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Anionic Structure of the So-called Ammonium Dimolybdate (NH4)2Mo2O7.

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skatem. I . I . Cofforr and 2.I I). f.aPI-rrdr. J . Amer Chem. Soc. Y I . 7000
( I96Y1.
[91 F. 5. Hovv a n d .I I%. f i i r / ~ i J. . Amer. Chem Soc. Y I . 1371 (1969).
Chem. Commun. I Y 7 0 .
[ I l l ] 1). .4.f > i ~ , i r i ~ /Ii.. C. Piriii, and 11. 1' Cirr~~irr.
1710
[ i t ] In thecase ofthecomplexes [(R2PC2H,PR2),MX,]N2H, w i t h R = a l k y l .
arkl: X = halogen.and M = Mo. W. described bq Chirit 1'1 (I/. on14 the presence
of a h)drs7ido Iigand ( - ~ N
- NH:) has so far been detected. G. 4 Hrrirli.
R . mas or^. and K . M . 7'/1oma.\. J . Amer. Chem. Soc. Y6. 259 (1974).
Anionic Structure of the So-called Ammonium
Dimolybdate (NH,),Mo,O
,
melts, which likewise contains tetrahedral and octahedral
building units"'.
Two MOO(,octahedra are bound ria a common edge [oxygen
atoms 0" and 0 " ' ;cf. Fig. 21 across a symmetry center
to give a M o , O t o unit. Each of the M o 2 0 1 i units
,
are linked
stepwise by two MOO, tetrahedra ria common oxygen atoms
[03and 0'1 to give infinite chains. The distances betwee!
the molybdenum atoms are 3.158 [Mol--Mo'] and 3.169A
[Mo'-Mo"].
The molybdenum-oxygen distances are shown
in Fig. 2. The anion chains are crosslinked ilia a system of
hydrogen bonds through ammonium ions. The distances
between the nitrogen atoms and their nearest neighboring
oxygen atoms are 2.79 to 2.99A.
By Inimr Kniipnatlcl, Hans H a r t / , Wo/fLDit.rrich Hunnius, and
Jouchim Fwhs['l
( N H 4 ) 2 M 0 2 0crystallizes
as colorless platelets from a warm
concentrated solution (60°C) of ammonium heptamolybdate,
(NH,),,Mo-O2,.4H2O, to which ammonia and ammonium
chloride have been added"'.
The triclinic unit cell of space group PT contains t w o formula
units.
Its lattice constants are: a=7.261 i0.001,
h=7.961 &O.OOl,
<,=7.326&0.001
?=82.63+0.05.
= 94.47 F0.05, y = 1 14.64 & 0.05".
The structure was elucidated on the basis of three-dimensional
diffraction data with evaluation of 3607 independent reflections
and refinement to an R value of 5.4'7,.
The salt does not contain a dimeric, but rather a po/j.nzer-ic
anion, in which the MOO,, octahedra and M o o 4 tetrahedra
are linked to form chains (Fig. 1).The coupling is of a completely different type from that in Na,Mo,O, prepared from
A:
t + . 2. Molqbdenum-oxygen distances [A] in ( M o . 0 ;
i n iinit'i
o f the last decimal place a r e Riven
in
1, :standard deviations
parentheses
The compound is conveniently named according to the "baseacid ratio", (NH,),O:MoO, = 1 :2, as ammonium (1 :2)molybdate. Knowledge of its structure is of interest for tinderstanding the formation of polyanions in aqueous solution.
Keceivcd .ILinc 31. 1Y74 [ Z 100 IF]
G c i m a n version: Angeu. Cheni. 86. 894 (1974)
Fig. I Anionic structure o f ( N f { , ) . M o : O
[*] Prof. I>r I . Fiichs. Prof. Dr. H. Hartl. Dr. W.-I>. Hunnius, and Ihpl.-Chem.
I. Kniipnadcl
Institiit fur Anorganische Chemie t'B 21 W E I der kreien L'niversitiit
1 Berlin 33. Fabeckstrasse 34 - 36 ( G e r m a n y )
H r i w 1 i u \ . Z. Naturforsch.. in press
[2] I. Lindqrisr, Acta Chem. Scand. 4. 1066 (1950): M. Srlehorg. Acta Chem.
Scand. 21.499 (1967).
[ I ] 11:-11.
ABSTRACTS
tions of Chain Molecules. Accounts Chem. Res. 7, 218-225
references]
[Rd 730 IE-L]
( 1974): 63
The biosynthesis of collagen is described by E. J . Miller and
!I J . Mofukas. Five genetically different a-chains of collagen
The characterization of chain molecules by their dipole moments
is the subject of a review by J . E. Murk. Theoretical analysis
of the measured dipole moments of randomly coiled chain
molecules can provide valuable information on the conformational energies and spatial configurations of such molecules.
Examples are "stereochemical copolymers", c. 9. polyvinyl
chloride and poly(p-chlorostyrene) and "chemical copolymers", e. g. poly(p-chlorostyrene-p-methylstyrene)
copolymer.
[The Use of Dipole Moments to Characterize ConfiguraAngrw. Chrm. internat. Edit.
1 Vol. 13
( 1 9 7 4 ) 1 No. I 2
are known which aggregate to give four types of trimers.
Thedistribution oftheaggregate types is in part organ-specific.
The messenger RNA for the synthesis of the r-chains stems
from one cistron ;the hydroxylation of prolyl and lysyl residues
takes place simultaneously or immediately after the translation. The chains aggregate and form helices as they are still
growing on the polysomes, while glycosylation to procollagen
takes place later. Procollagen is finally converted by proteolysis
into collagen. The findings are discussed in connection with
the concepts of cell morphology, localization, transport and
823
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structure, nh4, called, anionic, ammonium, dimolybdate, 2mo2o7
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