Ligand Exchange with Nickel-Alkene Complexes

Ligand Exchange with NIckel-Alkene Complexes 

Acetylene (50 mL, 6 mmol) was added at -50 °C without stirring to an Et20 soln (40 mL) of [Ni(C2H4)2(PCy3)] (5.0 mmol) [prepared from Ni(cdt) (1.165 g, 5.0 mmol Ni), ethene, and CyjP (1.40 g, 5.0 mmol)]. The color of the yellow soln changed to light red, and at -78 °C over the course of 2 d small yellow crystals formed. The mother liquor was decanted, and the crystals were washed with cold Et20 (2 x) and dried in vacuo at -30 °C to afford 48 yield 1.62 g (82%). 

PhC=CTMS (810 mg, 4.66 mmol) was added at 20 °C to the light yellow soln of 49 (610 mg, 2.33 mmol) in pentane (10 mL). Upon heating the mixture for a short period to 45 °C the color turned intense red. Cooling to -78 °C afforded red cubes which were separated from the mother liquor using a capillary frit, washed with cold pentane (2 x), and dried in vacuo at 20 °C to afford 50 5deld 960 mg (80%). 

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Ligand Exchange with NIckel-Alkene Complexes... 

Occasionally, however, isolable methylenecyclopropane complexes are observed, from which the ligands are released unaffected via ligand exchange. Thus (methylenecyclopropane)-bis(triphenylphosphane)nickel (2), a complex catalyzing methylenecyclopropane oligomerization, was prepared by two different routes the methylenecyclopropane ligand was released on treatment with various alkenes. Similar complexations and decomplexations were observed with methyl-substituted methylenecyclopropanes. ... 

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