Ten-vertex metallaborane chemistry: synthesis and characterization of some ortho-cycloboronated nido-5- and -6-iridadecaboranes; crystal structures of [5-H-5-(PPh3)-5-(PPh2-o-C6H4)-nido-5-IrB9H12-2] and [5-H-5,7-(PPh3)2-5-(PPh2-o-C6H4)-nido-5-IrB9H12-2]]

Abstract

The arachno-anion [B₉H₁₄]^– reacts with [IrCl(PPh₃)₃] to give an 80% yield of the known compound [6-H-6,6-(PPh₃)₂-nido-6-IrB₉H₁₃](1), whereas the reaction of nido-[B₉H₁₂]^– with [IrCl(PPh₃)₃] gives a mixture of products. These have been characterized by a combination of multi-element n.m.r. spectroscopy and single-crystal X-ray diffraction analysis to be [sym-6-H-6-(PPh₃)-6-(PPh₂-o-[graphic omitted]](2)(60% yield), [asym-6-H-6-(PPh₃)-6-(PPh₂-o-[graphic omitted]](3)(20% yield), [5-H-5-(PPh₃)-5-(PPh₂-o-[graphic omitted]](4)(0.1–20% yield) and [5-H-5,7-(PPh₃)₂-5-(PPh₂-o-[graphic omitted]](5)(5% yield). Crystals of compound (4) are triclinic, space group P with a= 1 254.4(3), b= 1 524.6(4), c= 1 091.7(2) pm, α= 97.69(2), β= 115.09(2), γ= 88.79(2)°, and Z= 2. Crystals of the bis(chloroform) solvate of (5) are triclinic, space group P with a= 1 501.3(3), b= 1 571.6(3), and c= 1 478.1 (3) pm, α= 104.27(2), β= 113.81 (2), γ= 97.98(2)°, and Z= 2. A further compound was isolated and tentatively identified as a phosphine-substituted nido-6-iridadecaborane. A scheme to explain the mixture of products is briefly discussed.