Ligand substitution and growth reactions with Ru3Se2 nido clusters. Coordination isomerism in [WRu3(mu(4)-Se)(2)(mu-CO)(4)(CO)(7)(L)] (L = phosphine ligand) and electrochemical behaviour of the Ru3MSe2 core clusters (M = Ru, W) in solution

The monosubstituted selenido-carbonyl open-triangular nido cluster [Ru-3(mu(3)-Se)(2)(CO)(8)(L)] (L = trispyrrolidinylphosphine, tpnp) reacts with trisparamethoxyphenylphosphine (t4mpp) and alpha,alpha'-bis(diphenylphosphinemethyl)benzene (dpmb), giving, respectively, the di- and tri-substituted [Ru-3(mu(3)-Se)(2)(CO)(6)(tpnp)(dpmb)] and [Ru-3(mu(3)-Se)(2)(CO)(7)(tpnp)(t4mpp)] clusters. Moreover, clusters [Ru-3(mu(3)-Se)(2)(CO)(8)(L)] (L = tpnp, t4mpp, diphenylmethoxyphosphine (dpxp)) show a reactivity towards [W(CO)(3)(MeCN)(3)], leading to the corresponding bimetallic closo clusters [WRu3(mu(4)-Se)(2)(mu-CO)(4)(CO)(7)(L)]. The formation of two coordination isomers, due to the position of L on different Ru atoms, confirms the presence in solution of two [Ru-3(mu(3)-Se)(2)(CO)(8)(L)] isomers before the attack of the W(CO)(3) fragment. Finally, electrochemical measurements show that the substitution of a Ru atom with a W atom in the closo Ru4Se2 cluster core triggers significant changes in the redox activity of the cluster core, which is further modulated by the electronic effects of the peripheral phosphines.