Reactivity differences between nickel and palladium complexes bearing 1,2-diphosphino-1,2-dicarba-dodecaborane ligand

AgOTf (OTf = trifluoromethanesulfonate) shows the reactivity differences when it reacts with carborane complexes [MCl2{(PPh2)2(C2B10H10)}] (M = Ni (2), Pd (3)). The reaction of AgOTf with the palladium complex 3 affords [Pd2(μ-OTf)2{(PPh2)2(C2B9H10)}2] (4) in high yields, while corresponding reaction between the nickel complex 2 and AgOTf leads to the formation of binuclear complexes [Ni{(PPh2)2(C2B9H10)}](μ-Cl)2[Ag{(PPh2)2(C2B10H10)}] (5) and [Ag2(μ-Cl)2 {(PPh2)2 (C2B10H10)}2] (6). The carborane cage of complexes 4 and 5 were broken to form nido-carboranes. It is believed the group 10 metals themselves play an important role in opening the closo-carborane skeleton. Directly stirring [(PPh2)2(C2B10H10)] with AgOTf afforded [Ag2(μ-OTf)2{(PPh2)2(C2B10H10)}2] (7), which is also used to react with 2 and 3. The reaction between 2 and 7 gives only 4 in high yields, however, stirring the mixture of 3 and 7 affords [Pd2(μ-Cl)2{(PPh2)2(C2B9H10)}2] (8), [Pd{(PPh2)2(C2B9H10)}2] (9) and 6. All these complexes have been characterized by IR, 1H NMR, 11B NMR and elemental analyses. Complexes 2, 4–9 have also been determined by single-crystal X-ray diffraction analyses.