Coinage metal carbonyls and isocyanides: Synthesis and characterization of the gold(I)complexes [HB(3,5-(CF3)(2)Pz)(3)]AuCO and [HB(3,5-(CF3)(2)Pz)(3)]AuCNBu(t)

Syntheses and IR spectroscopic and X-ray structural data for the gold(I) carbonyl and tert-butyl isocyanide complexes of the fluorinated tris(pyrazolyl)borate ligand [HB(3,5-(CF3)(2)Pz)(3)](-) (where HB(3,5-(CF3)(2)Pz)(3) = hydrotris(3,5-bis(trifluoromethyl)pyrazolyl)borate) are reported. The carbonyl complex [HB(3,5-(CF3)(2)Pz)(3)]AuCO (1) crystallizes in a triclinic unit cell, space group P (1) over bar, with a 8.3865(6) Angstrom, b 8.6467(6) Angstrom, c = 19.009(2) Angstrom, alpha 98.649(6)degrees, beta = 93.043(7)degrees, gamma = 117.446(6)degrees, V = 1197.5(2) Angstrom(3), Z = 2, and R = 0.0372. The gold atom adopts a distorted tetrahedral geometry with an Au-C distance of 1.862(9) Angstrom. The C-13 NMR spectrum of 1 displays a signal at delta 172.6 which corresponds to the carbonyl carbon. The nu(CO) of 1 (2144 cm(-1)) is similar to that observed for the copper(I) analog. Metal-CO distances and the C-O stretching frequencies of the coinage metal carbonyl adducts of [HB(3,5-(CF3)(2)Pz)(3)](-) follow the orders Ag > Au > Cu and Ag > Au greater than or equal to Cu, respectively. Crystals of [HB(3,5-(CF3)(2)Pz)(3)]AuCNBu(t) (2) are monoclinic, space group P2(1)/c, with a 12.082(2) Angstrom, b = 23.551(3) Angstrom, c = 10.780(2) Angstrom, beta = 106.683(12)degrees, V = 2938.4(7) Angstrom(3), Z = 4, and R = 0.0372. The gold atom coordinates to tris(pyrazolyl)borate in a highly asymmetric fashion with one short Au-N bond and two long Au-N separations. Corresponding Cu(I) and Ag(I) adducts display fairly symmetric structures with pseudotetrahedral metal sites. In the isocyanide series, the gold analog exhibits the highest nu(CN) whereas the Ag adduct has the longest metal-C distance. [HB(3,5-(CF3)(2)Pz)(3)]ML (M = Cu, Ag, Au; L = CO, CNBu(t)) complexes exhibit significantly reduced M-to-L back-bonding.