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

摘要: A thermally robust triple-decker complex [bis(η5-pentamethylcyclopentadienyltitanium)-μ-(η4:η4-1,2,4,5-tetrakis(trimethylsilyl)cyclohexa-1-4-diene-3,6-diyl)] (3) was obtained in 4% yield by thermolysing Cp*TiMe3 the presence bis(trimethylsilyl)acetylene (BTMSA). The solid-state structure of centrosymmetric 3 features rather long all C–C bonds nearly planar bridging ligand (1.4720(14)–1.4896(15) A) and a short distance its least-square plane to titanium atoms (1.7381(5) A). Computational results revealed bonding central be accomplished through back-bonding two CC simultaneous generation σ-Ti–C(H) bonds. Based on CASSCF CASPT2 results, molecule acquires several electronic configurations simultaneously, which hinders representation one single Lewis structure. Apart from being coordinated ligand, metal are involved direct Ti–Ti formation σ- δ-bonds between them. bond order this overlap shows only slight decrease upon excitation. ionic contribution is manifested charge −1.4e summed carbon ring. computational spin multiplicity ground state singlet, while first low lying excitation triplet. This agreement with absence EPR signal either toluene solution glass, downfield shifts broadened 1H NMR signals SiMe3 Cp* methyl groups observed increasing temperature.