SYNTHESIS AND COORDINATION CHEMISTRY OF DICOBALT-COMPLEXED THIACYCLOALKYNES

The reactions of bis(2-mercaptoethyl) sulfide or bis(2-mercaptoethyl) ether with (Co2(mu-HOCH2C= CCH2OH)(CO)6] in the presence of HBF4.OEt2 afford (Co2{mu-C2(CH2SCH2CH2)2X}(CO)6] (X = S or O) respectively together with dimeric products. The structure of the monomer [Co2Pmu-C2(CH2SCH2CH2)2S}-(CO)6] has been established by X-ray crystallography and comprises a hexacarbonyldicobalt unit transversely bridged via the alkyne functionality of 1,4,7-trithiacycloundec-9-yne which has an exodentate conformation. Proton NMR studies of the bis(2-mercaptoethyl) sulfide derivatives reveal that the SCHCH2S linkages are predominantly anti in solution. The monomers undergo carbonyl substitution by bis(diphenylphosphino)methane (dppm) to afford [Co2{mu-C2(CH2SCH2CH2)2X}(mu-dppm)(CO)4] (X = S or O) which react with [Mo(CO)3(eta-C6H3Me3-1,3,5)] to afford products in which the macrocycles face cap Mo(CO)3 fragments. Reaction of [Co2{mu-C2(CH2SCH2CH2)2S}(CO)6] with AgBF4 and PPh3 yields [Co2{mu-C2(CH2SCH2CH2)2S)(CO)6{Ag(PPh3)}]BF4 for which an X-ray crystallographic study revealed that the Ag(PPh3)+ fragment is co-ordinated by all three sulfur atoms of the ring which adopts an endodentate conformation. Reaction of [Co2{mu-C2(CH2SCH2CH2)2S}(CO)6] with [Cu(MeCN)4]PF, affords [Co2{mu-C2(CH2SCH2CH2)2S)(CO)6{Cu(MeCN)}]PF6 containing a labile acetonitrile ligand which undergoes substitution by phosphines. The dimeric compound [(OC)6Co2{mu-(CCH2SCH2-CH2SCH2CH2SCH2C)2}Co2(CO)6] produces a 1:1 adduct when treated with AgBF4. X-Ray crystallography reveals that the silver ion is co-ordinated by four of the six available thioether groups.