HETEROMETALL-ZWEIKERNKOMPLEXE AUS DEN TRIPELDECKERSANDWICH-VERBINDUNGEN BF4 UND CYCLOPENTADIENYLMETALLBISTHIOLATEN. KRISTALLSTRUKTUR UND SPIN-CROSSOVER-VERHALTEN VON t)2Ni(C5H4R)>BF4

Article abstract of DOI:10.1016/0022-328X(85)80394-6

The tripledecker sandwich complex BF4 (I) reacts with (C5H5)2Ti(SR)2 (R=Me, Ph) and (C5H5)2Mo(SR)2 (R=Me, Ph, Bu^t) to produce the dinuclear heterometallic compounds <(C5H5)2M(μ-SR)2Ni(C5H5)>BF4 (V, VI, XI-XIII).The temperature dependence of the 1H NMR spectra of the Ti-Ni complexes V, VI is best explained by an inversion at the sulfur atoms of the bridging SR units which, above +35 deg C, occurs rapidly.The chemical shifts of the 1H and 13C NMR signals of the cyclopentadienyl ligand coordinated to nickel in the compounds <(C5H5)2Mo(μ-SBu^t)2Ni(C5H4R)>BF4 (XIII: R=H, XIV: R=Me) are also strongly temperature-dependent presumably due to an equilibrium between a diamagnetic low-spin and a paramagnetic high-spin isomer.Molecular orbital calculations indicate that the spin crossover is probably a consequence of a flattening at the sulfur atoms caused by the t-butyl substituents.The X-ray structural analysis of XIII shows the presence of a folded four-membered MoS2Ni ring having the t-butyl groups on the inside.In accordance with the MO calculatins, the sulfur atoms are less pyramidal than in analogous complexes.The NMR spectrum of the compound BF4 (XXIII) which is prepared from C5H5(PMe3)Co(SPh)2 and I, does not vary with the temperature.