The preparation of electrophilic and electroneutral phosphane ligands and their substitution chemistry with Mo(CO)6

The synthesis, characterization and coordination chemistry of electroneutral and electron-poor phosphane ligands is reported. The addition of diaminochlorophosphanes [compounds of the type (R2N)2PCl] to ether solutions of C2F5Li produced the corresponding diaminopentafluoroethylphosphane compounds (R2N)2PC2F5 (R2N = C4H8ON, 1; C5H10N, 2; and C8H8N, 3). Similar treatment of aminodichlorophosphanes with two equivalents of C2F5Li produced compounds of the type (R2N)P(C2F5)2 (R = C4H8ON, 4; C5H10N, 5; C4H8N, 6; and C8H8N, 7). These phosphanes were isolated as high boiling liquids (1, 2, 4–7) or as a solid (3) in moderate yields (44–71%). Substitution reactions of one equivalent of 1–6 with Mo(CO)6 yielded the corresponding pentacarbonyl complexes (L)Mo(CO)5 (1a–6a). Thermolysis of 7 with Mo(CO)6 did not yield the expected pentacarbonyl complex. The phosphane compounds 1–7 and their molybdenum derivatives 1a–6a were characterized by multinuclear NMR; the CF2 region in the 19F NMR for compounds 4–7 and complexes 4a–6a displayed second-order character which complicated their interpretation. Compounds 1a–6a were also characterized by IR spectroscopy; the IR stretching frequencies for these complexes suggest that ligands 1–3 are electroneutral (and approximate the electronic influence of phosphites) while similar stretching frequencies for 4a–6a clearly establish these ligands as electrophilic.