J . Am. Chem. SOC.1988, 110, 7543-7544 ( H 2 0 ) 6 ( t o ~ )in2 D 2 0 , ( n - 1) equiv of 11 are polymerized, and conversion of the catalvst to the mono-olefin adduct Ru(H20)5(II)(tos)2,111, (A,, = 294 nm) is observed by N M R (eq 2).17
7543
complexes to enhance and understand their organometallic chemistry as well as the utilization of these new catalysts in the polymerization of highly functionalized monomers. Acknowledgment. This work was supported by the National Institute of Health (Grant No. G M 3 1332) and the Rohm and Haas Company. B.M.N. acknowledges IBM for a predoctoral fellowship. We thank Paul Bernhard for samples of Ru( H 2 0 ) 6 ( t o ~ )and 2 many helpful discussions.
A New Structural Form of Tin as a Double Cube. A Heptanuclear Tin-Sulfur Cluster (n-l)eguiv
Aqueous solutions of I11 are highly active in subsequent polymerizations, displaying the same rapid initiation times (1 0-1 2 s) as the limiting initiation times observed for the recycled Ru3+ solutions. We therefore attribute the increased activity of the recycled catalyst solutions to the in situ formation of Ru2+olefin complexes.Is When the polymerization of I1 is carried out by using Ru3+salts (RuC1, or K2RuC15)in D 2 0 to generate the active catalyst solution, resonances identical with the olefin resonances of adduct 111 are observed." Because Ru3+does not form stable olefin complexes,19we therefore conclude that these resonances are due to RuZ+olefin adducts formed from the reduction of Ru3+ in the reaction mixture. On the basis of formation of Ru4+ (as Ru Red, A,, = 544 nm)*O and a Ru2+ olefin complex21when I1 is polymerized by R u ( N H ~ ) ~ ( H , O )(A~, + = 325 nm), we propose a mechanism which involves the disproportionation of an equilibrium amount of Ru3+-olefincomplex to provide a Ru2+-olefin complex and a Ru4+species which is trapped by additional Ru3+. The olefin complex thus produced initiates the observed polymerization chemistry. The synthetic utility of these aqueous polymerization systems can be expanded to include monomers that are reluctant to polymerize in aqueous solution by using the preformed olefin complex I11 to catalyze the polymerization. For example, the K2RuC15 catalyzed aqueous polymerization of 2-norbornene-5-methanol provides at best only low yields of the desired polymer (typically
