral coordination mode. The reactions of L–SiMe₃ and L^Br–SiMe₃ with CpTaCl₄ and TaCl₅ yield dinuclear Ta complexes with a bridging bis(aryloxy) ligand. NMR spectroscopic data point out that the coordination of the bis(aryloxy) ligands in the Ta complexes very much resembles that in the Zr₃‐complex with one terminal and one bridging phenolato oxygen atom. The Zr₃ and the Ta complexes L^BrTa₂Cp₂Cl₆ and LTa₂Cl₈ were tested with respect to their catalytic properties in olefin polymerisation reactions in the presence of MAO.     

Der erste molekulare quadratisch‐antiprismatische Ga8‐Cluster mit closo‐Struktur

The First Molecular Square Antiprismatic Ga₈ Cluster exhibiting a closo Structure Ga₈(C₁₃H₉)₈^2– has been synthesized as a lithium salt from a reaction of fluorenyllithium with a metastable Ga^IBr solution. It is characterized by X‐ray structure analysis and DFT calculations. The eight Ga atoms form a square antiprismatic core and each Ga atom is σ‐bonded to a fluorenyl ligand. The Ga₈ entity of the cluster is described as a closo compound in contrast to the earlier presented species Ga₁₂(C₁₃H₉)₁₀^2–. This interpretation is based on DFT calculations for Ga₈H₈^2– and B₈H₈^2–.     

Dispersion‐Force‐Assisted Disproportionation: A Stable Two‐Coordinate Copper(II) Complex

The synthesis of the first linear coordinated Cu^II complex Cu{N(SiMe₃)Dipp}₂ ( 1 Dipp=C₆H₅‐2,6Prⁱ₂) and its Cu^I counterpart [Cu{N(SiMe₃)Dipp}₂]^? ( 2 ) is described. The formation of 1 proceeds through a dispersion force‐driven disproportionation, and is the reaction product of a Cu^I halide and LiN(SiMe₃)Dipp in a non‐donor solvent. The synthesis of 2 is accomplished by preventing the disproportionation into 1 by using the complexing agent 15‐crown‐5. EPR spectroscopy of 1 provides the first detailed study of a two‐coordinate transition‐metal complex indicating strong covalency in the Cu?N bonds.