Phosphanes, nitrogenated

Keywords Group 13 metals (aluminum, gallium, indium, thalhum), Ambidentate ligands. Phosphorus-nitrogen bidentate ligands, Pyridyl phosphanes, Aminoiminophosphoranes, Lewis acid catalysis... 

Compound 13a can been obtained via two different routes firstly in the reaction of 11 with dimethyl aluminum chloride where LiCl is eliminated and secondly by the reaction of di(pyridyl) phosphane 12 (Py2PH) with trimethyl aluminum where methane is formed, (Scheme 5). The X-ray structure determination of [Me2AlPy2P] 13a, (Fig. 3) elucidates the aluminum atom to be coordinated by the two nitrogen atoms of the pyridyl rings in addition to the two remaining methyl groups leaving the aluminum four... 

In an excellent review by Roesky et al. in 1994 [70a] a vast number of examples for coordination complexes of cyclic phosphazanes and phosphazenes and other related systems have already been compiled. In the following section, an attempt is made to cover the latest features of group 13 systems along with some earlier examples with phosphorus-nitrogen based systems other than pyridyl phosphanes. 

The phosphinimide phosphanes 42 [75b], which are similar to the acyclic diphosphazanes comprising of one nitrogen and phosphorus atom, when treated with AlMea, (Scheme 19), were found to coordinate to the P(III) center to yield the alane adducts 43 which were characterized by the P-NMR spectroscopy and structure elucidation of 43a. 

Phosphinous amides bearing protons at the nitrogen atom, that here we will call NH phosphinous amides, such as 6, may be involved in prototropic equilibria with their PH phosphazene forms 7 [18,68-70] (Scheme 10). This kind of prototropic equilibria, paralleling that between phosphinous acids R2P-OH and phosphane oxides R2P(0)H [4], have been evidenced in some particular... 

The first spirophosphorane with an azaphosphetidine ring 63 was prepared from the intramolecular cyclization and dehydration of phosphane oxides with DEAD/PPh3 <1996AGE1096, 1996PS489>. Dissolution of 63 in [r/8]-toluene led to some isomerization to the pseudorotamer 64, where the electronegative nitrogen occupies the equatorial position (Scheme 32). Such rotamers were previously unknown for the analogous oxaphosphetanes. 

The phosphanes useful in this process are built from acyl derivatives of compounds such as those shown in Figure 17.22. During the Staudinger ligation process, once the azide reactant forms the aza-ylide with the phosphine, electrophilic attraction induces the nitrogen to attack the electron deficient carbonyl, which in turn causes release of the phosphonium group and forms the amide bond (Figure 17.23). 

On the other hand, an electronically stabilized heavy ketone by the coordination of the nitrogen atom shows extremely low reactivity. It does not react with phosphanes, phosphates, ketones, epoxides, Mel, HC1, etc., although it undergoes methanolysis and hydrolysis (Scheme 21).168... 

For the reaction of phosphane oxide with isocyanate, the rate-determining step is the formation of the oxazaphosphetane 45 via P—O—bond formation of the intermediate betaine (44), since the stable and energetically favorable P=0 double bond is broken here. Subsequent rapid decomposition of the oxazaphosphetane 45 into iminophosphorane and carbon dioxide occurs. Within the actual aza-Wittig step, the intermediate betaine (46) is generated in a rate-determining step by nucleophilic attack of the iminophosphorane nitrogen on the carbonyl C. By P —O-bond formation, betaine (46) is then converted into an oxazaphosphetane (47), which decomposes... 

Phosphanes with quaternized aminoalkyl and aminoaryl groups or with phosphonium groups can also provide water solubility. Before the nitrogen atom can be alkylated, the phosphorus center has to be protected by oxida-... 

In addition to nitrogen bases, the potential of chiral phosphanes as catalysts has also been assessed. Early work on the use of P-chiral phosphines in intramolecular... 

This mechanism, involving sequential hydronation of N2 initially at the nitrogen atom remote from the metal(s), followed by cleavage of the N—N bond, then hydronation of the resulting nitride, is, in essence, the same mechanism that has been developed on electron-rich, low-oxidation-state Mo phosphane complexes (Section III). The only real difference is that in this case the N2 is bound to four Fe sites in a cluster. 

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