Reaction of a 14-vertex carborane with nucleophiles: formation of nido-C(2)B(12), nido-C(2)B(11,) and closo-CB(11) carborane anions.

Nucleophilic reactions of a 14-vertex closo-carborane are reported. 2,3-(CH(2))(3)-2,3-C(2)B(12)H(12) (1) reacts with MeOH at 70 degrees C to give closo-CB(11) anions 1,2-(CH(2))(3)CH(OMe)-1-CB(11)H(10) (2a), 1,2-(CH(2))(2)CH(OMe)CH(2)-1-CB(11)H(10) (2b), and 1,2-(CH(2))(2)CH horizontal lineCH-1-CB(11)H(10) (2c). It is suggested that 2c is an intermediate for the isomerization from 2a to 2b. Treatment of 1 with MeOH/Me(3)N, (t)BuOK or LiNMe(2) affords nido-C(2)B(12) species 8,9-(CH(2))(3)-mu-11,12-(Nu)BH-8,9-C(2)B(11)H(11) (Nu = MeO (3a), (t)BuO (3b), and Me(2)N (3c)). In the presence of acid such as HCl, anions 3 are converted to 1. However, 3 undergo deboration reaction, in the presence of bases, to generate a nido-C(2)B(11) anion 8,9-(CH(2))(3)-8,9-C(2)B(11)H(12) (4) that can also be formed directly from the reaction of 1 with excess CsF or piperidine. Mechanistic studies show that 3a is the first intermediate in the reaction of 1 with MeOH and 4 is unlikely an intermediate.