Air-sensitive phosphines

BH3 protects air-sensitive phosphines (deprotection is carried out using an amine)... 

All these 6-electron compounds are Lewis acid, thus they react with Lewis bases such as NR 3. The carbanions lead to borates such as BPli4 that are sometimes used to precipitate organometallic cations. BH3 is currently used to protect air-sensitive phosphines (see section 3) and to crystallize them. The complexes formed are air-stable, and the free phosphine can easily be regenerated by reaction with an amine giving, with BH3, a more robust complex. 

It is worth noting from a practical point of view that the air sensitive phosphine P(t-Bu)2Me can be replaced by the commercially available, air-and moisture- stable salt [HP(/-Bu)2Me]Bp4 without decrease in yield. The drawback of this methodology was that it is limited to the use of vinylstannanes and that arylstannanes were ineffective partners. The solution came a few months later with the discovery that electron-rich alkyldiaminophosphane PCy(pyrrolidinyl)2 was a superior ligand compared to P(/-Bu)2Me (36 + 37 38). ... 

Air-sensitive phosphine ligands are rarely used for CDC reactions under strong oxidative conditions. However, the Li group developed a... 

Although the synthetic approaches taken by these two groups appear more or less straightforward, there are two difficulties associated with the synthesis of these phosphorus maeroeyeles which make these preparations all the more substantial. The first of these problems is the air sensitivity of phosphines, especially primary and secondary... 

It would be more convenient if 12 or a similar catalyst could be made in situ from precursors which are more air-tolerant than 6 and require fewer steps to make. (Phosphine 11 is air-sensitive but no more so than PPh3, which can be weighed and transferred in open air.) Complex 1 seemed a suitable candidate, for it is air-stable and can be made in one step from ruthenium trichloride, CpH, and PPh3,(21) and ligand substitutions are facile, particularly inprotic solvents. 

Cp2Zr(CO)(PR3) (R = Me, F), were isolated as oily, air-sensitive solids. The competing photodegradation of Cp2Zr(CO)2 (2) to oligomeric zirco-nocene prevented the formation of these monocarbonyl-phosphine complexes in higher yields (51). 

Under microwave heating, the Heck olefinations were achieved in 30-60 min, as opposed to 10-40 h by conventional heating. The recyclable heterogeneous LDH-Pd(0) catalytic system circumvents the need to use expensive and air-sensitive basic phosphines as ligands in the palladium-catalyzed coupling of chloroarenes. This novel Mg-Al layered double-hydroxide (LDH) support in the catalytic system stabilizes the nanopalladium particles and also supplies adequate electron density to the anchored palladium(O) species and facilitates the oxidative addition of the deactivated electron-rich chloroarenes. 

Caution. Triethylphosphine and tetrakis(triethylphosphine)platinum(0) are extremely air-sensitive. The phosphine is malodorous and toxic. Therefore all... 

Tetrakis(triethylphosphine)platinum(0) is extremely air sensitive and readily soluble in saturated aliphatic hydrocarbons. The complex can be stored under dry nitrogen in a freezer (-35°) for several months. The complex readily loses one of the coordinated phosphine molecules to give Pt(PEt3)36 (dissociation constant (K ) in heptane is 3.0 X 10" ). The H NMR spectrum measured in benzene-d6 shows two multiplets at 5 1.56 (CH2) and 1.07 ppm (CH3). Tetrakis-(triethylphosphine)platinum(O) is a strong nucleophile and reacts readily with chlorobenzene and benzonitrile to give a-phenyl complexes PtX(Ph)(PEt3)2 (X = Cl, CN).7 Oxidative addition of EtOH affords [PtH(PEt3)3] +. 

The reaction of aliphatic 1,5-Grignard compounds of 1,5-dibromopentane with dichlorophenylphosphine constituted the first synthesis of a phosphorinane derivative, 1-phenylphosphorinane (equation (3)). It is an air sensitive colourless oil with the characteristic strong smell of a phosphine. Addition of HgCl2 gives a solid product, m.p. 127 °C, With... 

By bubbling 02 into a solution of Ni(CNR)4 or Ni(CNR)2 at temperatures below —20 °C, green compounds having the formula [Ni(CNR)202] are formed (R = Cy, Bu ).26 It is reported that these compounds are very air-sensitive and thermally unstable they may explode spontaneously when dried. The reactivity of the [Ni(CNR)202] complexes has however been studied (equations 9-14).27 In general, the oxygen atoms are transferred from the isocyanide complex to the different reactants with the formation of different oxo compounds such as oxoanions, peroxides and phosphine oxides. Reactions (9)-(14) (referred to as atom transfer reactions) all occur at low temperatures. 

When [Pt(COD)2] (10) is treated with 4 equiv of tertiary phosphine in a hexane solution under nitrogen, [Pt(PR3)4] is formed. These platinum(O) complexes are yellow, air-sensitive, low-melting, crystalline solids with solubility properties that are very similar to the parent phosphines. When dissolved in solution these complexes reversibly dissociate (see Equation 4). Thus the P-31 NMR spectra in benzene... 

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