Kinetics Norbomadiene

Early work established that S4N4 forms di-adducts with alkenes such as norbornene or norbomadiene. Subsequently, structural and spectroscopic studies established that cycloaddition occurs in a 1,3-S,S"-fashion. The regiochemistry of addition can be rationalized in frontier orbital terms the interaction of the alkene HOMO with the low-lying LUMO of S4N4 exerts kinetic control. Consistently, only electron-rich alkenes add to S4N4. 

Only limited data are available for the kinetics of oxo synthesis with the water-soluble catalyst HRh(CO)(TPPTS)3. The hydroformylation of 1-octene was studied in a two-phase system in presence of ethanol as a co-solvent to enhance the solubility of the olefin in the aqueous phase [115]. A rate expression was developed which was nearly identical to that of the homogeneous system, the exception being a slight correction for low hydrogen partial pressures. The lack of data is obvious and surprising at this time, when the Ruhrchemie/ Rhone-Pou-lenc process has been in operation for more than ten years [116]. Other kinetic studies on rhodium-catalyzed hydroformylation have been published, too. They involve rhodium catalysts such as [Rh(nbd)Cl]2 (nbd = norbomadiene) [117] or [Rh(SBu )(CO)P(OMe)3]2 [118], or phosphites as ligands [119, 120]. 

The photoisomerisation kinetics and other properties of the 1 1 inclusion complexes formed between aromatic derivatives of norbomadiene and P-cyclo-dextrin have been measured." (S)- or (R)-2-Chloropropiophenone affords partially racemised (S)- or (R)-2-phenylpropionic acid respectively by a photo-induced rearrangement via what is probably an ion or radieal intermediate," and (Z)-N-substituted benzoyl-a-dehydrophenylalanines such as (7) are photo-isomerised to 1-azetidine derivatives (8) by a 1,3-acyl migration. Irradiation of 9,9 -bifluorene-9,9 -diol (9) gives a mixture of fluoren-9-one and spiro[9H-fluorene-9,9 (10 -H)-phenanthren]-10 -one (10) whose composition is solvent dependent with the more polar solvents favouring (10). Laser flash photolysis shows the presence of two transients, one of which can be identified with the 9-fluorenyl cation (11), and which originates from photoheterolysis of the diol (9). There is also evidence to support the view that unimolecular rearrange-... 

A study of the temperature dependence of the NMR spectrum of a solution of norbomadiene and [(C7H8)RhCl]2 indicates the formation at low temperature of the five-coordinate rhodium complex (186) (596). The kinetics of norbomadiene exchange suggest that the slow reaction... 

Bis(c/j-l, 2-perfluoromethylethylene-l, 2-dithiolato)nickel (138) undergoes a kinetically second-order oxidative cycloaddition with norbornene and norbomadiene via a charge-separated transition state to give (139) this is a full report now amplifying the preliminary report (cf. Vol. 1, p. 155). Conjugated dienes mostly react too rapidly for kinetic study, to give, for... 

The Ni -catalysed (2+2) cycloaddition of activated olefins such as acrylonitrile or acrylic acid esters to quadricyclane which gives endo- and exo-substituted products is complicated particularly in the case of 1,2-disubstituted olefins by a competing isomerization of quadricyclane to norbornadiene. Norbomadiene gives identical cycloadducts under these conditions with a similar isomer ratio. Kinetic studies of the cycloaddition reactions of quadricyclane gave a plot of log [quadricyclane]t o/ [quadricyclane]i=t against time which exhibited a marked deviation from linearity due to the retarding effect of norbomadiene which is also formed and in turn coordinates to the Ni catalyst. Scheme 11 accounts for these observations. 

The nickel compounds NiRa(bipy) react with a variety of alkenes, including ethylene, norbomadiene, maleic anhydride, and tetracyanoethylene, to produce Ni(bipy)(alkene) or Ni(bipy)(alkene)2. A kinetic study, supported by characterization of intermediates from the reactions with aorolein and with acrylonitrile, indicates that the reaction mechanism involves the intermediacy of transient complexes NiR2(bipyXalkene), containing the alkene TT-bonded to the nickel as in the products. There is a correlation between the rates of these reactions and the stabilities of the respective complexes Ni(bipy)(alkene). The unstable species CoH(LL)2, where LL = bipy or phen, undergo substitution reactions with, for example, carbon monoxide, in which one LL ligand is replaced. One LL can also be replaced by alkyl halides here the reaction is oxidative elimination rather than simple substitution. ... 

A stopped-flow kinetic study has revealed a marked inverse kinetic isotope effect for the reduction of norbomadiene to norbornene by [Ir(PPh3)2(OCMe2)2R2] (R = H or D). The faster rate of the deuteride complex has been attributed to the large isotope ratio k-Jk-i = 5.73 0.32) in the equilibrium between 15 and 16 in equation (35) ... 

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