Thiosemicarbazone platinacycles with tertiary phosphines. Preparation of novel heterodinuclear platinum–tungsten complexes

Treatment of thiosemicarbazones (R1C6H4)C(H)NN(H)C(S)NHR2 [R1,R2: 4-Me,H (a); 4-Me,Me (b); 4-Me,Et (c); 2-Me,H (d); 2-Me,Me (e); 2-Me,Et (f)] with cis-[PtMe2(cod)] afforded the tetranuclear platinum(II) compounds [Pt{(R1C6H3)C(H)NNC(S)NHR2}]4 (1a–1f) with the ligand as terdentate [C,N,S] after C–H activation and NH deprotonation. The reaction of 1a–1f with PPh3 in 1:4 M ratio gave the mononuclear compounds [Pt{(R1C6H3)C(H)NNC(S)NHR2}(PPh3)] (2a–2f). Treatment of 1a–1f with large-bite diphosphines Ph2P(CH2)nPPh2 (n = 2, dppe; n = 3, dppp; n = 4, dppb) afforded the dinuclear compounds [{Pt[(R1C6H3)C(H)N–N = C(S)NHR2]}2{μ-Ph2P(CH2)nPPh2}], (3a–3f, 4a–4f, 5a–5f), with the diphosphine in a bridging mode. Similar reactions with the short-bite diphosphines Ph2PCH2PPh2 (dppm) and Ph2PC(CH2)PPh2 (vdpp) yielded the mononuclear compounds [Pt{(R1C6H3)C(H)NNC(S)NHR2}(Ph2PR3PPh2-P)] (R3 = CH2, 6a–6f; R3 = C = CH2, 7a–7f) with the diphosphine in a monodentate coordination. Treatment of 1a–1f with [W(CO)5(Ph2CH2PPh2)] gave the heterodinuclear species [{Pt[(R1C6H3)C(H)NNC(S)NHR2]}{Ph2CH2PPh2W(CO)5}] (8a–8f). The molecular structures of compounds 3e and 5c have been determined by X-ray crystal structure analysis.

The preparation of tetranuclear thiosemicarbazone platinum(II) complexes, as well as the ensuing phosphine derivatives has been achieved. The complexes with monocoordinated diphosphines are starting materials for novel platinum–tungsten species.Figure optionsDownload as PowerPoint slideHighlights
► Tetranuclear cyclometallated thiosemicarbazone platinum compounds.
► Platinacycles with bridging and monocoordinated tertiary diphosphines.
► New heterodinuclear platinum/tungsten complexes.