Formic acid modified Ti(OCHMe2)4.: Syntheses, characterization, and X-ray structures of Ti4(μ4-O)(μ-O)(OFc)2(μ-OR)4(OR)6 and Ti6(μ3-O)6(OFc)6(OR)6 (OFc = O2CH; OR = OCHMe2)

Novel structural arrangements for carboxylic acid modified titanium alkoxides were obtained from, stoichiometric reactions between titanium isopropoxide (Ti(OPri)(4)) and formic acid (HOFc). The 1:1 reaction in toluene forms the tetranuclear species Ti4O2(OFc)(2)(OPri)(10), 1. The structure of 1 was solved in the triclinic space group P (1) over bar with a = 13.034(3) Angstrom, b = 13.467(2) Angstrom, c = 13.996(2) Angstrom, alpha = 98.79(1)degrees, beta = 104.68(2)degrees, and gamma = 97.82(2)degrees for Z = 2. The general structure of 1 resembles two face-shared [Ti-O](4) cubes with one set of mirror-related titanium atoms removed. The oxygen atoms are represented by one mu(4)-O, one mu-O, and four mu-OR ligands, with the remaining sires filled by two OFc ligands and six terminal alkoxides, Increasing the stoichiometry to 1:2 (Ti/HOFc) leads to the isolation of Ti6O6(OFc)(6)(OR)(6), 2. The structure of 2 was solved in the monoclinic space group P2(1)/c with a = 8.968(2) Angstrom, b = 26.520(4) Angstrom, c = 20.046(2) Angstrom, and beta = 93.19(1)degrees for Z = 4. The structure of 2 consists of two offset six-membered [Ti-(mu(3)-O)](3) rings joined through Ti-O bonds. The OFc ligands are arranged externally around the central hexagon-prism, oscillating between the top and bottom rings. Compound 1 adopts a very symmetrical arrangement in solution due to the labile OFc ligands and was found to undergo "aging" by a trans-esterification mechanism, the rate of which is enhanced by heating. Compound 2 maintains its solid-state structure in solution.