Synthesis, characterization, and coordination chemistry of two new tartaric acid-derived bis(phosphite) ligands

Comparative Study of Novel Phosphordiamidite and Phosphite Ligands Used in Alkene Hydroformylation; Synthesis, Characterization, Metalation, and Catalytic Evaluation

“…The palladium complexes of L1 and L3 , ( 4 and 6 ), have singlet 31 P{ 1 H} NMR resonances that are 30–40 ppm upfield of those of the ligands. These are consistent with the typical Δ δ values for other phosphite‐substituted cis ‐[PdCl 2 (L) n ] complexes, which are between 30 and 34 ppm upfield of those of the parent ligands even though these complexes are structurally diverse (monodentate vs. bidentate) (rigid vs. flexible linkers in the backbone) …”

Generally Applicable NMR Titration Methods for the Determination of Equilibrium Constants for Coordination Complexes: Syntheses and Characterizations of Metallacrown Ethers with α,ω-Bis(phosphite)-polyether Ligands and Determination of Equilibrium Binding Constants to Li+

“…To achieve nonstoichiometric binding conditions, the observed association binding constant, K obs , was lowered by using a mixture of tetrahydrofuran- d 8 and dichloromethane- d 2 . Tetrahydrofuran was chosen because it is very similar to the diethyl ether that is coordinated to the Li + in the LiB(C 6 F 5 ) 4 ·2Et 2 O salt and because it is commonly used as a solvent in the styrene hydroformylation reactions catalyzed by Rh metallacrown ethers. − To determine a concentration of tetrahydrofuran- d 8 in dichloromethane- d 2 at which both free alkali metal cations and free 2 are present, and at which some coordination of the Li + to 2 is detectable, a tetrahydrofuran solvent back-titration was carried out and plotted in Figure . Aliquots of a solution of tetrahydrofuran- d 8 containing a 1:1 ratio of 2 and LiB(C 6 F 5 ) 4 ·2Et 2 O were added to a dichloromethane- d 2 solution that also contained a 1:1 ratio of 2 and LiB(C 6 F 5 ) 4 ·2Et 2 O at the same concentration at 301 K. The 31 P{ 1 H} NMR chemical shifts were converted to observed, normalized signal changes using the form (σ o – σ I )/(σ F – σ I ), where σ o is the observed chemical shift, σ I is the initial chemical shift of 2 in this case, and σ F is the final chemical shift of bound 2 ·Li + , and were plotted versus the concentration of tetrahydrofuran- d 8 present, as shown in Figure .…”

“…Hard/soft bimetallic complexes, such as those formed by the coordination of an alkali metal cation to a metallacrown ether, are of interest as catalysts for organic reactions involving carbon monoxide because the interaction of both metals with carbon monoxide may give rise to activities and/or selectivities that are different from those of the monometallic, transition-metal catalysts. We have recently reported that Rh(I) metallacrown ethers with α,ω-bis(phosphite)-polyether or α,ω-bis(phosphite)-polyether/amide ligands are catalysts for the hydroformylation of styrene, and the production of the branched isomer (regioselectivity) could be increased by the addition of an alkali metal salt. − However, it was not clear if this effect was due to binding of the alkali metal cation by the metallacrown ether because it was also observed with bis(phosphite) ligands that did not contain a polyether group and required a large excess of the alkali metal salt in tetrahydrofuran.…”