Diiminepyridine‐Supported Phosphorus(I) and Phosphorus(III) Complexes: Synthesis, Characterization, and Electrochemistry

Abstract

Diiminepyridines (DIP) are popular redox “non‐innocent” ligands with widespread application in late, first‐row transition metal mediated catalysis and coordination chemistry. Here, we report the isolation and characterization of a pair of phosphorus coordination complexes in the +1 and +3 oxidation states supported by the same ligand framework bearing sterically imposing and electron‐releasing tBu substituents on the imine carbons of the DIP backbone. Electrochemical analysis demonstrates that the DIP scaffold can retain its ability to serve as an electron reservoir when coordinated to a reduced pnictogen centre, with a reversible reduction observed for the PI complex.

Investigating the Reactions of BiCl3, a Diiminopyridine Ligand, and Trimethylsilyl Trifluoromethanesulfonate

“…The magnitude of the shifts of the methine and pyridine protons are directly correlated to the charge of the complex ( 3 > 2 > 1 ). The 19 F NMR spectra of all three products display resonances at −79.2 ppm, which correspond to ionic triflate in solution (−78.3 to −79.2 ppm ionic triflate versus covalent triflate CH 3 OTf = −76.3 ppm). , The supported ionic nature in the solution is consistent with other known bismuth, antimony, and arsenic ionic complexes, with triflates bearing similar 19 F NMR shifts (−78.3 to −79.1 ppm) and weak interactions in the solid state attributed to electrostatic interactions . Attempts to access a tris­(triflato) complex by adding 3 equivalents resulted in the formation of 3 by 1 H NMR spectroscopy with unreacted TMSOTf (Figures S26–S28).…”

Recent developments in the chemistry of non-trigonal pnictogen pincer compounds: from bonding to catalysis

“…A recent report proposes the possible isolation of a formal P(0) species upon reduction of a pyridyl-diime ligated phosphorus complex which exhibits a reversible reduction in the cyclovoltammogram. 62…”

When is a pyridine not a pyridine? Benzannulated N-heterocyclic ligands in molecular materials chemistry

“…14 The vacant, localized C=N * orbitals of imine-based ligands like PDIs can be exploited to access ligand-centred redox in transition metal 15 and main-group complexes. 16 For example, (PDI)Fe(L) (L = N 2 , NH 3 ) complexes contain ligand-centered triplet PDI diradical dianions antiferromagnetically coupled to ferrous iron centres, not neutral closed-shell singlet PDIs bound to Fe(0). 17 PDI ligands can thus serve as 'electron reservoirs', storing reducing equivalents which may then be used profitably in chemical reactions.…”