An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

The synthesis of the calix[4]arene-based P,N-ligand 3 (5,11,17,23-tetra-tert-butyl-25-[(2-quinolylmethyl)oxy]-26,27,28-(mu3-phosphorustrioxy)calix[4]arene), in which the nitrogen atom-containing moiety has been introduced at the lower rim of the cavity prior to P-functionalisation, is described and its coordination properties investigated. In the crystal structure, the calix[4]-cavity adopts a cone conformation with an exo orientation of the phosphorus lone pair enabling P-N chelation. 1H, 13C, 31P and 1H{15N} HMQC NMR spectra indicated that, in complexes [PdCl(CH3)(3)] (4) and [Rh(CO)Cl(3)] (5), ligand 3 coordinates in a chelating fashion, while in cis-[PtC12(3)2] (6) and [Rh(acac)(CO)(3)] (7) it behaves as a monodentate ligand, coordinating via the phosphorus atom only. X-Ray crystal structure determinations were performed for [PdCl(CH3)(3)] (4) and cis-[PtCl2(3)2] (6). The cationic Pd complex [Pd(CH3)(CH3CN)(3)][PF5] (8) was found to be active in a CO/ethylene copolymerisation reaction. Good selectivities were observed for the Pd-catalysed allylic alkylation of cinnamyl acetate with in situ prepared catalysts. [Rh(acac)(CO)2] modified with ligand 3 catalyses the hydroformylation of 1-octene with low selectivities towards linear aldehydes. High-pressure NMR experiments on the hydrido carbonyl rhodium(3) were inconclusive, different species were formed.

Chiral calixarene-based diphosphite ligands 3a-d have been obtained via lower-rim functionalisation of the p-tert-butylcalix[4]arene core. High enantiomeric excesses (up to 94 %) and good activities were obtained in the rhodium-catalyzed asymmetric hydrogenation of prochiral olefins with TADDOL-containing diphosphites 3c,d. This is the first example of chiral calix[4]arene-modified ligands that induce high enantioselectivity in metal-catalysed asymmetric reactions.

A study of the insertion reaction of ethylene into the Pd-C bond on complexes of general formula [Pd(CH3)(N-N)(2)][OTf] and [Pd(CH3)(phen)(L)][OTf] led to the development of a facile procedure for the synthesis of new, stable, Pd-ethyl derivatives. The rate of this insertion reaction is affected by the nature of the nitrogen-donor ligand, N-N or L.

Two series of methylpalladium(II) compounds with mono and bidentate nitrogen-donor ligands, namely [Pd(N-N)2(CH3)][X] (N-N=phen (1a), dm-phen (1b) (dm-phen=4,7-dimethyl-1,10-phenanthroline), tm-phen 1c (tm-phen=3,4,7,8-tetramethyl-1,10-phenanthroline); X=OTf, PF6−) and [Pd(N-N)(L)(CH3)][OTf] (N-N=phen and L=py (1ad) (py=pyridine), N-N=phen and L=2-Ph-py (1ae) (2-Ph-py=2-phenyl-pyridine), N-N=phen and L=BzQ (1af) (BzQ=7,8-benzoquinoline), N-N=tm-phen and L=BzQ (1cf)), have been synthesised and fully characterised both in solid state and in solution. The crystal structures of [Pd(phen)2(CH3)][PF6] and [Pd(phen)(2-Ph-py)(CH3)][OTf] show a square planar coordination geometry for palladium with the monodentate ligand (one phen molecule plays this role in 1a) bound to the metal with its plane almost perpendicular to the coordination plane. In both structures the PdN bond length trans to the methyl is remarkably affected by its trans influence. The behaviour in solution is characterised for the first series of compounds by a dynamic process which makes the two N-N ligands equivalent, as corroborated by the 15N NMR analysis: only one averaged signal is shown for all of the four nitrogen atoms. No fluxional process is present for the compounds of the second series, and three main crosspeaks are shown in the 15N–1H HMQC spectra. In particular, the signal of the 15N trans to the methyl group has a typical chemical shift, which differs from those of two 15N trans to each other. Both series of complexes are reacted with carbon monoxide and the reaction products are studied by 1H NMR spectroscopy and, when possible, by isolating the acyl derivatives. The products of this reaction are affected by the nature of the second molecule of N-ligand.

The efficiency of a superficially simple preparation procedure for palladium-diphosphane catalysts has been examined. Preparation of Pd(dppe)X-2 in situ by mixing equimolar amounts of Pd(OAc)(2) and 1,2-bis(diphenylphosphanyl)ethane (dppe) in methanol in the first step unexpectedly affords the bischelate [Pd(dppe)(2)](OAc)(2) as the (main) kinetic product. Subsequently, the slow reaction of [Pd(dppe)(2)](OAc)(2) and unreacted Pd(OAc)(2) forms the thermodynamically favored monochelate [Pd(dppe)(OAc)(2)] (following first-order kinetics). Conversion of the bischelate into the monochelate stops after addition of strong acid (HX) in the second step, thus affording a mixture of active Pd(dppe)X-2-virtually inactive-[Pd(dppe)(2)]X-2-and unstable - PdX2-species. This procedure was also evaluated for some other diphosphane ligands and methods are given to overcome the encountered problem.

Isolation of a series of sulfonated diphosphines via a new highly efficient method is described. The work-up procedure involves the precipitation of the sulfonated ligand prior to neutralization, and subsequent removal of the sulfuric acid by filtration and washing. Great advantages of this procedure are its simplicity and easiness to scale-up while co-production of large amounts of sulfate salts is avoided.