SYNTHESIS, STRUCTURE, FLUXIONAL BEHAVIOR, AND SUBSTITUTION-REACTION OF THE METAL-METAL-BONDED HETEROBIMETALLIC PHOSPHIDO-BRIDGED COMPLEX CPW(CO)(2)(MU-CO)(MU-PPH(2))FE(CO)(3)

The heterobimetallic phosphido-bridged complexes CpW(CO)(2)(mu-CO)(mu- PPh(2))Fe(CO)(3) (4) and CpW(CO)(3)(mu-PPh(2))Fe(CO)(4) (5) were prepa red by the reaction of CpW(CO)(3)PPh(2) with Fe-2(CO)(9). Photolysis o f 5 produced 4. The structures of 4 and 5 were determined by single-cr ystal X-ray diffraction. The W-Fe distance was 2.8308(22) Angstrom in 4, indicative of a W-Fe bond. The long distance between W and Fe (4.24 34(20) Angstrom) in 5 indicates no metal-metal bond in the complex. Fl uxional behavior involving the exchange of all CO ligands in 4 was stu died by variable-temperature C-13 NMR spectroscopy. Reaction between 4 and Lewis bases L (L = P(OMe)(3), PMe(3), PPh(2)H, PPh(3), PEt(3)) at ambient temperatures produced CpW(CO)(2)(mu-PPh(2))Fe(CO)(3)(L) (6) w ith L regiospecifically coordinated to Fe. However, 5 did not react wi th L under similar conditions. The structure of CpW(CO)(2)(mu-PPh(2))F e(CO)(3)(PPh(2)H) (6c) was determined by single-crystal X-ray diffract ion.