Hydroisomerization of saturated hydrocarbons with novel MCM-41 immobilized Re(V) complex catalysts

The hetero-functionalized phosphines HPN2. H2PNO and HPN-Pip containing tricarbonyl Re(V) complexes, i.e. [Re(CO)(3)(kappa(3)-PN2)] (I), [Re(CO)(3)Br(kappa(2)-H2PNO)] (II) and [Re(CO)(3)Br(kappa(2)-HPN-Pip)] (III) were covalently bonded to modified and MCM-41 to obtain novel supported hybrid catalysts. Remarkable high catalytic effects were observed with these catalysts in the hydroisomerization of n-alkanes at low temperature. The catalyst II/MCM-41 provided the highest TONs 3.32 x 10(3) with 37% yield for n-hexane and 3.18 x 10(3) with 30% yield for n-heptane. Under optimized condition, good selectivities for n-hexane (85%) and for n-heptane (91%) were obtained. The TGA was used to evaluate the stability of catalysts and reusable for several cycles. A possible carbenium-based mechanism been used to explain product formation. (C) 2012 Elsevier B.V. All rights reserved.