Anna Rufińska

27Al-NMR-Spektroskopie zur Charakterisierung von Organoaluminium-Verbindungen

Abstract 27Al NMR parameters of organoaluminium compounds of the type (RnAlX3-n)m (n = 0, 1, 2, 3; m = 1, 2, 3) and (R2 AlO(CH 2 ) 2 Y )2 (Y = OR′, NR′2) were determined. In related organoaluminium compounds the chemical shift δ(27Al) is an indicator for the coordination number of aluminium atoms: In the investigated monomeric compounds R3Al, with three-coordinated aluminium δ(27Al) lies between 280 and 210 ppm, whereas for four-coordinated aluminium in (RnAlX3-n)m complexes (n = 1, 2, 3; m = 2,3) δ(27Al) is between 180 and 125 ppm. In organoaluminium compounds with five-coordinated aluminium atoms δ(27Al) was found between 125 and 100 ppm. Inorganic complexes of the type XAl(OAlX2)2-(OBR)4 have distinct 27Al shift ranges for their four- (δ ∼ 90) and five- (δ ∼ 45) coordinated aluminium atoms. Owing to the relationship between δ(27Al) and the coordination number, organoaluminium compounds of unknown structure and the adducts of RnAlX3-n units with donors can be easily characterised by 27Al NMR spectroscopy.

Drei- oder Vierfach-Koordination des Aluminiums in Alkylaluminiumphenoxiden und deren Unterscheidung durch 27Al-NMR-Spektroskopie

The 27Al NMR spectra for a series of aryloxyaluminium compounds [RnAl(OAr)3−n]m (R  methyl, isobutyl; n  0–2; m  1, 2, 3) with various alkyl substituents in the 2 and 6 positions of the phenoxy rings have been measured. The δ(27Al) resonances give an indication of the number of aryloxy ligands and the coordination number of each Al atom. Monomeric R2AlOAr compounds have δ(27Al) resonances around 190 ppm whereas dimeric analogues give signals at 167 ppm. The 27Al NMR resonances for monomeric RAl(OAr)2 are found at ca. 100 ppm while those for [Al(OAr)3]2, where the aluminium atoms are solely bonded to aryloxy groups, lie at ca. 50 ppm. Characteristic shifts of the resonances were also observed for complexes of these compounds with THF, whereby it was found that the resulting change Δδ(27Al) decreases with increasing number of aryloxy ligands. The crystal structures of three selected compounds, 3, 8 and 11, were determined by X-ray crystallography.

Fluxional behaviour in η3-allyl complexes of cr, mo and w as shown by magnetisation transfer difference spectroscopy (MTDS)

Abstract (η3-allyl)4M2 (M  Cr, I;M  Mo, II) exist in solution as mixtures of two isomers (Ia/Ib  60/40; IIa/IIb  90/10). Each isomer has two inequivalent allyl groups which are trans to one another and bridge the two metal atoms. The other allyl groups are bonded to each one of the metals. In the major isomer these two allyl groups are cis, whereas in the minor isomer they are trans. At temperatures above 30°C for I (8O°C for II), interconversion of the isomers Ia and Ib (IIa and IIb) can be detected by magnetisation transfer difference spectroscopy (MTDS) (1H NMR 400 MHz). This interconversion proceeds by exchange of syn (anti) protons of the non-bridging allyl groups of Ia (IIa) with syn (anti) protons of the non-bridging allyl groups of Ib (IIb). In addition, in Ia and Ib syn—syn (anti—anti) exchange of the protons of the bridging allyl groups can be detected. (η3-allyl)4M (M  Mo, III; M  W, IV) shows fluxional behaviour at temperatures above 70°C for III (90°C for IV). Syn—anti and also syn—syn (anti—anti) exchange takes place. Each of these processes can be monitored separately by MTDS.

Developing potentially useful organometallic Lewis acid catalysts: (η-cyclopentadienyl)zirconium trichloride derivatives

Abstract The organometallic Lewis acid (η-cyclopentadienyl)zirconium trichloride ( 2 ) was obtained from bis(cyclopentadienyl)zirconium dichloride ( 1 ) and chlorine by means of a radical induced metal-Cp bond cleavage. Reaction of 2 with tetrahydrofuran gave the CpZrCl 3 -bis(tetrahydrofuran) adduct 3 ; treatment of either 2 or 3 with excess dimethylformamide furnished CpZrCl 3 (dmf) 2 ( 4 ). (η-Methylcyclopentadienyl)bis(tetrahydrofuran)zirconium trichloride ( 7 ) was prepared by treatment of ZrCl 4 (thf) 2 ( 6 ) with one molar equivalent of the (methylcyclopentadienyl)thallium reagent 5 . Complexes 3, 4 and 7 were characterized by X-ray diffraction studies and their dynamic NMR spectra were recorded. Complex 3 crystallizes in space group P 2 1 / n with cell parameters a 8.155(1), b 13.342(2), c 15.775(1) A, β 104.81(1)°, Z = 4, R = 0.041, R w = 0.056. CpZrCl 3 (dmf) 2 ( 4 ) crystallizes in space group P 2 1 / c with cell parameters a 7.790(1), b 15.445(2), c 13.893(1) A, β 93.94(1)°, Z = 4, R = 0.032, R w = 0.052. Complex 7 crystallizes in space group P 2 1 / n with cell parameters a 10.242(2), b 12.836(2). c 13.683(1) A, β106.37 (1)°, Z = 4, R = 0.037, R w = 0.039. The (cyclopentadienyl)bis(tetrahydrofuran)zirconium trichloride adduct 3 selectively catalyzed the Diels-Alder addition of 2,3-dimethylbutadiene and methacrolein at ambient temperature to give 1,3,4-trimethyl-3-cyclohexenyl-1-carbaldehyde ( 13 ). However, the CpZrCl 3 -Lewis acid catalyzed rearrangement of 13 to 1,3,4-trimethylbicyclo[2.2.1]heptan-2-one ( 14 ) does not take place at a significant rate until ca. 150°C.

Optisch aktive übergangsmetall-komplexe: LXXXV. Darstellung, eigenschaften und konformationsanalyse von optisch aktiven CpCo-Komplexen☆

Abstract The Schiff bases from 2-pyridine-carbaldehyde, 2-acetylpyridine, 2-benzoylpyridine, 2-pyrrole-carbaldehyde, and 2-acetylpyrrole with (−)-1-phenylethylamine and (−)-3-aminomethylpinane were synthesized. The pyridine Schiff bases αγ were used as neutral compounds and the pyrrole Schiff bases δHζH were used as anions δζ in the reaction with CpCo(CO)I 2 and CpCo(CO)(C 3 F 7 )I. In place of the covalently bonded iodine ligand different monodentate ligands bp were incorporated. Compounds of the type CpCo(αζ)(ap) and [CpCo(αζ)(ap)]X with X = I, PF 6 are formed. All the complexes consist of pairs of diastereomers differing only in the Co configuration. The diastereomers exhibit different 1 H NMR spectra. The Co configuration in all the compounds is labile except the C 3 F 7 derivatives. A conformational analysis establishes which of the diastereomers is the thermodynamically more stable one, on the basis of the following arguments and methods: NOE-difference spectroscopy, diastereomer ratios at equilibrium, chemical shifts of the Cp signals, and CD spectra.

Optisch Aktive übergangsmetall-komplexe : LXXVII. Konformationsanlyse von C5H5(CO)2Mo-amidinat-komplexen mit hilfe des kern-overhauser-effekts

Abstract C5H5(CO)2Mo-benzamidinato complexes with various N-substituents were investigated by 1H NMR spectroscopy at 400 MHz. The preferred conformations of the thermodynamically more stable isomers were established by means of Nuclear-Overhauser-Effect Difference Spectroscopy.

Ein schneller zugang zu 103Rh-NMR-parametern von organorhodium-komplexen

Abstract The two-dimensional, indirect 1 H, 103 Rh NMR spectroscopy which allows rapid measurement of 103 Rh NRM parameters by means of the detection of the protons, is introduced. The efficiency of this technique is demonstrated with organorhodium phosphane complexes, in that δ( 103 Rh) and J (Rh,P), J (P,H) as well as their relative signs could be determined, even for dilute samples, in an experiment with short recording times.

195Pt NMR of organoplatinum compounds

Abstract The 195 Pt chemical shifts of several organoplatinum compounds in solution have been determined. The δ( 195 Pt) values of the phosphine-Pt II and -Pt 0 compounds lie in separate ranges, and allow the metal-diene systems to be characterized either as metallacyclopentene or as η 2 -bonded diene. Although the two isomers of bis(η 3 -allyl)Pt (VIII) formally should be regarded as Pt II compounds their 195 Pt shifts clearly lie in the region for Pt 0 compounds. The large separation between the 195 Pt signals and the difference in 195 Pt- T 1 values for the two isomers of VIII are in accord with their having different geometries around the metal.

183W NMR Data (δ(183W), nJ(W,H), and 1J(W,F)) for tungsten(II) metallacycles via two-dimensional indirect (1H, 183W) NMR spectroscopy

Abstract The 183 W data for the tungsten(II) metallacycles (Me) 2 N(CH 2 ) 2 N(CHC 6 H 4 )-W(CO) 3 X ( 1 : X = F; 2 : X = Cl; 3 : X = Br; 4 : X = I), (C 6 H 4 XCH)N(CH 2 ) 2 N(CHC 6 -H 4 )W(CO) 3 X ( 5 : X = Cl; 6 : X = Br; 7 : X = I), H 2 N(CH 2 ) 2 N(CHC 6 H 4 )W(CO) 3 F ( 8 ), H 2 N(C 6 H 4 )N(CHC 6 F 4 )W(CO) 3 F ( 9 ), and H 2 N(C 6 H 4 )N(CHC 6 H 4 )W(CO) 3 Cl ( 10 ) have been obtained by using n J (W,H) ( n – 3) couplings and the indirect two-dimensional ( 1 H, 183 W) detection scheme. The chemical shifts δ( 183 W), 3 J (H,W), together with its dihedral angle dependence, and the values 1 J (F,W) for these complexes are discussed.

Asymmetrische katalysen: XXVII. Rh-komplexe mit von tropolon abgeleiteten optisch aktiven liganden

Abstract In tropolone, the oxygen atoms were replaced stepwise by NC★ HMePh groups. The resulting compounds were introduced as anionic ligands into Rh(COD) complexes. The new ligands and complexes were analytically and spectroscopically characterized. The conformation of the NCH(Me)(Ph) substituent in the Rh(COD) complex of the troponiminate anion was determined by NOE 1 H NMR difference spectroscopy. Only small optical inductions were obtained in the asymmetric hydrosilylation of acetophenone with diphenylsilane using the in situ catalysts from [Rh(COD)Cl] 2 and the new ligands as well as the new complexes. The enantiomeric excess rose to 5 and 33%, respectively, when ( + )-norphos and (−) -diop were used as cocatalysts and the new complexes as procatalysts.