inorganic chemistry

ðÞNH 35 OsIIðÞN 2 OsIIIðÞNH (^35)
hi 5 þ
! OsVIðÞNH 34 N
hi 3 þ
þ OsVðÞNH 34 N
hi 2 þ
þ2NH 3
ð 33 Þ
thermal (63,64) and photochemical (61,62) process has been pre-
viously observed. The release of ammonia (Eq. 33) occurs due to
the strong trans-effect of nitride.
In distinction to [OsVI(NH 3 ) 4 N]^3 þ, the complex [OsV(NH 3 ) 4 N]^2 þ
( 68 ) is not stable and subsequent disproportionations may lead to
product formation, as, for example,
2 OsVðÞNH 34 N
hi 2 þ
! OsVIðÞNH 34 N
hi 3 þ
þ OsIVðÞNH 34 N
hiþ
ð 34 Þ
2 OsIVðÞNH 34 N
hiþ
þ3HþþH 2 O! OsVðÞNH 34 N
hi 2 þ
þ OsIIIðÞNH 35 ðÞH 2 O
hi 3 þ ð^35 Þ
These reactions or their modifications would result in the follow-
ing overall stoichiometry:
3 NHðÞ 35 OsIIðÞN 2 OsIIIðÞNH (^35)
hi 5 þ
þ3HþþH 2 O!
5 OsVIðÞNH 34 N
hi 3 þ
þ OsIIIðÞNH 35 ðÞH 2 O
hi 3 þ
þ6NH 3
ð 36 Þ
The analytical results roughly agree with this equation.
In general, OsVN complexes are not stable( 60 – 62,68) owing to
the fact that Os(V) is strongly oxidizing and reducing ( 69 ). In
the absence of a suitable redox partner, Os(V) undergoes dispropor-
tionation to Os(VI) and Os(IV) (see above). Accordingly, it should
also be possible to intercept Os(V) by other redox agents such as
oxygen. Indeed, O 2 is apparently able to oxidize [OsV(NH 3 ) 4 N]^2 þ
to [OsVI(NH 3 ) 4 N]^3 þ. With regard to Eq. (32), oxygen takes
up the excess electron. In agreement with this assumption,
the photolysis of [(NH 3 ) 5 OsII(m-N 2 )OsIII(NH 3 ) 5 ]^5 þ yields more
[OsVI(NH 3 ) 4 N]^3 þand less [OsIII(NH 3 ) 5 (H 2 O)]^3 þin the presence of
oxygen compared to that which was performed under argon. The
amount of [OsVI(NH 3 ) 4 N]^3 þ increased by 13% when the 5þ ion
(4 10
^4 M) was photolyzed in the presence of oxygen. This comes
close to a complete conversion (17%).
In the context of these observations, the question arises
what happens when [(NH 3 ) 5 OsIII(m-N 2 )OsIII(NH 3 ) 5 ]^6 þ ( 70 ) is
PHOTOCHEMICAL ACTIVATION AND SPLITTING OF H 2 O 365