(Ferrocenylpyrazolyl)palladium(II) complexes: Syntheses, characterization and rearrangement in solution

• (Ferrocenylpyrazolyl) chloromethylpalladium complexes.
• Catalysts for the copolymerisation of carbon monoxide and ethylene.
• Re-arrangement to bis(ferrocenylpyrazolyl)palladium salts.

Reactions of L1-L6 (3-ferrocenylpyrazolyle (L1), 3-ferrocenyl-5-methylpyrazolyle (L2) 3-ferrocenylpyrazolyl-methylenepyridine (L3) and 3-ferrocenyl-5-methylpyrazolylmethylene-pyridine (L4), 3-ferrocenylpyrazolylethylamine (L5) and 3-ferrocenyl-5-methylpyrazolylethyl-amine (L6)) with [PdCl(Me) (cod)] formed the mononuclear complexes [PdCl(Me) (κ1-L1)2] (1), [PdCl(Me) (κ1-L2)2] (2), [PdCl(Me) (κ2-L3)] (3), [PdCl(Me) (κ2-L4)] (4), [PdCl(Me) (κ2-L5)] (5) and [PdCl(Me) (κ2-L6)] (6). Reactions of 1–6 with the halide abstractor, Na[BAr4], (Ar = 3,5-(CF3)2C6H3), led to the formation of the salts, [PdMe(NCMe) (κ1-L1)2][BAr4] (7), [PdMe(NCMe) (κ1-L2)2][BAr4] (8), [PdMe(NCMe) (κ2-L3)][BAr4] (9), [PdMe(NCMe) (κ2-L4)][BAr4] (10), [PdMe(NCMe) (κ2-L5)][BAr4] (11), [PdMe(NCMe) (κ2-L6)][BAr4] (12) respectively. However, when 3 or 4 was reacted with of Na[BAr4] and a slight excess of methyl acrylate, the products were surprisingly the bis(ligand)palladium complexes [Pd(κ2-L3)2][BAr4]2 (13) and [Pd(κ2-L4)2][BAr4]2 (14) instead of the expected acylpalladium chelate complexes ([(κ2-L)Pd{(CH2)2C(O)OMe}][BAr4]).Complexes 1–6, activated with Na[BAr4], and pre-activated complexes 7–12 at 10 bar of ethylene and 30 bar of carbon monoxide produced polyketones, albeit with low activity (ca. 1.00 g.mmol−1Pd.h−1); with the active catalysts rearranging to mainly bis(pyrazolyl)palladium complexes similar to 13 and 14.

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