The hydrolysis–polycondensation of palladium (Pd) and platinum (Pt) complexes of phosphines [p-(OiPr)3SiC6H4]2PC6H5 and [p-(OiPr)3SiC6H4]3P gives rise to xerogels in which the metal complexes are included within a silica matrix with retention of the arrangement around the metal centre. However, the trans-Pd as well as the trans-Pt complexes incorporated within the xerogels slowly isomerize into the more stable cis complexes. Direct reaction of (CH3CN)2PdCl2 with xerogels prepared from both phosphines leads to the incorporation of the Pd salt, the corresponding complexes always adopting a cis arrangement of the ligands. Treatment with nBu3P of all the materials containing metal centres leads to the complete removal of the metal except for the materials obtained by hydrolysis of the metal–[p-(OiPr)3SiC6H4]3P complexes.

Dibenzo-18-crown-6 ether derivatives bearing two (1, 2) or four (3) hydrolysable Si(OR)3 groups have been synthesised. Their hydrolysis and polycondensation gave rise to new hybrid organic–inorganic materials incorporating dibenzo-18-crown-6 ether moieties covalently linked to silica by two or four Si–C bonds. The complexation of alkali metal cations (Na+ and/or K+) by these materials was investigated. A survey of the uptake of cations showed that four types of chelating sites exist within these materials, the ratio of which depends on the nature of the precursor (flexibility of the spacers between the benzene rings and the silicon centres and number of hydrolysable Si(OR)3 groups) and also on the degree of condensation σ of the polysiloxane network. Furthermore, the complexation of K+ by the precursors 1, 2 and 3 and of Na+ by 1 were performed quantitatively. During the sol–gel polymerisation of these complexes it was shown that about 95% of the alkali cations were retained within the xerogel. This study proves that the two routes of incorporation of salts within these hybrid materials are not equivalent.

The hydrolysis-polycondensation by the sol-gel process of the aromatic diphosphines (X3SiC6H4)2PC6H4P(C6H4SiX3)2, which are rigid molecules bearing four hydrolysable SiX3 groups (X = OiPr, H), leads to new organic-inorganic hybrid materials, characterized by solid state 13C, 29Si, and 31P NMR spectroscopies. The accessibility of the phosphorus centres incorporated into the xerogel obtained from the diphosphine with X = OiPr has been studied. All the phosphorus atoms reacted quantitatively with H2O2, S8, and CH3I but only 20% with the more bulky reagent W(CO)5·THF. This result is explained by the rigidity of the inorganic network resulting from the high number of hydrolysable Si-OiPr groups in the precursor.Key words : Diphosphines, sol-gel process, xerogels, solid 31P NMR.

Starting from R'R2P (R' = 8-dimethylamino-1-naphthyl) containing a donor dimethylamino group, the new phosphonium salts [R'R2P(CH2Ph)]Br-+(-) [R = Me (9) or Ph (10)] and [R'R2P(p-CH2C6H4CH2)PR2R'](2+)[2Br](2-) [R = Ph (12)] have been prepared. An interaction between the N and P atoms is evident from the X-ray crystal structure of 10 the N-P distance being less than the sum of the van der Waals radii of the 2 atoms. The geometry of 10 is that of a monocapped tetrahedron whereas the X-ray crystal structure determination shows essentially regular tetrahedral geometry for the analogous compound without the donor amino group, [(1-Np)Ph2P(CH2Ph)]Br-+(-) (11). Treatment of 1,5-bis(dimethylamino) -2,6-dilithionaphthalene with chlorodiphenylphosphane gave 1,5-bis(dimethylamino)-2,6-bis(diphenylphosphanyl)-naphthalene (8) which in the presence of methyl iodide afforded the diphosphonium salt [1,5-bis(dimethylamino)-2,6-bis(diphenylmethylphosphonium)naphthalene](2+)[2I](2-) (13). Similarly, treatment of 8 with 1 equivalent of benzyl bromide gave the monophosphonium salt [1,5-bis(dimethylamino)-2-diphenylbenzylphosphonium-6-diphenylphosphanyl-naphthalene](+) [Br](-) (14) whereas in the presence of 2 equivalents of the same reagent [1,5-bis(dimethylamino)-2,6-bis(diphenylbenzylphosphonium)naphthalene] (2+)[2 Br](2-) (15) was obtained. The ionomer poly([(1,5-bis{dimethylamino}- 2,6-bis{diphenylphosphonium}naphthalene)-(P,P-p-xylylene)](2+)[2 Br](2-)) (16), soluble in liquid SO2, was prepared by treatment of 8 with alpha,alpha'-dibromo-p-xylene.

The complexation of alkali metal cations (Na+ and/or K+) by organic-inorganic hybrid materials incorporating dibenzo-18-crown-6 ether moieties covalently linked to silica by two Si-C bonds is explained in terms of deformations of the crown ether moiety during the sol-gel process.

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[4+2]-Coordinate phosphorus compounds, [bis(8-(dimethylamino)-1-naphthyl)]phenylphosphane, [bis(8-(dimethylamino)-1-naphthyl)]phenylphosphane sulfide, [bis(8-(dimethylamino)-1-naphthyl)]phenylphosphonium bromide, [bis(8-(dimethylamino)-1-naphthyl)]methylphosphane, and [bis(8-(dimethylamino)-1-naphthyl)]phosphane oxide, with two identical bidentate (8-(dimethylamino)-1-naphthyl) ligands have asymmetrical geometries in solution and undergo intramolecular nondissociative ligand exchange as shown by dynamic (1)H NMR studies. The DeltaG() values for this process were found to lie in the range 56.2-61.7 kJ mol(-)(1). The (1)H NMR study for bis[(8-(dimethylamino)-1-naphthyl)]phenylphosphane sulfide has revealed that two hexacoordinate isomers coexist in solution in a solvent dependent ratio. Their interconversion in solution is consistent with an intramolecular 1,2-shift of adjacent ligands.

The reaction of p-bromo (triisopropyloxysilyl)benzene 2 with magnesium led to stable THF solutions of the corresponding Grignard reagent. The reaction of this latter with PCl(3) or PhPCl(2) allowed the preparation of phosphines 4 and 5 respectively. LiAlH(4), reduction of 4 afforded phosphine 6. Compounds 4 and 6 have been transformed into phosphorus derivatives including BH(3), W(CO)(5), platinum and palladium complexes, all of them bearing three hydrolysable groups. Hydrolysis and condensation of these phosphorus derivatives in the presence of an acid catalyst result in the formation of new hybrid organic-inorganic silica gels incorporating phosphorus centres. Solid state (13)C, (29)Si, (31)P NMR spectroscopies were used to evaluate the integrity of the organic moiety and to determine the degrees of hydrolysis and condensation in the network materials. It was shown that during the sol-gel process there is no alteration around the phosphorus centre. The xerogels are amorphous microporous materials with specific surface areas lying between less than 10 m(2) g(-1) and 800 m(2) g(-1) depending on the experimental conditions. In contrast with these results, complete cleavage of the Si-C bonds was observed during the hydrolysis and polycondensation of the tris(triisopropyloxysilylmethyl)phosphine 7 and of tris(trihydrosilylmethyl)phosphine 8.

Solution NMR studies of silyl cations [ArSiMe2]+X− (X = I, CF3SO3) incorporating the terdentate aryl diamine ligand Ar - C6H3− 2,6-(CH2NMe2)2 have been carried out in a protic solvent (methanol-d4) and in an aprotic solvent (CD2Cl2). This study has shown that the structure of these silyl cations is highly dependent on the solvent. In CD2Cl2, the silyl cation is five-coordinated owing to the coordination of one NMe2 group and of the anion to the silicon centre which gives rise to a dissymmetric structure. On the other hand, in CD3OD there is no coordination of the anion, but the silyl cation is also probably five-coordinated due to the coordination of the solvent to the silicon atom which is supported by the X-ray analysis of the compound 9. With the weakly nucleophilic anion BPh4− in CD2Cl2, in addition to the silyl cation previously described, another five-coordinated silyl cation resulting from the coordination of both NMe2 groups to the Si centre was postulated.

New hexacoordinate phosphonium salts Ar(2)RZP(+) X-[Ar = (8-dimethylamino)-1-naphthyl] with two N-->P intramolecular coordinations are described. NMR studies of these salts and the X-ray structure of one of them, 5 (R = Ph, Z = H, X = Br) show that they have a dissymmetric structure with the two Me2N groups coordinated at the phosphorus centre. Salts 4 (R = Ph or Me, Z = CH2CO2Et) react slowly with PhCHO under Wittig conditions probably because of the steric hindrance around the phosphorus atom. This is confirmed by the higher reactivity of the less hindered pentacoordinate phosphonium salts ArR2P+CH2CO2Et X- 11 (R = Ph or Me) which are also much more reactive than Ph3P+CH2CO2Et Br-. This study points out the increase of reactivity of these salts due to the N-->P interaction.

The reaction of ArLi 1 (Ar = [C6H3(CH2NMe2)2-2,6]) with Ph2PCl affords the phosphane 2 which, on treatment with HCl, gives rise to the monoprotonated ammonium salt 3, even in the presence of an excess of HCl. 2 reacts with MeI to give exclusively the phosphonium salt 4. Reaction of 1 with PhPCl2 gives the stabilized phosphenium ion [ArPPh]+Cl− 6. This ion is reduced by LiAlH4 in ArPHPh 9, which undergoes hydride abstraction on treatment with trityl cation, giving the same ionic phosphorus species. This unusual reaction is an example of increased reactivity of a PH bond resulting from hypercoordination at the phosphorus atom.

ArPH2 (Ar=[C6H3(CH2NMe2)2-2,6]) 3 undergoes hydride abstraction on treatment with trityl cation to give the stabilized phosphenium ion [ArPH]+BF4−, 4a. The same cation was prepared by reaction of 3 with BrCCl3 (4b) and also by lithiation of 3 followed by treatment with I2 (4c). ArLi reacts with PX3 (X = Cl or Br) to give the stabilized phosphenium ion [ArPX]+X− which affords 3 by LiAlH4 reduction. In contrast, DIBAL-H reduction of [ArPX]+X− gives [ArPH]+X−. This last reaction constitutes a transformation of a stabilized and functionalized phosphenium ion into a different ion. Confirmation of the structure of these salts was given by single-crystal X-ray diffraction analysis of [ArPH]+PF6− 4e.

An extension of coordination by intramolecular N → P donor-aceptor interaction in (8-dimethylamino-1-naphthyl)diphenylphosphane 1 has been shown by X-ray structure determination. In addition, a very easy intramolecular isomerisation process around the phosphorus atom at room temperature was revealed by dynamic NMR studies. Isomerisation also occurs in the corresponding oxide 2, sulfide 3, and phosphonium salts 4 and 5, but with slightly higher activation energies.

The high basicity of {2,6-bis-[(dimethylamino) methyl]phenyl} bis (1,2-benzenediolato)silicate (1) was demonstrated by its quantitative protonation in methanol to give the zwitterion 2. It was found that 1 is much more basic (pKa in CH2Cl2 = 16.7) than the “proton sponge” 1,8-bis(dimethylamino)naphthalene (3) and also much more basic than {2,6-bis-[(dimethylamino) methyl]phenyl} bis (1,2-benzenediolato)phosphorane (4). The stability of the zwitterion 2, the geometry of which corresponds to a more perfect octahedron than 1, can explain the high basicity of 1. Dynamic NMR studies of 2 in solution show that at low temperature the hydrogen-bonding interaction with one oxygen atom observed in the solid state is maintained. On raising the temperature, firstly the hydrogen bond breaks, then dynamic coordination occurs, in which the NMe2 groups displace each other in conjunction with transprotonation.

Hexacoordination of the neutral phosphorus compounds 4–6 is evidenced by their high field 31P NMR chemical shifts and is further substantiated by the crystal structure of 5 and 6.5 contains the potentially bis-chelating ligand Ar = (C6H3(CH2NMe2)2-2,6) and 6 the same ligand with a protonated amino group. In both cases the compounds exhibit slightly distorted octahedral geometry. In compound 5, only one NMe2 group is coordinated to the phosphorus atom with an N → P bond of 2.063 Å. In compound 6, the NMe2 group is coordinated to the phosphorus atom with an N → P bond of 2.007 Å while the dimethylammonium substituent is pointing away from the phosphorus atom forming a hydrogen bridge with two oxygen atoms. The fluxional behavior of these three novel six-coordinate phosphorus compounds was studied by dynamic 1H NMR spectroscopy.

In this paper, we describe two routes to prepare silyl cations with at least one Si-H bond by using the bis-chelating ligand C6H3(CH(2)NMe(2))(2)-2,6. The first is the reaction between a pentacoordinate dihydrosilane ArRSiH(2) [Ar = (C6H3(CH(2)NMe(2))(2)-2,6] and an electrophile. The second is the reaction of the lithium derivative ArLi with a dichlorohydrosilane RSiHCl(2). These cations are 5-coordinated owing to intramolecular chelation by the two NMe(2) groups. By using the same bis-chelating ligand, the formation of silyl cations with Si-C bonds has also been investigated. We show that in an aprotic solvent with non-nucleophilic counteranions [(3,5-(CF3)(2)C6H3]B-4(-), BPh(4)(-)] there is also his chelation of the two amino groups to the silicon atom giving 5-coordinated silyl cations while in the presence of nucleophilic anions (Cl-, Br-, I-, CF3SO3-) there is no his chelation of the two NMe(2) groups but rather a fluxional coordination of these groups occurring at silicon.

The X-ray structure analysis of bis(8-dimethylamino-l-naphthyl)phenylphosphane (3) and of the corresponding sulphide 4 has revealed hexacoordination at phosphorus in both cases, the N … P separations being less than the sum of the van der Waal radii. Furthermore, in both cases the overall geometry corresponds to a distorted bicapped tetrahedron. The optimum geometry calculated for 4 via the Hyperchem program developed by Autodesk (MM + method) suggests that the structure of the molecule is a function not only of steric requirements but also of electronic effects.

We confirm that compounds 2 bearing a SiH bond are siliconium ions. In contrast we show that the non-functional cationic compounds 4–7 exist as silylammonium ions or siliconium ions depending on the counteranion and on the solvent.