Controlled Hydrolysis of Tripodal Titanium Amido Halides: The Influence of the Ligand Periphery upon the Basicity of the Amido-N Functions

Ortho-linked polyaryloxide ligands and their titanium complexes

Ortho-linked polyphenols, quaterphenol L(OH)4, and moderately hindered terphenol PhL(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)(OiPr)]2 (P2(1)/n, a = 12.2699(5) A, b = 11.7957(5) A, c = 21.238(1) A, beta = 94.551(1) degrees, Z = 2, T = 170(2) K), dimeric [Ti2(mu-PhLO3)2(mu-Cl)(Cl)(THF)] (P1, a = 11.212(1) A, b = 14.165(1) A, c = 22.447(2) A, alpha = 90.440(4) degrees, beta = 93.345(4) degrees, gamma = 111.164(4) degrees, Z = 2, T = 170(2) K), and trimeric [Ti3(mu,mu'-LO4)(mu-OiPr)2(OiPr)6] P2(1)/n, a = 11.1022(5) A, b = 18.7015(9) A, c = 24.409(1) A, beta = 95.369(2) degrees, Z = 4, T = 170(2) K). The reaction of TiCl3(THF)3 with [PhLO3]3- results in oxidation of Ti(III) to Ti(IV) and formation of the oxo dimer [Ti(PhLO3)(THF)]2(mu-O) (P1, a = 10.8649(6) A, b = 12.1882(7) A, c = 14.3349(9) A, 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.