(FLUOROALKYL)PHOSPHINE HYDRIDE COMPLEXES OF IRIDIUM - SYNTHESIS AND STRUCTURES OF (DFEPE)2IRH AND (DFEPE)2IR2(H)(MU-H)2(MU-O3SCF3)

The synthesis and characterization of a series of (fluoroalkyl)phosphine complexes of iridium are described. Treatment of [(cod)Ir(thf)2]OTf with (C2F5)2PCH2CH2P(C2F5)2(''dfePe'') affords [(dfepe)Ir(cod)]OTf (1), which serves as a versatile precursor to a variety of (dfepe)Ir complexes. Reaction of 1 with acetonitrile yields [(dfepe)Ir(MeCN)2]OTf (2). In the presence of free dfepe, the hydrogenolysis of 1 affords the cationic dihydride cis-[(dfepe)2Ir(H)2]OTf (3), which is readily deprotonated by weak bases to give the structurally characterized neutral hydride (dfepe)2IrH (4). Protonation of 4 to regenerate (dfepe)2Ir(H)2+ is effected only by the strong acid HOTf. Although 4 is stabile toward MeCN, 3 readily loses one dfepe ligand in MeCN solvent to give [(dfepe)Ir(MeCN)(H)2]OTf (7). Treatment of 4 with CO, however, results in the clean displacement of one dfepe ligand to form (dfepe)Ir(CO)2H (6). Hydrogenolysis of 1 in the absence of dfepe or donor solvents leads to the formation of the sparingly soluble symmetrical dimeric Ir(III) polyhydride [(dfepe)Ir(H)(mu-H)(OTf)]2 (8). Like 3,8 is highly acidic and readily deprotonates to form the asymmetric dimer (dfepe)2Ir2(H)(mu-H)2(mu-O3SCF3) (9). The presence of a bridging triflate ligand in 9 has been confirmed by X-ray crystallography. Attempts to further deprotonate 9 to form the parent [(dfepe)Ir(mu-H)]2 have thus far been unsuccessful. Crystal data for 4: orthorhombic, P2(1)2(1)2(1), with a = 11.706(4) angstrom, b = 16.449(5) angstrom, c = 18.497(5) angstrom, V = 3572.5(5) angstrom3, Z = 4, R(F) = 6.45%, and R(wF) = 6.65%. Crystal data for 9: monoclinic, P2(1)/n, with a = 10.915(3) angstrom, b = 19.967(4) angstrom, c = 19.898(5) angstrom, beta = 102.58(2)-degrees, V = 4232(2) angstrom3, Z = 4, R(F) = 6.25%, and R(wF) = 8.43%.