(Me/sub 5/C/sub 5/)/sub 2/Yb(. mu. -Me)Be(C/sub 5/Me/sub 5/): a model for methane coordination
One strategy for synthesis of a substituted methane complex, M reverse arrow CH/sub 4/X, is to choose a ligand or a group X whose electronegativity is less than that of a methyl group so that the permanent dipole moment is in the direction of carbon rather than X. A convenient molecule is MeBe(C/sub 5/Me/sub 5/) since it is monomeric, as is MeBe(C/sub 5/H/sub 5/); therefore, no steric effects will prevent coordination, and it presumably has a dipole moment. A convenient Lewis acid is (Me/sub 5/C/sub 5/)/sub 2/ Yb since it is a bent metallocene in gas phase, therefore, the reorganization energy of bending is small, and this 4f metallocene forms coordination complexes with olefins and acteylenes. The geometry of the fragments in the complex in the solid state is very weakly perturbed relative to the individual parts as determined by gas electron diffraction. The principle perturbations are that the Yb-C(C/sub 5/Me/sub 5/) distance lengthens by ca. 0.06 A and the (Me/sub 5/C/sub 5/)ring centroid-Yb-(Me/sub 5/C/sub 5/)ring centroid closes by ca. 13/sup 0/. In solution the resonance in the /sup 1/H NMR spectrum due to the bridging methyl group is deshielded by 0.1 ppm relative to free MeBe(C/sub 5/Me/sub 5/). The complex is undergoing rapid intermolecular chemical exchange to -70 /sup 0/C.
- Research Organization:
- Lawrence Berkeley Lab., CA
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5975833
- Journal Information:
- J. Am. Chem. Soc.; (United States), Vol. 109:19
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BERYLLIUM COMPOUNDS
CHEMICAL PREPARATION
MOLECULAR STRUCTURE
ORGANOMETALLIC COMPOUNDS
YTTERBIUM COMPOUNDS
BOND ANGLE
BOND LENGTHS
EXPERIMENTAL DATA
HYDROGEN 1
METHANE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
ALKALINE EARTH METAL COMPOUNDS
ALKANES
DATA
DIMENSIONS
HYDROCARBONS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
LENGTH
LIGHT NUCLEI
MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
RARE EARTH COMPOUNDS
RESONANCE
SPECTRA
STABLE ISOTOPES
SYNTHESIS
400201* - Chemical & Physicochemical Properties