Reactions of group 13 metal trialkyls with oxamides

Alkyl aluminum-, gallium-, and indium oxamidates Me4Al2(dpoa) (1), Me4Al2(dboa) (2), Me4Ga2(dpoa) (3), Me4Ga2(dboa) (4), tBu4Ga2(dpoa) (5) and Me4In2(dboa) (6) (dpoa-H2 = N,N′-diphenyloxamide, dboa-H2 = N,N′-di-tert-butyloxamide) have been prepared and characterized. Compounds 1–3, 5 and 6 exist in the form of isomers a only, with a skeleton framework of the molecules consisting of two almost flat, coplanar and fused MNOC2 (M = Al, Ga, In) heterocyclic rings. Depending on the reaction conditions, the compound 4 was obtained as the isomer 4a or as the mixture of two isomers 4a and 4b. Molecular structures of the compounds 1a–6a have been determined by X-ray crystallography. A structure of the isomer 4b was proposed on the basis of NMR spectroscopy. A skeleton framework of the 4b molecule consists of two fused different cycles, GaO2C2 and GaN2C2.

Graphical abstractN,N′-Diphenyloxamide (dpoa-H2) and N,N′-di-tert-butyloxamide (dboa-H2) reacted with R3M in a 1:2 M ratio to produce quantitatively the oxamidates of group 13 metals, R4M2ox (R = alkyl groups; M = Al, Ga, In; ox = dpoa, dboa).Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Group 13 metal trialkyls react with N,N′-disubstituted oxamides. Oxamidates R4M2(ox) (R = alkyl group; M = Al, Ga, In; ox = oxamidate unit) are formed. ► Isomers with oxamidate ligands in the trans configuration are the main products. ► Only gallium oxamidates exhibit a configurational isomerism.