Ortho-linked polyaryloxide ligands and their titanium complexes

Ortho-linked polyphenols, quaterphenol L(OH)(4), and moderately hindered terphenol L-Ph(OH)(3) are developed as new multidentate polyaryloxide ligands for transition-metal chemistry. The polyphenols are synthesized using ortho-metalation and metal-catalyzed cross-coupling methodologies; the synthetic routes allow for facile electronic and steric modification of the basic ligand design. The Ti(IV) coordination chemistry of these ligands reveals a diverse collection of bridged structures: dimeric [Ti(mu-PhLO3)((OPr)-Pr-i)](2) (P2(l)/n, a = 12.2699(5) Angstrom, b = 1 1.7957(5) Angstrom, c = 21.238(1) Angstrom, beta = 94.551(1)degrees, Z = 2, T = 170(2) K), dimeric [Ti-2(mu-(LO3)-L-Ph)(2)(mu-Cl)(Cl)(THF)] (P (1) over bar, a = 11.212(1) Angstrom, b = 14.165(1) Angstrom, c = 22.447(2) Angstrom, alpha = 90.440(4)degrees, beta = 93.345(4)degrees, gamma = 111.164(4)degrees, Z = 2, T= 170(2) K), and trimeric [Ti-3(mu,mu'-LO4)(mu-(OPr)-Pr-i)(2)((OPr)-Pr-i)(6)] (P(2)l/n, a = 11.1022(5) Angstrom, b = 18.7015(9) Angstrom, c = 24.409(1) Angstrom, beta = 95.369(2)degrees, Z = 4, T = 170(2) K). The reaction of TiCl3(THF)(3) with [(LO3)-L-Ph](3-) results in oxidation of Ti(III) to Ti(IV) and formation of the oxo dimer [Ti((LO3)-L-Ph)(THF)](2)(mu-O) (P (1) over bar, a = 10.8649(6) Angstrom, b = 12.1882(7) Angstrom, c = 14.3349(9) Angstrom, alpha = 65.602(3)degrees, beta = 84.390(3)degrees, gamma = 86.582(3)degrees, Z = 1, T = 200(2) K); the oxo group presumably originates from the THF solvent. The titanium centers in these environments are either 5- 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.