Abstract
The bis(ferrocenyl)phosphenium ion, [Fc2P]+, reported by Cowley et al. (J. Am. Chem. Soc. 1981, 103, 714–715), was the only claimed donor‐free divalent phosphenium ion. Our examination of the molecular and electronic structure reveals that [Fc2P]+ possesses significant intramolecular Fe⋅⋅⋅P contacts, which are predominantly electrostatic and moderate the Lewis acidity. Nonetheless, [Fc2P]+ undergoes complex formation with the Lewis bases PPh3 and IPr to give the donor–acceptor complexes [Fc2P(PPh3)]+ and [Fc2P(IPr)]+ (IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazole‐2‐ylidene).
Highlights
714–715), was the only claimed donor-free divalent phosphenium ion
31P NMR spectroscopy it was concluded that the positive charge was formally situated at phosphorus and that the iron atoms are in the oxidation state II
The claim was further supported by the ability of [Fc2P]+ to react as a Lewis acid towards the Lewis base n-Bu3P, giving rise to the donor– acceptor complex [Fc2P(Pn-Bu3)]+.[6]
Summary
714–715), was the only claimed donor-free divalent phosphenium ion. Our examination of the molecular and electronic structure reveals that [Fc2P]+ possesses significant intramolecular Fe···P contacts, which are predominantly electrostatic and moderate the Lewis acidity. In the donor–acceptor complexes 3 and 4, the P1-P2 (2.2335(5) ) and P1-C1 (1.865(2) ) bond distances compare well with those found in the related compounds [Ph2P(PPh3)][GaCl4][14] (2.220(6) ) and [Ph2P(SIMes)][B(C6F5)4] (1.861(4) , SIMes = 1,3-dimesitylimidazolidin-2-ylidene).[15] No other major structural features were observed around the [Fc2P]+ fragments in these complexes, which indicates that the ligands effectively compensate most of the positive charge on P1.
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