MONO(PENTAMETHYLCYCLOPENTADIENYL)THORIUM CHEMISTRY - FORMATION AND STRUCTURAL CHARACTERIZATION OF A NOVEL TRIFLATE-BRIDGED DIMERIC THORIUM COMPLEX

Reaction of [(Me(3)Si)(2)N]Th-2[N(SiMe(3))(SiMe(2)CH(2))] (1) with 1 equiv of trifluoromethanesulfonic acid (HOTf) produces the mono(triflate) species Th[N(SiMe(3))(2)](3)(OTf) (2), whereas the reaction of 1 with 2 equiv of HOTf yields both 2 and the tris(triflate) complex Th[N(SiMe(3))(2)](OTf)3 (3) in approximately equal amounts. Heating a toluene solution of 2 with 1 equiv of Cp*H (Cp* = C(5)Me(5)) leads to formation of the dimeric triflate-bridged complex Cp*[(Me(3)Si)(2)N]Th(mu 2-OSO2CF3)(3)Th[N(SiMe(3))(SiMe(2)Ch(2))]Cp* (4). Reaction of 4 with 1 equiv of KN(SiMe(3))(2) produces the dimeric species {Cp*(TfO)Th[N(SiMe(3))(SiMe(2)CH(2))]}(2) (5). Compounds 2-5 have been characterized by H-1 NMR and IR spectroscopy, elemental analysis, and, in the case of 4, by a single-crystal X-ray diffraction study. Compound 4 consists of two mono(pentamethylcyclopentadienyl)thorium moieties (Th-Cp*(centroid) = 2.54 and 2.51 Angstrom) joined by means of three bridging triflate ligands. One thorium metal center bears a bis(trimethylsilyl)amide ligand (Th-N = 2.24(3) Angstrom) while the other features a cyclometalated amide ligand (Th-N = 2.26(4) Angstrom, Th-C = 2.43(5) Angstrom). A tentative mechanism is proposed for the formation of 4. Crystal data for 4 at -70 degrees C: monoclinic space group P2(1)/n, a = 14.073(3) Angstrom, b = 23.242(5) Angstrom, c = 18.101(4) Angstrom, beta = 105.70(3)degrees, V = 5699.5 Angstrom(3), d(calcd) = 1.806 g cm(-3), Z = 4.