A New Type of Heteropolyoxometalates formed from Lacunary Polyoxotungstate Ions and Europium or Yttrium Cations We gratefully acknowledge Dr. Gerard Parkin and Dr. Brian Bridgewater for the use of the diffractometer at Columbia University and helpful discussions. Supported by NSF-CHE9502213, NIH-GM60654-01 (LCF), NIH-MARC (FGP), NSF-CHE-9705788 (W.D.H), and NSF Grant PCM8111745 for the purchase of the 400 MHz Spectrometer. Infrastructure at Hunter College is supported in part by NIH-Research Centers in Minority Institutions Grant RR03037-08S2.