title: Sequential construction of one, two, or three dithiolene ligands from alkynes and sulfur in dinuclear cyclopentadienyl molybdenum complexes.
abstract: This paper describes the sequential assembly of up to three dithiolene ligands from alkynes and elemental sulfur at a dimetal center. The dimolybdenum mu-alkyne complexes [Mo(2)(mu-R(1)C[triple bond]CR(2))(CO)(4)Cp(2)] (1a-c; Cp = eta-C(5)H(5), R(1) = R(2) = H, CO(2)Me; R(1) = H, R(2) = CO(2)Me) undergo oxidative decarbonylation on reaction with elemental sulfur in refluxing toluene to give good to excellent yields of the terminal dithiolene complexes [Mo(2)(S)(mu-S)(2)(SCR(1)=CR(2)S)Cp(2)] (2a-c). Further reaction of these complexes with 1 equiv of an alkyne R(3)C[triple bond]CR(4) (R(3) = R(4) = H, CO(2)Me; R(3) = H, R(4) = CO(2)Me) followed by oxidation with elemental sulfur produces the bis(dithiolene) complexes [Mo(2)(mu-S)(2)(SCR(1)=CR(2)S)(SCR(3)=CR(4)S)Cp(2)] (4a-d). Two examples, [Mo(2)(mu-S)(2)(S(2)C(2)H(2))(2)Cp(2)] and [Mo(2)(mu-S)(2){S(2)C(2)(CO(2)Me)(2)}(2)Cp(2)], have been structurally characterized. Reaction of 2 with an excess of an activated alkyne R(5)C[triple bond]CR(6) (R(5) = R(6) = CO(2)Me) and sulfur, or of 4 with the alkyne alone, affords good yields of the tris(dithiolene) complexes [Mo(2)(SCR(1)=CR(2)S)(SCR(3)=CR(4)S)(SCR(5)=CR(6)S)Cp(2)] (6a-e). The degree of control over the substituents in these complexes is demonstrated by the synthesis of [Mo(2)(S(2)C(2)H(2)){mu-S(2)C(2)(CO(2)Me)(2)}{mu-S(2)C(2)(CO(2)Et)(2)}Cp(2)] (6e), which contains three different dithiolene ligands, as a single isomer.
authors.affiliation: Department of Chemistry, University of Sheffield, Sheffield S3 7HF, UK.
authors.forename: Harry
authors.initials: H
authors.lastname: Adams
authors.forename: Matthew N
authors.initials: MN
authors.lastname: Bancroft
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Morris
authors.forename: Andrea E
authors.initials: AE
authors.lastname: Riddiough