Proton Lability in Highly Hindered Dinuclear Palladium(I) μ-Phosphido−Secondary Phosphine Complexes. Crystal Structures of [Pd₂(μ-PBu^t₂)(PCy₂H)₃(CO)]BF₄and [Pd₂(μ-PBu^t₂)(PCy₂H)₂(μ,η²,η²-isoprene)]BF₄

The reactions of the dinuclear cationic complexes [Pd-2(mu-PBu(2)(t))(PR(3))(4)](+) (PR(3) = PCy(2)H, PMe(3)) with CO or isoprene proceed with substitution of one or two phosphine ligands giving the corresponding [Pd-2(mu-PBu(2)(t))(PR(3))(3)(CO)](+) and [Pd-2(mu-PBu(2)(t)) (mu,eta(2),eta(2)-isoprene)(PR(3))(2)](+) cations. [Pa-2(mu-PBu(2)(t))(PCy(2)H)(3)(CO)](+) equilibrates in solution to a mixture of monocarbonyl derivatives arising from bridging phosphido/terminal phosphine interchange. The complexes were characterized by multinuclear 1-D and 2-D NMR spectroscopy. The crystal and molecular structures of [Pd-2(mu-PBu(2)(t))(PCy(2)H)(3)(CO)]BF4 and [Pd-2(mu-PBu(2)(t))(PCy(2)H)(2)(mu,eta(2),eta(2)-isoprene)]CF3SO3 were solved by single-crystal X-ray diffraction studies.