вход по аккаунту


Naked Molecule Chemistry Different Bonding Modes of CO to FeX2.

код для вставкиСкачать
Table 1. Comparison of selected structural parameters of the tetramers
[Me3R-XI4and [Me3R-thp16.
28 1.9
255 (S)
208 (N)
217 (N)
221 (N)
234 (0)
Nonius) with MoKR radiation at 163 K ; no absorption correction
I). Application of anisotropic temperature factors for Pt
and CI (136 parameters, H atoms omitted) gave residual indices of
R=0.054, R,, =0.049 ( w = I/a2/Fo)). Despite the low temperature of
measurement, the two CHCI, molecules exhibit in part very high temperature factors, indicating the existence of disorder, which may have
affected the results of the refinement. Further details of the crystal structure investigation may be obtained from the Fachinformationszentrum
Energie, Physik, Mathematik GmbH, D-75 14 Eggenstein-Leopoldshafen
2 (FRG), on quoting the depository number CSD-53 187, the names of
the authors, and the journal citation.
@ =70.9 cm-
Naked Molecule Chemistry : Different Bonding
Modes of CO to FeX,**
principle, be possible for Pt'" atoms, e.g., in a trans[(NH&Pt'"( 1-methylcytosine)] complex,['51 chelate ring
formation through nitrogen atoms is observed exclusively;
this problem has been discussed in detail.[l6] Chelate complexes of titanocene with xanthinel"] and theophylline["]
show, in the case of xanthine, the unique presence of two
N,O-coordinated as well as one N,C1-coordinated titanocene group, whereas, for theophylline, only a 1 : 1 complex
with titanocene (N7-06 coordination) is formed.
Experimental Procedure
An aqueous solution (20 mL) containing the potassium salt of theophylline
(0.38 g, 0.17 mmol) was added dropwise at room temperature to a solution of
(0.5 g, 0.086 mmol) in 20 mL of water. The resulting solution was refluxed for 5 h and then filtered. The filtrate was concentrated under vacuum and the solid, white residue was recrystallized from dry acetonitrile. White crystals, m.p. >215"C (dec.), were obtained. Yield: ca. 50%. For
the X-ray crystal structure analysis, a small sample was recrystallized from
dry CHCL,.
Received: February 15, 1988;
revised: May 27, 1988 [Z 2619 IE]
German version: Angew. Chem. 100 (1988) 1194
CAS Registry numbers:
[MezPt(HzO)3]2S04, 7270-24-8; [Me$-thp],,
thp],. IZCHCI,, 116050-13-6; Hthp-potassium salt, 57533-87-6.
[I] G. W. Adamson, J. C. Bart, J. J. Daly, J . Chem. SOC.A1971. 2616.
[2] A. G. Swallow, M. R. Truter, Proc. R. SOC.London Ser. A252 (1960)
131 A. C. Hazell, M. R. Truter, Proc. R . SOC.London Ser. A252 (1980) 218.
[4j R. E. Rundle, J. D. Sturdivant, J . Am. Chem. SOC.69 (1947) 1561.
[5] R. N. Hargreaves, M. R. Truter, J . Chem. SOC.A1971. 90.
[6] W. Massa, G. Baum, B. S. Seo, J. Lorberth, J. Organornet. Chem. (1988).
in press.
[7] G. Donnay, L. B. Coleman, N. G. Krieghoff, D. 0. Cowan, Acra Crystall o p . Secf. 8 2 4 (1968) 287.
181 R. Allmann, D. Kucharczyk, Z . Krisfallogr. 165 (1983) 227.
[9] M. Atam, U. Miiller, J. Organomef. Chem. 71 (1974) 435.
[lo] B. Vance, J . Organomet. Chem. 336 (1987) 441.
(111 H. S. Preston, J. C. Mills, C. H. L. Kennard, J. Organornet. Chem. 14
(1968) 447.
[I21 G. Smith, C. H. Kennard, T. C. Mak, J . Organomet. Chem. 290 (1985)
[I31 H. Herdtweck, B. S . Seo, H. Donath, J. Lorberth, J. Organomet. Chem.
(1988). in press.
[14] N. H. Agnew, T. G. Appleton, J. R. Hall, G. F. Kilmister, I.J. McMahon, J. Chem. SOC.Chem. Commun. 1979. 324.
[I51 R. Beyerle-Pfniir, H. Schollhorn, U. Thewalt, B. Lippert, J . Chem. SOC.
Chem. Commun. 1985, 1510.
[I61 J. Reedijk, A. M. J. Fichtinger-Schepman, A. T. van Oosterom, P. van de
Putte, Strucf. Bonding Berlin 67 (1987) 53
[I?] A. L. Beauchamp, F. Belanger-Gariepy, A. Mardhy, D. Cozak, Inorg.
Chim. Acfa 124 (1986) L23.
[I81 D. Cozak, A. Mardhy, M. J. Olivier, A. L. Beauchamp, Inorg. Chem. 25
(1986) 2600.
I191 Crystal structure determination of C , O H ~ ~ N ~ O ~ R . ~space
C H Cgroup
R?, a=2220.7(8), c=2231.4(9) pm, Z = 18, 1322 unique reflections with
FO> 5 u were measured on a four-circle diffractometer (CAD4, EnrafAngew. Chem. l n t . Ed. Engl. 27 (1988) No. 9
By Ian R . Beattie,* Susan D . McDermott,
Elizabeth A . Mathews, Keith R . Millington, and
Andrew D. Willson
It is well established that many metal halides isolated in
inert gas matrices can interact with dopants such as CO to
give species showing vco in the IR spectrum to high frequency of the isolated CO molecule. Hauge et al."' have
summarized much of this work by showing how Avco (the
shift of vco in the "complex" from that of free CO) varies
as a function of the formal metal charge divided by the
square of the "metal to C O distance". Similar data have
recently been given for C O on metal oxide surfaces.'21
When iron(I1) halides are cocondensed at 12 K with argon doped with CO, bands are present in the IR spectrum
to high frequency of free CO. There are also metal halogen
vibrations to low frequency of that of the halide isolated in
pure argon. Noting that CO is known to give complexes
with the (expected) impurities H,Oi3] or HX,14' our spectra
at low dopant concentrations (1 mol YOCO in Ar) show additional features at 2175 cm-' (Cl) and 2169 c m - ' (Br).
The band for the iodide is apparently too close to the impurity bands for reliable observation. The precise position
of these bands and the number of features observed is dependent o n dopant concentration.
On annealing these matrices at temperatures of the order
of 20 K, major changes occur in the spectra of the chloride,
bromide, and iodide. In each case one principal band is
observed in the vco region characteristic of metal carbonyl
halide formation: 2111 (Cl), 2103 (Br), 2088 c m - ' (I). The
precise position of the bands is again to some extent dependent on dopant concentration. There are also two lessintense bands in the 600-cm-' region (609 and 584 c m - '
in the chloride), the higher-frequency band being narrow
while that to lower frequency is broader and shows indications of resolution into a doublet in some spectra. The frequency region below 500 cm-' is complex and will be discussed in detail elsewhere.
Isotopic substitution using 13C0 gave the expected frequency shift for the vc0 bands. The bands near 600 c m - '
both shifted by ca. 15 cm-', suggesting they are M-C-0
[*] Prof. I. R. Beattie, S. D. McDermott, E. A. Mathews, A. D. Willson
Chemistry Department, Southampton University
Southampton SO9 5NH (UK)
Dr. K. R. Millington
CEGB Berkeley Nuclear Laboratories
Berkeley, Gloucestershire, GL13 9PB (UK)
[**I We thank SERC and AEE Winfrith for financial support for this work,
Dr. A . Brisdon and Dr. T. R. Gilson for helpful discussion, Dr. P. J .
Jones for experimental help, and Dr. P Goggin for the spectrum of
AuCl .CO.
0 V C H Verlagsgesellschafr m b H . 0-6940 Weinheim. 1988
0570-0833/88/0909-1161 $ 02.50/0
deformation modes. This frequency region is clear of other
vibrations and represents a useful test for the presence of
metal carbonyl halides in such systems.
Partial isotopic substitution (l2C0 : 13C0 ca. 1 : 1) suggested for the vco region the presence of one degenerate
vibration in the parent (all I2C0) compound.[51Unfortunately, because of the relatively high frequencies of the
carbonyl bands, this region is partially obscured by the intense free I3CO band. Attempts to eliminate all free CO by
annealing at 35 K using a krypton matrix were not successful. In 20 : 1 : 1 Ar : I2CO : I3CO, however, the narrow SMco
band at 609 cm-’ gave a quintet (Fig. 1). For truns-
1. van der Waals: high-frequency v,,~’~;
no observed
M-C-0 skeletaj modes. Example: B F 3 - C 0 with
d(B-C)=2.886 A[’’] and vco in an argon matrix at
2150 ~ m - ’ . [ ’ ~ ]
2. “o-bonded”: high-frequency vco; M-C-0 skeletal modes present. Example: AuCl. CO with
d(Au-C)= 1.93 A[’,] and vco in the region of 2157
3. “n-acceptor”: lower-frequency vco; M-C-0 skeletal modes present. Example: Ni(CO), with
d(Ni-C)= 1.84
and vco at 2058 cm-’.
Matrix isolation represents a sensitive method for
studying such interactions. In particular it may be possible
to examine the relationship between van der Waals, obonded, and n-acceptor species by systematically varying
the acceptor. It should also be possible to examine the
number of CO molecules interacting on one center and
possibly dipole-dipole or phonon interactions. CrF, .n CO
would seem to be an appropriate model for the study of
surface chromium atoms on a-Cr203 where the (001) faces
at 298 K show a single IR peak for CO, varying from 2185
to 2170 cm-’.[I6] Finally, such studies may be relevant to
the occurrence of bond-stretch isomers.[171
v [crf‘l
Fig. I . Effect of ca. 50% ”C isotopic enrichment on 609-cm
tions for equally spaced quintet.
sharp differentiation between the fluoride and the other
halides is associated with the spin changes necessary in
forming the n adduct and with the “harder” metal center.
Certainly the shift of the antisymmetric stretching frequency of FeF2 from 731 cm-’ in Ar to 587 cm-’ in CO
suggests a strong interaction with CO. A complication in
such experiments is the variation in intensity of vco with
frequency.”, “1
At least three types of linear CO interaction can occur,
the boundaries between them not being clear:
- ’ band. x
posiReceived: April 13, 1988 [Z 2702 IE]
German version: Angew. Cbem. 100 (1988) 1202
[Fe(CO),CI,] the out-of-plane deformation of the planar
D4h Fe(CO), residue would be of u2” symmetry. In the absence of coupling this nondegenerate vibration must result
in a quintet for a I :1 I2CO : I3CO isotopic ratio. There is
strong evidence that molecular FeCl, is linearl6]so that acquisition of four C O molecules leads to the trans adduct if
this linearity is retained. The only previously known isomer is the cis form.
The bands observed by us for truns-[Fe(CO),I,]-e,
612, e, 598 cm-’-are close to those proposed
for the same compound produced by photolysis of cis[Fe(C0)412].[7381
However, our assignments reverse those in
the literature for the 6Mcomodes. (We also note that in
one case the bl, mode is reported as IR active.)
Our results suggest that the initial F e X 2 . n C 0 species at
low dopant concentrations has an n value of less than 4.[91
Annealing enables migration of the CO molecules to occur
giving a species which can then reorganize to give the iron
carbonyl halide. If FeCI, is cocondensed with pure CO, the
“n complex” is formed even at 9 K.
It is instructive to contrast the ease of reaction of CO
and the isolated FeI, molecule with a synthetic method for
cis-[Fe(CO),I2] which recommends treatment of Fe12 with
CO at 110 atm for 10 h.[’O1
There is no clear-cut evidence for TI species containing
less than four carbonyl groups. Nor is there evidence for
“n-acceptor” behavior with FeF,. It is possible that the
0 VCH Verlagsgesellscbaft mbH. 0-6940 Weinheim, 1988
[I] R. H. Hauge, S . E. Gransden, J. L. Margrave, J. Chem. SOC. Dalton
Trans. 1979, 745.
[2] M. I. Zaki, H. Knozinger, Spectrocbim. Acra Part A43 (1987) 1455.
131 H. Dubost, Chem. Phys. 12 (1976) 139; H. Dubost, L. Abouaf-Marguin,
Chem. Phys. Len. 1 7 (1972) 269.
[4] L. Andrews, R. T. Arlingham, G. L. Johnson, J. Chem. Phys. 78 (1983)
6347, and references cited therein.
[S] See, e.g., J. H. Darling, J. S. Ogden, J . Chem. SOC.Dalton Trans. 1972,
161 M. Hargittai, I. Hargittai, J. Mol. Spectrosc. 108 (1984) 155.
171 K. Noack. Helu. Cbim. Acta 45 (1962) 1847.
181 M. Pankowski, M. Bigorgne, C. R. Hebd. Seances Acad. Sci. 263 (1966)
[9] C . W. DeKock, D. A. Van Leirsburg, J. Am. Cbem. SOC. 94 (1972)
[lo] W. Hieber, H. Lagally, Z . Anorg. Allg. Cbem. 245 (1940) 305.
[I I] C . Morterra, E. Garrone, V. Bolis, B. Fubini, Spectrocbim. Acra Part A 43
(1987) 1577.
[I21 K. C. Janda, L. S. Bernstein, J. M. Steed, S. E. Novick, W. Klemperer, 1.
Am. Chem. SOC.100 (1978) 8074.
[I31 J. Gebicki, J. Liang, J. Mol. Srruct. 117 (1984) 283.
1141 P. Jones, 2. Nafurforscb.837(1982) 823.
[lS] J. Ladell, B. Post, I. Fankuchen, Acta Crystallogr. 5 (1952) 795.
[I61 D. Scarano, A. Zecchina, Spectrocbim. Acta Part A43 (1987) 1441.
[17] See, e.g., Y. Jean, A. Lledos, J. K. Burdett, R. H. Hoffman, J. Chem. SOC.
Chem. Commun. 1988. 140.
In all cases there is a kinematic increase of vc0 on coordination which
depends on the effective mass of the acceptor and the M-C force constant.
0S70-0833/88/0909-1162 $ 02.50/0
Angew. Chem. Int. Ed. Engl. 27 (1988)No. 9
Без категории
Размер файла
246 Кб
chemistry, bonding, mode, molecules, naked, different, fex2
Пожаловаться на содержимое документа