Convergent synthesis of alkynylbis(bidentate phosphine)ruthenium dendrimers

Publisher:
The American Chemical Society
Publication Type:
Journal Article
Citation:
Organometallics, 2003, 22 (7), pp. 1402 - 1413
Issue Date:
2003-01
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The "first-generation" alkynylruthenium dendrimers 1,3,5-C6H3(4-CCC6H4CC-trans-[Ru(dppe)2]CC-3,5-C6H3{4-CCC6H4CC-trans-[Ru(4-CCC6H4R)(dppe)2]}2)3 [R = H (19), NO2 (20)], containing nine dialkynylruthenium centers, have been prepared by convergent synthesis. Reaction of 3 equiv of 1-iodo-4-trimethylsilylethynylbenzene with triethynylbenzene, under Sonogashira coupling conditions, followed by deprotection with tetra-n-butylammonium fluoride affords 1,3,5-C6H3(4-CCC6H4CCH)3 (2), which is reacted with cis-[RuCl2(L)2] (L = dppe, dppm) to afford the octopolar, triruthenium dendritic cores 1,3,5-C6H3{4-CCC6H4CC-trans-[RuCl(L)2]}3 [L = dppe (5), L = dppm (6)] via the vinylidene intermediates [1,3,5-C6H3{4-CCC6H4CH=C-trans-[RuCl(L)2]}3](PF6)3 [L = dppe (3), L = dppm (4)]. Reaction of 5 with terminal alkynes 4-HCCC6H4R (R = H, NO2, NEt2) affords a series of related dialkynylruthenium zero-generation dendrimers 1,3,5-C6H3{4-CCC6H4CC-trans-[Ru(4-CCC6H4R)(dppe)2]}3 [R = H (7), NO2 (8), NEt2 (9)]. Reaction of 3 equiv of trans-[Ru(4-CCC6H4CCH)(CCPh)(dppe)2] with 1,3,5-triiodobenzene under Sonogashira coupling conditions also affords 7, together with the homo-coupled trans,trans-[(dppe)2(PhCC)Ru(4,4'-CCC6H4CCCCC6H4CC)Ru(CCPh)(dppe)2]. The first-generation dendrimers 19 and 20 are prepared by coupling core 5 with the dendrons 1-(HCC)C6H3-3,5-{4-CCC6H4CC-trans-[Ru(4-CCC6H4R)(dppe)2]}2 [R = H (17), NO2 (18)].
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