Inorg. Chem. 1981, 20, 335-342 Discussion It seems likely that when a solution containing the equilibrium mixture [RhCl(COCH3)L3]+ ~i [RhCl(CH3)(CO)L3]+is exposed to air, the dimethylphenylphosphine ligand trans to methyl dissociates and is oxidized irreversibly (Scheme I). The five-coordinate cation [RhCl(CH3)(CO)Ld+ so formed might reasonably be expected to dimerize to give a dicationic di-p-chloro complex containing six-coordinate rhodium(III), and this in turn could undergo methyl migration to give a dinuclear acetyl complex 2 containing five-coordinate rhodium(II1). The observed tri-p-chloro complex 1 presumably is formed by addition of C1- to 2, the chloride ion probably being derived either from that eliminated on reaction of RhC12(COCH3)L3with NH4PF6or from the dichloromethane solvent. The latter source is a possibility in view of the unexpected finding of 12dichloroethane in crystals of 1 ( R = CH3) grown from dichloromethane/methanol. Although we have not been able to isolate the di-p-chloro complex 2, Clark and Reimer26have reported the formation (26) Clark, H. C.; Reimer, K. J. Inorg. Chem. 1975,14, 2133-2139.
335
of the analogous di-p-bromo complex [ Rh2Br2(COCH3)2L4](PF6)2by treatment of 1 mol of RhBr2(CH3)(CO)L2with 1 mol of AgPF6. However, the reported IR (C=O) and 'H N M R data are sufficiently similar to those for our tri-pchloro complex as to suggest that the compound may in fact be the corresponding tri-p-bromo complex, formed by the reaction
-
2RhBr2(CH3)(CO)L3 + AgPF6 [Rh2Br3(COCH3)2L4]PF6+ AgBr Acknowledgment. W e thank Dr P. A. Tucker for helpful discussion. Registry NO. l.O.SC2H4C12, 75149-77-8; 2, 75149-79-0; RhC12(COCHJL,, 22605-70-5; RhC12(COC2HS)L,, 22605-71-6; [RhCl(C2H4)2]2, 12081-16-2;acetyl chloride, 75-36-5.
Supplementary Material Available: Listings of details of data collection (Table I), calculated phenyl hydrogen atom coordinates and isotropic thermal parameters (Table 11), structure factor amplitudes (Table HI), and bond distances and interbond angles of the phenyl rings (Table IV) (23 pages). Ordering information is given on any current masthead page.
Contribution from the Institute for Materials Research, McMaster University, Hamilton, Ontario, L8S 4M 1, Canada, and the Institute for Inorganic Chemistry, Technical University of Munich, 8046 Garching, Federal Republic of Germany
Crystal Structures of Two Crystalline Forms of Chloro- cis-diammine(1-methylcytosine-N3)platinum(11) Nitrate, [PtC1(NH3),(C5H7N3O)](NO3), and Their 'H NMR, IR, and Raman Spectra BERNHARD LIPPERT,I' COLIN JAMES LYNE LOCK,*lb and ROBERT ANTHONY SPERANZINIlb Received December 28, 1979 Chloro-cis-diammine(1-methylcytosine-N3)platinum(II)nitrate, [PtCI(NH3)2(C5H7N30)] (NO,), can be obtained in two monoclinic crystal forms: R l / c , u = 8.143 (2) A, b = 6.899 (1) A, c = 21.434 (3) A, B = 91.27 (2)", Z = 4; n / c , u = 13.155 (6) A, 6 = 9.754 (5) A, c = 19.097 (7) A, = 99.70 (3)", Z = 8. Data were collected for both crystals with use of Mo Ka radiation and a Syntex P21diffractometer. The crystal structures were determined by standard methods; that of the P2,/c crystal was refined to R I = 0.035 and R2 = 0.040 on the basis of 3018 reflections and that of the C2/c crystal to Rl = 0.047 and R2 = 0.064 on the basis of 1700 reflections. The cation, in both crystals, has a normal structure and bond lengths (Pt-N(ammonia) = 2.04 (1)-2.053 (8) A; Pt-N(3) = 2.026 (6), 2.06 (1) A; Pt-Cl = 2.299 (2), 2.300 (2) A). Both crystals contain a unit composed of two cations and two nitrate ions, both cations being hydrogen bonded to the same oxygen atom of a nitrate group through a proton on 4-NH2 of the cytosine ring. Thus both nitrate ions can be considered as bridging the two cations. The principal difference in the crystal packing is that in the P2,/c structure this two cation-two anion unit is essentially planar, whereas in the C2/c structure it is bent about the nitrate-nitrate axis. 'H NMR spectra of the two compounds in D20reveal a fast exchange of the C(5) proton of the 1-methylcytosineligand with deuterium ion upon heating. The corresponding C(5) deuterated 1-methylcytosinecomplexes have been isolated and studied by infrared spectroscopy. Introduction vestigate the stereochemistry of the interactions, and we routinely use X-ray crystallography to characterize the cis-Dichlorodiammineplatinum(I1)is a useful anticancer agent24 and is used in the treatment of testicular c a n ~ e r . ~ , ~products. It has been shown that, in vitro, the platinum complex interacts preferentially with the guanine- plus cytoThe drug's mode of action has been postulated to involve sine-rich areas of DNA,' and we have obtained and examined cross-linking of the two strands of DNA, thus interfering with a crystalline product of the type [Pt(NH3)2(9-ethylreplication, and there is experimental evidence that, in vivo, guanine)( 1-methylcytosine)] (C104)2.8 In order to make these the ability of cis-dichlorodiammineplatinum(I1)to cross-link mixed complexes, it is necessary to make products in which DNA is very much greater than that of trans-dichlorodione chlorine ion of ~ i s - P t c l * ( N Hhas ~ ) ~been replaced by a ammineplatinum(II), which has no anticancer activity.6 DNA base. Few, if any, of these complexes had been adeW e have been studying the interaction of cis-dichlorodiquately characterized although products in which one chloride ammineplatinum(I1) with various DNA bases in order to inion of K2PtC14had been replaced by a DNA base have been d e s ~ r i b e d . ~In J ~addition, complexes with one base attached ( I ) (a) Technical University of Munich. (b) McMaster University. (2) (a) Rosenberg, B. Plarinum Mer. Rev. 1971,15,42. (b) Clare, M. J.; Hoeschele, J. D. Ibid. 1973,17, 2. (c) Clare, M. J. Coord. Chem. Rev. 1974,12,349. (3) Roberts, J. J.; Thomson, A. J. Prog. Nucleic Acid Res. Mol. Biol. 1979, 22,71. (4) Cf. conference papers in Biochimie. (5) Einhorn, L. H.; Furnas, B. J . Clin. Hemafol. Oncol. 1977, 7, 662. (6) Roberts, J. J.; Pascoe, J. M. Nature (London) 1972,235,282.
0020-1669/81/1320-0335$01.00/0
(7) Stone, P. J.; Kelman, A. D.; Sinex, F. M. Narure (London) 1974,251, 736. (8) Lippert, B.; Lock, C. J. L.; Speranzini, R. A., unpublished work. (9) Terzis, A,; Hadjiliadis, N.; Rivest, R.; Theophanides, T. Inorg. Chim. Acra 1975,12,L5. (10) Kong, P. C.; Rochon, F. D. J . Chem. Soc., Chem. Commun. 1975,599.
0 1981 American Chemical Society
336 Inorganic Chemistry, Vol. 20, No. 2, 1981 to the trans-dichloro(organic sulfoxide-S)platinum(II) moiety have been described."-13 In preparing the guanine-cytosine complex referred to above,* we have prepared and characterized chloro-cis-diammine(1-methylcytosine-N3)platinum(11) nitrate. It exists in two different crystal forms with different space groups but, as expected, in a single form in solution. In D20solution the C(5) proton of the coordinated l-methylcytosine ligand is exchanged against a deuterium ion when the complex is heated. We describe the work here. Experimental Section Chloro-cis-diammine( 1-methylcytosine-N3)platinum( 11) nitrate, C~S-[P~C~(NH~)~(C~H~N~O)]NO~, was prepared in two ways described subsequently. Usually a mixture of forms A (needles, space group P2,/c) and B (roughly cubic parallelepipeds, space group C 2 / c ) was obtained and the crystals were separated by hand. It appeared that temperature and slowness of the crystallization process were the important parameters in deciding which product was formed predominantly. Rapid cooling and fast evaporation at room temperature (large surface) yielded predominantly or even exclusively the A product, whereas slow evaporation at +4-+7 "C gave B as the major product. Addition of crystals of either A or B to a concentrated solution of the compound and subsequent cooling yielded the desired product in high yield. Ways of Preparation (a) c i ~ - P t ( N H ~ )(0.6 ~ c lg)~ was reacted with 1 equiv of AgN03 in water (0.338 g, 30 mL). The precipitated silver chloride was removed by filtration, and the resulting solution was reacted with I-methylcytosine (0.25 g) in water for 24 h a t 45 "C. The resultant solution was then concentrated to IO-mL volume by rotary evaporation and cooled to +4 "C. After 2 days, a small amount of ~ i s - P t ( N H ~ )(~- 5c l ~ mg) was filtered off. After 12 days, a large amount of precipitate was collected from the brownish purple solution. It consisted of 300 mg of the C2/c product, small amounts of cisPt(NH3)2C12,and two other unidentified compounds (together -30 mg). ~ i s - P t ( N H ~ )was ~ c lremoved ~ by extraction with dimethylformamide and the product recrystallized from water. Depending upon the conditions of crystallization, either A or B as major products were obtained. (b) This procedure involved the preparation of ~ i s - [ P t c l ( N H ~ ) ~ (CSH7N30)]C1-H2014 from ~ i s - P t ( N H ~ )and ~ c l1~-methylcytosine (3 g of ~ i s - P t ( N H ~ ) ~1.25 c l ~g,of 1-methylcytasine, 500 mL of H 2 0 , 36 h, 40 "C, stoppered flask concentration to 5@mLvolume, filtration of unreacted ~ i s - P t ( N H ~ ) ~slow c l ~evaporation , at 22 "C; yield 1.6 g plus other products; recrystallization from H20) and subsequent reaction of the isolated crystalline product (0.333 g, 10 mL of H 2 0 ) with AgN03 (0.127 g, 10 mL of H20). Silver chloride was removed by filtration and the product crystallized at 22 OC: main product A, yield 90%. Recrystallization from water yielded A or B as major products depending on the conditions of crystallization. Anal. Calcd for A: C, 13.3; H, 2.9; N, 18.6; Pt, 43.2; 0, 14.2. Found: C, 13.4; H, 3.0; N, 18.7; Pt, 43.6; 0, 14.9. Calcd for B: C, 13.3; H , 2.9; N, 18.6; Pt, 43.2; 0, 14.2. Found: C, 13.4; H, 2.9; N, 18.0; Pt, 43.1. Prolonged heating of chloro-cis-diammine( 1-methylcytosine-p)platinum(I1) nitrate in water (>0.5 h, 80-90 "C, 100 mg, 5 mL, stoppered or open flask) led to formation of a purple or blue solution. During this process, the pH was dropping (from - 5 to -3 after 2 h a t 90 "C). From the concentrated solution, the starting material was recovered in 60-70% yield. The crystals were blue, but two cautious recrystallizations from water (22 "C) yielded almost colorless crystals of the starting compound(s). Deuterated Compounds. 1-Methylcytosine (ND,) was prepared by heating for 0.5 h a t 90 "C 1-methylcytosine in D 2 0 (250 mg, 5 mL) and crystallization at 22 OC. The "fully" deuterated analogues (ND2, (ND3)2, C(5)D) of A and B were obtained by heating cis- [PtCI(NH3)2(CSH7N30)]N03 (200 mg, 4 mL of D20) in a stoppered flask for 3 h in a 90 "C water bath and appropriate crystallization of the resulting blue solution (cf. (11) Lock, C. J. L.; Speranzini, R. A.; Powell, J. Can. J . Chem. 1976, 54, 51
(12) Lock, C. J. L.; Speranzini, R. A,; Turner, G.; Powell, J. J . Am. Chem. Soc. 1976, 98, 7865. (13) Melanson, R.; Rochon, F. D. Inorg. Chem. 1978, 17, 619. (14) Lippert, B.; Lock, C. J. L., unpublished work (refers to cis-[a2Pt(Cyto)Cl]Cl*HIO).
Lippert, Lock, and Speranzini
Figure 1. The molecular cation [Pt(NH3)2(CSH7N30)C1]+ (P2,/c structure). preceding section). The partially deuterated compounds ((ND,),, C(5)D) were obtained by dissolving the fully deuterated compounds in H 2 0 at room temperature and subsequent crystallization. The partially deuterated compounds (C(5)D) were obtained by three cycles of brief warming (60 "C, 25 min) of the fully deuterated compounds in H 2 0 and subsequent crystallization. Apparatus. 'H N M R spectra were recorded on a Varian EM360 spectrometer at 60 MHz. Tetramethylsilane was used as external reference. Infrared spectra were recorded on a Perkin-Elmer 580 grating spectrometer as Nujol mulls with CsI windows and as KBr disks. No differences were observed between KBr and Nujol spectra. The reported frequencies were measured on an expanded scale with 1.3-cm-' maximum resolution, calibration against polystyrene. IR intensities: vw = very weak, w = weak, m = medium, s = strong, vs = very strong, sh = shoulder, b = broad. Raman spectra of solid samples were recorded on a Coderg PH1 spectrometer with a krypton laser (647.1-nm excitation), calibration against indene. Both compounds A and B showed severe decomposition in the laser beam. This required fast scanning and consequently larger slit width (6 cm-I). Collection of the X-ray Data. Crystals of the two compounds were selected after examination under the polarizing microscope for homogeneity. Precession photographs showed both crystals were monoclinic, one with the systematic absences of P2,/c and the other with those of C2/c or Cc. For the second crystal the space group C2/c was assumed and justified by the satisfactory solution of the structure. Unit cell parameters were obtained from a least-squares fit of x , 4, and 20 for 15 reflections for each compound in the range 20" < 20 < 35" recorded on a Syntex P21diffractometer using Mo K a radiation h = 0.71069 A at 22 "C. Crystal data and other numbers related to data collection are summarized in Table I. Densities were obtained by flotation in a diiodomethane-chloroform mixture. Intensity data were also recorded on the Syntex P2' diffractometer using a coupled 0(crystal)-20(counter)scan. The methods of selection of scan rates and initial data treatment have been des~ribed.l~3'~ Corrections were made for Lorentz-polarization effects and absorption. Solution of the Structure. Both structures were solved in the same way. The coordinates of the platinum atom were found from a three-dimensional Patterson synthesis, and a series of full-matrix least-squares refinements followed by three-dimensional electron density difference syntheses revealed all the nonhydrogen atoms. At this stage the temperature factors of the platinum and chlorine atoms, which were previously isotropic, were made anisotropic. Tests were made at each stage to show the use of the increased parameters was significant." Further refinement using full-matrix least squares minimizing x.w(lFoI was terminated when the maximum shift/error was about 0.05. Cruickshank weighting schemes were used and corrections were made for secondary extinction with use of the method of Larson.'* Throughout the refinement, the scattering curves were taken from ref 19 and anomalous dispersion corrections from ref 20 were applied to the curves for platinum and chlorine. The atom parameters for nonhydrogen atoms are listed in Tables I1 and IIL2' (15) Hughes, R.P.;Krishnamachari, N.; Lock, C. J. L.; Powell, J.; Turner, G . Inorg. Chem. 1977, 16, 314. (16) Lippert, B.; Lock, C. J. L.; Rosenberg, B.; Zvagulis, M.Inorg. Chem. 1978, 17, 2911. (17) Hamilton, W. C. Acta Crystallogr. 1965, 18, 502. (18) Larson, A. C. Acta Crystallogr. 1967, 23, 664. (19) Cromer, D. T. "International Tables for X-ray Crystallography"; Ibers, J. A., Hamilton, W. C., Eds.;Kynoch Press: Birmingham, England, 1964; Vol. IV, Table 2.3.1, p 149. (20) Cromer, D. T.; Waber, J. T. Reference 18, Table 2.2A, p 72 ff.
Inorganic Chemistry, Vol. 20, No. 2, I981 337 Table I compd fw cryst size
1203.8 (9) A' 4 2.492 g cm-' 2.47 (2) g cm-3 123.0 cm-' 4.03-4.33 55"; h, k, tl (1) 106; (2) 2,-1,6 (1) 1.16%; (2) 1.12% 22 "C 301 8 2168 135 187 528 0.0349 0.0396 0.035 (0.006) 2.23 x 10-7
C, HI,ClN, 0,Pt 45 1.6 polyhedron with faces: {OlO}, 0.10 mm apart; 110 a n d f i 0 , 0.11 mm apart; 110 and 110,O.lO mm apart hkl,h + k = 2 n + l;hOl,I=2n + 1 C2/c (No. 15) u = 13.155 (6) A, b = 9.754 (5) A, c = 19.097 (7) A, p = 99.70 (3)' 2415 (2) A' 8 2.484 g cm-' 2.47 (2) g cm-' 123.0 c m - I 1.93-3.96 45"; h,k, *I (1) 317; (2) 006; (3) 204 (1) 1.96%; (2) 1.93%; (3) 2.08% 22 "C 1700 1344 61 81 214 0.0467 0.0641 0.057 (0.006) 7.32 X lo-'
1.35 e/A3; 0.40, -0.08,0.16 -1.11 e/A3; 0.20, 0.10,0.31 l / w = 10.7 - 0.1541FoI + 0.001 05 lFo12
1.47 e/A3; 0.20,0.30, 0.26 -1.85 e/A3;0.15, 0.12, 0.27 l/w = 34.6 - 0.293 lFoI + 0.003 39 IFo12
C5H13Cw604Pt
451.6 cylinder, r = 0.075 mm, I = 0.40 mm OkO,k=2n
systematic absences space group unit cell parameters
+ l;hOl,I=2n + 1
P2,/c (No. 14) u = 8.143 (2) A, b = 6.899 (1) A, c = 21.434 (3) A, p = 91.27 (2)"
V Z
Pcalcd Pobsd
linear abs coeff transmission coeff limits max 213; quadrant std reflctns overall esd temp no. of independent reflctns no. withZ > 3 4 4 3 4 4 > I > 00where Fc > Fo 3~(I)>Z>0(l)whereF,
