C−C, C−S, and C−N Coupling versus Dealkylation Processes in the Cationic Tris(thiolato)dimolybdenum(III) Complexes [Mo₂Cp₂(μ-SMe)₃L₂]⁺ (L = xylNC, t-BuNC, CO, MeCN)

Abstract

Reductive coupling between isocyanide ligands attached to adjacent molybdenum atoms in the bis(aryl isocyanide) complex [Mo2Cp2(μ-SMe)3(xylNC)2](BF4) (1) was initiated by addition of the hydrosulfide anion (HS−) to 1 under reflux in tetrahydrofuran, affording, in nearly quantitative yields, the dimetallaimidoyl(amino)carbene derivative [Mo2Cp2(μ-SMe)3{μ-η1(C):η1(C)-C(NHxyl)C(Nxyl)}] (7), in which both isocyanide groups of 1 are now linked by a new C−C bond. When the previous reaction was conducted in the presence of a large excess of hydrosulfide (20 equiv), under similar experimental conditions, the dithiocarbonimidate compound [Mo2Cp2(μ-SMe)2(μ-S2CNxyl)] (8) was obtained in quantitative yields. This product results from subsequent thiolate exchange and substitution reactions to afford a quadruply sulfur bridged intermediate, followed by free isonitrile addition to sulfido S atoms. Treatment of the coupled isocyanide derivative 7 with HBF4 led exclusively to the formation of the starting complex 1 by reversible isocyanide ligand decoupling. The heating of a tetrahydrofuran solution of 1 with the base NaCCH gave, in high yields, the μ-alkylidyne and μ-acetylide product [Mo2Cp(μ-SMe)2{μ-(η5-C5H4)(xylN)CN(xyl)C}(μ-CCH)] (9), in which a deprotonated Cp and both isocyanide ligands of 1 are now linked by new C−C and C−N bonds, and in addition an acetylide has replaced a thiolate ligand of 5. Reaction of the μ-alkylidyne complex [Mo2Cp(μ-SMe)3{μ-(η5-C5H4)(xylN)CN(xyl)C}] (5) with NaCCH under reflux in tetrahydrofuran produced, in high yields, the μ-alkylidyne and bis(μ-acetylide) cationic compound [Mo2Cp(μ-SMe)2{μ-(η5-C5H4)(xylN)CN(xyl)C}(μ-CCH)2]Br (10), in which two xylNC ligands have replaced a thiolate group of 5. Further reactions of the bis(μ-isocyanide) complex 10 with NaOH (suspension), on the one hand, and HBF4, on the other hand, under reflux in tetrahydrofuran or at room temperature in dichloromethane, respectively, led to the formation in high yields of the known mixed μ-alkylidyne and μ-amino-oxycarbene species [Mo2Cp(μ-SMe)2{μ-(η5-C5H4)(xylN)CN(xyl)C}{μ-η1(O):η1(C)-OCNHxyl}] (12) and the new tetrakis(isocyanide) dicationic derivative [Mo2Cp2(μ-SMe)2(xylNC)4](BF4)2 (11), respectively. The latter complex results from successive protonation at one carbon atom of the cyclopentadienyl ligand linked with isocyanides of 10 and decoupling between deprotonated Cp and isocyanide ligands. The heating of a tetrahydrofuran solution of a mixture of the bis(alkyl isocyanide) complex [Mo2Cp2(μ-SMe)3(t-BuNC)2](BF4) (2) and NaSH proceeded exclusively through the dealkylation of one tert-butyl isocyanide ligand to afford the known product [Mo2Cp2(μ-SMe)3(t-BuNC)](CN)] (13). Similar reaction of the dicarbonyl derivative [Mo2Cp2(μ-SMe)3(CO)2]Cl (3) with NaSH proceeded through dealkylation of one thiolate group to yield the new neutral sulfido species [Mo2Cp2(μ-SMe)2(μ-S)(CO)2] (14). Further heating of 14 in dichloromethane led to the formation of the chloromethanethiolate derivative [Mo2Cp2(μ-SMe)2(μ-SCH2Cl)(CO)2]Cl (15)...

Constructing Organometallic Architectures from Aminoalkylidyne Diiron Complexes

“…Analogous bis‐aminoalkylidyne species were also reported in the past . On the other hand, stable polynuclear compounds with bridging aminoalkylidyne ligands are relatively rare in the literature, based on molybdenum, nickel, tungsten, platinum, iron and heterodinuclear systems, and their chemistry has been sparingly developed.…”

Bond Forming Reactions Involving Isocyanides at Diiron Complexes

“…Reductive coupling of two isocyanide ligands is a long-known reaction [88], and examples include a number of mononuclear isocyanide complexes of group 4 [89], group 5 [88,90,91] and group 6 [92] transition metals. Coupling of isocyanide ligands involving dinuclear complexes is far less common [93][94][95]. Thus, the CNR coupling shown in Scheme 12 has a distinctive character for two reasons: It involves a diiron complex, which is rather uncommon [96], and it provides an example of isocyanide coupling taking place via C-N bond formation, which is rarely observed [62,95], with respect to the predominant C-C coupling mode.…”

The Coordination Chemistry of Imidomethanedithiolate Di-anions: A Structural Comparison with Their Dithiocarbamate Analogs

“…Mo separation is 2.86 Å. The second molybdenum complex is also di-nuclear, but it is organometallic: [CpMo(SMe)] 2 [S 2 C=N(2,6-Me 2 C 6 H 3 )] (2) [28]. The two molybdenum centers are bridged by a pair of µ 2 -methylthiolate ligands, and each is also bound by a Cp ligand (Figure 2b).…”

“…There are five structures in this category, all containing gold. There is one example of a dinuclear gold(I) complex (i.e., in the salt [Ph 3 P=N=PPh 3 ] 2 {Au[S 2 C=N(CN)]} 2 (28) [20]). The di-anion in 28 (Figure 7a) is a centrosymmetric dimer in which a pair of gold atoms are symmetrically µ 2 -bridged by two cyanodithiocarbimate ligands (Au-S: 2 × 2.28 Å); an intramolecular aurophilic (Au•••Au = 2.81 Å) is noted.…”