Abstract:In order to construct bimetallic organometallic donor-acceptor complexes with nonlinear optical (NLO) properties, the bimetallic sesquifulvalene com-

The heterobimetallic cationic NLO chromophore (1-ferrocenyl-η6-borabenzene)(η5-cyclopentadienyl)cobalt(1+) ([{1-((η5-C5H5)Fe(η5-C5H4))-η6-BC5H5}Co(η5-C5H5)]+, 1 +) has been synthesized by reaction of FcBBr2 and cobaltocene and subsequent oxidation with FeCl3. The neutral bimetallic compound 1 is paramagnetic and exhibits an ESR spectrum similar to that of the mononuclear 19-valence-electron complex Co(1-Ph-η6-borabenzene)2. Complex 1-PF6 crystallizes in monoclinic space group P21/c with a = 10.541(3) Å, b = 17.647(5) Å, c = 10.965(3) Å, β = 96.38(2)°, Z = 4, and V = 2027.0(10) Å3. NMR data for the oxidized diamagnetic cation 1 + indicate that the positive charge is predominantly localized on the (borabenzene)cobalt moiety. The X-ray structure determination of 1-PF6 shows the two sandwich units in mutually trans positions. The structural data denote an increased electronic interaction between the donating ferrocenyl group and the borabenzene unit. A cyclic voltammetric study of 1-PF6 or 1 reveals three reversible redox couples (−1/0, 0/+1, +1/+2), resembling those of the mononuclear parent compounds, although the redox potentials are slightly shifted due to the mutual influence of the electron-donating and -accepting properties of the different sandwich units. The UV−vis spectrum of 1 + confirms the enhanced donor−acceptor interaction by a strong, negative solvatochromic absorption about λ = 600 nm which is assigned to a charge-transfer transition. The determination of the first hyperpolarizability β by means of hyper Rayleigh scattering yields (90 ± 30) × 10-30 esu, which is unexpectedly high in the face of the directly coupled donor−acceptor pair.

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Professor Karl-Heinz Thiele zum 70. Geburtstag gewidmet Inhaltsu È bersicht. Die Bis(aryloxy)-Ligand-Vorla Èuferverbin-dung Bis(2-trimethylsiloxy-5-tbutylphenyl)methan (L±SiMe 3 ) und ihr Bromoderivat (2-Trimethylsiloxy-3-bromo-5-tbutylphenyl)(2'-trimethylsiloxy-5'-tbutylphenyl)methan (L Br ±SiMe 3 ) werden in Analogie zur Synthese entsprechender Calixarene in ausgezeichneten Ausbeuten hergestellt. Kristallstrukturanalyse von L Br ±SiMe 3 : Raumgruppe P2 1 /c, a = 12.462(7), b = 10.466(6), c = 23.315(14) A Ê , b = 105.02(4)°, V = 2937(3) A Ê 3 , Z = 4. L±SiMe 3 und L Br ±SiMe 3 reagieren in sehr guten Ausbeuten mit Zr IV -und Ta V -Chloriden unter Bildung zwei-und dreikerniger Komplexe. Aus der Reaktion von CpZrCl 3 mit L Br ±SiMe 3 im Verha Èltnis 3 : 2 wird ein Zr 3 -Komplex (7) mit nur einen L Br -Liganden isoliert, dessen Zr-Atome von l 3 -Sauerstoff u È berbru È ckt werden. Die Kristallstrukturanalyse von 7 (Raumgruppe R 3, a = 33.23(6), c = 24.47(8) A Ê , V = 23405(128) A Ê 3 , Z = 18) ergibt auûerdem, dass der Ligand L Br u È ber ein Phenolatsauerstoffatom terminal an ein verzerrt tetragonal-pyramidal koordiniertes Zr-Atom bindet, wa È hrend das zweite Sauerstoffatom des L Br -Liganden eine Bru È cke zum zweiten Zr-Atom mit einer verzerrt oktaedrischen Koordination bildet. Das dritte Zr-Atom ist ebenfalls verzerrt oktaedrisch koordiniert. Die Reaktionen von L±SiMe 3 und L Br ±SiMe 3 mit CpTaCl 4 und TaCl 5 ergeben Ta-Zweikernkomplexe mit einem verbru È ckenden Bis(aryloxy)-Liganden. NMR-spektroskopische Befunde deuten darauf hin, dass die Koordination des Bis(aryloxy)-Liganden in den Ta-Komplexen a È hnlich der im Zr 3 -Komplex u È ber ein terminales und ein verbru È ckendes Phenolatsauerstoffatom erfolgt. Der Zr 3 -Komplex sowie die Ta-Komplexe L Br Ta 2 Cp 2 Cl 6 und LTa 2 Cl 8 wurden auf katalytische Eigenschaften fu È r die Olefinpolymerisation in Gegenwart von MAO getestet. Zr IV and Ta V Complexes with Methano-Bridged Bis(aryloxy) LigandsAbstract. The bis(aryloxy) ligand precursor compounds bis(2-trimethylsiloxy-5-tbutylphenyl)methane (L±SiMe 3 ) and its bromoderivative (2-trimethylsiloxy-3-bromo-5-tbutylphenyl)(2'-trimethylsiloxy-5'-tbutylphenyl)methane (L Br ±SiMe 3 ) are prepared in analogy to the corresponding calixarenes in excellent yields. X-ray structure analysis for L Br ±SiMe 3 : space group P2 1 /c, a = 12.462(7), b = 10.466(6), c = 23.315(14) A Ê , b = 105.02(4)°, V = 2937(3) A Ê 3 , Z = 4. L±SiMe 3 and L Br ±SiMe 3 react with Zr IV and Ta V chlorides in very good yields forming di-and trinuclear complexes. From the reaction of CpZrCl 3 with L Br ±SiMe 3 in the ratio of 3 : 2 a Zr 3 complex (7) is obtained, with one L Br ligand only, which Zr atoms are bridged by a l 3 -oxygen. The X-ray structure analysis of 7 (space group R 3, a = 33.23(6), c = 24.47(8) A Ê , V = 23405(128) A Ê 3 , 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 l...