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The reactions of the nickel(0) complex [Ni(bipy)(COD)] (COD = cyclooctadiene, bipy = 2,2‘-bipyridine) with isoprene (ip) in the absence and presence of carbon dioxide were investigated. A detailed kinetic analysis revealed that [Ni(bipy)(COD)] reacts reversible with ip and activation parameters for the forward and back reactions were calculated from a temperature dependence study to be the following: ΔH⧧ = 35 ± 5 kJ/mol, ΔS⧧ = −79 ± 16 J/(mol K) forward reaction (ip dependence); ΔH⧧ = 58 ± 2 kJ/mol, ΔS⧧ = 58 ± 10 J/(mol K) back-reaction (COD dependence at low temperatures). It could be shown that CO2 did not react with [Ni(bipy)(COD)] directly but with the nickel ip complex to form the product complex ((3−5-η3)-3-methyl-3-pentenylato)nickel bipyridine. The reaction proceeded in an associative way, during which CO2 was inserted into a Ni−C bond in an oxidative coupling step. The activation parameters were calculated to be ΔH⧧ = 25 ± 7 kJ/mol and ΔS⧧ = − 184 ± 24 J/(mol K).

The reactions of the nickel(0) complex [Ni(bipy)(COD)] (COD = cyclooctadiene, bipy = 2,2‘-bipyridine) with benzaldehyde, propionaldehyde, and carbon dioxide/propionaldehyde were investigated. A detailed kinetic analysis revealed that [Ni(bipy)(COD)] reacts reversible with aldehydes and activation parameters for the forward and back reactions were calculated from a temperature dependence study: forward reaction (benzaldehyde) ΔH⧧ = 47.8 ± 0.4 kJ/mol, ΔS⧧ = −47 ± 1 J/(mol K); back reaction (COD) ΔH⧧ = 45 ± 6 kJ/mol, ΔS⧧ = −61 ± 19 J/(mol K) and forward reaction (propionaldehyde) ΔH⧧ = 55 ± 3 kJ/mol, ΔS⧧ = −58 ± 9.0 J/(mol K); back reaction (COD) ΔH⧧ = 39 ± 0.5 kJ/mol, ΔS⧧ = −58 ± 2 J/(mol K). It could be shown that carbon dioxide did not react with [Ni(bipy)(COD)] directly but with the nickel propionaldehyde complex to form a five-membered cyclic nickel complex. The reaction proceeded according to an associative mechanism, during which the carbon dioxide was inserted into a Ni−O bond by an oxidative coupli...