SYNTHESIS AND REACTIVITY OF FUNCTIONALIZED DIMETHYLSILYL COMPLEXES OF THE FORMULA (ETA-5-C5H5)RE(NO)(PPH3)(SIME2X) - NEW BASE-STABILIZED SILYLENE COMPLEXES, NOVEL LEWIS ACID ADDUCTS, AND EVIDENCE FOR BASE-FREE SILYLENE COMPLEXES

Reactions of (eta-5-C5H5)Re(NO)(PPh3)(SiMe2H) (1) and CHCl3, CBr4, and CHI3 give halosilyl complexes (eta-5-C5H5)Re(NO)(PPh3)(SiMe2X) [X = Cl (2), Br (3), I (4); 66-84%]. Addition of Me3SiOTf to 2 gives triflate (eta-5-C5H5)Re(NO)(PPh3)(SiMe2OTf) (5; 97%), which in turn reacts with (Me2N)3S+ [SiMe3F2]- to give (eta-5-C5H5)Re(NO)(PPh3)(SiMe2F) (6; 77%). Reaction of 5 and pyridine gives the base-stabilized silylene complex [(eta-5-C5H5)Re(NO)(PPh3){SiMe2(NC5H5)}]+TfO- (7; 84%). CH2Cl2 solutions of (eta-5-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-degrees-C), and in the presence of excess BCl3 (eta-5-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, H-1- and C-13-NMR spectra of 2/AlCl3 suggest an equilibrium with the base-free silylene complex [(eta-5-C5H5)Re(NO)(PPh3)(= SiMe2)]+X+.