METALLABORANE REACTION CHEMISTRY .1. 2 INTERESTING CLOSED CLUSTER COMPOUNDS FROM THE REACTION OF ACETYLENE WITH AN OPEN NIDO-6-IRIDADECABORANE

The passing of acetylene through a refluxing solution in benzene of [6,6,6-(PPh3)H(Ph2P-ortho-C6H4)-nido-6-IrB9H12-5] results in the formation of the closo ten-vertex [2,2,2-(PH3)2(Ph2P-ortho-C6H4)-closo-2-IrB9H7-10-(PPh3)-1) 4 (up to 95% based on phosphine content; 47% based on iridium content) and [1,1,1-(CH=CH-CH=CH)(Ph2P-ortho-C6H4)-isocloso-1-IrB9H7-5-(PPh3)-2] 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, beta = 97.86(1)-degrees, and Z = 4; space group P2(1)/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, beta = 116.69(2)-degrees, and Z = 4; space group P2(1)/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.