The crystal and molecular structures of dioxo mo(VI) complexes of tripodal, tetradentate N,S-donor ligands

Abstract

The crystal and molecular structures of the complexes MoO 2((SCH 2CH 2) 2NCH 2CH 2SCH 3), I and MoO 2((SCH 2CH 2) 2NCH 2CH 2N(CH 3) 2), II, have been determined from X-ray intensity data collected by counter methods. Compound I crystallizes in two forms, Ia and Ib. In form Ia the space group is P2 1/n with cell parameters a = 7.235(2), b = 7.717(2), c = 24.527(6) Å, β = 119.86(2)°, V = 1188(1) Å 3, Z = 4. In form Ib the space group is P2 1/c with cell parameters a = 14.945(5), b = 11.925(5), c = 14.878(4) Å, β = 114.51(2)°, V = 2413(3) Å 3, Z = 8. The molecules of I in Ia and Ib are very similar having an octahedral structure with cis oxo groups, trans thiolates ( cis to both oxo groups) and N and thioether sulfur atoms trans to oxo groups. Average ditances are MoO = 1.70, MoS (thiolate) = 2.40, MoN = 2.40 and MoS (thioether) = 2.79 Å. Molecule II crystallizes in space group P2 12 12 1 with a = 7.188(1), b = 22.708(8), c = 7.746(2) Å, V = 1246(1) Å 3 and Z = 4. The coordination about Mo is octahedral with cis oxo groups, trans thiolates and N atoms trans to oxo. Distances in the first coordination sphere are MoO = 1.705(2), 1.699(2), MoS = 2.420(1), 2.409(1) and MoN = 2.372(2), 2.510(2) Å. The conformational features of the complexes are discussed. Complex I displays MoO and MoS distances which are very similar to those found by EXAFS in sulfite oxidase. This similarity is discussed.