Iron porphryin complexes are active catalysts for the cyclopropanation of alkenes by ethyl diazoacetate. Fe(TIP) (TIP = meso-tetra-p-tolylporphyrin), an isolated iron(II) porphyrin complex, can be used as the catalyst, or the iron(III) complexes of several porphyrins can be reduced in situ. The reactions produce synthetically useful excesses of the trans cyclopropyl ester products. This stereoselectivity exhibits a modest solvent dependence, with donor solvents giving higher ratios of the trans cyclopropane products. The diastereoselectivity exhibits only a modest dependence on the steric bulk of the porphyrin. The reactions are selective for 1-alkenes and 1, 1-disubstituted alkenes. Conjugated substrates and enol ethers react more rapidly than simple aliphatic alkenes. A mechanistic model for the iron-mediated reactions is proposed which is consistent with the data presented herein. Disciplines Chemistry CommentsReprinted (adapted) Am. Chern. Soc. 1995, 117, 9194-9199 Shape Abstract: Iron porphryin complexes are active catalysts for the cyclopropanation of alkenes by ethyl diazoacetate. Fe(TIP) (TIP = meso-tetra-p-tolylporphyrin), an isolated iron(II) porphyrin complex, can be used as the catalyst, or the iron(III) complexes of several porphyrins can be reduced in situ. The reactions produce synthetically useful excesses of the trans cyclopropyl ester products. This stereoselectivity exhibits a modest solvent dependence, with donor solvents giving higher ratios of the trans cyclopropane products. The diastereoselectivity exhibits only a modest dependence on the steric bulk of the porphyrin. The reactions are selective for 1-alkenes and 1, 1-disubstituted alkenes. Conjugated substrates and enol ethers react more rapidly than simple aliphatic alkenes. A mechanistic model for the iron-mediated reactions is proposed which is consistent with the data presented herein.The metal-catalyzed cyclopropanation of substituted olefins by diazo esters is a reaction commonly employed in organic synthesis. 1 Chiral copper 2 -4 and rhodium 5 • 6 catalysts have recently been reported to effect cyclopropanation with high enantioselectivity. However, the diastereoselectivities obtained in these reactions are generally poor. Mixtures of the trans and cis cyclopropyl esters are produced, with the trans isomer obtained in only a slight excess. A notable exception is a recently reported ruthenium catalyst/ which provided high enantioselectivities and trans/cis ratios of 10:1 using ethyl diazoacetate (EDA) as the carbene source.We are interested in the development of metalloporphyrin cyclopropanation catalysts, since such reactions often exhibit unique stereoselectivities and exceedingly high catalyst turnover numbers. For example, rhodium(III) porphyrin-catalyzed cyclopropanation reactions using EDA as the carbene source produced the cis cyclopropyl ester as the major product when bulky ligands such as the tetramesitylporphyrin (TMP) (see Figure 1) were employed. 8 -11 To the best of our knowledge, this is the only exampl...

London forces are omnipresent in nature and relevant to molecular engineering. Proper tuning of their energetic contribution may stabilize molecular aggregates, which would be otherwise highly unstable by virtue of other overwhelming repulsive terms. The literature contains a number of such noncovalently bonded molecular aggregates, of which the "binding mode" has never been thoroughly settled. Among those are the emblematic cationic complexes of tetrakis(isonitrile)rhodium(I) studied by a number of researchers. The propensity of these complexes to spontaneously produce oligomers has been an "open case" for years. For the dimer [(PhNC)(4)Rh](2)(2+), one of the archetypes of such oligomers, density functional theory methods (DFT-D3) and wave function based spin-component-scaled second-order Møller-Plesset perturbation theory (SCS-MP2) quantum chemical calculations indicate that when the eight isonitrile ligands arrange spatially in an optimal π-stacked fashion, the energy due to dispersion not only overcomes coulombic repulsion but also the entropy penalty of complex formation. This central role of long-range electron correlation explains such cation-cation attractive interactions. Furthermore, the present findings relativize the role of the metal-metal "d(8)-d(8)" interactions, which are present on a relatively small scale compared to the effects of the ligands; d(8)-d(8) interactions represent about 10-15% of the total dispersion contribution to the binding energy.

The syntheses of cycloruthenated compounds by several methods, and especially by the C-H activation pathway, have been reviewed. Many ruthenium-containing starting materials lead to these interesting organometallic compounds, which have found various applications in different fields of chemistry. Their reactivity highlights both the variety of reactions that were found to occur at the Ru-C bonds as well as the inertness of the organometallic moiety when these species are exposed to strongly oxidizing molecules or to reactive halogenation reagents. Their use as catalyst precursors showed them to be particularly efficient for hydrogenation reactions, either by H 2 or by hydride transfer.