Solution Study of the Ambient Temperature Monomer-Dimer Equilibrium Th2(OR)8 .dblharw. 2Th(OR)4 (R = CH-i-Pr2) and X-ray Crystal Structures of Th2(OCH-i-Pr2)8, Th(OCH-i-Pr2)4(quin), and ThI(OCH-i-Pr2)3(py)2
                                
                                    
                                        作者:David M. Barnhart、David L. Clark、John C. Gordon、John C. Huffman、John G. Watkin、Bill D. Zwick                                    
                                    
                                        DOI:10.1021/ic00126a008
                                    
                                    
                                        日期:1995.10
                                    
                                    The thorium metallacycle [(Me(3)Si)(2)N]Th-2[N(SiMe(2))(SiMe(2)CH(2))] (1) reacts with 4 equiv of 2,4-dimethylpentan-3-ol (diisopropylmethanol) in toluene at room temperature to produce dimeric Th-2(OR)(8) (2) (R = CH-i-Pr-2). H-1 NMR spectra of 2 in noncoordinating solvents indicate a monomer-dimer equilibrium in solution at ambient temperatures between 2 and its monomer Th(OR)(4) (3). Thermodynamic parameters for the equilibrium process are Delta H degrees = 17 kcal mol(-1), Delta G degrees = 5 kcal mol(-1), Delta S degrees = 40 cal mol(-1) K-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)(4)(DME) (4), Th(OR)(4)(py)(2) (5), and Th(OR)(4)(quin) (6), respectively. Reaction of 5 with 1 equiv of Me(3)SiI produces the monoiodide derivative TnI(OR)(3)(py)(2) (7). Compounds 2-7 have been characterized by H-1 NMR and IR spectroscopy, by elemental analysis, and, in the case of 2, 6, and 7, by single crystal X-ray diffraction studies. Th-2(OCH-i-Pr-2)(8) (2) exhibits a dimeric structure in which the Th2O8 core can be viewed as two ThO5 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). Th(OCH-i-Pr-2)(4)(quin) (6) displays a trigonal bipyramidal geometry with the quinuclidine ligand occupying an axial site. Th-O distances average 2.165(17) Angstrom while the Th-N distance is 2.712(11) Angstrom. ThI(OCH-i-Pr-2)(3)(py)(2) (7) exhibits a facial pseudooctahedral geometry in the solid state, with Th-O and Th-N distances averaging 2.136(8) and 2.746(9) Angstrom, respectively, and a Th-I distance of 3.226(1) Angstrom. Crystal data for 2 at -170 degrees C: monoclinic space group P2(1)/n, a = 12.115(2) Angstrom, b = 20.820(3) Angstrom, c = 13.002(2) Angstrom, beta = 100.62(1)degrees, V = 3223.4 Angstrom(3), d(calcd) = 1.428 g cm(-3), Z = 2. Crystal data for 6 at -70 degrees C: monoclinic space group Cc, a = 18.778(3) Angstrom, b = 11.391(2) Angstrom, c = 20.538(3) Angstrom, beta = 123.51(2)degrees, V = 4028.4 Angstrom(3), d(calcd) = 1.356 g cm(-3), Z = 4. Crystal data for 7 at -70 (d)egrees C: triclinic space group P ($) over bar 1, a = 9.691(2) Angstrom, b = 11.739(2) Angstrom, c = 17.006(3) Angstrom, alpha = 77.63(3)degrees, beta = 75.34(3)degrees, gamma = 72.41(2)degrees, V = 1764.1 Angstrom(3), d(calcd) = 1.624 g cm(-3), Z = 2.