Binding energies (BE) of 18 pure vanadium compounds (V 2p3/2 niveau) were measured in selected oxygen and chlorine environments, linearity of BE vs. oxidation states scrutinized and appropriate model compounds chosen as comparative standards. The general trend is an increase of BE with formal oxidation state; in particular, it could be counterbalanced by electron donating/withdrawing ligands on the V atom. A graphical (computerized) background substraction method was utilized to remove an interfering O 1s satellite peak and to enhance accuracy of BE values in surface compounds. BEs of (SiO)3VO (I), (SiO)3V (II), and (SiO)3V(O2) (III) were determined. By comparison to standards positive BE shifts of about 2.1 eV were derived indicating the strong electron withdrawing (“electron sink”) effect of the support on V in surface compounds. This is the first reported ESCA data on a surface peroxo complex, (III). Some implications of the results are also discussed.

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Es werden die Photoelektronenspektren (AlKα, HeI) von NbI5, NbI4, Nb3I8, Nb6I11, HNb6I11, Nb6I8(CH3NH2)6, Nb6I8(C3H7NH2)6 und Nb gemessen und diskutiert. Es läßt sich zeigen, daß die Bindungsenergie BE der Niob‐Rumpfniveaus linear von der Oxydationszahl n (n = I/Nb) abhängt; für das Nb 3d5/2‐Niveau ergibt sich die Beziehung BE = 201,8 + 1,07 · n. Durch Anwendung dieser Beziehung wird der hydridartige Charakter des Wasserstoffs in HNb6I11 wahrscheinlich gemacht sowie die Zunahme der Elektronenkonzentration im Nb6I8‐Cluster der Verbindungen Nb6I8(CH3NH2)6 und Nb6I8(C3H7NH2)6 belegt. Für Nb6I11(HNb6I11) ergibt sich eine verbotene Zone Eg = 0,40 (0,45) eV, für die Amine ist der Abstand der Oberkante des Valenzbandes zur Fermi‐Kante 0,70 (CH3NH2) bzw. 0,68 eV (C3H7NH2).

Binding energy (BE) behavior and signal intensity as function of V conc. and ligands L were critically examined in Vn/SiO2 species (where n = +5, +4, and +3) and securing of optimized products and ESCA samples is described. The results moreover demonstrate conditions and approaches whereby ESCA can provide reliable information on highly diluted surface compound systems. From aquous media 1.0–1.2 wt. % VV and 0.4–1.2 wt. % VIII proved to be preferred ranges whereas in non aqueous (metalorganic) preparates the surprisingly low concentration of 0.4–0.15 wt. % VIII gave usable spectra and even 0.4 wt. % VV could be measured. ESCA data with the peroxo complex (SiO)3V(O2) (I) confirmed these trends. Superiorly subdivided surface compounds (reflected in the quality of spectra) are obtainable from V[N(SiMe3)2]3 impregnations where 0.4–0.5 wt. % VIII (or VV) are maximum/optimum conc. limits. Evidence for formulating Vn/SiO2 as three legged surface compounds is summarized and diagnostic/predictive uses of the additivity principle for surface electron states illustrated. In the (SiO)3VL series, where L = none, O, and (O2) positive ΔBE shifts for SiOV (0.7 eV); VO (0.6 eV); and V(O2) (0.4 eV) were estimated. Tentative BE contributions of some donor ligands (and Cl) are also suggested. In (I) ESCA indicated a formal oxidation state of approx. +4. Certain limits (precautions) with ESCA are noted and extensions of the additivity relationship discussed.

Conveniently available transition metal hexamethyldisilazanes (M‐HMDS) are described as novel surface reacting agents in SiOM type surface compound formation on silicagel. Secondary reaction products SiOSiMe3 and SiN(SiMe3)2 confer “silanized” (hydrophobic) environments which can be removed at 300–400°C. Reactivity of MN linkages with surface silanols and strained siloxanes can be manipulated by coordinating ligands L (also as solvents) in the molecule. Three legged vanadium(III) surface compounds were obtained directly by thermal activation of V[N(SiMe3)2]3 on SiO2 in neutral or reducing atmospheres. Detailed course of the reaction were monitored by ESCA and Reflectance Spectroscopy. Impregnation from benzene (0.40–0.45 wt. % V) and subsequent heating to 400–800°C (for 1 hr) gave optimized products. The optimized (SiO)3V from V(HMDS)3 was found to have identical spectral, chemical, and catalytical properties as the oxidation/reduction products from NH4VO3 etc. from aq. impregnations including chemiluminescence with O2 at 20°C. This is the first reported example of such remarkable surface product correspondence by different mechanistic pathways and its utility in structural elucidation is emphasized. Importance of chemiluminescence as most sensitive indicator of identical surface states is discussed as well as attempts to produce “naked” two legged VII/SiO2 and VIII/SiO2.