Page 166 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry

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824 Inorganic Exotic Molecules

+
such as C 2 H 4 Ag , simple carbo-cations such as the ketones. Or we may have halogen, oxygen, nitrogen-
•
+
hydrogen-bridged, nonclassical ethyl cation, [C 2 H 5 ] ion, forming acyl halides, carboxylic acids and their esters and
+
and to more normal solute/solvent complexes such as Li • anhydrides, and amides. There are some unusual features
(H 2 O) n with n ranging from 1 to “∞” (i.e., from a “super- of these species and some are indeed exotic, but, alas, they
simple” ion–molecule cluster to infinitely dilute aqueous are organic. Or the groups may be metals and so we have
solutions). It is related also to the corresponding propy- a special type of carbonyl compound—the same term, but
lene (methylethylene) complex by a simple substitution with a different meaning, since a metal attached to CO and
+
process, CH 3 CH CH 2 Li . None of this is particularly nothing more is even a generally classical type of carbonyl
•
surprising. However, this last ion is the product of the compound, to the inorganic chemist. If the group is a main
gas-phase reaction of Li and isopropyl chloride, group metal, then there is novelty. For example, Li 2 CO
+
has the carbon and oxygen of the CO bridged by the two
Li + (CH 3 ) 2 CHCl → CH 3 CH CH 2 •Li + HCl. (5)
+
+
metal atoms, a quite unusual geometry even for those ac-
customed to the variety of structures and bonding types of
This is reminiscent of the really quite ancient organic
metal carbonyls. Introduction of valence isoelectronic sil-
chemistry elimination reaction of an alkyl halide using
icon, sulfur, and other elements of the second row and be-
a strong base (i.e., some alkali metal hydroxide) but now
yond into the discussion generates the exotic blue/purple
employing the metal half of the latter reagent.
disilylketones (R 3 Si) 2 CO, monomeric silanones R 2 Si O,
the blue thioketones R 2 C S, and a plethora of doubly

B. “Squashing” Ethylene to Imines, modified compounds of the type R 2 E E such as ger-
En Route to Cages maselones with quite obviously the third row Ge and Se.
We note that many of these modified species energetically
Another set of interrelations arises when we take the hy-
“prefer” to be polymers and that is their natural form to
drogens of ethylene and squash them in the carbon nuclei.
the laboratory scientist and layperson alike (e.g., silicone
We first produce CH 2 NH, known as either methylen-
polymers). Then again, formaldehyde itself forms a poly-
imine or formaldimine. This species is unknown in the
mer in an exothermic reaction, despite its rich chemistry
condensed phase but is known in the gas phase and as an
as a monomeric tetratomic molecule.
interstellar molecule. It is the archetype of a large number
of organic compounds. Although this is more within the
province of organic than inorganic compounds, we note D. Azo Compounds, Isodiazenes,
how the reaction and Peroxynitirites
CH 2 O + NH 3 → CH 2 NH + H 2 O (6) The alternative squashing yields N 2 H 2 , alternatively
known as diimide and diazene, with natural derivatives
does not proceed as written but instead goes on to R N N R . Well known to the organic chemist, this is

form the tetraazaadamantane cage product hexamethy- the archetype of generally red, orange, or yellow azo com-
lene tetramine (CH 2 ) 6 N 4 . Admittedly “organic,” this pounds. Paralleling the above is the blue R 3 SiNNSiR 3 ,a
species presages σ-bonded, electron-precise inorganic rather rare variety of dinitrogen complexes en route to
cage species such as phosphorus and arsenic oxides and reduction and cleavage, and analogues such as the rare
sulfides. Recall such common species as phosphorus pen- RP NR (as opposed to common R 3 PNR species). We

toxide P 4 O 10 —we note that the formula of this species is also recall N 2 F 2 and hyponitrite salts [N 2 O 2 ] . These are
2−
often written P 2 O 5 , which is the correct formula for an al- seemingly normal, albeit unstable species. However, they
together different and much more exotic species with the have the surprising feature that the cis or Z isomer is more
structure (O ) 2 P O P( O) 2 . thermodynamically stable than the trans or E form, de-
spite greater lone-pair, charge, and/or dipolar repulsion in
the former. We should also not forget the isomeric species
C. Carbonyl Compounds—To the Organic
and Inorganic Chemist with the general formula RR N N, and while many are
transient intermediates either forming dinitrogen or trap-
Squashing results in a choice of two compounds and ping it, there are also isolable isodiazene complexes con-
derivatives. The first is CH 2 O, known as formaldehyde taining such species as ligands. And, being fond of iso-
or methanal. No surprises here with this organic molecule. electronic analogues, we note that (O − ) 2 N + O is more
Again, we recognize this species as the archetype of a stable than its counterpart O − N O + O , where we rec-
−
large variety of compounds, RR CO, so-called carbonyl ognize these last two species respectively to be the ancient

compounds to the organic chemist. Some R and R are nitrate ion and (an unimportant resonance structure of) the
hydrogen, alkyl, or aryl groups—these are aldehydes and increasingly important, but still exotic, peroxynitrite ion.