Synthesis of functional heterometallic complexes and clusters containing molybdenum and palladium or platinum, their self-assembly on gold surfaces and X-ray photoelectron spectroscopic studies

Abstract

Abstract The new heterometallic complexes [Mo2Pd2(η5-C5H4CH2CH2SCH2CH3)2(CO)6(PEt3)2] (5), trans-[Pt{Mo(η5-C5H4CH2CH2SCH2CH3(CO)3}2(CNt-Bu)2] (6) and trans-[Pt{Mo(η5-C5H4CH2CH2SCH2CH3)(CO)3}2(NCPh)2] (7) and the mononuclear complex (8) have been prepared from the new carbonylmetallate Li[Mo(η5-C5H4CH2CH2SCH2CH3)(CO)3]·2DME (4). Whereas the first three complexes are analogous to the known complexes [Mo2Pd2(η5-C5H5)2(CO)6(PEt3)2] (1a), trans-[Pt{Mo(η5-C5H5)(CO)3}2(CNt-Bu)2] (2) and trans-[Pt{Mo(η5-C5H5)(CO)3}2(NCPh)2] (3), respectively, their cyclopentadienyl ligands have been functionalized by a dialkyl sulfide group with the aim to anchor these compounds on gold surfaces. Two approaches have been used to anchor the heterometallic complex on the surface and generate monolayers. The first process consisted of depositing cluster 5 by spin coating on a gold surface. The second was the immersion of a gold surface into a cluster solution. For both procedures, the resulting deposits were analysed by STM (scanning tunneling microscopy), ellipsometry and XPS (X-ray photoelectron spectroscopy). For the layers obtained by spin coating of a solution of cluster 5, it was found that the cluster is not attached to the surface, but only deposited on it. In contrast, after immersion of a gold substrate into a solution of 5 or 6, anchoring of the complexes was clearly evidenced by XPS via the chemical shift of the S–2p binding energy toward lower binding energies.