Stefan H. Mühle

A Modular Approach to Structurally Diverse Bidentate Chelate Ligands for Transition Metal Catalysis

A modular approach to a new class of structurally diverse bidentate P/N, P/P, P/S, and P/Se chelate ligands has been developed. Starting from hydroquinone, various ligands were synthesized in a divergent manner via orthogonally bis-protected bromohydroquinones as the central building block. The first donor functionality (L1) is introduced to the aromatic (hydroquinone) ligand backbone either by Pd-catalyzed cross-coupling (Suzuki coupling) with hetero-aryl bromides, by Pd-catalyzed amination, or by lithiation and subsequent treatment with electrophiles (e.g., chlorophosphanes, disulfides, diselenides, or carbamoyl chlorides). After selective deprotection, the second ligand tooth (L2) is attached by reaction of the phenolic OH functionality with a chlorophosphane, a chlorophosphite, or a related reagent. Some of the resulting chelate ligands were converted into the respective PdX2 complexes (X = Cl, I), two of which were characterized by X-ray crystallography. The methodology developed opens an access to a broad variety of new chiral and achiral transition metal complexes and is generally suited for the solid-phase synthesis of combinatorial libraries, as will be reported separately.

Organometallic compounds of the lanthanides. CXXIII. Lanthanide bent-sandwich complexes with the bulky tetramethyl- iso -propylcyclopentadienyl ligand—synthesis, structures and catalytic activity for the hydrosilylation of alkenes/alkynes

Abstract The trichlorides of yttrium, samarium and lutetium react with two equivalents of Na[C5Me4 iPr] in THF to form [(η5-C5Me4 iPr)2LnCl(THF)] (Ln=Y (1), Sm (2), Lu (3)). Metathesis of 1–3 with LiCH3 in diethyl ether and LiCH(SiMe3)2 in toluene gives [(η5-C5Me4 iPr)2LnCH3(THF)] (Ln=Y (4), Lu (5)) and [(η5-C5Me4 iPr)2Ln{CH(SiMe3)2}] (Ln=Y (6), Sm (7)), respectively. The 1:2 reaction of LnI2(THF)x (Ln=Sm, Yb) with Na[C5Me4 iPr] in THF results in the formation of the divalent metallocenes [(η5-C5Me4 iPr)2Ln(THF)] (Ln=Sm (8), Yb (9)). The new compounds with the bulky tetramethyl-iso-propylcyclopentadienyl ligands were characterized by C, H analysis, mass spectrometry and NMR spectroscopy. Additionally, single crystal X-ray structure determination of the lutetium complexes 3 and 5 was performed. It has been shown that the alkyl complexes 4–7 are effective precatalysts for the hydrosilylation of alkenes and alkynes. The results of the described investigations are discussed.

THE SOLID-STATE STRUCTURE OF K3C60(THF)14

Abstract A solution reaction of C60 with an excess of potassium metal under sonication yields K3C60(THF)14 (1; THF = tetrahydrofuran). Compound 1 forms a polymeric linear chain built-up from one potassium ion bridging between two fulleride ions and thereby sitting above a CC bond between two pentagons, while the other two potassium ions cap the C60 molecule from top and bottom, thereby being located above six-membered rings. The coordination sphere of the potassium centres is completed by THF molecules. The crystal packing reveals a similarity with the face centred cubic lattice of the superconducting K3C60 phase. The solution EPR spectrum of 1 exhibits a sharp signal with g = 2.0007 at temperatures between 120 and 330 K.

Organometallic Compounds of the Lanthanides. 127 [1] Synthesis of Monomeric Bis(cyclopentadienyl)lanthanide Tetrahydroborates with Bulky Cyclopentadienyl Ligands. Single Crystal X-ray Structures of [(η5-C5Me5)2SmBH4(THF)] and [(η5-C5Me4Et)2Y(μ-H)2BH2(THF)]

The trichlorides of yttrium, samarium, and lutetium react with 2 equivalents of Na[C5H4 tBu] and 1 equivalent of NaBH4 to give [(η5-C5H4 tBu)2LnBH4(THF)] (Ln = Y (1), Sm (2), Lu (3)) or with 2 equivalents of Na[C5Me4R] and 1 equivalent of NaBH4 to form [(η5-C5Me4R)2 · LnBH4(THF)] (R = H, Ln = Y (4), Sm (5), Lu (6); R = Me, Ln = Y (7), Sm (8), Lu (9); R = Et, Ln = Y (10), Sm (11), Lu (12); R = iPr, Ln = Y (13), Sm (14), Lu (15)). The new compounds have been characterized by elemental analysis, NMR spectroscopy and mass spectrometry. The crystal structures of 8 and 10 were determined by single crystal X-ray diffraction. Organometall-Verbindungen der Lanthanoide. 127 Synthese von monomeren Bis(cyclopentadienyl)lanthanoid-tetrahydroboraten mit sperrigen Cyclopentadienyl-Liganden. Einkristallstrukturen von [(η5-C5Me5)2SmBH4(THF)] and [(η5-C5Me4Et)2Y(μ-H)2BH2(THF)] Die Trichloride von Yttrium, Samarium und Lutetium reagieren mit 2 Aquivalenten Na[C5H4 tBu] und 1 Aquivalent NaBH4 zu [(η5-C5H4 tBu)2LnBH4(THF)] (Ln = Y (1), Sm (2), Lu (3)) oder mit 2 Aquivalenten Na[C5Me4R] und 1 Aquivalent NaBH4 zu [(η5-C5Me4R)2 · LnBH4(THF)] (R = H, Ln = Y(4), Sm (5), Lu (6); R = Me, Ln = Y (7), Sm (8), Lu (9); R = Et, Ln = Y (10), Sm (11), Lu (12); R = iPr, Ln = Y (13), Sm (14), Lu (15)). Die Verbindungen wurden elementaranalytisch, NMR-spektroskopisch und massenspektrometrisch charakterisiert. Die Kristallstrukturen von 8 und 10 wurden aus Einkristallstruktur-Daten bestimmt.

Synthesis, characterization, and catalytic properties of bis[alkylindenyl]-, bis[alkenylindenyl]- and [alkenylindenyl(cyclopentadienyl)]zirconium dichloride complexes

Abstract 4,7-Dimethylindenyl lithium or 2,4,7-trimethylindenyl lithium reacts with 1-bromobutane, 1-chloro-2-propene, or 1-bromo-3-methyl-2-butene to give 3-butyl-4,7-dimethyl-1 H -indene ( 1 ), 3-(2-propene-1-yl)-2,4,7-trimethyl-1 H -indene ( 2 ), or 3-(3-methyl-2-butene-1-yl)-2,4,7-trimethyl-1 H -indene ( 3 ), respectively. Deprotonation of 1 – 3 with n -butyl lithium yields the lithium salts 1a – 3a . The reactions of 1a – 3a and of [1-(4-pentene-1-yl)indenyl]lithium ( 4a ) with zirconiumtetrachloride produce the complexes bis[1-butyl-4,7-dimethylindenyl]- ( 1b ), bis[1-(2-propene-1-yl)-2,4,7-trimethyl-indenyl]- ( 2b ), bis[1-(3-methyl-2-butene-1-yl)-2,4,7-trimethylindenyl]- ( 3b ) or bis[1-(4-pentene-1-yl)indenyl]zirconium dichloride ( 4b ). The reaction of cyclopentadienylzirconium trichloride with [2-(3-butene-1-yl)-4,7-dimethylindenyl]lithium or [2-(4-pentene-1-yl)-4,7-dimethylindenyl]lithium affords the mixed complexes [2-(3-butene-1-yl)-4,7-dimethylindenyl(cyclopentadienyl)]zirconium dichloride ( 5c ) or [2-(4-pentene-1-yl)-4,7-dimethylindenyl(cyclopentadienyl)]zirconium dichloride ( 6c ). All new compounds were characterized by elemental analysis, 1 H- and 13 C{ 1 H}-NMR spectroscopy as well as by mass spectrometry. In addition, single-crystal X-ray structural analysis was done for 3b . The complexes 1b – 4b , 5c , and 6c were tested as catalysts for the homopolymerization and copolymerization of ethene and propene and the results were compared to those of analogous compounds.

Si(CH2CH2SnH3)4 — a unique organotin hydride featuring 12 SnH units in a dendritic molecule. Single-crystal X-ray structures of tetrakis(2-stannylethylene)silane and tetrakis[2-(triphenylstannyl)ethylene]silane

Abstract Fourfold hydrostannation of tetravinylsilane affords the first generation metallodendrimer Si(CH2CH2SnPh3)4 (1). Selective bromination yields Si(CH2CH2SnBr3)4 (2), which can be reduced by LiAlH4 to give Si(CH2CH2SnH3)4 (3), containing 12 reactive SnH bonds. These novel dendritic organotin compounds were characterized by elemental analysis, spectroscopic studies (1H-, 13C-, 119Sn-NMR; IR) and by single-crystal X-ray structure determination. The molecular structures of 1 and 3 reveal increased conformational constraint in 1; the average SnH bond length in 3 is 1.60(7) A.

Erste Komplexe von Yttrium und Lutetium mit schwefelfunktionalisierten Cyclopentadienylliganden

Yttriumtrichlorid reagiert mit 2 Aquivalenten Na[C5H4CH2CH2SEt] (1) zu (η5-C5H4CH2CH2SEt)2YCl (2). Die schrittweise Reaktion von Lutetiumtrichlorid mit jeweils einem Aquivalent von 1 und Na[C5Me5] verlauft unter Bildung von (η5-C5Me5)(η5-C5H4CH2CH2SEt)LuCl (4). Durch Alkylierung von 2 bzw. 4 mit LiMe werden die Komplexe (η5-C5H4CH2CH2SEt)2YMe (3) bzw. (η5-C5Me5)(η5-C5H4CH2CH2SEt)LuMe (5) erhalten. Die Verbindungen wurden elementaranalytisch, NMR-spektroskopisch und massenspektrometrisch charakterisiert. Die Molekulstrukturen von 2 und 4 wurden aus Einkristallstruktur-Daten bestimmt. Organometallic Compounds of the Lanthanides. 132 First Complexes of Yttrium and Lutetium with Sulfur functionalized Cyclopentadienyl Ligands Yttrium trichloride reacts with 2 equivalents of Na[C5H4CH2CH2SEt] (1) to form (η5-C5H4CH2CH2SEt)2YCl (2). The stepwise reaction of lutetium trichloride with one equivalent of 1 and one equivalent of Na[C5Me5] yields (η5-C5Me5)(η5-C5H4CH2CH2SEt)LuCl (4). Alkylation of 2 and 4 with LiMe gives (η5-C5H4CH2CH2SEt)2YMe (3) or (η5-C5Me5)(η5-C5H4CH2CH2SEt)LuMe (5), respectively. The new compounds have been characterized by elemental analysis, NMR spectroscopy and mass spectrometry. The molecular structures of 2 and 4 were determined by single crystal X-ray diffraction.

Synthesis and characterization of 1- and 2-(ω-alken-1-yl)indenes, their lithium salts and dichlorozirconium(IV) complexes

A series of new 1-, 2-, and multi-substituted indenes has been synthesized and characterized. The reaction of indenyl lithium or 4,7-dimethylindenyl lithium with alkenyl bromides yielded a mixture of 1- and 3-allylindene ( 1 ), 3-(3-buten-1-yl)indene ( 2 ), 3-(4-penten-1-yl)indene ( 3 ), 3-allyl-4,7-dimethylindene ( 4 ), 3-(3-buten-1-yl)-4,7-dimethylindene ( 5 ), as well as 3-(4-penten-1-yl)-4,7-dimethylindene ( 6 ). The 2-substituted indenes 2-allylindene ( 7 ), 2-(3-buten-1-yl)indene ( 8 ), 2-(4-penten-1-yl)indene ( 9 ), 2-allyl-4,7-dimethylindene ( 10 ), 2-(3-buten-1-yl)-4,7-dimethylindene ( 11 ), and 2-(4-penten-1-yl)-4,7-dimethylindene ( 12 ) were prepared by PdCl 2 (DPPF) or NiCl 2 (DPPE) catalyzed cross-coupling reactions of the appropriate Grignard reagents with 2-bromoindene or 2-bromo-4,7-dimethylindene. Alkenylation of 3-methylindenyl lithium and 2,4,7-trimethylindenyl lithium produced 1-(3-buten-1-yl)-3-methylindene ( 13 ) or 1-(3-buten-1-yl)-2,4,7-trimethylindene ( 14 ), respectively. The indene derivatives 1 – 14 react with n -butyl lithium in hexane yielding the corresponding lithium salts 1a – 14a . Zirconium tetrachloride reacts with 1a , 2a , 4a – 6a and 11a – 14a under formation of the corresponding bis(indenyl)zirconium dichloride complexes 1b , 2b , 4b – 6b and 11b – 14b . All compounds were characterized by elemental analysis, 1 H and 13 C{ 1 H}-NMR spectroscopy and mass spectrometry, 5b and 12b also by single crystal X-ray structural analysis. 1b , 4b – 6b and 11b – 13b are active catalysts for the polymerization of ethene and propene.

Metallorganische Verbindungen der Lanthanoide. 155 [1] Synthese und Charakterisierung neuer Lanthanoidocen-Komplexe mit silylierten Cyclopentadienylliganden

Die Trichloride von Yttrium, Samarium und Lutetium reagieren mit zwei Aquivalenten K[C5H4SiEt3] (1) zu den dimeren Verbindungen [(η5-C5H4SiEt3)2LnCl]2 (Ln = Y (2), Sm (3), Lu (4)). Deren Umsetzung mit einem Aquivalent Methyllithium fuhrt zu den analogen dimeren Lanthanoidocenmethyl-Komplexen [(η5-C5H4SiEt3)2LnMe]2 (Ln = Y (5), Sm (6), Lu (7)). Analog erhalt man aus Samariumtrichlorid bzw. Lutetiumtrichlorid und zwei Aquivalenten K[1, 3-C5H3(SiMe3)2] sowie anschliesender aquimolarer Umsetzung mit Methyllithium die monomeren Methylkomplexe [η5-1, 3-C5H3(SiMe3)2]2LnMe(THF) (Ln = Sm (8), Lu (9)). Die neuen Verbindungen wurden durch Elementaranalyse, Massenspektrometrie, 1H- und 13C{1H}-NMR-Spektroskopie sowie 1 — 7 durch Einkristall-Rontgenstrukturanalyse charakterisiert. Organometallic Compounds of the Lanthanides. 155 [1] Synthesis and Characterization of New Lanthanocene Complexes containing Silylated Cyclopentadienyl Ligands The trichlorides of yttrium, samarium, and lutetium react with two equiv. of K[C5H4SiEt3] (1) to form the dimeric compounds [(η5-C5H4SiEt3)2LnCl]2 (Ln = Y (2), Sm (3), Lu (4)). These react with one equiv. of methyllithium to give the corresponding dimeric lanthanocenemethyl complexes [(η5-C5H4SiEt3)2LnMe]2 (Ln = Y (5), Sm (6), Lu (7)). The reaction between samarium trichloride and lutetium trichloride, respectively with two equiv. of K[1, 3-C5H3(SiMe3)2] followed by one equiv. of methyllithium results in the formation of the monomeric methyl complexes [η5-1, 3-C5H3(SiMe3)2]2LnMe(THF) (Ln = Sm (8), Lu (9)). The new compounds have been characterized by elemental analysis, mass spectrometry, 1H- and 13C{1H} NMR spectroscopy, as well as 1 — 7 by single crystal X-ray structure analysis.

Lithium and lanthanum complexes with acenaphthylene dianion. Molecular structure of [Li(Et2O)2]2μ2:η3[Li(η3:η3-C12H8)]2 complex

The lithium complex with the acenaphthylene dianion [Li(Et2O)2]2μ2:η3[Li(η3:η3-C12H8)]2 (1) was synthesized by the reduction of acenaphthylene with lithium in diethyl ether. According to the X-ray diffraction data, compound 1 has a reverse-sandwich structure with the bridging dianion μ2:η3[Li(η3:η3-C12H8)]2. Two lithium atoms in complex 1 are located between two coplanar acenaphthylene ligands of the μ2:η3[Li(η3:η3-C12H8)]22– dianion and are η3-coordinated with the five- and six-membered rings. The lanthanum complex with the acenaphthylene dianion [LaI2(THF)3]2(μ2-C12H8) (2) was synthesized by the reduction of acenaphthylene in THF with the lanthanum(iii) complex [LaI2(THF)3]2(μ2-C10H8) containing the naphthalene dianion. The 1H NMR spectrum of complex 2 in THF-d8 exhibits four signals of the acenaphthylene dianion, whose strong upfield shifts compared to those of free acenaphthylene indicate the dianionic character of the ligand. The highest upfield chemical shift belongs to the proton bound to the C atom on which, according to calculation, the maximum negative charge is concentrated.