With phosphanes

Alkylation of the anion 2 with iodomethane or other haloalkanes provides alkyldicarbonyl(t/5-cyclopentadienyl)iron complexes such as 53,0 (see also Houben-Weyl, Vol. 13/9a, p 209). Migratory insertion of carbon monoxide occurs on treatment with phosphanes or phosphites9 -11 (see also Houben-Weyl, Vol. d3/9a, p257) to provide chiral iron-acyl complexes such as 6. This is the most commonly used preparation of racemic chiral iron-acyl complexes. 

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... 

Phosphite ligands (Fig. 9) are known to be better 7r-acceptors than phos-phane ligands. The stronger electron-withdrawing ligand increases the reaction rate because CO from the metal center is dissociated faster than with phosphane ligands. For different mono-phosphites, the selectivity to the... 

The rate-determining first step is the reaction of the isocyanate with phosphane oxide, resulting in the formation of isocyanate and CO2. Once the isocyanate is formed, it reacts with additional isocyanate to give carbodi-imide and regenerate the catalyst. A more detailed investigation of the reaction mechanism (Scheme 25) followed years later (69ACSA2697 72ACSA1777). 

In broad terms the coordination chemistries of technetium and rhenium are similar, and isomorph-ous compounds are frequently found. One important exception is the behavior with phosphanes. Since Tc is a stronger oxidant than Re, the reaction with phosphanes very often leads to reduction to Tc° and lower oxidation states. This is particularly the case with compounds derived from the... 

Thiiranes that are obtained from the reaction of diazo dipoles with C=S bonds can be transformed into alkenes by desulfurization. This reaction sometimes occurs spontaneously, but more often is achieved by treatment with phosphanes (225). This important methodology represents an alternative for the W ittig reaction and has high merit for the preparation of stericaUy hindered (226-229) and uncommonly functionalized alkenes (214,216,217,230,231). Some examples are given in... 

Several other dicarbonyltris(phosphane)iron complexes are mentioned as coproducts in the reaction of tricarbonyl( 1,2,3,6,->/-cyclooctenediyl)iron with phosphanes, but only the P(OC2H5)3 derivative could be isolated (60%).12... 

The reaction of GeCl2 with phosphane 123 furnished thermally unstable diphosphene 124, which at room temperature underwent cyclization to the bicyclic diphosphane 125 with liberation of Pr PCl (Scheme 42) <2001MGM609, 2004JOM(689)1331>. 

Complexes of type A with phosphane are determined by the tr-donor bond of the phosphorus atom. On the contrary, the (d-d)n back donation of the phosphorus is poor, due to much lower x-acceptor ability, and the balance of electrons cannot take place within the phosphorus metal bond. With respect to 31P NMR the phosphorus molecule is deshielded, exhibiting a low-field shift for the i 1-coordinated P atom of about 30-60 ppm compared to the uncoordinated phosphane phosphorus. 

The reaction of HFA with phosphanes has been reported by Bruker et al. (43) and reinvestigated by Roschenthaler (227). 

Of interest are the electron-rich, late transition metal catalysts with phosphane ligands rather than the electron-deficient, early transition metal Ziegler-Natta catalysts. 

When perfluoro(2-methylpent-2-ene) reacts with phosphanes, carbanion 5 is formed. It is known that internal alkenes isomerize into the terminal alkenes in the presence of basic reagents, so that 5 reacts with this isomeric form and the end product of the reaction is per-fluoro(3-ethyl-2.5-dimcthylocta-2.4-dieiie) (6). 

The addition of phosphanes to fluoroalkenes follows a free-radical mechanism. For example, tetrafluoroethene (1) yields preferentially the linear addition product 2 in moderate yield when reacted with phosphane at 150 C (see also Table 6). ... 

Novel water-soluble calix[4]arenes with phosphane-containing groups were synthesized by Shimizu et al. The beneficial effect of water-soluble phospha-... 

Besides polymeric material, a mixture of three ene reaction products is obtained (18% combined yield) in the thermal reaction, which proceeds at 20°C within several minutes. Similar results are found when zeolites with a large pore diameter (5-13 A) are used as catalysts. After irreversible addition of the cyclopropene to the zeolite, only polymeric material is obtained. Zeolites with 3- or 4-A pores give rise to a product spectrum similar to that obtained with phosphane-free palladium(O) catalyst systems, i.e. 90-97% of the tricyclic dimers are formed from 1- or 3-methylcyclopropene at temperatures between — 35 and 35 C. The palladium(II) chloride catalyzed reaction almost quantitatively yields a 2 1 mixture of the isomeric 1,2- and l,4-dimethyl-evo-tricyclo[3.1.0.0 ]hexane (lA and IB) from 1-methylcyclopropene. The reaction is strongly exothermic and therefore must be carried out in dilute solutions with effective... 

The principal synthetic application of cyclopropylidenetriphenylphosphoranes 4 is the conversion with carbonyl compounds (aldehydes and ketones) into alkylidenecyclopropanes 5. As cyclopropyl halides do not react with phosphanes to form cyclopropylphosphonium halides vide supra), the generation of these precursors 3 is generally performed by condensation of 1,3-dibromopropanes 1 with triphenylphosphane and subsequent 1,3-dehydrobromination of the resulting salt 2 with one equivalent of base. A second equivalent of base generates the... 

Co-cyclotrimerization of cyclopropenes with alkynes is achieved with phosphane-free cobalt catalysts, e.g. (t/ -cycloocta-l, 5-diene- -cyclooctenyl)cobalt(I), to give tricyclo[5.1.0.0 ]oct-2-ene systems 22 as the predominant products. Norcaradienes and cycloheptatrienes were observed as side products. 

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