A series of sterically varied titanium alkoxides [[Ti(OR)(4)](n)(), n = 4, OR = OCH(2)CH(3) (OEt); n = 1, OCH(CH(3))(2) (OPr(i)); n = 2, OCH(2)C(CH(3))(3) (ONep); n = 1, OC(6)H(3)(CH(3))(2)-2,6 (DMP)] were reacted with a series of thallium alkoxides [[Tl(OR)](x) (x = 4, OR = OEt, ONep; n = infinity, DMP)]. The resultant products of the [Tl(mu(3)-OEt)](4)-modified [Ti(OR)(4)](n)() (OR = OEt, OPr(i), ONep) were found by X-ray analysis to be Tl(4)Ti(2)(mu-O)(mu(3)-OEt)(8)(OEt)(2) (1), Tl(4)Ti(2)(mu-O)(mu(3)-OPr(i))(5)(mu(3)-OEt)(3)(OEt)(2) (2), and TlTi(2)(mu(3)-OEt)(2)(mu-OEt)(mu-ONep)(2)(ONep)(4) (3), respectively. The reaction of [Tl(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 TlTi(2)(mu(3)-OEt)(mu(3)-ONep)(mu-OEt)(mu-ONep)(2)(ONep)(4) (4). Compounds 1 and 2 possess an octahedral (Oh) arrangement of two Ti and four Tl metal atoms around a mu-O central oxide atom (the Tl-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 Tl atoms are formally 4-coordinated, adopting a distorted pyramidal geometry using four mu(3)-OR (OR = OEt or OPr(i)) ligands to complete their coordination sphere. The Tl atoms reside approximately 1.4 A 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 Tl cation is in a formal distorted pyramidal (PYD) arrangement. If the lone pair of the Tl cations are considered in the geometry, each Tl adopts a square base pyramidal geometry. Two terminal ONep ligands are bound to each Ti with the remainder of the molecule consisting of mu(3)- and mu-ONep ligands. The reaction of [Tl(mu(3)-ONep)](4) with two equivalents of [Ti(mu-ONep)(ONep)(3)](2) also led to the isolation of the homoleptic trinuclear complex TlTi(2)(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 Tl is PYD bound by ONep ligands. A further increase in the steric bulk of the pendant ligands, using [Tl(mu-DMP)](infinity) and [Ti(mu-ONep)(ONep)(3)](2), resulted in a further decrease in the nuclearity yielding the dinuclear species TlTi(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 Tl 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 [Tl(mu-DMP)](infinity) led to the formation of [Tl(+)][(-)(eta(2-3)-DMP)Ti(DMP)(4)] (7). The Ti metal center is in a TBP geometry, and the "naked" Tl cation resides unencumbered by solvent molecules but was found to have a strong pi-interaction with four DMP ligands of neighboring...

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[Tl(OCH2Me)]4 (1) was reacted with excess HOR to prepare a series of [Tl(OR)]n, where OR = OCHMe2 (2, n = 4), OCMe3 (3, n = 4), OCH2CMe3 (4, n = 4), OC6H3(Me)2-2,6 (5, n = infinity), and OC6H3(CHMe2)2-2,6 (6, n = infinity). Single-crystal X-ray diffraction experiments revealed that in the solid state the alkoxide-ligated compound 4 adopts a cubane structure, whereas the aryloxide derivatives, 5 and 6, formed polymeric chains. Compounds 1-6 were also characterized by 203,205Tl solution and 205Tl solid-state NMR spectroscopy. In solution it was determined that 1-4 retained the [Tl-O]4 cube structure, whereas the polymeric species 5 and 6 appeared to be fluxional. Variations in the solution and solid-state structures for the [Tl(OR)]4 cubes and polymeric [Tl(OAr)]infinity are influenced by the steric hindrance of the ligand. The acidity of the parent alcohol influences the degree of covalency at the Tl metal center, which is reflected in the 203,205Tl chemical shifts for 1-6.

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The reaction of [Sn(NMe(2))(2)](2) (1) with 4 equiv of HOCH(2)CMe(3) (HONep) leads to the isolation of [Sn(ONep)(2)](infinity) (2). Each Sn atom is four coordinated with mu-ONep ligands bridging the metal centers; however, if the free electrons of the Sn(II) metal center are considered, each Sn center adopts a distorted trigonal bipyramidal (TBP) geometry. Through (119)Sn NMR experiments, the polymeric compound 2 was found to be disrupted into smaller oligomers in solution. Titration of 2 with H(2)O led to the identification of two unique hydrolysis products characterized by single-crystal X-ray diffraction as Sn(5)(mu(3)-O)(2)(mu-ONep)(6) (3) and Sn(6)(mu(3)-O)(4)(mu-ONep)(4) (4). Compound 3 consists of an asymmetrical molecule that has five Sn atoms arranged in a square-based pyramidal geometry linked by four basal mu-ONep ligands, two facial mu(3)-O, and two facial mu-ONep ligands. Compound 4 was solved in a novel octahedral arrangement of six Sn cations with an asymmetric arrangement of mu(3)-O and mu-ONep ligands that yields two square base pyramidal and four pyramidal coordinated Sn cations. These compounds were further identified by multinuclear ((1)H, (13)C, (17)O, and (119)Sn) solid-state MAS and high resolution, solution NMR experiments. Because of the complexity of the compounds and the accessibility of the various nuclei, 2D NMR experiments were also undertaken to elucidate the solution behavior of these compounds. On the basis of these studies, it was determined that while the central core of the solid-state structures of 3 and 4 is retained, dynamic ligand exchange leads to more symmetrical molecules in solution. Novel products 3 and 4 lend structural insight into the stepwise hydrolysis of Sn(II) alkoxides.