From clusters to ionic complexes: Structurally characterized thallium titanium double alkoxides

A series of sterically varied titanium alkoxides {[Ti(OR)(4)](n), n = 4, OR = OCH2CH3 (OEt); n = 1, OCH(CH3)(2) (OPri); n = 2, OCH2C(CH3)(3) (ONep); n = 1, OC6H3(CH3)(2)-2,6 (DMP)} were reacted with a sexes of thallium alkoxides {[TI(OR)](x) (x = 4, OR = OEt, ONep; n = infinity, DMP)}. The resultant products of the [TI(mu(3)-OEt)](4)-modified [Ti(OR)(4)](n), (OR = OEt, OPrI, ONep) were found by X-ray analysis to be Tl4Ti2(mu-O)(mu(3)-OEt)(8)(OEt)(2) (1), Tl4Ti2(mu-O)(mu(3)-OPr\)(5)(mu(3)-OEt)(3)(OEt)(2) (2), and TITi2(mu(3)-OEt)(2)(mu-OEt)(mu-ONeP)(2)(ONeP)(4) (3), respectively. The reaction of [TI(mu(3)-OEt)](4), 12HOEt, and 4[Ti(mu-ONep)ONeP)(3)](2) to generate 3 in a higher yield resulted in the isolation of TITi2(mu(3)-OEt)(mu(3)-ONep)(mu-OEt)(mu-ONeP)(2)(ONeP)(4) (4). Compounds I and 2 possess an octahedral (Oh) arrangement of two Ti and four TI metal atoms around a mu-O central oxide atom (the TI-O distance is too long to be considered a bond). For both compounds, each Ti atom adopts a distorted Oh geometry with one terminal OEt ligand, The TI atoms are formally 4-coordinated, adopting a distorted pyramidal geometry using four mu(3)-OR (OR = OEt or OPri) ligands to complete their coordination sphere. The TI atoms reside similar to1.4 Angstrom below the basal plane of oxygens. In contrast to these structures, both 3 and 4 utilize ONep ligands and display reduced oligomerization yielding trinuclear complexes without oxo formation. The two Ti cations are Oh, and the single TI cation is in a formal distorted pyramidal (PYD) arrangement. If the lone pair of the TI cations are considered in the geometry, each TI adopts a square base pyramidal geometry. Two terminal ONep ligands are bound to each Ti with the remainder of the molecule consisting of mu3- and mu-ONep ligands. The reaction of [TI(mu(3)-ONep)](4) with two equivalents of [Ti(mu-ONep)(ONeP)(3)](2) also led to the isolation of the homoleptic trinuclear complex TITi2(mu(3)-ONeP)(2)(mu-ONep)(3)(ONeP)(4) (5) which is analogous in structure to the mixed ligand species of 3 and 4. Each Ti is Oh coordinated with six ONep ligands, and the single TI is PYD bound by ONep ligands, A further increase in the steric bulk of the pendant ligands, using [TO(mu-DMP)](infinity) and [Ti(mu-ONep)(ONep)(3)](2), resulted in a further decrease in the nuclearity yielding the dinuclear species TITi(mu-DMP)(mu-ONep)(DMP)(ONeP)(2) (6). For 6, the two metals are bound by a mu-ONep and a mu-DMP ligand. The TI metal center was solved in a bent geometry while the Ti adopted a distorted trigonal bipyramidal (TBP) geometry using three ONep and two DMP ligands to fill its coordination sphere. Further increasing the steric bulk of the ancillary ligands using Ti(DMP)(4) and [TI(mu-DMP)](infinity) led to the formation of [TI+][(-)(eta(2-3)-DMP)Ti(DMP)(4)] (7). The Ti metal center is in a TBP geometry, and the "naked" TI cation resides unencumbered by solvent molecules but was found to have a strong pi-interaction with four DMP ligands of neighboring Ti(DMP)(5)(-) anions. For this novel set of compounds, (TI)-T-205 NMR spectroscopy was used to investigate the solution behavior of these compounds. Multiple (TI)-T-205 resonances were observed for the solution spectra of the crystalline material of 1-6, and a broad singlet was observed for 7. The large number of minor resonances noted for these compounds was attributed to sensitivity of the TI cation based on small variations due to ligand rearrangement. However, the major resonance noted in the (TI)-T-205 NMR solution spectra of 1-7 are in agreement with their respective solid-state structures.