Max Herberhold

Gehinderte ligandenbewegungen in übergangsmetall komplexen : III. Olefinrotation in cclopentadienyl-mangan-dicarbonyl- äthylen und cyclopentadienyl-chrom-carbonyl- nitrosyl-äthylen☆

Abstract The temperature dependence of the 1 H NMR spectra indicates that the ethylene ligand in the isoelectronic complexes, cyclopentadienylmanganese dicarbonyl ethylene, C 5 H 5 Mn(CO) 2 (CH 2 =CH 2 ) (I), and cyclopentadienylchromium carbonyl nitrosyl ethylene, C 5 H 5 Cr(CO)(NO)(CH 2 =CH 2 ) (II), undergoes a hindered rotation around the metalue5f8olefin bond axis. In addition to the ethylene complexes I and II, the corresponding complexes containing trans -D 2 - ethylene, C 5 H 5 Mn(CO) 2 ( trans -CHD=CHD)(ID) and C 5 H 5 Cr(CO)(NO)- ( trans -CHD=CHD) (IID), have been prepared and studied in order to support the analysis of the 1 H NMR spectra of I and II. The activation barriers for the ligand motion were fond to be Δ G ‡ 1 68 = 8.4 ± 0.2 kcal/mole in the case of I and ID, and Δ G ‡ 2 38 = 11.4 ± 0.2 kcal/mole in the case of II and IID.

Neue π-komplexe des chroms mit monoalkenen und alkinen

Abstract Photolysis of cyclopentadienyldicarbonylnitrosylchromium, C 5 H 5 Cr(CO) 2 NO, in cyclooctene solution results in the formation of an olefin complex, C 5 H 5 Cr(CO)(NO)(C 8 H 14 ). The π-bonded cycloolefin is displaced by various monodentate ligands, L. Some characteristic coordination compounds of the type C 5 H 5 Cr(CO)(NO)L containing either monoolefins or alkynes are described.

Gehinderte Ligandenbewegungen in Übergangsmetallkomplexen : VII. Rotation der olefinliganden L = malein- und furmarsäuredimethylester in komplexen des typs C5H5Mn(CO)2L und C5H5Cr(CO)(NO)L

Abstract The restricted rotation of the olefin ligands L = dimethyl maleate and dimethyl fumarate in complexes of the type C 5 H 5 Mn(CO) 2 L and C 5 H 5 Cr(CO)-(NO)L, respectively, has been investigated on the basis of their temperature-dependent 1 H NMR spectra. The olefinic ligand is arranged preferably in a position where the Cue5fbC double bond is parallel to the plane of the cyclopentadienyl ring. The possible stereoisomers are discussed using this model. The 1 H NMR spectra of C 5 H 5 Cr(CO)(NO)( trans -CH 3 OOCue5f8CHue5fbCHue5f8COOCH 3 ) provide direct evidence that the configuration (R or S) at the metal is stable up to 120°C, and that the restricted motion of the olefin is exclusively rotation around the metal—olefin bond. The activation barriers of the olefin rotation are found to be appreciably lower in the C 5 H 5 Mn(CO) 2 L complexes (Δ G ≠ ( T C ) 11–12 kcal mol −1 ) than in the isoelectric C 5 H 5 Cr(CO)(NO)L compounds (Δ G ≠ ( T C ) 15–20 kcal mol −1 ).

Übergangsmetallkomplexe mit N-haltigen liganden : VIII. Heptacarbonyl-dieisen-komplexe Fe2(CO)7L mit cyclischen azoverbindungen und 1,2-diazinen

Abstract Binuclear complexes of the type Fe 2 (CO) 7 L (L = a-e) can be obtained by the reaction of enneacarbonyldiiron, Fe 2 (CO) 9 , with the heterocyclic systems 2,3-diazabicyclo[2.2.1]heptene-2 (a), 2,2,5,5-bis(pentamethyleno)-1,3,4-thiadiazoline (b), benzo[ c ]cinnoline (c), phthalazine (d) and pyridazine (e). The IR and 1 H NMR spectra of these complexes indicate that the 1,2-diaza group of the heterocyclic compound L functions as a bridging four-electron ligand which is coordinated to the iron atoms through the lone pairs of electrons at the two nitrogen atoms. Furthermore, the complexes contain a CO bridge. The formation of the binuclear Fe 2 (CO) 7 L complexes (L = a-e) proceeds via the mononuclear complexes Fe(CO) 4 L. Decarbonylation of Fe 2 (CO) 7 L to give Fe 2 (CO) 6 L succeeds only with complexes with the cyclic azo ligands L = a, b or c, but not with complexes with the aromatic 1,2-diazines L = d or e.

Photonitrosylierung von decacarbonyl-dimangan

Abstract Photo-induced nitrosylation of Mn 2 (CO) 10 in n-pentane solution results in the formation of Mn(NO) 3 CO via Mn(CO) 4 NO, while complete decarbonylation is observed in tetrahydrofuran. The manganese-nitrosyl complexes formed in THF solution react with monodentate ligands (L) to give complexes of the type Mn(NO) 3 L (L = PPh 3 , AsPh 3 , P(OCH 3 ) 3 ), and with bifunctional bridging ligands (Lue5f8L) to give binuclear complexes (ON) 3 Mn(Lue5f8L)Mn(NO) 3 (Lue5f8L = 1,2-di-2-pyridylethylene, 1,2-di-4-pyridylethylene, 1,2-bis(diphenylphosphino)ethane).

π-komplexverbindungen der methoxy-substituierten äthylene : I. Das system cyclopentadienyl-mangan-dicarbonyl-olefin

Abstract The influence of methoxy substituents upon the coordinative properties of olefin ligands has been investigated for complexes of the type C 5 H 5 Mn(CO) 2 L [L = CH 2 ue5fbCH 2 , (CH 3 O)CHue5fbCH 2 , (CH 3 O) 2 Cue5fbCH 2 , cis - and trans -(CH 3 O)CHue5fbCH(OCH 3 ), (CH 3 O) 2 Cue5fbC(OCH 3 ) 2 ]. All complexes possess temperature-dependent 1 H-NMR spectra which indicate restricted rotation of the π-bonded olefin around the metal—olefin bond at room temperature in solution. In comparison with ethylene, the olefins methyl vinyl ether and 1,1-dimethoxyethylene increase the charge density at the metal, while tetramethoxyethylene — due to the inductive effect of the four CH 3 O substituents — causes a decrease of the charge.