The quantitative syntheses of MXH, phases (M = Sc, La, Gd, Er, Lu; X = C1 (and Br for Gd, Er); x N 0.6-0.7) together with their intercalates A,MXH, (A = Li, some Na, K; M = Sc, Y, Gd (but not Er, Lu)) have been accomplished by stoichiometric reactions of MX,, MH2 (or H2), M, and AX in sealed Ta or Nb containers at 750-900 OC. All MXH, phases have the ZrCIor ZrBr-type (3R) heavy-atom structures. The phases ScClH,, nonstoichiometric for 0.3 < x S 0.75, and LaClH are indistinguishable from the previously reported monochlorides. The X-ray structure of ScClH has been refined. The lithium intercalates, Li,MCIH,, for M = Sc, Y , and Gd are also nonstoichiometric in hydrogen, and all intercalates have the ZrBr heavy-atom structure. The Li0,*YC1 and Lio,,GdC1 phases previously reported from X-ray studies are obtained only in the presence of hydrogen. High values of x result in explusion of much of the lithium from the yttrium and gadolinium chloride derivatives. Hydrogen pressure, phase, and volume relationships are also considered.(aand so the question has likewise arisen as to whether these apparent ternary intercalates were indeed Li,MClH, quaternary phases.The present article reports the clarification of the Sc/CI/H system vis-a-vis "ScCI", some similar experiments regarding "LaCl" and "ErBr", and a study of the intercalation reactions of lithium, sodium, and potassium with the gadolinium, scandium, and yttrium monochloride and monobromide hydrides together with some exploratory results regarding analogous products for M = La, Er, and Lu. Experimental Section
