Preparation of Cationic Dinuclear Hydrido Complexes of Ruthenium, Rhodium, and Iridium with Bridging Thiolato Ligands and Their Reactions with Nitrosobenzene

A series of cationic dinuclear hydrido complexes with bridging thiolato ligands [Cp*MH(μ-SPri)2MCp*][OTf]
(4, M = Ru; 6a, M = Rh; 7a, M = Ir; Cp* = η5-C5Me5, OTf = OSO2CF3) were synthesized by treatment of the
corresponding chloro complexes [Cp*RuCl(μ-SPri)2Ru(OH2)Cp*][OTf] (1) or [Cp*M(μ-Cl)(μ-SPri)2MCp*][OTf]
(2, M = Rh; 3, M = Ir) with HSiEt3. The dirhodium and diiridium complexes 6 and 7 have been shown to
possess a bridging hydrido ligand by crystallographic analysis, while the diruthenium complex 4 is proposed to
have a terminal hydrido ligand that undergoes facile migration between the two ruthenium centers in solution.
Complexes 4, 6a, and 7a reacted with nitrosobenzene to give the paramagnetic dinuclear nitrosobenzene complexes
[Cp*M(μ-PhNO)(μ-SPri)2MCp*]+ (M = Ru, Rh, Ir) along with azoxybenzene. The molecular structures of the
three nitrosobenzene complexes have been determined by X-ray diffraction study to reveal that in each case
nitrosobenzene acts as a μ-η1:η1-N,O ligand. Judging from the molecular structures and the ESR spectra, the
unpaired electron is considered to be located mainly on the nitrosobenzene ligand, at least in the diruthenium and
dirhodium complexes. On the other hand, complex 2 reacted with nitrosobenzene to give the incomplete cubane-type trinuclear cluster [(Cp*Rh)3(μ-Cl)2(μ3-S)(μ-SPri)]+, whose molecular structure has also been determined
crystallographically.