• 沒有找到結果。

Charge density study of thiourea S,S-dioxide

N/A
N/A
Protected

Academic year: 2021

Share "Charge density study of thiourea S,S-dioxide"

Copied!
4
0
0

加載中.... (立即查看全文)

全文

(1)

3256 Inorg. Chem. 1990, 29, 3256-3259 verified by independently observing the spectrum of (0EP)-

Fell'( 1 ,4-OC6C12(CN)20)Fe1'1(OEP).) These features are em- phasized in the insets in Figure 4. These observations assure us that the species being observed in these N M R spectra are the intact, dimeric species. Additionally, we have noted that there is no concentration dependence of these spectra, whereas disso- ciation should produce concentration effects.

Asymmetry can also be introduced into these species by em- ploying an unsymmetrical quinone. Figure 5 shows the spectrum obtained by using reaction I with 2,6-dimethyl-l ,4-benzoquinone ( R , R" = H; R', R"' = CH,). The spectrum clearly shows two equally intense pyrrole resonances at 62 and 64 ppm along with a broad resonance at 70 ppm due to the methyl groups of the bridging ligand. The other two protons of that bridge were not seen; presumably they were too broad. Similarly, splitting of the pyrrole resonances was also observed with the diiron complex formed from 2,3-dimethoxy-5-methyl- 1 ,4-benzoquinone (coenzyme

Qo;

R, R' = OMe, R" = Me, R'" = H).

Experimental Section

Materials. Substituted quinones were obtained from Aldrich Chem- icals, and the diiron complexes were obtained via reaction 1 according to the method of Kessel and Hendrickson., The sample used to obtain the spectrum shown in trace C of Figure 1 was prepared by heating a mixture of (TTP)Fe"'OFe"'(TTP) and excess p-hydroquinone in tolu- ene-d, for 1 h at 80 'C in an NMR tube.

Instrumentation, NMR spectra were recorded on Nicolet NT-360 FT

and GE QE-300 spectrometers operating in the quadrature mode (IH

frequencies are 360 and 300 MHz, respectively). The spectra were collected over a 40-kHz bandwidth with 16K data points and a 6-ps 90' pulse. For a typical paramagnetic spectrum, between 500 and 2000 transients were accumulated with a delay time of 50 ms. The signal- to-noise ratio was improved by apodization of the free induction decay. The residual methyl peak of toluene was used as a secondary reference, which was set at 2.09 p p m ,

Acknowledgment. We thank the National Institutes of Health (Grant GM-26226) for support.

Registry No. (TP)Fe"'( 1 ,4-O2C6H4)Fe'"(TTP), 12847 1-79-4; (TT-

P)Fell'( 1 ,4-02C,C14)Fe'11(TTP), I2847 1-80-7; (TTP)Fe"'( 1 ,4-02C6- (2,3-C1)(5,6-CN))Fe1"(TTP), 128471-81-8; (TTP)Fe"'( 1 ,4-02C6Me,)- Fe"'(TTP). 12847 1-82-9; (TTP)Fe"'( 1 ,4-O2C6H,(2,6-Me))Fe"'(TTP),

I28471 -83-0; (TTP)Fe"'( I ,4-o2C6(2,3-MeO)(5-Me))Fe"'(TTP),

12847 1-84- 1.

Contribution from the Department of Chemistry, National Taiwan University, Taipei, Taiwan, ROC Charge Density Study of Thiourea S,S-Dioxide

Yu Wang.* Ning-Leh Chang, and Ching-Tzong Pai

Received October 3, I989

Thiourea S,S-dioxide has been studied by X-ray diffraction at room temperature.',2 The unusually long carbon-sulfur bond was noticed,' and a suggestion of mesoionic character with a positive charge located on the (NH2)2C part and a negative charge on the SO2 part of the molecule was made.' Dunitz3 gave an explanation that the weakening of the carbonsulfur p,-p,

is due to the odd electron of SOT being of d, character. In order to understand the bonding character of this molecule, a defor- mation density study was undertaken. The same approach was applied to the thiourea molecule, where the electron density distribution was studied both experimentally and theoretically in It would be a nice comparison between thiourea and thiourea dioxide to see the difference in the C-S bond as well as in the long-pair region of the sulfur atom. The strong hydrogen bonds in this crystal are also of interest.

'To whom correspondence should be addressed.

Table 1. Crystal Data for Thiourea S,S-Dioxide

chem formula (H2N)2CS02 fw 1 I O

a , A 10.719 (2) space group Pnma (No. 62)

b,

A

10.109 (2) p , cm-I 6.10 c, 8, 3.8018 (7) A, A 0.7 107 D,,, , g.cm-' 1.743 transm coeff 0.74-0.89

v,

. f 3 41 1.9 R(F) 0.0225, 0.0183" Z 4 R d F ) 0.0363, 0.0233' T, K I I O @ High-order refinement.

Table 11. Atomic Fractional Coordinates and B(eq)

(A2)

atom refinement X Y Z B(eqId

S a 0.46052 (1) 0.25 0.361 01 (4) 0.827 (5) b 0.46054 (8) 0.25 0.361 06 (3) 0.81 1 (4) c 0.46055 ( I ) 0.25 0.361 OS (2) 0.810 (3) b 0.611 67 (3) 0.25 0.601 29 (11) 0.799 (8) c 0.61 I68 (3) 0.25 0.601 30 (10) 0.809 (9) b 0.66357 (2) 0.36470 (3) 0.66471 (8) 1.070 (6) c 0.66359 (2) 0.36463 (3) 0.66485 (9) 1.071 (7) 0 a 0.401 79 (3) 0.12748 (3) 0.50954 ( I O ) 1.093 (9) b 0.401 73 (2) 0.12767 (2) 0.50968 (7) 1.074 (6) c 0.401 73 (2) 0.12758 (3) 0.50960 (9) 1.074 (7) HI a 0.7370 (7) 0.3696 (9) 0.768 (3) 1.78 (16) b 0.74692 0.37023 0.781 97 1.78 H 2 a 0.6288 (7) 0.4322 ( 1 1 ) 0.6265 (24) 1.72 (17) b 0.61964 0.45005 0.61636 1.72 C a 0.61162 (4) 0.25 0.601 19 (IS) 0.818 (12) N a 0.66361 (3) 0.36477 (3) 0.66477 (11) 1.082 ( I O )

From full data refinement. *From high-angle data ((sin @ / A > 0.65) refinement. From multipole refinement. dB(eq) = (8/3)r21&(i,-

j)a,*a,*.ai.a,.

Experimental Section

The title compound was prepared by oxidizing thiourea with 3% hy- drogen peroxide at 0 OC for 3 h and crystallized in an aqueous solution. The crystal data of (NH2)2CS02 at 1 I O K are listed in Table I. The intensity data were collected on a CAD4 diffractometer equipped with a graphite monochromator and liquid-N, gas flow set up using Mo K a

radiation. A sealed box was designed9 with a dry ice/acetone cold trap to ensure a low humidity around the crystal. Some of the experimental details are given in Table I. The intensity data

were

measured up to 28 = 100' for two equivalent sets of reflections (hkl, hkl). Five measure- ments at $ values from -30 to 30' with a step of 15' were collected for each_ reflection up to 28 = 60'. An additional equivalent set of reflections

( h k l ) was collected up to 28 = 90'. This yielded a total of 8676 mea- surements, which gave 2224 unique reflections after averaging of equivalents. The interest agreement is 2.1%. Three standard reflections monitored every 1 h showed variations of less than f5%. An absorption correction was applied according to 10 measured Faces of the compound. The crystal size is large in one direction, but cutting of the crystal would cause crystal damage. The collimator size was adjusted to ensure that the crystal was in the beam. All of the computations were carried out on a local MicroVAXIII computer using mainly NRCVAX programs.1°

The refinements of the multipole model were also carried out on the MicroVAX computer using the MOLLY program." Both least-squares refinements are based on Fo, with weight calculated as l/[a2(F,)

+

Sullivan, R. L.; Hargreaves, A. Acta Crysfallogr. 1962, I S , 675.

Chen, 1. C.; Wang, Y . Acta Crysfallogr., Secf. C: Crysf. Struct. Commun. 1984, C40, 1890.

Dunitz. J. D. Acta Crystallogr. 1956, 9, 579.

Mullen, D.; Hellner, E. Acta Crystallogr., Sect. B: Sfruct. Crystallogr. Crysf. Chem. 1978,834, 2789.

Mullen, D.; Scheringer, C. Acta Crystallogr., Sect. A : Cryst. Phys., Diffr., Theor. Gen. Crystallogr. 1978, A34, 476.

Kutoglu, A.; Scheringer, C.; Meyer, H.; Schweig, A. Acta Crystallogr., Sect. B: Struct. Sei. 1982, B38, 2626.

Breitenstein, M.; Dannohl, H.; Meyer, H.; Schweig, A,; Seeger, R.: Seeger, U.; Zittlau, W . Intl. Rev. Phys. Chem. 1983. 3, 335. Mullen, D. Acta Crysfallogr., Sect. B Srruct. Sei. 1982, 838, 2620. Ueng, C . H. Ph.D. Thesis, National Taiwan University, 1987. Gabe, E. J.; Lee, F. L.; LePage, Y . Crystallographic Computing 3;

Sheldrick, G. M., Kruger, C., Goddard, R., Eds.; Clarendon Press: Oxford, England, 1985; pp 167-174.

Hansen, N . H.; Coppens, P. Acta Crystallogr., Sect. A : Cryst. Phys., D i f f , Theor. Gen. Crysfallogr. 1978, A34, 909.

0020-1 669/90/ 1329-3256$02.50/0 0 1990 American Chemical Society

Downloaded by NATIONAL TAIWAN UNIV on August 20, 2009

(2)

Notes Inorganic Chemistry, Vol. 29,

NO.

17, 1990 3257 a I - 0 . 6 2 ( 4 ) -0.34 +0.45( 1 ) +0.23

\

- 0 . 6 4 ( 2 ) -0.92 +0.45( 1 ) + 0 . 2 3

Figure 1. (a) Molecular drawin with thermal ellipsoids (50% proba-

bility) at 110 K. Bond lengths

(1)

at 110 K (top) and 300 K (bottom). (b) Choice of local Cartesian axes for the multipole refinements. The numbers near the atoms are the net charges obtained from multipole refinement (top) and from EHMO (bottom).

(O.0IFJ2], An additional multipole refinement based on was also performed; the results were similar but gave slightly higher agreement indices. The deformation density maps generated both from the normal refinement and from the multipole refinement were produced by a locally developed contour-plotting program.I2

Results

The atomic parameters from the full data refinement and the high-order refinement ((sin O)/A

>

0.65

A-l)

using the spherical atom model are given in Table 11. The thermal ellipsoids of the molecule at 110 K and the bond lengths a t both 110 and 300 K are shown in Figure l a . The thermal parameters of the non- hydrogen atoms decrease to 30% on average by lowering the temperature from 300 to 110 K. However, the anisotropy in the thermal vibrations did not change significantly. The atomic scattering factors,

fo,

were calculated from the analytical ex- pression, with the coefficients taken from ref 13b. Anomalous dispersion corrections were applied according to ref 13a.

The experimental deformation density is calculated as the difference between the observed density, pOb, and the superposition of the sum of spherically averaged free atom densities,

Cpc.

The deformation densities were calculated up to a resolution of (sin

(12) Tsai, C. J. Masters Thesis, National Taiwan University, 1982. ( I 3 ) Internarional Tables for X-ray Crystallography; Kynoch: Birmingham,

England. 1974: (a) Vol. 111; (b) Vol. IV.

d

Figure 2. Deformation density maps of the thiourea plane and lane of

NN'S (carbon atom 0.064

A

off the plane contour level): 0.1

e l l 3 ;

solid

lines positive, dashed and dotted lines zero and negative. Key: (a) X - X(high); (b) X(multipo1e) - X(spherical), dynamic; (c) X(multipole)

-

X(spherical), static; (d) pmo

-

x p a o from EHMO.

O)/A = 1.08

A-1.

The Fourier coefficients were taken to be the

differences between kF, and F, values calculated with the atomic parameters obtained from the high-order ((sin O)/A

>

0.65

A-')

refinement. The hydrogen positions were displaced1"16 along the N-H vector to make the N-H distance of 1.0

A.13a

Here k is the optimum scale factor for the data used in the Fourier synthesis ((sin O)/A = 0-1.08

A-').

The experimental deformation electron density distribution for the plane of the thiourea part with a nearly coplanar SO2 fragment

Wang, Y.; Angermund, K.; Goddard, R.;

1987. 109. 1587.

W i n g , Y.fGuo, L. W.; Lin, H. C.; Kao, Inorg. Chem. 1988, 27, 520.

Wang, Y.; Chen, M. J.; Wu, C. H. Acra

Sci. 1988. B44, 179.

Kruger, C. J . Am. Chem. Soc. C . T.; Tsai, C. J.; Bats, J . W. Crystallogr., Sect. B Struct.

Downloaded by NATIONAL TAIWAN UNIV on August 20, 2009

(3)

3258 Inorganic Chemistry, Vol. 29, No. 17, 1990 Notes Table 111. Least-Squares Results of Multipole Refinements (Based

on F) NV" R I b R2b R l w b R k b S conventional 32 0.0286 0.0498 0.0522 0.0687 3.47 monopole 41 0.0240 0.0424 0.0373 0.0581 2.49 octapole 92 0.0181 0.0332 0.0227 0.0498 1.54 octapoleC 97 0.0174 0.0317 0.0217 0.0468 1.47 hexadecapole 120 0.01 7 1 0.03 13 0.0210 0.0447 I .43

a N V = number of variables.

*

R l = x:IFo - kFcl/CFo. R2 = CIF:

-

k F o 2 1 / x F 2 . Rl, = [ ~ w I F ,

-

k F , 1 2 / x ~ F , 2 ] 1 / 2 . RZrv = [ZWIF:

-

kFc212/xwF,4]1/2.

of the neighboring molecule is shown in Figure 2a. There is a positive density accumulation in the N-H, N-C, C-S, and S - 0 bonds. The degree of density accumulation is in the order C-S

>

C-N, N-H

>

S-0. One of the 0.-H-N hydrogen bonds can be easily recognized in Figure 2a with the lone-pair density of the oxygen atom pointed toward the hydrogen atom. The plane perpendicular to Figure 2a, bisecting SO2 and including the C-S bond, is depicted in Figure 3a. It is apparent that the lone-pair electron density of the sulfur atom is located at the apex of the trigonal pyramid extending toward the plane of SO2 a t the bi- section of the 0-S-0 angle, which can also be detected in Figure 2a.

In addition to the normal refinement based on the spherical atom density model, a multipole atomic model refinement" in terms of a polynomial spherical harmonic series was also performed on this compound. The local Cartesian axes are indicated in Figure 1 b. The improvements of the agreement indices over the various stages of expanding the series are illustrated in Table 111. For the final results, terms up to the hexadecapole level are taken for all non-hydrogen atoms and only up to dipole terms for the hydrogen atoms. The final atomic parameters from this refinement are also given i n Table 11. The atomic scattering factors are calculated as the sum of core electron and valence electron scattering factors with coefficients taken from ref 13a. The H e core is taken for C, N, and 0, and the Ne core, for S. The valence configuration of C, N,O, and S are s2p2, s2p3,s2p4, and s2p4, re- spectively. The net atomic charges of the atoms obtained from the refinement with the multipole model are shown in Figure 1 b with C, S, and H bearing positive charges and N and 0 negative charges. The model multipole deformation density distribution is obtained by Fourier synthesis with (F(mu1tipole)

-

F(spherica1)) as the coefficients. F(multipo1e) is calculated as described else- where.l' F(spherica1) is calculated from the same parameters as F(mu1tipole) except that the coefficients of all the multipole terms are set to zero. The corresponding model deformation density maps are shown in Figures 2b and 3b. Figures 2c and 3c are so called pseudo static deformation density maps, where F(multipole) and F(spherica1) are both calculated up to the same resolution of experimental maps with no thermal motion (thermal parameters set to zero). The features of the static and dynamic deformation density distributions are quite similar, but the static one has more pronounced peaks.

A simple EHMO calculation was also performed on this molecule with the aim of getting a theoretical deformation density map and atomic charge distribution. The net charges from such a calculation including d orbitals of the sulfur atom in the basis wave functions are shown in Figure 1 b. The calculation without d orbitals in the basis set of the wave function not only yields much larger charges both on sulfur (+1.9) and oxygen (-1.42) atoms but also yields much less density along the

S-C

bond. Figures 2d and 3d are the calculated static deformation density maps according to the EHMO calculation.

Discussion

Because of the unusual length of the S-C bond in this structure, a polarized bond was prop0~ed.l.~ A recent report" indicates that the site of nucleophilic attack is either the sulfur atom or carbon

With hexadecapole terms of sulfur atoms.

a b d

I

1

_ - .. _ -

Figure 3. Deformation density maps of the plane perpendicular to that

of Figure 2 but including the C-S bond (contour as in Figure 2; (a)-(d) defined as in Figure 2).

atom of R2CS02 depending on the substituent, R. This apparently supports the proposed polarization of the C-S bond, the direction of polarization C--S+02 or C+-S-02 depending on the steric and electronic effects of the substituents on the carbon atom. The molecular dipole moment of thiourea in the 1:l complex of thiourea with parabanic acid is in the direction of S - C 1 * Our

( 1 7 ) Hartwig, U.; Pritzkow, H.; Rall, K.; Sundermeyer, W. Angew Chem.,

Intl. Ed. Engl. 1989. 28, 221. ( 1 8) Weber, H. P.; Craven, B. M. Acta Crystallogr., 1987. 834, 202. See/. B Struct. Sci.

Downloaded by NATIONAL TAIWAN UNIV on August 20, 2009

(4)

Inorg. Chem. 1990, 29, 3259-3260 3259 results for the atomic charge distribution (Figure Ib) based on

the multipole refinement are in good agreement with the following o b s e r ~ a t i o n s : ~ ~ * ~ ~ the H, C, and S atoms are positive, and the 0 and N atoms are negative. This is in accordance with what was proposed for (H2N)&+ with the positive charge mainly on H atoms and for SO2- with the electron density mainly polarized toward the oxygen atoms, leaving the S and C atoms slightly positive, which enables the nucleophilic attack." The K value of the H atom seems to be highly correlated with its net charge. The result here is from the fixed K value of 1.4. This gives the least correlation between dipole terms of H and those of the N atom. The bond lengths (Figure l a ) at low temperature are longer than those of at room temperature, as expected for the thermal motion d i f f e r e n c e ~ . l ~ + ~ ~ However, the C-S length, on the contrary, is shortened somewhat. A similar phenomenon has been observed in other related sulfur bond lengths.I6 The

S-O

distance is longer than a localized double bond,15 and the C-N distance is com- parable to a partially double bond. The C-S bond is slightly longer than the single bond. Thus, the geometry of the structure itself reveals the charge polarization of the form proposed previo~sly.'~~

The experimental deformation density distribution of thiourea S S d i o x i d e in the plane of thiourea appears to be quite similar to that of thiourea: and the density accumulation along the C-S bond is slightly polarized toward the C atom indicating S-C. Although both atoms are positive, the carbon atom is less positive than the sulfur atom. The density accumulation along the N-H and C-N bonds is as expected. The loss of density near the sulfur nucleus has been found in other sulfur-containing compounds,IsJ6J1 This also agrees well with the atomic net charges obtained from the multipole refinement. The density accumulation along the S-0 bonds is less apparent or more diffuse than that of other experimental results.i5 This may be due to the fact that each oxygen atom accepts two intermolecular hydrogen bonds in the crystal. It is interesting to notice that, in the dynamic multipole deformation density map of Figure 2b, the density along the S-O bond is less diffuse and polarized more toward the oxygen atoms (thus yielding a relatively large negative charge for the oxygen atom) than that of the experimental one (Figure 2a). Nevertheless, the H-bonds are still clearly observed in the multipole deformation density map, in spite that the multipole model is a better repre- sentation near the nucleus and in the intramolecular bonded atom region. The influence of the intermolecular H-bonding on the electron distribution has been noticed and studied recently.22 Similarly, the lone-pair density at the sulfur atom is better rep- resented in the multipole deformation density map (Figure 3b) than in the experimental one (Figure 3a) and is comparable to that of the theoretically calculated one (Figure 3d). The pseudo static deformation density distribution (Figures 2c and 3c) gives the deformation density distribution without the thermal smearing effect a t the same resolution level. The resemblance between the dynamic and static deformation density distributions indicates little correlation between thermal motion and the deformation density. In order to see the effect of each multipole term on the de- formation density distribution, a multipole density map was produced at each step of expanding the multipole terms on all the atoms. It was obvious that, at least, all terms up to the quadrupole terms are needed for building up the density between the bonded atoms. Adding octapole terms certainly improved the density accumulation significantly. Additional hexadecapole terms on the C, N , and 0 atoms improved the density accumulation only slightly; however, this term was important for the sulfur atom. The net atomic charges from the EHMO calculation given in Figure 1 b are in agreement with the ones obtained by the multipole refinement. The deformation density based on the E H M O cal- culation only provides a qualitative comparison. The small basis (19) Busing, W. R.; Levy, H. A. Acta Crystallogr. 1964, 17, 142. (20) Wang, Y.; Blessing, R. H.; Ross, F.; Coppens, P. Acta Crystallogr.,

Sect. B Struct. Crystallogr. Cryst. Chem. 1976, 832, 512. (21) Wang, Y.; Liao, J. H. Acta Crystallogr., Sect. B Struct. Sci. 1989,

845, 65.

(22) Kring, M. P. C. M.; Graafsma, H.; Feil, D. Acta Crystallogr., Sect. E

Struct. Sci. 1988, B44. 609.

set calculations such as those with EHMO often underestimate the deformation density in the bonding regions but overestimate it in the lone-pair regions. A more sophisticated a b initio cal- culation of the title compound is underway.

Conclusion

Deformation density studies of thiourea dioxide, both by direct inspection of an experimental deformation density map and by construction of it according to a multipole model, lead to a better understanding of the atomic net charge distribution of the mol- ecule. The need of up to octapole terms for building up the density in the bonds is confirmed. The extra hexadecapole term is im- portant for the sulfur atom, which implies the angular complexity of the electronic distribution of sulfur atom in the molecule. The intermolecular H-bonding effect is observable in both the ex- perimental and model deformation density maps. Simple E H M O calculations can provide a qualitative comparison.

Acknowledgment. We wish to thank the National Science Council of the Republic of China for financial support. Thanks are also due to Professor Coppens for supplying the MOLLY pro- gram. We also express our appreciation to

Dr.

C. H. Ueng and Mr. G. H.

Lee

for their help on the low-temperature data collection and to Mr. H. C. Lin for software support.

Registry No. (H2N)2CS02, 41 89-44-0.

Supplementary Material Available: Tables SI-SIII, listing complete crystal data, atomic thermal parameters from various refinements, and coefficients of atomic multipole terms up to the hexadecapole level for non-hydrogen atoms and to the dipole level for hydrogen atoms (3 pages); Table SIV, listing calculated and observed structure factors (1 1 pages). Ordering information is given on any current masthead page.

Contribution from the Fachbereich Chemie, Universitat Dortmund, 4600 Dortmund, Federal Republic of Germany Head-Tail Oriented Nucleobases (B = Guanine, Cytosine) in cis-A,PtB, Resisting Cyanide Substitution. Implications for

the Nature of Strongly DNA-Bound Cisplatin Gudrun Frommer and Bernhard Lippert*

Received June 7, 1989

The adducts formed by the antitumor agent cis-diamminedi- chloroplatinum(II), cis-DDP (Cisplatin), with D N A cannot be completely removed even with excess cyanide.l Model nucleobase complexes of cis-DDP exhibit quite substantial differences in substitution rates when treated with CN-. These observations have led us to speculate that cross-links other than those between two guanines on one D N A strand (intrastrand G,G adduct) might account for this phenomenon.2 Specifically, the protective effect of the exocyclic oxygens of N3-bound thymine (and likewise uracil) ligands has been noted. It was suggested that the electron lone pairs of the carbonyl oxygens at either side of the Pt coordination plane in uracil and thymine complexes were responsible for this phenomenon. These oxygens are positioned such as to make an associative substitution mechanism difficult. In contrast, the two 9-ethylguanine (9-EtGH) ligands in cis-[(NH3)*Pt(9-EtGH-

A")2]2+,

which, in the solid state, are arranged head-head3 very

( I ) (a) Stone, P. J.; Kelman, A. D.; Sinex, F. M. Nature 1974, 251, 736. (b) Munchhausen, L. L.; Rahn, R. 0. Biochim. Biophys. Acta 1975, 414, 242. (c) Lippard, S. J.; Hoeschele, J. D. Proc. Natl. Acad. Sci. U.S.A. 1979, 76,6091. (d) Tullius, T. D.; Lippard, S. J. J . Am. Chem.

SOC. 1981, 103,4620. (e) Ushay, H. M.; Tullius, T. D.; Lippard, S. J. Biochemistry 1981, 20, 3744. (f) Bauer, W.; Gonias, S. L.; Kam, S.

K.; Wu, K. C.; Lippard, S. J. Biochemistry 1978,17, 1060. (g) Leng, M. Personal communication.

(2) Raudaschl-Sieber, G.; Lippert, 9. Inorg. Chem. 1985, 24, 2426. (3) (a) Lippert, B.; Raudaschl, G.; Lock, C. J . L.; Pilon, P. Inorg. Chim.

Acta 1984. 93, 43. (b) Schollhorn, H.; Raudaschl-Sieber, G . ; Muller, G.; Thewalt, U.; Lippert, B. J . A m . Chem. SOC. 1985, 107, 5932. 0020- 1669/90/ 1329-3259$02.50/0 0 1990 American Chemical Society

Downloaded by NATIONAL TAIWAN UNIV on August 20, 2009

數據

Table  11.  Atomic  Fractional Coordinates and B(eq)  (A2)
Figure  2.  Deformation density maps of  the  thiourea  plane  and  lane of  NN'S  (carbon atom  0.064  A  off  the  plane contour level):  0.1  e l l 3 ;   solid  lines  positive, dashed and dotted lines  zero  and negative
Table 111.  Least-Squares Results of  Multipole Refinements (Based  on  F)  NV"  R I b   R2b  R l w b   R k b   S  conventional  32  0.0286  0.0498  0.0522  0.0687  3.47  monopole  41  0.0240  0.0424  0.0373  0.0581  2.49  octapole  92  0.0181  0.0332

參考文獻

相關文件

— John Wanamaker I know that half my advertising is a waste of money, I just don’t know which half.. —

• Density is varying in the medium and the volume scattering properties at a point is the product of scattering properties at a point is the product of the density at that point

An n×n square is called an m–binary latin square if each row and column of it filled with exactly m “1”s and (n–m) “0”s. We are going to study the following question: Find

6 《中論·觀因緣品》,《佛藏要籍選刊》第 9 冊,上海古籍出版社 1994 年版,第 1

substance) is matter that has distinct properties and a composition that does not vary from sample

Murphy.Woodward.Stoltzfus.. 17) The pressure exerted by a column of liquid is equal to the product of the height of the column times the gravitational constant times the density of

S15 Expectation value of the total spin-squared operator h ˆ S 2 i for the ground state of cationic n-PP as a function of the chain length, calculated using KS-DFT with various

• elearning pilot scheme (Four True Light Schools): WIFI construction, iPad procurement, elearning school visit and teacher training, English starts the elearning lesson.. 2012 •