Synthesis and characterization of bimetallic and trimetallic complexes with hydrocarbon linkages

Abstract

The objective of my research project is to synthesize multimetallic ruthenium or osmium complexes with metal centers bridged with π-conjugated hydrocarbon chains. The majority of the new complexes were prepared by insertion reaction. The organic compound 1,3,5-triethynylbenzene is the starting material for the synthesis of complexes with 3-fold rotational symmetry. Metal-hydride complexes such as RuHCl(CO)(PPh3)3 and OsHCl(CO)(PPh3)3 were used to react with 1,3,5-triethynylbenzene to give metal-vinyl complexes with conjugated hydrocarbon bridges. For example, trimetallic ruthenium complex 1,3,5-[RUCl(CO)(PPh3)2-CH=CH-]3-C6H3 was prepared from the reaction of RuHCl(CO)(PPh3) 3 with 1,3,5-(CH≡C)3-C6H3. To synthesize bimetallic complexes, the diacetylenes-containing organic compounds 1,7-octadiyne-4,5-diol and trans-hex-3-ene-1,5-diyne were used. These two compounds reacted with RuHCl(CO)(PPh3)3 to give the bimetallic complexes RuCl(CO)(PPh3)2-CH=CH-CH2-(CHOH)2-CH2-CH=CH-RuCl(CO)(PPh3)2 and [RuCl(CO)(PPh3)2]2 (μ-CH=CH-CH=CH-CH=CH-) respectively. In the bimetallic complex RuCl(CO)(PPh3)2-CH=CH-CH2-(CHOH)2-CH2-CH=CH-RuCl(CO)(PPh3)2, the bridging C8-hydrocarbon chain is not conjugated. Various dehydrants were used to remove the two -OH groups to convert the C8-chain to conjugated one, although the reactions were unsuccessful in my experiments. Beside insertion reaction, Wittig reaction was explored as an alternative approach to synthesize bimetallic complexes with CnHn hydrocarbon linkages. To this end, halide-free, Tp-ruthenium phosphonium salt TpRu(CO)(PPh3)-CH=CH-CH2-PPh3BPh4 was synthesized. The latter complex reacts with benzoaldehyde in the presence of base to give the complex TpRu(CO)(PPh3)-CH=CH-C=CHPh. But this system failed to give the bimetallic ruthenium complexes using the carbonyl compounds such as glyoxal and terephthalaldehyde.

Date of Award	2001
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology