Synthesis and crystal structure of an acetylenic ferrocenyl substituted phosphaalkene

(E)-(5,5-Dimethyl-1,4-diferrocenylhex-2-yn-1-ylidene)(2,4,6-tri-tert-butylphenyl) phosphine (3) was obtained in the reaction of 2,4,6-tri-tert-butylphenyl phosphine (1) with 1,4-diferrocenyl butadiyne (2) in minor yields. Compound 3 was structurally characterized by single crystal X-ray diffraction. The molecular structure of 3 consists of a linear butyne C-4 backbone, which is in conjugation with a phosphene moiety resulting in the phosphapent-2-yn-4-ene motif with one ferrocenyl substituent bonded to a C-sp3 and the other one to the C-sp2 carbon atom. Both sandwich moieties are located at the same site of the C-4 axis opposing the tert-butyl groups. This results in an alternated stacking within the crystal packing along [0 1 0] with weak T-shaped pi interactions within the ferrocenyl containing layer. Electrochemical measurements revealed two reversible redox events for the two ferrocenyl groups at -20 mV and at 135 mV. (C) 2017 Elsevier B.V. All rights reserved.