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

Treatment of [Fc-1-R 1 -1′-R 2 ] (R 1  = H, R 2  = CH(O); R 1  = H, R 2  = CMe(O); R 1  = R 2  = CMe(O)) with LiC CCH 2 OLi (prepared in situ from HC CCH 2 OH and n -BuLi) affords the ferrocenyl-substituted but-2-yne-1,4-diol compounds of general formula [Fc-1-R 1 -1′-{CR(OH)C CCH 2 OH}] (R 1  = R = H ( 1a ); R 1  = H, R = Me ( 1b ); R 1  = CMe(O), R = Me ( 1c )) in low to high yields, respectively (where Fc = Fe(η 5 -C 5 H 4 ) 2 ). In the case of the reactions of [Fc-1-R 1 -1′-R 2 ] (R 1  = H, R 2  = CH(O); R 1  = R 2  = CMe(O)), the by-products [Fc-1-R 1 -1′-{CR(OH)(CH 2 ) 3 CH 3 }] (R 1  = R = H ( 2a ); R 1  = CMe(O), R = Me ( 2c )) along with minor quantities of [Fc-1,1′-{CMe(OH)(CH 2 ) 3 CH 3 } 2 ] ( 3 ) are also isolated; a hydrazide derivative of dehydrated 2c , [1-(CMe CHCH 2 CH 2 CH 3 )–1′-(CMe NNH-2,4-(NO 2 ) 2 C 6 H 3 )] ( 2c ′), has been crystallographically characterised. Interaction of 1 with Co 2 (CO) 8 smoothly generates the alkyne-bridged complexes [Fc-1-R 1 -1′-{Co 2 (CO) 6 -μ-η 2 -CR(OH)C CCH 2 OH}] (R 1  = R = H ( 4a ); R 1  = H, R = Me( 4b ); R 1  = CMe(O), R = Me ( 4c )) in good yield. Reaction of 4a with PhSH, in the presence of catalytic quantities of HBF 4  · OEt 2 , gives the mono- [Fc-1-H-1′-{Co 2 (CO) 6 -μ-η 2 –CH(SPh)C CCH 2 OH}] ( 5 ) and bis-substituted [Fc-1-H-1′-{Co 2 (CO) 6 -μ-η 2 -CH(SPh)C CCH 2 SPh}] ( 6 ) straight chain species, while with HS(CH 2 ) n SH ( n  = 2,3) the eight- and nine-membered dithiomacrocylic complexes [Fc-1-H-1′-{ cyclo -Co 2 (CO) 6 -μ-η 2 -CH(S(CH 2 ) n –)C CCH 2 S–}] [ n  = 2 ( 7a ), n  = 3 ( 7b )] are afforded. By contrast, during attempted macrocyclic formation using 4b and HSCH 2 CH 2 OCH 2 CH 2 SH dehydration occurs to give [Fc-1-H-1′-{Co 2 (CO) 6 -μ-η 2 -C( CH 2 )C CCH 2 OH}] ( 8 ). Single crystal X-ray diffraction studies have been reported on 2c ′, 4b , 4c , 7b and 8 .