Chromium complexes butadiene

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

Typical TLC data (silica gel, 6 1 hexanesiethyl acetate) include R - 0.61 (1-acetoxy-1,3-butadiene) 0.51, a red spot [tricarbonyl(cycloheptatriene)chromium] 0.45 a yellow spot (side product that often overlaps with the starting complex) and 0.31 a yellow spot (main intermediate chromium complex). 

M. 1-Aza-t,3-butadiene Complexes via 1,4- and N-Atkenyl(amino)carbene Chromium Complexes via 1,5 Hydrogen Shifts... 

The isolation of [Py2 DMF-RhCl2 (BFi,) ], a highly active chloroform-soluble catalyst which gives the same product stereochemistry observed in heterogenous hydrogenation, has been described. The stereoselective addition of Hj or D2 to 1,3-butadiene systems can be induced with a tricarbonyl chromium complex. ... 

Electronically rich 1,3-butadienes such as Danishefsky s diene react with chromium alkenylcarbene complexes affording seven-membered rings in a formal [4S+3C] cycloaddition process [73a, 95a]. It is important to remark on the role played by the metal in this reaction as the analogous tungsten carbene complexes lead to [4S+2C] cycloadducts (see Sect. 2.9.1.1). Formation of the seven-membered ring is explained by an initial cyclopropanation of the most electron-rich double bond of the diene followed by a Cope rearrangement of the formed divinylcyclopropane (Scheme 65). Amino-substituted 1,3-butadienes also react with chromium alkenylcarbene complexes to produce the corre-... 

Carboxylic acids, a-bromination of 55, 31 CARBOXYLIC ACID CHLORIDES, ketones from, 55, 122 CARBYLAMINE REACTION, 55, 96 Ceric ammonium nitrate [Ammonium hexa mtrocerate(IV)[, 55, 43 Chlorine, 55, 33, 35, 63 CHROMIUM TRIOXIDE-PYRIDINE COMPLEX, preparation in situ, 55, 84 Cinnamomtnle, a-phenyl- [2-Propeneni-tnle 2,3-diphenyl-], 55, 92 Copper(l) iodide, 55, 105, 123, 124 Copper thiophenoxide [Benzenethiol, copper(I) salt], 55, 123 CYCLIZATION, free radical, 55, 57 CYCLOBUTADIENE, 55, 43 Cyclobutadieneiron tricarbonyl [Iron, tn-carbonyl(r)4-l,3-cyclo-butadiene)-], 55,43... 

The first example of a 1,3-dienetetracarbonylchromium complex, butadienetetracarbonylchromium, has been prepared by condensing chromium atoms with butadiene and subsequent treatment with CO. The compound has been characterized by mass, i.r., and n.m.r. spectral studies." ... 

Geminal dibromocyclopropanes have been reduced by chromium(lI) - (-i-)-tartrate complex and by butyllithium - (+)-sparteine complex to give cyclic allenes and 1-phenyl-l,2-butadiene with very low enantioselectivity (< 1 % op)122. In addition, cyclic diallenes of unknown optical purity have been reported123, l24, e.g., 3,4,9,10-cyclododecatetraene-l,7-dione is prepared using a stoichiometric amount of methyllithium and a sixfold excess of (-)-sparteine123,124. 

Chromium atoms also react with butadiene to give a product that yields predominately d2-but-l-ene together with cis- and trans-d2-but-2-ene on deuterolysis. This can also be interpreted in terms of cr-bonded organo-metallic products. However, it is also possible to isolate a 7r-complex of butadiene by ligand stabilization of the low-temperature condensate (115, 138, 140) ... 

Unlike the chromium-butadiene reaction, the vapors of both molybdenum and tungsten afford thermally stable 7r-complexes that are air-stable, white crystalline solids (114) ... 

The tris-allyl complex, in each case, produced a 1.2 growth step of the butadiene molecule. With the more anionic (or less cationic) cobalt salt, the growth occured to only the dimer before it underwent anionic hydride chain transfer. With less anionic chromium the 1.2 chain growth continued on the produce polymer. 

Upon UV irradiation in hydrocarbon solution, the hexacarbonyls of chromium, molybdenum, and tungsten react differently with conjugated dienes like 1,3-butadiene (la), ( )-l,3-pentadiene (lb), 2-methyl-1,3-butadiene (lc), ( , )-2,4-hexadiene (Id), ( )-2-methyl-l,3-pentadiene (le), 2-ethyl-1,3-butadiene (If), or 1,3-cyclohexadiene (Ig). Chromium hexacarbonyl (2) yields, with the acyclic dienes la-lf, tetracarbonyl-r/2-dienechromium(0) complexes (3a-3f) in a smooth reaction (8-10). With 1,3-cyclohexadiene, in addition to 3g, dicarbonylbis(>/4-l,3-cyclohexadiene)chromium(0) (4g) is obtained [Eqs. (7) and (8)j. During chromatography on silica gel, the 1,3-cyclohexadiene complex 3g dismutates readily to [Cr(CO)6] and 4g [Eq. (9)]. Under the same conditions with 2 1,3-cyclopentadiene (lh) yields, in a hydrogen-transfer reaction, the stable dicarbonyl- / 5-cyclopentadienyl-r/ 3-cyclopent-enylchromium (5) (11-13) [Eq. (10)]. 

Chromium compounds of this type feature one to four carbonyls and one or more ancillary ligands, as seen, for example, in ( -C5H5)Cr(CO)2( -allyl). A general synthesis for allyl complexes of this type, including the aforementioned parent complex has just been published. Alternatively, the reaction of butadiene with [( -C5H5)Cr(CO)3]2 in the presence of mercury yields the crotyl derivative in... 

Molecular oxygen has become a commonly used co-catalyst for inactive or weakly active transition metal complexes [1-5]. In addition, other oxidizing agents, mainly peroxides, have recently been used in active rhodium complexes in particular, but also in metal carbonyls, as catalysts for hydrosilylation. The catalytic activity of bis(triphenylphosphine)carbonylrhodium(I) in the hydrosilylation of C=C and C=0 bonds can be much increased by the addition of about a 50 % molar excess of tert-butyl hydroperoxide [100]. Chromium triad carbonyls M(CO)e, where M = Cr, Mo, W, have been tested to examine the effect of various organic peroxides on the hydrosilylation of 2,3-dimethyl-1,3-butadiene by triethyl-, triethoxy- and methyldiethoxysilanes [100]. The evidence for organic oxidant promotion of RhCl(cod)phosphine-catalyzed hydrosilylation of 1-hexene was demonstrated previously [101]. 

Chromium atoms have also been observed [386] to trimerize acetylenes to benzenes, isomerize but-l-ene to a mixture of but-2-enes and form complexes with 1,3-butadiene and propene. 

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