Amino‐Substituted Ferra‐bis(tricarbollides) − Metallatricarbaboranes Designed for Linear Molecular Constructions

Abstract

AbstractReactions between high purity FeCl2 and the anion [nido‐7‐(tBuHN)‐7,8,9‐C3B8H10)]− (1−) have been used for efficient syntheses of the twelve‐vertex double‐cluster metallatricarbollide complexes of the para,para (p,p) type [closo‐9,9′(RHN)2‐commo‐2,2′‐FeII‐1,7,9‐(C3B8H10)‐1′,7′,9′‐(C3B8H10)] (2) (2a, R = tBu and 2b, R = H) (yields 42−45% for 2a). Compound 2b, which contains two reactive amino substituents conveniently attached to the tricarbollide subclusters in p‐positions with respect to the metal center, was prepared via facile cleavage of the tBu substituent in 2a either by AlCl3 or by thermal means. The structure of 2b constitutes a good setting for the synthesis of building blocks for constructing linear metallatricarbollide rods of high stability. Two isomeric compounds of the para,meta (p,m) type 3, [closo‐9,10′‐(RHN)2‐commo‐2,2′‐Fe‐1,7,9‐(C3B8H10)‐1′,7′,10′‐(C3B8H10)] (where R = tBu 3a and/or H 3b), were isolated in smaller yields from reactions of high purity FeCl2 with 1− at higher temperatures. Also reported is the characterization of the m,m‐type complex, [closo‐10,10′‐(tBuHN)2‐commo‐2,2′‐FeII‐1,7,10‐(C3B8H10)‐1′,7′,10′‐(C3B8H10)] (4a), and the two zwitterionic species of the new 7‐L‐7,8,10‐C3B8H10 type (6) [L = Me3N 6a and tBu(Me)HN 6b] isolated in moderate yields from the reaction of reagent grade FeCl2 with 1−. The molecular structures of 2b, 3a, and 6b were determined by single‐crystal X‐ray diffraction studies. Multinuclear (1H and 11B), two‐dimensional [11B‐11B]‐COSY, and 1H{11B(selective)} magnetic resonance measurements enabled complete assignments of all resonances for all compounds and are in excellent agreement with the structures proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)