Metallacyclobutanes thermolysis

Reductive elimination of metallacyclobutanes results in the formation of cyclopropanes recent examples are compiled in Table 8. Cyclopropane formation is observed throughout the transition series, typically induced by thermolysis or oxidation, depending on the metal. 

Titanocene methylidene phosphine complexes Cp2Ti= CH2L (L = PMes, PMe2Ph, PEts) have been generated by the thermolysis of titanocene metallacyclobutanes in the presence of excess phosphine (equation 9). These titanocene methylidene phosphine complexes have been found to react with alkenes, alkynes, and CO to form metallacyclobutanes, metallacyclobutenes, and a ketene complex, respectively. The phosphine ligand is labile, and an equilibrium mixture is rapidly established if a second phosphine is added. ... 

Some rare cases of cyclopropane formation from metallacycles other than metallacyclobutanes have been reported. Thus thermolysis of a rhenacyclopentane 3, obtained from CpRe(CO)2H2 (1) and 1,4-diiodobutane (2), yields methylcyclopropane (4) in near quantitative yield. Based... 

Thermolysis of the amides Cp2Zr(THF)(=NBu ) in benzene at 85°C affords the aryl complex Cp2ZrPh(NHBu ) and THF. The reaction between various complexes Cp2ZrL(=NR) (R = Bu , C6H3Mb2-2,6) and alkynes R OCR affords the metallacycles Cp r C(R2)=C(R )-NR). Some alkenes behave in similar fashion to form metallacyclobutanes. The reaction between NCC6H4CN and Cp2Zr(butadiene) is sensitive to conditions. Addition of the nitrile to the zirconium reagent results in complex 36. ... 

Generation of the 16-electron fragment Tp Rh(CNCH2CMe3) (Tp =[HB(3,5-dimethylpyrazolyl)3]) t> the presence of cyclopropane resulted in C-H activation of the hydrocarbon. The cyclopropyl hydride complex rearranged in benzene solvent to the metallacyclobutane complex Tp Rh(CNCH2CMe3)(CH2CH2CH2). Thermolysis of the rhodacyclobutane complex produced an 77 -propylene complex (Scheme 38). ... 

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