Direct phosphorylation in the synthesis of new bis(phosphorylamino)pyridine ligands

Unexpected reactivity of a PONNOP ‘expanded pincer’ ligand

“…1) revealed a nearly flat dinucleating phosphinite ligand bound to a diamond-shaped Cu 2 Cl 2 core. The structure is similar to the previously reported 141 and +P2-Cu2-N2 = 83.00 (14)1) that are smaller by B31 (see Tables S3-S5, ESI † for more detail).…”

Synthesis of an expanded pincer ligand and its bimetallic coinage metal complexes

“…PCl(tBu)2, [AuCl(SMe2)], CuI, CuCl, AgCl and AgPF6 were used as purchased from Sigma-Aldrich without further purification. 2,7-Dihydroxy-1,8-naphthyridine 54 and Ag[BAr F 4] 55,56 were synthesised following literature procedures. The numbering scheme employed for all complexes is provided in the ESI.…”

Unexpected Reactivity of a PONNOP ‘Expanded Pincer’ Ligand

“…The use of well-defined bimetallic complexes wherein two metal atoms are bound in close proximity is an emerging area in homogeneous catalysis. 1 The cooperative activation of substrate molecules by two metal centers in such bimetallic systems can enable distinct reactivity or improved catalytic performance when compared to monometallic analogues. 2 The design and exploration of new dinucleating ligands that enable such metal-metal cooperativity is key to further explore the potential of bimetallic catalysis.…”

“…This is likely an inorganic potassium salt that is formed in the reaction and was found not to affect subsequent reactions. However, to be able to proper balance reaction stoichiometry a spectroscopic purity (74 wt%) was determined by 1 H NMR analysis ( Fig. S1) using 1,4-dimethoxybenzene as an internal standard.…”

“…The first two steps comprise the synthesis of 2,7-dihydroxy-1,8-naphthyridine according to a modified literature procedure. 14 Subsequent phosphorylation was achieved by a reaction with a slight excess of chlorodiisopropylphosphine in the presence of excess Et3N in THF at 65 o C (Scheme 2) affording i-Pr PONNOP as a brown oil in 82% yield and 90% purity after workup. Several attempts to further enhance the purity solely resulted further decrease in purity due to the facile hydrolysis of the P-O bonds in the expanded pincer ligand (see ESI for more detail).…”