Polyhedral ruthenaborane chemistry: characterization of several new ruthenaboranes by nuclear magnetic resonance spectroscopy, and the crystal and molecular structure of [5,6,6-(PPh3)3-6-H-nido-6-RuB9H12]

Abstract

Several new polyhedral ruthenaborane clusters have been synthesized, sometimes in high yield, by the reaction of borane anions with a variety of ruthenium(II) complexes such as [RuCl₂(PPh₃)₃],[RuH₂(PPh₃)₃], [RuCl₂(PPh₃)₄], and [Ru(CO)CIH(PPh₃)₃]. Thus arachno-[B₃H₈]^– yielded the colourless four-vertex ruthenaborane arachno-[(CO)(PPh₃)₂HRuB₃H₈](1), whereas nido-[B₅H₈]^– yielded the pale yellow five-vertex cluster nido-[(CO)(PPh₃)₂RuB₄H₈](2) and the six-vertex cluster nido-[(CO)(PPh₃)₂RuB₅H₉](3). An interesting series of 6-ruthena-nido-decaboranes was also synthesized: arachno-[B₉H₁₄]^–(and, less effectively, deprotonated nido-B₁₀H₁₄) yielded orange nido-[(CO)(PPh₃)₂RuB₉H₁₃](4) and light yellow nido-[(CO)(PPh₃)₂RuB₉H₁₁(PPh₃)](5), whilst ^nido-[B₉H₁₂]^– afforded amber-red crystals of ₃nido-[(PPh₃)₂HRuB₉H₁₂(PPh₃)](6). Structures have been assigned on the basis of detailed ¹H, ¹¹B, and ³¹P n.m.r. studies and comparison with iron, osmium, and iridium analogues where these are known. The structure of [5,6,6-(PPh₃)3-6-H-nido6-RuB₉H₁₂](6) was confirmed by a single-crystal X-ray diffraction study; the monoclinic crystals contained 0.25CH₂Cl₂ as solvent of crystallization [a=1 263.2(5), b=1 786.2(3), c= 2 692.8(9) pm, β= 95.09(3)°, U= 6.256 nm³, space group P2₁/c, and Z= 4]. All thirteen H atoms on the cluster were located and freely refined with individual isotropic thermal parameters.