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

Reaction of Me 3 SiONa with [Re(CO) 5 Cl] affords the new complex Na[Re 2 (CO) 6 (µ-OSiMe 3 ) 3 ], which could be generated via formation of [Re(CO) 5 OSiMe 3 ] followed by immediate reaction with Me 3 SiO – . Substitution of some CO ligands by phosphines significantly decreases the electrophilicity of the Re(I) center, and therefore hinders further attack by Me 3 SiO – . Thus, fac-[Re(CO) 3 (Ph 2 PCH 2 CH 2 PPh 2 )OTf] (OTf is the triflate anion) reacts with Me 3 SiONa to give fac-[Re(CO) 3 (Ph 2 PCH 2 CH 2 PPh 2 )OSiMe 3 ], 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 (µ-OSiMe 3 ) 3 ] – . While fac-[Re(CO) 3 (Ph 2 PCH 2 CH 2 PPh 2 )OSiMe 3 ] is stable towards hydrolysis, [Re 2 (CO) 6 (µ-OSiMe 3 ) 3 ] – is readily hydrolyzed to [Re 2 (CO) 6 (µ-OH)(µ-OSiMe 3 ) 2 ] – , a molecular model of silica anchored [Re 2 (CO) 6 (µ-OH)(µ-OSi≡) 2 ] – , whose structure has been determined by single crystal X-ray diffraction. Key words: surface organometallic chemistry, rhenium, silica, silanolate, molecular model.