Study of ferrocenyl-substituted Co2(CO)6-bispropargylic alcohol complexes as substrates for the formation of chains and macrocycles

Treatment of [Fc-1-R1-1′-R2] (R1 = H, R2 = CH(O); R1 = H, R2 = CMe(O); R1 = R2 = CMe(O)) with LiCCCH2OLi (prepared in situ from HCCCH2OH and n-BuLi) affords the ferrocenyl-substituted but-2-yne-1,4-diol compounds of general formula [Fc-1-R1-1′-{CR(OH)CCCH2OH}] (R1 = R = H (1a); R1 = H, R = Me (1b); R1 = CMe(O), R = Me (1c)) in low to high yields, respectively (where Fc = Fe(η5-C5H4)2). In the case of the reactions of [Fc-1-R1-1′-R2] (R1 = H, R2 = CH(O); R1 = R2 = CMe(O)), the by-products [Fc-1-R1-1′-{CR(OH)(CH2)3CH3}] (R1 = R = H (2a); R1 = CMe(O), R = Me (2c)) along with minor quantities of [Fc-1,1′-{CMe(OH)(CH2)3CH3}2] (3) are also isolated; a hydrazide derivative of dehydrated 2c, [1-(CMeCHCH2CH2CH3)–1′-(CMeNNH-2,4-(NO2)2C6H3)] (2c′), has been crystallographically characterised. Interaction of 1 with Co2(CO)8 smoothly generates the alkyne-bridged complexes [Fc-1-R1-1′-{Co2(CO)6-μ-η2-CR(OH)CCCH2OH}] (R1 = R = H (4a); R1 = H, R = Me(4b); R1 = CMe(O), R = Me (4c)) in good yield. Reaction of 4a with PhSH, in the presence of catalytic quantities of HBF4 · OEt2, gives the mono- [Fc-1-H-1′-{Co2(CO)6-μ-η2–CH(SPh)CCCH2OH}] (5) and bis-substituted [Fc-1-H-1′-{Co2(CO)6-μ-η2-CH(SPh)CCCH2SPh}] (6) straight chain species, while with HS(CH2)nSH (n = 2,3) the eight- and nine-membered dithiomacrocylic complexes [Fc-1-H-1′-{cyclo-Co2(CO)6-μ-η2-CH(S(CH2)n–)CCCH2S–}] [n = 2 (7a), n = 3 (7b)] are afforded. By contrast, during attempted macrocyclic formation using 4b and HSCH2CH2OCH2CH2SH dehydration occurs to give [Fc-1-H-1′-{Co2(CO)6-μ-η2-C(CH2)CCCH2OH}] (8). Single crystal X-ray diffraction studies have been reported on 2c′, 4b, 4c, 7b and 8.

A series of ferrocenyl-containing but-2-yne-1,4-diols have been prepared and their alkynic moieties complexed with dicobalt hexacarbonyl units; acid-catalysed substitution of the hydroxyl groups in the resultant complexes by thiol-based nucleophiles leads to chain, macrocyclic and dehydration products.Figure optionsDownload as PowerPoint slide