Synthesis and structure of titanium(III) tweezer complexes with embedded alkali metal ions: [(eta(5)-CHMe(4))(2)Ti(eta(1)-C CSiMe(3))(2)](-)M(+) (M=Li,Na,K and Cs)

Complexes [(eta(5)-C(5)HMe(4))(2)Ti(eta(1)-C=CSiMe(3))(2)](-)M(+) (M = Li (2), Na (3), K (4), and Cs (5)) were prepared by the redox reaction of (eta(5)-C(5)HMe(4))(2)Ti(eta(1)-C=CSiMe(3))(2) (1) with the alkali metals in toluene. The X-ray crystal analysis of 4 (monoclinic, P2(1)/c, a = 10.888(3) Angstrom, b = 18.047(8) Angstrom, c = 16.562(3) Angstrom, beta = 104.10(2)degrees, Z = 4) revealed a tweezer structure with the potassium cation embedded between the trimethylsilylacetylide tweezer arms in a position which is slightly closer to the inner acetylide carbon atoms (2.946(4) Angstrom and 2.949(4) Angstrom) than to the outer ones (3.021(4) Angstrom and 2.961(4) Angstrom). The K+ ion simultaneously binds a C(5)HMe(4) ligand of the adjacent molecule at the K-centroid distance of 3.186(5) Angstrom, thus forming a polymer chain arrangement of molecular units. The complexes 2-5 afford characteristic EPR spectra (g = 1.9924-1.9935, Delta H = 2.0-2.4 G, a(Ti) = 7.8-8.4 G), infrared (v(C=C) at 1935-1948 cm(-1)) and UV-vis spectra (two CT bands in the region 355-390 nm). The molecular ions of 2-5 were observed in EI mass spectra.