Re 2 (µ-H)(µ-SH)(CO) 8 ] 1 reacted with [Re 2 (CO) 8 (MeCN) 2 ], [Os 3 (CO) 11 (MeCN)], [Co 2 (CO) 8 ] and [Fe 2 (CO) 9 ], respectively, by SH oxidative addition to give the spirocyclic cluster complexes [{Re 2] 5 in good yields. Complexes 2, 3 and 4 have been characterised by crystal structure analysis. Cluster complex 2 consists of two hydrido bridged dirhenium octacarbonyl units linked by a tetrahedral µ 4 -S. The crystal structure of 3 shows an analogous Re 2 unit and a planar Os 3 ring linked by a tetrahedral µ 4 -S. Cluster complex 4 consists of one Fe 2 and two Re 2 units linked into a chain by two tetrahedral µ 4 -S bridges. The structure of 5 is similar to that of 4 and was derived from spectroscopic data and elemental analysis. The formation of 3 was shown to proceed in two steps. First the acetonitrile ligand in [Os 3 (CO) 11 (MeCN)] is substituted by 1 followed by SH oxidative addition giving the intermediate [(OC) 8 (µ-H)Re 2 (µ 3 -S)Os 3 (µ-H)(CO) 11 ] 6. Upon heating the cluster complex eliminates one equivalent of CO yielding 3 as the final product. The molecular structure of 6 has been established by single crystal X-ray analysis.

The reaction of [PPN][Os3(μ-PR2)(CO)10] (R = Ph 1a, i-Bu 1b) with HgCl2 in THF at −90 °C under exclusion of light gave the spirocyclic cluster μ4-Hg[Os3(μ-PR2)(μ-CO)(CO)9]2 (R = Ph 2a, i-Bu 2b). In these compounds the μ4-Hg bridges one Os−Os edge of each Os3 subunit. The remaining four edges are bridged by the μ-CO and μ-PPh2 ligands, respectively. 13C NMR spectra of 13CO-enriched 2a recorded at room temperature indicate an intramolecular rotation of the Os3 subunits around the axis running through the mercury atom and the midpoints of the Os−Os vectors it bridges. When 2a is heated in toluene or 1,4-dioxane, a rearrangement of the metal skeleton takes place. The μ4-Hg moiety is shifted to another edge of one of the Os3 rings, giving the isomer (CO)10(μ-PPh2)Os3(μ4-Hg)Os3(μ-PPh2)(μ-CO)(CO)9, 3a. The kinetics of this process were measured by UV/vis spectroscopy at four different temperatures in toluene and 1,4-dioxane, respectively. The reaction is of first order with a rate constant of 6.66(2) × 10-5 s-1 in toluene at 331.6(1) K. The thermodynamic parameters ΔH ⧧ = 97(5) kJ mol-1, ΔS ⧧ = −33(13) J K-1 mol-1, and ΔG ⧧ = 107(6) kJ mol-1 were derived from an Eyring plot. The analogous cluster complex 3b with μ-P(i-Bu)2 bridges has been obtained, too. Its structure has been confirmed by single-crystal X-ray analysis. 2a and 2b are highly photosensitive in solution. Upon exposure to daylight, they rearrange to give the novel wheel-shaped cluster complexes Os6(μ6-Hg)(μ-PR2)2(CO)20 (R = Ph 4a, i-Bu 4b). The structure of 4a was confirmed by single-crystal X-ray analysis. In 4a the Hg atom is located at the center of a Os6 ring. The ring is corrugated with the mercury atom in bonding distance to all osmium atoms. The course of the reaction was monitored for the conversion of 2a by UV/vis spectra exhibiting two isosbestic points indicating an intramolecular reaction.

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In the course of our studies of trinuclear osmium cluster complexes with bridging sulfido and hydrido ligands, the new compounds Os3(μ‐H)(μ‐SR)(CO)9(PHCy2) (Cy = cyclo­hexyl) with R = phenyl, (I) (nona­carbonyl‐1κ3C,2κ3C,3κ3C‐di­cyclo­hexyl­phosphine‐3κP‐μ‐hydrido‐1:2κ2H‐μ‐phenyl­thio‐1:2κ2S‐triangulo‐triosmium), [Os3H(C6H5S)(C12H23P)(CO)9], and R = naphthyl, (II) [nona­carbonyl‐1κ3C,2κ2C,3κ4C‐di­cyclo­hexyl­phosphine‐2κP‐μ‐hydrido‐1:2κ2H‐μ‐(2‐naphthyl­thio)‐1:2κ2S‐triangulo‐triosmium], [Os3H(C10H7S)(C12H23P)(CO)9], were prepared. We report on these two phosphine‐substituted complexes, which exhibit perceptible changes of the Os—Os bond parameters due to the ligand‐substitution pattern.