TETRAHYDROQUINOLINYL AMIDO AND INDOLINYL AMIDO COMPLEXES OF TANTALUM AS MODELS FOR SUBSTRATE-CATALYST ADDUCTS IN HYDRODENITROGENATION CATALYSIS

The reactions of TaCl5 with Me(3)SiNC(9)H(10) or LiNC9H10, where [NC9H 10](-) = tetrahydroquinolinyl (the amido anion of tetrahydroquinoline) , afford selective preparative routes to the complete series of amido halide complexes of tantalum(V) Ta(NC9H10)(n)Cl-5-n for n = 1-5 (compo unds 1-5, respectively). The monokis(tetrahydroquinolinyl) complex is isolated as an ether adduct Ta(NC9H10)Cl-4(OEt(2)) while the complexes Ta(NC9H10)(n)Cl-5-n (n = 2-5) are found to be base-free, monomeric sp ecies. The related complexes of indolinyl [NC8H8](-) (the amido anion of indoline), Ta(NC8H8)(n)Cl-5-n(THF) for n = 1 (6) or 2 (7), have bee n prepared from TaCl5, Me(3)SiNC(8)H(8), and THF. An X-ray structural determination of Ta(NC9H10)(2)Cl-3 (2) reveals that it adopts a trigon al bipyramidal geometry with equatorial amido ligands that are closer to lying parallel (within) than perpendicular to the TBP equatorial pl ane. Routes to mixed-ligand aryloxide-amide complexes have been develo ped from either aryloxide or amido precursors but not from both. Thus, Ta(NC9H10)(OAr)Cl-3(OEt(2)) (8), where Ar = 2,6-(C6H3Pr2)-Pr-i, and T a(NC8H8)(OAr)Cl-3(OEt(2)) (9) are available from reacting Ta(OAr)Cl-4( OEt(2)) with Me(3)SiNC(9)H(10) and Me(3)SiNC(8)H(8), respectively, whi le Ta(NC9H10)(2)(OAr)(2)Cl (10) is available from Ta(NC9H10)(2)Cl-3 (2 ) and excess LiOAr . OEt(2). The alkyl derivatives Ta(NC9H10)(OAr)Me(2 )Cl (11), Ta(NC9H10)(OAr)Et(2)Cl (12), Ta(NC9H10)(2)(OAr)(2)Me (13), a nd Ta(NC9H10)Me(2)Cl(2) (14) are prepared from AlR(3) or ZnR(2) reagen ts and the appropriate precursor. Thermolyzing compounds 4, 5, and 11- 14 in solution afforded no evidence for the formation of any eta(2)(N, C)-heterocyclic complexes arising from metalation of a NC9H10 ligand.