Abstract: The invention provides rare earth compounds of formula (ML.sub.3).sub.x A!.sub.y where M is one or more of the rare earth metals and yttrium, L is a beta-diketone type ligand, A is a polyether or polyamine, and x and y are each 1 or 2. These compounds are precursors for chemical vapor deposition (CVD) of oxide layers in applications such as superconductors, piezoelectrics, microwaves, fuel cells, radiation detectors, optoelectronics, and catalysts. They are air and moisture stable, low melting, vacuum volatile at low temperatures leaving minimum residue and give good quality metal oxide deposits uncontaminated by fluorine. These compounds also have excellent solubility in a wide range of organic solvents, and are potentially useful as oil lubricant additives and in fuels.

Abstract: Novel metallo-organic complexes of the formula (M.sub.x X.sub.z. nL)y where M is an alkaline earth metal, a transition metal(at. Nos. 21-30, 39-48 and 72-80 inclusive) or a rare earth metal (at. Nos. 57-71 inclusive), X is an anion e.g. Cl.sup.-, Br.sup.-, NO.sub.3 -, NCS.sup.- etc. and L is a Lewis base, are prepared by reacting a source of the metal M under anhydrous conditions with an anhydrous ammonium salt of the anion X in the presence of the Lewis base, and cooling the reaction mixture to precipitate the complex.