Heterobimetallicd—f Metal Complexes as Potential Single-Source Precursors for MOCVD: Structure and Thermodynamic Study of the Sublimation of [Ni(salen)Ln(hfa)3], Ln = Y, Gd

Abstract

Heterobimetallic [Ni(salen)Ln(hfa)3] species [H2salen and Hhfa being N,N′‐ethylenebis(salicylideneimine) and hexa‐fluoroacetylacetone respectively], where Ni(salen) acts as a neutral chelating ligand towards LnIII, form a series of isostructural compounds for Ln = YIII and any lanthanideIII cation from La to Yb. They are also isostructural with some of the [Cu(salen)Ln(hfa)3] compounds. They sublime without decomposition under vacuum which makes them potential single‐source precursors in MOCVD. Sublimation, thermal behaviour, pressure and composition of the vapour phase versus temperature have been studied for the yttrium derivative, by means of thermal analyses, and mass spectrometry using a Knudsen cell. The dissociation process [Ni(salen)Y(hfa)3] = Ni(salen) + Y(hfa)3 has been thermodynamically investigated. Information on the solid‐state intermolecular interactions in relation with volatility was obtained through the crystal structure determination of the gadolinium derivative. A comparative structural study of [Ni(salen)Gd(hfa)3] and [Cu(saloph)Y(hfa)3], [H2saloph is N,N′‐o‐phenylenebis(salicylideneimine)], allows to under‐stand why the latter is less volatile than the former despite similar molecular and solid‐state structures.

The use of 3d-metal complexes as ligands to prepare volatile 4f–3d heterobimetallic complexes

“…This paper reviews our results about synthesis, structure and volatility of such f-d heterobimetallic complexes and presents new data from mass spectrometry studies. 3 ] were prepared according to the method described in [1,11,12]. Yield: 80-90%.…”

“…Therefore, we assumed that f-d heterobimetallic complexes of formula [M(salen)Ln(hfa) 3 ] (M = Cu, Ni) could be volatile. First results on their volatility appeared in [11].…”

“…Two series of complexes were prepared and investigated: [Cu(saloph)Ln(hfa) 3 ] and [Ni(salen)Ln(hfa) 3 ] [11]. The crystal structures of [Ni(salen)Gd(hfa) 3 ] and [Cu(saloph)Y(hfa) 3 ] were determined.…”

“…The Schiff base complex M(salen) acts as a terminal ligand to co-ordinatively saturate the f-element. From the single crystal structures of the La derivative [9], and of the Gd, Yb and Y derivatives [11], it may be inferred that [Ni(salen)Y(hfa) 3 ] and [Ni(salen)Ln(hfa) 3 ] are isostructural for Ln going from La to Yb. The Lu derivative was not investigated.…”

“…For [Ni(salen)Y(hfa) 3 ] as an example, mass-spectrometry analyses have proved that both the heterobimetallic species and the homometallic parent complexes M(salen) and Ln(hfa) 3 exist in the vapour phase, and that the partial pressure of dissociation products rapidly increase with temperature [11].…”