Molybdenum(VI) network polymers based on anion-pi interaction and hydrogen bonding: Synthesis, crystal structures and oxidation catalytic application

摘要

A crystallographic investigation of anion-pi interactions and hydrogen bonds on the preferred structural motifs of molybdenum(VI) complexes has been carried out. Two molybdenum(VI) network polymers MoO_2F_4-(Hinca)2 (1) and MoO_2F_3(H_2O)-(Hinpa) (2), where inca = isonicotinamide and inpa = isonipecotamide, have been synthesized, crystallographically characterized and successfully applied to alcohol oxidation reaction. Complex 1 crystallizes in the monoclinic space C2/c: a = 16.832(3) A, b = 8.8189(15)A, c = 12.568(2)A, beta = 118.929(3) deg, V= 1560.1(5)A~3, Z = 4. Complex 2 crystallizes in the triclinic space P-1: a = 5.459(2)A, b = 9.189(4)A, c=12.204(5)A, alpha = 71.341(6) deg, 0 = 81.712(7) deg, gamma = 77.705(7) deg, V= 564.8(4) A~3, Z = 2. Complex 1 consists of hydrogen bonding and anion-pi interactions, both of which are considered as important factors for controlling the geometric features and packing characteristics of the crystal structure. The geometry of the sandwich complex of [MoO_2F_4]~(2-) with two pyridine rings indicates that the anion-pi interaction is an additive and provides a base for the design and synthesis of new complexes. For complex 2, the anions and the protonated inpa ligands form a 2D supramolecular network by four different types of hydrogen contacts (N-H...F, N-H...O, O-H...F and O-H...O). The catalytic ability of complexes 1 and 2 has also been evaluated by applying them to the oxidation of benzyl alcohol with TBHP as oxidant.