Discrete and Polymeric Cobalt Pyrophosphates Derived from Pyrophosphoric Acid Diester Ar₂H₂P₂O₇

Abstract

While the structural elucidation and coordination chemistry of organo‐monophosphates have been well investigated, research on the simplest member of organo‐oligophosphates, viz. diorganopyrophosphates, is relatively rare due to the inherent hydrolytic instability of the ligand. Water elimination from the 2,6‐diisopropyl phenyl phosphate (dippH2) by the action of dicyclohexylcarbodiimide (DCC) results in the isolation of a diorganopyrophosphates ligand formulated as [O{P(OAr)(OH)(O)}2] (1 or pyrodippH2) (Ar = 2,6‐diisopropylphenyl). Due to the instability of 1, it has been transformed into its sodium salt [O{P(OAr)(ONa)(O)}2] (2), which has been used for further reactions to prepare cobalt pyrophosphate complexes 3–7. Reaction of 2 with anhydrous cobalt(II) chloride in the presence of N‐heterocyclic ligands results in the formation of [Co(pyrodipp)(imz)3] (3), [Co(pyrodipp)(bpy)2](CH3OH) (4) and [Co(pyrodipp)(phen)2] (5) (imz = imidazole; bpy = 2,2'‐bipyridine; phen = 1,10‐phenanthroline). Use of multidentate ancillary ligand such as 4‐pyridyl‐2,2':6',2''‐terpyridine (pyterpy) under similar reaction conditions leads to the formation of a one‐dimensional zig‐zag cobalt pyrophosphate coordination polymer [Co(pyrodipp)(pyterpy)(CH3OH)]n (6). In the absence of any ancillary ligand, the reaction between cobalt(II) chloride and 2 in acetonitrile results in the isolation of an interesting inorganic polymer [Co(pyrodipp)(CH3CN)2]n (7), whose backbone consists of a chain of spirocycles of CoP2O3 rings, joined at the cobalt centers. The newly synthesized cobalt pyrophosphates 3–7 have been characterized by both analytical and spectroscopic techniques, magnetic studies apart from single‐crystal X‐ray diffraction studies in each case. A striking and persistent structural feature in 3–7 is the presence of the cobalt pyrophosphate six‐membered metallacycle Co(OPOPO). While cobalt metal exists in trigonal bipyramidal geometry in complex 3, distorted octahedral coordination geometry is observed for cobalt centers in complexes 4–7.

Nuclearity Control in Molecular Copper Phosphates Derived from a Bulky Arylphosphate: Synthesis, Structural and Magnetic Studies

“…Subsequently, several strategies have been developed over the years to control phosphate's reactivity and structural formation. Particularly, increasing the steric bulk of the phosphorus‐acid ligands [8] and using the appropriate chelating co‐ligands such as 2,2‐bipyridine, 1,10‐phenanthroline, and terpyridine can perturb the extended structures and form discrete metallophosphates [2a,8b,9] . Meanwhile, pyrazole‐based ligands, even outside of the chelating ligand framework, are remarkably flexible ligand.…”

Unraveling Ultralong Phosphorescence in Ar2PO(H): n(O) → σ*(P-C) Transitions in Ar2PO(H) Stabilize Triplet States Better than n(P) → σ*(P-C) in Ar3P

“…Recently, phosphorus-based organic luminophores have been widely explored for optoelectronic applications owing to their unique geometry and scope for chemical modification via oxidation of the phosphorus center. − In this context, triarylphosphine oxides have enormous applications in catalysis, materials, medicines, etc. − However, the luminescence properties of these molecules are seldom reported in the literature. According to El-Sayed’s rule, the spin-forbidden intersystem crossing from S 1 → T n can be facilitated via n → π* transition in the presence of heteroatoms containing at least a lone pair of electrons .…”