Surface organometallic chemistry - Carbonyl complexes of Re(I) with silanolates as models of silica anchored rhenium carbonyl species

Reaction of Me3SiONa with [Re(CO)(5)Cl] affords the new complex Na[Re-2(CO)(6)(mu-OSiMe3)(3)], which could be generated via formation of [Re(CO)(5)OSiMe3] followed by immediate reaction with Me3SiO-. Substitution of some CO ligands by phosphines significantly decreases the electrophilicity of the Re(I) center, and therefore hinders further attack by Me3SiO-. Thus, fac-[Re(CO)(3)(Ph2PCH2CH2PPh2)OTf] (OTf is the triflate anion) reacts with Me3SiONa to give fac-[Re(CO)(3)(Ph2PCH2CH2PPh2)OSiMe3], a molecular model of silica anchored [Re(CO)(5)OSi]. However, substitution of only one CO by triphenylphosphine is not enough to avoid the formation of [Re-2(CO)(6)(mu-OSiMe3)(3)](-). While fac-[Re(CO)(3)(Ph2PCH2CH2PPh2)OSiMe3] is stable towards hydrolysis, [Re-2(CO)(6)(mu-OSiMe3)(3)](-) is readily hydrolyzed to [Re-2(CO)(6)(mu-OH)(mu-OSiMe3)(2)](-), a molecular model of silica anchored [Re-2(CO)(6)(mu-OH)(mu-OSi)(2)](-), whose structure has been determined by single crystal X-ray diffraction.