13-Vertex carborane, mu-1,2-(CH2)(3)-1,2-C2B11H11, (1), reacted with a series of nucleophiles (Nu) to give the cage carbon extrusion products [mu-1,2-(CH2)(3)CH(Nu)-1-CB11H10](-), [mu-1,2-(CH2)(2)CH(Nu)CH2-1-CB11H10](-), and/or [mu-1,2-(CH2)(2)CH=CH-1-CB11H10](-), depending on the nature of Nu and the reaction conditions. The key intermediates for the formation of CB11- anions were isolated and structurally characterized as [mu-eta:eta:eta-7,8,10-(CH2)(3)CHB(Nu)-7-CB10H10](-) (Nu = OMe, NEt2). The reaction mechanism is thus proposed, which involves the attack of Nu at the most electron-deficient cage boron, followed by H-migration to one of the cage carbons, leading to the formation of the intermediate. Nu-migration gives the products.