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The complex [OsTp(kappa(1)-OCMe)(2)(P(i)Pr(3))]BF(4) [Tp = hydridotris(pyrazolyl)borate] promotes the cleavage of both C(sp(3))-C(sp(2)) bonds of benzylidenecyclopropane and 3-phenylpropylidenecyclopropane to yield the complexes [OsTp(=C=CHR)(eta(2)-CH(2)=CH(2))(P(i)Pr(3))]BF(4) (R = Ph, CH(2)CH(2)Ph). The process is proposed to take place via metallacyclopropene intermediates stabilized by an ethylene chelation assistant. The driving force for the fragmentation is the high stability of the resulting ethylene-Os-vinylidene species.

Thecomplex [OsCp{κ3-P,C,C-PiPr2[C(CH3)CH2]}(CH3CN)]PF6(1) reactswith (2-pyridyl)methylenecyclopropane, at room temperature, to giveinitially the cyclobutylidene derivative [Os(η5-C5H5)(CCH2CH2CH-o-C5H4N){PiPr2[C(Me)CH2]}]PF6(2), as a result of the ring expansionof the alkylidenecyclopropane unit. Over time complex 2rearranges into the cyclobutene derivative [Os(η5-C5H5){η2-C(CHCH2CH2)-o-C5H4N}{PiPr2[C(Me)CH2]}]PF6(3). The reaction of 1with (2-pyridyl)methylenecyclopropane at room temperaturealso affords the phosphinomethanide metallacycle [Os(η5-C5H5){κ4-P,Ca,Cb,N-PiPr2[Ca(Me)CH2CH)(CbCH2CH2-o-C5H4N]}]PF6(4) as a minor product, which becomes the major product of the reactionat 45 °C. This osmacyclopentane results from the C–C couplingof the isopropenyl substituent of the phosphine ligand and the organicsubstrate. In acetone at 75 °C, the reaction of 1with (2-pyridyl)methylenecyclopropane leads to the 2-alkylidene-1-osmacyclobutane[Os(η5-C5H5){κ3-N,Ca,Cb-Ca(CH2CbH2)(CH-o-C5H4N)}{PiPr2[C(Me)CH2]}]PF6(5), as a consequence of the oxidative addition ofone of the C(sp2)–C(sp3) bonds of thecyclopropane unit of the substrate to the osmium atom, along with 6, a diastereomer of 4. Complexes 3–5have been characterized by X-ray diffractionanalysis. DFT calculations suggest that all of the reaction productsare derived from a common key 1-osma-2-azacyclopent-3-ene intermediate(D). [ABSTRACT FROM AUTHOR]

The article focuses on the potential applications of the cleavage of C-C bonds with the help of transition-metal complexes in organic synthesis, as well as petroleum and pharmaceutical research. It says that alkylidenecyclopropanes containing C=C bond at the olefinic moiety's terminal carbon undergo Os-promoted ring expansion. It cites that absence of coordination auxiliary can be cracked to ethylene and vinylidene units under very mild conditions to form ethylene-osmium-vinylidene complexes.

The article focuses on the formation of cyclobutylidine complexes from osmium and ruthenium through the ring expansion of alkylidenecyclopropanes. It mentions that new reaction transition pattern of metal complexes and alkylidenecyclopropane formed the derivatives of cyclobutylidene. It concludes that alkalidenecyclopropanes that contains chelation assistant undergo ring expansion to afford cyclobutylidene derivatives.