Klaus Eichele Publication Abstracts 2002

 

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[UP]	H. A. Y. Mohammad, J. C. Grimm, K. Eichele, H.-G. Mack, B. Speiser, F. Novak, M. G. Quintanilla, W. C. Kaska, H. A. Mayer: C-H Oxidative Addition with a (PCP)Ir(III)-Pincer Complex Organometallics 2002, 21, 5775-5784. DOI 10.1021/om020621w

Treatment of 4-MeO-C₆H₃-2,6-(CH₂Pt-Bu₂)₂ with IrCl₃*nH₂O in i-PrOH/H₂O gives a cyclometalated pincer chlorohydrido iridium complex. A second intramolecular oxidative addition reaction of one of the tert-butyl C-H bonds to the Ir(III) center followed by the reductive elimination of H₂ gives a novel doubly metalated compound that is stable to air and water. X-ray crystallographic analysis revealed a chelated square-pyramidal iridium compound with two cyclometalated five-membered rings in the basal plane and the iridium bound methylene group of the four-membered ring in the apical position. The free coordination site is protected by an agostic C-H bond. While a phosphorus-phosphorus coupling constant of 351.1 Hz establishes the trans position of the phosphorus groups there is no indication of a hydridic or weakly bound hydrogen. Electrochemical studies establish an equilibrium between the pincer chlorohydrido compound and the doubly metalated complex and H₂. A square scheme can be used to describe the relationship between the redox couples and solution equilibria. The unusual stability of the doubly metalated complex was supported by DFT calculations at different levels of theory on model compounds. They show the coordination of two hydrogen atoms best described as η²-coordinated dihydrogen and suggest an Ir(V) oxidation state as intermediate.

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E. Lindner, R. F. Zong, K. Eichele, M. Ströbele: Preparation, properties, and reactions of metal-containing heterocycles Part CVIII. A novel generation of rigid, nanoscaled 1,1'-ferrocenediyl-bridged bis(pyridine), bis(bipyridine), and bis(phenanthroline) ligands J. Organomet. Chem. 2002, 660, 78-84. DOI 10.1016/S0022-328X(02)01774-6

Four novel, rigid, and conjugated 1,1'-ferrocenediyl-bridged, bis(pyridine), bis(bipyridine), and bis(phenanthroline) ligands 2 and 5-7 have been synthesized by palladium promoted C-C coupling reactions and characterized by H-1-, C-13{H-1}-NMR, FT-IR, and mass spectroscopy as well as by elemental analyses. Ligand 2 was prepared from 5-ethynyl-2,2'-bipyridine and 1,1'-diiodoferrocene, while compounds 5-7 were readily accessible by reactions between pre-constructed ferrocene 4 and 4-bromopyridine, 5-bromo-2,2'-bipyridine, and 3-bromo-1,10-phenanthroline, respectively. Treatment of 1,1'-diiodoferrocene with 1-ethynyl-4-triisopropylsilyl ethynyl-2,5-dipropoxybenzene resulted in the formation of the ferrocene derivative 3. Via a Si-C bond cleavage in 3 in the presence of tetra-n-butylammonium fluoride in THF the intermediate 4 was obtained. Ligand 1*0.5H₂O crystallizes in the triclinic space group P-1 with a = 11.2711(10), b = 13.3346(12), c = 14.0879(14) Angstrom, alpha = 105.007(12), beta = 105.179(11), gamma = 105.218(10)degrees, V = 1845.7 Angstrom³, Z = 2, R = 0.0640, and wR(2) = 0. 1292.

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[UP]	E. Lindner, C. S. Ayasse, K. Eichele, M. Steimann: Macrocyclic Di- and Tetranuclear Osmacycloferrocenophanes. Organometallics 2002, 21, 4217-4225 DOI 10.1021/om020310l

The novel dinuclear and tetranuclear ortho-, meta-, and para-osmacycloferrocenophanes [η⁵-C₅H₄(CH₂)_n-1,m- C₆H₄(CH₂)_nOs(CO)₄(CH₂)_n-1,m- C₆H₄(CH₂)_nC₅H₄-η⁵]_xFe_x (n = 2-4, m = 2-4; x = 1: 3a-h; x = 2: 4a-h) have been made available by the reaction of the corresponding bis(triflates) [η⁵-C₅H₄(CH₂)_n-1,m- C₆H₄(CH₂)_nOTf]₂Fe (2a-h) with Na₂[Os(CO)₄] in refluxing dimethyl ether. The macrocycles of 3b,c,e and 4a,h were investigated by X-ray structural analyses and consist of an extended hydrocarbon skeleton containing additionally two and four transition metal centers, respectively. In the case of the dinuclear osmacycloferrocenophanes 3a-h the redox behavior was examined by means of cyclic voltammetry, and the results were compared with those of the bis(alcohols) 1a-h, which were used as starting compounds for the bis(triflates) 2a-h. With increasing chain length the ferrocene unit is easier oxidized, and in the case of 3f-h the E1/2 values are in the region of diethylferrocene.

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[UP]	N. Kuhn, K. Eichele, M. Walker, Th. Berends, R. Minkwitz: Neuartige elementorganische Sauerstoffsäuren des Phosphors und Schwefels [1] Z. Anorg. Allg. Chem. 2002, 628, 2026-2032 DOI 10.1002/1521-3749(200209)628:9/10<2026::AID-ZAAC2026>3.0.CO;2-0

The novel imidazoliophosphonate acid Im-PO3H (7, Im = 2-{1,3-diisopropyl-4,5-dimethylimidazolio}) is prepared through hydrolysis of the phosphonyl chloride [Im-P(O)Cl₂]Cl (6) formed by the direct reaction of the stable 2,3-dihydro-1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (5) with P(O)Cl₃. The novel cationic sulfonic acid [Im-SO3H]X (11) is formed as its BF₄ (11a) and SbF₆ (11b) salt on treatment of the betaine Im-SO3 (10) with HBF₄ x Et₂O or HF/SbF₅. The crystal structures of 7 and 11b are reported and discussed.

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K. Eichele, R. E. Wasylishen, J. F. Corrigan, N. J. Taylor, A. J. Carty, K. W. Feindel, G. M. Bernard: Phosphorus Chemical Shift Tensors of Phosphido Ligands in Ruthenium Carbonyl Compounds: 31P NMR Spectroscopy of Single-Crystal and Powder Samples and ab initio Calculations. J. Am. Chem. Soc. 2002, 124, 1541-1552. DOI 10.1021/ja0122041

The phosphorus chemical shift (CS) tensors of several ruthenium carbonyl compounds containing a phosphido ligand, μ-PR₂, bridging a Ru-Ru bond were characterized by solid-state ³¹P NMR spectroscopy. As well, an analogous osmium compound was examined. The structures of most of the clusters investigated have approximate local C_2v symmetry about the phosphorus atom. Compared to the "isolated" PH2^- anion, the phosphorus nucleus of a bridging phosphido ligand exhibits considerable deshielding. The phosphorus CS tensors of most of the compounds have spans ranging from 230 to 350 ppm and skews of approximately zero. Single-crystal NMR was used to investigate the orientation of the phosphorus CS tensors for two of the compounds, Ru₂(CO)₆(μ₂-η²-C=C-Ph) (μ₂-PPh₂) and Ru₃(CO)₉(μ₂-H) (μ₂-PPh₂). The intermediate component of the phosphorus CS tensor, δ₂₂, lies along the local C₂ axis in both compounds. The least shielded component, δ₁₁, lies perpendicular to the Ru-P-Ru plane while the most shielded component, δ₃₃, lies perpendicular to the C-P-C plane. The orientation of the phosphorus CS tensor for a third compound, Ru₂(CO)₆(μ²-PPh₂)₂, was investigated by the dipolar-chemical shift NMR technique and was found to be analogous, suggesting it to be the same in all compounds. Ab initio calculations of phosphorus magnetic shielding tensors have been carried out and reproduce the orientations found experimentally. The orientation of the CS tensor has been rationalized using simple frontier MO theory. Splittings due to ^99,101Ru-³¹P spin-spin coupling have been observed for several of the complexes. A rare example of ¹⁸⁹Os-³¹P spin-spin splittings is observed in the ³¹P MAS NMR spectrum of the osmium cluster, where ¹J(¹⁸⁹Os, ³¹P) is 367 Hz. For this complex, the ¹⁸⁹Os nuclear quadrupolar coupling constant is on the order of several hundred megahertz.

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[UP]	C. Nachtigal, S. Al-Gharabli, K. Eichele, E. Lindner, H. A. Mayer: Structural Studies of an Array of Mixed Diamine Phosphine Ruthenium(II) Complexes Organometallics 2002, 21, 105-112. DOI 10.1021/om0105831

Treatment of RuCl₂(h²-Ph²PCH₂CH₂OCH₃)₂ with various chelating diamines permitted the isolation of the corresponding RuCl₂(h¹-Ph₂PCH₂CH₂OCH₃)₂(diamine) complexes in high yield (diamine = 1,2-diaminoethane, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-phenylenediamine, 1,8-diaminonaphthalene, 2,2'-bipyridine, 1,10-phenanthroline). In solution, all complexes prefer the trans-chloro cis-phosphine arrangement, as deduced by NMR spectroscopy. X-ray studies showed that in the solid state all three possible isomers of the octahedral RuCl₂P₂(diamine) complexes are present. The reaction of the RuCl₂(h¹-Ph₂PCH₂CH₂OCH₃)₂(diamine) complexes with 1 equiv of AgSbF₆, AgBF₄, or TlPF₆ leads to the abstraction of one chloride by simultaneously coordinating one ether oxygen to ruthenium and forming monocationic [RuCl(h¹-Ph₂PCH₂CH₂OCH₃)(h²- Ph₂PCH₂CH₂OCH₃)(diamine)]+ compounds. If a large excess of silver or thallium salt is used, the dichloro complexes are converted to the [Ru(h²-Ph₂PCH₂CH₂OCH₃)₂(diamine)]2+ dications. In the case of 1,2-phenylendiamine as coligand, the corresponding dication is only observed in traces. NMR spectroscopic investigations and X-ray structural analyses confirm the h¹ and h² coordination of the ether-phosphine ligands in the corresponding mono- and dicationic ruthenium(II) complexes.