Nickelacycle preparation

Very recently, an oxanickelacyclopropane, synthesized by a Wittig reaction on coordinated is the smallest nickelacycle prepared. 

Although the carbonylation reactions of nickelacycles prepared from cyclic anhydrides is of no synthetic interest, the corresponding reactions of metallacycles synthesized from unsaturated carboxylic acids or alke-... 

The advantage of using a sacrificial anode has been clearly pointed out. Magnesium was found to be the most convenient, the oxidation of which produces Mg ions which can enter the catalytic cycle to cleave the nickela-cycle intermediate and liberate Ni for further catalytic cycles (Scheme 7). Such a mechanism has been substantiated on the basis of the formation of the nickelacycle and its characterization by cyclic voltammetry. In the absence of Mg (reactions conducted in a divided cell in the presence of ammonium ions) the nickelacycle does not transform and the reaction stops when all the starting nickel compound has been reacted. Upon addition of MgBr2 to an electrochemically prepared solution of the nickelacycle, Ni(II) is recovered [114]. 

The reaction of (methyl acrylate)bis(triphenylphosphane)nickel (34) with 3,3-dimethylcyclo-propene provides the orange, crystalline nickelacycle, methyl 6,6-dimethyl-2-nickela-2-(triphenylphosphane)bicyclo[3.1.0]hexane-3-e c/o-carboxylate (35), in 65% yield.The same complex 35 can also be prepared in 74% yield from the reaction of the cyclopropene with (cyclododeca-l,5,9-triene)nickel and triphenylphosphane. Treatment of 35 with 1,2-bis(dimethylphosphino)ethane affords derivative 36 in 88% yield as yellow-orange crystals. 

Preparation of Five-Membered Nickelacycles of N-Donor Ligands by Activation of C-XBonds (X=F, Cl, orBr). X-ray Crystal Structure of [NiBr 2-(CH=NCH2Ph) C6H4 (2,4,6-Me3C5H2N)]... 

Maleic anhydride acts as a r) -ligand with nickel(O) complexes and does not yield any nickelacycle. On the other hand, itaconic anhydride furnishes nickelacycle 8 in low yield, along with the Ti -complex 9, isolated as the major product. Complex 8 is also prepared by an alternative route based on the oxidative cycloaddition of carbon dioxide and allene. ... 

The analogous sulfur nickelacycles are prepared by an entirely different method. Thus, the oxidative addition of ethylene sulfide to a nickel(O) complex, formed in situ from 41 by reductive elimination of butane, gives thianickelacycle 42 (Scheme 11). Similarly, the oxidative addition of the four-membered heterocycle thietane with Ni(COD)bpy leads to five-membered ring complex 43. ... 

The carbonylation of nickelacycles proceeds readily at room temperature to give the corresponding cyclic anhydride by reductive elimination. For example, nickelacycle 44, prepared by oxidative addition of the corresponding cyclic anhydride and decarbonylation, regenerates the starting material after treatment with carbon monoxide (Scheme 12). Acid hydrolysis of the reaction mixtures allows the formation of dicar-boxylic acids, as illustrated for nickelacycles 30,45, and 46 (Scheme 12). 

Insertion of alkynes also takes place with unsaturated azanickelacycles. As shown in Scheme 17, nickelacycle 54, prepared at 45% yield, reacts with diphenylacetylene to form 55, which reductively eliminates to form the heterocycle (Scheme 17). The process allows synthesizing substituted 2-pyridones, although the yields are rather Better... 

As shown throughout this article, nickelacycles of general structure 1 can be prepared in a number of ways, mainly by oxidative addition to cyclic anhydrides followed by decarbonylation and by oxidative coupling of CO2/RNCO with alkenes and alkynes. These oxa- and azanickelacycles react by -elimination, oxidation, insertion, and alkylation reactions. Although most of the chemistry uncovered so far requires stoichiometric... 

A. Preparation of Nickelacycles ( )-4-(2,9-Dime yl-1,10-phenanthrolinenickela)-2-phthalimidobutyrolactone (66) and ( )-4-[(1,2-bis(diphenylphosphino)ethane)-nickela]2-phthalimidobutyrolactone (67)... 

While Ni(cod)2 In hydrocarbon solvents trimerises diphenyl acetylene, THF slows the reaction down and allows the interception of intermediates including the nickelacycle L2M1Ci,Phj,.150 The complex L2N1H(BHi,) or catalysts prepared in situ from Ni(II), L and NaBH (L PCy3) are highly active In the cyclotrlmerlsatlon of Me0( 2CECCH20Me. Substrate purity Is of prime... 

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