Sulfido-Persulfido Equilibria in Sulfur-Rich Metal Clusters: The Case of (C(5)Me(5))(3)RhRu(2)S(4)(2+).
The reaction of [(C(5)Me(5))M(MeCN)(3)](PF(6))(2) with (C(5)Me(5))(2)Ru(2)S(4) gives the cluster compounds [(C(5)Me(5))(3)MRu(2)S(4)(MeCN)](PF(6))(2), 1(PF(6))(2) (M = Rh) and 3(PF(6))(2) (M = Ir). Crystallographic studies of 1(PF(6))(2) show that the dication consists of an asymmetric RhRu(2)S(4) core containing an isosceles triangle of metal atoms with a Ru-Ru bond of 2.88 Å. The three metal atoms are joined by two &mgr;(3)-eta(1):eta(2):eta(1-)S(2) units, each persulfide being monodentate toward Rh. NMR studies show that 1(2+) is stereochemically nonrigid such that the two Ru(C(5)Me(5)) resonances coalesce at higher temperatures. The dynamic processes involving 1(2+) are unaffected by added (C(5)Me(5))Rh(MeCN)(3)(2+), ruling out dissociation of the (C(5)Me(5))Rh center. Exchange of the (C(5)Me(5))Ru sites in [(C(5)Me(5))(2)(C(5)Me(4)Et)RhRu(2)S(4)(MeCN)](PF(6))(2), 2(PF(6))(2), is associated with coalescence of the pairs of C(5)Me(4)Et resonances, suggesting that the dynamics in 1(2+) involve racemization. It is proposed that these dynamics proceed via the "base-free" intermediate [(C(5)Me(5))(3)RhRu(2)S(4)](2+), wherein one S-S bond has been cleaved. Solutions of 1(2+) react with acetone to give the S-acetonyl derivative [(C(5)Me(5))(3)RhRu(2)S(3)(SCH(2)COCH(3))]PF(6), 4(PF(6)). This species, which is not fluxional on the NMR time scale, is a rare example of a metal sulfido cluster with a trigonal prismatic M(3)S(3) core. There is one metal-metal bond of 2.75 Å between the two Ru atoms, spanned by the acetonylthio ligand. The M-S distances are nearly equivalent at 2.33 Å while the S-S bonding distance is 2.12 Å. This reaction is reversed by acid to give 1(2+) and acetone.
Venturelli
Anne
A
School of Chemical Sciences, University of Illinois, Urbana, Illinois 61801.
Rauchfuss
Thomas B.
TB
Verma
Atul K.
AK