Iridium(III, 0, and -I) Complexes Stabilized by 1,1 '-bis(diphenylphosphino)ferrocene (dppf): Synthesis and Characterization. Crystal Structures of [Na(THF)(5)][Ir(dppf)(2)]center dot THF and [Ir(dppf)(2)]

The iridium(I) complex stabilized by the organometallic ligand 1,1 '-bis(di phenylphosphino)ferrocene (dppf), [Ir(dppf)(2)](+), 1, undergoes a cyclomet alation reaction in solution to give the iridium(III) hydride [IrH(dppf(-H) )(dppf)(+),2 2, which has been isolated and characterized by spectroscopic methods. The compound is the final product of the intramolecular oxidative addition of the ortho C-H bond of a phenyl substituent of the diphosphine a nd is formed through an intermediate hydride, which has also been spectrosc opically characterized. 1 can be electrochemically reduced to the Ir(0) and Ir(-I) species, [Ir(dppf)(2]), 3, and [Ir(dppf)(2])(-), 4, respectively, i n two reversible single-electron processes. These low-valent metal complexe s have been obtained by chemical reduction of 1 with sodium naphthalenide i n tetrahydrofuran solution and their crystal and molecular structures deter mined by single-crystal X-ray analyses. 3 crystallizes in the triclinic sys tem, space group P (1) over bar, with a 13.019(4) Angstrom, b 13.765(6) Ang strom, c 15.549(5) Angstrom, alpha = 93.74(3)degrees, beta = -90.35(3)degre es, gamma = 92.07(3)degrees, V = 2779(2) Angstrom(3), and Z = 2. Anionic co mplex 4 crystallizes as sodium-solvated salt [Na(THF)(5)][Ir(dppf)(2)]. THF , 4b, in which the sodium cation is surrounded by five molecules of THF in a slightly distorted trigonal-bipyramidal environment. 4b crystallizes in t he monoclinic system, space group P2(1)/n, with a = 13.325(3) Angstrom, b 2 3.976(5) Angstrom c 26.774(7) Angstrom, beta = 98.77(2)degrees,V=8454(4) An gstrom(3), and Z = 4. The coordination geometry around the metal in neutral d(9) complex 3 is intermediate between the highly distorted square-planar geometry, found earlier in cationic d(8) species 1, and the almost regular tetrahedral arrangement of the two diphosphines in the anionic d(10) comple x 4. Reduction of Ir(I) to Ir(0) and Ir(-I) causes a stepwise decrease of t he Ir-P bond length of 0.04 Angstrom (average) and 0.05 Angstrom, respectiv ely, with a concomitant increase of the bite angle of the diphosphine which ranges from 94.3 degrees (average) in [Ir(dppf)(2)](+) to 102.3 degrees in [Ir(dppf)(2)](-).