Nickelacycle carboxylate

Scheme 5.5 shows two possible ways through which a nickelacycle carboxylate may, in principle, further react, once formed. Formation of p-Iactone, which may... 

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. 

The reaction also proceeds with P.y-unsaturated carboxylic acids and nickel(O) complexes to yield six-membered ring nickelacycles 28, which after coordination with a bidentate ligand afford the ring-contracted metallacycles 29 (Eq. 2-Cyclopentencarboxylic acid reacts by... 

The formation of nickelacycles from a,3 unsaturated carboxylic acids or amides can be rationalized as shown in Scheme 8. Thus, formation of nickelacycles from carboxylic acids or amides proceed by oxidative addition of the polar followed by insertion of the alkene into the... 

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-... 

Insertion of carbon dioxide is also possible. For example, seven-mem-bered ring nickelacycle 11, derived from 1,3-butadiene, undergoes further carboxylation in the presence of pyridine to form a nickel(II) dicarboxylate complex 48, which yields a diester after treatment with methanol under acidic conditions (Eq. 20). ° Similar results are obtained in the carboxylation of (r) -diene)iron(0) complexes. ... 

Carboxylation of five-membered ring nickelacycles 45 and 46 is less straightforward (Scheme 14). Reaction of the nickelacycles with carbon dioxide proceeds in the presence of pyridine to form 1,1-dicarboxyxlic acid, instead of the expected l,2-derivatives. ... 

Under milder conditions, and with the right choice of ligands, nickelacycles 4,288 can be isolated that may correspond to intermediates in the decarbonylation-decarboxylation reaction, and are related to carboxylation products (see Scheme 4.93). The alkyl carbon-nickel bond in these complexes can be intercepted by both alkyl halides (Scheme 4.100)," and organometallic species (Scheme 4.101). ... 

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