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 (H(3)Btap) And Comparison To (Vo)-O-V(Btap)

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, (VO3+)-O-V, and an octahedral complex with the cis-dioxomolybdenum(VI) ion, [MoO2](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 NS3 coordination. The ability of (VO)-O-V(btap) to form eta(2)-sulfenates, while [MoO2(btap)](-) does not form stable eta(2)-sulfenates, has been ascribed to the electron-deficient, pi-accepting nature of (VO3+)-O-V relative to [(MoO2)-O-VI](2+). Crystal data for 1 (C11H16NO4S2KMo): space group Pbcn, a = 6.6596(9) Angstrom, b = 13.7446(9) Angstrom, c = 32.992(2) Angstrom, alpha = beta = gamma = 90 degrees, Z = 8. Crystal data for 2 (C24H38N2O4S4Ni): space group Pbcn, a 12.0841(3) Angstrom, b = 14.4948(4) Angstrom, c = 16.7751(4) Angstrom, alpha = beta = gamma = 90 degrees, Z = 4.