Synthesis, Structure, and Magnetic Properties of (n-Bu(4)N)(2)[{Ni(MeOH)(2)}(2){Mo(NO)}(2)(&mgr;(3)-OH)(2)(&mgr;-OMe)(4){Mo(5)O(13)(OMe)(4)(NO)}(2)], a New Type of Polyoxometalate Incorporating a Rhomb-like Cluster.

The oxo-nitrosyl compound (n-Bu(4)N)(2)[{Na(MeOH)}Mo(5)O(13)(OMe)(4)(NO)].3MeOH reacts with various nickel(II) salts in methanol to give (n-Bu(4)N)(2)[{Ni(MeOH)(2)}(2){Mo(NO)}(2)(&mgr;(3)-OH)(2)(&mgr;-OMe)(4){Mo(5)O(13)(OMe)(4)(NO)}(2)], which has been characterized by single-crystal X-ray diffraction analysis and magnetic susceptibility measurements. This reaction shows the dual behavior of the defect Lindqvist-type species [Mo(5)O(13)(OMe)(4)(NO)](3)(-), which can act both as a ligand and as a source of the {Mo(NO)}(3+) unit. Furthermore, the reaction is reminiscent of the dissolution-precipitation of oxide supports in the preparation of supported catalysts and provides a novel illustration of the potential of polyoxometalates for probing the reactivity of oxides. The new polyoxomolybdate is made of a central rhomb-like {Ni(2)Mo(2)} cluster linked to two terminal [Mo(5)O(13)(OMe)(4)(NO)](3)(-) units, each terminal cluster being linked to a molybdenum center of the central unit through two oxo ligands. The two Ni(II) ions are coupled in a ferromagnetic way (J = 13.1 cm(-)(1)).