Multinuclear NMR Spectroscopic and X‐ray Crystallographic Studies of Electronic and Steric Effects of Phosphonous Acid Ligands and Their Chlorophosphite Ligand Precursors in Tungsten Pentacarb­onyl Complexes

Abstract

Although phosphonous acid ligands have recently become of interest for use in transition metal complex catalysts for organic reactions such as alkene hydroformylations, the factors that affect the steric and electronic properties of these ligands have not been studied in detail. To gain insight into the electronic and steric properties of phosphonous acid ligands, we have prepared tungsten(0) pentacarbonyl complexes with chlorophosphite ligands derived from either 2,2′‐biphenol or (±)‐1,1′‐bi‐2‐naphthol and have then hydrolyzed the coordinated ligands to generate tungsten(0) pentacarbonyl complexes with the corresponding phosphonous acid ligands. NMR measurements of the W–P coupling constants demonstrate that changing the biaryl groups from biphenyl to binaphthyl does not affect the electron‐donor ability of the ligand, whereas changing the third substituent from chloro to oxo has a significant effect. Estimation of cone angles of the ligands from X‐ray crystallographic data have shown that neither changing the biaryl group nor changing the third substituent have a significant effect on their cone angles. Further, these studies have identified important intra‐ and intermolecular interactions that favor certain ligand conformations. The data could be useful for the development of catalytic structure–activity relationships that could be used in the rational design of catalysts.

Synthesis, characterization and the thermal isomerization mechanism of a series of trans-tetracarbonyl-bis(phosphinite)molybdenum(0) complexes and an evaluation of their potential to form heterobimetallic compounds

“…6 (selected distances are listed in Table 3). These interactions are similar to other intramolecular metal (sp) carbonyl (p)/p interactions recently reported by our group [14].…”

Anionic phosph(in)ito (“phosphoryl”) ligands: Non-classical “actor” phosphane-type ligands in coordination chemistry

“…The presence of an acidic "hydroxy" substituent in −position to the phosphorus atom plays a critical role in some catalytic chemical transformations. [84] and O−anionic  1 -P−phosphite tungsten 28 [85] complexes in interaction with triethylammonium. …”

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

“…It was of interest to determine if | 1 J P–Se | and | 1 J P–W | correlate well with one another because tungsten analogs of P‐donor ligands are easier to obtain than are selenium analogs, and in some cases either selenium or tungsten values are not available in the literature to be used for comparative purposes. The values of | 1 J P–Se | and | 1 J P–W | that were available in the literature for a variety of ligands were plotted against one another (Figure ) , . A linear least‐squares analysis demonstrates a good correlation between the values ( R 2 = 0.961), even though the steric and electronic parameters are changing simultaneously.…”

“…These torsion angles are within the typical ranges observed for [Mo(CO) (6– n ) {P(X)(2,2′‐O 2 C 12 H 8 )} n ] complexes (O–P–O–C = |46.5 ± 7.1|°, P–O–C–C = |75.1 ± 3.9|°, ). Because the biphenyl groups of the [1,3,2]‐dioxaphosphepin rings racemize in solution, their complexes often crystallize in centrosymmetric space groups with both enantiomers in the same crystal as do 6 ( P 2 1 / c ) and 7 ( P 2 1 / n ) , , , . However, enantiomers can also segregate upon crystallization into a noncentrosymmetric space groups as does 3 , …”