Heterometall-Zweikernkomplexe aus den Tripeldeckersandwich-Verbindungen [Ni2(C5H4R)3]BF4 und Cyclopentadienylmetallbisthiolaten: Kristallstruktur und Spin-Crossover-Verhalten von [(C5H5)2Mo(μ-SBut)2Ni(C5H4R)BF4

Abstract The tripledecker sandwich complex [Ni 2 (C 5 H 5 ) 3 ]BF 4 (I) reacts with (C 5 H 5 ) 2 Ti(SR) 2 (R = Me, Ph) and (C 5 H 5 ) 2 Mo(SR) 2 (R = Me, Ph, Bu t ) to produce the dinuclear heterometallic compounds [(C 5 H 5 ) 2 M(μ-SR) 2 Ni(C 5 H 5 )]BF 4 (V, VI, XI–XIII). The temperature dependence of the 1 H 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°C, occurs rapidly. The chemical shifts of the 1 H and 13 C NMR signals of the cyclopentadienyl ligand coordinated to nickel in the compounds [(C 5 H 5 ) 2 Mo(μ-SBu t ) 2 Ni(C 5 H 4 R)]BF 4 (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 bulky t-butyl substituents. The X-ray structural analysis of XIII shows the presence of a folded four-membered MoS 2 Ni ring having the t-butyl groups on the inside. In accordance with the MO calculations, the sulfur atoms are less pyramidal than in analogous complexes. The NMR spectrum of the compound [C 5 H 5 (PMe 3 )Co(μ-SPh) 2 NiC 5 H 5 ]BF 4 (XXIII) which is prepared from C 5 H 5 (PMe 3 )Co(SPh) 2 and I, does not vary with the temperature.