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Bond Angle Effects on the Migratory Insertion of Ethylene and Carbon Monoxide into Palladium(II)-Methyl Bonds in Complexes Bearing Bidentate Phosphine Ligands

Bond Angle Effects on the Migratory Insertion of Ethylene and Carbon Monoxide into Palladium(II)-Methyl Bonds in Complexes Bearing Bidentate Phosphine Ligands. Ledford, John; Shultz, C. Scott; Gates, Derek P.; White, Peter S.; DeSimone, Joseph M.; Brookhart, Maurice (Department of Chemistry, University of North Carolina, Chapel Hill, NC 27599-3290, USA). Organometallics, 20(25), 5266-5276 (English) 2001 American Chemical Society. CODEN: ORGND7. ISSN: 0276-7333. DOCUMENT TYPE: Journal CA Section: 29 (Organometallic and Organometalloidal Compounds) Section cross-reference(s): 22, 75 Labile (P-P)Pd(CH3)(OEt2)+BAr'4- complexes (2) have been prepd. via protonation of (P-P)PdMe2 (1), where P-P = cis-1,2-bis(diphenylphosphino)ethylene (a, dppee), 1,2-bis(diphenylphosphino)benzene (b, dpbz), 1,2-bis(diphenylphosphino)ethane (c, dppe), 1,2-bis(dimethylphosphino)ethane (d, dmpe), 1,3-bis(diphenylphosphino)propane (e, dppp), 1,3-bis(diisopropylphosphino)propane (f, dippp), 1,4-bis(diphenylphosphino)butane (g, dppb) and Ar' = 3,5-(CF3)2C6H3. Unstable complex 2d (P-P = dmpe) was generated in situ. X-ray structures are reported for 1e and 2e-g. Treatment of 2a-g with CO in CH2Cl2 at -90° yields the (P-P)Pd(CH3)(CO)+ complexes 3a-g. Barriers to migratory insertion in 3a-g were detd. with the ordering to be: 3f (dippp) u 3g (dppb) < 3e (dppp) ? 3a (dppee) u 3b (dpbz) u 3c (dppe) < 3d (dmpe). Exposure of 2a-g to ethylene at -80° yields the ethylene complexes (P-P)Pd(CH3)(C2H4)+ (5a-g). Barriers to migratory insertion in these complexes were detd. by NMR spectroscopy to be: 5b (dpbz) u 5e (dppp) u 5f (dippp) u 5g (dppb) < 5a (dppee) u 5c (dppe) < 5d (dmpe). Complexes (P-P)Pd(CH2CH3)(C2H4)+ (6a-e,g) produced from 5a-e,g under C2H4 are catalyst resting states for the dimerization of C2H4 to butenes. In the case of 5f (P-P = dippp), the catalyst resting state produced is the b-agostic Et complex (dippp)Pd(CH2CH2-m-H)+ (8f), which has been isolated. This complex exhibits two dynamic processes studied by VT-NMR:interchange of Ca and Cb (DGG = 10.3(2) kcal/mol) and rotation of the agostic Me group (DGG ca. 6.4 kcal/mol). The b-agostic Pr complex 7f has been generated and identified as the Pr isomer (dippp)Pd(CH2CH2-m-HCH3)+. Keywords bond angle effect migratory insertion ethylene carbon monoxide palladium methyl bidentate phosphine complex prepn migratory insertion crystal mol structure methyl palladium bidentate phosphine arylborate complex kinetics migratory insertion ethylene carbon monoxide palladium dimethyl complex Index Entries Bond agostic; bond angle effects on migratory insertion of ethylene and carbon monoxide into palladium-Me bonds in complexes bearing bidentate phosphine ligands Free energy of activation Insertion reaction kinetics Potential barrier bond angle effects on migratory insertion of ethylene and carbon monoxide into palladium-Me bonds in complexes bearing bidentate phosphine ligands Bond carbon-palladium; bond angle effects on migratory insertion of ethylene and carbon monoxide into palladium-Me bonds in complexes bearing bidentate phosphine ligands Bond angle effect; bond angle effects on migratory insertion of ethylene and carbon monoxide into palladium-Me bonds in complexes bearing bidentate phosphine ligands Insertion reaction intramol., migration; bond angle effects on migratory insertion of ethylene and carbon monoxide into palladium-Me bonds in complexes bearing bidentate phosphine ligands Crystal structure Molecular structure of methylpalladium complexes with bidentate phosphine ligands Dimerization catalysts prepn. of methylpalladium bidentate phosphine complexes as dimerization catalysts for alkenes 260994-21-6 389798-51-0 389798-53-2 389798-55-4 389798-57-6 389798-59-8 389798-61-2 74-85-1, reactions 51915-19-6 139362-04-2 15630-15-6 63455-39-0 210767-94-5 288155-73-7 389798-18-9 389798-19-0 389798-21-4 389798-23-6 389798-25-8 389798-27-0 389798-29-2 389798-31-6 389798-33-8 389798-35-0 389798-37-2 389798-39-4 bond angle effects on migratory insertion of ethylene and carbon monoxide into palladium-Me bonds in complexes bearing bidentate phosphine ligands 113530-46-4 113530-47-5 210767-70-7 260993-77-9 crystal structure; bond angle effects on migratory insertion of ethylene and carbon monoxide into palladium-Me bonds in complexes bearing bidentate phosphine ligands 288155-74-8 288155-77-1 389798-41-8 389798-43-0 389798-44-1 389798-45-2 389798-47-4 389798-49-6 389798-63-4 389798-65-6 389798-67-8 389798-69-0 389798-71-4 389798-73-6 389798-75-8 389798-77-0 prepn. of 113822-11-0 reaction with bidentate phosphines 983-80-2 1663-45-2 6737-42-4 7688-25-7 13991-08-7 23936-60-9 91159-11-4 reaction with dimethyl(tetramethylethylenediamine)palladium complex

Optimization of the microscale determination of phosphates by direct potentiometric titration with silver ions and its application to the determination of phosphorus in organic compounds

Optimization of the microscale determination of phosphates by direct potentiometric titration with silver ions and its application to the determination of phosphorus in organic compounds.Some chemicals with cas registry numbers like 7688-25-7 and 603-35-0 are also used. Pietrogrande, Agostino; Zancato, Mirella; Bontempelli, Gino (Dep. Pharm. Sci., Univ. Padua, Padua 35131, Italy). Analyst (London), 112(2), 129-31 (English) 1987. CODEN: ANALAO. ISSN: 0003-2654. DOCUMENT TYPE: Journal CA Section: 80 (Organic Analytical Chemistry) Section cross-reference(s): 79 The microscale detn. of orthophosphate ions by argentometric titrn. with potentiometric detection of the end point using a combined massive Ag electrode was investigated. The best results were obtained when this titrn. was carried out in H2O/iso-PrOH (50%) buffered at pH 8.80. Under such conditions the titrn. error arising from the partial copptn. of Ag oxide near the equivalence point is minimized and the results obtained have a satisfactory accuracy (errors within ±0.30%) and good reproducibility. The concn. range in which reasonable accuracy and precision are attained and the most suitable titrn. rate to be adopted when an automatic titrimetric device is used were also considered. This optimized titrn. method was successfully applied to the detn. of P in organophosphorus compds. after mineralization in a suitably modified Schoeniger flask. .