National Institute of Standards and Technology
Computational Chemistry Comparison and Benchmark DataBase
Release 17bSeptember 2015
NIST Standard Reference Database 101
IIExperimental data
IIICalculated data
IVData comparisons
VCost comparisons
VIInput and output files
VIITutorials and Units
VIIILinks to other sites
XOlder CCCBDB versions
XIII Vibrations
XIVReaction data
XVEntropy data
XVIBibliographic data
XVIIIon data
XVIIIBad calculations
XIXIndex of properties
XXH-bond dimers

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II.A.1. (XV.A.)

Listing of experimental data for P2H4 (H2PPH2)

Other names
State Conformation
1A C2
Enthalpy of formation (Hfg), Entropy, Integrated heat capacity (0 K to 298.15 K) (HH), Heat Capacity (Cp)
Property Value Uncertainty units Reference Comment
Hfg(298.15K) enthalpy of formation     kJ mol-1 webbook
Hfg(0K) enthalpy of formation -12.54   kJ mol-1 webbook
Entropy (298.15K) entropy     J K-1 mol-1  
Integrated Heat Capacity (0 to 298.15K) integrated heat capacity     kJ mol-1  
Information can also be found for this species in the NIST Chemistry Webbook
Vibrational levels (cm-1) vibrations
Mode Number Symmetry Frequency (cm-1) Frequency Reference Intensity (km mol-1) Int. unc. Intensity Reference Comment
1 A 2296 1968Fra:1931      
2 A 2281 1968Fra:1931      
3 A 1049 1968Fra:1931      
4 A 781 1968Fra:1931      
5 A 653 1968Fra:1931      
6 A 437 1968Fra:1931      
7 A 169 1968Fra:1931      
8 B 2296 1968Fra:1931      
9 B 2281 1968Fra:1931      
10 B 1053 1968Fra:1931      
11 B 878 1968Fra:1931      
12 B 636 1968Fra:1931      

vibrational zero-point energy: 7405.0 cm-1
Calculated vibrational frequencies for P2H4 (H2PPH2).
Rotational Constants (cm-1) rotational constants
See section I.F.4 to change rotational constant units
A B C reference comment

Calculated rotational constants for P2H4 (H2PPH2).

Product of moments of inertia moments of inertia
amu3Å6   0gm3 cm6
Geometric Data
picture of H2PPH2

Point Group C2

Internal coordinates
distances (r) in Å, angles (a) in degrees, dihedrals (d) in degrees

Description Value unc. Connectivity Reference Comment
Atom 1 Atom 2 Atom 3 Atom 4
rPH 1.414   1 4 1976Hellwege(II/7) outside
rPH 1.417   1 3 1976Hellwege(II/7) inside
rPP 2.219   1 2 1976Hellwege(II/7)
aHPH 92 3 1 4 1976Hellwege(II/7)
aHPP 94.3 1 2 5 1976Hellwege(II/7) outside H
aHPP 99.1 1 2 6 1976Hellwege(II/7) inside H
dHPPH 74 3 1 2 6 1976Hellwege(II/7) Hs on different Ps
dHPPH 97.1 3 1 2 4 from HF/6-31G*, Hs on same P


Atom x (Å) y (Å) z (Å)
P1 0.0000 1.1096 -0.0080
P2 0.0000 -1.1096 -0.0080
H3 0.8420 1.3337 1.1094
H4 1.0127 1.2156 -0.9891
H5 -0.8420 -1.3337 1.1094
H6 -1.0127 -1.2156 -0.9891

Atom - Atom Distances bond lengths
Distances in Å

  P1 P2 H3 H4 H5 H6
P1   2.21911.41701.41402.81552.7193
P2 2.2191   2.81552.71931.41701.4140
H3 1.41702.8155   2.10883.15453.7871
H4 1.41402.71932.1088   3.78713.1643
H5 2.81551.41703.15453.7871   2.1088
H6 2.71931.41403.78713.16432.1088  

Calculated geometries for P2H4 (H2PPH2).

Experimental Bond Angles (degrees) from cartesians bond angles

atom1 atom2 atom3 angle         atom1 atom2 atom3 angle
P1 P2 H5 99.100 P1 P2 H6 94.300
P2 P1 H3 99.100 P2 P1 H4 94.300
H3 P1 H4 96.298 H5 P2 H6 96.298

Bond descriptions

Examples: C-C single bond, C=C, double bond, C#C triple bond, C:C aromatic bond
Bond Type Count
H-P 4
P-P 1


Atom 1 Atom 2
P1 P2
P1 H3
P1 H4
P2 H5
P2 H6
Electronic energy levels (cm-1)
Energy (cm-1) Degeneracy reference description
0 1   1A

Ionization Energies (eV)

Ionization Energy I.E. unc. vertical I.E. v.I.E. unc. reference
8.800   9.690   webbook
Dipole, Quadrupole and Polarizability
Electric dipole moment dipole
Calculated electric dipole moments for P2H4 (H2PPH2).
Electric quadrupole moment quadrupole
Calculated electric quadrupole moments for P2H4 (H2PPH2).

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squib reference DOI
1968Fra:1931 SG Frankiss "Vibrational Spectrum and Structure of Solid Diphosphine" Inorganic Chemistry 7 (9), 1931, 1968 10.1021/ic50067a051
1976Hellwege(II/7) Hellwege, KH and AM Hellwege (ed.). Landolt-Bornstein: Group II: Atomic and Molecular Physics Volume 7: Structure Data of Free Polyatomic Molecules. Springer-Verlag. Berlin. 1976.  
webbook NIST Chemistry Webbook (  

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