Solution study of the ambient temperature monomer-dimer equilibrium Th{sub 2}(OR){sub 8}{rightleftharpoons} 2Th(OR){sub 4} (R = CH-i-Pr{sub 2}) and X-ray crystal structures of Th{sub 2}(OCH-i-Pr{sub 2}){sub 8}, Th(OCH-i-Pr{sub 2}){sub 4}(quin), and ThI(OCH-i-Pr{sub 2}){sub 3}(py){sub 2}
- Los Alamos National Lab., NM (United States)
The thorium metallacycle [(Me{sub 3}Si){sub 2}N]{sub 2}Th[N(SiMe{sub 3})(SiMe{sub 2}CH{sub 2})] (1) reacts with 4 equiv of 2,4-dimethylpentan-3-ol(diisopropylmenthanol) in toluene at room temperature to produce dimeric Th{sub 2}(OR){sub 8}(2)(R=CH-i-Pr{sub 2}). {sup 1}H NMR spectra of 2 in noncoordinating solvents indicate a monomer-dimer equilibrium in solution at ambient temperatures between 2 and its monomer Th(OR){sub 4} (3). Thermodynamic parameters for the equilibrium process are {delta}H{degrees} = 17 kcal mol{sup {minus}1}, {delta}G{degrees} = 5 kcal mol{sup {minus}1}, {delta}S{degrees} = 40 cal mol{sup {minus}1} K{sup {minus}1}. Addition of Lewis bases such as DME (DME = 1,2-dimethoxyethane), pyridine or quinuclidine to solutions of 2 results in the formation of the five- and six-coordinate mononuclear adducts Th(OR){sub 4}(DME) (4), Th(OR){sub 4}(py){sub 2}(5), and Th(OR){sub 4}(quin) (6), respectively. Reaction of 5 with 1 equiv of Me{sub 3}SiI produces the monoiodide derivative ThI(OR){sub 3}(py){sub 2}(7). Compounds 2-7 have been characterized by {sup 1}H NMR and IR spectroscopy, by elemental analysis, and, in the case of 2,6, and 7, by single crystal X-ray diffraction studies. Th{sub 2}(OCH-i-Pr{sub 2}){sub 8}(2) exhibits a dimeric structure in which the Th{sub 2}O{sub 8} core can be viewed as two ThO{sub 5} trigonal bipyramids joined along a common axial-equatorial edge. Terminal Th-O distances average 2.154(11) {Angstrom} while bridging Th-O distances are significantly longer at 2.436(11) {Angstrom} (average).
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 469010
- Journal Information:
- Inorganic Chemistry, Vol. 34, Issue 22; Other Information: PBD: 25 Oct 1995
- Country of Publication:
- United States
- Language:
- English
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