Self‐Assembly of [ B ‐SbW 9 O 33 ] 9− Subunit with Transition Metal Ions (Mn 2+ , Cu 2+ , Co 2+ ) in Aqueous Solution: Syntheses, Structures and Magnetic Properties of Sandwich Type Polyoxometalates with Subvalent Sb III Heteroatom

Rational self‐assembly of Sb 2 O 3 and Na 2 WO 4 , or (NH 4 ) 18 [NaSb 9 W 21 O 86 ] with transition‐metal ions (Mn 2+ , Cu 2+ , Co 2+ ), in aqueous solution under controlled conditions yield a series of sandwich type complexes, namely, Na 2 H 2 [Mn 2.5 W 1.5 (H 2 O) 8 ( B ‐β‐SbW 9 O 33 ) 2 ]⋅32 H 2 O (1) , Na 4 H 7 [Na 3 (H 2 O) 6 Mn 3 (μ‐OAc) 2 ( B ‐α‐SbW 9 O 33 ) 2 ]⋅20 H 2 O (OAc=acetate anion) (2) , NaH 8 [Na 2 Cu 4 Cl( B ‐α‐SbW 9 O 33 ) 2 ]⋅21 H 2 O (3) , Na 8 K[Na 2 K(H 2 O) 2 {Co(H 2 O)} 3 ( B ‐α‐SbW 9 O 33 ) 2 ]⋅ 10 H 2 O (4) , and Na 5 H[{Co(H 2 O) 2 } 3 W(H 2 O) 2 ( B ‐β‐SbW 9 O 33 ) 2 ]⋅11.5 H 2 O (5) . These structures are determined by using the X‐ray diffraction technique and further characterized by obtaining IR spectra and performing elemental analysis. Structure analysis reveals that polyoxoanions in 1 and 5 comprise of two [ B ‐β‐SbW 9 O 33 ] 9− building units, whereas 2 , 3 , and 4 consist of two isomerous [ B ‐α‐SbW 9 O 33 ] 9− building blocks, which are all linked by different transition‐metal ions (Mn 2+ , Cu 2+ , or Co 2+ ) with different quantitative nuclearity. It should be noted that compound 2 represents the first one‐dimensional sinusoidal chain based on sandwich like tungstoantimonate building blocks through the carboxylate‐bridging ligands. Additionally, 3 is constructed from sandwiched anions [Na 2 Cu 4 Cl( B ‐α‐SbW 9 O 33 ) 2 ] 9− linked to each other to form an infinitely extended 2D network, whereas 5 shows an interesting 3D framework built up from offset sandwich type polyoxoanion [{Co(H 2 O) 2 } 3 W(H 2 O) 2 ( B ‐β‐SbW 9 O 33 ) 2 ] 6− linked by Co 2+ and Na + ions. EPR studies performed at 110 K and room temperature reveal that the metal cations (Mn 2+ , Cu 2+ , Co 2+ ) reside in a square‐pyramidal geometry in 2 , 3 , and 4 . The magnetic behavior of 1 – 4 suggests the presence of weak antiferromagnetic coupling interactions between magnetic metal centers with the exchange integral J =−0.552 cm −1 in 2 .