Syntheses and Carbonyliridium Complexes of Unsymmetrically Substituted Fluorous Trialkylphosphanes: Precision Tuning of Electronic Properties, Including Insulation of the Perfluoroalkyl Groups

Abstract

Reactions of iodides I(CH2)mRf8 [m = 2−4; Rf8 = (CF2)7CF3] and LiPH2 · DME (−45 °C, THF) give the primary phosphanes PH2(CH2)mRf8 (7−9; 48−76%). Radical-initiated reactions (100 °C) of 7 and H2C=CHCH2Rf8, 8 and H2C=CHRf8 or H2C=CHCH2CH2Rf8, and 9 and H2C=CHCH2Rf8, give the title phosphanes P[(CH2)mRf8]2[(CH2)m′Rf8] [m/m′ = 2/3 (10), 3/2 (11), 3/4 (12), 4/3 (13); 70−76%]. The symmetrically substituted phosphane P[(CH2)mRf8]3 (m = 5, 6) is similarly prepared from PH3 and H2C=CHCH2CH2CH2Rf8, analogously to previously reported homologs [m = 2 (2), 3 (4), 4 (5)]. Reactions of 10−13 and 2, 4, 5, and 6 with [Ir(COD)Cl]2 and CO give trans-Ir(CO)(Cl)(PR2R′)2 (70−83%). The IR νCO values show a monotonic decrease with increasing numbers of CH2 groups. Phosphanes 13, 5, and 6 have the most CH2 groups, and give νCO values 10, 7, and 4 cm−1 higher than the unfluorinated phosphane P[(CH2)7CH3]3. Hence, 6 provides nearly complete insulation of the iridium center from the electronegative perfluoroalkyl groups. Analogous rhodium derivatives of 4 and 5 are also described.