Chemistry of a Metallathiaborane Cluster. 5.^† Reaction of [8,8-(η²-dppm)-8-(η¹-dppm)-<i>n</i><i>ido</i>-8,7-RhSB₉H₁₀] and Its Derivatives with Organotransition-Metal Reagents

The phosphine ligands on [8,8-(PPh3)2-nido-8,7-RhSB9H10] (2) may be replaced by the bidentate phosphine dppm {dppm = [(CH2)(PPh2)2]} to form the species [8,8-(η2-dppm)-8-(η1-dppm)-nido-8,7-RhSB9H10] (3). The latter reacts with [Ru(η6-p-cym)(μ-Cl)2]2 to afford [8,8-η2-{(μ-Cl)2Ru(η6-p-cym)(dppm)}-nido-8,7-RhSB9H10] (4), which contains the group [(μ-Cl)2Ru(η6-p-cym)(dppm)] that coordinates in a multidentate mode to Rh, in 77% yield. Similar chemistry using [Cp*Ir(μ-Cl)2]2 {Cp* = [η5-C5(CH3)5]} affords the related species [8,8-η2-{(μ-Cl)2Cp*Ir(dppm)}-nido-8,7-RhSB9H10] (5), and [8,8-η2-{(μ-Cl)2Cp*Rh(dppm)}-nido-8,7-RhSB9H10] (6) is obtained from the reaction between 2 and [Cp*RhCl2(η1-dppm)]. Reactions of 3 with [IrCl(CO)(PPh3)2] or [RhCl(PPh3)3] result in removal of dppm. [RhCl(PPh3)3] reacts with 3 to afford [1-PPh3-{1,3-(μ-dppm)}-closo-1,2-RhSB9H8] (7), but on reaction for extended periods [8-Cl-{8,9-(μ-dppm)}-10-PPh3-nido-8,7-RhSB9H7] (8) is also formed. Reaction between 7 and dppe {dppe = [(CH2)2(PPh2)2]} gives [1,1-(η2-dppe)-3-(η1-dppm)-closo-1,2-RhSB9H8] (9), which when treated with [Ru(η6-p-cym)(μ-Cl)2]2, affords [1,1-(η2-dppe)-3-η1-{(dppm)Ru(η6-p-cym)Cl2)}-closo-1,2-RhSB9H8] (10), in which the rhodathiaborane cage has a pendent metal-ligated dppm group at the 3-position. A rationale for the formation of 7 and 8 in the reaction of 3 with [RhCl(PPh3)3] is presented, and it provides evidence for the pathways for reactions of the other metal-containing moieties with 3. The existence of 8 provides support for some earlier proposals concerning the chemistry of 3. The new species 4, 5, 6, 8, and 10 are characterized by NMR spectroscopy, elemental analysis, mass spectrometry, and in the case of 4, 8, and 10, crystal structure determinations.