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On the Synthesis and Chemical Behaviour of the Elusive Bis(hydrosulfido)‐Bridged Dinuclear Rhodium(I) Complexes [{Rh(μ‐SH)(CO)(PR 3 )} 2 ]
Author(s) -
PérezTorrente Jesús J.,
Jiménez M. Victoria,
HernandezGruel Marc A. F.,
Fabra María J.,
Lahoz Fernando J.,
Oro Luis A.
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902249
Subject(s) - rhodium , chemistry , stereochemistry , cluster (spacecraft) , molecule , medicinal chemistry , crystallography , catalysis , organic chemistry , computer science , programming language
Several bis(hydrosulfido)‐bridged dinuclear rhodium(I) compounds, [{Rh(μ‐SH)(L) 2 } 2 ], have been prepared from rhodium(I) acetylacetonato complexes, [Rh(acac)(L) 2 ], and H 2 S(g). Reaction of [Rh(acac){P(OPh) 3 } 2 ] with H 2 S(g) affords the dinuclear bis(hydrosulfido)‐bridged compound [{Rh(μ‐SH){P(OPh) 3 } 2 } 2 ] ( 1 ). However, reaction of complexes [Rh(acac)(CO)(PR 3 )] with H 2 S(g) gives the dinuclear compound [{Rh(μ‐SH)(CO)(PR 3 )} 2 ] (R=Cy, 2 ; R=Ph, 4 ) and the trinuclear cluster [Rh 3 (μ‐H)(μ 3 ‐S) 2 (CO) 3 (PR 3 ) 3 ] (R=Cy, 3 ; R=Ph, 5 ). The selective synthesis of both type of compounds has been carried out by control of the H 2 S(g) concentration in the reaction media. The trinuclear hydrido–sulfido cluster [Rh 3 (μ‐H)(μ 3 ‐S) 2 (CO) 3 (PPh 3 ) 3 ] ( 5 ) has been also obtained by reaction of [{Rh(μ‐SH)(CO)(PPh 3 )} 2 ] ( 4 ) with [Rh(acac)(CO)(PPh 3 )], proceeding through the trinuclear hydrosulfido–sulfido intermediate [Rh 3 (μ 3 ‐SH)(μ 3 ‐S)(CO) 3 (PPh 3 ) 3 ]. The molecular structures of complexes 1 and 3 have been determined by X‐ray diffraction methods. Compound 1 is stable in solution, but complexes 2 and 4 slowly transform in solution into the trinuclear hydrido–sulfido clusters 3 and 5 , respectively, with the release of H 2 S(g) in a reversible way. 1 H NMR kinetic experiments for the transformation of 4 into 5 have revealed that this transformation follows second‐order‐type kinetic. The following activation parameters, Δ H ≠ =24±3 kJ mol −1 and of Δ S ≠ =−223±8 J K −1 mol −1 , have been calculated from the determination of the second‐order rate constants in the temperature range 30–45 °C. The large negative value of the activation entropy is consistent with an associative character of the rate‐determining step. A plausible multistep mechanism based on the chemical behaviour of hydrosulfido–metal complexes and compatible with the kinetic behaviour has been proposed.