Coordination Chemistry of a Tripodal S₂ON Ligand:  Syntheses, Structures, and Reactivity of the Molybdenum(VI) and Nickel(II) Complexes of Bis(2-mercaptoethyl)-2-amino-4-methylphenol (H₃btap) and Comparison to V^VO(btap)

Abstract

The tripodal tetradentate ligand H 3 btap coordinates to V V, Mo VI, and Ni II via three different bonding modes to yield three complexes with unique ligand-based oxidation chemistry. For V V and Mo VI ( 1 ), all four of the heteroatom donors are coordinated to the metal ion forming a trigonal bipyramidal complex with the oxovanadium(V) ion, V V O 3+, and an octahedral complex with the cis -dioxomolybdenum(VI) ion, [MoO 2 ] 2+ . Only three of the heteroatom donors of H 3 btap are used to coordinate to Ni II ( 2 ), two thiolate sulfurs and the amine nitrogen, yielding a dimeric structure in which each nickel(II) ion has NS 3 coordination. The ability of V V O(btap) to form η 2 -sulfenates, while [MoO 2 (btap)] - does not form stable η 2 -sulfenates, has been ascribed to the electron-deficient, π-accepting nature of V V O 3+ relative to [Mo VI O 2 ] 2+ . Crystal data for 1 ( C 11 H 16 NO 4 S 2 KMo): space group Pbcn, a = 6.6596(9) Å, b = 13.7446(9) Å, c = 32.992(2) Å, α = β = γ = 90°, Z = 8. Crystal data for 2 ( C 24 H 38 N 2 O 4 S 4 Ni): space group Pbcn, a = 12.0841(3) Å, b = 14.4948(4) Å, c = 16.7751(4) Å, α = β = γ = 90°, Z = 4.