Phosphasilene

Schematic illustration of a generic phosphasilene with a three-coordinate silicon atom and a two-coordinate phosphorus atom.

Phosphasilenes or silylidenephosphanes are a class of compounds with silicon-phosphorus double bonds.[1] Since the electronegativity of phosphorus (2.1) is higher than that of silicon (1.9), the "Si=P" moiety of phosphasilene is polarized.[2][3] The degree of polarization can be tuned by altering the coordination numbers of the Si and P centers, or by modifying the electronic properties of the substituents.[2] The phosphasilene Si=P double bond is highly reactive, yet with the choice of proper substituents, it can be stabilized via donor-acceptor interaction or by steric congestion.[3]

Structure of the first phosphasilene prepared by Bickelhaupt et al.[4]

The landmark discovery of the first phosphasilene by NMR spectroscopy was made in 1984 by Bickelhaupt et al.[4] The first phosphasilene came with bulky aryl substituents at the phosphorus and silicon atoms.[4] Almost a decade after this spectroscopic observation, the first structural characterization of phosphasilene was achieved in 1993 by Niecke et al.[5] The successful isolation of phosphasilenes with silicon-phosphorus double bonds represents one of the discoveries that challenged and disproved the "double-bond rule".

  1. ^ Driess, M. (1994). "Some Aspects of the Chemistry of Silylidene-Phosphanes and -Arsanes". Coord. Chem. Rev. 145: 1–25. doi:10.1016/0010-8545(95)90212-0.
  2. ^ a b Nesterov, V.; Breit, N.; Inoue, S. (2017). "Advances in Phosphasilene Chemistry". Chem. Eur. J. 23 (50): 12014–12039. doi:10.1002/chem.201700829. PMID 28379639.
  3. ^ a b Hansen, K.; Szilvási, T.; Blom, B.; Driess, M. (2015). "Transition Metal Complexes of a "Half-Parent" Phosphasilene Adduct Representing Silylene→Phosphinidene→Metal Complexes". Organometallics. 34 (24): 5703–5708. doi:10.1021/acs.organomet.5b00772.
  4. ^ a b c Smit, C. N.; Lock, F. M.; Bickelhaupt, F. (1984). "2,4,6-Tri-tert-butylphenylphosphene-Dimesitylsilene; The First Phosphasilaalkene". Tetrahedron Lett. 25 (28): 3011–3014. doi:10.1016/S0040-4039(01)81351-4.
  5. ^ Bender, H. R. G.; Niecke, E.; Nieger, M. (1993). "The First X-ray Structure of a Phosphasilene: 1,3,4-Triphospha-2-silabutene-(1)". J. Am. Chem. Soc. 115 (8): 3314–3315. doi:10.1021/ja00061a034.