SYNTHESIS AND COORDINATION CHEMISTRY OF DICOBALT-COMPLEXED ACETYLENIC CROWN-ETHERS

Reactions of [Co2(mu-HOCHRC=CCHROH)(mu-dppm) (CO)4] (R = H or Me, dppm = Ph2PCH2PPh2) with HO(CH2)(n)OH (n = 4-6) in the presence of HBF4.OEt2 afforded the Co2(mu-dppm)(CO)4-complexed tetraoxacyclodiynes [(OC)4(mu-dppm)Co2{mu-CCHRO(CH2)(n)OCHRC}2Co2(mu-dppm)(CO)4]. The dimeric nature of the products was confirmed by fast atom bombardment mass spectroscopy and the crystal structure of [(OC)4(mu-dppm)Co2{mu-CCH2O(CH2)4OCH2C}2Co2(mu-dppm)(CO)4]. The acid-catalysed reaction of [Co2(mu-HOCH2C=CCH2OH)(mu-dppm)(CO)4] with triethylene glycol and a NaBF4 template afforded [Co2{mu-CCH2O[(CH2)2O]3CH2C}(mu-dppm)(CO)4] which can co-ordinate Li+. The analogous reaction with tetraethylene glycol afforded [Co2Na{mu-CCH2O[(CH2)2O]4CH2C}(mu-dppm)(CO)4]BF4, in which the sodium template remains co-ordinated by the crown ether. Washing with deionised water removes the Na+ ion to produce [CO2{mu-CCH2O[(CH2)2O]4CH2C}(mu-dppm)(CO)4] which forms complexes with LiBF4 and KSCN.