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 EC 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 spectroscopies and by X-ray crystallography.
The reactivity displayed by 4 is contrasted with the known indenyl-substituted cluster
H2Re2Ir(η5-ind)(CO)9 prepared earlier by Shapley and co-workers.
