Facile C–C bond cleavage of β-diketones by tin(IV) porphyrin complex

Reactions of trans-dihydroxo(meso-tetraphenylporphyrinato)tin(IV) [Sn(TPP)(OH)2] with β-diketones such as acetylacetone (1), dibenzoylmethane (2), 1-phenylbutane-1,3-dione (3), or 4,4-dimethyl-1-phenylpentane-1,3-dione (4) were studied. All reactions afforded dicarboxylato tin(IV) porphyrin complexes [Sn(TPP)(O2CR)2] (R = Me, Ph, t-Bu) and ketonic compounds due to the C–C bond cleavage of β-diketones. The products were characterized by 1H NMR spectroscopy and ESI mass spectrometry, and further proved by X-ray crystallographic analysis of Sn(TPP)(O2CCH3)2. Possible reaction mechanisms involving four-centered intermediate species are discussed, in which the C–C and O–H bonds are cleaved along with the simultaneous formation of (Sn)O–C and H–C bonds.