Georg Riepl

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.

Asymmetric Catalysis. : 8. X-ray structure analysis of the asymmetric hydrosilylation catalyst Cyclo-octa-1,5-diene-pyrrol-2-carbald-(s)- 1-phenylethyliminato—rhodium(I)

Abstract Complex (-) 578− I was prepared by reaction of [(COD-1,5)RhCl] 2 with the Na derivative of the Schiff base, derived from pyrrol-2-carbaldehyde and (s)-l-phenylethylamine. An X-ray structure analysis for (-) 578− I, an enantioselective catalyst for the hydrosilylation of acetophenone, was carried out. The (s)-l-phenylethyl group, responsible for the optical induction, adopts the following conformation: the phenyl and methyl substituents of the asymmetric carbon atom C13 stagger the C21H bond in the chelate plane, and the CH bond of the asymmetric carbon atom C13 is oriented towards the mid-point of the coordinated double bond ClC2 of the COD1,5 ligand.

Optically active transition-metal compounds. Stereochemistry and crystal structure determination of [η5-C5H5)CoI-NC5H4C(R)NCH(CH3)(C6H5)]+I−, R = CH3 ☆ ☆☆

Abstract The crystal structures and absolute configurations of (η 5 -C 5 H 5 )-CoI(NC 4 H 3 -C(R)=N( S )-CH(CH 3 )(C 6 H 5 )) (R = H, compound I; R = CH 3 , compound II) have been determined by single crystal X-ray diffraction. Crystals of compound I are orthorhombic, with a 11.084(6), b 12.107(6) and c 13.121(7) A, space group P 2 1 2 1 2 1 and d (calcd, Z = 4) 1.69 g cm −3 The structure was solved by the Patterson technique and refined with use of full matrix least-squares methods to R ( F ) = 0.031 and R w ( F ) = 0.028. Compound II is nearly isomorphous and isostructural; a 11.246(6), b 11.923(6) and c 13.370(7) A, d (calc., Z = 4) 1.71 g cm −3 and was refined to the final agreement factors of R ( F ) = 0.044 and R w ( F ) = 0.035. The Co atom has a distorted tetrahedral coordination, with Co-I 2.595(2) for I and 2.607(2) A for II; Co-(η 5 -C 5 H 5 ring centroid) 1.681(4) and 1.703(5) A; Co-N(pyrrole) 1.905(9) and 1.885(9) A; Co-N(imine) 1.971(8) and 2.003(9) A, all the parameters being well within values found in the literature. The configuration around the chiral carbon of the phenylethylamine is S for both compounds, whereas the configuration around the metal is R in I and S in II. The different metal configurations in I and II have their origin in the two different substituents (R = H, CH 3 ) at the imine carbon atoms of the chelate ring, which induce completely different conformations of the ( S )-CH(CH 3 )(C 6 H 5 ) moiety in the two complexes. For both compounds the thermodynamically less stable isomer is enriched upon crystallization. Also, for compound I the solution and solid state conformations are almost opposite to each other, the conformation in the solid reflecting intramolecular interactions (phenyl/C 5 H 5 attraction).

Optically active transition-metal compounds: XXII. Stereochemistry and crystal structure determination of (η5-C5H5)CoI(NC4H3C(R)=N(S)-CH(CH3)(C6H5)) (R = H, CH3)☆

Abstract The crystal structures and absolute configurations of (η 5 -C 5 H 5 )-CoI(NC 4 H 3 -C(R)=N( S )-CH(CH 3 )(C 6 H 5 )) (R = H, compound I; R = CH 3 , compound II) have been determined by single crystal X-ray diffraction. Crystals of compound I are orthorhombic, with a 11.084(6), b 12.107(6) and c 13.121(7) A, space group P 2 1 2 1 2 1 and d (calcd, Z = 4) 1.69 g cm −3 The structure was solved by the Patterson technique and refined with use of full matrix least-squares methods to R ( F ) = 0.031 and R w ( F ) = 0.028. Compound II is nearly isomorphous and isostructural; a 11.246(6), b 11.923(6) and c 13.370(7) A, d (calc., Z = 4) 1.71 g cm −3 and was refined to the final agreement factors of R ( F ) = 0.044 and R w ( F ) = 0.035. The Co atom has a distorted tetrahedral coordination, with Co-I 2.595(2) for I and 2.607(2) A for II; Co-(η 5 -C 5 H 5 ring centroid) 1.681(4) and 1.703(5) A; Co-N(pyrrole) 1.905(9) and 1.885(9) A; Co-N(imine) 1.971(8) and 2.003(9) A, all the parameters being well within values found in the literature. The configuration around the chiral carbon of the phenylethylamine is S for both compounds, whereas the configuration around the metal is R in I and S in II. The different metal configurations in I and II have their origin in the two different substituents (R = H, CH 3 ) at the imine carbon atoms of the chelate ring, which induce completely different conformations of the ( S )-CH(CH 3 )(C 6 H 5 ) moiety in the two complexes. For both compounds the thermodynamically less stable isomer is enriched upon crystallization. Also, for compound I the solution and solid state conformations are almost opposite to each other, the conformation in the solid reflecting intramolecular interactions (phenyl/C 5 H 5 attraction).