The a c t i o n of I z / I -in methanol o n compounds PhCH2SnRj l e a d s o n l y t o c l e a v a g e o f t h e b e n z y l group (as PhCH2I) when R=Et, P r n o r Bun. WithPhCH2SnMe3, b o t h b e n z y l and methyl groups are removed. R a t e C o n s t a n t s a r e r e p o r t e d f o r t h e i o d o d e m e t a l l a t i o n o f a l l f o u r PhCH2SnR3 compounds, R=Me, E t , P r n and Bun.The ? r e s e n t r e s u l t s and p r e v i o u s l i t e r a t u r e d a t a show t h a t w i t h a c o n s t a n t SnR3 l e a v i n g group, t h e sequence o f a l k y l -t i n r e a c t i v i t y i s Ph>PhCH2>Me>Et>Prn, w i t h t h e b e n z y l -t i n bond b e i n g broken 3-4 t i m e s as r a p i d l y as t h e m e t h y l -t i n bond and a b o u t 4 0 t i m e s as r a p i d l y as t h e e t h y l -t i n bond.The e f f e c t o f added a n i o n s , C 2 , B r -, I-and CEO4-on t h e r a t e c o n s t a n t s (and p r o d u c t s ) a r e r e p o r t e d , and it i s shown t h a t b o t h k i n e t i c s t u d i e s and p r o d u c t a n a l y s e s l e a d to t h e c o n c l u s i o n t h a t f o r e i g n a n i o n s d o n o t p a r t i c i p a t e i n t h e r e a c t i o n mechanism.These a r e , however, s p e c i f i c k i n e t i c s a l t e f f e c t s i n t h e o r d e r NaBr