The mechanism and kinetics of the solvolysis of complexes of the type [(L-L)Pd(C(O)CH(3))(S)](+)[CF(3)SO(3)](-) (L-L = diphosphine ligand, S = solvent, CO, or donor atom in the ligand backbone) was studied by NMR and UV-vis spectroscopy with the use of the ligands a-j: SPANphos (a), dtbpf (b), Xantphos (c), dippf (d), DPEphos (e), dtbpx (f), dppf (g), dppp (h), calix-6-diphosphite (j). Acetyl palladium complexes containing trans-coordinating ligands that resist cis coordination (SPANphos, dtbpf) showed no methanolysis. Trans complexes that can undergo isomerization to the cis analogue (Xantphos, dippf, DPEphos) showed methanolyis of the acyl group at a moderate rate. The reaction of [trans-(DPEphos)Pd(C(O)CH(3))](+)[CF(3)SO(3)](-) (2e) with methanol shows a large negative entropy of activation. Cis complexes underwent competing decarbonylation and methanolysis with the exception of 2j, [cis-(calix-diphosphite)Pd(C(O)CH(3))(CD(3)OD)](+)[CF(3)SO(3)](-). The calix-6-diphosphite complex showed a large positive entropy of activation. It is concluded that ester elimination from acylpalladium complexes with alcohols requires cis geometry of the acyl group and coordinating alcohol. The reductive elimination of methyl acetate is described as a migratory elimination or a 1,2-shift of the alkoxy group from palladium to the acyl carbon atom. Cis complexes with bulky ligands such as dtbpx undergo an extremely fast methanolysis. An increasing steric bulk of the ligand favors the formation of methyl propanoate relative to the insertion of ethene leading to formation of oligomers or polymers in the catalytic reaction of ethene, carbon monoxide, and methanol.

The structures of neutral and ionic 4-cyanophenylpalladium() and methylpalladium() complexes containing bidentate phosphine ligands were investigated in solution and in the solid state. Diphosphine ligands with a xanthene and a ferrocene backbone were used. New bis(dialkylphosphino) substituted Xantphos ligands were synthesised. 1 H NMR and31 P NMR spectroscopy, conductivity measurements, UV-Vis spectroscopy, and X-ray crystallography were used to elucidate the structures of the complexes. Subtle changes of the phosphine ligands govern the coordination mode of the ligand. A variety of bidentate cis-, and trans-coordination and terdentate P-O-P, P-S-P and P-Fe-P coordination modes of the ligands were observed.

The synthesis of a new series of diphosphine ligands based on 2,7-di-tert-butyl-9,9-dimethylxanthene (1), p-tolyl ether (2), ferrocene (3), and benzene (4) backbones, containing one or two 2,8-dimethylphenoxaphosphine moieties, is reported. The ligands were employed in the rhodium-catalyzed hydroformylation of 1-octene. For all four ligand backbones, introduction of phenoxaphosphine moieties led to an increase in catalytic activity and a decrease in regioselectivity toward the linear aldehyde product. Xanthene-based ligands 1a-1c yielded highly active and regioselective hydroformylation catalysts; ligands containing p-tolyl ether and ferrocene backbones 2a-2c and 3a-3c provided less active and less regioselective catalysts. Catalysts containing benzene-derived ligands 4a and 4b showed a remarkable preference for the formation of the branched aldehyde product. The coordination behavior of ligands 1-4 under hydroformylation conditions was investigated using high-pressure NMR and IR spectroscopy, revealing the distinct steric and electronic properties of the diphenylphosphine and 2,8-dimethylphenoxaphosphine moieties in ligands 1-4. The phosphacyclic moieties proved to be less basic and less sterically demanding toward other ligands in metal complexes than the acyclic diphenylphosphine moieties. For ligands that contain rigid backbones, the lack of conformational freedom in these phosphacyclic moieties does lead to repulsive interactions between the substituents of the two phosphorus donor atoms, resulting in an increase in the bite angle of the ligand. The low catalytic activity of rhodium catalysts modified by benzene-based ligands 4a-4c was attributed to the quantitative formation of HRh(L) 2 under hydroformylation conditions.

Photolysis of CpMn(CO)3 in a hexane/water biphasic system has been shown to generate hydrogen peroxide and hydrogen in 40−50% yield. Photolysis of the title compound results in loss of a CO ligand followed by coordination of a water molecule. The initially formed CpMn(CO)2(H2O) intermediate was detected using time-resolved IR spectroscopy. The cyclopentadiene (CpH) monomer is generated as the major product, formed by the transfer of an H atom from the coordinated H2O solvent to the Cp ring. A simple mechanism for H2 generation is proposed on the basis of deuteration studies which demonstrate the production of D2 and CpD upon photolysis of CpMn(CO)3 in a hexane/D2O biphasic system.

In the past there has been a renewed interest in developing polymer-bound ligands and the corresponding catalysts. The primary advantages of polymer-supported ligands are the ease of purification during the synthesis and the ability to recover and reuse both the transition metal and the ligand.[1]Resin-bound chiral ligands have proven their efficiency in asymmetric catalysis.[2] The combinatorial synthesis and screening of chiral ligand libraries is an efficient method for finding enantioselective catalysts [3] and a number of successful approaches have been reported. [4,5] Although solid-phase organic synthesis (SPOS) has proven its efficiency in highspeed routes towards chemical libraries, surprisingly, examples in which SPOS is applied in the combinatorial synthesis and screening of phosphorus ligands are rare.[6] Recently, we reported the solid-phase parallel synthesis of a variety of phosphites and phosphoramidites.[7] Herein, we report an efficient route for the parallel synthesis of polymer-supported phosphorus-stereogenic aminophosphane-phosphite and aminophosphane-phosphinite bidentate ligands, as well as their application in rhodium-catalyzed asymmetric hydrogenation.P-stereogenic aminophosphane-phosphite and aminophosphane-phosphinite ligands (3, Scheme 1) have successfully been applied in asymmetric hydrogenation [8] and hydroformylation.[9] As a result of the modular structure of this class of ligands, there is an enormous potential for ligand finetuning (R 1 , R 2 , and R 3 ), which makes them ideal candidates for the parallel synthesis of (supported) ligand libraries.However, these types of ligands have all been developed in the traditional synthetic way requiring troublesome and laborious ligand optimization. A generally applicable combinatorial approach has not been developed yet because the synthetic methodology is still lacking. To assemble libraries of these chiral ligands the development of an efficient solidphase methodology is pivotal, not only to allow automated synthesis but also to circumvent work-up and purification problems, inherent to solution-phase synthesis.Following the general synthetic route developed by JugØ and co-workers (Scheme 1), [8] we developed the following route towards supported analogues.[10] The reaction of oxazaphospholidine borane 1 a (R 1 = phenyl) with the lithiated analogue 5 (Scheme 2) [11] of 4-bromo functionalized polystyrene 4 yielded a white resin that, based on the chemical shift of the relatively sharp resonance signal observed in its gel-phase 31 P NMR [12]

A family of monodentate polystyrene-supported phosphites, phosphoramidites and phosphanes has been prepared and evaluated as ligands in rhodium-catalysed asymmetric hydrogenation and palladium-catalysed asymmetric allylic alkylation. The supported ligands yielded active and enantioselective catalysts, which in selected cases match the performance of the nonsupported counterparts. As expected, the performance of the supported ligands in the rhodium-catalysed hydrogenation depends on the nature of the ligand, the type of polymeric support, as well as on the substrate. Ad-

Various routes for the synthesis of polymer-bound phosphites and phosphoramidites have been investigated. In the presence of a suitable activator the supported phosphoramidites react cleanly with alcohols to give the corresponding monodentate phosphite ligands in solution. We have applied this novel solid-phase route in the parallel synthesis of several monodentate chiral and achiral phosphite ligands.

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