Silicide hydride

A silicide hydride is a mixed anion compound that contains silicide (Si⁴⁻ or clusters) and hydride (H⁻) anions. The hydrogen is not bound to silicon in these compounds. These can be classed as interstitial hydrides, Hydrogenated zintl phases, or Zintl phase hydrides.^[1] In the related silanides, SiH₃⁻ anions or groups occur. Where hydrogen is bonded to the silicon, this is a case of anionic hydride, and where it is bonded to a more complex anion, it would be termed polyanionic hydride.^[1]

Silicide hydrides may be prepared by heating a Zintl phase or metal silicide under hydrogen pressure, of perhaps 20 atmospheres.^[2]

Properties

In CaSiD_1+x the deuterium atom (D) fits in a tetrahedral hole between three calcium and one silicon atoms. The Si-D distance is 1.82 Å, quite a bit further than then a Si-H covalent bond.^[3]

List

formula	system	space group	unit cell Å	volume	density	comment	reference
Li4Si2H	orthorhombic	Cmmm				zigzag Si chains Si-Si 2.39	[4]
CaSiH							[3]
CaSiH1+x x<1.2	orthorhombic	Pnma	a = 14.4884, b = 3.8247, c = 11.2509, Z = 3			zigzag Si chains Si-Si 2.47	[4]
CaAlSiH	trigonal		Z=1			Al-H bond semimetal	[4]
Ca2SiH2.41	amorphous		a=5.969 b=3.6146 c=6.815			reversible hydrogen storage	[4]
Ca5Si3H0.53	tetrahedral	I4/mcm	a=7.6394 c=14.7935 Z=4	863.33			[1][5]
SrSiH1.6	orthorhombic	Pnma					[6]
SrAlSiH		P3m1				Al-H bond semimetal	[4]
SrGaSiH	trigonal	P3m1	Z=1			grey; Ga-H 1.71 semimetal	[4][7]
Sr21Si2O5H21+x	cubic	Fd3m	a = 19.1190				[8]
BaSiH3.4	orthorhombic	Pnma					[6]
Ba3Si4Hx (x = 1–2)	tetrahedral	I4/mcm	a ≈ 8.44, c ≈ 11.95, Z = 8			Si46– in a butterfly-shape	[2]
Ba21Si2O5H21+x	cubic	Fd3m	a = 20.336				[8]
BaAlSiH						Al-H bond semimetal	[4]
BaGaSiH	trigonal	P3m1	a=4.2934 c=5.186 Z=1	82.79		grey; air stable; Ga-H 1.71 semimetal	[4][7]
BaGaSiD	trigonal	P3m1	a=4.2776 c=5.1948 Z=1	82.32		grey	[7]
LaFeSiH	tetragonal	P4/nmm	a=4.0270 c=8.0374				[9]
LaFeSiH	orthorhombic	Cmme	a=5.6831 b=5.7037 c=7.9728			at 15K; superconductor Tc=9.7K	[10]
La3Pd5SiD~1.6	orthorhombic	Imma	a=13.193 b=7.638 c=7.916	801.8		<9.5 bar	[11]
La3Pd5SiD~2.71	orthorhombic	Imma	a=13.102 b=7.673 c=8.168	821.3			[11]
La3Pd5SiD~5	orthorhombic	Pmnb	a=13.16 b=7.91 c=8.20	854		>75 bar	[11]
BaLaSi2D0.80	orthorhombic	Cmcm	a = 4.6443, b = 15.267, c = 6.7630				[12]
NdScSiH1.5	tetrahedral	I4/mmm	a=4.221 c=16.928 Z=4				[13]
EuSiH1.8	orthorhombic	Pnma					[6]
GdMnSiH	tetragonal	P4/nmm					[14]
GdFeSiH	tetragonal	P4/nmm	a=3.901 c=7.503	114.2			[14]
GdCoSiH	tetragonal	P4/nmm	a=3.879 c=7.439	111.9			[14]