Synthesis, Structure, and Ligand Behavior of the 1,2‐Diphosphaferrocene [η 5 ‐1,3‐ t Bu 2 C 5 H 3 )(η 5 {3,4‐(Me3Si0)2‐5‐(Me3Si)P2C3} Fe]

Reaction of equimolar amounts of (η 5 ‐1,3‐ t Bu 2 C 5 H 3 )(CO)‐{3,4‐(Me 3 SiO) 2 ‐5‐(Me 3 Si)P 2 C 3 }Fe] 2 ‐FeP(SiMe 3 ) 2 with bis(trimethylsilyl)methylenechlorophosphane afforded the 1‐metallo‐1,2‐diphosphapropene (η 5 ‐1,3‐ t Bu 2 C 5 H 3 )(CO) 2 FeP (SiMe 3 )P = C(SiMe 3 ) 2 ( 1b ). Treatment of 1b with an excess of [(Z)‐cyclooctene]Cr(CO) 5 furnished 1,2‐diphosphaferrocene (η 5 ‐1,3‐ t Bu 2 C 5 H 3 )(η 5 ‐{1‐[Cr(CO) 5 ]‐3,4‐(Me 3 SiO) 2 ‐5‐(Me 3 Si)P 2 C 3 }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°C affording sandwich 5 . In contrast, treatment of 4c with [Fe 2 (CO) 9 ] in refluxing n ‐pentane yielded the trinuclear complex (η 5 ‐1,3‐ t Bu 2 C 5 H 3 ){η 5 ‐1,2‐[Fe 2 (CO) 7 ]‐3,4‐(Me 3 SiO) 2 ‐5‐(Me 3 Si)P 2 C 3 }Fe ( 6 ). The ligation of sandwich 5 to the [Fe(CO) 4 ] unit in 7 was achieved by irradiation with [Fe(CO) 5 ] in n ‐pentane solution. A tricarbonylnickel adduct 8 resulted from the reaction of 4b with an excess of [Ni(CO) 4 ] in toluene at ambient temperature. The molecular structures of the complexes 6 and 8 were established by single‐crystal X‐ray structure analyses. Cyclovoltammetric studies with 4b , 5 , and 8 revealed an anodic shift of the oxidation potential when changing from 5 to 8 and 4 .