NONCLASSICAL METAL-CARBONYLS - [AG(CO)](+) AND [AG(CO)(2)](+)

The synthesis and characterization of salts of the cationic silver(I) carbonyl complexes [Ag(CO)](+) and [Ag(CO)(2)](+) are reported. The counterions used include OTeF5- and the weakly coordinating anions B(OTeF5)(4-), Zn(OTeF5)(4)(2-), Nb(OTeF5)(6-), and Ti(OTeF5)(6)(2-). Despite the fact that carbon monoxide is reversibly bound to silver(I), these compounds are stable enough to be isolated as crystalline solids under a CO atmosphere or at low temperatures. Two of the new compounds, [Ag(CO)][B(OTeF5)(4)] and [Ag(CO)(2)][B(OTeF5)(4)], were studied by single-crystal X-ray diffraction. A combination of manometric, spectroscopic, and diffraction results suggests little or no Ag --> CO pi-backbonding in these complexes, which makes them rare examples of sigma-only metal carbonyls (and for which we propose the name nonclassical metal carbonyls). The data include the following: nu(CO) values, which range from 2189 to 2220 cm(-1) solid-state delta(C-13) values, which are similar to 171; J109(Ag)13(C) values, which range from 190 to 284 Hz; chemical shift anisotropies, which range from -45(5) to -76(5) ppm for sigma(parallel to) and from 280(5) to 295(5) ppm for sigma(perpendicular to); Ag-C and C-O bond distances for [Ag(CO)][B(OTeF5)(4)] which are 2.10(1) and 1.077(16) Angstrom, respectively; and Ag-C and C-O bond distances for the three unique cations in [Ag(CO)(2)][B(OTeF5)(4)], which range from 2.06(5) to 2.20(4) Angstrom and from 1.07(5) to 1.09(6) Angstrom, respectively. For [Ag(CO)][B(OTeF5)(4)], monoclinic, P2(1)/n: a = 10.001(2) Angstrom, b = 16.180(4) Angstrom, c = 12.235(3) Angstrom, beta = 100.48(2)degrees, Z = 4, T = -125 degrees C, R = 0.040. For [Ag(CO)(2)][B(OTeF5)(4)], triclinic, <P(1)over bar>: a = 10.367(5) Angstrom, b = 13.146(7) Angstrom, c = 16.56(1) Angstrom, alpha = 87.77(5)degrees, beta = 76.38(4)degrees, gamma = 89.06(4)degrees, Z = 4, T = -100 degrees C, R = 0.078. The structure of [(CH3)(2)CHCO][SbCl6] was redetermined at low temperature by single-crystal X-ray diffraction. The C-O distance in the acylium cation was found to be 1.101(4) Angstrom, significantly shorter than the 1.12822(7) Angstrom bond distance in gaseous CO. For [(CH3)(2)CHCO][SbCl6], orthorhombic, Pnma: a = 19.368(1) Angstrom, b = 7.055(1)Angstrom, c = 9.108(1) Angstrom, Z = 4, T = -130 degrees C, R = 0.020.