110174-49-7Relevant academic research and scientific papers
Synthesis and characterization of a new series of η6-arene compounds of molybdenum and tungsten: M(OC6H3Ph-η6-C6H 5)(X)(L)2 (M = Mo, W; X = H, Cl) compounds containing chelated 2,6-diphenylphenoxide ligands
Kerschner, Judith L.,Torres, Edna M.,Fanwick, Phillip E.,Rothwell, Ian P.,Huffman, John C.
, p. 1424 - 1431 (2008/10/08)
Reaction of the group 6 metal tetrahydrides MH4(PMePh2)4 (M = Mo, W) with 2,6-diphenylphenol (HOAr-2,6-Ph2; excess) in a melt at temperatures above 150°C leads to the formation of a deep red mixture from which the 18-electron compounds M(OC6H3Ph-η6-C6H 5)(H)(PMePh2)2 (M = Mo (1), W (2)) can be isolated. Spectroscopic data on deep red 1 and 2 indicate the presence of a 2,6-diphenylphenoxide ligand chelated to the metal via an η6-interaction through one of the side-chain aryl rings. A solid-state structural study of both 1 and 2 showed them to be isomorphous and confirmed the presence of the η6-arene ring. Chelation of this ring through the aryloxide oxygen atom causes no noticeable asymmetry in the π-interaction with the metal centers. The overall geometry about the metal is best described as a four-legged piano stool with the phosphine ligands mutually trans. The resulting virtual plane of symmetry in the molecules is found to be maintained in solution, with 1H, 13C, and 31P NMR spectra indicating equivalent phosphine ligands being present along with equivalent ortho and meta hydrogens on the η6-bound aryl ring. These monohydrides are found to be extremely stable to thermolysis, with no indication for the activation of the ortho-CH bonds of the substituent aryl rings of the OAr-2,6-Ph2 ligand. Formation of related compounds containing η6-bound 2,6-diphenylphenoxide by reduction of high-valent derivatives of this ligand proved successful. Hence reduction of W(OAr-2,6-Ph2)Cl5 (3) with sodium amalgam (4Na/W) in the presence of phosphine ligands produced the 18-electron monochlorides W(OC6H3Ph-η6-C6H5) (Cl)L2 (L = PMe2Ph, 4; L2 = Ph2PCH2CH2PPh2, 5). Compounds 4 and 5 have spectroscopic properties similar to the monohydrides. Structural studies of 4 and 5 also show the coordination environment about the tungsten atom to be similar to that seen in 2. In the case of 5 the trans arrangement of the phosphorus atoms of the dppe ligand is achieved without unusual distortions. Attempts to prepare chelated 2,6-diphenylphenoxide compounds of molybdenum by heating HOAr-2,6-Ph2 with Mo(CO)6 in octane led only to the η6-arene compound Mo(HOC6H3Ph-η6-C6H 6)(CO)3 (6) in high yield. Both spectroscopic as well as structural studies showed the phenolic group to be protonated. Attempts to obtain chelation by inducing oxidative addition of the OH bond to the Mo metal center failed. Crystal data for MoC44H40P2O (1) at -145°C: a = 17.310 (7) A?, b = 10.149 (3) A?, c = 21.090 (5) A?, β= 108.89 (2)°, Z = 4, dcalcd = 1.407 g cm-3 in space group P21/c. For WC44H40P2O (2) at -155°C: a = 17.358 (4) A?, b = 10.20 (1) A?, c = 21.127 (5) A?, β = 108.85 (1)°, Z = 4, dcalcd = 1.558 g cm-3. For WC34H35ClP2O (4) at 22°C: a = 14.942 (2) A?, b = 12.6796 (8) A?, c = 16.233 (1) A?, β = 98.104 (8)°, Z = 4, dcalcd = 1.616 g cm-3 in space group P21/c. For WC44H37ClP2O (5) at 20°C: a = 9.172 (1) A?, b = 19.765 (6) A?, c = 10.293 (3) A?, β = 110.22 (2)°, Z = 2, dcalcd = 1.637 g cm-3 in space group P21. For MoO4C21H14 (6) at 20°C: a = 20.304 (1) A?, b = 12.188 (2) A?, c = 14.464 (2) A?, Z = 8, dcalcd = 1.582 g cm-3 in space group Pbcn.
