New Palladium(II)−(η^3/5- or η¹-Indenyl) and Dipalladium(I)−(μ,η³-Indenyl) Complexes

Reaction of the dimeric species [(η3-Ind)Pd(μ-Cl)]2 (1) (Ind = indenyl) with NEt3 gives the complex
(η3-5-Ind)Pd(NEt3)Cl (3), whereas the analogous reactions with BnNH2 (Bn = PhCH2) or pyridine (py) afford
the complexes trans-L2Pd(η1-Ind)Cl (L = BnNH2 (4), py (5)). Similarly, the one-pot reaction of 1 with a
mixture of BnNH2 and the phosphine ligands PR3 gives the mixed-ligand, amino and phosphine species
(PR3)(BnNH2)Pd(η1-Ind)Cl (R = Cy (6a), Ph (6b)); the latter complexes can also be prepared by addition
of BnNH2 to (η3-5-Ind)Pd(PR3)Cl (R = Cy (2a), Ph (2b)). Complexes 6 undergo a gradual decomposition
in solution to generate the dinuclear PdI compounds (μ,η3-Ind)(μ-Cl)Pd2(PR3)2 (R = Cy (7a), Ph (7b)) and
the PdII compounds (BnNH2)(PR3)PdCl2 (R = Cy (8a), Ph (8b)), along with 1,1‘-biindene. The formation of
7 is proposed to proceed by a comproportionation reaction between in situ-generated PdII and Pd0
intermediates. Interestingly, the reverse of this reaction, disproportionation, also occurs spontaneously to
give 2. All new compounds have been characterized by NMR spectroscopy and, in the case of 3, 4, 5, 6a,
7a, 7b, and 8a, by X-ray crystallography.