Synthesis and characterization of bis- and tris-carbonyl Mn(I) and Re(I) PNP pincer complexes.

Abstract

Abstract: A series of neutral bis- and cationic tris-carbonyl complexes of the types cis-[M(κ³ P,N,P-PNP)(CO)₂Y] and [M(κ³ P,N,P-PNP)(CO)₃]⁺ was prepared by reacting [M(CO)₅Y] (M = Mn, Re; Y = Cl or Br) with PNP pincer ligands derived from the 2,6-diaminopyridine, 2,6-dihydroxypyridine, and 2,6-lutidine scaffolds. With the most bulky ligand PNP^NH-tBu, the cationic square-pyramidal 16e bis-carbonyl complex [Mn(PNP^NH-tBu)(CO)₂]⁺ was obtained. In contrast, in the case of rhenium, the 18e complex [Re(PNP^NH-tBu)(CO)₃]⁺ was formed. The dissociation of CO was studied by means of DFT calculation revealing in agreement with experimental findings that CO release from [M(κ³ P,N,P-PNP)(CO)₃]⁺ is in general endergonic, while for [Mn(κ³ P,N,P-PNP^NH-tBu)(CO)₃]⁺, this process is thermodynamically favored. X-ray structures of representative complexes are provided.

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