Binucleating behaviour of a proximally-diphosphinated calix[4]arene.

The long diphosphine 5,11-diphenylphosphanyl-25,26-dipropyloxy-27,28-bis(2-propenyloxy) calix[4]arene (cone) (5), in which the two phosphorus atoms are separated by a semi-rigid linking unit, was prepared in four steps starting from calix[4]arene. Reaction of 5 with AuCl(SEt(2)) or [RuCl(2)(p-cymene)](2) led to calixarenes bearing two metallated pendant arms, [5·(AuCl)(2)] and [5·{RuCl(2)(p-cymene)}(2)], respectively. In the presence of AgBF(4) or [Ni(C(5)H(5))(1,5-cyclooctadiene)]BF(4), diphosphine 5 displayed a marked tendency to form oligomeric material, but under high dilution conditions dimeric species were obtained selectively.

Calixarene-monophosphines as supramolecular chelators.

The calix[4]arenes 5-diphenylphosphino-17-R1-11,23-diR2-25,26,27,28-tetrapropoxycalix[4]arene (1, R1 = R2 = Br; 2, R1 = Br, R2 = H; 3, R1 = R2 = p-tolyl; 4, R1 = p-tolyl, R2 = H; 5, R1 = R2 = H; 20, R1 = p-tolyl, R2 = H), all bearing a diphenylphosphino group attached to the calixarene upper rim, have been synthesised starting from 5,11,17,23-tetrabromo-25,26,27,28-tetrapropoxycalix[4]arene. Reaction of 1-5 with [RuCl2(p-cymene)]2 leads quantitatively to monophosphine complexes, [RuCl2(p-cymene)L], in which the endo-oriented ruthenium atom unit sits inside the cone delineated by the four phenoxy rings. The particular orientation of the P-Ru vector appears to result from pi-pi interactions between the p-cymene ligand and two aromatic cavity walls.

Calix[4]arene-phosphine dimers: precursors of flexible metallo-capsules and self-compacting molecules.

The first diphosphines based on a double calixarene, namely 1,4 (or 1,3)-bis-(5-diphenylphosphino-25,26,27,28-tetrapropoxycalix[4]aren-17-yl)benzene (L(2), L(3)) were each prepared in four steps starting from 5,17-dibromo-25,26,27,28-tetrapropoxycalix[4]arene. Upon reaction of L(2) with [Au(tht)(thf)]BF(4), (tht = C(4)H(8)S) a rigid metallo-capsule was quantitatively formed, which adopts an oblique form owing to the distinct nature of the spacers linking the two calixarene half-spheres. In the solid state, the 1,4-substituted phenylene linker is turned towards the gold ion, suggesting the existence of weak bonding interactions between two aromatic CH protons of this ring and the metal centre (AuH =2.

Calix[4]arene daisychains.

Generic calix[4]arenes became readily accessible in the late 70s. With their potential eight anchoring points, their utility for the production of sophisticated, highly functionalised macrocyclic molecules was rapidly recognised. While most studies in calixarene chemistry have focused on monocalixarene derivatives, there is now an increasing interest in developing multicalixarene compounds, especially those made of several linearly-arranged calix[4]arene units, the first examples of which were reported in 1989.

Catalytic applications of keto-stabilised phosphorus ylides based on a macrocyclic scaffold: calixarenes with one or two pendant Ni(P,O)-subunits as ethylene oligomerisation and polymerisation catalysts.

Four calix[4]arenes containing either one or two ylidic -C(O)CH=PPh3 moieties anchored at p-phenolic carbon atoms were prepared starting from cone-25,27-dipropoxycalix[4]arene (1): 1,3-alternate-5,17-bis(2-triphenylphosphoranylideneacetyl)-25,26,27,28-tetrapropoxycalix[4]arene (12), 1,3-alternate-5-(2-triphenylphosphoranylideneacetyl)-25,26,27,28-tetrapropoxycalix[4]arene (13), cone-5-(2-triphenylphosphoranylideneacetyl)-25,27-dihydroxy-26,28-dipropoxycalix[4]arene (14), cone-5,17-bis(2-triphenylphosphoranylideneacetyl)-25,27-dihydroxy-26,28-dipropoxycalix[4]arene (15). All the ylides were shown to be suitable for the preparation of SHOP-type complexes, i.e.

Ethylene oligomerisation and polymerisation with nickel phosphanylenolates bearing electron-withdrawing substituents: Structure-reactivity relationships.

Three SHOP-type catalysts, in which the C=C(O) double bond was substituted by electron-withdrawing substituents, [Ni{Ph2PC(R1)=C(R2)O}Ph(PPh3)] (2: R1,R2 = -C(Me)=NN(Ph)-; 3: R1 = CO2Et, R2 = Ph; 4: R1 = CO2Et, R2 = CF3), were assessed as ethylene-oligomerisation and -polymerisation catalysts and compared to Keim's complex, [Ni{Ph2PCH=C(Ph)O}Ph(PPh3)] (1). A rationale for the influence of the double-bond substituents of the P,O-chelate unit on the catalytic properties is proposed, on the basis of X-ray diffraction studies, spectroscopic data and DFT-B3 LYP calculations. Whatever their relative electron-withdrawing strength, the R1 and R2 substituents induce an increase in activity with respect to catalyst 1.

Playing with podands based on cone-shaped cavities. How can a cavity influence the properties of an appended metal centre?

The potential of molecules that combine the properties of a conical cavity with those of a covalently-linked transition-metal centre is highlighted through the assessment of cyclodextrin- and calixarene-derived podands ("cavitand" ligands) in coordination chemistry and catalysis. Metallocavitands with coordination sites directed towards the interior of the generic cavity provide interesting systems for studying host-guest complexation processes, their enhanced strength of metal-ion binding allowing for regioselective catalysis in a confined environment, and stabilisation of coordination complexes of unusual forms. Where cavitands have exo-oriented podand arms, the intrinsic dynamics of the cavity can dramatically modify metal chelation behaviour and the catalytic properties of the complexes.

Bis-phosphites and bis-phosphinites based on distally-functionalised calix[4]arenes: coordination chemistry and use in rhodium-catalysed, low-pressure olefin hydroformylation.

Six calix[4]arenes each bearing two non-cyclic PR2 units attached at distal phenolic oxygen atoms, p-Bu t-calix[4]arene-25,27-(OPR2)2-26,28-(OR')2(R = OPh; R'= Prn, L1; R = OPh; R'= CH2CO2Et, L2; R= OPh; R'= CO2 cholesteryl, L3; R = Ph; R'= Prn, 4; R = Ph; R'= CH2CO2Et, L5; R = Ph; R'= CO2cholesteryl, L6) have been synthesized and their coordinative properties investigated. The diphosphites L1-L3, where the P centres are separated by 12 bonds, readily form chelate complexes provided the complexation reaction is achieved either by using a starting complex that possesses good leaving groups or by operating under high dilution in order to avoid oligomer formation. Thus, the cationic complexes [Rh(COD)L1]BF4 and [Rh(COD)L3]BF4 were both formed in high yield by reacting the appropriate diphosphite with either [Rh(COD)(THF)2]BF4 or [Rh(COD)2]BF4.

Diphosphines with expandable bite angles: highly active ethylene dimerisation catalysts based on upper rim, distally diphosphinated calix[4]arenes.

The binding properties of two large diphosphines, cone-5,17-dibromo-11,23-bis(diphenylphosphino)-25,26,27,28-tetrapropoxycalix[4]arene (1) and cone-5,17-bis(diphenylphosphino)-25,26,27,28-tetrapropoxycalix[4]arene (2) toward Ni(II) centres have been investigated. Whatever the starting complex, NiBr2 or [NiCp]BF4, quantitative formation of a chelate complex was observed, illustrating the preorganisation of the ligands. An X-ray structure determination was carried out for [NiCp1]BF4 which revealed that the nickel atom is positioned to one side of the calixarene axis, the PNiP plane being roughly parallel to the calixarene reference plane.