VoZ. 6, No. 4 , April 1967
CRYSTAL
under the trans effect of the amine group in [Pt(dien)XI+, and i t would be desirable to see to what extent this behavior is changed when a strong trans-effect ligand is present.
STRUCTURE O F
ck-Pt [P(CHa)a]zC11 7 2 5
Acknowledgment.-This work was supported by the Italian Consiglio Nazionale delle Ricerche (CNR, Rome). We wish to thank professor M. L. Tobe for reading the final manuscript.
CONTRIBUTION FROM THE DEPARTMENTS O F CHEbIISTRY, UNIVERSITY O F SOUTH CAROLINA, COLUMBIA, SOUTH CAROLINA29208, AND NORTHWESTERN UNIVERSITY, EVANSTON, ILLINOIS 60201
Crystal Structure of cis-Pt [P(CH,),],Cl, BY G. G. MESSMEK,' E. L. ~ L M M AAND , ~ JAMES A. IBEKS Received October 3 , 1966 The crystal structure of cis-Pt JP(CH3)8]Z C ~has Z bcen determined from counter data by three-dimensional single-crystal X-ray diffraction techniques. Unit cell constants are: Q = 16.67 & 0.02 A, b = 11.93 f 0.02 A, c = 6.33 f 0.01 A, p = 91" 25' f 15'. The space group is B21. The structure is made up of discrete molecular units with ordinary van der Waals separations. The asymmetric unit is one molecule with Pt-P distances of 2.256 and 2.239 A (both fO.008 A) and Pt-Cl distances of 2.364 and 2.388 A (both f0.008 A ) . The molecule is twisted toward a tetrahedral configuration with nearest neighbors of platinum displaced about 0.1 A out of the best least-squares plane defined by the platinum and its four nearest neighbors. These bond lengths are to be compared with Pt-P distances of 2.298 f 0.018 and 2.315 & 0.004 A and Pt-X ~ Z t r ~ n s - P t [ P ( C ~ H ~ ) ~respectively. ]~Brz, distances of 2.294 f 0.009 and 2.428 f 0.002 A observed in trans-Pt[P( C Z H & ] ~ Cand analysis because the crystals were most easily aligned about the c axis of the B-centered cell. All our intensity data were collected with this axis vertical on the diffractometer, and this orientation facilitated comparison with our previous photographic structure determination.T Further, the p angle for the Bcentered cell is approximately 90". With four molecular entities in the B-centered cell, the calculated density was found t o be 2.16 g compared with the observed of 2.18 g cm-z obtained by flotation in carbon tetrachloride-bromoform mixtures. (This corresponds to two molecules in the primitive cell ,) A single crystzl, 0.20 X 0.15 X 0.15 mm, mounted on a GE single-crystal orienter with a Picker diffractometer using Zrfiltered Mo Kcu radiation was used to measure 2433 independent hkl intensity data by a scanning technique a t room temperature. Background was estimated by stationary counting a t 10.8'' 28 from the peak maxima for 10 sec. The peak was then scanned for 40 sec with a 20 scan. The integrated intensity was obExperimental Section tained by subtracting the background scaled to 20 sec from Crystals of cis-Pt[P(CzH;)3]&1~and ~ i s - P t [ P ( C H ~ \ ~ l were ~Cle the 20 scan. The value of the linear absorption coefficient ( p ) kindly provided to us by Professor J. Chatt. c ~ s - P ~ [ P ( C ~ H ~ )for ~ ] Mo ~ - Ka radiation is 132 cm-'. No corrections were made for C ~ was Z found to have a large triclinic cell, and this structure absorption and, consequently, no detailed physical interpretadetermination was abandoned. Crystals of c ~ s - P ~ [ P ( C H ~ ) ~tion ] ~ - should be made of the anisotropic temperature factors. Clz were found to be monoclinic with unit cell constants from Recently Srivastava and Lingafelter* have shown that absorption calibrated precession photographs: a = 16.67 i. 0.02 A, b = = 191 cm-l do not appreciably affect atomic effects with 11.93 i. 0.02 A, c = 6.33 f 0.01 A, and p = 91' 25' f 15' coordinates; hence, we feel our estimates of error in atomic co(Mo Kcu, X 0.7107 A). The systematic extinctions observed ordinates are realistic. Corrections were made for anomalous were: for hkl, h 1 = Yn 1; for OkO, k = 2n .f1. The dispersion (see below). possible space groups with these extinctions are B2, or B21/m. With a reorientation of the a and c axes, these would correspond Structure Determination t o the more common P21 or P21/m.G The structure analysis 'In space group B21 with four molecules per unit established the correct space group as B21 or PZ1 (vide injm). cell, all atoms would be in the general positions: (0, 0, We retained the use of the B-centered cell for the structure (x,y, z; 2, ' / z y,E ) . In space group 0 ; '/z, 0, l/z)
Introduction We have completed crystal structure determinations of trans-Pt[P(C2H5)3I2X2,X = C1 and Br, and found substantially shorter Pt-P bond lengths than would be predicted from a sum of covalent radiL3r4 However, the Pt-X bonds were found to be normal single bonds, equal to the sum of the single-bond covalent radii. Hence, Pt-X (X = C1, Br) and Pt-P distances have been carefully determined in the X-Pt-X and P-Pt-P atomic arrangements. To substantiate the thermodynamic results of Chatt and Wilkens5 in terms of bond lengths, we undertook to solve the crystal structure of cis-Pt [P (CH3)3]zC12.
+
+
+
(1) I n partial fulfillment for the Ph.D. requirements, University of Pittsburgh. (2) Address all correspondence to this author: Department of Chemistry, University of South Carolina, Columbia, S. C. 29208 (3) G. G. Messmer and E. L. Amma, Inoug. Chem., 6, 1775 (1966). (4) For a more complete introduction and references, see preceding paper. a (5) J. Chatt and R. G. Wilkens, J . Chem. Soc., 273,4300 (1952); 70 (1953); 525 (1956). (6) "International Tables for X-ray Crystallography," Vol. I, T h e Kynoch Press, Birmingham, England, 1952, pp 79,93.
+
B21/m: (a) the Pt, 2P, 2C1, and one of the three carbon atoms on each phosphorus could lie in the mirror plane a t y = '/4: (0, 0, 0 ; l/z, 0, l/z) (x,'/4, z; 2, 3/4, E ) and the remaining carbon atoms in the general positions (0, 0, 0 ; l / Z , 0 , l/2) ( x , y, z; R, 7 )2.; x, '/Z y,z; 2, '/z y, E ) ; (b) the Pt could lie in the mirror
+
+
+
(7) P. D. Carfagna and E. L. Amma, unpublished results. (8) R. C. Srivastava a n d E. C. Lingafelter, Acta Ciyst., 20, 918 (1960).
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plane and the other atoms in the general positions; (c) all other special positions in this space group are centers of symmetry, and the asymmetric cis molecule could not be placed a t a center of symmetry. The occurrence of a number of substantial peaks in the three-dimensional Patterson a t y # 0, l / Z rules out possibility (a) in B21/m. The existence of a large peak a t y = 0 that can be most readily assigned to a Pt-Cl(P) interaction in the Patterson rules out possibility (b) of B21/m, and therefore the correct space group is B21. The structure was solved and refined on this basis. The Pt, P, and C1 atoms were located from the threedimensional Patterson vector maps. The carbon atoms were located from three-dimensional electron density and difference electron density maps.9 The structure was refined by full-matrix least squares including anisotropic temperature factors : (a) without dispersion corrections, (b) with only the real part of the dispersion correction, and (c) with real and imaginary dispersion corrections. The function minimized was Zw (Fo - Fc)2. The observations were weighted on counting statistics and a 4y0 intensity factor.I4 Atomic co(9) Fourier programs are due to Sly, Shoemaker, and van den Hende for the IBM 7090. (10) Least-squares refinement performed with ORBLS of W. Busing, K. 0. Martin, and H. Levy as modified by Ibers for inclusion of anomalous dispersion. We are grateful to Professor L. Dah1 and the University of Wisconsin for the CDC 1604 time to perform some of these calculations. (11) Anomalous dispersion corrections made to F , as suggested by: J. A. Ibers and W. C. Hamilton, Acta Cuyst., 17, 781 (1964). (12) (a) Scattering factors for neutral CI, P, and C from: J. A. Ibers, “International Tables for X-Ray Crystallography,” Vol. 111, The Kynoch Press, Birmingham, England, 1962, p 202; (b) scattering factor for neutral Pt from: D. T. Cromer and J. T. Waber, Acta Cuysl., 18, 104 (1965). (13) Real and imaginary dispersion corrections applied to Pt, P, and C1 from: D. T . Cromer, ibzd., 18, 17 (1965).
CRYSTAL
STRUCTURE OF c&-Pt[P(CH3)3]zClz 727
ordinate shifts for the final least-squares cycle were less than 4 X of a cell edge for Pt, P, and C1 and less than 4 X for carbon. The final disagreement index R15 and the weighted R for refinements a-c were found to be: 0.100, 0.120; 0.101, 0.120; and 0.097, 0.115, respectively. A final difference map appeared qualitatively clean and showed no unusual features. Final calculated and observed structure factors from the refinement, including dispersion corrections, are listed in Table I. Table I1 contains atomic parameters and errors, and Table I11 shows interatomic distances, angles, and errors,16 as well as the best least-squares plane through Pt, P, and CI.” We are disappointed that the disagreement index is not lower, but some improvement could be obtained by neglecting a number of reflections that are obviously in error due to extinction. This relatively high disagreement index may also reflect the neglect of absorption corrections. It is readily shown that in an acentric space group where the effects of anomalous dispersion are important Friedel’s law fails. I n particular, in P21 (B2,) F2(hkZ) is no longer equal to F2(h&) and it is necessary to test both possibilities if a complete data set is not available. The test is equivalent to refining two structures: structure 1 has the coordinates as given in Table 11; structure 2 has essentially the same x and z coordinates but with the y reversed in sign. We carried out both calculations and have rejected structure 2 on the following grounds: (A) The structure obtained does not make chemical sense in that two distinctly different Pt-P and Pt-Cl distances result (Pt-P, 2.201 f 0.008, 2.244 f 0.005 A; Pt-Cl, 2.370 f 0.007, 2.423 f 0.00s A). This arises from a shift of the Pt atom relative to the X-ray source. Templeton, Zalkin, and Uekil* have recently noted this effect in their study of thorium nitrate pentahydrate. (B) Structure 2 refines to a weighted R factor of 0.121. If this is tested using ha milt on'^'^ R-factor test as a hypothesis of one degree of freedom, then structure 2 can be rejected a t the 0.5% confidence level.
Results and Discussion The crystal structure of cis-Pt [P(CH&]& is made up of discrete molecular units separated by ordinary van der Waals distances (Figures 1 and 2). The average Pt-P distance of 2.247 A (2.256 =t0.008, 2.239 f 0.006 A) is significantly different from the 2.135 f 0.004 and 2.300 f 0.019 A Pt-P distances observed in transPt [P(C2H6)3]2Br2and trans-Pt [P(C2H5)3]2CIzr respectively. However, a Pt-P distance of 2.267 0.008 A has been observed in trans-Pt [P(CeH&C2Hj]2HCI by Eisenberg and IbersZ0 These numbers indicate that Pt-P distances may be as sensitive to substituents on the phosphorus as they are to trans substituents on the metal
*
(14) S. W. Peterson and H. A. Levy, i b d , 10, 70 (1957). (15) R = Z l / F , / - ~ F o ~ ~ / Z ~Weighted F o ~ . R = [Zu(F,
-
F0)211/2/
[ZWF02]1k
(16) Distances, angles, and errors were calculated with W. Busing, K . 0. Martin, and H. A. Levy, ORPBE. (17) W. C. Hamilton, Acta Cuyst., 14, 185 (1961). (18) T. Ueki, A. Zalkin, and D. H. Templeton, i b i d . , 20, 836 (1966). (19) W. C. Hamilton, ibid., 18, 502 (1965). (20) R. Eisenberg and J. A. Ibers, Inorg. Chem., 4, 773 (1965).
728 G. G . MESSMER, E. L. AMR.IA,AND J m m A. IBERS
Inovganic Chemistry
TABLE 11 klCJ.\.rI’OSITIONAL
Atom
I’t c11 P1 CIS
Pz
c1 C2 C3 c 4
CS c 6
AND TEhlPURATURE 1’ARAAIETERs A S D
ERRORS;” u’
rln
u‘(x/n)
y/b
u‘blb)
0,4066 0.5351 0.4521 0.3578 0.2825 0.5556 0.4514 0.3961 0.2543 0.2039 0,2557
4 43 39 55 27 224 209 249 180 106 71
- 0,5000 -0.5359 -0.3451 - 0,6533 -0.4950 -0.3032 -0.3507 -0,2194 - 0.4076 -0.4606 -0.6306
. . .1,
= u
x
1 ZiC
u’(z/c)
0.7008 0.8323 0.5378 0,9034 0.5574 0.5875 0.2500 0.6115 0.3343 0,7485 0.4334
68 65
i7 102 353 344 238 275 221 177
12 153 125 146 93 746 528 679 583 424 627
Thermal Paramctcrs and Standard Deviations; Anisotropic Teniperature Factors of the Form C.XP[-(@11h2 2&2hk 2R13hZ 2 ~ ~ ~ k; i j l= x 105 P2zk2 13sP
+
Atom
U’
(311
2 0.0021 21 0.0027 19 P1 0.0022 35 Clp 0.0049 12 Pa 0.0018 142 Ci 0 0038 127 Ca 0.0048 182 Cj 0.0073 97 Cq 0.0032 46 cg 0 0012 (26 0.0036 95 a With real and imaginary Pt C11
PA2
U‘
+
+
Pa3
+
+
e‘
PI2
0.0040 5 0.0152 20 0.0006 0,0067 49 257 0 0321 0.0010 202 0 0052 45 0 0217 -0.0006 247 0.0064 0 0275 55 0.0002 145 0 0040 31 0 0193 0.0004 0,00i7 1556 280 0 0478 -0.0017 0,0091 815 282 0 0166 0.0010 0.0023 1156 147 0 0386 0.0006 0.0048 1125 0 0354 191 0.0005 0.0065 169 0 0251 0.0008 709 1229 0.0021 101 0 0510 -0.0012 dispersion corrections. Parameter fixed.
U’
013
4 26 24 36 35 167 160 131 112 71 i7
0.0001 -0,0031 0.0014 0,0019 -0,0008 -0.0050 0,0042 0.0071 -0,0046: 0.0040 0.0011
U’
4 62
47 73 32 404 254 364 276 149 268
U‘
Pi3
-0.0010 -0.0012 -0,0011 0.0054 - 0.0034 0.0055 0.0031 - 0.0021 0.0020 - 0.0040 -0.0027
1(i 87
77 97 129 559 393 339 316 278 296
TABLE I11 INTERSTOXIC DISTANCES, ANGLES,ASD E R R O RFOR S ~ cis-l’t[P( CHJ)a]2C12
I. Intramolecular Bonded, A
Pt-Cl1 Pt-Cl2 Pt-Pt 1%-Pa
2 3G4 f 0 2.388f 0 2 256 zt 0 2 239 zt 0
Nonboiided, A
008 009 008 006
P--Cl~ P-Cl1 P-Clp Pz-cll PI-1’2
P1-Cl P1-c2
P1-Ca P2-c4
P2-C6 P2-c6
X-Pt-X P1-Pt-Pz Cl1-Pt-Cl2 Cl1-Pt-P1 Cl2-Pt-Pa P1-Pt-Cly Pp-Pt-c11
7 -
1 818 f 0 034 1 822 rt 0 035 1 833 f 0 029 1 809 =I= 0 033 1 851 f 0 019 1 849 f 0 024 angles, deg--
9 6 . 2 i: 0 . 4 87.7 f 0 . 3 91.3f0.3 85.1i0 . 4 1 7 4 . 5 i: 0 . 3 1 7 1 . 1f 0 . 4
C11-Clr
cs-c2 c1-c3 c2-c3
C4-c: 7---Pt-P-C
Pt-P1-C1 Pt-P1-P2 Pt-P1-C3 Pt-P2-C4 T’t-Pp-CD Pt-Pz-Cs
3 3 4 4 3 3
Nonlmiidecl, A
304 f 0 012 131 =t0 013 6 3 9 3 ~0.013 593 =!= 0 008 350 rt 0 011 293 f 0 013
2.78 2.85 2.94 2.84
cj-cs
2.73 4.2 0 . 0 4 2.99 f 0 . 0 4
GC1, C2-Cl1 Cs-Cls C;--Cl*
3 27 f 0.04 4 59 f 0 03 3 . 4 0 f 0 04 3.56 f 0 03
cq-
f 0.05 f0.06 zt 0 . 0 5 zt 0 . 0 5
3.81 f 0 . 0 4 3.59 f 0.03 4.59 f 0 . 0 2 7---C-P-C
angles, deg-------
118.4 f 1 . 3 115.if0 . 4 112.Of 1.1 123.5+ 1.1 1 1 3 . i f i1.8 111.1 f 1 . 1
CI-Pl-cP Cl-Pl-Ca c?-PI-C3 C4-P2-C5 Ca-Pa-Ce C3-Pa-Ca
angles, deg----------.
9 9 . 5 =k 2 . 0 1 0 2 . 5 12 . 0 107.1f 1 . 9 102.0 i: 1 . 5 96.8i1 . 8 1 0 7 . i f 1.3
11, Iiitermolecular Shortest Pt-Pt, 6.326 A All intermolecular distances are equal to or greater than normal van der Waals distances with van der VvTaals radii of C1 and CH3 = 2 . 0 A.
+
+
=
1.80 .I
Deviation of Pt, P, and C1 from Best Least-Squares Plane,b aX bY CZ - d = 0 a = $4.717 Pt, +O 0002 f 0 006 A b = -6 971 C11, +O 1209 rt 0 009 X c = -4.857 Clz, -0 1451 f 0 010 x Pn, +0.0763 i 0 007 il d = $2.000 Pi, -0 0726 f 0 008 A With real and iniaginarp dispersion corrections. Positional staiidard deviations a e r c used to provide weights for the least-squares plane. X , Y , arid 2 refer to thc inoiioclinic coordiiiate system.
VoL. 6 , No. 4, April 1967
Figure 1.-Perspective
CRYSTAL STRUCTURE OF cis-Pt LP(CH3)3]2C12729
view of t h e structure of cis-Pt[P(CH~)a]zCl~ looking in the direction of negative c . CZis superposed in this view by PI.
Figure 2.-Perspective view of the structure of cis-Pt[P(CH~)3]2C12in the direction of positive b. For orientation purposes the “large” molecule approximately in the center in this view corresponds to the molecule approximately in the center of the cell in Figure 1.
atom. A Pt-P “normal” single-bond lengthz1of 2.41 A would be expected from covalent radii. The average Pt-C1 distance of 2.376 A (2.364 f 0.008, 2.388 + 0.009 A) is significantly longer than the Pt-CI distance (21) L. Pauling, “Nature of the Chemical Bond,” 3rd ed, Cornell University Press, Ithaca, N. Y.,1960, p 246.
of 2.294 i 0.009 A in the trans isomer which is a “normal” single Pt-C1 bond. The Pt-Br distance of 2.428 f 0.002 A in trans-Pt[P(C2HS)3]Br2 is also a “normal” Pt-X single bond. This 2.376 A distance is to be compared with the Pt-CI distances of 2.422 f 0.009 A observed by Eisenberg and IbersZ0and 2.42 A by Wun-
730
PING-KAY HON,
c. E.h ” U G E K ,
AND
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