Photochemical studies of (η~5-C_5H_5)Ru(PPh_3)~2Cl and (η~5-C_5H_5)Ru(PPh_3)_2Me: formation of Si-H and C-H bond activation products

摘要

Studies examining the photochemical reactivity of CpRu(PPh_3)_2Cl and CpRu(PPh_3)_2Me towards the two electron donor ligands PEt_3, C_2H_4, DMSO, the CH bond activatable reagents tetrahydrofuran, toluene, and pyridine, and the SiH bond activatable reagents HSiEt_3 and HSi(Me)_2CHvCH_2) are presented. Broadband UV irradiation of CpRu(PPh_3)_2Cl leads to the formation of mono-substitution products such as CpRu(PPh_3)- (PEt_3)Cl which are inert to further photochemical reaction, although thermally bis-substituted products such as CpRu(PEt_3)_2Cl can be formed. Room temperature irradiation of the related complex CpRu- (PPh_3)_2Me with L = PEt_3, C_2H_4, and DMSO also produces CpRu(PPh_3)(L)Me. However, when these reactions are followed by in situ laser irradiation (325 nm source) at low temperature, three solvent activated isomers (ortho, meta and para) of CpRu(PPh_3)_2(C_6H_4Me) are detected in toluene in addition to η~1- and η~3-coordinated benzyl species. Furthermore, photolysis in THF leads to both the C-D bond activation product CpRu(PPh_3)_2(OC_4D_7) and the labile coordination complex CpRu(PPh_3)(THF)Me. Now CH_4 rather than CH3D is liberated which suggests the involvement of an orthometallated species. The photochemically driven reaction of CpRu(PPh_3)_2Me with HSiEt_3 at 198 K generates CpRu(κ~2-2-C_6H_4PPh_2)(SiEt_3)H and thereby confirms a role for an orthometallated complex is this process. Irradiation in cyclohexane produces the known orthometallated complex, CpRu(κ~2-2-C_6H_4PPh_2)(PPh_3), and CH_4 in accordance with this reactivity.