Synthesis and Reactivity of Functionalized Dimethylsilyl Complexes of the Formula (η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(SiMe 2 X); New Base‐Stabilized Silylene Complexes, Novel Lewis Acid Adducts, and Evidence for Base‐Free Silylene Complexes

Reactions of (η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(SiMe 2 H) ( 1 ) and CHCl 3 , CBr 4 , and CHI 3 give halosilyl complexes (η 5 ‐C 5 H 5 )Re(NO)‐(PPh 3 )(SiMe 2 X) [X = Cl ( 2 ), Br ( 3 ), I ( 4 ); 66–84%]. Addition of Me 3 SiOTf to 2 gives triflate (η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(SiMe 2 OTf) (5; 97%), which in turn reacts with (Me 2 N) 3 S ⊕ [SiMe 3 F 2 ] ⊖ to give (η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(SiMe 2 F) ( 6 ; 77%). Reaction of 5 and pyridine gives the base‐stabilized silylene complex [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 ){SiMe 2 (NC 5 H 5 )}] ⊕ TfO ⊖ ( 7 ; 84%). CH 2 Cl 2 solutions of (η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )(CH 3 ) ( 8 ) or 2 and Lewis acids are studied by IR and NMR. As assayed by IR, 8 /ECl 3 solutions (E = B, Al) show ReNO–ECl 3 (major) and Re–ECl 3 (minor) adducts. Solutions of 2/BCl 3 show analogous adducts (‐78°C), and in the presence of excess BCl 3 (η 5 ‐C 5 H 5 )Re‐(NO–BCl 3 )(PPh 3 )(SiMe 2 Cl) ( 11 ) crystallizes. Solutions of 2 /AlCl 3 show uncomplexed 2 and Re–AlCl 3 (major) and ReNO–AlCl 3 (minor) adducts. In contrast to 2 – 7 and 2/BCl 3 , 1 H‐ and 13 C‐NMR spectra of 2 /AlCl 3 suggest an equilibrium with the base‐free silylene complex [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 )‐( = SiMe 2 )] ⊕ X ⊖ .