2-CO-ORDINATE, 3-CO-ORDINATE AND 4-CO-ORDINATE GOLD(I) COMPLEXES OF 1,2-BIS(DIPHENYLPHOSPHINO)-1,2-DICARBA-CLOSO-DODECABORANE

Treatment of (PPh2)2C2B10H10 with gold(I)complexes [AuX(tht)] (tht = tetrahydrothiophene, X = Cl or C6F5) gives two-co-ordinate [(AuX)2{(PPh2)2C2B10H10}] or three-co-ordinate [AuX{(PPh2)2C2B10H10}] species. Other three-co-ordinate compounds have been prepared starting from [Au(tht)L]ClO4 (L = tht, PR3, or ylide) by reaction with the diphosphine. Substitution of tht in [Au(tht){(PPh2)2C2B10H10}]ClO4 affords [AuL{(PPh2)2C2B10H10}]ClO4 where, depending on the ligand, three-co-ordinate (L = SPPh3, AsPh3, or C5H4NSH) or four-co-ordinate complexes [L = 1,10-phenanthroline or (PPh2)2C2B10H10] can be synthesised. The bis-chelated gold(I) phosphine complex [Au{(PPh2)2C2B10H10}2]ClO4 has been isolated. The crystal structure of [Au(PPh3){(PPh2)2C2B10H10}]ClO4.CH2Cl2 has been established by X-ray crystallography: monoclinic space group P2(1)/n, a = 11.760(3), b = 20.290(5), c = 21.375(6) angstrom, beta = 105.10(2)-degrees, Z = 4, R = 0.032. The gold atom exhibits trigonal-planar co-ordination, by three phosphorus atoms with Au-P 2.318(1), 2.405(1) and 2.417(1) angstrom (the longer bonds are to the diphosphine).