Unexpected differences in the reactivity between the phosphorus and arsenic derivatives [(CpBIGFe)2(μ,η4:4-E4)] (E = P and As).

Different reaction pathways were determined between thermolysis and photolysis reactions of the butterfly complex [{CpBIGFe(CO)2}2(μ,η1:1-As4)] (1b). The thermolysis leads to novel arsenic-rich compounds [(CpBIGFe)2(μ,η4:4-As4)] (2b), [(CpBIGFe)3(μ3,η4:4:4-As6)] (4) and [CpBIGFe(η5-As5)] (5), whereas the photolysis of [{CpBIGFe(CO)2}2(μ,η1:1-E4)] (1a: E = P; 1b: E = As) exclusively results in the decarbonylation products [(CpBIGFe)2(μ,η4:4-P4)] (2a), 2b and [(CpBIGFe)(μ,η4:1-As4)(CpBIGFe(CO)2)] (3). The E4 complexes 2a and 2b show unique structural differences in the solid state despite their related compositions.