| Abstract
| - Ortho-linked polyaryloxides are developed as new multidentate ligands for transition-metal chemistry. The ligand syntheses are flexible and allow facile modification of the basic ligand design. A structural investigation of these ligands on Ti(IV) reveals a series of dimeric and trimeric complexes that are characterized by 5- and 6-coordinate metal centers with a range of chelate coordination and bridging modes.
- Ortho-linked polyphenols, quaterphenol L(OH)4, and moderately hindered terphenol PhL(OH)3 are developed asnew multidentate polyaryloxide ligands for transition-metal chemistry. The polyphenols are synthesized usingortho-metalation and metal-catalyzed cross-coupling methodologies; the synthetic routes allow for facile electronicand steric modification of the basic ligand design. The Ti(IV) coordination chemistry of these ligands reveals adiverse collection of bridged structures: dimeric [Ti(μ-PhLO3)(OiPr)]2 (P21/n, a = 12.2699(5) Å, b = 11.7957(5)Å, c = 21.238(1) Å, β = 94.551(1)°, Z = 2, T = 170(2) K), dimeric [Ti2(μ-PhLO3)2(μ-Cl)(Cl)(THF)] (P, a =11.212(1) Å, b = 14.165(1) Å, c = 22.447(2) Å, α = 90.440(4)°, β = 93.345(4)°, γ = 111.164(4)°, Z = 2, T =170(2) K), and trimeric [Ti3(μ,μ‘-LO4)(μ-OiPr)2(OiPr)6] (P21/n, a = 11.1022(5) Å, b = 18.7015(9) Å, c =24.409(1) Å, β = 95.369(2)°, Z = 4, T = 170(2) K). The reaction of TiCl3(THF)3 with [PhLO3]3- results inoxidation of Ti(III) to Ti(IV) and formation of the oxo dimer [Ti(PhLO3)(THF)]2(μ-O) (P, a = 10.8649(6) Å,b = 12.1882(7) Å, c = 14.3349(9) Å, α = 65.602(3)°, β = 84.390(3)°, γ = 86.582(3)°, Z = 1, T = 200(2) K);the oxo group presumably originates from the THF solvent. The titanium centers in these environments are either5- or 6-coordinate, with distorted square pyramidal/trigonal bipyramidal and distorted octahedral geometries,respectively; the polyphenoxide chelate ligands are capable of bridging multiple oxophilic titanium sites.
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