New {RuNO} polyoxometalate [PW11O39Ru(II)(NO)]4-: synthesis and reactivity

New Ru-containing polyoxometalate [PW11O39Ru(II)(NO)](4-) (1(4-)) was obtained in high yield by reaction of [Ru(NO)Cl5](2-) with [PW11O39](7-) and characterized by multinuclear NMR, cyclic voltammetry, IR spectroscopy, and electrospray ionization mass spectrometry (ESI-MS). The intrinsic reactivity of the {RuNO} site in 1(4-) toward various reagents has been studied using a versatile and simple ESI tandem mass spectrometric methodology for identification of the L attached at the Ru site; this approach relies on the preferential liberation of the L ligands attached at the Ru sites upon mass-selecting desired intermediates and subsequent promotion of their fragmentation. Reactions with both hydrazine and hydroxylamine lead to elimination of the nitroso group and quantitative formation of [PW11O39Ru(III)(H2O)](4-) (2(4-)) in aqueous solution. In the reaction with hydroxylamine, an intermediate with coordinated dinitrogen has been detected. An easy access to the NH3-coordinated [PW11O39RuNH3](4-) (3(4-)) complex was achieved upon reduction of 1(4-) with Sn(2+) in water.