Ekkehardt Hahn

Metallorganische verbindungen der lanthanoide: XXXI. Synthese und molekülstruktur einiger cyclopentadienyllutetiumhydride☆

Abstract The reaction of alkyl- and aryl-(dicyclopentadienyl)lutetium complexes ( 1 ) with H 2 or D 2 gives dimeric dicyclopentadienyllutetiumhydride ( 2 ) or -deuteride ( 3 ). Dicyclopentadienyllutetiumchloride ( 4 ) reacts with sodium in tetrahydrofuran (THF) with formation of [Na(THF) 6 ][(Cp 2 LuH) 3 H] ( 5 ). Tricyclopentadienyllutetium ( 6 ) reacts with NaH or NaD to give the complexes [Na(THF) 6 ][(Cp 3 Lu) 2 H]·2(THF) ( 7 ) or [Na(THF) 6 ][(Cp 3 Lu) 2 D]·2(THF) ( 8 ), respectively. The molecular structures of 2 and 7 were determined by single crystal X-ray diffraction.

The influence of electronic and steric effects and the importance of polymerization conditions in the ethylene polymerization with zirconocene/MAO catalysts

Abstract A series of Cp′(C5H5)ZrCl12 and Cp2′ZrCl12 precatalysts (Cp′ = C5Me4H, C4Me4P, C5Me5) together with (C5H5)2ZrCl12 has been investigated in terms of steric and electronic variations and their catalytic activities in combination with methylalumoxane (MAO) towards the polymerization of ethylene are compared. The changes in the steric environment were evaluated on the basis of the structural data available and supplemented by theoretical structural studies on the semiempirical (ZINDO, EHMO) and density functional (DF) level. The X-ray structures of (C5Me4H)2ZrCl2 (3) and (C4Me4P)(C5H5)ZrCl2 (4) have been determined (3: orthorhombic, Cmcm, a = 6.714(4), b = 17.275(4) c = 15.643(5) A , Z = 4 ; 4: monoclinic, P21/c, a = 8.8791(5), b = 7.8051(8), c = 20.9215(10) A β = 94.422(4)° , Z = 4. 91Zr NMR data for the above series has been measured and is correlated to changes in the HOMO-LUMO gap available from electronic structure calculations. Under mostly homogeneous polymerization conditions, at very low zirconium concentrations the order of the catalytic activity found for ethylene polymerizations is (C5H5)2ZrCl2 > (C5Me4H)(C5H5)ZrCl2 > (C5Me5)(C5H5)ZrCl2 > (C4Me4P)(C5H5)ZrCl2 > (C5Me4H)2ZrCl2 > (C5Me5)2ZrCl2 > (C4Me4P)2ZrCl2, which for the most part is inversely proportional to the steric demand of the ring ligands in the metallocene precatalysts except for the phospholyl systems. The lower activities of the phospholyl vs. the tetra- and penta-methylcyclopentadienyl compounds might imply an electronic effect such that the electron withdrawing phosphorus substituent decreases the activity, although further studies are needed to clarify this situation. Emphasis is placed on the control of the polymerization conditions and evaluation of the time-activity profiles. At higher zirconium concentrations an increased precipitation of polyethylene takes place during the course of polymerization and results in a transfer to the heterogeneous phase with a diffusion controlled reaction rate thereby invalidating any activity-comparing studies.

Organometallic compounds of the lanthanides

Abstract Bis(tetrahydrofuran)lithium dimethylbis(cyclopentadienyl)lutetate( III ) have been shown to react with t-butyl alcohol, t-butyl hydrosulfide, and phenyl hydroselenide in ether at −78°C to give the complexes (C 5 H 5 ) 2 Lu(OC 4 H 9 -t)(THF), (C 5 H 5 ) 2 Lu(SC 4 H 9 -t) 2 Li(THF) 2 , and (C 5 H 5 ) 2 Lu(SeC 6 H 5 ) 2 Li(THF) 2 , respectively. The analogous pentamethylcyclopentadienyl complexes (C 5 Me 5 ) 2 Lu(OC 4 H 9 -t)(THF), and (C 5 Me 5 ) 2 Lu(SC 4 H 9 -t) 2 Li(THF) 2 have been prepared from (C 5 Me 5 ) 2 Lu(μ- CH 3 ) 2 Li(THF) 2 and t-C 4 H 9 OH or t-C 4 H 9 SH, respectively. The new compounds have been characterized by elemental analysis and 1 H and 13 C NMR spectroscopy. The structures of the complexes (C 5 Me 5 ) 2 Lu(SC 4 H 9 -t) 2 Li(THF) 2 ( 7 ) and (C 5 H 5 ) 2 Lu(SeC 6 H 5 ) 2 Li(THF) 2 ( 8 ) have been determined by X-ray diffraction. The crystals of 7 are monoclinic with a 19.016(7), b 17.206(6), c 11.899(4) A, β 101.82(3), space group P 2 1 / n , Z = 4, R = 0.052, and 4228 observed ( I >- 2σ( I )) reflections. The crystals of 8 are monoclinic with a 21.60( 3 ), b 13.98(1), c 11.43(1) A, β 120.68(7)°, space group P 2 1 / a , Z = 4, R = 0.066, and 2615 observed ( I >- 3σ( I )) reflections.

Metallorganische verbindungen der lanthanoiden: XVIII. Synthese und struktur von tris[(1,2-dimethoxyethan)lithium]hexamethyllutetat(III)☆

Abstract The reaction of lutetium trichloride with methyllithium in diethyl ether in the presence of 1,2-dimethoxyethane gives [Li(dme)] 3 [Lu(CH 3 ) 6 ], its crystal structure shows an octahedral Lu(CH 3 ) 6 arrangement with methyl bridges to the lithium atoms of three tetrahedra, coordinated dme ligands. The complex crystallizes in the monoclinic space group Cc with a 1390(2), b 1083(2), c 1839(4) pm, and β 94.08(13)°.

Organometallic compounds of the lanthanide—XL. Recent developments in organolanthanide chemistry

Abstract Lanthanide trichlorides LnCl3 react with pentamethylcyclopentadienyl alkali metal derivatives with formation of novel compounds of the type C5Me5LnCl3MLn (M = alkali metal, L = donor solvent like Et2O, THF, DME). X-ray structural investigations showed that YbCl3 reacts with KC5Me5 in THF and DME with formation of [K(DME)3][K((C5Me5Yb)3Cl8K(DME)2)2]. Compounds of the type Cp2Ln(μ-CH3)2LiL2 and [Li(TMED)2][CpLn(CH3)3] are useful starting materials for the synthesis of new organolanthanide derivatives with bonds between the lanthanides and other elements. By their reactions with tBuSH, PhSeH, Ph2Ph, and Ph2AsH, e.g. the new organolutetium compounds (C5Me5)2Lu(μ-StBu)2Li(THF)2, (C5H5)2Lu(μ-SePh)2Li(THF)2, (C5H5)2Lu (μ-PPh2)2Li(TMED), and (C5H5)2Lu(μ-AsPh2)2Li(TMED) could be synthesized and characterized by X-ray structural analyses. Dicyclopentadienylsamarium chloride reacts with trimethylsilyl lithium in DME with formation of [Li(DME)3][(C5H5)2Sm(SiMe3)2], whereas in the reaction of (C5H5)2Sm(μ-Cl)2Na(DME) with LiGeMe3 redistribution occurs with formation of hexamethyldigermane and [Li(DME)3][(C5H5)3SmClSm(C5H5)3]. The same anion is formed in the reaction of NaCl with (C5H5)3Sm in DME. Finally LiN3 reacts with (C5H5)3Sm in DME with formation of the complex [Li(DME)3][(C5H5)3SmNNNSm(C5H5)3].

Metallorganische verbindungen der lanthanoide: XXXV. Bis(tetramethylethylendiamin)lithium tetrakis-t-butylluteta(III): synthese, molekülstruktur und reatives verhalten gegenüber α,β-ungesättigten carbonylverbindungen

Abstract LuCl3 reacts with t-butyllithium in the presence of ether and tetramethylethylene diamine (tmed) to form [Li(tmed)2][Lu(t-C4H9)4], the structure of which has been elucidated through complete X-ray analysis. The crystals are orthorhombic with a 20.995(9), b 18.310(7), c 9.527(2) A, space group P21ab, Z = 4, D(calcd) 1.17 g cm−3, R = 0.035, and 2471 observed reflections. The compound undergoes 1,2-addition to cinnamic aldehyde, benzalacetone, 1-phenylbutene-2-methyl-3-one, 2-methylbutene-3-one and cyclohexanone, respectively, to give after hydrolysis of the reaction mixture α-t-butyl-substituted enoles. The reaction products were identified by means of GC/MS methods.

Some novel halide- and alkyl-derivatives of pentamethylcyclopentadienyllanthanum, -praseodymium, -ytterbium and -lutetium

Abstract LaCl 3 and PrCl 3 react with NaC 5 Me 5 or KC 5 Me 5 in tetrahydrofuran in the presence of ether or dimethoxyethane (dme) to form the new complexes (C 5 Me 5 ) 2 La(μ-Cl) 2 K(L 2 ), (C 5 Me 5 ) 2 Pr(μ-Cl) 2 Na(L 2 ) (L = Et 2 O, dme) and, C 5 Me 5 PrCl 3 Na(Et 2 O). These compounds react with LiCH 3 or LiCH 2 SiMe 3 forming new alkyl derivatives of the type (C 5 Me 5 ) 2 Ln(μCH 3 ) 2 Li(tmed) (Ln = La, Lu, tmed = tetramethylethylenediamine), [Li(dme) 3 ] [(C 5 Me 5 ) 2 Lu(CH 2 SiMe 3 ) 2 ] and [Li(tmed) 2 ] [C 5 Me 5 Ln(CH 3 ) 3 ] (Ln = Yb, Lu). The structure of (C 5 Me 5 ) 2 Pr(μ-Cl) 2 Na(dme) 2 was determined by X-ray diffraction.

Metallorganische Verbindungen der Lanthanoide. XXIII: Synthese und Struktur von [Li(tmed)2][C5Me5Lu(CH3)3]

Abstract LaCl 3 , YbCl 3 and LuCl 3 react with NaC 5 Me 5 and LiCH 3 or LiCH 2 SiMe 3 in tetrahydrofuran in the presence of tetramethylethylenediamine (tmed) under formation of the new complexes (C 5 Me 5 ) 2 Ln(μ-CH 3 ) 2 Li(tmed) (Ln = La, Lu), [Li(dme) 2 ][(C 5 Me 5 ) 2 Lu(CH 2 SiMe 3 ) 2 ] and [Li(tmed) 2 ][C 5 Me 5 Ln(CH 3 ) 3 ] (Ln= Yb, Lu). The structure of [Li(tmed) 2 ][C 5 Me 5 Lu(CH 3 ) 3 ] has been determined by X-ray diffraction.

Single-Step Synthesis of Organometallic Molecular Squares from NR,NR',NR'',NR'''-Substituted Benzobiscarbenes.

The single-step multicomponent self-assembly of molecular squares featuring four bridging benzobiscarbenes and four PdII (allyl) or IrI (COD) vertices is presented. Four equivalents of the linear benzobisimidazolium salt [1](PF6 )2 react with two equivalents of [Pd(allyl)Cl]2 or [IrCl(COD)]2 in the presence of Cs2 CO3 to yield the tetranuclear octacarbene molecular squares [2](PF6 )4 (M=Pd) and [3](PF6 )4 (M=Ir), respectively. Compounds [2](PF6 )4 and [3](PF6 )4 feature exclusively M-carbon bonds making them the first purely organometallic molecular squares.

Electrophilic nitrosyls: preparation, structure, and reactivity of cis-chloronitrosylbis(pyridine-2-carboxylato)ruthenium and related complexes

Reaction of [RuCl5(NO)]2– with pyridine-2-carboxylic acid (Hpyca) at pH 4.5 gave cis[RuCl(pyca)2(NO)], isomer(I), with the acetate groups co-ordinated trans to the nitrosyl and chloro-ligands and the pyridine nitrogens trans to one another, as proved by an X-ray crystallographic investigation. Crystal data: orthorhombic, space group P212121, a=15.297(8), b=11.401(5), and c= 8.224(3)A; R= 0.072. A second product of the reaction was [RuCl3(pyca)(NO)]–. At pH 7 the reaction gave a second isomer of cis-[RuCl(pyca)2(NO)], (II), with the acetate oxygen trans to NO and a pyridine nitrogen traps to Cl. Reaction of quinoline-2-carboxylic acid (Hgnca) with [RuCl5(NO)]2–at pH 4.5 gave cis-[RuCl(qnca)2(NO)], isomer (II), and at pH 7 [Ru(OH)(qnca)2(NO)]. With [OsCl5(NO)]2– and Hpyca only [OsCl3(pyca)(NO)]–, was obtained. It was not possible to isomerise isomer (I) thermally without decomposition by loss of HCl. Reactions of the nitrosyl group in isomers (I) and (II) with nucleophiles were complicated by ligand-replacement reactions.