S. M. Murgia

Vibrational spectra of π-allyl-and π-allyl-d5-dicarbonyl-nitrosyliron

Abstract Vibrational spectra of π-C3H5Fe(CO)2NO and π-C3D5Fe(CO)2NO have been studied in the liquid and solid states. The spectra have been interpreted on the basis of a C3 molecular symmetry. A reassignment of some bands is proposed for the allylic fragment based on vH/vD isotopic shifts. Examination of spectra of deuteriated derivatives has also allowed a reasonable assignment of all modes involving the FeCO and FeNO groups.

Polarographic behaviour of π-allylic complexes of transition metals : II. π-allyltricarbonylcobalt and some phosphinic derivatives

Abstract The polarographic reduction in acetonitrile (ACN) of π-C3H5Co(CO)3 and of the phosphinic derivatives π-C3H5Co(CO)2L [L = P(OC6H5)3, P(OCH2)3CC2H5, P(C6H5)3, P(OC2H5)3, P-n-Bu3, P(C6H11)3] is reported and the reduction mechanism is discussed. The dependence of the E 1 2 of thecomplexes on the properties of the ligands is analysed, and a linear plot of E 1 2 vs. ΔHNP of the ligands is observed. The pseudo first-order rate constants for the reduction of the complexes with NaBH4 in ACN are reported.

Infrared spectrum and vibrational assignment of π-allyltricarbonylcobalt

Summary The infrared spectrum of π-allyltricarbonylcobalt has been recorded between 4000 and 300 cm −1 . The assignment of fundamental motions was essentially based on the crystal spectra in polarized light. The observed absorption pattern in the solid state seems to indicate that the molecule crystallizes in the monoclinic P m or C m space groups.

Force Field Calculations of Some Halogenated Monosubstituted Derivatives of Selenophene and Tellurophene

Abstract Force fields have been calculated for 2-Chloro and 2-Bromo derivatives of Selenopnene and Tellurophene. The calculation of the fundamental frequencies was performed starting from a GVTF which was proven satisfactory for the heter-ocyclic parent molecules. In the initial steps we refined only the force constants mostly involving the substituent vibrational modes. In the final step, some force constants involving the ring motions were also released, in order to obtain the best fit. The procedure has been developed with the aim of getting information on the influence of the substituent effects on the heteroaromatic ring force field.

An overlay calculation of the molecular force field of 2- and 3-halogeno derivatives of thiophene

Abstract A normal mode calculation, which includes force constants, vibration mean amplitudes, Coriolis parameters and thermodynamic properties, has been performed on a series of six halogenated thiophenes. The zeroth-order force field we have used is that of the thiophene parent molecule, and some specific force constants and interaction constants have been refined using the overlay technique. Results show that the halogen substitution acts upon the heterocyclic ring motion frequencies as an isotopic substitution, viz. with small electronic effects but with remarkable mass effects.

The microwave spectrum of 3-chlorothiophene

Abstract The microwave spectra of the normal, Cl(37) and S(34) isotopic species of 3-Chlorothiophene have been investigated in the frequency range 26.4–40 GHz. A first adjustment of the rotational constants was done on the basis of the (B+C) values obtained from the μ a -R-type bands of the Cl(35) and Cl(37) isotopic species. Rotational, centrifugal distortion and quadrupole coupling constants have been obtained for such an asymmetric rotor.

Dipole Moments and Molecular Conformation of Allylcarbonylnitrosyl Iron Complexes

The dipole moments of the complexes π (CH2CXCH2) Fe (CO) (NO) L, with X and L equal, respectively, to H, CO; H, P (C6H5)3; CH3, CO; Cl, CO; Br, CO, have been measured. From the results it is concluded that: 1. The value of the group moment is ca. 1.6 D, if = 1.3 D and Co-Fe-CO(NO) =98°. 2. A trans structure appears most likely in the π (CH2CYCH2) Fe (CO) 2NO (Y = Cl, Br, CH3). 3. Qualitative comparison between and group moments confirms that the C5H5 group bonds to manganese as (C5H5)δ-.

The Polarographic Reduction of Diazoacetone

The electrochemical reduction of diazoacetone in 10 % water: ethanol solution, between pH = 3 and pH = 9, has been studied. Two waves have been observed in acid solution: the first is attributed to the reduction of diazoacetone to aminoacetone and the second one to the reduction of 2,5-dimethyldihydropyrazine (formed by dimerization of the aminoacetone) to 2,5-dimethylpiperazine. In neutral and alkaline media the first wave splits into two waves corresponding to a reduction of diazoacetone to hydrazone and aminoacetone.

Electrochemical Behaviour of the Fe(CO)3NO⊖ Ion

The polarographic behaviour of [(C2H5)4N] ⊕ [Fe(CO)3NO⊖] has been investigated at the mercury dropping electrode and platinum stationary electrode. It was found that the complex displays two anodic and one cathodic waves. On the basis of the results obtained a mechanism is proposed and discussed.