A coordinatively flexible ligand for carbonyl clusters: bridging and terminal SnCl3 groups in the iridium clusters [Ir4(CO)11((mu)SnCl3)]–, [Ir4(CO)10(SnCl3)((mu)-SnCl3)]2– and [Ir6(CO)15((mu)3-SnCl3)]–

The carbonyl cluster [Ir4(CO)11(SnX3)]–[X = Cl, (1a) or Br (1b)] can be formed in good yield by insertion of SnX2 in the Ir–Br bond of [Ir4(CO) 11Br]– or, much less efficiently, by substitution of bromine with [SnCl3]–, in THF at room temperature. The disubstituted cluster [Ir4(CO)10(SnCl3) 2]2–(2) was obtained in 50% yields by double substitution on [Ir4(CO)11Br]–, in THF at 60 °C, whereas [Ir6(CO)15(SnCl3)]–(3) can be prepared by carbonyl substitution of the homoleptic complex [Ir6(CO)16] with an excess of [SnCl3]– in refluxing THF. In the three compounds, the SnCl3 units act as a one electron donor, displaying terminal (in 2), edge-bridging (in 1 and 2) and face-bridging (in 3) coordination. In keeping with a reduced bond order, the Ir–Sn bond distances increase in the series, being 2.584(1)A for a terminal group; 2.72 A for edge-bringing units and 2.78 A for the face-bridging SnCl3. Regardless of the coordination mode, the geometry of the three chlorine atoms is always pyramidal, with Cl–Sn–Cl angles close to 90° and Sn–Cl bond distances close to 2.42 A . Tin is always symmetrically bridging, with Ir–Sn–Ir close to 60°.