Koordinationsverbindungen des Typs C₅H₅Cr(CO)(NO)L mit Olefin‐ und Acetylenliganden

Abstract

Durch photoinduzierte Substitution eines CO-Liganden in C5H5Cr(CO)zNO (1) wurden Olefin-und Acetylen-n-Komplexe des Typs C5H5Cr(CO)(NO)L, 2 dargestellt, die am Zentralmetall ein Chiralitatszentrum besitzen. Neben den C~H5Cr(CO)(NO)L-Verbindungen mit L = Athylen: 2a, Propen: 2b und Styrol: 2c wurden zwei Gruppen von Olefinkomplexen untersucht: Zum einen Komplexe mit Cycloolefinen 2d-m, zum anderen Komplexe mit Akzeptorolefinen 2n -t der Malein-oder Fumarsaurereihe ; zum Vergleich wurden einige CsHsCr(CO)(NO)L-Verbindungen 2 u-z mit 1, = Alkin dargestellt. Die Komplexe wurden anhand typischer IRund IH-NMR-Daten charakterisiert ; in einigen Fallen konnte anhand der temperdturabhkngigen IH-NMR-Spektren auf eine gehinderte Rotation des x-gebundenen Liganden L geschlossen werden. Der Komplex des 1,5-Cyclooctadiens, C5H5Cr(CO)(NO)CgH12 (21), wandelt sich leicht in das zweikernige Derivat C S H~~[ C~H~C~( C O ) ( N O ) ] * (31) urn, das eine 1,5-Cyclooctadien-Briicke enthalt. CoordinationCompounds of theTyp? CSHsCr(CO)(NO)L Containing Olefin andAcetylene LigandsThe photoinduced substitution of a CO ligand in C5H&r(CO)z(NO) (1) has been used to prepare olefin and acetylene x-complexes of the type C5H5Cr(CO)(NO)L 2, which possess a center of chirality at the metal. In addition to C5HxCr(CO)(NO)L compounds with L = ethylene: 2a, propene: 2b or styrene: 2c, two groups of olefin complexes have been investigated: complexes containing cycloolefins 2dm, and complexes containing acceptor olefins 2n-t of the maleic and fumaric acid type. For purposesof comparison, some C5H5Cr(CO)(NO)L compounds 2u-z with L = alkyne have also been isolated. The complexes have been characterised by typical IR-and 1H-N MR spectroscopic data; in some cases, hindered rotation of the x-bonded ligand L has been deduced from the temperature dependence of the 1H-NMR spectra. The complex of 1,5-cyclooctadiene, C~H~C~ ( C O ) ( N O ) C~H L~ (21), is easily converted into the binuclear derivative C E H~~[ C~H~C~( C O ) ( N O ) ]~ (31) containing a bridging 1,5-~yclooctadiene ligand.Wegen der technisch-wirtschaftlichen Bedeutung homogener Olefinreaktionen, die unter der Wirkung von Ubergangsmetallkatalysatoren ablaufen 1-4), ist die systematische Untersuchung stabiler Modellkomplexe mit x-gebundenen Olefinliganden *) Korrespondenz bitte an diesen Autor richten.

s-trans-Diene Complexes of a First-Row Transition Metal. Half-Sandwich s-trans-η4-1,3-Diene Nitrosyl Complexes of Chromium

“…Consistent with the reactivity of the parent (cyclopentadienyl)chromium system, , (C 5 Me 5 )CrNO(CO) 2 ( 4 ) is strongly resistant to double carbonyl substitution in the presence of either simple alkenes or nonconjugated dienes (e.g., 1,5-hexadiene), leading to monosubstitution products only, even upon prolonged photolysis in the presence of excess alkene. Thus, photolysis of dicarbonyl complex 4 in the presence of a large excess of propene or allyltrimethylsilane provides η 2 -alkene complexes 6a and 6b , respectively, each as a mixture of otherwise unassigned diastereomers (Scheme 1).…”

“…The synthesis of chromium diene complexes in this series is complicated by the inherent instability of complexes of the form [(C 5 H 5 )Cr(NO)X 2 ] 2 (X = halide, alkyl), demanding an alternative strategy to those used for molybdenum and tungsten. Photolytic carbonyl substitution has been previously demonstrated for (C 5 H 5 )CrNO(CO) 2 , 1 , providing η 2 -alkene and η 2 -alkyne complexes, although no evidence for a second carbonyl substitution has been obtained. , Unfortunately, however, the initial substitution products remain photolabile; reactions can be run only to low conversions and provide impractically low isolated yields. No previous investigation of photochemical substitution using conjugated dienes has been reported for this system.…”

Recent organometallic nitrosyl chemistry

“…178 Numerous olefins and acetylenes coordinate to the chromium center in the reaction summarized by eq 27 (L = olefin, acetylene). 179 bound olefin is readily displaceable by other nitrogendonor ligands.180 A related tungsten acetylene complex has been obtained by an entirely different route. 148 The complex containing 1,5-cyclooctadiene, i.e.…”

Nickel and Platinum 1,2-Dibromoacenaphthylene Chemistry

“…The difference is the olefinic character of the 1,2-double bond of the acenaphthylene unit. Acenaphthylene itself shows this character and has yielded several π-complexes through coordination of the 1,2-double bond. − With this point of view, 1,2-dibromoacenaphthylene resembles more a vinyl halide than an aryl halide. Oxidative-addition of vinyl halides to group 10 metals has attracted attention due to the importance of group 10 metal catalyzed coupling reactions of vinyl halides. , Coordination of the vinyl halide through the C−C double bond is believed to be on the path to oxidative-addition, and Pd and Pt π-complexes that subsequently undergo oxidative-addition have been isolated or observed. ,− However, for Ni the only vinyl halide π-complexes to have been isolated are stable to oxidative-addition, − marking 2 a rare example of a Ni(0) π-complex that subsequently undergoes oxidative-addition …”