No abstract

The photoelectron spectra of some five-co-ordinate trigonal-bipyramidal complexes [Fe(CO),L] (L = PMe,, PPh,, AsPh,, or pyridine in an axial position, or CH,=CH-CN and CH,=CH-CHO in the equatorial plane) have been measured. The spectra have been assigned by comparing them with one another and with those available for [Fe(CO),] and [Fe(C0),(q-C,H4)].CNDO calculations carried out for [Fe(CO),(py)] and [Fe(CO),(q2-CH,= CH-CN)] are of only limited help in making assignments. The substituent effect on the stability of the Fe-L bond is discussed. The stability order obtained is the same as that found previously via kinetic studies.

Semiempirical CN D 0 / 2 calculations have been performed on the series of compounds phenylcyclopropane, phenyloxiran, phenylthiiran, phenylaziridine, and 1.1 -dichloro-2-phenylcyclopropane. From the energies obtained, it is concluded that for all these molecules the most stable conformation is that in which the planes of the phenyl group and of the three-membered ring are orthogonal (or very close to orthogonal) to one another. These results indicate that inter-ring conjugation is present. The energy barrier to rotation about the phenyl-threemembered ring bond is

Semiempirical CND0/2 calculations have been applied to the rotational isomerism of the hindered a-diazo ketones CH2ClCOCHN2 and CH3COCCH3N2. It is concluded that the cis form is the more energetically stable for the chloroderivative, whilst both cis and trans forms are present in the other compound. These results are in agreement with spectroscopic measurements and experimental electric dipole moments.

The photoelectron spectra of the compounds MMe,X (M = C, Si, Ge, Sn, and Pb; X = CI and Br) have been measured. An assignment of the spectra is proposed based on a comparison with spectra of the similar compounds MMe, and MXH, and on semiempirical CNDO calculations which have been extended to third-row elements.