The hydrogenphosphate complex of (1,5-cyclooctadiene)iridium(I), {[Bu 4N][(1,5-COD)Ir · HPO 4]} n: synthesis, spectroscopic characterization, and ES-MS of a new, preferred precursor to HPO 42− and Bu 4N + stabilized Ir(0) n nanoclusters

Abstract

The synthesis and characterization of a previously unknown, rare organometallic–phosphate complex, {[Bu 4N][(1,5-COD)Ir · HPO 4]} n ( 1), is described. Characterization of 1 was accomplished by elemental analysis, electrospray mass spectrometry (ES-MS), and 1H and 13C NMR which established the symmetry of the product as at least C 2 or C s. The ES-MS reveals an interesting, Ir(I) to Ir(III) oxidative process with intense peaks displaying the 191Ir/ 193Ir isotopic distribution patterns expected for the fragments [(1,5-COD)Ir III(HPO 4) 2] −, [(C 8H 11) 2(Ir III) 2(PO 4)(HPO 4)(H 2O)] −, and [(C 8H 11) 2(Ir III) 2(PO 4)(HPO 4)(H 2O) 2] −. These fragments, in turn, provide evidence for a structure with two HPO 4 2− groups attached to a single Ir, for example ring structures (of at least such C 2 or C s symmetry) such as {[Bu 4N][(1,5-COD)Ir · HPO 4]} 2. Complex 1 is significant since it is known to be the preferred, compositionally precise precursor to the prototype example of a recently discovered class of novel, HPO 4 2− and Bu 4N + stabilized nanoclusters, (Bu 4N) 2 n 2 n+ [Ir(0) n · (HPO 4) n ] 2 n− . Such nanoclusters are being extended, via their analogous hydrogenphosphate-organometallic precursors (1,5-COD)M + or 2+/HPO 4 2− (M=Rh(I), Ru(II), Pt(II)) to their corresponding, catalytically active [M(0) n · (HPO 4) n ] 2 n− nanoclusters.