Coordination Behavior of a P4 -Butterfly Complex towards Transition Metal Lewis Acids: Preservation versus Rearrangement.

The reactivity of the P4 butterfly complex [{Cp'''Fe(CO)2 }2 (μ,η1:1 -P4 )] (1, Cp'''=η5 -C5 H2 tBu3 ) towards divalent Co, Ni and Zn salts is investigated. The reaction with the bromide salts leads to [{Cp'''Fe(CO)2 }2 (μ3 ,η2:1:1 -P4 ){MBr2 }] (M=Co (2Co), Ni (2Ni), Zn (2Zn)) in which the P4 butterfly scaffold is preserved. The use of the weakly ligated Co complex [Co(NCCH3 )6 ][SbF6 ]2 , results in the formation of [{(Cp'''Fe(CO)2 )2 (μ3 ,η4:1:1 -P4 )}2 Co][SbF6 ]3 (3), which represents the second example of a homoleptic-like octaphospha-metalla-sandwich complex. The formation of the threefold positively charged complex 3 occurs via redox processes, which among others also enables the formation of [{Cp'''Fe(CO)2 }4 (μ5 ,η4:1:1:1:1 -P8 ){Co(CO)2 }][SbF6 ] (4), bearing a rare octaphosphabicyclo[3.3.0]octane unit as a ligand. On the other hand, the reaction with [Zn(NCCH3 )4 ][PF6 ]2 yields the spiro complex [{(Cp'''Fe(CO)2 )2 (μ3 ,η2:1:1 -P4 )}2 Zn][PF6 ]2 (5) under preservation of the initial structural motif.