Alkylidyne-alkyne coupling on triruthenium clusters. Isomerization of (μ-H)Ru3(μ3-η3-EtSCCRCR)(CO) 9 (R = Me or Ph) to Ru3(μ-SEt)(CO)9(μ3-η 3-CCRCHR), an intermediate in alkylidyne chain growth. The crystal structure of Ru3(μ-SEt)(μ ...