Direct proof of the molecular structure of dimeric titanocene; The X-ray structure of μ(η5:η5-fulvalene)-di-(μ-hydrido)-bis(η5-cyclopentadienyltitanium)· 1.5 benzene

Bis(η5-cyclopentadienyl)titanium(II) in the gas phase:

“…The experimental geometrical parameters of 6 [10] are well reproduced by the calculation presented in this study. The only significant exception is the Ti-Ti distance, which was found shorter than the experimental value of 2.989 Å [10] by 0.112 Å .…”

“…The only significant exception is the Ti-Ti distance, which was found shorter than the experimental value of 2.989 Å [10] by 0.112 Å . It should be noted that also the calculated Ti-H bond lengths and Ti-H-Ti and H-Ti-H angles were found notably different from the X-ray data.…”

“…However, these differences can be attributed to the inaccuracy of the determination of hydrogen atom positions from X-ray data and to the fact that the experimental molecular structure of 6 was determined from the titanocene dimer cocrystallized with 1.5 equiv. of benzene [10], whereas the calculated structure corresponds to 6 in the gas phase. The calculated energy of reaction (2) is 48 kJ mol À1 and the elimination of dihydrogen from 10 giving rise to 6 (reaction (3)) is 91 kJ mol À1 exothermic.…”

“…However, their bright green ''titanocene'' appeared to be a dimer with the fulvalene ligand and two (l-hydrido) bridges connecting titanium atoms. Strong evidence for dimeric structure was given by Brintzinger and Bercaw [6], the presence of fulvalene moiety was established by the 13 C NMR [7] and by the X-ray crystallographic studies of various derivatives of the titanocene dimer [8,9], and finally, a direct proof provided the X-ray structure solved by Mach et al [10]. A clear conclusion has been drawn from numerous experimental studies, that in spite of extensive effort devoted to its preparation and characterization, the free titanocene is obviously not isolable [11], and as such it remained the last experimentally unknown metallocene in the 3d series transition metals.…”

Fulvalene titanium and zirconium complexes: synthesis and NMR study of phosphanido-, alkyl-, and alkynyl-derivatives. X-ray crystal structures of [{Ti(η5−C5H5)(μ−PPH2)}2{μ−(η5−C5H4−η5−C5H4)}] and [{Zr(η5−C5H5)(μ−C≡CSiMe3)}2{μ−(η5−C5H4−η5−C5H4)}]

“…The structures of [{TiCp(/z-X)}2{/x-(~75-CsH4-r/5-C5H4)}] (X = H, O, or Cl) were reviewed when the structure of the di-hydrido compound was determined [13]. It was found that all of the structures have the same form.…”