title: Ten-vertex polyhedral azametallaborane chemistry: a unique nido-6,9 to nido-6,8-cluster isomerization.
abstract: Reaction of the [arachno-4-NB(8)H(12)](-) anion 2 with [RhCl(2)(eta(5)-C(5)Me(5))](2) in CH(2)Cl(2) at room temperature affords a mixture of red '6,9' isomer [9-(eta(5)-C(5)Me(5))-nido-6,9-NRhB(8)H(11)] (3) and its yellow '6,8' isomer, [8-(eta(5)-C(5)Me(5))-nido-6,8-NRhB(8)H(11)] (4). Under the same conditions, reactions of 2 with [IrCl(2)(eta(5)-C(5)Me(5))](2) and [RuCl(2)(eta(6)-MeC(6)H(4)-4-(iso)Pr)](2) give the '6,8' isomers, yellow [8-(eta(5)-C(5)Me(5))-nido-6,8-NIrB(8)H(11)] (5) and red [8-(eta(6)-MeC(6)H(4)-4-(iso)Pr)-nido-6,8-NRuB(8)H(11)] (6), respectively. In contrast, [IrCl(PPh(3))(3)] yields orange [9,9-(PPh(3))(2)-9-H-nido-6,9-NIrB(8)H(11)] (7), which exhibits the '6,9' configuration. Compound 3 isomerizes quantitatively in solution to give 4. At high temperatures, compound 7 gives the yellow '6,8' species, [8,8-(PPh(3))(2)-8-H-nido-6,8-NIrB(8)H(11)] (8), in low yields. Possible mechanisms for the unprecedented 6,9 --> 6,8 isomerization are discussed.
authors: School of Chemistry, University of Leeds, Leeds, UK LS2 9JT. rmacias@unizar.es
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