Philip S. Skell

Electron Paramagnetic Resonance of Triplet Alternant Methylenes. Propargylene and Homologs

The electron paramagnetic resonance of a number of alternant methylene compounds has been observed, and zero‐field splitting parameters have been obtained. The results are D=0.6276±0.0002 cm−1 and E=0.0000±0.0008 cm−1 for H–↑C↑–C≡C–H,D=0.6263±0.0002 cm−1 and E=0.0000±0.0008 cm−1 for H–↑C↑–C≡C–CH3,D=0.5413±0.0004 cm−1 and E=0.0035±0.0003 cm−1 for H–↑C↑–C≡C–C6H5,D=0.6087±0.0001 cm−1 and E=0.0000±0.0004 cm−1 for H–↑C↑–C≡C–C≡C–CH3,D=0.6055±0.0001 cm−1 and E=0.0000±0.0004 cm−1 for H–↑C↑–C≡C–C≡C–C(CH3)3,D=0.5530±0.0002 cm−1 and E=0.0000±0.0006 cm−1 for H–↑C↑–C≡C–C≡C–C6H5, and D=0.8629±0.0003 cm−1 and E=0.0000±0.0010 cm−1 for H–↑C↑–C≡N. The interpretation of the data is based upon the observed spin‐density distribution in the alternant free radicals having structures similar to the above triplet molecules. Thus, propargylene, H–↑C↑–C≡C–H, is discussed in terms of a superposition of two π‐electron systems having the same spin‐density distribution as in the allyl radical. Both positive and negative triplet spin de...

Reactions of coordinated arenes: Syntheses of substituted (η5-cyclohexadienyl) (η5-cyclopentadienyl)iron(II), and (η6-arene) (η4-cyclohexadiene)iron(0) complexes

The complexes obtained from the co-deposition of iron atoms with arenes react with cyclopentadiene to give the substituted (η5-cyclohexadienyl)-(η5-cyclopentadienyl)iron(II) complexes, and with hydrogen to give the (η6-arene)(η4-cyclohexadiene)iron(0) complexes. The latter reaction was used to demonstrate that the complex obtained in the case of toluene is not a 1 : 1 adduct.

An electron paramagnetic resonance study of methylene

The present paper is a detailed account of the study of the methylene molecule trapped in matrices at 4.2 °K by electron paramagnetic resonance spectroscopy. The methylene is generated by photolysis of its diazirine precursor dissolved in the matrix material. Besides verifying that the methylene ground electronic state was a spin triplet, the first observation of the EPR spectrum revealed that the molecule was nonlinear. Through assumptions concerning the amounts of spectral averaging owing to molecular motion and the relationship of the zero‐field splitting parameters D and E with each other through an s–p hybrid model of the electronic structure, other workers showed the bond angle to be substantially bent. This was later confirmed by ourselves and others with a measurement of the isotropic carbon‐13 hyperfine interaction. Using 90.5% carbon‐13 enrichment in the present work, a more precise determination of the isotropic carbon‐13 hyperfine interaction was found to be 239 MHz. The increased resolution a...

Reactions of BrCl with alkyl radicals.

Abstract It is demonstrated that photohalogenations of low reactivity substrates with BrCl occurs mainly with Cl· selectivity. With tertiary or benzylic hydrogens in the substrate, mainly Br· selectivity is observed. These observations are rationalized, taking into account the relative concentrations of halogen atoms and their respective rates of hydrogen abstractions. The resultant radicals react with BrCl to make (RBr/RCl) in ratios between 1 and 15.

REACTIONS OF ATOMS: SILICON AND THE HIGH BOILING METALS. DIRECT SYNTHESES OF ORGANOMETALLICS

The reactions of atomic Si, Mg, Pt, Ni, Co, Al, Dy, etc. with organic substrates occur at -1960, producing organometallic products.