Bis-methylene-phosphorane

A further example of the diazaphosphole synthesis by [3 + 2] cycloaddition is given by the reaction of a phosphoranediyl diazomethane (26) (R = NPr j) with P-chloro-bis(trimethylsilyl)-phosphaethene. The adduct loses trimethylchlorosilane and yields a 3-phosphoranediyl-l,2,4-diazaphosphole (or 3-phosphonio-l,2,4-diazaphospholide) (27). The analogous addition to the trimethylsilyl substituted P-chloro-bis(methylene)phosphorane (28) yields a 4-methylene derivative (29) of this diazaphosphole (molecular structure in Table 1). It provides the only fully characterized example of this type up to 1995. Methyl triflate methylates the compound at N-1 and gives a phosphonio methylene diazaphosphole cation (30). 

Scheme 5 Bis-methylene-phosphorane-type bonding with the usual notations and resonance structures...

Scheme 6 Possible participation of bis-methylene-phosphorane-type bonding in Ji-systems...

Like ylides, bis-methylene-phosphoranes can also be built into 7i-systems in different ways (see Scheme 6), with one of the P=E bonds in an exocyclic position, or with the entire 3c-4e 7i-system incorporated into the cyclic delocalization. 

The bis(methylene)phosphoranes hold two carbon atoms doubly bonded to the same phosphorus atom. The molecule is chiral in the solid state due to the propeller-like orientation of the silyl groups as demonstrated in Fig. 2. 

The deprotonation of amino-bis(methylene)phosphoranes leads to imino-bis(methylene) phosphate anions, which show one PN and two PC double bonds [Eq. (11)] (50a). 

The availability of phosphaalkenes led to a second route to phosphiranes with diazoalkanes as cycloaddition partners compare with Scheme 14. The first formed 4,5-dihydro-3//-l,2,4-diazaphospholes 43 decompose under the influence of light and extrusion of nitrogen to form the bis(methylene) phosphoranes 44, which cyclize in a 47t-electro-cyclic closure to the phosphiranes 45 (Scheme 17) <1996CHEC-II(I)298>. For the theoretical background, see Section 1.08.2.1.1, and for analogous reactions see <1995CC25> and <1997CB779>. 

Although strictly outside the remit of this chapter, it is appropriate to note continued activity in the chemistry of c X -p -bonded phosphorus compounds that do not possess a lone pair of electrons at phosphorus. A monomeric metaphosphonate species (262, X=0) has been stabilised by coordination via the P=0 bond), and Harger s group has provided evidence of the intermediacy of metathiophosphonates (262, X=S) in the reactions of phosphonami-dothioic acids with alcohols.The cation (263) has been stabilised by coordination at phosphorus with 4-dimethylaminopyridine and the reactivity of bis(methylene)phosphoranes (264) and related phosphoranylidene car-benoids has been investigated. ... 

EPR spectroscopy has been used to determine the bonding and structure in copper(II) complexes with N-(thio)-phosphorylated thioamides 51 in a study of the role of hydrogen atoms and hydroxyl radicals in glycerol-1-phosphate degradation, and in a thermo- and surface-chemistry study of dimyristoylpho-sphatidylcholine (DMPC) and dimyristoylphosphatidylglycerol (DMPG) bilayers in the (La + H2O) phase.EPR spectroscopy has also been used to characterise novel oligo(cation radicals) of methylene phosphoranes and di(cation radicals) of a 1,3-phenylene-bis(methylene phosphorane) (52). ... 

Reports of iron complexes containing bis(methylene)phosphoranes include the preparation and X-ray structure determination of (63).37 The directly coordinated bis(methylene)phosphorane-iron complex (64) under-... 

Commercial development of calcium polyphosphate fibres Discovery of new class of aluminophosphate molecular sieves Preparation of first carbophosphene - (bis methylene phosphorane) Discovery of Phospha-Cope rearrangement Synthesis of first compound with an As=P bond Cyclo-P, triple decker compound made First asymmetric hydrogenation catalyst discovered (a metallophosphine complex)... 

Some compounds of the types indicated in Table 6.14 are believed to have been synthesised. Most of these compounds contain some trimethylsilyl, ter-2,4,6 butylphenyl or other bulky stabilising groups. Some typical syntheses are (6.620-6.623) [7,8]. Bis methylene phosphoranes were discovered by Appel and co-workers in 1982 [9]. 

R. Appel, Bis(methylene) phosphoranes in M. Regitz and O.J. Scherer, Eds., Multiple Bonds and Low Coordination in P Chemistry, Thieme-Verlag, Stuttgart, 1990. 

The bis(methylene)phosphorans (Me3Si)2C=P(R)=C(SiMe3)2 (R = Mc2N, CeHn, Ph) were synthesized by Appel and coworkers in 1982. The compounds can be purified by vacuum distillation, but little about their reactions is known. A metallo-bis(methylene)phosphorane, CH2=P(LFe(CO)2=CH2, has also been synthesized. ... 

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