EFFECT OF ANCILLARY LIGANDS ON RU(II) ON ELECTRONIC DELOCALIZATION INRUTHENIUM(II) BISFERROCENYLACETYLIDE COMPLEXES

The synthesis and properties of [cis-Ru(dppm)(2)(C=CFc)(2)]CuI (dppm=P h2PCH2PPh2, Fe=ferrocenyl) (1) and trans, trans, trans-Ru(PBu3)(2)(CO) (L)(C=CFc)(2) (3, L=CO; 4, L pyridine; 5, L=P(OMe)(3)) are reported. T he ruthenium bisacetylide bridges in these complexes allow electronic interaction between the terminal ferrocenyl groups. The interaction is enhanced when the ancillary ligands on the ruthenium center are elect ron donors and lessened when the ligands are-acceptors. Complex 1 was prepared in 70% yield by the coupling of FcC=CSn(n-Bu)(3) and cis- or trans-RuCl2(dppm)(2) in the presence of excess CuI and was crystallogr aphically characterized. Removal of the coordinated CuI from 1 with ex cess P(OMe)(3) yields trans-Ru(dppm)(2)(C=CFc)(2) (2). Reaction of 2 w ith CuI yields 1. trans, trans, trans-Ru(PBu3)(2)(CO)(2)(C=CFc)(2) (3) was synthesized from RuCl2(CO)(2)(PBu3)(2) and FcC=CSn(n-Bu)(3) using a CuI catalyst and was crystallographically characterized. Reaction o f 3 with excess pyridine yields trans, trans, trans-Ru(PBu3)(2)(CO)(py )(C=CFc)(2) (4). The reaction is reversible; 3 may be obtained by reac ting 4 with excess carbon monoxide, Reaction of 4 with P(OMe)(3) yield s s,trans,trans-Ru(PBu3)(2)(CO)(P(OMe)(3))(C=CFc)(2) (5). Dications of all the complexes were prepared by oxidation with 2 equiv of FcPF(6), and monocations were prepared in solution by reaction of the neutral complexes with the dications. The difference between the first and sec ond ferrocenyl oxidations (Delta E-1/2) in the cyclic voltammograms of 1, 3, 4, and 5 are 0.14, 0.09, 0.13, and 0.15 V, respectively. Charac terization of the complexes by visible, IR, and near-IR spectroscopy s upports the conclusion that the ligand environment of the ruthenium ce nter affects the extent of electronic delocalization between the ferro cenyl groups.