title: Novel synthetic approach to charge-compensated phosphonio-nido-carboranes. Synthesis and structural characterization of neutral mono and bis(phosphonio) nido-ortho-carboranes.
abstract: A number of monosubstituted n-(triphenylphosphonio)-7,8-dicarba-nido-undecaboranes (2a, n = 1; 2b, n = 3; 2c, n = 5; 2d, n = 9) were prepared via a cross-coupling reaction between the tetrabutylammonium iodo-7,8-dicarba-nido-undecaborates (1a-d) and PPh3 in the presence of a Pd(PPh3)4 catalyst. The substitution rate was found to depend on the iodine position in the carborane cage. Under similar conditions, the reaction of 5,6-diiodo- (3) and 9,11-diiodo-7,8-dicarba-nido-undecaborate (5) anions exclusively yielded the monosubstitution products 5-iodo-6-(triphenylphosphonio)-7,8-dicarba-nido-undecaborane (4) and 9-iodo-11-(triphenylphosphonio)-7,8-dicarba-nido-undecaborane (6), respectively. The reaction of tetrabutylammonium 6,9-diiodo-7,8-dicarba-nido-undecaborate (7) exclusively produced the phosphine substitution product in the open face of the nido-carborane, 6-iodo-9-triphenylphosphonio-7,8-dicarba-nido-undecaborane (8). The addition of a base (Cs2CO3, NaH) to the reactions of 3 and 5 with PPh3 afforded the corresponding bis(triphenylphosphonio)-7,8-dicarba-nido-undecaboranes, 9 and 10. Compound 10 was also prepared from 6 using the general procedure. The reaction of the triiodocarborane tetrabutylammonium 5,6,9-triiodo-7,8-dicarba-nido-undecaborate (11) with excess PPh3 in the presence of Cs2CO3 and Pd(PPh3)4 only produced neutral 5-iodo-6,9-bis(triphenylphosphonio)-7,8-dicarba-nido-undecaborane (12); no positively charged tris(phosphonio) species formed. The compositions of all prepared compounds were determined by multinuclear NMR spectroscopy and high-resolution mass spectrometry. The structures of compounds 2c, 6, 8, 9, and 12 were established by the X-ray diffraction analysis of single crystals.
authors: †International Institute of Nano and Molecular Medicine, School of Medicine and ‡Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States.
authors: Kuanysh Z
authors: KZ
authors: Kabytaev
authors: †International Institute of Nano and Molecular Medicine, School of Medicine and ‡Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States.
authors: Alexander V
authors: AV
authors: Safronov
authors: †International Institute of Nano and Molecular Medicine, School of Medicine and ‡Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States.
authors: Yulia V
authors: YV
authors: Sevryugina
authors: †International Institute of Nano and Molecular Medicine, School of Medicine and ‡Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States.
authors: Charles L
authors: CL
authors: Barnes
authors: †International Institute of Nano and Molecular Medicine, School of Medicine and ‡Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States.
authors: Satish S
authors: SS
authors: Jalisatgi
authors: †International Institute of Nano and Molecular Medicine, School of Medicine and ‡Department of Chemistry, University of Missouri, Columbia, Missouri 65211, United States.
authors: M Frederick
authors: MF
authors: Hawthorne
mesh_terms: D001896:Boron Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry; D008958:Models, Molecular; D009943:Organophosphorus Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry; D010720:Phosphines / Q000737:chemistry*; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*
chemical_list: D001896:Boron Compounds; D056831:Coordination Complexes; D009943:Organophosphorus Compounds; D010720:Phosphines; D000644:Quaternary Ammonium Compounds; D010165:Palladium; C009405:tetrabutylammonium