The new metal-metal-bonded (fulvalene)dimolybdenum carbonyl complexes FVMo2(CO)(4)L(2) (L = PPh(3), PCy(3), PXy(3); Xy = 3,5-dimethylphenyl) were synthesized via (af hydride hydrogen atom abstraction from FVMo2(CO)(4)L(2)H(2) (L = PPh(3), PXy(3)) by trityl radicals, (b) sodium reduction of FVMo2(CO)(4)L(2)Cl(2) (L = PPh(3), PCy(3), PXy(3)), and (c) oxidation of the dianions [FVMo2(CO)(4)L(2)](2-) (L = PPh(3), PCy(3)). The compounds were characterized by IR, UV-vis, and H-1, C-13{H-1} and P-31{H-1} NMR spectroscopy, and the spectroscopic data are in all cases consistent with structures containing the phosphines in positions trans to the Mo-Mo bond. The UV-vis spectra of trans-FvMo(2)(CO)(4)L(2) (L = PPh(3), PCy(3), PXy(3)) all exhibit a sigma --> sigma* transition at 374 nm, suggesting that the phosphines influence neither sterically nor electronically the Mo-Mo bond strength. Evidence for radical intermediates was found when FvMo(2)(CO)(4)(PPh(3))(2) was prepared from FvMo(2)(CO)(4)(PPh(3))(2)H-2.