View source for It:Osmium Tetroxide

=Introduction<sup>1</sup>=

Chemical Formula: OsO<sub>4</sub>
Molar Mass: 254.23 gmol<sup>-1</sup>
Melting point: 40°C
Boiling point: 130°C
VERY TOXIC Especially to the eyes.
Colourless/Yellow
Ozonelike odour

Osmium Tetroxide is an example of the highest oxidation state achieved by transition metal. It has a tetrahedral shape as shown in jmol format below with O=Os=O bond angle of ~109°.

<jmol>
<jmolApplet>
<size>200</size>
<color>white</color>
<script>zoom 100; cpk on;frame 1; move 10 -20 10 0 0 0 0 0 3; delay 1;</script>
<inlineContents>HEADER    CSD ENTRY XICKAV
HEADER    NONAME 07-Dec-06                                              NONE   1
TITLE                                                                   NONE   2
AUTHOR    WWW daemon apache                                             NONE   3
REVDAT   1  07-Dec-06     0                                             NONE   4
ATOM      1  O           0       0.000  -1.424  -1.007  0.00  0.00           O+0
ATOM      2 Os           0      -0.000  -0.000   0.000  0.00  0.00          Os+0
ATOM      3  O           0       0.000   1.424  -1.007  0.00  0.00           O+0
ATOM      4  O           0      -1.424   0.000   1.007  0.00  0.00           O+0
ATOM      5  O           0       1.424  -0.000   1.007  0.00  0.00           O+0
CONECT    1    2    0    0    0                                         NONE  10
CONECT    2    1    3    4    5                                         NONE  11
CONECT    3    2    0    0    0                                         NONE  12
CONECT    4    2    0    0    0                                         NONE  13
CONECT    5    2    0    0    0                                         NONE  14
END                                                                     NONE  15
END</inlineContents>
</jmolApplet>
</jmol>


===Weapon of terror?===
Osmium Tetroxide has been seen as a possible terrorist weapon, this is becuase of its possible use as a catalysist in an explosive device, or due to its high toxicity. The catalytic behaviour is possible due to osmium’s many oxidation states, and the toxicity because of its acidic and corrosive nature in aqueous systems. However it's cost has had it dubbed 'the billionaires weapon'.

=Preparation<sup>1</sup>=

Addition of oxygen by burning the metal at 800 °C

[[Image:OsO4.JPG|Thumb|Left|200|Preparation]]

=Use in Organic Chemistry=

Oxidation of C=C bond<sup>1</sup>

[[Image:OsO4 oxidation.JPG|Thumb|Left|200|Reaction]]




Osmium forms several oxofluorides, all of which are very sensitive to moisture. Purple cis-OsO2F4 forms at 77 K in an aqueous solution of HF<sup>3</sup>

OsO4 + 2 KrF2 → cis-OsO2F4 + 2 Kr + O2 
OsO4 also reacts with F2 to form yellow OsOF2:

2 OsO4 + 2 F2 → 2 OsO3F2 + O2 
OsO4 reacts with one equivalent of [Me4N]F at 298 K and 2 equivalents at 253 K[4]:

OsO4 + [Me4N]F → [Me4N][OsO4F] 
OsO4 + 2 [Me4N]F → [Me4N]2[cis-OsO4F2]


==References==
1.http://www.chm.bris.ac.uk/motm/oso4/oso4v.htm

2.http://news.bbc.co.uk/1/hi/uk/3604857.stm

3.Christe et al. Osmium Tetrafluoride Dioxide, cis-OsO2F4. J. Am. Chem. Soc. 1993, 115. 11279-11284

4. http://en.wikipedia.org/wiki/Osmium_tetroxide