Klaus Eichele Publication Abstracts 2012

 

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[UP]	V. Gierz, A. Seyboldt, C. Maichle-Moessmer, K. W. Toernroos, M. T. Speidel, B. Speiser, K. Eichele, D. Kunz: Dinuclear coinage-metal complexes of bis(NHC) ligands: structural features and dynamic behavior of a Cu-Cu Complex Organometallics 2012, 31(22), 7893-7901. DOI 10.1021/om300544g

Binuclear complexes of copper, silver, and gold bearing a 2,2?-bipyridine analogue, the pyridazine annelated bis(N-heterocyclic carbene) ligand (vegi) 1, were prepared and structurally characterized. They all feature the shortest metal–metal distances that have been measured so far in complexes with this structural motif bearing neutral bidentate ligands, indicative of d¹⁰–d¹⁰ interactions. While in the silver complex the linear coordination of each silver atom with two carbene ligands results in a planar complex, the ligand planes are twisted by 70° in the Cu complex 4 and by 31° in the gold complex 3. The copper complex shows a solvent-dependent equilibrium between the [Cu₂L₂]²⁺ complex and a [Cu₂L₃]²⁺ complex along with solvated CuPF₆.

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[UP]	S. Biswas, M. Mueller, C. Toenshoff, K. Eichele, C. Maichle-Moessmer, A. Ruff, B. Speiser, H. F. Bettinger: The Overcrowded Borazine Derivative of Hexabenzotriphenylene Obtained through Dehydrohalogenation Eur. J. Org. Chem. 2012(24), 4634-4639. DOI 10.1002/ejoc.201200322

Treatment of 9-chloro-9-bora-10-azaphenanthrene with potassium hexamethyldisilazide yields the borazine derivative of hexabenzotriphenylene (4). This compound, the formal trimer of 9,10-azaboraphenanthryne (6), is soluble in organic solvents and was fully characterized. The tetramer of 6 is formed as a byproduct in the previously described high-temperature synthesis of 4.

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[UP]	J. Henning, H. Schubert, K. Eichele, F. Winter, R. Poettgen, H. A. Mayer, L. Wesemann: Synthesis and Characterization of N-[2-P(i-Pr)2-4-methylphenyl]2- (PNP) Pincer Tin(IV) and Tin(II) Complexes Inorg. Chem. 2012, 51(10), 5787-5794. DOI 10.1021/ic300324s

N-[2-P(i-Pr)₂-4-methylphenyl]₂^– (PNP) pincer complexes of tin(IV) and tin(II), [(PNP)SnCl₃] (2) and [(PNP)SnN(SiMe₃)₂] (3), respectively, were prepared and characterized by X-ray diffraction, solution and solid state NMR spectroscopy, and ¹¹⁹Sn Mössbauer spectroscopy. Furthermore, ¹¹⁹Sn cross polarization magic angle spinning NMR spectroscopic data of [Sn(NMe₂)₂]₂ are reported. Compound 2 is surprisingly stable toward air, but attempts to substitute chloride ligands caused decomposition.

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[UP]	C. Toenshoff, M. Mueller, T. Kar, F. Latteyer, T. Chassé, K. Eichele, H. F. Bettinger: B3N3 Borazine Substitution in Hexa-peri-Hexabenzocoronene: Computational Analysis and Scholl Reaction of Hexaphenylborazine ChemPhysChem 2012, 13(5), 1173-1181. DOI 10.1002/cphc.201101025

The doping of graphene molecules by borazine (B₃N₃) units may modify the electronic properties favorably. Therefore, the influence of the substitution of the central benzene ring of hexa-peri-hexabenzocoronene (HBC, C₄₂H₁₈) by an isoelectronic B₃N₃ ring resulting in C₃₆B₃N₃H₁₈ (B3N3HBC) is investigated by computational methods. For comparison, the isoelectronic and isosteric all-B/N molecule B₂₁N₂₁H₁₈ (termed BN) and its carbon derivative C₆B₁₈N₁₈H₁₈ (C6BN), obtained by substitution of a central B₃N₃ by a C₆ ring, are also studied. The substitution of C₆ in the HBC molecule by a B₃N₃ unit results in a significant change of the computed IR vibrational spectrum between 1400 and 1600 cm^-1 due to the polarity of the borazine core. The properties of the BN molecule resemble those of hexagonal boron nitride, and substitution of the central B₃N₃ ring by C₆ changes the computed IR vibrational spectrum only slightly. The allowed transitions to excited states associated with large oscillator strengths shift to higher energy upon going from HBC to B3N3HBC, but to lower energy upon going from BN to C6BN. The possibility of synthesis of B3N3HBC from hexaphenylborazine (HPB) using the Scholl reaction (CuCl₂/AlCl₃ in CS₂) is investigated. Rather than the desired B3N3HBC an insoluble and X-ray amorphous polymer P is obtained. Its analysis by IR and ¹¹B magic angle spinning NMR spectroscopy reveals the presence of borazine units. The changes in the ¹¹B quadrupolar coupling constant C_Q, asymmetry parameter ?, and isotropic chemical shift ?_iso(¹¹B) with respect to HPB are in agreement with a structural model that includes B3N3HBC-derived monomeric units in polymer P. This indicates that both intra- and intermolecular cyclodehydrogenation reactions take place during the Scholl reaction of HPB.

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[UP]	J.-A. Dimmer, M. Hornung, K. Eichele, L. Wesemann: Selenium adducts of germa- and stanna-closo-dodecaborate: coordination at platinum, structural studies and NMR spectroscopy Dalton Trans. 2012, 41(29), 8989-8996. DOI 10.1039/C2DT30478C

The selenium adducts of germa- and stanna-closo-dodecaborate can coordinate at platinum via the selenium atom and result in the products [Pt(dppp)(Se–TB₁₁H₁₁)₂]^2- (T = Ge, Sn) (dppp = 1,3-bis(diphenylphosphino)propane). The monomeric tin compound [Pt(dppp)(Se–SnB₁₁H₁₁)₂]^2- is converted to a dimeric complex [Pt₂(dppp)₂(?₂,??₂-?²-Se₂SnB₁₁H₁₁)]. The new compounds were characterized by NMR spectroscopy in solution (¹H, ¹¹B, ¹³C, ³¹P, ⁷⁷Se, ¹¹⁹Sn, ¹⁹⁵Pt), elemental analysis and single crystal X-ray diffraction.

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[UP]	C. Nickl, K. Eichele, L. Wesemann: 1,2-Distanna-closo-dodecaborate—a rare example of a 1,2-distannylene ligand in transition metal chemistry Dalton Trans. 2012, 41, 243-250. DOI 10.1039/C1DT11247C

The coordination chemistry of the novel bidentate tin ligand 1,2-distanna-closo-dodecaborate is illustrated for the first time by reactions with molybdenum, platinum and gold metal complexes. Up to three clusters coordinate two metal centers in close proximity. For all these metal complexes the typical mu-bridging coordination mode was observed exclusively. Furthermore, two cluster anions react with dichloromethane via substitution of the chloride ions. The carbon functionalized tin cluster [Et4N]2[CH2(Sn2B10H10)2] and the coordination complexes [Et3NMe]6[Mo2(CO)6(Sn2B10H10)3], [Et3NMe]2[{HPt(PEt3)2(Sn2B10H10)}2], [Et4N]2[{HPt(PPh3)2(Sn2B10H10)}2] and [{(TP)Au}2(Sn2B10H10)] (TP = PhP(o-Ph2PC6H4)2) are fully characterized by multinuclear NMR spectroscopy, elemental analyses and crystal structure analyses.