Disubstituted 1,8-Diamidonaphthalene Ligands as a Flexible, Responsive, and Reactive Framework for Tantalum Complexes

Article abstract of DOI:10.1021/ic1003963

Deprotonated N,N'-disubstituted 1,8-diaminonaphthalenes (R ₂DAN^2-; R = (CH₃)₂CH, C ₆H₅, 3,5-Me₂C₆H₃) were incorporated into Ta(V) complexes employing two methods. The direct proton transfer reaction of the parent amine, 1,8-(RNH)₂C₁₀H ₆, with TaMe₃Cl₂ led to elimination of methane and formation of TaCl₃[1,8-(RN)₂C₁₀H ₆] (1, 2). Reaction of the dilithiated amido species, Li ₂R₂DAN, with TaMe₃Cl₂ or [Ta(NEt₂)₂Cl₃] yielded TaMe₃[1,8- (RN)₂C₁₀H₆] (3, 4) and TaCl(NEt ₂)₂[1,8-(RN)₂C₁₀H₆] (5, 6), respectively. X-ray structural studies of these complexes revealed the flexible coordination behavior of R₂DAN^2- by demonstrating that the ligand bonded to Ta with a coordination array dependent on the identity of the other ligands bonded to tantalum. Computational analysis of these complexes confirmed that the energetic components for binding of R ₂DAN^2- to these TaX₃²⁺ fragments were dominated by the electronic features of the metal fragment. Chemical transformations of the bound ligand were evaluated by reaction of compounds 5 and 6 with LiNMe₂ and MeLi. Simple metathesis products Ta(NEt ₂)₂NMe₂[1,8-(ⁱPrN)₂C ₁₀H₆] (R = ⁱPr 7, R = 3,5-Me₂(C ₆H₃) 8) were obtained from reactions with LiNMe ₂. In contrast, when the R group of the DAN ligand was ⁱPr, reaction with MeLi ultimately led to activation of the isopropyl group and formation of the metallaziridine [κ³-(Me ₂CN)(ⁱPrN)C₁₀H₆]Ta(NEt ₂)₂ (9) species via the elimination of methane.