Olefin complexes containing

The model we have used for the description of the transition states implies that also the corresponding n-olefin complexes contain an asymmetric metal atom and that changes of configuration at the metal occur more slowly than the intramolecular transformation of the 7i-complex into the metal-alkyl complex. 

The reaction proceeds more rapidly, in higher yield, regiospedfically P if the olefin in the [Fp(olefin)] complex contains an electron-withdrawing group such as ester or aldehyde group. 

Finally, reaction of the discrete rhodium-alkoxo complex containing a tethered olefin shown in Equation 9.83 has been shown to undergo insertion of the alkene into the metal-alkoxo bond, followed by p-hydrogen elimination. This mechanism has also been shown to occur by a stereochemical labeling study in which the stereochemistry of the olefinic product reveals the mode of addition. The stereochemistry of the product from reaction of the alkoxo olefin complex containing deuterium in the trans position of the coordinated alkene shows that a syn addition of the rhodium and oxygen occurred across the carbon-carbon bond. ... 

Potassium trichloro(ethene)platinate(II), also known as Zeise s salt, has the formula K[PtCl3(C2H4)]H20 and contains rj -ethylene ligand. The compound is a yeUow-coloured coordination complex that is stable in air. The platinum atom has a square planar geometry. While reacting K2PtCl4 with ethanol in 1827, a Danish chemist Zeise synthesized this metal olefin complex containing a platinum-bound ethylene moiety, which incidentally represented the first metal—olefin complex. 

Summary of Magnetic Resonance Data for Miscellaneous Olefin Complexes Containing the jt-(C3)M System... 

Olefin Complexes Containing the ir- C M System. Cyclobutadiene is the simplest example of an olefin having a tt-(C4)M system. Complexes are known in which this ring system is believed to be present, for example, tetramethylcyclobutadiene-nickel dichloride 75a) or of nickel salts 129a). No magnetic resonance data are yet available for these compounds. 

Zirconocene complexes containing two indenyl or tetrahydroindenyl groups bridged with short links such as —CH2—CH2— or —Si(CH3)— can produce isotactic polymers of higher a-olefins (32). To synthesize syndiotactic PO, bridged zirconocene complexes with rings of two different types are required, one example of which is isopropyl(cyclopentadienyl)(l-fluorenyl)zirconocene. These complexes are used for the synthesis of syndiotactic PB... 

The observation that addition of imidazoles and carboxylic acids significantly improved the epoxidation reaction resulted in the development of Mn-porphyrin complexes containing these groups covalently linked to the porphyrin platform as attached pendant arms (11) [63]. When these catalysts were employed in the epoxidation of simple olefins with hydrogen peroxide, enhanced oxidation rates were obtained in combination with perfect product selectivity (Table 6.6, Entry 3). In contrast with epoxidations catalyzed by other metals, the Mn-porphyrin system yields products with scrambled stereochemistry the epoxidation of cis-stilbene with Mn(TPP)Cl (TPP = tetraphenylporphyrin) and iodosylbenzene, for example, generated cis- and trans-stilbene oxide in a ratio of 35 65. The low stereospecificity was improved by use of heterocyclic additives such as pyridines or imidazoles. The epoxidation system, with hydrogen peroxide as terminal oxidant, was reported to be stereospecific for ris-olefins, whereas trans-olefins are poor substrates with these catalysts. 

The Chemistry of Complexes Containing 2.2 -Bipyridy 1, 1,10-Phenanthroline, or 2.2. 6. 2"-Terpyridyl as Ligands W. R. McWhinnie and J. D. Miller Olefin Complexes of the Transition Metals... 

Matsumoto et al. reported some reactions of diruthenium complexes containing a bridging disulfide ligand with unsaturated compounds such as olefins and ketones [135]. These diruthenium complexes show unique reactivities towards double-bond systems since the S-S bond has some double bond character from the contribution of the canonical structure B in Scheme 36. 

For catalysis by Pt(II) and Rh(I) w-olefin complexes (those containing chelating diolefin ligands were less effective), three types of reaction have been observed depending on the nature of the silane (55). 

Other substituted olefins such as acrylonitrile, fumaronitrile, crotono-nitrile, cinnamonitrile, and diethylfumarate also formed adducts with Co (DMG)2 complexes containing py, H2O, or PBuj and, in one case, with [Co (DMG-BF2)2py]. Second-order rate constants were reported for the formation of several Tr-olefin-Co(I) complexes from organocobalt(III) complexes containing, for example, NCCH2CH2- with DMG, DPG, DMG-BF, py, H2O, and PBuj. 

Volume 1, Metal Complexes. Describes the organopalladium complexes containing Pd—C a bonds, hydrides, olefins and acetylenes, dienes, w-allylic groups, cyclopentadienyls, and benzenes. 

A family of cyclopentadiene(Cp)-containing iron-olefin complexes has been pioneered by Jonas [13-15]. The complexes 38-40 (Scheme 7) can be obtained in a large scale from ferrocene 37 under reducing conditions in the presence of suitable coordinating olefins. Complex 38 is a highly air-sensitive, crystalline material, whereas complexes 39 and 40 are more robust due to their cyclooctadiene (cod)... 

Olefin dimerisation with Ni-NHC complexes became a topic of interest following reports of Ni(II) phosphine complexes being employed in imidazolium-based ionic liquid solvents [23, 24]. It had previonsly been established that aIkyl-Ni(II) complexes containing NHC ligands can rapidly decompose via imidazolium formation (Scheme 4.1) [5], and it was thus of interest to explore the effect that an excess of the imidazolinm cation would have on this reaction. 

Scheme 8.18 Hydrogenations of olefins with iridium complexes containing dithio-ether ligands with a pyrrolidine backbone.

The first examples of highly active olefin polymerization catalysts based on late transition metals were nickel and palladium complexes containing bulky diimine ligands.310 312 For example, complex (120) was found to polymerize ethylene with an activity of ll,000gmmol h bar A range of PE materials with molecular weights up to 106 and... 

In the case of other Group 6 metals, the polymerization of olefins has attracted little attention. Some molybdenum(VI) and tungsten(VI) complexes containing bulky imido- and alkoxo-ligands have been mainly used for metathesis reactions and the ring-opening metathesis polymerization (ROMP) of norbornene or related olefins [266-268]. Tris(butadiene) complexes of molybdenum ) and tungsten(O) are air-stable and sublimable above 100°C [269,270]. At elevated temperature, they showed catalytic activity for the polymerization of ethylene [271]. 

We have not yet addressed the important topic of absorption by the ligands in complexes. For many types of complexes, this type of spectral study (usually infrared spectroscopy) yields useful information regarding the structure and details of the bonding in the complexes. This topic will be discussed later in connection with several types of complexes containing specific ligands (e.g., CO, CN-, N02-, and olefins). 

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