Synthesis of triamidoamine ligands of the type (ArylNHCH2CH2)3N and molybdenum and tungsten complexes that contain an [(ArylNCH2CH2)3N]3- ligand

Aryl bromides react with (H2NCH2CH2)(3)N in a reaction catalyzed by Pd-2(dba)(3) in the presence of BINAP and NaO-t-Bu to give the arylated derivatives (ArylNHCH(2)CH(2))3N [Aryl = C6H5 (1a), 4-FC6H4 (1b), 4-t-BuC6H4 (1c), 3,5-Me2C6H3 (1d), 3,5-Ph2C6H3 (1e), 3,5-(4-t-BuC6H4)(2)C6H3 (1f), 2-MeC6H4 (1g), 2,4,6-Me3C6H2 (1h)]. Reactions between (ArNHCH2CH2)(3)N (Ar = C6H5, 4-FC6H4, 3,5-Me2C6H3, and 3,5-Ph2C6H3) and Mo(NMe2)(4) in toluene at 70 degreesC lead to [(ArNHCH2CH2)(3)N]Mo(NMe2) complexes in yields ranging from 64 to 96%. Dimethylamido species (Ar = 4-FC6H4, 3,5-Me2C6H3) could be converted into paramagnetic [(ArNHCH2CH2)(3)N]-MoCl species by treating them with 2,6-lutidinium chloride in tetrahydrofuran (THF). The direct reaction between 1a-f and MoCl4(THF)(2) in THF followed by 3 equiv of MeMgCl yielded [(ArNHCH2CH2)(3)N]MoCl species (3a-f) in high yield. If 4 equiv of LiMe instead of MeMgCl are employed in the direct reaction, then [(ArNHCH2CH2)(3)N]MoMe species are formed. Tungsten species, [(ArNHCH2CH2)(3)N]WCl, could be prepared by analogous direct methods. Cyclic voltammetric studies reveal that MoCl complexes become more difficult to reduce as the electron donating ability of the [(ArNHCH2CH2)(3)N](3-) ligand increases, and the reductions become less reversible, consistent with ready loss of chloride from {[(ArNHCH2CH2)(3)N]MoCl}(-). Tungsten complexes are more difficult to reduce, and reductions are irreversible on the CV time scale.