Chemistry:Phosphinate

From HandWiki

Phosphinates or hypophosphites are a class of phosphorus compounds conceptually based on the structure of hypophosphorous acid. IUPAC prefers the term phosphinate in all cases, however in practice hypophosphite is usually used to describe inorganic species (e.g. sodium hypophosphite), while phosphinate typically refers to organophosphorus species.

Hypophosphites

The hypophosphite ion is (H2PO2). The salts are prepared by heating white phosphorus in warm aqueous alkali e.g. Ca(OH)2:[1]

P4 + 2 Ca(OH)2 + 4 H2O → 2 Ca(H2PO2)2 + 2 H2

Hypophosphites are reducing agents:[1]

(H2PO2) + 3 OH(HPO3)2− + 2 H2O + 2 e

Hypophosphites are used in electroless nickel plating as the reducing agent to deposit for example Ni metal from Ni salts.[1] The hypophosphite ion is thermodynamically unstable, and disproportionates on heating to phosphine and phosphate salts:

2 H2PO2 → PH3 + HPO42−

Reactions

When heated, sodium hypophosphite disproportionates to PH3, Na2H2P2O5, Na2HPO3, Na4P2O7 and H2.[2]

When exposed to light ammonium hypophosphite darkens. A proposed reaction is:[3]

[H2PO2] → H + [HPO2]
[HP•O2] + [H2PO2] → H + [O2PPHO2]2−

Uses

Hypophosphite (usually sodium hypophosphite) acts as a reducing agent to deposit nickel onto surfaces without using electricity. Common in electronics, automotive, and aerospace industries for corrosion resistance and hardness. Some hypophosphite compounds are used in medicines, particularly as sources of phosphorus or as stabilizers in formulations.

In polymer and plastic stabilization, they are used today as antioxidants and thermal stabilizers to prevent degradation during the processing of plastics like PVC. Beyond nickel plating, hypophosphites are used in general chemical synthesis where a mild reducing agent is needed.

Additionally, in wood science, sodium hypophosphite in combination with other agents, such as ammonium-, nitrogen- or aluminium-containing chemicals, has been used for in solid wood and particleboard to improve the fire retarding properties.[4][5]

List

name formula system space group unit cell volume density comment ref
lithium di­hydrogenphosphate LiH2PO2 monoclinic C2/c a = 9.356 b = 5.3107 c = 6.543 β = 108.26° Z=4 308.73 1.547 [6][7]
beryllium bis(di­hydrogenphosphate) Be(H2PO2)2 tetragonal P41212 a = 5.0117 c = 20.051 Z=4 503.62 1.833 band gap 7.84 eV [8][7]
ammonium hypophosphite (NH4)H2PO2 orthorhombic Cmma a = 7.5425 b = 11.5204 c = 3.9942 Z = 4 347.07 1.589 [9]
Hydrazinium(2+) phosphinate (N2H6)(H2PO2)2 monoclinic P21/c a = 7.74 b = 6.44 c = 6.77 β = 98.1° [10]
1,3-diaminoguanidinium(1+) hypophosphite (CN5H8)H2PO2 monoclinic P21/c ?P21/m a=6.3673 b=14.5302 c=66452 β=16742° [11]
triethylammonium hypophosphite hydrate (Et3NH)(H2PO2)·H2O [12]
NaH2PO2•0.8H2O monoclinic P21/n a=11.127 b=13.572 c=12.93 β=102.98° Z=20 [13]
Mg(H2PO2)2 [14]
Mg(PO2H2)2.6H2O tetragonal I41/acd a=10.33 c=20.38 Z=8 1.60 [15]
hexa­aqua­magnesium(II) bis­(hypophosphite) [Mg(H2O)6](H2PO2)2 tetragonal P42/nmc a=7.2187 c=10.4639 Z=2 542.27 1.598 [16]
Al(H2PO2)3 [17]
Potassium hypophosphite KH2PO2 monoclinic C2/c a = 7.313 b = 7.2952 c = 7.181 β = 116.20° Z = 4 343.75 [18]
calcium hypophosphite Ca(H2PO2)2 [19]
calcium sodium hypophosphite NaCa(H2PO2)2 cubic P213 a = 9.720 918.3 1.90 [20]
Ti(H2PO2)3 trigonal R3c a=11.7484 c=9.7368 Z=6 1163.9 2.079 blue [21]
vanadium(III) hypophosphite V(H2PO2)3 monoclinic P21/n a = 11.4985 b = 11.7771 c = 11.5999 β = 99.807° 1547.89 2.11 green [22]
VO(H2PO2)·H2O monoclinic C2/c a = 12.046 b = 8.147 c = 7.548 β = 121.83° blue [23][24]
manganese hypophosphite monohydrate Mn(H2PO2)2.H2O monoclinic P21/c a = 7.8601 b = 7.4411 c = 10.7717 β = 102.859° Z=4 [25]
manganese hypophosphite monohydrate β-Mn(H2PO2)2.H2O monoclinic P21/n 12.013 b=8.100 c=12.450 β=106.28° Z=8 [26]
3-Hypophosphito)-(μ2-hypophosphito)-manganese dimethylformamide solvate [Mn(H2PO2)2]n·(DMF)0.11 hexagonal R3 a=20.53 c=8.041 [27]
[NH4][MnII(H2PO2)3(H2O)] monoclinic P21/n a=7.4412 b=15.147 c=9.3051 β=108.230° [28]
guanidinium manganese hypophosphite CN3H6 Mn(H2POO)3 monoclinic I2/m a=8.7596 b=13.2087 c=9.6956 β=89.764° [29]
guanidinium manganese hypophosphite CN3H6 Mn(H2POO)3 triclinic P1 a=9.0994 b=9.2419 c=15.8369 α=105.294° β=90.971° γ=118.618° [29]
formamidinium manganese hypophosphite CN2H5Mn(H2POO)3 monoclinic C2/c a=13.4506 b=10.2196 c=7.5274 β=103.604° [29]
imidazolium manganese hypophosphite C3H52Mn(H2POO)3 monoclinic P21/c a=9.6520 b=12.7066 c=18.4643 β=91.5450° [29]
triazolium manganese hypophosphite C2H4N3Mn(H2POO)3 monoclinic P21/c a=9.8034 b=8.5924 c=13.3120 β=98.554° [29]
dabcon-diium dimanganese hexakis(hypophosphite) C6H14N2Mn2(H2POO)6 hexagonal R3 a=9.8860 c=41.171 [29]
dabcon-diium dimanganese hexakis(hypophosphite) C6H14N2Mn2(H2POO)6 triclinic P1 a=9.8364( b=14.9329 c=16.8019 α=66.631° β=89.585° γ=89.082° [29]
bis(μ2-Phosphinato)-bis(5,10,15,20-tetraphenylporphyrinato)-di-manganese ethanol solvate monohydrate monoclinic P21/n a=13.2131 b=25.263 c=23.477 β=95.31° [30]
Bis(phosphinato)(2,2'-bipyridyl)manganese(II) C10H12N2Mn(H2PO2)2 monoclinic C2/c a=16.827 b=10.745 c=7.170 β=91.46° X=4 1.75 yellow [31]
iron(III) hypophosphite Fe(H2PO2)3 hexagonal R3 a = 11.2800 c = 9.6375 Z = 6 1061.97 2.353 [32]
hexa­aqua­cobalt(II) bis­(hypophosphite) [Co(H2O)6](H2PO2)2 tetragonal I41/acd a=10.3406 c=20.402 Z=8 2181.6 1.809 purple [33][34]
Co(H2PO2)2•0.53H2O monoclinic P112/a a=6.4722 b=5.3411 c=7.4900 γ=90.087° Z=2 layered, can intercallate with more water, or pyridine [35]
Co(H2PO2)2•2H2O
[NH4][CoII(H2PO2)3(H2O)] monoclinic P21/n a=7.367 b=14.914 c=9.205 β=108.38° [28]
CoCl(H2PO2).H2O orthorhombic Pbca a=7.416 b=13.082 c=9.483 Z=8 920 2.56 [36]
bis(μ-hypophosphito)-bis(benzene-1,2-diamine)-cobalt dichloride [Co(H2PO2)(C12N4H16)]Cl2 orthorhombic Pbcn a = 9.554 b = 9.147 c = 21.9222 Z = 2 1915.7 [37]
ortho-phenylenediamine cobalt hypophosphite chloride [Co(H2PO2)(C12N4H16)]Cl2 orthorhombic Pbcn a = 9.554 b = 9.147 c = 21.9222 Z = 2 1915.7 [38]
CoIII(NH3)5(H2PO2)(ClO4)2 [39]
NaCo(H2PO2)3 cubic P213 a = 9.256 Z=4 793.1 [40]
Hexa­aqua­nickel(II) bis­(hypophosphite) [Ni(H2O)6](H2PO2)2 monoclinic C2/c a = 10.1453 b = 10.1467 c = 10.3571 β = 92.632 Z=4 1065.05 1.851 green [33]
[NH4][NiII(H2PO2)3(H2O)] monoclinic P21/n a=7.3202 b=14.7961 c=9.1762 β=108.814° [28]
2-13,27-Di-t-butyl-3,6,9,17,20,23-hexamethyl-3,6,9,17,20,23-hexaazatricyclo[23.3.1.111,15]triaconta-1(29),11(30),12,14,25,27-

hexaene-29,30-dithiolato)-(μ2-phosphinato-O,O')-di-nickel(ii) tetraphenylborate acetonitrile solvate

[Ni2L(μ-O2PH2)]BPh4 triclinic P1 a=13.179 b=15.736 c=16.799 α=108.48° β=91.90° γ=107.61° [41]
" [Ni2L(μ-O2PH2)]ClO4 [41]
NiCl(H2PO2).H2O orthorhombic Pbca a = 7.2986 b = 13.0616 c = 9.4078 Z = 4 896.85 pale green; hypophosphite [42]
hexa­aqua­cobalt(II)/nickel(II) bis(hypophosphite) [Co0.5Ni0.5(H2O)6](H2PO2)2 tetragonal I41/acd a=10.3111 c=20.236 Z=8 2163.2 1.823 green [34]
Cu(H2PO2)2 monoclinic P21/c a = 7.2186 b = 5.3462 c = 6.2521 β = 98.835° Z = 2 T = 270 238.42 2.696 blue [43]
Cu(H2PO2)2 orthorhombic Pbca a = 5.3259 b = 6.2720 c = 14.2590 Z=4 T = 270 476.31 2.699 blue [43]
Cu(H2PO2)2 orthorhombic Pnma a = 6.6738 b = 5.4133 c = 7.1954 Z=2 T = 270 259.95 2.472 blue [43]
Zn(H2PO2)2 orthorhombic Pmma a=6.479 b=5.365 c=7.408 [44]
Zn(H2PO2)2.H2O monoclinic P21/c a=7.685 b=7.376 c=10.468 β=104.16° [44]
Ge2(H2PO2)6 trigonal R3 a=11.86 c=9.58 Z=3 2.18 colourless [45]
Chloro(phosphinato)germanium(II) GeCl(H2PO2) orthorhombic Pnam a=8.178 b=9.595 c=5.299 Z=4 2.764 [46]
Rubidium hypophosphite RbH2PO2 orthorhombic Pnma a = 7.9835 b = 6.3678 c = 7.575 Z = 4 385.12 [18]
Sr(H2PO2)2 monoclinic C2/c a = 15.655 b = 5.9436 c = 5.9177 β = 93.905° Z=4 549.4 2.631 colourless [47]
Cadmium bis­[dihydrogenphosphate(I)] Cd(H2PO2)2•H2O monoclinic C2/c a = 15.156 b = 5.4692 c = 6.5516 β=102.487 Z=4 530.22 3.036 [48][49]
Chloro(phosphinato)tin(II) SnCl(H2PO2) orthorhombic Pnam a=8.045 b=9.915 c=5.517 Z=4 3.308 [46]
Calcium hexa­kis(di­hydrogen­phosphito)­stannate(IV) Ca[Sn(H2PO2)6] hexagonal R3 a = 11.8619 c = 9.8668 Z = 3 1202.31 2.273 [50]
[Sn2(H2PO2)3]Br orthorhombic Pmn21 a=5.4177 b=7.1467 c=13.8359 Z=2 535.71 3.176 [51]
RbSb(SO4)(H2PO2)F orthorhombic Pnma a=15.1004 b=5.4481 c=8.8857 Z=4 731.01 3.519 dark [52]
Cesium hypophosphite CsH2PO2 orthorhombic Pnma a = 8.3776 b = 6.6271 c = 7.916 Z = 4 439.52 [18]
barium bis­(di­hydrogen­phos­phate) Ba(H2PO2)2 orthorhombic Ccca a = 6.2390 b = 15.584 c = 6.1726 Z=4 600.2 2.958 colourless [47]
BaSb(H2PO2)3Cl2 monoclinic P21 a=8.5451 b=7.6108 c=9.0163 β=95.680° SHG 5.0 × KDP; birefringence (0.09@546 nm); bandgap 4.2 eV [53]
La(H2PO2)3 triclinic P1 a = 6.7912 b = 7.0801 c = 8.863 α = 82.64° β = 74.43o γ = 71.91° Z=2 [54]
La(H2PO2)3•H2O triclinic P1 a = 7.2291 b = 7.983 c = 8.934 α =110.57° β = 98.26° γ = 104.35° Z=2 [54]
Ce(H2PO2)3(H2O) triclinic P1 a=7.1729 b=7.9827 c=8.871 α=110.643° β=98.101° γ=104.97° [55]
Pr(H2PO2)3 [54]
[Pr(H2PO2)(HPO3)(H2O)]·H2O orthorhombic P212121 a=6.6558 b=7.1539 c=16.5506 [55]
Nd(H2PO2)3 [54]
Dy(H2PO2)3 monoclinic C2/m a=14.368 b=5.734 c=12.123 β=122.33° [55]
Yb(H2PO2)3 monoclinic C2/m a=14.281 b =5.658 c=12.006 β=122.26° [56]
Thallous hypophosphite TlH2PO2 melt 114°C [49][57]
Pb(H2PO2)2 monoclinic C2/c a = 15.516 b = 6.008 c = 5.969 β = 93.30° Z=4 555.5 4.032 colourless [47]
U(H2PO2)4 orthorhombic Pbca a=7.467 b=13.394 c=19.904 Z=8 1990.7 3.323 green [43]
UO2(H2PO2)2·H2O monoclinic P21/n a = 7.686 b = 9.275 c = 11.027 β = 92.32° Z=4 785.4 3.535 colourless [58]
UO2(H2PO2)2·H3PO orthorhombic P212121 a = 7.1572 b = 7.2363 c = 17.554 901.0 3.435 yellow [58]

See also

References

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