Synthesis of [Pt12(CO)20(dppm)2]2-and [Pt18(CO)30(dppm)3]2-Heteroleptic Chini-type Platinum Clusters by the Oxidative Oligomerization of [Pt6(CO)12(dppm)]2-

The reactions of [Pt6(CO)12]2-with CH(PPh2)2(dppm), CH2=C(PPh2)2(P^P), and Fe(C5H4PPh2)2(dppf) proceed via nonredox substitution and result in the heteroleptic Chini-type clusters [Pt6(CO)10(dppm)]2-, [Pt6(CO)10(P^P)]2-, and [Pt6(CO)10(dppf)]2-, respectively. Conversely, the reactions of [Pt6(CO)12]2-with Ph2P(CH2)4PPh2(dppb) and Ph2PC-CPPh2(dppa) can be described as redox fragmentation that afford the neutral complexes Pt(dppb)2, Pt2(CO)2(dppa)3, and Pt8(CO)6(PPh2)2(C-CPPh2)2(dppa)2. The oxidation of [Pt6(CO)10(dppm)]2-results in its oligomerization to yield the larger heteroleptic Chini-type clusters [Pt12(CO)20(dppm)2]2-, [Pt18(CO)30(dppm)3]2-, and [Pt24(CO)40(dppm)4]2-(for the latter there is only IR spectroscopic evidence). All the clusters were characterized by means of IR and31P NMR spectroscopies and electrospray ionization mass spectrometry. Moreover, the crystal structures of [NEt4]2[Pt6(CO)10(dppm)]·CH3CN, [NEt4]2[Pt12(CO)20(dppm)2]·2CH3CN·2dmf, [NEt4]2[Pt12(CO)20(dppm)2]·4dmf, [NEt4]2[Pt6(CO)10(dppf)]·2CH3CN, Pt2(CO)2(dppa)3·0.5CH3CN, Pt8(CO)6(PPh2)2(C-CPPh2)2(dppa)2·2thf, and Pt(dppb)2were determined by single-crystal diffraction (dmf = dimethylformamide; thf = tetrahydrofuran).