Modification of the thermal properties of trinuclear lead(II) complex with functionalized β-diketonate

Abstract

The crystal structure and thermal properties of the related homoleptic [Pb(mtmhd)2]3 (1) and heteroleptic [{Pb(mtmhd)(hfac)}2Pb(hfac)2] (2) complexes with methoxy-substituted b-diketonate mtmhd (mtmhd= 2-methoxy-2,6,6-trimethyl-heptane-3,5-dionato (C(CH3)3-C(O)-CH-C(O)-C(CH3)2OCH3), hfac= 1,1,1,5,5,5-hexafluoropentane-2,4-dionato) are compared. Both complexes have molecular structure on the basis of trinuclear molecules with lead(II) bis-chelates bound through Pb-O bridge bonds. Complex 1 has three uncoordinated methoxy groups whereas in the heteroleptic complex 2 has all the methoxy-groups bonded to Pb atoms. Volatility and thermal stability of the complexes were examined using a vacuum sublimation test and thermogravimetric analysis. Heteroleptic complex 2 exhibits higher volatility and thermal stability. The temperature of 50 % mass loss is about 30 oC lower for 2 in comparison with 1. According to mass spectrometry and NMR data, 2 retains its trinuclear structure in the gas phase but not in the solution. Thus, heteroligand complexing was shown to improve the thermal properties of polynuclear metal complexes with functionalized b-diketonate ligands; it can be used in the design of new MOCVD precursors.