Directed Synthesis of the Triangular Mixed-Metal Cluster H₂RhRe₂Cp*(CO)₉: Ligand Fluxionality and Facile Cluster Fragmentation in the Presence of CO, Halogenated Solvents, and Thiols

Abstract

The reaction of H2Re2(CO)8 (1) with Cp*Rh(CO)2 (2) in refluxing hexane affords the mixed-metal clusters H2RhRe2Cp*(CO)9 (4, major product), HRh2ReCp*2(CO)6 (5), and HRhRe3Cp*(CO)14 (6). 4 and 5 are electron-precise 48e clusters and display triangular metallic cores, while 6 contains 64 valence electrons and exhibits a spiked-triangular core having a pendant Re(CO)5 moiety. Heating 1 with Cp*2Rh2(CO)2 (3) gives 4 and 5 as the principal products, in addition to H2Rh2Re2Cp*2(CO)8 (7) in low yield. Cluster 7 possesses 60e and contains a tetrametallic core with two face-capping CO and hydride groups. Heating 4 under CO leads to cluster fragmentation and formation of Re2(CO)10 and 2 in essentially quantitative yield, as assessed by IR spectroscopy. The kinetics for the fragmentation of 4 in toluene under CO have been investigated over the temperature range 325−349 K by UV−vis spectroscopy. On the basis of the first-order rate constants and the Eyring activation parameters (ΔH ⧧ = 25.0(8) kcal/mol; ΔS ⧧ = −2.6(3) eu), a rate-limiting step involving a polyhedral opening of 4 is supported. 4 is thermally and photochemically sensitive, and reactions conducted in the presence of chlorinated solvents furnish the face-shared bioctahedral compound Cp*Rh(μ-Cl)3Re(CO)3 (8). Heating 4 and H2S in benzene at ca. 60 °C furnishes the 48e triangular cluster S2Rh3Cp*(CO)4 (9), which contains two Rh(CO)2 moieties and two face-capping sulfide groups. The reaction of 4 with p-methylbenzenethiol gives the sulfido-bridged dimer Cp*Rh(μ-SC6H4Me-p)3Re(CO)3 (11). The dinuclear compounds Cp*Rh(μ-Cl)(μ-SC6H4Me-p)2Re(CO)3 (10) and 11 are formed when 8 is allowed to react with p-methylbenzenethiol. Treatment of 8 and 10 with excess p-methylbenzenethiol yields 11 at elevated temperature in toluene. Compounds 4−11 have been isolated and fully characterized by IR and NMR spectroscopy and by X-ray crystallography. The reactivity displayed by 4 is contrasted with that of the known indenyl-substituted cluster H2Re2Ir(η5-ind)(CO)9 prepared earlier by Shapley and co-workers.

DFT Investigation of the Mechanism of Phosphine-Thioether Isomerization in the Triosmium Cluster Os3(CO)10(Ph2PCH2CH2SMe): Migratory Preference for the Formation of an Edge-Bridged Thioether versus a Phosphine Moiety

“…Scheme outlines this first exchange step, where the conrotatory motion of the six migrating groups furnishes the bridging isomer A2 ; here the thioether moiety is transformed from an initial equatorial position in A1 to an axial site at the cluster. This in-plane migration represents a prevalent manifold for the exchange of CO and phosphine ligands between adjacent metal centers in polynuclear metal clusters. − , Figures and show the geometry-optimized structures and the potential energy surface for the conversion of 1,2-( P eq , S eq )-Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe) to 1,1-( P eq , S ax )-Os 3 (CO) 10 (Ph 2 PCH 2 CH 2 SMe). The transition state TSA1A2 lies 10.9 kcal/mol higher in energy than the starting species A1 , and the product species, A2 , is only marginally less stable than the starting cluster, lying 0.8 kcal/mol above A1 .…”

Bis(hydrosulfido)-bridged dinuclear rhodium(i) complexes as a platform for the synthesis of trinuclear sulfido aggregates with the core [MRh2(μ3-S2)] (M = Rh, Ir, Pd, Pt, Ru)

“…Related precedents for sulfido-bridged IrRh 2 and Rh 3 compounds are [Cp*(PMe 3 )Ir(μ 3 -S) 2 Rh 2 (cod) 2 ], 20 which was prepared from the bis-hydrosulfido mononuclear complex [Cp*Ir-(SH) 2 (PMe 3 )], and [Cp*Rh(μ 3 -S) 2 Rh 2 (CO) 4 ] obtained by thermolysis of a triangular RhRe 2 cluster in the presence of H 2 S(g). 21 The molecular structure of 3 has been determined by X-ray analysis and it is shown in Fig. 1.…”

“…4 ] obtained by thermolysis of a triangular RhRe 2 cluster in the presence of H 2 S (g). 21 The molecular structure of 3 has been determined by X-ray 50 analysis and it is shown in Figure 1. 3 features an almost isosceles Rh 3 triangle capped, at both sides, by two triply bridging sulfido ligands, with a mean distance between the sulfur atoms and the trimetallic plane of 1.5438(5) Å, resulting in a trigonal bipyramidal Rh 3 S 2 core.…”

E–H Bond Activation and Insertion Processes in the Reactions of the Unsaturated Hydride [W2Cp2(μ-H)(μ-PPh2)(NO)2]

“…Since the chemistry of the latter complexes has not been studied in detail, it was of interest to explore the chemical behavior of 1 in a wide sense . From an electronic point of view, compound 1 can be related to different carbonyl complexes bearing the very reactive 32-electron M 2 (μ-H) 2 core, such as [Os 3 (μ-H) 2 (CO) 10 ], [Re 2 (μ-H) 2 (CO) 8 ], and [Mn 2 (μ-H) 2 (CO) 6 (μ-L 2 )], all of which proved to be very reactive toward a great variety of organic and inorganic molecules under mild conditions. From a structural point of view, however, compound 1 is related more closely to the 30-electron carbonyl hydrides [M 2 Cp 2 (μ-H)­(μ-PCy 2 )­(CO) 2 ] (M = Mo, W), which also display a wide and remarkable reactivity. , In this paper we report our results on the reactions of 1 with several p-block-element (E) molecules bearing E–H bonds, such as BH 3 ·THF, HSnPh 3 , HSPh, and ( p -tol)­C­(O)­H, in order to examine its oxidative addition and dehydrogenation chemistry.…”