Alkenes 1,3-diketone metal complexes

Another area where metal /3-diketonates have made a significant impact is in the oxidation of aLkanes , alkenes and alcohols A number of different metal complexes have been used in these reactions, including Pd(acac)2 (29) , Co(acac)3 (30) , Fe(acac)3 (31), a bimetallic Pd(II) complex containing a 1,3,5-triketone ligand, MCI (acac)(PPh3) (32) where M = Ni, Co, Cu, Mn(acac)3 (33) , Mo02(acac)2 (34) , VO (acac)2 (35) and VO(hfac)2 (36) . In the latter study, the oxidation of a-acetylenic... 

Chloro(methoxy)- and chloro(phenoxy)carbenes, which are generated from the diazirine precursors, behave as ambiphiles in additions to alkenes, exhibiting high reactivities toward both electron-poor and electron-rich olefins. Methoxy(phenyl)- and ferrocenyl(methoxy)methylenes have been transferred in a stereospecific manner from transition metal complexes of these species to electron-deficient alkenes. Irradiation of benzocyclobutanedione with UV light induces a rearrangement of the cyclic a-diketone to 17, which has been trapped by alkenes in good yields " . Thermolysis of 18 gives rise to nucleophilic dimethoxycarbene, which has been intercepted by electron-deficient olefins or by styrene derivatives. 

The reaction occurs with some enantioselectivity and requires the presence of pivaldehyde (which is also oxidized)29,30. The reaction occurs for many other alkenes using transition metals coordinated to 1,3-diketone type ligands31-34. Use of a cobalt(II) complex and aldoacetal in place of the Mn(III) compound and pivaldehyde gives a novel method for the synthesis of acid-sensitive epoxides35. 

B. B. Wentzel, P. A. Gosling, M. C. Feiters, R. J. M. Nolte, Mechanistic studies on the epoxidation of alkenes with molecular oxygen and aldehydes catalysed by transition metal—diketonate complexes,/. Chem. Soc. Dalton Trans. (1998) 2241. 

The direct resolution of underivatised enantiomers has been effected with the aid of some metal-containing chiral stationary phases. Particular attention has been paid to the resolution of chiral alkenes and epoxides using stationary phases derived from chiral metal chelate complexes. The rhodium dicarbonyl P-diketonate complex (5), when dissolved in squalene and coated onto a capillary column, permitted the quantitative enantiomer resolution of 3-methylcyclopentene while methyl oxirane was similarly resolved... 

One of the most interesting arylcopper(I) compounds is mesitylcopper(I), which is a pentamer in the solid state and a tetramer in the presence of S-ligands. It has recently been shown to split dioxygen, and is highlighted here because it is prepared from CuCl. Hexafluoroacetylacetonatocopper(I)-alkyne complexes (prepared from CuCl) have been shown to be useful in the chemical vapor deposition of Cu metal. ( )-l-TrimethylsUyl-l-alkenes have been prepared in high yields by the CuCl-catalyzed decomposition of a-trimethylsilyldiazoalkanes. Finally, Indian chemists have shown that 1,2-diketones are produced in good yield when Na(RCO)Fe(CO)4 is treated with CuCl. ... 

The nickel acylate complex [Ni( 0)3 = (Bu)OLi ] reacts with mono- and disubstituted alkyne derivatives to afford 1,4-diketones, cyclopentenones or y-lactones, depending on the substitution pattern and the reaction time. " Nickelocene, [Ni(q - 5H5)2], reacts with 1,3-dimesitylimidazolium chloride to afford the carbene complex 63, the chloride ligand of which may be subsituted for a methyl group through further reaction with MeLi. Reduction of nickelocene with metallic sodium in the presence of either 1-pentene or 1-hexene results in alkene activation and formation of trinickel products containing p3-carbyne... 

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