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Book Review Ion Solvation. By Y. Marcus

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the longest AIL0 length to be referred to as a bond in the
literature,"'' but the interaction is further substantiated by
the Me-AI-Me angle of 140.6(3)". Indeed, a comparison of
van der Waals radii shows that even O(6) interacts to, a
small extent with the aluminum (A1 . . .O = 3.093(5) A).
O(4) and O(5) are outside the contact distance-with the
aluminum atom (Al. . ' 0 =3.460(5) and 3.800(5) A, respectively), and, significantly, the two methyl groups incline toward O(5). However, the aluminum atom should be regarded as 5-coordinate. The two AI-C~,,,,.i,,y,~distances in
the cation are short, AI-C( l3)= 1.915(6) A and AI-C( 14)
= 1.939(7) A, *compared to those in the anion of 2.005(7)
and 2.053(6) A.
c5
A
W
Fig. 2. Crystal structure of the cation of [AIMe? .[ IS ] ~ r o w n - 5 ] ~ [ A 1 M e , C l , ] ~ .
113, IS].
AIL01 =2.26(1), AI-02=2.18(2), A1-03=2.13(1)
A
The structure of [AIMe2.[15]crown-5]@is shown in Figure 2.['3.151
It has a similar configuration to that found for
the JAICI2~[l5]crown-5]@
cation.i31The AI-C distances are
1.99(1) and 2.0I(l)A, and the Me-AI-Me angle is
l78( 1)'.
These studies indicate that [AIR2]@species may be important in the reaction chemistry of Ziegler/Natta systems
with donor ligands.
Received: January 2, 1987;
revised: February 2, 1987 [Z 2035 IE]
German version: Angew. Chem. 99 (1987) 476
[ I ] AIR? species have been implicated in solution studies. See for example:
E. Bonitz, Clirm. Eer. 88 (1955) 742: H. Lehmkuhl, H. I) Kobs, Tetrahedron Lett. 29 (1965) 2505: H. Lehmkuhl. Lrehigc Ann. Chem. 7 / 9 (1968)
40; R. Benn, A. Rufinsky, Angen, Chem. 98 (1986) 851: Anyeu. Chem.
In/ Ed. Enql. 25 ( 1986) 86 I .
[2] S. G. Bolt. Drcsertarmn. University of Alabama 1986.
[3] S. G. Bott, H. Elgamal, J. L. Atwood, J . Am. Chem. Soc. 107 (1985)
1796.
141 J. L. Atwood, H. Elgamal, G. H. Robinson, S. C. Bott, J. A. Weeks, W.
E. Hunter, J. Inclusion Phenom 2 (1984) 367.
[ 5 ] H. Elgamal, Drsserratron. University of Alabama 1985.
f61 T h e formation of a two phase liquid system is indicative o f the presence
o f ionic material. This is the liquid clathrate phenomenon: J. L. Atwood
in 1. L. Atwood, J. E. D. Davies. D D. MacNicol (Eds.): I n c h i o n Compounds. Val. 1, Academic Press, London 1984, pp. 375-405.
(71 S.G. Bott, H. Elgamal. A. W. Coleman, A. J . Baskar, C. M. Means, J. L.
Atwood, Inorg. C1rem.. submitted.
(81 N . C. Means. C. M. Means. S. G. Bott, J. L. Atwood, Inorg Cl7em.. in
press.
[9] In a typical experiment 2.50g (0.01 mol) o f [Cp,TiCI?] a n d 2.65 g
(0.01 mol) of [18Jcrown-6 were mixed together in toluene (ca. 50 ml).
AIMe3 (2.0 ml, 0.02 mol) was slowly added. The reaction began immediately a n d from the red solution ca. 2.64g (62"h) o f colorless crystalline
material was deposited. T h e latter was shown by a n X-ray crystallographic dnalysis to be [AIMeZ-[18]crown-6]"[AIMelC1~]".
[lo] I n each case signals d u e to M-Me ( M = T i , Zr) resonances have been
recorded in the N M R . I t is likely that the [Cp,M(CI)Me] species is
formed rather than [Cp,MMeZ] Other products which apparently contain M-crown linkages have been found in low yield. I t is reasonable to
assume that the [AIMe2.[18]crown-6]'^ species comes from the attack o f
AIMe.0 on the crown after the AIMe, alkylates the transition metal.
T h e formation o f AlMe:Cl in the reaction of AIMel with [Cp,TiCIl] has
been reported. K. Claus, H. Bestian, Justrrs Liehrqs Ann. Chem. 654
(1962) 8 ; F. N. Tebbe, G. W. Parshall, G. S. Reddy, J. Am. Chem. Soc.
I00 (1978) 361 I .
[I I] CoCI? (0.65 g. 0.005 mol) was slurried with [15]crown-5 (1.0 ml, I I g,
0.005 mol) in toluene (ca. 50 ml). AIMe, (2.0 ml, 0.02 mol) was slowly
added. A vigorous reaction ensued, and a black liquid Clathrdte was immediately noted. Colorless, air-sensitive crystals of [AIMe?.[15jcrownS)][AIMe,CII] grew from the liquid clathrate.
/)=93.08(4)',
[I21 P 2 , / n , aa= I1.397(4). h = 12.670(4), c = 17.075(6)
V=2462 A', Z = 4 . C A D 4 diffractometer, Mo,,,. 2.05ZHC46", 1326
measured reflections with 1 2 3 r r ( l ) , MULTAN and difference Fourier
methods, hydrogen atoms located and refined, all non-hydrogen atoms
refined with anisotropic thermal parameters, R = 0 044.
[I31 Further details of the crystal structure investigation may be obtained
from the Director of the Cambridge Data Centre, Cambridge CB2 I EW,
England, on quoting the names of the authors. and the journal citation.
[I41 In [A1CIl-benzo[15]cro~n5)[AIEtCI,]131, the five AIL0 lengths range
from 2.03( I ) to 2.30( I ) A. T h e latter is the longest previously reported a s
a formal bond.
V=215
Z=4.
1151 Pnma, u = l1.184(3), h= 10.928(8), c = 17.717(9)
CAD-4 diffrdctometer, MoK,,, 2 S 2 H 5 4 4 " . I104 measured rellections
with 1 2 3 c r ( I ) MULTAN a n d difference Fourier methods. The crown
was badly disordered. This problem has been discussed: P. C. Stark, M.
Huff, E. A. Babaian, L M. Barden, D C. Hrncir, S. G. Bott, J. L. Atwood, J . I n d Phenonr. 5 , in press. R=O.l52.
A,
A,
A',
BOOK R E V I E W S
Ion Solvation. By Y . Marcus. John Wiley, Chichester 1985.
viii, 306 pp., bound, L 42.00.--ISBN 0-471-90756-1
Chemical reactions are usually carried out in solution,
and often involve ions as reactants. A knowledge of the
interactions between solvent molecules and dissolved ions
is therefore of great importance for understanding and
thereby influencing such reactions.
The better-known books on this topic are already rather
outdated, and Prof. Yizhak Marcus of the Hebrew Univer486
sity of Jerusalem has therefore taken on the task of bringing the subject up to date, and treating some parts of it in a
completely new way. It must be said at the outset that he
appears to have succeeded very well. The nine chapters
cover every important aspect of the solvation of ions in
aqueous and nonaqueous media.
Following a brief introductory chapter (Significance and
Phenomenology of Ion Solvation), the simple case of an
interaction between a single ion and a single solvent moleAngeu. Chem. Inr. Ed. Enql. 26 (19871 No. 5
cule in the gas phase is first discussed (Ion Solvation in the
Gas Phase). This is followed by a treatment of the solvation of a single ion by many solvent molecules, as in a dilute solution, dealing with structural, spectrochemical, and
kinetic aspects. Chapter 3 (Interaction Models for Ion Solvation) describes various theoretical models based on statistical thermodynamics considerations. Chapter 4 (Structural and Kinetic Aspects) deals with changes in the dynamic behavior of the solvent molecules caused by ion solvation. Concepts such as first and second solvation shells,
primary and secondary solvation, and coordination and
solvation numbers, are here put into an up-to-date context.
Chapter 5 (Ion Hydration) deals with the special position
occupied by water as a solvent for electrolytes, being concerned exclusively with the thermodynamic and structural
aspects of the ion/water interaction. The growing importance of ions in nonaqueous organic solvents is recognised
in the following chapter (Ion Solvation in Nonaqueous
Solvents). Detailed tables listing relevant properties of
nonaqueous solvents (including empirical parameters of
solvent polarity), and of Gibbs transfer energies AG: (X,
H,O-S)/kJ.mol- ’) for single ions, make this chapter one
of the most useful in the book. Here the reader benefits
from the knowledge which the author gathered in compiling (for IUPAC) critical tables of Gibbs transfer energies,
enthalpies, and entropies for the transfer of single ions
from water into nonaqueous solvents [ Y . Marcus, Pure d
Appl. Chem. 55 (1983) 977; ibid. 57 (1985) 11031. Attempts
at correlating such Gibbs transfer energies with intrinsic
solvent properties using multiparameter equations are also
described.
Chapter 7 is devoted to the selective solvation of ions in
binary solvent mixtures. Chapter 8 deals with solvation of
ion pairs, with particular attention to molten hydrated
salts, perhaps as a result of the author’s laboratory being
near the Dead Sea (Dead Sea Water contains a 8.8 mol
ions/liter!). In the final chapter (Some Applications of Ion
Solvation) many different applications in the fields of electrochemistry, hydrometallurgy, solvent extraction, and organic synthesis are discussed.
The book excels in having a lucid, readable style, and
the detailed author and subject indexes make it easy to
use. Lists of references at the end of each chapter (more
than 310 references altogether) enable the reader to gain
easy access to original papers-although that should often
be unnecessary, since the 64 tables and 36 figures provide
a wealth of useful information. The book should be included in every library, and anyone who can afford to (at
the price of DM 175.00!) should have the book on his
desk-he will certainly get a lot of use from it.
Christian Reichardt [NB 813 IE]
Fachbereich Chemie
der Universitat Marburg (FRG)
Molybdenum Enzymes. Edited by T. C . Spiro. Wiley, ChiChester, England 1985. x, 61 I pp., hardcover, $ 125.00.ISBN 0-47 1-88542-8
This book collects some excellent reviews on the inorganic chemistry and biochemistry of molybdenum, molybdenum-containing enzymes, and the molybdenum-containing cofactors. As noted by P. J. Stephens in his chapter, the
general area of molybdenum enzymes, especially as related
to nitrogen fixation, has been extensively reviewed in comparison to research productivity. These reviews are, however, a significant new contribution because of the emphaAnyen..
(%mi
in!. Ed. Engl. 26 11987) N i l . 5
sis on the chemical aspects as opposed to the agricultural
and genetic aspects. The authors are well chosen, critical,
and careful to avoid oversimplification or overinterpretation. The literature is completely covered through 1983
with some references to 1984. The ten chapters overlap
some in their scope; thus, there is some redundancy that
would not occur in a monograph by a single author. However, to carry on the editor’s analogy, although some of the
same territory is being explored, it is being seen through
different eyes and to different purposes.
Chapter 1, by R. H . Holm and E. Simhon, is a thorough
survey of molybdenum- and tungsten-containing iron-sulfur clusters, their structure, physical properties, reactivity,
especially with respect to substitution and electrochemistry, and synthesis. These results are then discussed by comparison to the properties of the iron-molybdenum cofactor
from nitrogenase. The second chapter, by E . Stiefel and S .
Cramer, concerns the isolation, composition, physical and
chemical properties, assay, and biosynthesis of the ironmolybdenum cofactor. The same authors discuss the molybdenum cofactor (the molybdenum center of enzymes
other than nitrogenase) in Chapter 8.
Chapter 3, by P. J. Stephens, reviews structures of the
iron and iron-molybdenum proteins that compose the nitrogenase enzyme. This review is organized by presenting
the “Dominant Hypothesis” concerning each protein, and
then presenting the experimental data. Conflicts between
the “Dominant Hypothesis” and the data are pointed out
in a stimulating presentation. For example, there are problems with the hypotheses about the types and number of
clusters in light of the cysteine analysis of the proteins.
The next two chapters concern the reactions of nitrogenase. B. Burgess presents a discussion of the varied substrates of nitrogenase and describes the steady-state kinetics results. Emphasis is put on the importance of considering electron flow through the enzyme, careful product
analysis, and the problems of controlling the “inputs” to
the enzyme (reducing equivalents, MgATP, substrate, medium). There is also some discussion of substrate interaction, the evidence for interacting sites on the enzyme, and
the problem of the competition between hydrogen evolution and substrate reduction.
Chapter 5 , by R. 7’horneley and D. Lowe, is the most detailed discussion of the mechanism of nitrogenase. The authors attempt to fit a mechanism and individual rate constants particularly to the reactions of the Klebsiella pneumoniae proteins. The work especially involves the authors’
pre-steady-state kinetics measurements, but also encompasses the steady-state measurements. This type of detailed
analysis is necessary in order to get a real understanding of
this complex system, and in order to avoid errors from too
facile interpretation of individual experiments, but the details will appeal more to committed kineticists. The next
chapter, by M . Hidai, reviews the diverse work o n the inorganic and organometallic chemistry of complexes of dinitrogen and their reactivity. Unfortunately, there still remains little connection between these studies and advances
in the understanding of nitrogenase.
The remaining four chapters concern molybdenum-containing proteins other than nitrogenase. Chapter 7 by D.
Garner and S . Brisfow presents the inorganic background
through a discussion of oxomolybdenum chemistry. This
long presentation also demonstrates the relevance of the
measurements on the inorganic complexes to the study of
the enzymes. Chapter 8 o n the molybdenum cofactor is
next, followed by a detailed discussion by R. Hille and V.
Mussey primarily on xanthine oxidase. Here the emphasis
487
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