Group 13 hydride

Group 13 hydrides are chemical compounds containing group 13-hydrogen bonds (elements of group 13: boron, aluminium, gallium, indium, thallium, and nihonium).^[1]

Trihydrides

The simplest series has the chemical formula XH₃, with X representing any of the boron family.

Compound	Chemical formula	Geometry	Model
boron trihydride hydrogen boride (borane)	BH₃
aluminium trihydride hydrogen aluminide (alumane) (alane)	AlH₃
gallium trihydride hydrogen gallide (gallane)	GaH₃
indium trihydride hydrogen indigide (indigane)	InH₃
thallium trihydride hydrogen thallide (thallane)	TlH₃
nihonium trihydride hydrogen nihonide (nihonane)	NhH₃

The great variety of boranes show a huge covalent cluster chemistry, but the heavier group 13 hydrides do not. Despite their formulae, however, they tend to form polymers. Alane(aluminum trihydride) is a strong reducing agent with octahedrally coordinated aluminium atoms. Gallane is even harder to synthesise and decomposes to gallium and hydrogen at room temperature. Indigane and thallane are too unstable to exist for any significant time when not coordinated.^[2]

Simple MH₃ group 13 hydrides have a trigonal planar molecular geometry. This is due to the sp² hybridized center and vacant p-orbital, and contrasts with the trigonal pyramidal geometry of the pnictogen hydrides which are sp³ hybridized and contain a non-bonding lone pair of electrons.

All group 13 hydrides have their hydrogen anions such as BH₄⁻ and AlH₄⁻.

Hexahydrides

This series has the chemical formula X₂H₆.

Compound	Chemical formula	Geometry	Model
Diborane	B₂H₆
Dialane	Al₂H₆
Digallane	Ga₂H₆
Diindigane	In₂H₆
Dithallane	Tl₂H₆
Dinihonane	Nh₂H₆

References

^ Downs, Anthony J.; Pulham, Colin R. (1994-01-01). "The hydrides of aluminium, gallium, indium, and thallium: a re-evaluation". Chemical Society Reviews. 23 (3): 175. doi:10.1039/cs9942300175. ISSN 1460-4744.
^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 227–33. ISBN 978-0-08-037941-8.

[1] Downs, Anthony J.; Pulham, Colin R. (1994-01-01). "The hydrides of aluminium, gallium, indium, and thallium: a re-evaluation". Chemical Society Reviews. 23 (3): 175. doi:10.1039/cs9942300175. ISSN 1460-4744.

[2] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 227–33. ISBN 978-0-08-037941-8.

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