Transition‐Metal (Mn II and Co II ) Complexes with the Heteropolymolybdate Fragment [As V Mo 9 O 33 ] 7– : Crystal Structures, Electrochemical and Magnetic Properties

Two novel heteropolymolybdates, [(CH 3 ) 4 N] 8 n [M(H 2 O) 5 ] 2 n (H 3 O) 2 n [{M(H 2 O) 5 } 2 (MAs V Mo 9 O 33 ) 2 ] n [M(H 2 O) 4 (MAs V Mo 9 O 33 ) 2 ] n · 20 n H 2 O (M = Mn 2+ , 1 ; M = Co 2+ , 2 ), constructed from the new fragment (As V Mo 9 O 33 ) 7– and a transition metal have been synthesized in aqueous solution and characterized by elemental analysis, IR spectroscopy, thermal gravimetric analysis, and single‐crystal X‐ray diffraction. Structurally the title complexes resemble a sandwich‐type complex because they involve the coordination of two transition metals to two [As V Mo 9 O 33 ] 7– fragments, which derive from the well‐known B ‐β ‐ Keggin structure. Compounds 1 and 2 exhibit a one‐dimensional chain‐like framework [M(H 2 O) 4 (MAs V Mo 9 O 33 ) 2 ] 8 n – with isolated {[M(H 2 O) 5 ] 2 (MAs V Mo 9 O 33 ) 2 } 6– units residing among the chains. The magnetic properties of the two complexes were investigated to indicate typical antiferromagnetic interactions through the Mn II –O–Mn II bridge unit for complex 1 and the Co II –O–Co II bridge unit for complex 2 . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)