Klaus Eichele Publication Abstracts 2003

 

---

[UP]	A. M. Winter, K. Eichele, H.-G. Mack, S. Potuznik, H. A. Mayer, W. C. Kaska: Rhodium pincer complexes of 2,2'-bis(diphenylphosphino)diphenylamine J. Organomet. Chem. 2003, 682, 149-154. DOI 10.1016/S0022-328X(03)00776-9

The novel pincer ligand 2,2'-bis(diphenylphosphino)diphenylamine (1) has been synthesized by treatment of 2,2'-dibromodiphenylamine with n-butyl lithium and subsequent reaction with diphenylchlorophosphine. When ligand 1 is treated with RhCl₃ hydrate the dinuclear complex 1a forms which can be converted into the square planar carbonyl complex 1c upon reduction with Na/Hg in the presence of CO. Depending on the reaction conditions two different complexes were isolated when 1 reacts with [(COE)₂RhCl]₂. In THF the hydrochloro complex 1b and with n-butyl lithium the COE complex 1d is generated. Interestingly, the formation of 1b represents a rare case of N–H oxidative addition to a late transition metal complex fragment. Compound 1c is observed upon reaction of the COE complex 1d with carbon monoxide. Quantum chemical calculations at different levels of theory are in good agreement with the experimental structure of 1c.

---

[UP]	E. Lindner, M. Henes, W. Wielandt, K. Eichele, M. Steimann, G. A. Luinstra, H.-H. Görtz: Transition metal-catalyzed polymerization of 1,3,5-trioxane J. Organomet. Chem. 2003, 681, 12-23 DOI 10.1016/S0022-328X(03)00527-8

The molybdenum complexes [(eta⁵-C₅Me₅)Mo(CO)₃OTf] (1a), [(eta⁵-C₅H₅)Mo(CO)₃X] (2a –2c) (X=F₃CSO₃ (a), F₃CCO₂ (b), BF₄ (c)), and [(eta⁵-C₅H₄CO₂CH₃)Mo(CO)₃OTf] (3a) catalyze the cationic ring-opening polymerization (ROP) of 1,3,5-trioxane to polyoxymethylene (POM, 5). Hitherto unknown 3a is accessible by treatment of [(eta⁵-C₅H₄CO₂CH₃)Mo(CO)₃CH₃] with CF₃SO₃H. The precipitation time of the polymerization, which is defined in the following as the time until precipitation starts, is dependent on the Lewis acidity of the transition metal center and the presence of formaldehyde or water. ¹³C-labeled formaldehyde was copolymerized with 1,3,5-trioxane and randomly incorporated into POM. This observation supports the conception that formaldehyde is reversibly formed during the polymerization. Catalyst 2a was successfully applied in the ROP of trioxane even in the presence of up to 3.6 mol% of water. Time-dependent ¹H-NMR spectroscopic investigations of the trioxane polymerization revealed the formation of methoxymethyl formate (4) as a by-product, an isomer of trioxane. In the presence of 2a as a catalyst, 4 was degraded to methyl formate (6) and POM (5) in a ratio of about 2:1. This degradation was monitored by ¹H-NMR spectroscopy. Catalyst 2a is also able to copolymerize 1,3,5-trioxane with 1,3-dioxepane leading to a thermally stable copolymer after treatment with an aqueous solution of Na₂CO₃.

---

[UP]	D. L. Bryce, K. Eichele, R. E. Wasylishen: An 17O NMR and Quantum Chemical Study of Monoclinic and Orthorhombic Polymorphs of Triphenylphosphine Oxide. Inorg. Chem. 2003, 42, 5085-5096. DOI 10.1021/ic020706p

Solid-state ¹⁷O NMR spectroscopy is employed to characterize powdered samples of known monoclinic and orthorhombic modifications of ¹⁷O-enriched triphenylphosphine oxide, Ph₃PO. Precise data on the orientation-dependent ¹⁷O electric field gradient (EFG) and chemical shift (CS) tensors are obtained for both polymorphs. While the ¹⁷O nuclear quadrupolar coupling constants (C_Q) are essentially identical for the two polymorphs (C_Q = -4.59 ± 0.01 MHz (orthorhombic); C_Q = -4.57 ± 0.01 MHz (monoclinic)), the spans (Ω) of the CS tensors are distinctly different (Ω = 135 ± 3 ppm (orthorhombic); Ω = 155 ± 5 ppm (monoclinic)). The oxygen CS tensor is discussed in terms of Ramsey's theory and the electronic structure of the phosphorus-oxygen bond. The NMR results favor the hemipolar σ- bonded R₃P⁺-O^- end of the resonance structure continuum over the multiple bond representation. Indirect nuclear spin-spin (J) coupling between ³¹P and ¹⁷O is observed directly in ¹⁷O magic-angle-spinning (MAS) NMR spectra as well as in ³¹P MAS NMR spectra. Ab initio and density-functional theory calculations of the ¹⁷O EFG, CS, and ¹J(³¹P,¹⁷O) tensors have been performed with a variety of basis sets to complement the experimental data. This work describes an interesting spin system for which the CS, quadrupolar, J, and direct dipolar interactions all contribute significantly to the observed ¹⁷O NMR spectra and demonstrates the wealth of information which is available from NMR studies of solid materials.

---

[UP]	Z.-L. Lu, K. Eichele, I. Warad, H. A. Mayer, E. Lindner, Z.-j. Jang, V. Schurig: Supported Organometallic Complexes. XXXVIII. Bis(methoxyethyldimethylphosphine)ruthenium(II) Complexes as Transfer Hydrogenation Catalysts Z. Anorg. Allg. Chem. 2003, 629, 1308-1315. DOI 10.1002/zaac.200300067

Diamineruthenium(II) complexes containing the hemilabile methoxyethyldimethylphosphine ligand, [Cl₂Ru(L_n)-(h¹-Me₂PCH₂CH₂OMe)₂] (2L_n) (n = 1-12, Scheme 1), have been synthesized from the starting materials Me₂PCH₂CH₂OMe, [Ru(COD)Cl₂]_n, and the respective diamines L₁-L₁₂. The structure of complex 2L₅ reveals that two chlorides are in trans position, while in complex 2L₁₁ the two chlorides favor a cis configuration. Most of the complexes are highly catalytic active in the hydrogen transfer reduction of acetophenone. The experimental study indicates that the replacement of phenyl groups for methyl functions in the ether-phosphine ruthenium(II) complexes resulted in a switch of the hydrogenation mechanism from direct hydrogenation to transfer hydrogenation. The reason is attributed to the better donor ability of methyl groups compared to phenyl substitutents. Thus the metal center becomes more electron-rich and inhibits the binding of dihydrogen to the ruthenium(II) complex fragment.

---

[UP]

E. Lindner, I. Warad, K. Eichele, H. A. Mayer: Supported organometallic complexes Part 34: synthesis and structures of an array of diamine(ether-phosphine)ruthenium(II) complexes and their application in the catalytic hydrogenation of trans-4-phenyl-3-butene-2-one. Inorg. Chim. Acta 2003, 350, 49-56. DOI 10.1016/S0020-1693(02)01535-9

The novel diamine-bis(ether-phosphine)ruthenium(II) complexes Cl₂Ru(h¹- Ph₂PCH₂CH₂OCH₃)₂ (diamine)₂ (3L₁-3L₁₁) have been obtained by reaction of equimolar amounts of Cl₂Ru(P-O)₂ (2) with the respective diamines L₁-L₁₁ in good yields. X-ray structural investigations of 3L₂ and 3L₈ show monoclinic unit cells with the space group P2₁/c. The octahedrally coordinated ruthenium atoms have each two trans-chlorides and cis-phosphines which is in agreement with NMR studies in solution. With the exception of 3L₄ all mentioned ruthenium complexes are highly catalytically active in the hydrogenation of the α,β-unsaturated ketone trans-4-phenyl-3-butene-2-one. In most cases the conversions and selectivities toward the formation of the unsaturated alcohol trans-4-phenyl-3-butene-2-ol were 100% with high turnover frequencies under mild conditions.

---

[UP]

E. Lindner, R. Zong, M. Ströbele, K. Eichele: Preparation, properties, and reactions of metal-containing heterocycles. CX. 1. Crystal structure of 1,1'-bis{[4-(1,10-phenanthroline-3-yl-ethynyl)- 2,5-dipropoxy-phenyl]ethynyl}ferrocene. Z. Anorg. Allg. Chem. 2003, 629, 587-588. DOI 10.1002/zaac.200390097

The crystal structure of 1,1’-bis{[4-(1,10-phenanthroline-3- yl-ethynyl)-2,5-dipropoxy-phenyl]ethynyl}ferrocene (1)is reported. This compound crystallizes with two chloroform solvent molecules in the monoclinic space group P2₁/c (No. 14), a = 15.4253(11), b = 23.2003(10), c = 17.2630(13) A, β = 90.866(9)° and Z = 4. Both arms of the ferrocene moiety are parallel displaced with the four nitrogen atoms pointing to the same direction.

---

[UP]	Z.-L. Lu, K. Eichele, E. Lindner, H. A. Mayer: Supported organometallic complexes. Part 37: Synthesis and structures of diamine-bis(methoxyethyldimethylphosphine) ruthenium(II) complexes. Inorg. Chem. Commun. 2003, 6, 365 –369. DOI 10.1016/S1387-7003(02)00774-8

The first two examples of diamineruthenium(II)complexes containing the hemilabile methoxyethyldimethylphosphine ligand, Cl₂Ru(en)(η¹-Me₂PCH₂CH₂OMe)₂ (2a) and Cl₂Ru[(R,R)-dpen](η¹-Me₂PCH₂CH₂OMe)₂ (2b) (en = 1,2-diaminoethane, (R,R)-dpen = 1R,2R-1,2-diamino-1,2-diphenylethane) have been synthesized and structurally characterized.

---

[UP]	E. Lindner, H. A. Mayer, I. Warad, K. Eichele: Supported organometallic complexes. Part XXXV. Synthesis, characterization, and catalytic application of a new family of diamine(diphosphine)ruthenium(II) complexes J. Organomet. Chem. 2003, 665, 176-185. DOI 10.1016/S0022-328X(02)02112-5

The novel diamine(dppp)ruthenium(II) complexes 3L₁ - 3L₁₂ have been obtained by reaction of equimolar amounts of Cl₂Ru(dppp)₂ (2) with the diamines L₁ - L₁₂ in excellent yields. Within a few minutes one of the diphosphine ligands was quantitatively exchanged by the corresponding diamine. X-ray structural investigations of 3L₁, 3L₂, and 3L₈ show triclinic unit cells with the space groups P-1 (3L₁, 3L₂) and P1 (3L₈). Whereas in solution all these complexes prefer a trans-RuCl₂ configuration, in the solid state cis-(3L₁, 3L₂) and trans-isomers (3L₈) were observed. With the exception of 3L₅, 3L₆, and 3L₁₂ all mentioned ruthenium complexes are highly catalytically active in the hydrogenation of the α,β-unsaturated ketone trans-4-phenyl-3-butene-2-one. In most cases the conversions and selectivities toward the formation of the unsaturated alcohol trans-4-phenyl-3-butene-2-ol were > 99% with high turnover frequencies (TOFs) under mild conditions.

---

[UP]

E. Lindner, R. F. Zong, K. Eichele, U. Weisser, M. Ströbele: Preparation, properties, and reactions of metal-containing heterocycles, 109. Synthesis and structure of redox-active heterotetranuclear molecular polygons by self-assembly of two ferrocene-bridged bis(pyridines) with two transition metals Eur. J. Inorg. Chem. 2003, 705-712. DOI 10.1002/ejic.200390097

The macrocyclic complexes [(η⁵C₅H₄C₂-3-py)₂Fe]₂Ni₂(NO₃)₄ (2), [(η⁵-C₅H₄C₂-3-py)₂Fe]₂Ag(ClO₄)₂ (4), and [(η⁵C₅H₄C₂-3-py}₂Fe]₂Pd₂Cl₄ (5) were obtained by reaction of [Ni(H₂O)₆](NO₃)(₂), AgClO₄, and PdCl₂(COD) with the ligands (η⁵-C₅H₄C₂-4-py)₂Fe (1) and (η⁵-C₅H₄C₂-3-py)₂Fe (3), respectively, under high dilution conditions (Scheme 1). The molecular motifs of 2, 4, and 5 were studied by single-crystal X-ray structural investigations. Elemental analyses and H-1 NMR and IR spectra were also used to confirm the structures. Compound 2 represents an unsymmetric paddlewheel, in which the centers of the four Cp rings define a nearly ideal rectangle with dimensions of 20.2 x 3.3 Angstrom. In principle, macrocycles 4 and 5 can also be described as rectangles, however, due to the 3-positioned nitrogen donors with deformed edges (17.4 x 3.3 Angstrom for 4). In contrast to the offset packing of the molecules in 2, the macrocycles in the crystal of 4 are aligned, with trapped acetonitrile molecules in between. The intra- and intermolecular Ag-Ag distances are 3.50 and 3.79 A, respectively. Cyclovoltammetric studies reveal chemically reversible ferrocene-based redox reactions of 1-4. Although no electronic communication was observed between the two identical ferrocene units, a weak through-bond electronic interaction between ferrocene and nickel, or silver, was established. In 2 a weak antiferromagnetic interaction between the nickel atoms was also found.