Ligand substitution and growth reactions with Ru3Se2 nido clusters.: Coordination isomerism in [WRu3(μ4-Se)2(μ-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. (C) 2004 Elsevier B.V. All rights reserved.