Eleven-vertex polyhedral metalladicarbaborane chemistry. Reactions of neutral nido-5,6-C 2B 8H 12 and the [ nido-6,9-C 2B 8H 10] 2− anion to give formally closo isomeric 1-(arene) and 1-(cyclopentadiene)-1,2,4- and 1,2,3-metalladicarbaundecaboranes, and some substituent chemistry. Chiral separations, and crystal and molecular structures of [5-Br-1-(η 6-C 6Me 6)-1,2,4-RuC 2B 8H 9] and [2-Me-1-(η 5-C 5Me 5)-1,2,3-RhC 2B 8H 9

Abstract

Reactions between nido-5,6-C 2B 8H 12 ( 1) and the organometallic halides [{MLCl 2} 2] ( 2) [where {ML}={Ru(η 6-C 6Me 6)} ( 2a), {Ru(η 6- p-MeC 6H 4 i Pr)} ( 2b), {Rh(η 5-C 5Me 5)} ( 2c), and {Os(η 6- p-MeC 6H 4 i Pr)} ( 2d)] in the presence of N, N, N′, N′-tetramethylnaphthalene-1,8-diamine (tmnda) in dichloromethane or chloroform have generated a series of the corresponding metalladicarbaboranes [1-L-1,2,4-MC 2B 8H 10] ( 3, closo 11-vertex numbering system) [where {ML}={Ru(η 6-C 6Me 6)} ( 3a), {Ru(η 6- p-MeC 6H 4 i Pr)} ( 3b), {Rh(η 5-C 5Me 5)} ( 3c), and {Os(η 6- p-MeC 6H 4 i Pr)} ( 3d)] in yields of 48–94%. The substituted species, [5-Br-1-(η 6-C 6Me 6)-1,2,4-RuC 2B 8H 9] ( 5-Br-3a) and [ 7-Br-1-(η 6-C 6Me 6)-1,2,4-RuC 2B 8H 9] ( 7-Br-3a) have been obtained from a similar reaction involving [7-Br- nido-5,6-C 2B 8H 11] ( 7-Br-1) (combined yield 75%, separated by preparative HPLC). Each of the compounds 5-Br-3a and 7-Br-3a has been resolved into its enantiomers by use of chiral HPLC separation techniques. Analogous reactions between [{MLCl 2} 2] ( 2) and the [ nido-6,9-C 2B 8H 10] 2− anion (species 4 2−) have produced a series of the isomeric symmetrical complexes [1-L- closo-1,2,3-MC 2B 8H 10] ( 5) [where {ML}={Ru(η 6-C 6Me 6)} ( 5a), {Ru(η 6- p-MeC 6H 4 i Pr)} ( 5b), {Rh(η 5-C 5Me 5)} ( 5c) and {Os(η 6- p-MeC 6H 4 i Pr)} ( 5d)]; the 2-methyl substituted compound [2-Me-1-(η 5-C 5Me 5)- closo-1,2,3-RhC 2B 8H 9] ( 2-Me-5c) has been prepared similarly using the [6-Me- nido-C 2B 8H 9] 2− anion (species 2-Me-4 2−) as the starting dicarbaborane. All these compounds are characterised by mass spectrometry and 11B- and 1H-NMR spectroscopy. Single-crystal X-ray diffraction studies have been carried out on compounds 5-Br-3a and 2-Me-5c as two representative examples of the compounds in series 3 and in series 5. The {MC 2B 8} clusters of compounds 3 have four-membered open faces, generating an ‘ isonido’ geometry, whereas those of compounds 5 approximate more to the classical closo cluster geometry. Thermolyses of the {1,2,4-MC 2B 8} compounds 3a– 3d cleanly generate their corresponding {1,2,3-MC 2B 8} isomers 5a– 5d.