Construction of a Functionalized Selenophene‐Allylidene Ligand via Alkyne Double Action at a Diiron Complex

Abstract

The diiron µ‐vinyliminium compounds [Fe2Cp2(CO)(µ‐CO){µ‐η1:η3‐C3HC2HC1NMe(R)}]CF3SO3 (R = Me, 2a; R = Xyl = 2,6‐C6H3Me2, 2b; Cp = η5‐C5H5) reacted with grey selenium, in the presence of sodium methoxide, to give the corresponding Se‐functionalized derivatives [Fe2Cp2(CO)(µ‐CO){µ‐η1:η3‐C3HC2(Se)C1NMe(R)}], 3a–b, in ca. 50 % yields. The monoiron zwitterionic complex [FeCp(CO){SeC1(NMe2)C2HC3H}], 4, was obtained as a side‐product (31 %) of the reaction leading to 3a. The treatment of 3b with S8/NaOMe afforded the 2‐ferra‐thiophene [FeCp(CO){SC3HC2HC1NMe(Xyl)}], 5, in 49 % yield. The straightforward reactions of 3a with a two‐fold excess of dialkylacetylenedicarboxylates led to functionalized 3‐amino‐selenophenes appended to the diiron frame through a bridging allylidene ligand, [Fe2Cp2(CO)(µ‐CO){µ‐η1:η3‐C7(CO2R)C6(CO2R)C3HC2SeC5(CO2R)C4(CO2R)C1(NMe2)}] (R = Me, 6a; R = Et, 6b; R = tBu, 6c), in approximately 50 % yields. The synthesis of 6a–c is the result of two distinct modes of reactivity exhibited by the alkyne reactant in one pot, i.e. 1,3‐dipolar cycloaddition to C and Se atoms and insertion into Fe‐µ‐alkylidene. All the products were characterized by means of elemental analysis, IR and multinuclear NMR spectroscopy, and the molecular structure of 6a was elucidated by a single‐crystal X‐ray diffraction study.

Alkyne–alkenyl coupling at a diruthenium complex

“…[1][2][3] For instance, as two working hands compared to one single hand, dimetallic systems offer major opportunities to build and stabilize uncommon hydrocarbyl ligands via multisite bridging coordination. [4][5][6][7][8][9][10] Alkynes are useful and versatile reagents in this setting, and in particular the {M 2 Cp 2 (CO) x } scaffold (M = Fe, Ru; Cp = η 5 -C 5 H 5 ; x = 2, 3) is suitable to promote their coupling with a diversity of bridging coordinated carbon ligands, including carbonyl, 11,12 isocyanide, 13 thiocarbonyl, 14 alkylidyne 10,15,16 and alkylidene ligands, [17][18][19][20] usually via alkyne insertion into the metal-μ-carbon bond, but alternative modes are also possible. 21 The two metal coordination spheres are coordinatively and electronically saturated, therefore prior removal of one 2-electron ligand (usually, a carbon monoxide ligand) is needed to guarantee the initial η 2 -coordination of the alkyne to one metal centre, that is a preliminary, fundamental step along the coupling process.…”

Tetrasubstituted Selenophenes from the Stepwise Assembly of Molecular Fragments on a Diiron Frame and Final Cleavage of a Bridging Alkylidene

“…The synthesis and characterization of [ 2a – d ]­CF 3 SO 3 , 3a – c , and 4a – j are reported in the Supporting Information. Compounds [ 1 ]­CF 3 SO 3 and 3d were prepared according to published procedures. Organic reactants (TCI Europe or Merck) and [Fe 2 Cp 2 (CO) 4 ] (Strem) were commercial products of the highest purity available.…”