Unsaturated organic molecules, coupling

Silane coupling agents are generally synthesized through addition of silicon hydrides to unsaturated organic molecules ... 

The influence of the nature of the metal atom is apparent in the chemical shifts and, to a lesser degree, in the couplings within the vinyl group. The effect on shifts is greatest on the proton in the position gem to the metal, and least on the proton in the cis position. This is in accord with observations of shifts in unsaturated organic molecules in general (316). 

B. Coupling Reactions with Unsaturated Organic Molecules. 173... 

As a result of the second imine coordination occurring much more slowly than the first, the opportunity was afforded to bring about tandem couplings involving imines and additional unsaturated organic molecules. Thus, even though 29... 

In this paper we present an account of the results obtained by our group in this area. We will mainly emphasize those concerning the coordination of C02 in its intact form (Alvarez et al, 1986) as well as those leading to the coupling of this molecule with unsaturated organic substrates, in particular the metal-induced carboxylation and hydrocarboxylation of ethylene to form acrylate and propionate derivatives, respectively (Alvarez et al, 1985). 

Catalysis of the [2+2+2] cycloaddition of alkynes by transition metal complexes has been extensively exploited for the synthesis of complex organic molecules [30-34]. The accepted mechanism for this transformation, shown in Scheme 10, involves coordination of two alkyne molecules to the metal centre followed by oxidative coupling to form the coordinatively unsaturated metallocyclo-pentadiene 49, which can coordinate a third molecule of alkyne to afford 50. Insertion of the alkyne in a metal-carbon bond of this complex leads to met-allocycloheptadiene 51, and reductive elimination then affords cyclotrimer 52 and regenerates the catalytic species. Alternatively, the transformation of 49 into 52 might involve a Diels-Alder reaction giving intermediate 53, followed by reductive elimination [35]. 

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