Towards supported catalyst models: The synthesis, characterization, redox chemistry, and structures of the complexes Ti(OAr1)4(Ar' = C6H4(2-t-Bu),C6H(2,3,5,6-Me)4)

Article abstract of DOI:10.1139/v91-027

ROBERT T. TOTHand DOUGLAS W. STEPHAN. Can. J. Chem. 69, 172 (1991). Reaction of substituted phenoxides with TiC1, affords the species Ti(OAr1), (Ar' = C6H,(2-t-BLI), 1; Ar' = C6H(2,3,5,6-Me),, 2). The compound Ti(OC6H4(2-t-Bu)),, 1, crystallizes in the tetragonal space group P42,c, with a =_orthorhombic 15.203(4) A,_space c = 8.026(3)_{group Pbcn} A, Z_with = 2,_{a =} and_16.539(7) V = 1855(2)_A b₌ .A3._16.136(6) The corn_8). ound_{c =} Ti(OC6H(2,3,5,6-Me)4)4,2,_27.716(12) A, Z = 8, and V₌ crystallizes_{7397(9) A3.} in_The the geometry of the Ti coordination sphere in these complexes is best described as pseudo-tetrahedral. In the case of 1 strict crystallographic 4 symmetry is imposed. The complex 2 exhibits reversible cyclic voltammetric behaviour consistent with a one electron reduction to the Ti(lI1) analogue. Chemical reduction of 2 employing sodium amalgam affords the quantitative formation of (C6H(2,3,5,6-Me)40)2Ti(p-OC6H(2,3,5,6-Me)4)2Na(THF)2, 3. The reaction of 3 with [(COD)Rh(p-Cl)]?does not afford the Ti(III)/Rh(I) early-late heterobimetallic (ELHB) complex (C6H(2,3,5,6-Me)40)2Ti(~-oc6H(2,3,5,6-Me)4)2Rh(COD) The nature of all products is not known; however, redox chemistry, in which electron transfer from Ti(II1) to Rh(1) occurs is evidenced by the generation of 2 and Rh(0). In addition, ligand transfer reactions giving uncharacterized Rh-alkoxides are suggested by the spectral data. The implications and ramifications for the synthesis of alkoxide bridged ELHB models of bimetallic heterogeneous catalyst systems are discussed.