1,3-dipolar cycloaddition to the Fe-S=C fragment 20. Preparation and properties of carbonyliron complexes of di-thiooxamide. Reactivity of the mononuclear (di-thiooxamide)Fe(CO)(3) towards dimethyl acetylenedicarboxylate

摘要

Reaction of Fe-2(CO)(9) at room temperature in THF with the di-thiooxamides (L), S=C N(R,R)-C{(R,R')N)=S [R =Me, R'-R'= (CH2)(2) (a); R = H, R' = Pr-i (b); R = H, R' = iPr (c), R = H, R'= benzyl (d); R = H, R'= 11 (e)], results for ligands a-d initially in the formation of the mononuclear sigma-S, sigma-S' chelate complexes Fe(CO)(3)(L) (7a-d), which could be isolated in case of 7a and 7d. Under the reaction conditions, complexes 7a-d react further with [Fe(CO),] fragments to give three types of Fe,(CO)6(L) complexes (8a-d) in high yields, depending on the di-thiooxamide ligand used together with traces of the known Complex S2Fe3(CO)(9) (14). The molecular structures of these complexes have been established by the single crystal X-ray diffraction determinations of 8a, 8b and 8d. In the reaction with ligand e the corresponding complex 7e was not detected and the well-known complexes 14 and S2Fe3(CO)(9) (15) were isolated in low yield. In situ prepared 7a reacts in a slow reaction with I equiv. of dimethyl acetylene dicarboxylate in a 1,3-dipolar cycloaddition reaction to give the stable initial ferra [2.2.1] bicyclic complex 10a in 60% yield. In complex 10a an additional Fe(CO)(4) fragment is coordinated to the sulfido sulfur atom of the cycloadded Fe-S=C fragment. When a toluene solution of 10a is heated to 50 degreesC it loses two terminal CO ligands to give the binuclear Fe-Fe bonded complex 11a in almost quantitative yield. The molecular structures of 10a and Ila have been confirmed by single crystal X-ray diffraction. Reaction of 7d at room temperature with 2 equiv. of dimethyl acetylene dicarboxylate results in the mononuclear complex 12d in 5% yield. The molecular structure of 12b has been established by single crystal X-ray diffraction and comprises a tetra dentate ligand with two ferra-sulpha cyclobutene, and a ferra-disulpha cyclopentene moiety. When the reaction is performed at 60 degreesC a low yield of 2,3,4,5-thiophene tetramethyl tertracarboxylate is obtained besides complex 12d. C 2002 Elsevier Science B.V. All rights reserved. [References: 96]