Wraparound ligands: addition of activated alkynes to sulfur- and thiolate-bridged dimolybdenum complexes derived from trithiocarbonates

Abstract

The complex [Mo₂(μ-S)(μ-SCH₂CH₂SCCRCR}Cp₂] 1 (R = CO₂Me, Cp = η-C₅H₅) reacted with dimethyl acetylenedicarboxylate (DMAD, RCCR, R = CO₂Me) to afford two isomeric compounds, [Mo₂(μ-SCRCRSCH₂CH₂SCCRCR}Cp₂] 3 and [Mo₂{μ-SCH₂CH₂SCCRCRCRCRS}Cp₂] 4. In the first of these the DMAD has added between the μ-S ligand and the bridging thiolate, whereas in the second it has added between the μ-S ligand and the dimetallaallyl unit. Complex 4 was successfully structurally characterised, but crystallisation of 3 led unexpectedly to the oxidation product [Mo₂{μ-SCRCRS(O)CH₂CH₂S(O)₂CCRCR}Cp₂] 5. Reaction of 1 with methyl propiolate (RCCH, R = CO₂Me) afforded [Mo₂(μ-SCHCRSCH₂CH₂SCCRCR}Cp₂] 6, a product analogous to 3, regiospecifically. The complexes [Mo₂(μ-S)(μ-SCH₂CH₂CH₂SCCRCR}Cp₂] 7 and [Mo₂(μ-S)(μ-SMe){μ-CRC(SMe)CR}Cp₂] 9 both incorporated DMAD in a similar manner to give [Mo₂(μ-SCRCRSCH₂CH₂CH₂SCCRCR}Cp₂] 8 and [Mo₂{μ-CRC(SMe)CR}(μ-SCRCRSMe)Cp₂] 10 respectively. The crystal structures of 5, 6 and 10 have also been determined.