SYNTHESIS AND CHEMISTRY OF THE ARYLIRIDIUM(III) FLUORIDES CP'IR(PME(3))(ARYL)F - HIGH REACTIVITY DUE TO SURPRISINGLY EASY IR-F IONIZATION

This paper reports the synthesis and chemistry of the unusual late met al fluoride complexes, Cp'Ir-(PMe(3))(Aryl)F [Cp' = Cp (C(5)Me(5)), A ryl = Ph (1a); Cp' = Cp, Aryl = p-tolyl (1b); Cp' = Cp(Et) (C(5)Me(4) Et), Aryl = Ph(1c)]. The solid-state structure of Ic has been determin ed: crystals of 1c are monoclinic, space group P2(1)/c, with a = 9.235 (2) Angstrom, b = 12.667(2) Angstrom, c = 17.129(3) Angstrom, beta 104 .547(16)degrees, and Z = 4; R = 3.98%, wR = 4.65% for 2859 data for F- 2 > 3 sigma(F-2). These complexes exhibit reactivity that is substanti ally different from that of related Cl, Pr, and I species because of t he greater propensity of fluoride ion to dissociate from the Ir center , even in nonpolar solvents. For example, in solution at room temperat ure, fluoride is slowly displaced from complexes 1 by Lewis bases such as pyridines and phosphines (L); the resulting salts [Cp'Ir(PMe(3))(A ryl)(L)]F (2) exist in equilibrium with the covalent starting material s. This equilibrium Lies well to the left for pyridines and phosphines under anhydrous conditions, but both the rate of establishment and th e magnitude of K-eq are increased dramatically by the addition of H2O. In aqueous THF the aquo species [CpIr(PMe(3))(Ph)(OH2)]F . xH(2)O (2 e) is formed much more rapidly than the [Cp'Ir(PMe(3))(Aryl)(L)]F salt s. This, and the rapid further reactivity of 2e, enables the aquo spec ies to serve as an intermediate in the water-catalyzed substitution of fluoride by L. Treatment of la with mixtures of water and other enter ing ligands and monitoring these reactions over time reveals that the kinetic affinity of these ligands for the Ir center is exactly the rev erse of their thermodynamic affinity: kinetically, H2O > pyridines > p hosphines; thermodynamically, phosphines > pyridines > H2O. Addition o f BPh(3) to [Cp'Ir(PMe(3))(Aryl)(L)]F (2) in nonaqueous media leads to irreversible formation of the berate complexes, [Cp'Ir(PMe(3))(Aryl)( L)]BPh(3)F. The lability of the fluoride Ligand in complexes 1 is also demonstrated by mixing CpIr(PMe(3))(Ph)F with Cp*Ir(PMe(3))(p-tolyl) X IX Cl, Pr, OTf, OPh] in C6D6, which leads to solutions containing fo ur species identifiable as the two starting materials and the two exch ange products CpIr(PMe(3))Ph)X and Cp*Ir(PMe(3))p-tolyl)F. Organic ha lides participate in exchange as well; reaction of la with PhCH(2)Br, Me(3)SiCl, MeCOCl, and even CH2Cl2 results in complete replacement of fluoride by bromide or chloride in la. The labile fluoride ion also le ads to other novel reactivity. For example, addition of dimethyl acety lenedicarboxylate to complexes 1 gives iridacyclopentadiene complexes (5) and reaction of la and Ic with (l-trimethylsilyl)imidazole provide s Cp'Ir(PMe(3))(Ph)(imidazolate) complexes (7) and Me(3)SiF. Treatment of 1 with silanes HSiMe(2)R [R = Ph, Me] leads to the formation of Cp 'Ir(PMe(3))(R)(SiMe(2)F) complexes(8); excess HS-p-tolyl reacts with e ither 1a or 1b to provide CpIr(PMe(3))(S-p-tolyl)(2) (10).