SYNTHESIS, STRUCTURE, AND LIGAND BEHAVIOR OF THE 1,2-DIPHOSPHAFERROCENE ))(ETA(5)-(3,4-(ME(3)SIO)(2)-5-(ME(3)SI)P2C(3))FE]

Reaction of equimolar amounts of (eta(5)-1,3-tBu(2)C(5)H(3))(CO)(2)-Fe P(SiMe(3))(2) with bis(trimethylsilyl)methylenechlorophosphane afforde d the 1-metallo-1,2-diphosphapropene -tBu(2)C(5)H(3))(CO)(2)FeP(SiMe(3 ))P=C(SiMe(3))(2) (1b). Treatment of 1b with an excess of [(Z)-cyclooc tene]Cr(CO)(5) furnished 1,2-diphosphaferrocene {1-[Cr(CO)(5)]-3,4(Me( 3)SiO)(2)-5-(Me(3)Si)P2C3}Fe (4b). Chromium complex 4b was freed from the pentacarbonylchromium fragment by heating with 1.5 equiv, of [Fe-2 (CO)(9)] in toluene solution at 80-90 degrees C affording sandwich 5. In contrast, treatment of 4c with [Fe-2(CO)(9)] in refluxing n-pentane yielded the trinuclear complex [Fe-2(CO)(7)]-3,4-(Me(3)SiO)(2)-5-(Me( 3)Si)P2C3}Fe (6). The ligation of sandwich 5 to the [Fe(CO)(4)] unit i n 7 was achieved by irradiation with [Fe(CO)(5)] in n-pentane solution . A tricarbonylnickel adduct 8 resulted from the reaction of 4b with a n excess of [Ni(CO)(4)] in toluene at ambient temperature. The molecul ar structures of the complexes 6 and 8 were established by single-crys tal X-ray structure analyses. Cyclovoltammetric studies with 4b, 5, an d 8 revealed an anodic shift of the oxidation potential when changing from 5 to 8 and 4.