Difunctionalized {closo‐1‐CB11} Clusters: 1‐ and 2‐Amino‐12‐ethynylcarba‐closo‐dodecaborates

Abstract

Carba-closo-dodecaborate anions with two functional groups have been synthesized via a simple two-step procedure starting from monoamino-functionalized {closo-1-CB11 } clusters. Iodination at the antipodal boron atom provided access to [1-H2 N-12-I-closo-1-CB11 H10 ](-) (1 a) and [2-H2 N-12-I-closo-1-CB11 H10 ](-) (2 a), which have been transformed into the anions [1-H2 N-12-RCC-closo-1-CB11 H10 ](-) (R=H (1 b), Ph (1 c), Et3 Si (1 d)) and [2-H2 N-12-RCC-closo-1-CB11 H10 ](-) (R=H (2 b), Ph (2 c), Et3 Si (2 d)) by microwave-assisted Kumada-type cross-coupling reactions. The syntheses of the inner salts 1-Me3 N-12-RCC-closo-1-CB11 H10 (R=H (1 e), Et3 Si (1 f)) and 2-Me3 N-12-RCC-closo-1-CB11 H10 (R=H (2 e), Et3 Si (2 f)) are the first examples for a further derivatization of the new anions. All {closo-1-CB11 } clusters have been characterized by multinuclear NMR and vibrational spectroscopy as well as by mass spectrometry. The crystal structures of Cs1 a, [Et4 N]2 a, K1 b, [Et4 N]1 c, [Et4 N]2 c, 1 e, and [Et4 N][1-H2 N-2-F-12-I-closo-1-CB11 H9 ]⋅0.5 H2 O ([Et4 N]4 a⋅0.5 H2 O) have been determined. Experimental spectroscopic data and especially spectroscopic data and bond properties derived from DFT calculations provide some information on the importance of inductive and resonance-type effects for the transfer of electronic effects through the {closo-1-CB11 } cage.