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

Treatment of thiosemicarbazones (R 1 C 6 H 4 )C(H) NN(H)C( S)NHR 2 [R 1 ,R 2 : 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 -[PtMe 2 (cod)] afforded the tetranuclear platinum(II) compounds [Pt{(R 1 C 6 H 3 )C(H) NN C(S)NHR 2 }] 4 ( 1a – 1f ) with the ligand as terdentate [ C , N , S ] after C–H activation and NH deprotonation. The reaction of 1a – 1f with PPh 3 in 1:4 M ratio gave the mononuclear compounds [Pt{(R 1 C 6 H 3 )C(H) NN C(S)NHR 2 }(PPh 3 )] ( 2a – 2f ). Treatment of 1a – 1f with large-bite diphosphines Ph 2 P(CH 2 ) n PPh 2 ( n  = 2, dppe; n  = 3, dppp; n  = 4, dppb) afforded the dinuclear compounds [{Pt[(R 1 C 6 H 3 )C(H) N–N = C(S)NHR 2 ]} 2 {μ-Ph 2 P(CH 2 ) n PPh 2 }], ( 3a – 3f , 4a – 4f , 5a – 5f ), with the diphosphine in a bridging mode. Similar reactions with the short-bite diphosphines Ph 2 PCH 2 PPh 2 (dppm) and Ph 2 PC( CH 2 )PPh 2 (vdpp) yielded the mononuclear compounds [Pt{(R 1 C 6 H 3 )C(H) NN C(S)NHR 2 }(Ph 2 PR 3 PPh 2 -P )] (R 3  = CH 2 , 6a – 6f ; R 3  = C = CH 2 , 7a – 7f ) with the diphosphine in a monodentate coordination. Treatment of 1a – 1f with [W(CO) 5 (Ph 2 CH 2 PPh 2 )] gave the heterodinuclear species [{Pt[(R 1 C 6 H 3 )C(H) NN C(S)NHR 2 ]}{Ph 2 CH 2 PPh 2 W(CO) 5 }] ( 8a – 8f ). The molecular structures of compounds 3e and 5c have been determined by X-ray crystal structure analysis.