| The divalent ytterbium organometallic compound, dipotassium bis( 8 annulene)ytterbate(II), 1, and its divalent calcium analog, 2, have been synthesized and characterized. The crystal structure of the bis-dimethoxyethane adduct of 1 shows a centrosymmetric ytterbium atom complexed by two 8 annulene rings. A potassium coordinated with a dimethoxyethane molecule is at the opposite side of each ring. A comparison of the infrared spectra and x-ray powder patterns of the bis-dimethoxyethane adducts of 1 and 2 indicate that the two complexes are isostructural and suggests that the ring-metal interaction in 1 is essentially ionic in nature.;The crystal structure of the bis-diglyme adduct of the di-t-butyl derivative of 1, K(C(,6)H(,14)O(,3)) (,2) Yb(t-BuC(,8)H(,7))(,2) , indicates that the central carbon atom of the t-butyl group is in the least-squares plane of the 8 annulene ring.;The trivalent ytterbium(III) complex, potassium bis( 8 annulene)ytterbate(III), 3, has also been synthesized. In tetrahydrofuran solution, an electron exchange reaction occurs between 1 and 3. The second order rate constant of this electron exchange is (TURNEQ) 10('6) moles('-1)s('-1) at -10(DEGREES)C as determined from ('1)H-NMR data.;A previously reported synthesis of bis( 8 annulene)cerium(IV), 4, has now been verified. Characterization of 4, including its photo-electron spectrum, suggests that the ring-metal interaction in 4 includes interaction of the ligand e(,2u) orbitals with the metal E(,2u) (4f) orbitals. The formation of 4 from the chemical oxidation of the known complex, potassium bis( 8 annulene)cerate(III), is also reported.;A comparison of the infrared spectra of the bis( 8 annulene) lanthanide complexes indicates that all of the absorbances in the 600 to 3000 cm('-1) range are due to ligand vibrations, and further suggests that shifts of these vibrations upon changing the central metal atoms are not indicative of a covalent ring-metal interaction in the bis( 8 annulene) complexes. |
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