ChemInform Abstract: Synthesis and Reactivity of Functionalized Dimethylsilyl Complexes of the Formula (η5-C5H5)Re(NO)(PPh3)(SiMe2X); New Base-Stabilized Silylene Complexes, Novel Lewis Acid Adducts, and Evidence for Base- Free Silylene Complexes.

Abstract

Reactions of (η5-C5H5)Re(NO)(PPh3)(SiMe2H) (1) and CHCl3, CBr4, and CHI3 give halosilyl complexes (η5-C5H5)Re(NO)-(PPh3)(SiMe2X) [X = Cl (2), Br (3), I (4); 66–84%]. Addition of Me3SiOTf to 2 gives triflate (η5-C5H5)Re(NO)(PPh3)(SiMe2OTf) (5; 97%), which in turn reacts with (Me2N)3S⊕ [SiMe3F2]⊖ to give (η5-C5H5)Re(NO)(PPh3)(SiMe2F) (6; 77%). Reaction of 5 and pyridine gives the base-stabilized silylene complex [(η5-C5H5)Re(NO)(PPh3){SiMe2(NC5H5)}]⊕ TfO⊖ (7; 84%). CH2Cl2 solutions of (η5-C5H5)Re(NO)(PPh3)(CH3) (8) or 2 and Lewis acids are studied by IR and NMR. As assayed by IR, 8/ECl3 solutions (E = B, Al) show ReNO–ECl3 (major) and Re–ECl3 (minor) adducts. Solutions of 2/BCl3 show analogous adducts (-78°C), and in the presence of excess BCl3 (η5-C5H5)Re-(NO–BCl3)(PPh3)(SiMe2Cl) (11) crystallizes. Solutions of 2/AlCl3 show uncomplexed 2 and Re–AlCl3 (major) and ReNO–AlCl3 (minor) adducts. In contrast to 2–7 and 2/BCl3, 1H- and 13C-NMR spectra of 2/AlCl3 suggest an equilibrium with the base-free silylene complex [(η5-C5H5)Re(NO)(PPh3)-( = SiMe2)]⊕ X⊖.