Pentamethylcyclopentadienylrhodaborane chemistry. Part 5. Preparation, molecular structure, and nuclear magnetic resonance spectra of the arachno ten-vertex rhodadecaboranes [6-(η5-C5Me5)-6,9-(RNC)2-arachno-6-RhB9H11](R = Me or p-MeC6H4)

Abstract

The reaction of MeNC with [6-(η⁵-C₅Me₅)-nido-6-RhB₉H₁₃](1) results in the formation of yellow air-stable [6-(η⁵-C₅Me₅)-6,9-(MeNC)₂-arachno-6-RhB₉H₁₁](2) in 64% yield. The product was characterized by n.m.r. spectroscopy, and the structural type confirmed by a single-crystal X-ray diffraction analysis on the p-MeC₆H₄NC analogue, yellow, air-stable [6-(η⁵-C₅Me₅)-6,9-(p-MeC₆H₄NC)₂-arachno-6-RhB₉H₁₁](3), obtained in the much lower yield of ca. 5% from the reaction of the nido compound (1) with p-MeC₆H₄NC. Crystals of (3) were triclinic, space group P, with a= 1 307.4(2), b= 1 264.6(2), c= 1 093.1(1) pm, α= 115.23(1), β= 85.05(1), γ= 110.37(1)°, and Z= 2; R factor 0.0312 for 5 138 observed reflections [I > 2.0σ(I)]. The two p-MeC₆H₄NC ligands are in the Rh(6)-endo and B(9)-exo configuration.