Synthesis of rhodium–carbonyl complexes bearing a novel P,N-chelating ligand of Schiff-base type

Abstract

Schiff-base type N,P-chelating ligands, phosphorus analogues of imino-anilido ligands, were designed and synthesized as a new type of ligands toward transition metals, and the rhodium-carbonyl complexes bearing the novel imino-phosphido and phosphaalkenyl-anilido ligands were synthesized as stable crystalline compounds. Their structures were definitively revealed by X-ray crystallographic analysis, showing the unique electronic features of the ligands. In addition, the effective trans-influence of the phosphorus atom was suggested on the basis of the structural parameters and spectroscopic features of the isolated complexes.

Rhodium-Catalyzed Isomerization of a Bis(secondary phosphine) to an Unsymmetrical Diphosphine via P–C Cleavage and P–P and C–H Bond Formation

“…In agreement with this idea, in NMR spectra of 5 in toluene- d 8 the phosphido 31 P­{ 1 H} NMR signal shifted upfield on cooling to −80 °C until it overlapped the PHIs peak, but only one set of signals was observed throughout. As previously observed in Rh, Pt, and other phosphido complexes, , the change in phosphorus coordination number from four to three on deprotonation of 2 – 4 to yield 5 – 7 resulted in decreased J PP and J Rh–P couplings, for example, from 287 (trans J PP ) and 105 Hz in 2 to 113 and 50 Hz in 5 (Table ). As with the cationic precursors 2 – 4 , rotation about the P–C­(Is) bonds was slow on the NMR time scale in 5 – 7 .…”

Efficient Synthesis of Titanium Complexes Bearing Tridentate [N–,N,O–] Anilido-Imine Ligands and Their Catalytic Properties for Ethylene Polymerization

“…The free ligands L a H 2 −L f H 2 were synthesized in moderate to high yields by refluxing a 2-(arylamino)benzaldehyde derivative with a 2-amino-4-tert-butyl-6-alkylphenol compound in methanol in the presence of a few drops of formic acid, as illustrated in Scheme 1. The 2-(arylamino)benzaldehyde derivatives were synthesized following a published procedure 13 by coupling 1,3dioxolane-protected 2-bromobenzaldehyde with the corresponding 2,6-dialkylaniline in toluene using Pd(OAc) 2 as the catalyst. The free ligands L a H 2 −L f H 2 were characterized by 1 H and 13 C NMR spectroscopy.…”

“…The 2-(arylamino)benzaldehyde derivatives were synthesized following a published procedure 13 by coupling 1,3dioxolane-protected 2-bromobenzaldehyde with the corresponding 2,6-dialkylaniline in toluene using Pd(OAc) 2 as the catalyst. The free ligands L a H 2 −L f H 2 were characterized by 1 H and 13 C NMR spectroscopy. All these compounds show the characteristic resonances for HCN (8.75−8.76 ppm) and Ar−OH (6.47−6.54 ppm) in similar patterns.…”

“…On the basis of the above investigation, complexes 3a−3f were synthesized in high yields by carrying out the reactions of TiCl 4 with the corresponding free ligands L a H 2 −L f H 2 in toluene at 110 °C and then heating the crude products at 140 °C for a couple of hours. All complexes 3a−3f were characterized with 1 H and 13 C NMR spectroscopy, as well as elemental analyses. Structures of complexes 3b, 3d, and 3e were determined by single-crystal X-ray crystallography.…”

“…Gel permeation chromatography (GPC) analysis on the resultant polymers exhibits a relatively narrow polydispersity index (PDI) of 2.45−3.75, indicating the single-site nature of these catalyst systems. The polymers were also characterized by 13 C NMR, which indicates that the resultant polymers are linear with a characteristic resonance at 30.2 ppm. The melting points of the obtained polyethylenes range from 138 to 142 °C, which is typical for linear polyethylene.…”