SYNTHESIS AND CHARACTERIZATION OF KEGGIN DERIVATIVES CONTAINING AN [MO(NO)](3+) UNIT - (N-BU(4)N)(4)[PM(11)O(39)(MO(NO))] (M=MO, W)

The diamagnetic complexes (n-Bu(4)N)(4)[PM(11)O(39){Mo(NO)}] (M=Mo, W) have been synthesized in acetonitrile by reaction of the lacunary [PM(11)O(39)](7-) species, generated in situ through degradation of the parent complete Keggin anions by n-Bu(4)NOH, with either (n-Bu(4)N)(2)[Mo5O13(OMe)(4)(NO){Na(MeOH)}] . 3MeOH or [Mo(NO)(OMe)(Me(2)CNO)(2)](2) acting as a source of the [Mo(NO)](3+) unit. These new nitrosyl-oxometalates have been characterized by elemental analysis, infrared spectroscopy, electrochemistry, and P-31 and W-183 spectroscopy. Comparison of electrochemical and spectral data of the nitrosyl derivatives to those of the parent Keggin anions demonstrate that the electron-withdrawing effect of the nitrosyl ligand is opposed to the overall increase in charge of the heteropolymetalate framework arising from the replacement of an MO(4+) unit by an [Mo(NO)](3+) unit. In the case of [PW11O39{Mo(NO)}](4-), W-183 NMR data also support some delocalization of the Mo(II) d-electrons onto the polytungstate ligand.