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)(PPh
3)
3 and OsHCl(CO)(PPh
3)
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)(PPh
3)
2-CH=CH-]
3-C
6H
3 was prepared from the reaction of RuHCl(CO)(PPh
3)
3 with 1,3,5-(CH≡C)
3-C
6H
3.
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)(PPh
3)
3 to give the bimetallic complexes RuCl(CO)(PPh
3)
2-CH=CH-CH
2-(CHOH)
2-CH
2-CH=CH-RuCl(CO)(PPh
3)
2 and [RuCl(CO)(PPh
3)
2]
2 (μ-CH=CH-CH=CH-CH=CH-) respectively. In the bimetallic complex RuCl(CO)(PPh
3)
2-CH=CH-CH
2-(CHOH)
2-CH
2-CH=CH-RuCl(CO)(PPh
3)
2, the bridging C
8-hydrocarbon chain is not conjugated. Various dehydrants were used to remove the two -OH groups to convert the C
8-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 C
nH
n hydrocarbon linkages. To this end, halide-free, Tp-ruthenium phosphonium salt TpRu(CO)(PPh
3)-CH=CH-CH
2-PPh
3BPh
4 was synthesized. The latter complex reacts with benzoaldehyde in the presence of base to give the complex TpRu(CO)(PPh
3)-CH=CH-C=CHPh. But this system failed to give the bimetallic ruthenium complexes using the carbonyl compounds such as glyoxal and terephthalaldehyde.
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