Metal salts of the form $\ce{(M^{+})_2[XeF8]^{2-}}$ where M is a metal salt such as $\ce{Cs, Rb}$ (see the above reference) or $\ce{Na}$ (see p. 62 in Advances in Inorganic Chemistry, Volume 46, A. G. Sykes editor; link
The $\ce{XeF8}$ portion of the molecules approximates a square-antiprism geometry.
the lowest oxide of xenon $\ce{XeO}$ is not known though O.N is +2. Why?
Perhaps the molecule is unstable, favoring disproportionation to other xenon oxides plus oxygen. For example, Andreas Hermann and Peter Schwerdtfeger suggest the following pathway at high pressure:
$\ce{3XeO → Xe3O2 + 1/2O2}$
The authors go on to note "we do not find $\ce{XeO}$ to be stable at any pressure" (link to full paper).
Edit: See orthocresol's comment below. He argues that at ambient pressure the following decomposition pathway might be more likely:
Metal salts of the form $\ce{(M^{+})_2[XeF8]^{2-}}$ where M is a metal salt such as $\ce{Cs, Rb}$ (see the above reference) or $\ce{Na}$ (see p. 62 in Advances in Inorganic Chemistry, Volume 46, A. G. Sykes editor; link
The $\ce{XeF8}$ portion of the molecules approximates a square-antiprism geometry.
the lowest oxide of xenon $\ce{XeO}$ is not known though O.N is +2. Why?
Perhaps the molecule is unstable, favoring disproportionation to other xenon oxides plus oxygen. For example, Andreas Hermann and Peter Schwerdtfeger suggest the following pathway at high pressure:
$\ce{3XeO → Xe3O2 + 1/2O2}$
The authors go on to note "we do not find $\ce{XeO}$ to be stable at any pressure" (link to full paper).
Edit: See orthocresol's comment below. He argues that at ambient pressure the following decomposition pathway might be more likely:
One more thing: The higher oxides: XeO3 and XeO4 were discovered earlier but the oxide XeO2 was discovered recently! What took it so long to discover?More
says it is prepared at 0 C and quickly decomposes to $\ce{XeO3}$ with a half-life around 2 minutes. Sounds like it may have been difficult to tell that something other than $\ce{XeO3}$ was being produced.More
At least 2 compounds have been reported that contain the $\ce{XeF8^{2-}}$ unit. See, for example:
The $\ce{XeF8}$ portion of the molecules approximates a square-antiprism geometry.
(image source)
Perhaps the molecule is unstable, favoring disproportionation to other xenon oxides plus oxygen. For example, Andreas Hermann and Peter Schwerdtfeger suggest the following pathway at high pressure:
$\ce{3XeO → Xe3O2 + 1/2O2}$
The authors go on to note "we do not find $\ce{XeO}$ to be stable at any pressure" (link to full paper).
Edit: See orthocresol's comment below. He argues that at ambient pressure the following decomposition pathway might be more likely:
$\ce{XeO -> Xe + 1/2 O2}$
At least 2 compounds have been reported that contain the $\ce{XeF8^{2-}}$ unit. See, for example:
The $\ce{XeF8}$ portion of the molecules approximates a square-antiprism geometry.
(image source)
Perhaps the molecule is unstable, favoring disproportionation to other xenon oxides plus oxygen. For example, Andreas Hermann and Peter Schwerdtfeger suggest the following pathway at high pressure:
$\ce{3XeO → Xe3O2 + 1/2O2}$
The authors go on to note "we do not find $\ce{XeO}$ to be stable at any pressure" (link to full paper).
Edit: See orthocresol's comment below. He argues that at ambient pressure the following decomposition pathway might be more likely:
$\ce{XeO -> Xe + 1/2 O2}$
More
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