Nature of PO Bonds in Phosphates

Abstract

Making use of a combination of ab initio calculated geometries, orbital energies, and orbital spatial distributions as well as experimental information about bond lengths, bond energies, vibrational frequencies, and dipole moments, the nature of the terminal PO bond in phosphates such as (MeO) 3 PO was probed and compared to the case in MeOsPdO where P is trivalent and a PO π bond is thus assumed to exist. We find that the MeOsP and terminal PO bond lengths in (MeO) 3 PO are essentially the same as in MeOsPdO and the terminal PO lengths are substantially shorter than single PsOMe bond lengths. We also find that the HOMO orbital energies in the two compounds are within 0.1 eV of one another and that these orbitals have spatial characteristics much like one would expect of a bonding π orbital connecting two atoms from different rows of the periodic table. Using this data, making a comparison to the more familiar bonding arising in N 2 , CO, and BF, and taking note of the dipole moments in compounds known to possess dative bonds, we conclude that it is best to represent the terminal PO bond in phosphates in terms of valence-bond structures such as (MeO) 3 PdO in which the formal charges are P 0 O 0 and where a single PO π bond exists. However, when it comes to characterizing the PO antibonding π* orbitals, significant differences arise. Electronic structure methods were able to identify the π* orbital of MeOsPdO and to determine its energy (the MeOsPdO -anion is even bound). Similar attempts to identify the PO π* orbital in the unbound (MeO) 3 PdO -anion lead us to conclude that this anion state is probably so strongly coupled to the continuum (i.e., to states corresponding to (MeO) 3 PdO plus a free electron) that it is so short lived as to be undetectable in experiments.

Tuning structural, electronic, and magnetic properties of black-AsP monolayer by adatom adsorptions: A first principles study

“…The bond length is much shorter than the sum of the P (1.07Å) and O (0.66Å) covalent radii [48], which indicates a P=O double bond. Furthermore, the bond length in O−AsP system is in good agreement with the P=O double bond length of 1.51Å in phosphoric acid [49]. Judging from the number of bonding atoms, the adsorption energies are supposed to follow the order of C>N>O.…”

Potential Dependent Structure and Stability of Cu(111) in Neutral Phosphate Electrolyte

“…The in situ X-ray structural analysis of the Cu(111) surface at −0.5 V gave an oxygen coverage θ O = 0.6. It is known that phosphate species have a tetrahedral structure with a P-O bond length of the order d P-O~1 .5-1.6 Å, thus the corresponding O-O distance is d O-O~2 .44-2.62 Å [26][27][28]. The atomic distance of the copper atoms at the Cu(111) surface is 2.556 Å, which is similar to the O-O distance in the phosphate, thus making the adsorption of phosphate or hydrogen phosphate with three oxygen atoms sitting in the same adsorption site likely.…”

Polyphosphate: A Morphogenetically Active Implant Material Serving as Metabolic Fuel for Bone Regeneration

“…The diameter of a ortho‐phosphate unit is about 3 Å, implying that the maximal chain length of polyP 40 , used for our studies is approximately 12 nm. Certainly, the polyP chains, due to their properties of free rotating of the phosphate units, exist in solution as coiled bundles, especially in complex with the counterion Na + .…”

“…Those soft scaffolds might be suitable to repair smaller bone defect, e.g., during the process of distraction osteogenesis. [184] The diameter of a ortho-phosphate unit is about 3 Å, [185] implying that the maximal chain length of polyP 40 , used for our studies is approximately 12 nm. Certainly, the polyP Figure 5.…”