Synthesis, molecular and electronic structure of a stacked half-sandwich dititanium complex incorporating a cyclic p-faced bridging ligand

0464377 - ÚFCH JH 2017 RIV GB eng J - Článek v odborném periodiku
Gyepes, R. - Pinkas, Jiří - Císařová, I. - Kubišta, Jiří - Horáček, Michal - Mach, Karel
Synthesis, molecular and electronic structure of a stacked half-sandwich dititanium complex incorporating a cyclic p-faced bridging ligand.
RSC Advances. Roč. 6, č. 96 (2016), s. 94149-94159. E-ISSN 2046-2069
Grant CEP: GA ČR(CZ) GAP207/12/2368
Institucionální podpora: RVO:61388955
Klíčová slova: atoms * carbon * electronic structure
Kód oboru RIV: CF - Fyzikální chemie a teoretická chemie
Impakt faktor: 3.108, rok: 2016

A thermally robust triple-decker complex [bis(h5-pentamethylcyclopentadienyltitanium)-m-(h4:h4-1,2,4,5-
tetrakis(trimethylsilyl)cyclohexa-1-4-diene-3,6-diyl)] (3) was obtained in 4% yield by thermolysing
Cp*TiMe3 in the presence bis(trimethylsilyl)acetylene (BTMSA). The solid-state structure of
centrosymmetric 3 features rather long all C–C bonds in the nearly planar bridging ligand (1.4720(14)–
1.4896(15) °A) and a short distance of its least-square plane to the titanium atoms (1.7381(5) °A).
Computational results revealed the bonding of the central ligand to be accomplished through backbonding
of its two C]C bonds and through the simultaneous generation of two s-Ti–C(H) bonds.
Based on CASSCF and CASPT2 results, the molecule acquires several electronic configurations
simultaneously, which hinders its representation by one single Lewis structure. Apart from being
coordinated to the central ligand, the metal atoms are involved in a direct Ti–Ti bonding by the
formation of one s- and two d-bonds between them. The bond order of this Ti–Ti overlap shows only
a slight decrease upon electronic excitation. The presence of ionic contribution to the bonding of the
central ligand is manifested by the charge 1.4e summed on the carbon atoms of the bridging ring.
Based on computational results, the spin multiplicity of the ground state is singlet, while the first low
lying excitation state is triplet. This is in agreement with the absence of EPR signal in either toluene
solution and glass, and with slight downfield shifts of broadened 1H NMR signals of SiMe3 and Cp*
methyl groups observed with increasing temperature.
Trvalý link: http://hdl.handle.net/11104/0263281