Relative strengths of early transition metal M-H and M-C bonds in substituted niobocenes and tantalocenes. Thermodynamic trends and electronic factors of olefin insertion into a metal-hydride bond

Journal Article · Wed Jul 05 04:00:00 EDT 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00196a001· OSTI ID:6835958

Lichtenberger, D L; Darsey, G P; Kellogg, G E ^[1]; Sanner, R D; Young, Jr, V G; Clark, J R ^[2]

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1. Univ. of Arizona, Tucson (USA)
2. Arizona State Univ., Tempe (USA)

Principles of M-C and M-H bonding interactions are examined experimentally by high-resolution valence photoelectron spectroscopy. Gas-phase He I and He II photoelectron spectra are reported for the following series of d{sup 0} and d{sup 2} bent metallocenes: Cp{sub 2}MH{sub 3} (M = Nb, Ta), Cp{sub 2}M(CO)L (M = Nb, Ta; L = H and M = Nb; L = CH{sub 3}), and Cp{sub 2}M(C{sub 2}H{sub 4})L (M = Nb, Ta; L = H and M = Ta; L = C{sub 2}H{sub 5}) (Cp = {eta}{sup 5}-C{sub 5}H{sub 5}). The ligand replacements represented by this series of complexes allow stepwise comparison and assignment of each individual low-energy valence ionization band. The He I/He II spectral comparisons show that the lowest ionization energy band of the carbonyl complexes is higher in metal character than the corresponding ionization of the ethylene complexes. This trend indicates extensive electron delocalization in the metal-ethylene bonding that corresponds more accurately to a metallacyclopropane description with relatively strong metal-carbon bonds. The photoelectron data for the early transition metal hydride and alkyl species show that the metal-hydrogen bonds are slightly more stable than the metal-carbon bonds. Correlation of the ionization information for these substituted early metallocenes reveals that the stabilization of the metallacyclopropane-hydride structures, M(C{sub 2}H{sub 4})H, relative to the olefin-inserted metal-alkyl structure, M(C{sub 2}H{sub 5}), is partly due to stabilization of the metal electron density by back-bonding to the olefin as indicated by earlier theoretical studies.

• OSTI ID: 6835958
• Journal Information: Journal of the American Chemical Society; (USA), Journal Name: Journal of the American Chemical Society; (USA) Vol. 111:14; ISSN 0002-7863; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400000* -- Chemistry
400201 -- Chemical & Physicochemical Properties
CHEMICAL BONDS
COMPLEXES
DATA
DATA ANALYSIS
ELECTRON SPECTROSCOPY
ELEMENTS
EXPERIMENTAL DATA
INFORMATION
MEASURING INSTRUMENTS
MEASURING METHODS
METALS
NIOBIUM
NUMERICAL DATA
PHOTOELECTRON SPECTROSCOPY
SPECTROSCOPY
TANTALUM
TRANSITION ELEMENT COMPLEXES
TRANSITION ELEMENTS