The heterocyclic complexes [η 1( N)-QUIN]Ta(OAr) 3Cl 2 ( 1) and [η 1( N)-6MQ] Ta(OAr) 3Cl 2 ( 2) (where Ar = 2,6-diisopropylphenyl, QUIN = quinoline, and 6MQ = 6-methylquinoline) are prepared from Ta(OAr) 3Cl 2(OEt 2) and QUIN or 6MQ in pentane. [η 1 ( N)-6MQ]Ta(OAr) 2Cl 3 ( 4) is prepared similarly from Ta(OAr) 2Cl 3(OEt 2). Upon rapid, two-electron reduction of these complexes, an η 1( N) → η 2( N,C) bonding rearrangement is effected and the thermally sensitive, d 2 species [η 2( N,C)-QUIN]Ta(OAr) 3 ( 5), [η 2( N,C)-6MQ]Ta(OAr) 3 ( 6), and [η 2( N,C)-6MQ]Ta(OAr) 2Cl(OEt 2) ( 9) can be isolated. Alternatively, [η 2( N,C)-6MQ]Ta(OAr) 2Cl(OEt 2) ( 9) can be prepared in higher yield from (η 6-C 6Me 6)Ta(OAr) 2Cl and 6MQ. The trimethylphosphine adducts [η 2( N,C)-QUIN] Ta(OAr) 3(PMe 3) ( 7) and [η 2( N,C)-6MQ]Ta(OAr) 3(PMe 3) ( 8) can be prepared by simple coordination of PMe 3 to the base-free compounds 5 and 6. When Ta(OAr) 2Cl 3(OEt 2) is reduced by one electron in the presence of QUIN, 6MQ, or pyridine, the d 1 bis(ligand) complexes [η 1( N)-QUIN] 2Ta(OAr) 2Cl 2 ( 10), [η 1( N)-6MQ] 2Ta(OAr) 2Cl 2 ( 11), and [η 1( N)-py] 2Ta(OAr) 2Cl 2 ( 12) can be isolated. Complexes 10 and 11 are not readily converted to the η 2( N,C) analogues 5 and 6 by further reduction. Under mild hydrogenation conditions, the only heterocyclic ligands which are hydrogenated are those bound in the η 2( N,C) mode to a d 2 metal. Structural studies on [η 2( N,C)-6MQ]Ta(OAr) 3(PMe 3) ( 8) and [η 2( N,C)-6MQ]Ta(OAr) 2Cl(OEt 2) ( 9) have been undertaken. [η 2( N,C)-6MQ]Ta(OAr) 3(PMe 3) ( 8) crystallizes in the monoclinic space group C2 1/ c (No. 15), with a = 32.849 (3) Å, b = 19.579 (2) Å, c = 23.822 (2) Å, β = 135.69 (49)°, and V = 10702 (2) Å 3 with Z = 8 and ρ caled = 1.16 g cm −3. [η 2( N,C)-6MQ]Ta(OAr) 2Cl(OEt 2) ( 9) crystallizes in the monoclinic space group P2 1/ n (No. 14) with a = 12.059 (9) Å, b = 17.975 (14) Å, c = 17.949 (13) Å, β = 100.29 (3)°, and V = 3828 (9) Å 3 with Z = 4 and ρ caled = 1.37 g cm −3. Both structures indicate an interruption of aromaticity to the heterocyclic ring only when bound in this fashion, consistent with the observation of 1,2,3,4-tetrahydroquinoline as the principal hydrogenation product of [η 2( N,C)-QUIN]Ta(OAr) 3 ( 5) with no decahydroquinoline being observed.