Thermal and Photochemical Formation of Dinuclear Molybdenadithiolene Complexes in One-Pot Reactions among[(Cp)2Mo2(CO)6], Elemental Sulfur and Dimethyl Acetylenedicarboxylate

Abstract

One-pot reaction among [(Cp)2Mo2(CO)6], elemental sulfur, and dimethyl acetylenedicarboxylate (DMAD) affords several types of dinuclear molybdenadithiolene complexes. The thermal reaction gives [(Cp)(CO)2Mo{μ-S2C2(CO2Me)2}2Mo(Cp)] (2), while the photoreaction gives mainly isomeric [(Cp)Mo(CO){μ-S2C2(CO2Me)2}2Mo(CO)(Cp)] (3). The former dicarbonylmolybdenum complex easily undergoes decarbonylation, while the latter is thermally stable.

Sequential Construction of One, Two, or Three Dithiolene Ligands from Alkynes and Sulfur in Dinuclear Cyclopentadienyl Molybdenum Complexes

“…Its 1 H NMR spectrum contained two Cp resonances and three peaks due to methyl groups in an overall ratio of 10:18. These data agreed with those in the literature: 6a is a known compound, having been previously made by Sugiyama et al by the thermal or photochemical reaction of [Mo 2 (CO) 6 Cp 2 ] with DMAD and sulfur, though the existence of a tris(dithiolene) complex of this type was first suggested by King as long ago as 1967 based on the mass spectrum of [Mo 2 (NO) 2 {S 2 C 2 (CF 3 ) 2 } 2 Cp 2 ] . As in the formation of the bis(dithiolene) complexes, an internal redox reaction has occurred with the production of the formally dianionic dithiolene ligand from two S 2− ligands, but in this case there is no reoxidation of the metal centers, which remain as Mo(IV).…”

“…As expected, one of the dithiolene ligands occupies a terminal position on Mo(2) whereas the other two adopt what we term the semibridging mode of coordination, in which one sulfur atom bridges between the two metals and the other is bound only to Mo(1). This type of bonding is well established in a number of cases, especially in dimolybdenum chemistry. ,,,− Each molybdenum thus attains a square-based pyramidal CpMoS 4 coordination sphere. The structure is thus very similar to that of one isomer of the related dicarbonyl [Mo 2 (CO) 2 {μ-S 2 C 2 (CO 2 Me) 2 } 2 Cp 2 ] but with the two CO ligands replaced by a third dithiolene.…”

“…Compounds of type 4 , like 2 , are formally Mo(V) dimers. As such it seemed possible that oxidation of the corresponding Mo(III) bridging dithiolene complex [Mo 2 {μ-S 2 C 2 (CO 2 Me) 2 } 2 Cp 2 ] , with elemental sulfur might induce the dithiolene ligands to adopt terminal coordination and thus form a viable alternative route to 4a . In practice, however, this proved rather disappointing: heating a toluene solution with an excess of sulfur for a week produced only an 11% yield of 4a .…”

“…More often, however, dithiolenes have been produced by the reaction of discrete metal sulfide (or polysulfide) complexes with activated alkynes such as dimethyl acetylenedicarboxylate (DMAD) . In some cases heating or photolysis of suitable precursor complexes with a mixture of sulfur and a large excess of the alkyne accomplishes a similar result. , Depending on the reactivity of the metal sulfide complex, reactions with less activated alkynes such as phenylacetylene and diphenylacetylene can also occur, though reactions with acetylene itself are limited to only relatively few examples such as [ReS 4 ] − and [Ru 2 (μ-S) 2 (μ-S 2 )Cp* 2 ] . The addition of acetylene itself to sulfur atoms to produce bridging dithiolene ligands in dimolybdenum complexes is also well documented in the extensive work of Rakowski Dubois and co-workers …”

A novel route to dithiolenes from 1,3-dithiole-2-thiones at a dicobalt centre

“…6 It is also clear that the µ-CS ligand is responsible for the low field signal in the 13 C NMR spectrum. The remaining portion of the organic ligand is bonded as an unsymmetrically bridging dithiolene, in which S(1) bridges the metal-metal bond whereas S( 2 7 The C(30)-C(31) bond distance in this ligand is 1.352(7) Å, which is typical for dithiolenes.…”