Novel (R2PC2H4PR2)M-0-COT complexes (Na = Pd, Pt) having semiaromatic eta(2)-COT or dianionic eta(2)(1,4)-COT ligands

摘要

The complexes (R2PC2H4PR2)Pd(C2H4) (R = Pr-i, Bu-t) react with COT by displacement of the ethene ligand to afford the novel mononuclear complexes (R2PC2H4PR2)Pd(eta(2)-C8H8) (R = Pr-i (1a), tBu (1b)). The COT ligand of 1a,b is semiaromatic; i.e., it is planar with alternating C-C and C=C bonds as expected for the monoanion [C8H8](-). Treatment of 1a,b with (R2PC2H4PR2)Pd-alkene complexes generates the dinuclear derivatives {(R2PC2H4PR2)Pd}(2)(mu-eta(2),eta(2)-C8H8) (R = Pr-i (2a), Bu-t(2b)). The complexes 2a,b are labile; elimination of the COT ligand from 2a gives rise to homoleptic Pd-2(mu-d(i)ppe)(2). Reaction of (d(i)ppe)PtCl2 with (tmeda)(2)Li2COT or displacement of the alkene ligands in {(d(i)ppe)Pt}a(mu-eta(2),eta(2)-C8H12) (4) or (d(i)ppe)Pt(C2H4) (5) by COT produces (d(i)ppe)Pt(eta(2)-C8H8) (6a), which in the solid state also has a semiaromatic COT ligand. In solution, complex 6a is in equilibrium with the novel isomeric form (d(i)ppe)Pt-II{eta(2)(1,4)-C8H8} (6b). The complexes are characterized by IR, MS, and solution and solid-state NMR. [References: 49]