Electron diffraction patterns of the fullerene C(60) in the gaseous state have been obtained by volatilizing it from a newly designed oven-nozzle at 730 degrees C. The many peaks of the experimental radial distribution curve calculated from the scattered intensity are completely consistent with icosahedral symmetry for the free molecule. On the basis of this symmetry assumption, least-squares refinement of a model incorporating all possible interatomic distances led to the values r(g)(C(1)-C(2)) = 1.458(6) angstroms (A) for the thermal average bond length within the five-member ring (that is, for the bond fusing five- and six-member rings) and r(g)(C(1)-C(6)) = 1.401(10) A for that connecting five-member rings (the bond fusing six-member rings). The weighted average of the two bond lengths and the difference between them are the values 1.439(2) A and 0.057(6) A, respectively. The diameter of the icosahedral sphere is 7.113(10) A. The uncertainties in parentheses are estimated 2sigma values.

Isopenicillin N synthase (IPNS) is a unique mononuclear non-heme Fe enzyme that catalyzes the four electron oxidative double ring closure of its substrate ACV. A combination of spectroscopic techniques including EPR, absorbance, circular dichroism (CD), magnetic CD, and variabletemperature, variable-field MCD (VTVH-MCD) were used to evaluate the geometric and electronic structure of the {FeNO} 7 complex of IPNS coordinated with the ACV thiolate ligand. Density Function Theory (DFT) calculations correlated to the spectroscopic data were used to generate an experimentally calibrated bonding description of the Fe-IPNS-ACV-NO complex. New spectroscopic features introduced by the binding of the ACV thiolate at 13,100 and 19,800 cm −1 are assigned as the NO π*(ip) → Fe d x2−y2 and S π → Fe d x2−y2 charge transfer (CT) transitions, respectively. Configuration interaction mixes S CT character into the NO π*(ip) → Fe d x2−y2 CT transition, which is observed experimentally from the VTVH-MCD data from this transition. Calculations on the hypothetical {FeO 2 } 8 complex of Fe-IPNS-ACV reveal that the configuration interaction present in the {FeNO} 7 complex results in an unoccupied frontier molecular orbital (FMO) with correct orientation and distal O character for H-atom abstraction from the ACV substrate. The energetics of NO/O 2 binding to Fe-IPNS-ACV were evaluated and demonstrate that charge donation from the ACV thiolate ligand renders the formation of the Fe III -superoxide complex energetically favorable, driving the reaction at the Fe center. This single center reaction allows IPNS to avoid the O 2 bridged binding generally invoked in other non-heme Fe enzymes that leads to oxygen insertion (i.e. oxygenase function) and determines the oxidase activity of IPNS.

The alpha-ketoglutarate (alpha-KG)-dependent oxygenases are a large and diverse class of mononuclear non-heme iron enzymes that require FeII, alpha-KG, and dioxygen for catalysis with the alpha-KG cosubstrate supplying the additional reducing equivalents for oxygen activation. While these systems exhibit a diverse array of reactivities (i.e., hydroxylation, desaturation, ring closure, etc.), they all share a common structural motif at the FeII active site, termed the 2-His-1-carboxylate facial triad. Recently, a new subclass of alpha-KG-dependent oxygenases has been identified that exhibits novel reactivity, the oxidative halogenation of unactivated carbon centers. These enzymes are also structurally unique in that they do not contain the standard facial triad, as a Cl- ligand is coordinated in place of the carboxylate. An FeII methodology involving CD, MCD, and VTVH MCD spectroscopies was applied to CytC3 to elucidate the active-site structural effects of this perturbation of the coordination sphere. A significant decrease in the affinity of FeII for apo-CytC3 was observed, supporting the necessity of the facial triad for iron coordination to form the resting site. In addition, interesting differences observed in the FeII/alpha-KG complex relative to the cognate complex in other alpha-KG-dependent oxygenases indicate the presence of a distorted 6C site with a weak water ligand. Combined with parallel studies of taurine dioxygenase and past studies of clavaminate synthase, these results define a role of the carboxylate ligand of the facial triad in stabilizing water coordination via a H-bonding interaction between the noncoordinating oxygen of the carboxylate and the coordinated water. These studies provide initial insight into the active-site features that favor chlorination by CytC3 over the hydroxylation reactions occurring in related enzymes.

We report vibrational Raman and infrared spectra for chemically separated CbO and C7e fullerenes. Thin film samples were prepared by subliming the chromatographically separated species onto appropriate substrates. The Cso Raman spectrum shows eight clear lines and two weaker ones. If CsO in fact has the proposed buckminsterhtllercne structure (as is strongly indicated by recent experiments), the present Raman measurements together with the four observed IR frequencies give a complete set of Raman and infrared active fundamental frequencies for this molecule. A comparison of this set with the calculated spectrum for buckminsterfullerene shows satisfactory agreement.

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Borohydride-reduced nickel (P-2 Ni) , used with ethylenediamine, is highly stereospecific for the hydrogenation of alkynes to pure olefins with cis: trans ratios as high as 200: 1.REDUCTION of nickel(I1) acetate with sodium borohydride in ethanol yields a nearly colloidal non-magnetic black nickel catalyst, P-2 nickel, which is extremely sensitive to substrate structure in olefin hydrogenation.1 Reduction of disubstituted alkynes with this catalyst results in high yields of the corresponding alkenes with cis : trans ratios of 30: 1.2 Thus, hex-3-yne gives 96% hex-3-ene (cis : trans 29 : 1) .2b

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Reduction of nickelous acetate with sodium borohydride in ethanolic solution yields a nearly colloidal black suspension (P-2 nickel) which, used in situ, is a hydrogenation catalyst of extraordinary sensitivity to the environment of the double bond. Slight increases in hindrance are strongly reflected in the rate of hydrogenation: 1octene, 1.00; 3-methyl-1-butene, 0.23; 3,3-dimethyl-1-butene, 0.07. Substitution of the olefinic moiety more markedly affects the reduction rate: 1-octene, 1.0; 2-methyl-1-pentene, 0.004; 2-methyl-2-pentene, <<0.001; 2,3-dimethy 1-2-butene, 0. Cyclohexene is peculiarly inert among simple cyclic alkenes: cyclopentene, 1.00; cyclohexene, ~0.010; cycloheptene, 0.60; cyclooctene, 0.20. Strained double bonds are readily reduced: bicyclo[2.2.ljheptene, 1.0; cyclopentene, 0.26; cis-2-pentene, <0.01. The presence of an aryl group, even nonconjugated, markedly promotes hydrogenation: 1-octene, 1.0; 3,4-methylenedioxyallylbenzene (safrole), >3.5; allylbenzene, 3.0. Double-bond isomerization and disproportionation of cyclohexadienes are minimal. Benzylic compounds are not hydrogenolyzed significantly in 24 hr, and allylie and propargylic compounds are hydrogenated with no detectable hydrogenolysis. Dienes and acetylenes are partially reduced with high selectivity.Sodium borohydride reacts with various group VIIIB transition metals to yield finely divided black precipitates, some of which are active catalysts for hydrolysis of borohydride.3•4 567Certain of these materials have been shown to be hydrogenation catalysts