13652-21-6Relevant academic research and scientific papers
A new Type of Transition-Metal Dimer Based on a Hexaphosphine Ligand System: Co2(CO)4(eHTP)(2+) (eHTP = (Et2PCH2CH2)2PCH2P(CH2CH2PEt2)2)
Askham, Fredric R.,Stanley, George G.,Marques, Edward C.
, p. 7423 - 7431 (1985)
The synthesis and characterization of a new hexa-tert-phosphine ligand system, (Et2PCH2CH2)2PCH2P(CH2CH2PEt2)2, 1, is described.This ligand has the ability to both tris-chelate and bridge two transition metals, either in a closed-mode, M-M bonding geometry, or in an open-mode configuration in which the two metal atoms are 6-7 Angstroem apart.Reaction of 1 with 2 equiv of CoCl2 initially produces, in high yiels, the paramagnetic, binuclear, red-brown Co(II) compound, Co2Cl4(eHTP), 4, where eHTP = 1.An Extended X-ray Absorption Fine Structure (EXAFS) spectrum of 4 shows Co-P and Co-Cl bond distances in the 2.2-2.4 Angstroem region and no Co-Co contact distance less than 4.0 Angstroem, indicating that 4 is in an open-mode geometry.On standing, 4 dissociates two chloride ligands to form the green, paramagnetic Co2Cl2(eHTP)(2+) complex, 5, which precipitates out of the reaction mixture, either as the chloride or, if an extra equivalent of CoCl2 is used, the CoCl4(2-) salt.The EXAFS spectrum on the CoCl4(2-) salt of 5 is very similar to that of 4, indicating that 5 is also in an open-mode geometry.Reaction of 4 or 5 (alone or mixed) with H2/CO (33percent CO) and an extra equivalent of CoCl2 at 50 bar and 80 deg C forms, in high yields, the yellow-green, diamagnetic Co(I) binuclear carbonyl/eHTP complex, , 6a, which can be metathesized with aqueous NaPF6 to give the yellow PF6(1-) salt, 6b. 6 has been charactirized by 1H and 31P NMR, EXAFS, mass spectroscopy, IR, and a crystal structure.Crystals of 6b belong to the monoclinic space group C2/c, with unit cell parameters a = 26.464 (4) Angstroem, b = 12.562 (2) Angstroem, c = 14.380 (3) Angstroem, β = 99.04 (1) deg, V = 4721 (3) Angstroem3, and Z = 4.The structure was refined to give R = 0.070 and Rw = 0.106.The molucule lies on a 2-fold axis, passing through the bridging methylene group of the eHTP ligand.The complex has the central bis(phosphino)methane portion of the eHTP ligand adopting a unique inverted coordination geometry to give an open-mode complex with the two cobalt atoms separated by 6.697 (1) Angstroem.The cobalt atoms have a distorted trigonal-bipyramidal geometry with one carbonyl ligand and two terminal phosphorus atoms of the eHTP ligand in the equatorial plane.
Tridentate phosphine ligands bearing aza-crown ether lariats
Pap, Levente G.,Arulsamy, Navamoney,Hulley, Elliott B.
, p. 385 - 392 (2018)
Crown ethers are useful macrocycles that act as size-selective binding sites for alkali metals. These frameworks have been incorporated into a number of macromolecular assemblies that use simple cations as reporters and/or activity triggers. Incorporating crown ethers into secondary coordination sphere ligand frameworks for transition metal chemistry will lead to new potential methods for controlling bond formation steps, and routes that couple traditional ligand frameworks with these moieties are highly desirable. Herein we report the syntheses of a family of tridentate phosphine complexes bearing tethered aza-crown ethers (lariats) designed to modularize the variation of aza-crown size, lariat length, and distal phosphine substituents, followed by the synthesis and solid-state structures of Mo(III) complexes bearing cations in the pendent crown ethers.
