Conformationally Restrained Octahedral Metallacrown Ethers with 1,2-(Ph₂P(CH₂CH₂O)₂)₂C₆H₄ Ligands. X-ray Crystal Structure of cis-Mo(CO)₄{1,2-(Ph₂P(CH₂CH₂O)₂)₂C₆H₄-P,P‘}

Abstract

A new R,ω-bis(phosphine)-polyether ligand, 1,2-(Ph 2 P(CH 2 CH 2 O) 2 ) 2 C 6 H 4 , has been synthesized and used to prepare a number of conformationally restrained metallacrown ethers. The reaction of 1,2-(Ph 2 P(CH 2 CH 2 O) 2 ) 2 C 6 H 4 and Mo(CO) 4 (nbd) gives a good yield of cis-Mo-(CO) 4 {1,2-(Ph 2 P(CH 2 CH 2 O) 2 ) 2 C 6 H 4 -P,P′}. This complex has been isomerized to trans-Mo-(CO) 4 {1,2-(Ph 2 P(CH 2 CH 2 O) 2 ) 2 C 6 H 4 -P,P′} using both UV light and HgCl 2 catalysis. The reaction of 1,2-(Ph 2 P(CH 2 CH 2 O) 2 ) 2 C 6 H 4 with fac-RuCl 2 (CO) 3 (THF) initially yields a mixture of monomeric and oligomeric cis,cis,trans-[RuCl 2 (CO) 2 {1,2-(Ph 2 P(CH 2 CH 2 O) 2 ) 2 C 6 H 4 -P,P′}] n metallacrown ethers. Surprisingly, the oligomeric metallacrown ethers slowly convert into the monomeric metallacrown ether at ambient temperature in a chloroform-d solution. This does not occur with the conformationally mobile [cis,cis,trans-RuCl 2 (CO) 2 {Ph 2 P(CH 2 CH 2 O) 4 -CH 2 CH 2 PPh 2 -P,P′}] n metallacrown ethers. The X-ray crystal structure of cis-Mo(CO) 4 {1,2-(Ph 2 P(CH 2 CH 2 O) 2 ) 2 C 6 H 4 -P,P′} has also been determined. The four ether oxygens lie in a plane, and the average cross-ring oxygen-oxygen distance is slightly larger than those in metallacrown ethers containing Ph 2 P(CH 2 CH 2 O) 4 CH 2 CH 2 PPh 2 ligands.

Synthesis, characterization and coordination chemistry of a new phosphite–ether ligand: The effects of alkali metal salts and the ligand/Rh molar ratio on the catalytic activity and regioselectivity of a Rh(I) complex of this ligand in the hydroformylation of styrene

“…Consistent with the NMR data, 6 has a cis octahedral coordination geometry similar to that seen in other cis-Mo(CO) 4 (P-donor ligand) 2 complexes [45,46]. The octahedron is significantly distorted as indicated by the deviation of the phosphorus-molybdenumphosphorus bond angle (96.21(11)°) from the ideal angle of 90°.…”

“…2 and 3, respectively. These structures are of interest because they allow the effect of the coordination environment of the metal center on the ligand to be examined and because they are closely related to the previously reported structures of sterically unhindered and symmetrical metallacrown ethers [44][45][46][47][48].…”

Metallacrown ethers with a symmetric bis(phosphite) ligand derived from 1,2-bis-(2-hydroxyethoxy)benzene: Synthesis, characterization and hydroformylation of styrene

“…2 and 3 respectively. These structures are of interest because they allow the effect the variation in transition metal center on the conformation of metallacrown ether ring to be examined and are closely related to the previously reported structures of sterically hindered and symmetrical metallacrown ethers [40]. The solid state conformations of 2 and 4 also provide insight into the catalytic studies because they allow the metallacrown ether ring conformations to be evaluated for their potential abilities to bind alkali metal cations.…”

“…It is interesting that cis-Mo (CO)4 ({Ph 2 P(CH 2 CH 2 O) 2 } 2 -o-C 6 H 4 )[40], which also has an o-phenylene group in the metallacrown ether ring fails to exhibit cation binding although the related metallacrown ether in which the ophenylene is replaced by an ethylene, cis-Mo(CO)4 ({Ph 2 P (CH 2 CH 2 O) 4 CH 2 CH 2 PPh 2 ) [43] does bind Li þ and Na þ cations under the same conditions. An metallacrown ether ring in 2 has a chair conformation.…”

Metallathiacrown Ethers: Synthesis and Characterization of Transition-Metal Complexes Containing α,ω-Bis(phosphite)-Polythioether Ligands and an Evaluation of Their Soft Metal Binding Capabilities

“…These complexes are often formed by the bidentate chelation of α,ω-bis­(phosphorus-donor)-polyether ligands to transition metals. Like the crown ethers, the metallacrown ethers prefer to bind hard metal cations, but the presence of a transition-metal center modifies their selectivity and also provides additional spectroscopic probes, such as the 31 P­{ 1 H} NMR chemical shift, that allow the binding to be evaluated both qualitatively and quantitatively. − Hard metal cation binding also has been reported to affect the activities and selectivities of metallacrown ether catalysts in alkene hydrogenation and hydroformylation reactions. − …”