Tertiary phosphine-functionalized ligands

The low affinity of the alkali metals for neutral P-donor ligands has hampered efforts to synthesize complexes in which there is a genuine R3P-M interaction (see Section I). However, this poor affinity may be overcome by incorporating a remote phosphine functionality into a potentially chelating anionic ligand, such as a phosphine-substituted alkoxide, amide, or aryl, and several alkali metal complexes of such ligands have been isolated. 

Selected Structural and NMR Data for Crystallographically Characterized Alkali Metal Complexes of Tertiary Phosphine-Functionalized Ligands 

The ligand is chiral at both phosphorus and methine carbon centers and the compound crystallizes as pairs of RRSS (with reference to the 

Addition of LiAlMe4 to 64 yields the adduct [ LiN(SiMe2CH2PPr )2 LiAlMe4]2, which is dimeric in the solid state. Two of the lithium atoms are bound by the ligand in a P2N bis-chelate mode, the other 

The structure of the unusual diphospholide complex [ (Me3Si)3Si Li(p,-176 i76-2,4,5-But3-C3P2)( i76-toluene)] has been reported, although synthetic details were not described (174). The two lithium atoms sit either side of the diphospholide anion, each bound in an rf-fashion. The coordination sphere of one lithium is completed by a cr-bonded Si(SiMe3)3 ligand, while the other lithium is bound in an rf-fashion to a molecule of toluene. 

CH2PM62 substituents allowing Li-P contacts without disruption of the bond angles of the core. Multinuclear NMR studies indicate that the dimeric structure is preserved in solution. At 193 K the structure is static the Li and P spectra consist of a triplet and a quartet (c PLi = 44 Hz), respectively, indicating coordination of each lithium by two phosphorus atoms. However, at room temperature the Li and P spectra consist of a quintet and a septet, respectively (J u = 21 Hz), indicating that the dimer is fluxional, with each Li coupling to all four phosphorus nuclei and vice versa. A of 50 kJ moL was estimated for this process from the coalescence temperature. 

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The coordination chemistry of tertiary phosphine-functionalized calix[4]arenes have been described.279 Treatment of a bis(diphenylphosphino) or bis(dimethylphosphino) derivative of calix[4]arene with [PtCl2(COD)] leads to the formation of the corresponding dichloroplatinum(II) complex. The related diplatinum(II) species has also been reported with the tetrafunctionalized calix[4]arene.280 The mononuclear derivative is susceptible to oligomerization if the two free phosphine ligands are not oxidized or complexed to another metal center such as gold(I).279 The platinum(II) coordination chemistry of a mono-281 and diphosphite282 derived calix[ ]arene (n = 4 and 6, respectively) has also been described. 

Ph3P)4Pd and certain Pd(II) complexes in the presence of an excess of a tertiary phosphine also function as active catalysts (128). This indicates that palladium species may have potential provided they are protected from destructive reduction by the choice of suitable ligands. A complex species [(Ph3P)2Pd]jf gradually forms in the PhjP—Pd metal mixture ( 28). 

Bis-ylides (Scheme 31) may function as four-electron donors and become geminally diaurated. The donor capacity of ylides is generally higher than that of most other ligands, and even powerful donors like tertiary phosphines can thus be readily replaced by non-stabilized ylides. Ylides may therefore be used as auxiliary ligands which are retained, while other components of the coordination sphere are subject to substitution. 

Functionalized tertiary aryl phosphines play an important role in transition metal coordination chemistry. These compounds have been used as ligands in synthesis, catalysis, mechanistic studies, and in the study of coordination compounds as structural models. In this contribution the syntheses of two new types of these ligands, tertiary aryl phosphines functionalized by an amide group, are detailed. The published coordination chemistry of these compounds includes the study of intramolecular N—H oxidative addition, the synthesis of chelates stabilized amido complexes, and the preparation of complexes with both ftve- and six-membered chelate rings. ... 

Schiff base condensation reactions have also been widely used in the preparation of new imine-functionalized tertiary phosphines (64) (68).122-129 The most frequently used experimental procedure involves the condensation of a carbonyl compound (often 2-Ph2PCeH4CHO)176 and the appropriate amine in ethanol, benzene, or THF under refluxing conditions. To ensure complete reaction, a Dean-Stark trap or the addition of molecular sieves is often necessary, to remove water formed during the reaction. Evaporation of the solvent and recrystallization yield the desired ligand in good to excellent yields. This approach can be used to prepare bis-phosphines, e.g., (66)-(68).127- 29 The iminophosphine (69) was prepared by a series of coupling reactions at a palladium template, and was liberated from the metal by treatment with aqueous cyanide.130... 

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