Inorganic Chemistry, Vol. 15, No. 10, 1976 2455
Nature of Pt Chain Distortion in K1.75Pt(CN)plSH20 Fourier summation, FORDAP; least-squares refinement, OR XLFS3; error analysis of distances and angles, OR FbE3, and structural drawings, OR TEPII. For determination of least-squares planes the program PLNJO was used; J.-0. Lundgren, University of Uppsala, Uppsala, Sweden; based on the method of D. Blow, Acta Crystallogr., 13, 168 (1960). For the intensity statistics MULTAN was used; J, P. Declercq, G. Germain, P. Main, and M. M. Woolfson, Acta Crystallogr., Sect. A , 29, 231 (1973). The Delauney-reduced cell parameters were derived using the computer program TRACER 11, A Fortran Lattice Transformation-Cell Reduction Program, written by Dr. S. L. Lawton. (17) P. Day and J. Hines, Operating Systems Rev., 7, 28 (1973). (18) S. W. Peterson and H. A. Levy, Acta Crystallogr., 10, 70 (1957). (19) (a) The Zachariasen approximationigb was used for the overall isotropic g parameter as defined and scaled by Coppens and Hami1t0n.l~~ The lFol value: were corrected for extinction from the expression lFolcorr = IF,I(l + ?2gX31Fc12/~sin where lFcl is on an absolute scale, X is the wavelength (A), g is the refined extinction parameter, Fis the mean absorption-weighted path length in the crystal in centimeters (calculated simultaneously during the computation of absorption corrections), and Vis the unit cell volume (A3). (b) W. H. Zachariasen, Acta Crystallogr., 23,558 (1967). (c) P. Coppens and W. C. Hamilton, (20) (21) (22) (23)
Acta Crystallogr., Sect. A , 26, 71 (1970). G. E. Bacon, Acta Crystallogr., Sect. A , 8, 357 (1972). M. L. Moreau-Colin, Bull. SOC.Fr. Mineral. Cristallogr., 91,332 (1968). K. Krogmann, Angew Chem., Int. Ed. Engl., 8, 35 1969). Some very short Pt-Pt separations are: (a) 2.58 ( ) A in [Pt3(C8Hl2)3(SnC13)2], L. J. Guggenberger, Chem. Commun., 512 (1968); (b) 2.581 8, in [Pt2("-C~H5)4], K. K. Cheung, R. J. Cross, K. P. Forrest, R. Wardle, and M. Mercer, Chem. Commun., 875 (1971); (c) 2.675
\
(24) (25) (26)
(1) A in Pt3[P(C6H11)3]4(C0)3,A. Albiriati, G. Carturan, and A. Musco, Inorg. Chim. Acta, 16, L3-L4 (1976); '(d) 2.647 8, in [Pt?S(CO)iPPh3)3], A. C. Skapski and P. G. H. Troughton, J . Chem. S o t . A , 2772 (1969); and (e) J. M. Williams, Inorg. Nucl. Chem. Lett., 12, 651 (1976). P. L. Johnson, T. R. Koch, J. A. Abys, and J. M. Williams, to be published. K. Krogmann, ACS Symp. Ser., 5, (1974). J. Bernasconi, P. Bruesch, D. Kuse, and H. R. Zeller, J . Phys. Chem. Solids, 35, 145 (1974). R. L. Musselman, T. R. Koch, and J. M. Williams, to be published.
(27) (28) T. W, Thomas, C.-H. Hsu, M. M. Labes, P. S. Gomm, A. E. Underhill, and D. M. Watkins, J . Chem. SOC.,Dalton Trans., 2050 (1972). (29) K. Carneiro, J. Eckert, G. Shirane, and J. M. Williams, Solid State Commun., in press. (30) A. J. Schultz, G. D. Stucky, and J. M. Williams, to be published. (31) R. Comes, M. Lambert, H. Launois, and H. R. Zeller, Phys. Reu. B, 8, 571 (1973); R. Comes, M. Lambert, and H. R. Zeller, Phys. Status Solidi B, 58, 587 (1973). (32) L. Pauling, "The Nature of the Chemical Bond", 3d ed,Cornell University Press, Ithaca, N.Y., 1960. (33) J. R. Ferraro, L. J. Basile, and J. M. Williams. J. Chem. Phvs.. 64. 732
(1976).
(34) D. Cahen and J. E. Lester, Chem. Phys. Lett., 18, 108 (1973). (35) M. A. Butler, D. L. Rousseau, and D. N. E. Buchanan, Phys. Reu. B, 7, 61 (1973). (36) P. L. Johnson, T. R. Koch, and J. M. Williams, to be published. (37) C. F. Eagen, S. A. Werner, and R. B. Saillant, Phys. Reo. B, 12, 2036 (1975). Note that the charge density wave distortions in KCP(Br) are
small and the rigid sinusoidaldisplacement of the Pt(CN)4-2 groups (at 7 K) amounts to only 0.026 A.
Contribution from the Chemistry Division, Argonne National Laboratory, Argonne, Illinois 60439, and the Webster Research Center, Xerox Corporation, Webster, New York 14580
The Nature of the Pt Chain Distortion in the Partially Oxidized One-Dimensional Complex, K 1 . 7 5 P t ( C N ) 4 - 1 . 5 H 2 0 1 A. H. REIS, Jr., S. W. PETERSON,* D. M. WASHECHECK,* and JOEL S. MILLER3
Received March 22, 1976
AIC60199Y The oxidation of potassium tetracyanoplatinate(I1) in the absence of halide ions results in the formation of bronze needles of K1 75Pt(CN)p1.5H20 stoichiometry. The structure of this partially oxidized material consists of parallel one-dimensional noncollinear chains involving a commensurate repeat unit of 11.865 A. Thus the unit cell contents as deduced from single crystal xlray data is formulated K7[Pt(CN)4]@6HzOand is stoichiometric. This material crystallizes in the triclinic space group P1 with (I = 10.323 (14), b = 9.285 (13), c = 11.865 (17) A, a = 77.31 (3), @ = 114.85 ( 9 , y = 73.84 ( 2 ) O , and 2 = 4. The structure was solved by a combination of Patterson, Fourier, and least-squares refinement techniques to an RF = 0.050 for the 1840 observed reflections for which Fo > 3uF,. There are three inequivalent Pt atoms in the chain and two Pt-Pt bond distances of 2.967 (1) and 2.976 (1) A. The average twist angles of the cyanide ligands of the tetracyanoplatinate planes are 45.3 (5) and 49.8 (3.7'). An extensive network of K+ ionic bonding and hydrogen bonded water molecules knit the material together orthogonal to the chain direction. The chain distortion is shown to be due to Coulombic forces acting between the tetracyanoplatinate anions, located in the asymmetric crystal sites at z = -1/4 and 3/4, and the coordinated asymmetric K+ distribution. The crystallographic analysis leads to the formal oxidation state of +2.25 for Pt in this potassium deficient material and an odd number of electrons per unit cell.
Introduction In recent years there has been an enhanced interest in the chemical and physical properties of pseudo-one-dimensional inorganic and organic complexes due to the prediction and observation of a number of unusual anisotropic physical p h e n ~ m e n a ~(e.g., - ~ high conductivity, metallic state, metal insulator transition, charge density wave, superconductivity) and chemical properties (e.g., novel structures containing infinite chains with short interplanar spacings, homogeneous nonstoichiometric compositions, and mixed valency) directly associated with the reduced dimensionality of various onedimensional systems.6-8 For these reasons there has been immense interest in the synthesis and characterization of several partially oxidized one-dimensional materials. The best characterized highly conducting one-dimensional complexes are based on the partial oxidation of tetracyanoplatinate(I1) and reduction of 7,7,8,8-tetra~yano-p-quinodimethane.~ Partial oxidation of tetracyanoplatinate(I1) in the presence of chloride or bromide results in the formation of KzPt(CN)&o.y3H20 (X = C1, Br) which are well characterized at several temperatures by x-
ra~,~-'O neutron,11-14and diffuse scattering15 methods and have an incommensurate superlattice which is attributed to a charge density wave instability.16 Oxidation of tetracyanoplatinate(I1) in the absence of halide ions was shown by Levy in 19101' to yield a complex of nominal K175Pt(CN)4'1 .5H20173 stoichiometry. This bronze material was initially characterized by short interplanar spacings from x-ray powder analysis18 and c o n d ~ c t i v i t y ~ ~ which increased with decreasing ternperaturelga thereby suggesting a metallic state. With the isolation of single crystals suitable for x-ray20 and neutron21 analysis the structural determination of this partially oxidized cation deficient complex of K175Pt(CN)ql SH20, KDEF, has been completed. We are presenting here the results of the complete structural investigation which has been undertaken to characterize the nature of this cation deficient partially oxidized material and determine the driving force behind the Pt chain distortion.
Experimental Section Crystal Preparation. KDEF was prepared by the partial oxidation of K2Pt(CN)c3H20 in acid solution with hydrogen peroxide according
2456 Inorganic Chemistry, Vol. 15, No. 10, 1976
Peterson et al. Table I. Experimental Details on K1.7~Pt(CN),*1.5H20(KDEF)
Figure 1. Oscillation photograph of KDEF rotated about the c axis showing weak I # 4n layers and very strong 1 = 4n layers with no indication of a superlattice. to the methods of Levy,17Krogmann et a].,'* and Minot et a1.22 X-ray size crystals grew within 24 h out of the original reaction mixture. Two types of crystals appeared, both metaklic needks, a copper form and a bronze form. The copper form was shown to be KCP(Cl), formed due to C1- impurities within the original K2Pt(CN)4,3H20 starting material. Double aqueous recrystallization of K2Pt(CN)pxH20 is adequate to remove chloride impurities. The bronze appearing needles proved to be the desired form of KDEF. Many of the bronze needle crystals were twinned, the twin axis being the needle axis. A suitable untwinned specimen was selected and mounted in a sealed capillary for preliminary checking and data collection. Space Group. Pre-lirninary x-ray precession and Weissenberg photographs showed 1 Laue symmetry and no systematic absences consistent with the triclinic space groups P1 (Cl, No. 1) or P1 (Clj, No. 2). The crystal needle axis was chosen to be the mounting axis and the crystallographic c axis. Oscillation and rotation photographs showed reciprocal lattice layers for which 1 = 4n were especially strong; all others were very weak (see Figure 1). This result is in contrast to x-ray data for materials such as KCP(Br) and KCP(C1) where the c axis length is about half that of the present case and every I = 2n layer is strong. The strength of the I = 4n and the weakness of I # 4n layers clearly indicate the existence of a Pt chain with Pt atoms stacked -c/4 apart. X-Ray Data. Table I lists all pertinent experimental information concerned with the data collection and reduction of KDEF. The crystal, sealed in a glass capillary, was mounted on a G.E. XRD-490 automated diffractometer which has been previously discussed in detai1.23 The cell parameters were determined from precise angular measurements of 16 manually centered reflections, chosen in the 28 range of 20-35O. Two standard reflections were checked repeatedly during the data collection and found to remain unchanged in intensity within the expected statistical variation. Standard errors were assigned to the data on the basis of counting statistics plus a (0.031)2 contribution to the variance of each reflection. Structure Solution and Refinement. The structure was solved using a Patterson map which gave large peaks a t ~ / 4multiples indicating the positions of the Pt atoms. Space group P1 was chosen provisionally and Pt(1) and Pt(3) were assigned to the special positions at (O,O,O) and (0,0,'/2),while Pt(2) was placed at (0.002,0.002,0.252) initially. Isotropic full-matrix least-squares refinement of the scale factor and Pt atoms gave an initial RF of 0.24. A difference Fourier revealed the positions of the C, N, and K+ atoms, which were refined isotropically to an RF of 0.16. The potassium ions and Pt atoms were then refined by anisotropic full-matrix refinement to an RF of 0.12. A subsequent difference Fourier revealed the positions of all oxygen atoms and a further four cycles of anisotropic full-matrix least-squares refinement converged at an RFof 0.094. The positions of all hydrogen atoms were found on a final difference Fourier. Anisotropic full-matrix least-squares refinement of all atoms (hydrogens were refined positionally only with a fixed isotropic B = 4.0 A2) converged to a final RF of 0.088 for 3067 reflections.
Cell constants at T = 22 "C: a = 10.323 (14) A , b = 9.285 (13) A, C = 11.865 ( 1 7 ) A , a = 7 7 . 3 1 (3)",p= 114.85 ( 5 ) " , 7 = 7 3 . 8 4 (2)" Cell volume: 914.25 A 3 Molecular weight of KDEF: 394.59 g/equiv Calculated density: 2.866 g cm-3 Measured density: 2.820 ( 5 ) by flotation in CHBr$CCl, z=4 Space group: Pi [C,l, No. 21 Radiation: Mo Ka, h 0.710 69 A (Ross 1, Zr Filter) Attenuator: Cu foil at 10 000 Hz Take off angle: 2" Max 20: 50' (+h i k + I ) Scan type: 8-28 coupled Scan width: 1.4" Scan speed: 0.1" step Counting time: 5 s/step (background 20 s each side of peak) Crystal: c axis mounted cm3 (0.0060 X 0.0024 X 0.0200 cm) Volume = 0.31 12 X Absorption coefficient = 169.80 cm-' Max transmission factor = 0.63 Min transmission factor = 0.40 No. of reflections collected = 3227 R P for all reflections = 0.088 (3067) . , R F for reflections where F,bsd > 3&&sd = 0.050 (1840 ref) z2= 1.70 The quantity minimized in the refinement is Cw(Fo2- Fc2)2where Fo and Fc are the observed and calculated structure factor amplitudes and the weights w are given by 1/u2(F,J2. The agreement indices are defined as RF = 1IiFol- lFcII/lFo, 2;2 = C [ w ( F o 2- Fc2)2/(Ng - NR)]'I2, where NOis the number of independent observations and N R the number of parameters varied. The above RF values include all the reflections, many of which are unobserved or very weak. The final agreement indices of RF = 0.050 for Fo > 3u(Fo) and ZZ = 1.70 are perhaps more representative in indicating the excellence of the refinement. Since the exact H20 and K+ ion composition of the cell was in d o ~ b t , ~the~ multipliers , ~ ~ , ~ of ~ the oxygen atoms and potassium ions were varied in one of the final refinements. The multipliers converged to the following values: K(1), 0.980 (18); K(2), 0.967 (17); K(3), 1.003 (16); K(4), 0.521 (16) (at special position (l/2,0,0)); O(l), 1.13 (6); 0 ( 2 ) , 0.98 (6); and 0 ( 3 ) , 1.00 (6). These results indicate that the K+ ion and H20 sites are fully occupied. The stoichiometry of 3.5 K+ ions and 3 H2O molecules in the asymmetric unit was somewhat surprising; although the earliest report17 had given exactly that stoichiometry, later chemical studies of KDEF18,22gave K1.74Pt(CN)4*1.8H2Oand K1,78[Pt(CN)4]Br0.03p2H20 as representing the composition. The equivalence of the materials was verified through comparison of their respective reduced unit cell constants.20s21In view of the possibility that halide ion may be incorporated in the lattice a search of the final difference Fourier was made for weak peaks which could be identified with chlorine. Although several weak peaks were found at the noise level of the map (0.3 e-/A2) which could be possible halide sites, none were refinable. The thermal ellipsoid parameters p22 (0.0393) for K(4) and 611 (0.0263) for O(3) were observed to be relatively large indicating the possibility of disorder and careful examination of the final difference Fourier gave additional credence to this possibility. N o other atoms gave any similar indications. Two-position disorder models for both K(4) and O(3) were then incorporated into a least-squares refinement. Both models refined to yield two sites for both K(4) and 0(3), however, with no change in the R factor. The site separation of the two K+ sites was 0.72 (2) A and of the two 0 sites was 0.76 (6) A. The anisotropic thermal parameters of N(3) (see Figures 2 and 5a), which is bonded to both K ( l ) and 0 ( 3 ) , show a very small 011 (0.0005) contribution and are probably greatly affected by the K(4) and O(3) disorder. Parameter changes for other atoms were insignificant. Because of the disorder and the space group ambiguity a limited number of attempts were made to refine in the noncentrosymmetric space group P1. The large increase in number of parameters prohibited carrying out a complete noncent_osymmetric refinement in P1; however, all indications point to P1 as the correct space group. The existence of disorder in K(4) and O(3) positions, however, if accepted and assumed to be static does imply of course that the local structure
Nature of Pt Chain Distortion in K1.75Pt(CN)pl SH20
Inorganic Chemistry, Vol. 15, No. 10, 1976 2457
Table 11. Fractional Atomic Coordinates for KDEF with Estimated Standard Deviations given in Parentheses Atoms X Y z Pt(1)
0 0.009 26 (10) 0 0.050 (2) 0.087 (2) 0.235 (2) 0.363 (2) -0.237 (2) -0.367 (2) -0.021 (2) -0.027 (2) -0.119 (2) -0.193 (2) 0.134 (2) 0.205 (2) 0.198 (2) 0.302 (2) -0.185 (2) -0.299 (2) 0.400 3 (6) -0.269 9 (7) -0.1 12 5 (5)
'Iz
-0.451 -0.446 0.365 0.455 -0.482 0.498 -0.408 0.470 0.348
(2) (2) (2) (28) (27) (31) (29) (30) (27)
0 0.256 65 (9)
0
-0.021 37 (8) 0
'I2
0.054 (2) 0.085 (2) 0.097 (2) 0.148 (2) 0.402 (2) 0.349 (2) 0.446 (2) 0.412 (2) 0.231 (2) 0.219 (2) 0.275 (2) 0.282 (2) 0.364 (2) 0.428 (2) 0.156 (2) 0.092 (2) 0.329 4 (5) 0.392 4 (6) 0.129 8 (5) 0 0.199 (2) 0.448 (2) 0.089 (2) 0.099 (25) 0.158 (24) 0.406 (27) 0.462 (24) 0.171 (26) 0.136 (24)
-0.239 (2) -0.374 (2) -0.062 (2) -0.100 (2) 0.074 (2) 0.116 (2) 0.229 (2) 0.357 (2) -0.152 (2) -0.222 (2) 0.110 (2) 0.188 (2) -0.236 (2) -0.361 (2) 0.186 (2) 0.303 (2) 0.395 5 (5) -0.386 4 (6) 0.501 l ( 5 ) 0 -0.481 (2) -0.170 (2) 0.249 (2) -0.377 (26) 0.440 (26) -0.200 (28) -0.104 (27) 0.229 (24) 0.164 (28)
c141 N131'
N141
Figure 2. A single wavelength of the Pt atom chain repeat showing atom labeling and staggering of the TCP units along the Pt chain.
is actually noncentrosymmetric and that Pi applies to the average structure. The atom multipliers were also varied in one of the final refinements of the disordered model. The K+ ion and H20 stoichiometry were unchanged. The atomic coordinates for the average structure of KDEF are listed in Table I1 and the anisotropic temperature factors are listed in Table 111. The Pt, C, N, K+, and 0 scattering factors were taken from the compilation of Cromer and Waber24 and modified for the real and imaginary components of anomalous d i s p e r ~ i o n . Hydrogen ~~ scattering factors were taken from ref 26.
The raw x-ray data were reduced using the program DATA LIB^^ for input into the Fourier and least-squares refinement programs S S F O U R ~and ~ S S X F L S , ~respectively. ~ All distances, angles, and esd's were calculated using the program S5FFE.28 Molecular drawings were made using the program ORTEP.29 Structure Description. The interatomic distances for the structure of KDEF are given in Table IV while the interatomic angles are listed in Table V. Figure 2 depicts positions and labeling for all atoms along the Pt chain. The crystal structure of KDEF represents a complex mixture of a metal-metal, ionic, and hydrogen-bonded material. An important feature of the structure is the transversely distorted nonlinear Pt atom polymeric chain involving four TCP groups, which lies parallel to the crystallographic c axis and shows a repeat of 11.865 (17) A. Pt( 1) and Pt(3) lie at the positions (O,O,O) and (O,O,l/2) while Pt(2) lies at the general position h(0.009,-0.021,0.256), thus giving rise to a zig-zag chain with the chain sequence ...Pt(2)-Pt( l)-Pt(2)-Pt(3)Pt(2)-Pt(l) .... There are three inequivalent Pt atoms and two unique Pt-Pt distances, Pt(1)-Pt(2) = 2.967 (1) 8, and Pt(2)-Pt(3) = 2.976 (1) 8,. It is well known that least-squares error estimates for structural parameters are usually underestimated by factors of 2 to 3, thus the
Table 111. Anisotropic Thermal Parametersa (X lo4) of KDEF with Estimated Standard Deviations in Parentheses Atoms Pt(1) Pt(2) Pt(3) C(1) N(1) C(2) N(2) C(3) N(3) C(4) N(4) C(1)' N(1)' c(2): N(2) C(3)' N(31,' C(4) N(4)'
P1'
Pza
44.5 (18) 39.0 (13) 35.0 (17) 86 (29) 133 (32) 86 (37) 44 (28) 98 (39) 5 (23) 5 1 (25) 143 (33) 83 (31) 129 (33) 34 (23) 101 (30) 90 (33) 85 (28) 84 (32) 57 (25) 93 (8) 194(12) 108 (8) 97 (14) 162 (34) 105 (30) 263 (54)
44.8 (13) 49.4 (10) 43.6 (13) 83 (27) 63 (21) 48 (24) 177 (33) 63 (25) 184 (32) 5 1 (23) 76 (22) 55 (22) 97 (24) 58 (22) 150 (29) 41 (24) 85 (25) 73 (26) 92 (24) 141 (8) 150 (9) 103 (7) 393 (27) 195 (34) 175 (32) 167 (35)
P33
48.4 (16) 45.3 (11) 44.9 (15) 115 (19) 102 (26) 117 (35) 107 (30) 119 (34) 98 (28) 120 (20) 74 (23) 119 (19) 96 (27) 5 0 (23) 73 (25) 98 (30) 101 (27) 87 (29) 128 (30) 100 (8) K(l) K(2) 144 (10) K(3) 96 (7) K(4) 166 (17) O(1) 123 (30) O(2) 104 (27) O(3) 141 (36) a The form of the anisotropic temperature factor is: exp[-(h2p,, + k2p,,
PI2
P13
-16.1 (12) 20.8 (14) -11.7 (9) 17.5 (10) -7.8 (11) 13.9 (13) -50 (22) 44 (20) -48 (21) 69 (25) -29 (23) 10 (30) -35 (24) 20 (24) -33 (24) 70 (31) -17 (22) -5 (21) -10 (18) 14 (19) -39 (21) 60 (24) -1 (20) 37 (21) 71 (25) -72 (23) -1 (19) 17 (20) -90 (24) 30 (23) -24 (23) 42 (27) -16 (22) 35 (23) -35 (24) 39 (26) 42 (24) -11 (21) 52 (6) -16 (6) -88 (8) 124 (9) -50 (5) 54 (6) 36 (14) 75 (13) -27 (24) 40 (26) -92 (23) 28 (23) - 106 (34) -91 (33) + Pp,, + 2hkp,, + 2 h l p 1 3 + 2klp3,)].
Pa3
-8.7 (10) -9.5 (8) -9.6 (10) -5 (17) -18 (18) 7 (22) -10 (24) -20 (22) -1 (23) 2 (16) -22 (17) 12 (15) -42 (20) 6 (17) -47 (21) -27 (20) -21 (20) -35 (21) -14 (21) -40 (6) -66 (7) -33 (5) 115 (15) -46 (22) -66 (22) 44 (26)
Peterson et al.
2458 Inorganic Chemistry, Vol. 15, NO. 10, I976 Table IV. Interatomic Distances for KDEF with Estimated Standard Deviations Given in Parentheses Bond Bond Bond distance, distance, distance, Atoms A Atoms a Atoms a (A) Distances within the Pt-Pt Chain Pt( 1)-Pt(2) 2.967 (1) Pt(2)-Pt(3) 2.976 (1) (B) Distances within the TCP(1) Unit which Are Unique (Pt(1) Lies at a Center of Symmetry) 2.01 (2) Pt(l)C(2) 2.03 (2) Pt( 1)-C(1) 1.10 (3) C(I)-N(1) 1.13 (2) C(2)-N(2)
(C) Distances within the TCP(2) Unit Pt(2)-C(1)’ 2.01 (2) Pt(2)
