Reactions of a Highly Crowded Cyclic Stannylene with Iodoalkanes, Enones, and Dienes. Inhibition of Nucleophilic Substitution at Tin(IV) Centers

The cyclic stannylene ( 2; RR = C(SiMe 3 ) 2 SiMe 2 CH 2 CH 2 Me 2 Si(Me 3 Si) 2 C) reacted with alkyl iodides R‘I (R‘ = Et, i Pr) to give the Sn IV compounds ( 6b, c ), which were converted by treatment with silver trifluoroacetate into ( 7b, c ). Reactions of the stannylene 2 with appropriate enones or diones yielded the products ( 10 ), ( 11 ), ( 12 ), and ( 13 ) (OC 14 H 8 O = 9,10-phenanthrenediolato). The crystal structures of 6b, 7b, c, and 10 − 13 have been determined. Treatment of 2 with water, alcohols, or phenol led to ring opening. There is evidence from ESR spectroscopy that the oxidative additions of diones involve radical intermediates. The compound ( 6a ) reacted with ICl to give the chloride ( 15 ), but, in contrast to the previously described crowded trialkyltin halides (Me 3 Si) 3 CSnMe 2 X (X = Cl, I), neither 6a nor 15 reacted with nucleophilic reagents.