TY - JOUR
T1 - Diruthenium dithiolato cyanides
T2 - Basic reactivity studies and a post hoc examination of nature's choice of Fe versus Ru for hydrogenogenesis
AU - Justice, Aaron K.
AU - Linck, Rachel C.
AU - Rauchfuss, Thomas B.
PY - 2006/3/20
Y1 - 2006/3/20
N2 - The reaction of Ru2(S2C3H 6)(CO)6 (1) with 2 equiv of Et4NCN yielded (Et4N)2[Ru2(S2C3H 6)(CN)2(CO)4], (Et4N) 2[3], which was shown crystallographically to consist of a face-sharing bioctahedron with the cyanide ligands in the axial positions, trans to the Ru-Ru bond. Competition experiments showed that 1 underwent cyanation >100x more rapidly than the analogous Fe2(S2C 3H6)(CO)6. Furthermore, Ru2(S 2C3H6)(CO)6 underwent dicyanation faster than [Ru2(S2C3H6)(CN)(CO) 5]-, implicating a highly electrophilic intermediate [Ru2(S2C3H6)(μ-CO)(CN)(CO) 5]-. Ru2(S2C3H 6)(CO)6 (1) is noticeably more basic than the diiron compound, as demonstrated by the generation of [Ru2(S 2C3H6)(μ-H)(CO)6]+, [1H]+. In contrast to 1, the complex [1H]+ is unstable in MeCN solution and converts to [Ru2(S2C3H 6)(μ-H)(CO)5(MeCN)]+. (Et4N) 2[3] was shown to protonate with HOAc (pKa = 22.3, MeCN) and, slowly, with MeOH and H2O. Dicyanide [3]2- is stable toward excess acid, unlike the diiron complex; it slowly forms the coordination polymer [Ru2(S2C3H6)(μ-H)(CN) (CNH)(CO)4]n, which can be deprotonated with Et 3N to regenerate [H3]-. Electrochemical experiments demonstrate that [3H]- catalyzes proton reduction at -1.8 V vs Ag/AgCl. In contrast to [3]2-, the CO ligands in [3H]- undergo displacement. For example, PMe3 and [3H]- react to produce [Ru2(S2C3H6)(μ-H)(CN) 2(CO)3(PMe3)]-. Oxidation of (Et4N)2[3] with 1 equiv of Cp2Fe+ gave a mixture of [Ru2(S2C3H 6)(μ-CO)(CN)3(CO)3]- and [Ru 2(S2C3H6)(CN)(CO)5] -, via a proposed [Ru2]2(μ-CN) intermediate. Overall, the ruthenium analogues of the diiron dithiolates exhibit reactivity highly reminiscent of the diiron species, but the products are more robust and the catalytic properties appear to be less promising.
AB - The reaction of Ru2(S2C3H 6)(CO)6 (1) with 2 equiv of Et4NCN yielded (Et4N)2[Ru2(S2C3H 6)(CN)2(CO)4], (Et4N) 2[3], which was shown crystallographically to consist of a face-sharing bioctahedron with the cyanide ligands in the axial positions, trans to the Ru-Ru bond. Competition experiments showed that 1 underwent cyanation >100x more rapidly than the analogous Fe2(S2C 3H6)(CO)6. Furthermore, Ru2(S 2C3H6)(CO)6 underwent dicyanation faster than [Ru2(S2C3H6)(CN)(CO) 5]-, implicating a highly electrophilic intermediate [Ru2(S2C3H6)(μ-CO)(CN)(CO) 5]-. Ru2(S2C3H 6)(CO)6 (1) is noticeably more basic than the diiron compound, as demonstrated by the generation of [Ru2(S 2C3H6)(μ-H)(CO)6]+, [1H]+. In contrast to 1, the complex [1H]+ is unstable in MeCN solution and converts to [Ru2(S2C3H 6)(μ-H)(CO)5(MeCN)]+. (Et4N) 2[3] was shown to protonate with HOAc (pKa = 22.3, MeCN) and, slowly, with MeOH and H2O. Dicyanide [3]2- is stable toward excess acid, unlike the diiron complex; it slowly forms the coordination polymer [Ru2(S2C3H6)(μ-H)(CN) (CNH)(CO)4]n, which can be deprotonated with Et 3N to regenerate [H3]-. Electrochemical experiments demonstrate that [3H]- catalyzes proton reduction at -1.8 V vs Ag/AgCl. In contrast to [3]2-, the CO ligands in [3H]- undergo displacement. For example, PMe3 and [3H]- react to produce [Ru2(S2C3H6)(μ-H)(CN) 2(CO)3(PMe3)]-. Oxidation of (Et4N)2[3] with 1 equiv of Cp2Fe+ gave a mixture of [Ru2(S2C3H 6)(μ-CO)(CN)3(CO)3]- and [Ru 2(S2C3H6)(CN)(CO)5] -, via a proposed [Ru2]2(μ-CN) intermediate. Overall, the ruthenium analogues of the diiron dithiolates exhibit reactivity highly reminiscent of the diiron species, but the products are more robust and the catalytic properties appear to be less promising.
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U2 - 10.1021/ic051989z
DO - 10.1021/ic051989z
M3 - Article
C2 - 16529459
AN - SCOPUS:33645531773
SN - 0020-1669
VL - 45
SP - 2406
EP - 2412
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 6
ER -