Jaap N. Louwen

The electronic structure of dinuclear transition-metal complexes containing metal—metal interactions: II. He(I) and He(II) photoelectron spectra of hexacarbonyldi-irondisulfur and related complexes

Abstract The He(I) and He(II) photoelectron spectra of a series of Fe 2 (CO) 6 LL 1 -type complexes (L = L 1 = S, ( i -propyl)S; L,L 1 = t -but of an all-electron, ab initio SCF MO calculation on Fe 2 (CO) 6 S 2 and of extended CNDO calculations on related molecules. Assignments given ar He(I)/He(II) intensity differences, and on comparison with related molecules. The coordination of the bridging ligands to the metal centres and the nature of the metal—metal interactions are discussed.

He(I) and He(II) photoelectron spectra of mononuclear transition metal carbonyl complexes containing a 1,4-diaza-1,3-butadiene ligand

Abstract He(I) and He(II) photoelectron spectra have been recorded for the following mononuclear transition metal carbonyl complexes containing symmetrically 1,4-disubstituted 1,4-diaza-1,3-butadienes, RNC(R′)C(R″)NR, d6 [M(CO)4(RNCHCHNR)] (M = Cr, W, R = i-Pr; M = Mo, R = t-Bu) and [ReCl(CO)3(i-Pr-NCHCHN-i-Pr)], d8 [M(CO)3(RNCR′CR″NR)] (M = Fe, R = t-Bu, n-Bu, c-Hex, R′ = R″ = H; M = Fe, R = n-Bu, R′ = R″ = Me; M = Ru, R = i-Pr2CH, R′= R″ = H) and [Fe(t-BuNCHCHN-t-Bu)2], and d10 [Ni(CO)2(t-BuNCHCHN-t-Bu)] and [Ni(t-BuNCHCHN-t-Bu)2]. The observed vertical ionization energies (IEs) are tabulated and assigned to metal d orbitals and ligand systems on the basis of the results of semi-empirical molecular orbital (MO) calculations, He(I)/He(II) intensity ratios, and comparisons with related molecules (trend effects). The weighted average IE of the metal d orbitals in each R-DAB complex ( IE ′d) is lower than that of the corresponding unsubstituted metal carbonyl complex ( IE d). The values of ΔIEd (= IE ′d - IE d) are −1.54 eV for the d6 complexes, −1.80 eV for the d8 system and −2.09 eV for the d10 compound. This means that ΔIEd increases by the same amount on going from d6 to d8 complexes (0.26 eV) as it does on going from d8 to d10 complexes (0.29 eV). Replacement of two CO groups by a second RNCHCHNR ligand leads to a further lowering of the weighted average IE of the d orbitals (−0.5 eV) which is significantly less than that found for the first substitution.

The He(I) and He(II) Photoelectron Spectra of some η5-Cyclopentadienyl-Titanium, -Zirconium and -Hafnium Trihalide Complexes

The He(I) and He(II) photoelectron spectra are reported for (η5-C5H5)MX3 (M = Ti, Zr, Hf; X = Cl, Br) and some methylcyclopentadienyl and pentamethylcyclopentadienyl derivatives. Unambiguous assignments are made of the Cp orbitals, the halide a2 and e orbitals. Very regular trends are observed in the ionization energies upon substitution of the ring, metals and ligands.

He I and He II photoelectron spectra of trans-[MCl2L2](M = Pd, L = PEt3 or AsEt3; M = Pt, L = NMe3, PMe3, PEt3, or AsEt3) and trans-[PtH(Cl)(PEt3)2], and Hartree-Fock–Slater calculations on model compounds

U.v. photoelectron spectra of trans-[MCl2L2](M = Pd, L = PEt3 or AsEt3; M = Pt, L = NMe3, PMe3, PEt3, or AsEt3) are reported, as well as Hartree-Fock–Slater calculations on the model compounds trans-[MCl2(EH3)2](M = Pd, E = N or P; M = Pt, E = N). The results from these calculations and empirical assignment criteria such as He I/He II intensity differences and shift effects upon substitution have enabled a full assignment of the upper valence ionizations. Evidence is found for a through-space interaction of phosphorus and arsenic orbitals with orbitals localized on the chloride ligands. The energy levels for ionizations in corresponding complexes of Pd and Pt are rather similar, with the exception of ionizations from orbitals due to π interaction of chloride orbitals with d orbitals of appropriate symmetry. It appears that these interactions are much stronger with Pt than with Pd.

He(I) and He(II) photoelectron spectra of some organozinc and organoaluminium radicals containing 1,2-bis(t-butylimino)ethane

He(I) and He(II) spectra of the organometallic radicals AlEt2(L)·, ZnMe(L)·, and ZnEt(L)·(L = ButNCH–CHNBut) generated in the gas phase have been measured. The observed ionization energies (i.e.s) for AlEt2(L)· are qualitatively in agreement with results from an MNDO calculation performed for the model radical AlMe2(L)·(L = MeNCH–CHNMe). Very low i.e.s for the radical electrons (about 6 eV) are observed. These electrons reside mainly in the ligand π* orbital. Considerable delocalization of all valence molecular orbitals over the whole molecule is demonstrated. Strong charge donation from the N lone pairs towards the metal is apparent both in the i.e.s of the ligand orbitals without metal interactions and in the low i.e. values for Zn 3d ionizations.

The electronic structures of some aromatic sulfinylamines

Abstract He(I) and He(II) photoelectron spectra of some sulfinylamines are reported and assignments made on the basis of CNDO/S LCAO MO calculations. Insight into the effects of several substituents on the electronic structures of the compounds is obtained. The difference between the actual electronic structure of o , o ′, p -trimethyl sulfinylaniline and that interpolated from other molecules in the series is assumed to reflect a different conformation for this compound. The results of the MO calculations agree fairly well with the experimental data, although some discrepancies occur, concerning especially the π-donating capacity of a Cl substituent, and ionizations from chlorine lone pair orbitals.

The He(I) and He(II) Photoelectron Spectra of Tm2Zn (Tm = (C5H5)Fe(CO)2, (C5H5)M(CO)3; M = Cr, Mo, W)

UV photoelectron spectra of the title compounds are reported. Assignments are made with the help of He(I)/He(II) intensity differences, shift effects upon substitution and comparison with related molecules. Previously drawn conclusions about the electronic structure of similar complexes also hold for the compounds. It is indicated that the ionization energy for the symmetric metal-metal bond strongly depends on the overlap between transition and post-transition metals.

Ultraviolet Photoelectron Spectra of Square Planar Complexes of Nickel Triad Metals, I.He(I) and He(II) Spectra of [M{C6H3(CH2NMe2)2o,o′}X], (M = Ni, Pt; X = Cl, Br, I. M = Pd; X = Br)

UV photoelectron spectra of the title compounds are reported. Assignments based on He(I)/He(II) intensity differences, shift effects, and comparison with related molecules allow an assignment of the upper valence bands. Electronic differences between nickel and both platinum and palladium are reflected in the spectra, especially with respect to bands due to ionization of electrons from the metal. Strong evidence is found for π interaction of the ligand phenyl system with metal orbitals

He(I) and He(II) Photoelectron Spectra of Some L3MCo(CO)4 Complexes (M = Si, Ge, Sn, Pb and L = Cl, Br and CH3)

Abstract The He(I) and He(II) photoelectron spectra of L3MCo(CO)4 complexes (M = Si, Ge, Sn, and Pb and L = Cl, Brand CH3) are reported. Bands attributable to the metal-cobalt bond, cobalt 3d and CO orbitals are assigned in agreement with a qualitative MO model. Relativistic effects and He(I)/He(II) intensity ratios prove to be important in assigning these ultraviolet photoelectron spectra.

The Hei and HeH Photoelectron Spectra of [Fe*?3-C3H5(CO)3X] and [Fe^3-C4H7 (CO)3X] (X = Cl, Br, I) and [CoC3H5(CO)3]

Abstract By means of UV photoelectron spectroscopy (UPS) the electronic structures of [Feη3.C3H5(CO)3X], [Feη3-(2-CH3C3H4)(CO)3X] (X = Cl, Br, I) and [Co(C3H5)(CO)3] have been studied. Detailed assignments are possible and surprisingly low ionization energies (as low as 8.19 eV) are found for iodine lone pair type Orbitals. From the spectra a large difference in π backbonding is found between the cobalt and iron complexes