Eleven-vertex polyhedral metalladicarbaborane chemistry.: Reactions of neutral nido-5,6-C2B8H12 and the [nido-6,9-C2B8H10]2- anion to give formally close 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-(η6-C6Me6)-1,2,4-RuC2B8H9] and [2-Me-1-(η5-C5Me5)-1,2,3-RhC2B8H9]

Reactions between nido-5,6-C2B8H12 (1) and the organometallic halides [{MLCl2}2] (2) [where {ML}= {Ru(eta (6)-C6Me6)} (2a), {Ru(eta (6)-p-MeC6H4'Pr)} (2b), {Rh(eta (5)-C5Me5)} (2c), and {Os(eta (6)-p-MeC6H4'Pr)} (2d)] in the presence of N,N,N',N'-tetramethyl-naphthalene-1,8-diamine (tmnda) in dichloromethane or chloroform have generated a series of the corresponding metalladicarbaboranes [1-L-1,2,4-MC2B8H10] (3, close 11-vertex numbering system) [where {ML} = {Ru(eta (6)-C6Me6}) (3a), {Ru(eta (6)-p-(MeC6H4Pr)-Pr-i)} (3b), {Rh(eta (5)-C5Me5)} (3c), and {Os(eta (6)-p-(MeC6H4Pr)-Pr-i)} (3d)] in yields of 48-94%. The substituted species, [5-Br-1-(eta (6)-C6Me6)-1,2,4-RuC2B8H9] (5-Br-3a) and [7-Br-1-(eta (6)-C6Me6)-1,2,4-RuC2B8H9] (7-Br3a) have been obtained from a similar reaction involving [7-Br-nido-5,6-C2B8H11] (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 [{MLCl2}(2)] (2) and the [nido-6,9-C2B8H10](2-) anion (species 4(2-)) have produced a series of the isomeric symmetrical complexes [1-L-closo-1,2,3-MC2B8H10] (5) [where {ML} = {Ru(eta (6)-C6Me6)} (5a), {Ru(eta (6)-p-MeC6H4'Pr)} (5b), (Rh(eta (5)-C5Me5)} (5c) and {Os(eta (6)-p-(MeC6H4Pr)-Pr-i)} (5d)]; the 2-methyl substituted compound [2-Me-1-(eta (5)-C5Me3-closo-1,2,3-RhC2B8H9 (2-Me-5c) has been prepared similarly using the [6-Me-nido-C2B8H9](2-) anion (species 2-Me-4(2-)) as the starting dicarbaborane. All these compounds are characterised by mass spectrometry and B-11- and H-1-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 {MC2B8} clusters of compounds 3 have four-membered open faces, generating an 'isonido' geometry, whereas those of compounds 5 approximate more to the classical close cluster geometry. Thermolyses of the {1,2,4-MC2B8} compounds 3a-3d cleanly generate their corresponding {1,2,3-MC2B8} isomers 5a-5d. (C) 2000 Elsevier Science B.V. All rights reserved.