Electron‐Rich Mo^IV₃‐Polyoxomolybdates Resembling the Paratungstic Archetype

Abstract The first polyoxometalates (POMs) composed of Mo IV , Mo V 2 , discrete d 1 ‐Mo V and Mo VI , [Mo IV 3 Mo V 6 Mo VI 4 O 32 ( μ 2 ‐OH)( μ 3 ‐OH)py 9 ] ( 1 ), was prepared from the solvothermal partial oxidation of [Mo IV 3 O 2 (O 2 CCH 3 ) 6 (H 2 O) 3 ]ZnCl 4 in a mixture of pyridine and water. The Mo V =O adduct‐free unit [H 2 Mo 12 O 33 py 9 ] presents the 11 e ‐reduced Mo derivative of the paratungtic archetype. The use of methanol, ethanol, n ‐propyl alcohol and triglycol instead of water produced the isostructural [Mo IV 3 Mo V 6 Mo VI 4 O 32 ( μ 3 ‐OH)( μ 2 ‐OR)py 9 ](R=CH 3 , 2 ; C 2 H 5 , 3 ; C 3 H 7 , 4 ; C 2 H 4 OH, 5 ), providing the first examples of Mo IV 3 −POMs containing bridging alkoxyl groups. The addition of [Cr III Mo 6 O 24 ] 9− led to the substitution of {Mo V =O} 3+ with {Cr III ‐py} 3+ in the allomer [Mo IV 3 Mo V 5 Mo VI 4 Cr III O 32 ( μ ‐OH) 2 py 10 ] ( 6 ). Using a mixture of Mo 3 and MoW 2 precursors afforded W VI ‐incorporated allomer [Mo IV 3 Mo V 6 Mo VI W VI 3 O 32 ( μ ‐OH) 2 py 9 ] ( 7 ). The complete substitution of Mo VI with W VI by using a mixture of the Mo 2 W, MoW 2 and W 3 precursors produced the diamagnetic [Mo IV 3 Mo V 6 W VI 4 O 33 ( μ 3 ‐OH)py 9 ] − ( syn ‐ 8 ) resulting from the anti → syn conversion between the top and bottom M 3 triads concomitant with Mo V ‐Mo V bonding. Both anti ‐ 1‐7 and syn ‐ 8 have been characterized by X‐ray single crystal structural analyses. The spin distribution and magnetic interactions have been investigated by temperature‐dependent magnetic susceptibility and DFT theoretical calculations. Heterogeneous hydrogen transfer catalysis has been examined by the Lewis catalysis field (LCF) theory.