Phosphine alkenes

A number of X-ray crystal structures of nickel(O) complexes containing both alkenes and phosphines have been reported to date with the aim of gaining more information on the bonding in metal alkene complexes. Structural data for the most relevant nickel(O) phosphine alkene complexes are reported in Table 9. 

Table 9 Structural Data for some Nickel(0) Phosphine Alkene Mixed Complexes and Related...

Dialkyl(trimethylsilyl)phosphines, alkene additions, 10, 780 Dialky lzincs... 

Chiral phosphine-alkene (201) has been designed as a novel bidentate ligand for the rhodium-catalysed asymmetric 1,4-addition of aryl boronic acids to maleimides,... 

Another argument against the oxo-transfer mechanism in our catalytic aerobic oxidation protocol is the lack of formation of sulfoxides from sulfides, N-oxydes from amines and phosphine oxydes from phosphines. Alkenes also proved to be inert towards oxidation no epoxide formation could be detected under our reaction conditions. 

In reactions requiring palladium 0), formation of the active complex may be achieved more conveniently by reduction of a palladium(ll) complex, for example, Pd 0Ac)2- Any phdsphine may then be used in the reaction, without the need to synthesize and isolate the corresponding palladium 0)-phosphine complex. Only 2-3 equivalents of phosphine may be needed, making the palladium(O) complex coordinatively unsaturated and therefore very reactive. The reduction of palladium li)to palladium(o) can be achieved with amines, phosphines, alkenes, and organometailics such as DIBAL-H, butyl lithium, or trialkyl aluminium. The mechanisms are worth giving as they illustrate the basic steps of organometallic chemistry. 

There is an extensive Co1 chemisty of monocyclopentadienyl compounds, of which CpCo(CO)2 is one example. The CO may be replaced by phosphines, alkenes, isocyanides, and so on. The dicarbonyl itself can be reduced to a radical ion that contains cobalt in the formal oxidation state 0.5, and can be isolated as its (Ph P)2N+ salt ... 

To complete the alkene hydrogenation reaction sequence, the first hydrogen transfer must be followed by a second, which results in the reductive elimination of the alkane product. This proceeds through a three-centered transition state. The catalytic cycle is shown in Fig. 22-1 but the process is actually more complicated since the equilibria are dependent on phosphine, alkene, rhodium concentrations, temperature, and pressure. 

Carbonyl, Phosphine, Alkene, and Alkyne Complexes with jr-Ligands 2... 

Phosphines add to alkenes to give alkyl phosphines and to alkynes to give vinyl phosphines. In the presence of an ytterbium (Yb) catalyst, diphenylphosphine added to diphenyl acetylene to give the corresponding vinyl phosphine. A palladium catalyst was used for the addition o-diphenylphosphine to terminal alkynes, giving the anti-Markovnikov vinyl phosphine but a nickel catalyst led to the Markovnikov vinyl phosphine.Alkenes also react with diarylphosphines... 

Structure-property relationship studies of bidentate phosphine-alkene ligands in the catalytic arylation of heterocycles were pursued with the synthesis of a... 

The mechanism for heterocycle arylation is likely analogous to that postulated with monodentate trialky lphosphine ligands (Scheme 18). The higher reactivity and extended catalyst lifetime observed with bidentate phosphine-alkene ligand might... 

CARBONYL, PHOSPHINE, ALKENE, AND ALKYNE COMPLEXES WITH rr-LIGANDS... 

An interesting, but hitherto widely neglected feature of CO2 in this context is its ability to chemically interact with metal-oxygen complexes, leading to transition metal peroxocarbonates [4,82]. These complexes are able to transfer one oxygen atom to oxophiles such as phosphines, alkenes and active methylene... 

Scheme 22 Phosphine/alkene-mediated one-pot Wittig reaction...

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