Metallaborane reaction chemistry. Part 1. Two interesting closed cluster compounds from the reaction of acetylene with an open nido-6-iridadecaborane

Abstract

The passing of acetylene through a refluxing solution in benzene of [6,6,6-(PPh₃)H(Ph₂P-ortho-[Graphic omitted]] results in the formation of the closo ten-vertex [2,2,2-(PH₃)₂(Ph₂P-ortho-[Graphic omitted]]4(up to 95% based on phosphine content; 47% based on iridium content) and [1,1,1-(CHCH–CHCH)(Ph₂P-ortho-[Graphic omitted]]5(5%). Both compounds have been characterised by multielement NMR spectroscopy and by single-crystal X-ray diffraction studies. Compound 4[monoclinic; a= 1334.1(2), b= 1798.9(3), c= 1646.2(2) pm, β= 97.86(1)°, and Z= 4; space group P2₁/c; R= 0.0337 for 5703 reflections] has a conventional ten-vertex {closo-2-IrB₉} cluster structure and has two PH₃ ligands on the metal atom which arise from the reductive stripping of the P-aryl groups from arylphosphine ligands. Compound 5[monoclinic; a= 1778.9(5), b= 1368.7(3), c= 1789.9(5) pm, β= 116.69(2)°, and Z= 4; space group P2₁/c; R= 0.0396 for 5190 reflections] has a ten-vertex {isocloso-1-IrB₉} cluster structure and also has an unsubstituted 1 -metallacyclopenta-2,4-diene system resulting from the oligomerisation of two acetylene molecules.