Evidence for cyclic bromonium lons IL. Crystal Structure of Adamanty lideneadamantane Bromonium lon -2 Br-1 X-ray structure C-Br bond lengths are slightly longer than in normal alkyl 2.116A 2.194A bromides: 2.116 A and 2.194 A Vs 1.93-204A C-C bond is 1.497 A which is shorter than sp hybridized C-C bond(1.54 A)but longer than C=C(1.336 A in starting 1497A material) r3 counterion is linear but lengths are not symmetrical. Br- is interacting with Br-3 which causes an asymmetry in the molecule(accounts for different C-Br-1 bond lengths) Br-1 and Br-3 are within van der Waals distance (3.097 A vs Slebocka-Tilk.H. Ball R.G. brown.RS JACS 1985. 107 4504 3.7 A for van der Waals) PA-Bromonium 06 10/4/00 3: 01 PM2 eq Br2 -2 eq Br2 II. Crystal Structure of Adamantylideneadamantane Bromonium Ion Evidence for Cyclic Bromonium Ions C-Br bond lengths are slightly longer than in normal alkyl bromides: 2.116 Å and 2.194 Å vs. 1.93-2.04 Å . C-C bond is 1.497 Å which is shorter than sp3 hybridized C-C bond (1.54 Å) but longer than C=C (1.336 Å in starting material). Br3- counterion is linear but lengths are not symmetrical. Br-1 is interacting with Br-3 which causes an asymmetry in the molecule (accounts for different C-Br-1 bond lengths). Br-1 and Br-3 are within van der Waals distance (3.097 Å vs. 3.7 Å for van der Waals). Slebocka-Tilk, H.; Ball, R. G.; Brown, R. S. JACS 1985, 107. 4504 C C Br Br3– Br-1 Br-4 Br-2 Br-3 X-ray structure 2.116 Å 2.194 Å 1.497 Å 09A-Bromonium 06 10/4/00 3:01 PM