The role of the central atom in structure and reactivity of polyoxometalates with adjacent d-electron metal sites. computational and experimental studies of gamma-[(Xn+O4)RuIII2(OH)2(MFM)10O32](8-n)-) for MFM = Mo and W, and X = AlIII, SiIV, PV, and SVI.
The role of the central atom X in the structure and reactivity of di-Ru-substituted gamma-Keggin polyoxometalates (POMs), gamma-[(Xn+O4)RuIII2(OH)2(MFM)10O32](8-n)-), where MFM = Mo and W, and X = AlIII, SiIV, PV, and SVI., was computationally investigated. It was shown that for both MFM = Mo and W the nature of X is crucial in determining the lower lying electronic states of the polyoxoanions, which in turn likely significantly impacts their reactivity. For the electropositive X = AlIII, the ground state is a low-spin state, while for the more electronegative X = SVI the ground state is a high-spin state. In other words, the heteroatom X can be an "internal switch" for defining the ground electronic states of the gamma-M2-Keggin POMs. The obtained trends, in general, are less pronounced for MFM = Mo than for W. On the basis of the comparison of the calculated energy gaps between low-spin and high-spin states of polytungstates and polymolybdates, we predict that the gamma-M2-Keggin polytungstates could be more reactive than their polymolybdate analogues. For purposes of experimental verification the computationally predicted and evaluated polytungstate gamma-[(SiO4)RuIII2(OH)2(OH2)2W10O32]4- was prepared and characterized.
Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, 1515 Dickey Drive, Atlanta, Georgia 30322, USA.
David
D
Quiñonero
Yan
Y
Wang
Keiji
K
Morokuma
Lyuba A
LA
Khavrutskii
Bogdan
B
Botar
Yurii V
YV
Geletii
Craig L
CL
Hill
Djamaladdin G
DG
Musaev