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 °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=CH-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 -μ-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.