# Borate oxalate

The borate oxalates are chemical compounds containing borate and oxalate anions. Where the oxalate group is bound to the borate via oxygen, a more condensed anion is formed that balances less cations. These can be termed boro-oxalates, bis(oxalato)borates, or oxalatoborates or oxalate borates. The oxalatoborates are heterocyclic compounds with a ring containing -O-B-O-. Bis(oxalato)borates are spiro compounds with rings joined at the boron atom.
Oxalatoborates are used or for research in lithium-ion battery electrolytes and for supercapacitors.

## Production

Oxalatoborates have been produced by heating boric acid, oxalic acid and one of a metal oxalate, a metal carbonate or an amine in boiling benzene.

## Properties

When heated, oxalaotoborates decompose at around 320 °C to yield a metaborate, carbon monoxide, and carbon dioxide.

## List

| name | chemical formula | mw | crystal system | space group | unit cell Å | volume | density | comment | CAS no |
| Lithium bis(oxalate)borate, LiBOB | LiB(C$_2$O$_4$)$_2$ | 193.8 | orthorhombic | Pnma | a 6.3635 b 7.5998 c 13.1715 | | | | 244761-29-3 |
| lithium difluoro (oxalate) borate, LiDFOB | LiBF$_2$(C$_2$O$_4$) | 143.8 | orthorhombic | Cmcm | a = 6.2623, b = 11.437, c = 6.3002, Z = 4 | 451.22 | | | 409071-16-5 |
| lithium difluoro (oxalate) borate dihydrate | LiBF$_2$(C$_2$O$_4$)•2H$_2$O | | monoclinic | P21/c | a = 9.5580, b = 12.7162, c = 5.4387, β =106.247 Z = 4 | 634.63 | | | |
| ammonium bis(oxalato)borate | | | | | | | | | |
| tetramethylammonium bis(oxalato)borate | N(CH$_3$)$_4$B(C$_2$O$_4$)$_2$ | | | | | | | | |
| triethylammonium bis(oxalato)borate | | | | | | | | | |
| pyridinium bis(oxalato)borate | | | | | | | | | |
| quinolinium bis(oxalato)borate | | | | | | | | | |
| 1-ethyl-3-methylimidazolium bis(oxalate)borate (EmimBOB) | | | | | | | | ionic liquid | |
| 1-Butyl-1-Methylpyrrolidinium bis(oxalate)borate; Bmpyr BOB | (C$_4$H$_8$N$^+$)(CH$_3$)(C$_4$H$_{10}$)[B(C$_2$O$_4$)$_2$]$^−$ | | | | | | | ionic liquid | |
| | [(C$_2$H$_5$)$_4$N][CF$_3$B(OCH$_3$)(C$_2$O$_4$)] | | | | | | | | |
| | [(C$_2$H$_5$)$_4$N][CF$_3$CF$_2$B(OCH$_3$)(C$_2$O$_4$)] | | | | | | | | |
| | [(C$_2$H$_5$)$_4$N][CF$_3$BF(C$_2$O$_4$)] | | | | | | | | |
| | [(C$_2$H$_5$)$_4$N][CF$_3$CF$_2$BF(C$_2$O$_4$)] | | | | | | | | |
| sodium bis(oxalato)borate, NaBOB | NaB(C$_2$O$_4$)$_2$ | | orthorhombic | Cmcm | a 8.12756( b 10.3399 c 7.8211 | | | | |
| Trihexyltetradecylphosphonium bis(oxalate)borate | | | | | | | | | |
| | [(C$_6$H$_5$)$_4$P][CF$_3$B(OCH$_3$)(C$_2$O$_4$)] | 538.24 | triclinic | P1 | a 11.0744 b 11.5314 c 12.2196, α 73.427° β 69.395° γ 61.786° Z=2 | 1273.7 | 1.403 | | |
| | [(C$_6$H$_5$)$_4$P][CF$_3$CF$_2$B(OCH$_3$)(C$_2$O$_4$)] | | | | | | | | |
| | [(C$_6$H$_5$)$_4$P][CF$_3$BF(C$_2$O$_4$)] | | | | | | | | |
| | [(C$_6$H$_5$)$_4$P][CF$_3$CF$_2$BF(C$_2$O$_4$)] | 576.22 | monoclinic | C2/c | a 16.821 b 7.1612 c 21.519 β 101.981° Z=4 | 2535.6 | 1.509 | | |
| Lithium difluoro(oxalato)borate tetramethylene sulfone disolvate | Li$^+$•C$_2$BF$_2$O$_4$$^−$•2C$_4$H$_8$O$_2$S | | monoclinic | P2$_1$/n | a = 13.9005 b = 5.8917 c = 19.9627 β = 106.010 Z=4 | 1571.48 | 1.623 | colourless | |
| potassium boro-oxalate | K(C$_2$O$_4$)(BO$_2$)$_2$•2H$_2$O | 248.77 | triclinic | P1 | a=6.3508 b=7.0095 c=10.590 α=93.798 β=101.424 γ=100.196 | 452.3 | 1.827 | NLO 1×KDP; stable to 187 °C | |
| rubidium bis(oxalato)borate | | | | | | | | | |
| caesium bis(oxalato)borate | | | | | | | | | |
| thallium bis(oxalato)borate | | | | | | | | | |
| | Pb$_6$O$_2$(BO$_3$)$_2$(C$_2$O$_4$) | 740.39 | orthorhombic | Cmcm | a=18.0445 b=6.6225 c=11.4682 Z=8 | 1370.45 | 7.177 | band gap 3.60 eV | |