Fragmentation reactions of realgar caused by early transition metal hydrides

The reaction of realgar with [Cp′2MH3] in boiling toluene gave [Cp′2M2As2S6] (Cp′ = t-BuC5H4; M = Nb: 1; Ta: 2), while [Cp2WH2] (Cp = C5H5) reacted with As4S4 to give [Cp2W(H)(η1-As5S2)] (6). The structures were determined by X-ray crystallography. Compounds 1 and 2 are dimers in which two Cp′M units are symmetrically bridged by a μ,η2:2-AsS3 ligand, a sulfide ligand and a heteroallylic μ,η2:2-AsS2 ligand. The structure of 6 belongs to the type of bent metallocenes in which tungsten is surrounded tetrahedrally by two Cp ligands, a crystallographically found hydride atom and the new As5S2 cage. The reaction of 1 with W(CO)5THF gave [Cp′2Nb2As2S6·W(CO)5] (3) and [Cp′2Nb2As2S6W(CO)3·W(CO)5] (4). Compound 3 is a monoadduct of 1 bearing the W(CO)5 fragment at the As atom of the AsS3 ligand. The structure of 4 contains a distorted cubane-like Nb2WS4As cluster with an integrated W(CO)3 unit. A similar cluster 5 containing a CuI fragment instead of W(CO)3 was prepared from 1 and CuI. The structure is completed by an attached As4S3 cage, the As3 basis of which is oriented towards iodide. Electrochemical investigations of 1, 3, and 4 shows for each compound quasi-reversible one-electron reductions with E1/2 = −0.73 V (1), −0.55 V (3) and −0.67 V (4), respectively.

The reaction of realgar with [Cp′2MH3] gave [Cp′2M2As2S6] (Cp′ = t-BuC5H4; M = Nb: 1; Ta: 2), while [(C5H5)2WH2] gave [(C5H5)2W(H)(η1-As5S2)] (6). The dimeric structures of 1 and 2 consist of Cp′M units and symmetrical μ,η2:2-AsS33−, S2−, and μ,η2:2-AsS2− bridges. The bent metallocene type structure of 6 contains the new As5S2− cage as a monodentate ligand. Clusters [Cp′2Nb2As2S6·W(CO)5] (3) and [Cp′2Nb2As2S6W(CO)3·W(CO)5] (4) were synthesized from 1 and W(CO)5THF.Figure optionsDownload as PowerPoint slideHighlights
► Fragmentation reactions of realgar with groups 5 and 6 metallocene hydrides.
► Formation of dimeric or trinuclear complexes containing small As/S ligands.
► Stabilization of heteroallylic μ,η2:2-AsS2 ligand and of the new As5S2− cage.
► Preparation of a heterometallic cluster with a Nb2CuS4As core.