DIPHOSPHA-FERROCENES AND TRIPHOSPHA-FERROCENES - CRYSTAL AND MOLECULAR-STRUCTURES OF [FE(ETA(5)-C(5)ME(5))(ETA(5)-C(3)(T)BU(3)P(2))] AND OFTHE ADDUCTS A(5)-C(5)ME(5))(ETA(5)-C(2)(T)BU(2)P(3))MO(CO)(5)] AND TA(5)-C(5)ME(5))(ETA(5)-C(2)(T)BU(2)P(3))W(CO)(5)]

Synthesis and structural studies of the iron ''sandwich'' complex [Fe( eta(5)-C(5)Me(5))(eta(5)-C(3)(t)Bu(3)P(2))] 1 are described. The lone pair electrons of the two adjacent phosphorus atoms of the C(2)(t)Bu(2 )P(3) ring in the triphospha-ferrocene complex [Fe(eta(5)-C(5)Me(5))(e ta(5)-C(2)(t)Bu(2)P(3))] 2 can ligate to other metal centres. The resu lts of single crystal X-ray structural studies of the molybdenum and t ungsten pentacarbonyl eta(1)-complexes ta(5)-C(2)Me(5))(eta(5)-C(2)(t) Bu(2)P(3))M(CO)(5)] (4: M = Mo, 5: M = W) are discussed: they form an isostructural series with the previously reported chromium complex. Th e starting material 2 reacts with [(C(5)H(4)Me)(CO)(2)Mn(THF)] to form the adduct (5)-C(2)(t)Bu(2)P(3))Mn(CO)(2)(eta(5)-C(5)H(4)Me)] 6. The phenyl-substituted di- and triphosphacyclopentadienides [Na(DME)(3)][C (3)Ph(3)P(2)] and [Na(DME)(3)][C(2)Ph(3)P(2)] (DME = 1,2-dimethoxyetha ne) react with ferrous chloride and Li[C(5)Me(5)] to give the 'sandwic h' compounds [Fe(eta(5)-C(5)Me(5))(eta(5)-C(3)Ph(3)P(2))] 9 and [Fe(et a(5)-C(5)Me(5))(eta(5)-C(2)Ph(2)P(3))] 10. The later reacts with W(CO) (5)(THF) to yield the eta(1)-complex e(eta(5)-C(5)Me(5))(eta(5)-C(2)Ph (2)P(3))W(CO)(5)] 11.