Ferra- and Ruthenatricarbollides CpFeC<INF>3</INF>B<INF>8</INF>H<INF>11</INF> and Cp*RuC<INF>3</INF>B<INF>8</INF>H<INF>11</INF>

The room-temperature photochemical reaction of the tricarbollide anion [nido-7,8,9-C<INF>3</INF>B<INF>8</INF>H<INF>11</INF>]^- (<BO>1a</BO>) with [CpFe(C<INF>6</INF>H<INF>6</INF>)]⁺ proceeds without cluster rearrangement to form the 12-vertex closo-ferratricarbollide 1-Cp-1,2,3,4-FeC<INF>3</INF>B<INF>8</INF>H<INF>11</INF> (<BO>2a</BO>, the metal atom is assigned number 1). <BO>2a</BO> rearranges to the isomeric complex 1-Cp-1,2,3,5-FeC<INF>3</INF>B<INF>8</INF>H<INF>11</INF> (<BO>2b</BO>) at 110 °C and further to 1-Cp-1,2,4,10-FeC<INF>3</INF>B<INF>8</INF>H<INF>11</INF> (<BO>2c</BO>) at 165 °C. The reaction of <BO>1a</BO> with [Cp*RuCl]<INF>4</INF> is accompanied by polyhedral rearrangement giving 1-Cp*-1,2,3,5-RuC<INF>3</INF>B<INF>8</INF>H<INF>11</INF> (<BO>3b</BO>). Its further isomerization occurs slowly at room temperature and rapidly at 65 °C to give complex 1-Cp*-1,2,4,10-RuC<INF>3</INF>B<INF>8</INF>H<INF>11</INF> (<BO>3c</BO>). Similar reactions of [nido-7,8,10-C<INF>3</INF>B<INF>8</INF>H<INF>11</INF>]^- (<BO>1b</BO>) with [CpFe(C<INF>6</INF>H<INF>6</INF>)]⁺ and [Cp*RuCl]<INF>4</INF> afford <BO>2b</BO> and <BO>3b</BO>, respectively. A diamond-square-diamond mechanism for the <BO>2a</BO> → <BO>2b</BO> → <BO>2c</BO> rearrangement sequence is proposed. The relative stability of isomers <BO>2a</BO>−<BO>c</BO> was estimated by DFT calculations. The constitution of the compounds prepared was determined by multinuclear NMR spectroscopy and mass spectrometry. The structures of <BO>2a</BO>, <BO>2b</BO>, and <BO>3c</BO> were established by X-ray diffraction.