Insertion of Phosphenium Ions into a Bicyclo[1.1.0]Tetraphosphabutane Iron Complex

By reacting [{Cp‴Fe(CO)(2)}(2)(µ,η(1:1)-P(4))] (1) with in situ generated phosphenium ions [Ph(2)P][A] ([A](−) = [OTf](−) = [O(3)SCF(3)](−), [PF(6)](−)), a mixture of two main products of the composition [{Cp‴Fe(CO)(2)}(2)(µ,η(1:1)-P(5)(C(6)H(5))(2))][PF(6)] (2a and 3a) could be identified by extensive (31)P NMR spectroscopic studies at 193 K. Compound 3a was also characterized by X-ray diffraction analysis, showing the rarely observed bicyclo[2.1.0]pentaphosphapentane unit. At room temperature, the novel compound [{Cp‴Fe}(µ,η(4:1)-P(5)Ph(2)){Cp‴(CO)(2)Fe}][PF(6)] (4) is formed by decarbonylation. Reacting 1 with in situ generated diphenyl arsenium ions gives short-lived intermediates at 193 K which disproportionate at room temperature into tetraphenyldiarsine and [{Cp‴Fe(CO)(2)}(4)(µ(4),η(1:1:1:1)-P(8))][OTf](2) (5) containing a tetracyclo[3.3.0.0(2,7).0(3,6)]octaphosphaoctane ligand.