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Matter Preserving Synthetic Pathways and Semi-Empirical Computer Assisted Planning of Syntheses.

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Symmetries and/or permutational equivalencies[’. in the
EMEFIEM may be represented by permutations of the
indices h or p and v, respectively.
be-Matrices which differ only by permutations of indices
whose atoms belong to the same element are equivalent.
Any set of equivalent be-matrices contains E ! irreducible
matrices. These are in block form if the represented EM
contains E disjoint molecules. Further, they are the bematrices of the individual molecules within the EM.
Equivalent irreducible be-matrices differ only by permutations of the blocks.
Chemical processes correspond to interconversions
E M p E M , of IEM (EM, and EM,EFIEM) and are
represented by eq. (6) where R, is a transformation operator.
acting on some M, correspond to processes described by a
time-dependent Schrodinger equation.
Potential applications of this equation include the computer assisted planning of syntheses, elucidation of reaction
mechanisms and mass spectrometric patternsl7I, and
documentation of chemical reactions.
Received: May 26,1971 [Z 503a IE]
revised: August 3, 1971
German version: Angew. Chem. 83.980 (1971)
Matter Preserving Synthetic Pathways
and Semi-Empirical Computer Assisted Planning
of Syntheses[‘’
By Ivar Ugi and P a d Gillespie“’
The set A, of free atoms Ao={A,,,A ,,,... A,,) is represented by a be matrix M, whose diagonal elements are
ebl, and whose b-region contains only zeros. Transformations R, generate from M,, according to eq. (6),the
set F that corresponds to the total FIEM16].Cycles of such
transformations form closed lines in the corresponding
topological space.
Equation (6) then may be considered the consequent
result of the application of logical structure^['^ to chemical
systems, in short, a master equation for describing the
chemistry of the FIEM.
The various operators RP correspond to various types of
chemical processes.
It is interesting to note that eq. (6) contains any of the
conservation laws one normally assumes in the solution
to problems within chemical systems, e.g., conservations
of mass, charge, electrons, etc. It follows that those transformations generated as a result of the operation of R ,
[f] Chemistry and Logical Structures, Part 3.-Part
Synthetic planning processes consist of two steps ; first
one looks for the pathways that lead from readily available
starting materials to a target molecule Z , then one decides
which of these conceivable pathways is the optimum as a
function of some chosen criteria. This communication
deals primarily with the problem of determining the
available synthetic alternatives without detailed discussion
of the evaluation problem[31.
The search for a synthetic pathway is best accomplished
by “working the problem backwards”[41.A target molecular
structure Z is analyzed for “seams” in order to find the
set Y of precursors {Y,,Y,, . _ _
Y,,
, ...) that can be
converted by one step reactions into Z . A set X of compounds (X,,X,, ..., X,, ...) are then sought which can be
converted in one-step reactions into the precursors
{Yl,Y2,..., Yy, ...) until a set A of convenient starting
materials {A,, ..., A,, ...} is achieved. Thus the mappings
A, -+ B,-+.-. --t Z yields a tree (1) of synthetic pathways.
2: see Ref. [2].
[2] P . Gillespie, P . H o f f a n n , H . Klusacek, D. Marquarding, S . Pfohl,
F. Ramirez, E. A . Tsofis, and I. Ugi, Angew. Chem. 83, 691 (1971);
Angew. Chem. internat. Edit. 10, 687 (1971).
[3] The he matrices differ fundamentally from extended connectivity
matrices, the so-called principal matrices of molecules, by being
endowed with well defined transformation properties. Further, the be
matrices not only refer to molecules but EM as well.
[4] The steric features of the considered systems can also be represented by additional diagonal entries referring to the local configurations of
the vicinities of the individual atoms; the numbering of the atoms
can serve as a sequence rule for descriptor^[^! An alternative would
be to include some suitably chosen nuclear coordinates, e.g. Cartesian
or approximate cubic lattice coordinate^!^'.
[ 5 ] I . Ugi, D. Marquarding, H . Klusacek, G . Gokrl, and P. Gillespie,
Angew. Chem. 82, 741 (1970); Angew. Chem. Internat. Edit. 9, 703
(1970).
[6] We gratefully acknowledge a valuable discussion with Prof.
J . Dugundji (Department of Mathematics, U.S.C) during which the
following evolved: The be-matrices of an FIEM define a finite metric
space which may be properly called the EM space or the chemical
topology of the FIEM. In this space the distanced between two points
(ie., EM and EM’, represented by their be-matrices M and M’) is
given by d=IM-M’(. The EM space of a FIEM is a subspace of the
unicersal chemical topology referring to the universal FIEM that
contains all chemical compounds of the universe. Chemical topology,
as a term, has previously been used in an attempt to represent steric
features of molecules topologically‘’]. It follows that a synthetic
route is a pathway in the topological space of an FIEM connecting a
starting material point, frequently uia other points, with that of a
product such that none of the distances between two points exceeds
a specified limit (see Ref. [7]).
[7] I. U g i and P . Gillespie, Angew. Chem. 6’3, 982 (1971); Angew.
Chem. internat. Edit. 10, 915 (1971).
Angew. Chem. iniernaf. Edit. / Vol. I0 (1971) / N o . 12
An existing computer program”], designed to produce
this “tree”, and employing empirical information concerning known synthetic reactions, is limited to the
generation of those synthetic pathways which are suggested
to the chemist by his knowledge of the literature.
As in all chemical processes, synthetically useful reactions
including sequences of reactions (if suitably defined)
proceed with a constant matter balanceL6’and correspond
to interconversions of IEME FIEM[’]. Therefore, eq. (2)Iz1
provides the basis for a program conceptually dependent
upon fundamental principles which, in contrast to the
[*] Prof. Dr. I. Ugi and Dr. P. Gillespie
Department of Chemistry, University of Southern California
Los Angeles, Calif. 90007 (USA)
91 5
above empirical, analogy oriented program, generates
the complete set of all conceivable synthetic routes for a
given target. This includes new reactions, i.e., computer
invented pathways suggesting experimental discovery.
At any given moment, these synthetic pathways not only
contain the characteristic intermediates A,, Bb,.. .Y,, Z , but
all unconsumed starting materials and existing byproducts that accompany the intermediates as well. The
pathway A,-tBb+ ... Z shown in scheme (3) may also be
A, + A ,
B, + Bb
c, + cy
...
+
B, + BL
+
C,
+
...
+
+ Cr
...
(3)
x,+ XI
x,+ x; Y, + Y;
...
--t
--t
Y,+Y;
---t
z+z
represented by the balance of matter preserving pathway
EMinilialpEMb+
‘ ~ ~ E M , + E M f i (4),
n a l with A,EEMinitial,
BbeEMb,...,Z E EMfinal.
+ A, + Bb
B b + BL + Bb
+ Cl + ... + X; + Y;}
+ C: + ... + X; + Y ; )
B, + B; + C: + ... + X; + Y;}
BE + Cf: + ... + X, + X: + X i + Y;)
B; + C: + ... + X: + Y, + Y; + Y;}
8; + C: + ... + X i + Y; + Z, + Z:}
A,
(4)
An input of Mfinalis required for the matter preserving
synthetic path computer program. Additional input of
MiniIial,
if known, reduces output as well as run time.
From these inputs, i. e. be-matrices[’’, the complete set of
transformations, R,, ... R,, for
ceptional cases three connections are dissected or made,
I
and bond orders b,, in M , are changed by Ab,”
with simultaneous changes in C, by A&,= & 1 (for radical
reactions) or by A&k= 0, F2 (for ionic reactions). Preferred
transformations can be effected by loading the transformation invariant i-region of the be matrix121with
further information regarding the system at hand, e.g.,
kinetic or thermodynamic pair parameters. Relative
“charge affinity” information in the form of an extended
Evans-Lapworth Scheme may be used to indicate by the
algebraic sign and values of the i,” which of the bonds
b are preferentially subject to ionic reactions and deter’LY
mine which of the atoms (A, or A”) will play the nucleophilic r ~ l e [ ~ .Heats
~ ] . of bond formation AH,> between
A, and A, may be included as off diagonal matrix elements,
A H,,, in the i-region of the be matrices. A summation of
these A HPvaccording to the b-region serves as an estimate
of the heat of formation for the corresponding EMo.
This information will allow the program to reject excessively endothermic reactions.
Subsequent selection rules based upon other known
principles such as the Dewar-Evans r ~ l e [ ~ - as
’ ~well
] as
general empirical or semi-empirical information on
chemical reactivity can be added to the i-region of the be
matrices. The latter include observations to the effect that
in cyclic processes involving five- or six-membered rings
and carbon compounds, those R , are preferred that
represent reactions involving multiple bonds, bonds
immediate or next neighbors to multiple bonds or electrically charged or heteroatoms. If more than one of these
conditions applies to one of the bonds the preference
for reactions involving these bonds is enhanced.
An example of a synthetic planning process for N-formylglycine-N’-methylamide ( I ) may serve to illustrate the
present method and its potential usefulness. If one looks
for those syntheses of ( I ) that proceed with the loss of one
mole of water, one starts with R =CH, and
is generated. Sequential application of the operators
R,, ..., R, on MiniIlal
yield the be matrices which represent
the EM, encountered on the individual paths while the
operators R , represent the chemical processes of the
synthetic steps.
If it is not possible to derive the EMfinaldirectly from the
formula of Z , one adds, as the required complements,
a molecules of A-B, equivalent to A@+ :Be or A , + B.,
and p molecules of C=D representing unsaturated byproducts (e.g., (C6H5)3-0) of synthetic steps to form
the EMrinal=( Z a(A-B)
p(C=D)}. From this the
program yields EM, representations containing the Y,
that can be identified, simultaneously identifying the
complements A-B and C=D of Z . In the next step the
Y, are subjected to an analogous treatment etc., until
readily available starting materials are reached.
+
+
Simplification of matrices with an attendent reduction of
computer time can be gained by replacing a substituent on
Z with an R (O<R6112,Reol=I) symbol possessing an
electron or its polyfunctional analog if this substituent
appears in a starting material and no reaction sequence
involves it.
In order to achieve a convenient and economical procedure
the operator R P must be subjected to empirical selection
rules such that those steps can be avoided that do not
proceed with practical rates or yields. The rules must
provide that only those transformations are used that
correspond to operations whereby one, two or in ex916
assigns numbers to the atoms of ( I ) as indicated. Further,
one can label the latter with (+) or (-) according to an
Evans-Lapworth patternL7.
‘I. From these, one obtains a
bei matrix Mfinal(6a). The b-region entries represent the
bond system of EMfinal;the number, b3,=2, in the
second column, third row means that in ( I ) the C-atom.
2 is connected by a double bond to the 0-atom 3. Diagonal
entries represent those numbers of electrons belonging
to the corresponding atoms. For example, the third diagonal
element from the top e,=2+4 relates to the fact that six
valence electrons belong to 0 - 3 of which two are bonding
and four are “free”. Entries to the i-region[’I are relative
“charge affinity” data concerning pairs of atoms in the
sense of an extended Evans-Lapworth pattern; the (+)
sign of i,, = + 2 in (6a) indicates that C-atom 2 is electrophilic us. N-atom 4, the latter being nucleophilic relative
to the former. The value 2 of i,, represents a crude estimate
of a relative charge affinity difference which does not
always correspond to an electronegativity difference.
Higher iVvvalues for a pair of atoms (A,,A,) indicates an
increased likelihood for an ionic reaction involving bond
making or bond breaking between A, and A,.
Angew. Chem. internal. Edit. J VoI. 10 (1971) 1 No. 12
H
1
H1
c 2
0 3
N4
H5
H6
c 7
H8
c 9
0 10
N 11
H 12
R 13
H 14
0 15
H 16
0
0
0
0
0
0
0
0
0
0
0
0
0
,o
N
4
+3 +2
0
0
+3 +2
0
0
2 2 + 4 -1 - 3 -3
1
0 3 + 2 - 2 -2
0
0
1
1
O
0
0
0
0
1
0
1
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
n
o
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
C
2
O
3
N
4
H
5
H
6
t i
0 +I +3 +2
0
0
O + 3 + 2
-3 -3 -3
0 -1
- 2 -2 -2 + l
0
+ l
0 & 1 + 3 + 2
+ 1
O _ f l + 3 + 2
4 -1 + 2 + 3 + 2
1
I +I+ 3 + 2
1
0
4 + 3 + 2
0
0
2 2 + 4 -1
0
0
I
03+2
o o o o I
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
C
7
H
8
4
1
1
0
0
0 +3
0
0
0 + 3
-3 -3 -3
0
- 2 -2 -2 +1
0
0
O f 3
0
0
0 + 3
-1 -1 -1 1-3
0
0
0 +3
0
0
0 + 3
- 3 -3 -3
0
-2
-1 - 2 + I
I
o 0+3
0
-3
-2
0
0
-1
0
(6a)
O = M final
-3
-2
o
0
1 + 3
0
12+4-3
0
1 1 -
0
1 0 + 3
0
0
0
0
0
0
o7
C
O
N
H
R
H
O
H
9 1 0 1 1 1 2 1 3 1 4 1 5 1 6
1
1
4
- 22+4
3+2
1
1
I
1
4
1
2
1
1
6
3 +2
1
1
1
1
12+4
1
H
1
HI
c 2
0 3
N4
H5
H6
c 7
H8
c 9
0 10
N 11
H 12
R 13
H 14
0 15
H 16
C
2
N
4
H
5
3f2
1
1
O
3
H
6
C
7
H
8
3,3
1
1
C
9
O
10
N
11
H
12
H
14
O
15
H
16
R
H
13
14
O
15
H
16
R
13
4
2 2f4
1
1
1
3+2e
I
1+ 6 e
3
4@
1
I
I
1
H
1
Hi
c 2
0 3
N4
H5
H6
c 7
H8
c 9
0 10
N 11
H 12
R 13
H 14
0 15
H 16
O
3
1 -1
I
4
H
1
H1
c 2
0 3
N4
HS
H6
c 7
H8
c 9
0 10
N 11
H 12
R 13
H 14
0 15
H 16
C
2
C
2
O
3
N
4
H
5
3+2
1
1
H
6
C
1
H
8
4
1
1
C
9
O
10
N
11
H
12
1
1
Angew. Chem. internal. Edit. 1 VoI. 10 (1971) 1 No. 12
4
2 2+4
1
1
3+2e
2f4
3
1
4@
1
I
1
2
I
1
2f4
1
917
In (6b)-(6d), the “zeros” of the b-region as well as the
entries of the i-region that correspond to those of (6a)
are omitted for simplicity. Additionally, if bond enthalpy
data AH,” had been included in the i-region, one would
find that the sequence (6a)-(6d) corresponds to a favored,
strongly exothermic pathway.
One of the transformations defined by the octet rule
(Ae,=O) which is preferred according to the entries of the
i-region leads from (6a) to Ma.add
(6b) and from here one
obtains, e.g., analogously Mprec.( 6 4 and from this Miniliai
(6d). This sequence of transformations corresponds
to the matter balance preserving synthetic pathway
EMinitial +EMprecursor
EM,.,,,
EMfinal.
+
+
An abbreviated flow chart for the program used to generate
solutions to the be matrix transformations follows :
1
I
Input Molecules
Molecules=M,,M,, ...M,, whereeach M consistsof n, atoms.
Total set ofaroms = {A,,A, ,...,A,,,A,, ,._,Anx:
Zdentify 7?ansformation and Properties for Consideration
Input p. where p is the identifier for transformation R p . Input
B,.&, ..., where {pi} identifies the atom-pair properties,
Ipl,Ioz, ... to be considered under Rp.
I
Construct (bvv)and (e,J for Consideration
M is n x n , where n
=
1
n,.
,=I
EM,”,,,,,
Diagonal elements, M,, = px= valence electrons for A,.
Sub-diagonal elements, MPv,p < v = b,, = bond (A,,, A,)
=
Construct Necessary I Matrices for R ,
Construct IB1,1p2,... according to properties p , , p 2 . . . each
I” corresponds to M,,”,p i v
Perform Desired Pansformation
Perform R, on M -t M‘. R , = f(b,,, pii. XIB’). Generate
*
The above reaction is a four component
of (2) + ( 3 ) ( 4 ) ( 5 ) . If this investigation had been
carried out before 1959, then the four component condensation might have been proposed by a computer for
experimental discovery.
Are There Further Pansformationsfor Consideration
I
I
I
C L
+ +
For the prediction of conceivable mass spectrographic
fragment patterns, the parent molecule or parent ion may
be represented by its be matrix M,,. Those EME FIEM
generated by suitably selected classes of dissecting transformation operators acting on M, represent the fragments.
This is in contrast to existing machine assisted mass
spectral interpretation schemes that depend upon empirical
data[”l.
For the generation of a computer program, logical thought
is transformed into algorithms. The latter are created from
flow charts which represent the flow of logic and decision
relative to a problem that will be solved by a computer.
[I]
Chemistry and Logical Structures, Part 4. This work was supported
by the Department of Health, Education and Welfare, Biochemical
Support Grant N o RR-07012-04.-Part 3: see Ref. [2].
[2] I . Ugi and P. Gillespie, Angew. Chem. 83,980 (1971); Angew. Chem.
internat. Edit. 10.914 (1971).
[3] G. Kaufhold and 1. Ugi developed, in 1967 (unpublished results),
an empirical computer method for generating and evaluating synthetic
pathways for peptides using maximum yield as the criterion. (a) I . Ugi,
Rec. Chem. Progr. 30,289 (1969); (b) G. Gokel, P. Hofmann, H . Klieman,
H . Klusacek, G. Ludke, D. Marpuarding, and I . Ugi in I . Ugi: Isonitrile
Chemistry. Academic Press, New York, 1971, pp 211; (c) 1. Ugi,
Chem. Rep. Intra-Science Foundation 1971, Vol. 4 (in press).
[4] R . E. Irehnd: Organic Synthesis. Prentice-Hall, Englewood Cliffs,
N.Y., 1969, p. 17.
[ 5 ] E . J . Corey and W 7: Wipke, Science 166, 178 (1969).
918
0
Exit
Note: If dissection is desired, transformations will be performed on
successive M*’s.
M, molecule i
Ai atom i
n i number of atoms in molecule i
p identifier for a transformation, R
R transformation identified by p.
Bi identifier for atom-pair property
p,v row, column numbers for matrix M .
M be matrix
M* be matrix generated by some R, on M
Received: May 26, 1971 [Z 503b IE]
revised: August 3, 1971
German version: Angew. Chem. 83,982 (1971)
[6] In this context we wish to mention the treatment of matter balance
problems with a matrix method by G. Kaufhold and 1. Ugi, Liebigs
Ann. Chem. 709, 11 (1967).
[7] D. Evans has recently pointed out in lectures and discussions, e.g.,
at the UCLA Physical Organic Chemistry Seminar on May 6, 1971,
that the precursors of a given target molecule can be derived on the
basis of Lapworth‘s “charge affinity” assignments [S]. Ref. [3 b]
contains a discussion of the possibilities of application of Evans’
conception in the planning of syntheses with the aid of EDV on the
basis of the universal equation (2).
[8] A. Lapworrh, J. Chem. SOC.121,416 (1922).
[9] The Dewar-Evans rules [lo], as recently formulated by Dewar
[11, 127, and based on Evans’ rule of isoconjugation [I31 together
with the P M O treatment of aromaticity and the concept of antiHiickel systems, correspond to a simple and comprehensive theory
of concerted reactions. These can be regarded either as providing a
Angew. Chem. internut. Edil. J Yol. 10 (1971) J No. I 2
satisfactory basis for the Woodward-Hoffmann rules 1141 or a satisfactory alternative to them and related [15, 161 or corresponding
treatments 116, 171 of the underlying problem.
[lo] See also: 1. Ugi, D. Marquarding, H . Klusacek, G. Gokel, and
P. Gillespie, Angew. Chem. 82, 741 (1970); Angew. Chem. Internat.
Edit. 9, 703 (1970).
[ill M . J . S . Dewar, Angew. Chem. 83, 859 (1971); Angew. Chem.
internat. Edit. 10, 845 (1971).
[12] M . J . S . Dewar, Tetrahedron Suppl. 8, 75 (1966).
1131 M . G . Evans and M . Polanyi, Trans. Faraday SOC.34, 11 (1938);
M . G. Evans and E. Warhurst, ibid. 34, 614 (1938); M . G. Evans, ibid.
35,824 (1939).
[14] R. B. Woodward and R . Hoffmann, Angew. Chem. 81, 797 (1969);
Angew. Chem. internat. Edit. 8, 781 (1969).
[I51 H . C.Longuett-Higgins and E. W: Abrahamson, J. Amer. Chem.
SOC.87, 2045 (1965).
1161 K . Fukur in P:O. Lowdin and B. Pullman: Molecular Orbitals
in Chemistry, Physics, and Biology Academic Press, New York 1964,
p. 513; Accounts Chem. Res. 4,57 (1971).
[I71 J . J . C. Mulder and 1. Oosterhoa Chem. Commun. 1970,305,307.
[lS] Cf. e . g . : 1. Ugi, Angew. Chem. 74, 9 (1962); Angew. Chem.
internat. Edit. I, 8 (1962).
1191 A . Buchs, A . M . Duffield, G. Schroll, C. Djerassi, A . B. Delfine,
B. G . Buchanan, G. L. Sutherland, E. Q. Fergenbaum, and J . Lederberg,
J. Amer. Chem. SOC.92,6831 (1970).
In the mass spectrum (50 eV) the molecular ion occurs at
m/e 204. The ionization-induced degradation of (2) resembles that of (3) ; however, the intensity ratios of the
ions at mle 204, 176, and 148 exhibit characteristic differences for the two compounds.
Contrary to the prevailing opinion[41,the spectroscopic
data show that the N, can act quite well as a stronger donor
than CO if attention is paid to the sum of the o-donor and
n-acceptor strengths. The weakening of the vcE0 frequencies compared to (3),as well as the drop in force constants
k and ki calculated according t," ref. ['I, which are respectively 15.61 and 0.49 mdyn/A for ( 3 ) and 15.38 and
0.45mdyn/A for (2), and the upfield shift of the C,H,
protons, evidence an increase in electron density on the
central metal atom due to the N, ligand.
(2) is the first N,-complex to have been synthesized by
controlled oxidation of the corresponding hydrazine
derivative. Further studies on related complexes will show
whether the technique is applicable to the systematic
synthesis of N, complexes. Preliminary experiments on
(2) indicate a high reactivity in solution and ready substitution of the N, ligand by other donors.
Oxidation of C,H,Mn(CO),N,H, to
C,H,Mn(CO),N,, a New Dinitrogen Complex"]
By Dieter Sellmann"]
In order to study the redox behavior of complexed hydrazine, C,H,Mn(CO),N,H,
( I ) [ * ] was subjected to the
action of various oxidizing agents. The two-electron oxidant
H,0,/Cu2+ was found to convert ( I ) into n-cyclopentadienyldicarbonyldinitrogenmanganese(1) (2) in 40% yield
according to :
Received: July 28,1971 [Z 506 IE]
German version: Angew. Chem. 83, 1017 (1971)
[l] Reactions of complexed ligands, Part 4.-Part 3: D. Sellmann,
Z . Naturforsch. 26b, in press (1971).
[2] D. Sellmann, Z. Naturforsch. 2Sb, 890 (1970).
[3] I am grateful to Dr. J . Muller for recording and discussing the mass
spectrum.
141 Cf. K . G . Coulton, R . L. DeKok, and R . F . Fenske, J. Amer. Chem.
SOC.92, 515 (1970); J . Chatt, D. P. Melville, and R. L. Richards, J. Chem.
SOC.A 1969,2841 ; G. M . Bancroft, M . J . Mays, and B. E. Prater, Chem.
Commun. 1969, 585.
[ 5 ] F. A. Cotton and C. S. Kraihanzel, J. Amer. Chem. SOC.84, 4432
(1962).
Fluorochlorobromoiodosilaner**l
(2)
By Friedrich Hoper and Walter Veigl"]
"0
After removal of the solvent tetrahydrofuran, (2) sublimed
at room temperature ( z10- torr) to give large, reddishbrown crystals that are diamagnetic and highly refractive.
They are also air-stable, resublimable, melt at 60°C with
evolution of gas, and dissolve in all common organic solvents. Their composition and structure were confirmed by
elemental analysis, IR, 'H-NMR, and mass spectroscopy'?
The IR spectrum of the complex (2) in n-hexane shows
three characteristic very strong bands of approximately
equal intensity at 2169 (vNEN),1980 (vcE0, A'), and 1923
, in KBr these bands are shifted to 2163,
cm-' ( v ~ = ~Bl);
1965, and 1895 cm-'.
The method of preparation and the extremely intense vNGN
band suggest "end-on" bonding of the N, ligand to the
central metal atom.
In the 'H-NMR spectrum ([D,]-acetone) the C,H, protons of (2) show a sharp singlet at z= 5.16, which is shifted
upfield by 12 Hz compared to the signal of C,H,Mn(CO),
(3).
[*] Dr. D. Sellmann
Anorganisch-chemisches Laboratorium
der Technischen Universitat
8 Miinchen 2, Arcisstrasse 21 (Germany)
Angew. Chem. internat. Edit.J Vol. 10 (1971) J No. 12
Halosilanes of the type SK,Y and SX,Y have been known
for a long time"], but only a few investigations regarding
SiX,YZ compounds have been published in the literature[' - 4 1 . In our investigations of halogen exchange reactions at the silicon atomLs1we have now succeeded in
synthesizing the hitherto unknown fluorochlorobromoiodosilane SiFClBrI (I) :
SiBr,
SiFBr,
SbF,
SiFBr,
SbCI,
(2)
SiFCl€ir,
(3)
+ SIF Br,_,(n=2-4)
(1)
(2)
SiFCIBr,
+ SiFCI,Br,_,
-
(n=2, 3)
(2)
(3)
+ HSiI,
SiFClBrI
+ HSiBrI,
(3)
(1)
By modifying the reaction conditions (slow addition of
Sb-halide to boiling halosilane, rapid removal of reaction
products) used by Schumb and Anderson''. 61 in reactions
(1) and (2) we have been able to obtain better yields of (2)
[*] Doz. Dr. F. Holler and W. Veigl
Institut fur Anorganische Chemie der Technischen Hochschule
A-8010 Graz, Rechbauerstrasse 12 (Austria)
p*] This work was supported by the Fonds zur Forderung der wissenschaftlichen Forschung, Vienna.
919
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