The reactions of LaCl 3 and YCl 3 with 1,3-bis(1,3-dimethyl-1 H -pyrazol-4-yl)propane-1,3-dione (HL) and 1,10-phenanthroline (Phen) in the presence of a base afford complexes [La(L) 3 (Phen)] ( I ) and [Y(L) 3 (Phen)] ( II ). Unstable solvates I · iso -PrOH ( III ) and II · iso -PrOH ( IV ) are obtained from solutions of the complexes in 2-propanol, and their structures are determined by X-ray diffraction analysis (CIF files CCDC 1026802 ( III ) and 1026808 ( IV )). The compositions of the complexes are additionally studied by 1 H, 13 C, 89 Y, and 139 La NMR methods. Fragmentation is studied by laser desorption/ionization (LDI) and electrospray ionization (ESI) mass spectrometry.