A coordinatively flexible ligand for carbonyl clusters: bridging and terminal SnCl3 groups in the iridium clusters [Ir-4(CO)(11)(mu-SnCl3])(-), [Ir-4(CO)(10)(SnCl3)(mu-SnCl3)](2-) and [Ir-6(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) Å for a terminal group; 2.72 Å for edge-bringing units and 2.78 Å 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 Å. Tin is always symmetrically bridging, with Ir–Sn–Ir close to 60 .