research communications
κ2N,N′)platinum(II)
of dichlorido(1,2-phenylenediamine-aDepartment of Chemistry, Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo, 153-8902, Japan, and bDepartment of Chemistry & Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo, 171-8501, Japan
*Correspondence e-mail: cnmatsu@rikkyo.ac.jp
The PtII atom in the title compound, [PtCl2{(C6H4)(NH2)2}], lies on a twofold rotation axis and has a slightly distorted square-planar coordination environment defined by two N atoms of an 1,2-phenylenediamine ligand and two Cl− ions. In the crystal, the planar complex molecules are stacked parallel to the c axis, resulting in a columnar structure. In a column, an infinite almost straight Pt⋯Pt chain is formed, suggesting weak metal–metal interactions [Pt⋯Pt = 3.3475 (8) Å]. The crystal packing is stabilized by a three-dimensional N—H⋯Cl hydrogen-bonding network between the amino groups and the Cl ligands of adjacent molecules.
Keywords: crystal structure; columnar structure; infinite metal chain; platinum(II) complex; hydrogen bonding.
CCDC reference: 1055177
1. Chemical context
The title compound, dichlorido(1,2-phenylenediamine-κ2N,N′)platinum(II) [PtCl2{(C6H4)(NH2)2}], (I), which was originally prepared by Connors et al. (1972), is a member of the family of derivatives of cis-diamminedichloridoplatinum(II), cis-[PtCl2(NH3)2] (cis-platin). Since the discovery of the antitumor activity of cis-platin (Rosenberg et al., 1965), numerous derivatives and analogues of cis-platin have been prepared and investigated. However, reports on the corresponding crystal structures are rather scarce, probably because of the difficulty in obtaining crystals suitable for X-ray analysis, in part owing to poor solubility. Although the antitumor activity (Connors et al., 1972; Meischen et al., 1976) and the chemical stabilities (Köckerbauer & Bednarski, 1996) of the title compound have been reported, its has not been determined so far. In the course of our study of the deprotonation and redox properties of a platinum complex with 1,2-phenylenediamine as a ligand (Konno & Matsushita, 2006a,b), we have successfully obtained single crystals of the title compound and report here its crystal structure.
2. Structural commentary
The molecular structure of (I) is displayed in Fig. 1. The platinum compound (I) is isostructural with the palladium compound [PdCl2{(C6H4)(NH2)2}] reported previously (Konno & Matsushita, 2017). The PtII atom lies on a twofold rotation axis. Hence the comprises half of a [PtCl2{(C6H4)(NH2)2}] molecule, the other half being completed by application of twofold rotation symmetry. The PtII atom is coordinated by two N atoms of an 1,2-phenylenediamine ligand and by two Cl− ions in a slightly distorted square-planar configuration (Table 1). The r.m.s. deviation of the least-squares plane formed by atoms Pt1, N1, C1, C2 and C3 is 0.0121 Å. The structural parameters of the coordination sphere around PtII in the crystal of (I) (Table 1) are consistent with those found in cis-[PtCl2(NH3)2] (Milburn & Truter, 1966), [PtCl2(en)] (en is ethylenediamine; Iball et al., 1975), cis-[PtCl2(L)2] (L is cyclohexylamine; Lock et al., 1980), [PtCl2(cis-dac)]·0.33-hydrate (dac is 1,2-diaminocyclohexane; Lock & Pilon, 1981), cis-[PtCl2(L′)(NH3)] (L′ is cyclobutylamine; Rochon & Melanson, 1986), [PtCl2(Me2en)] (Me2en is N,N-dimethylethylenediamine; Melanson et al., 1987), [PtCl2(tn)] (tn is 1,3-diaminopropane; Odoko & Okabe, 2006), [PtCl2(L′′)] (L′′ is 2-morpholinoethylamine; Shi et al., 2006), [PtCl2(Me4en)] (Me4en is N,N,N′,N′- tetramethylethylenediamine; Asiri et al., 2012). Bond lengths and angles of the 1,2-phenylenediamine moiety (Table 1) are not significantly different from those found in the bis(1,2-phenylenediamine)platinum(II) complex, [Pt(C6H8N2)2]Cl2·2H2O [N—C = 1.450 (2) Å, C—C = 1.365 (6)–1.389 (4) Å; Konno & Matsushita, 2006a] or in isostructural dichlorido(1,2-phenylenediamine)palladium(II) [N—C = 1.458 (2) Å, C—C = 1.371 (3)–1.416 (8) Å; Konno & Matsushita, 2017].
3. Supramolecular features
As shown in Fig. 2, the neutral planar molecules of (I) stack parallel to the c axis, resulting in a columnar structure. The planar [PtCl2{(C6H4)(NH2)2}] units are arranged in parallel and the 1,2-phenylenediamine moieties alternate with each other as a result of the c-glide operation. In the column, an infinite, almost straight [Pt⋯Pt⋯Pt = 176.513 (11)°] platinum chain is formed with a short interatomic distance [Pt⋯Pt = 3.3475 (8) Å], suggesting weak metal–metal interactions. The infinite palladium chain of the isostructural Pd complex is straighter [Pd⋯Pd⋯Pd = 179.232 (7)°] than the platinum chain. The Pt⋯Pt distance in (I) is slightly shorter than those of cis-[PtCl2(NH3)2] [3.372 (2) and 3.409 (2) Å; Milburn & Truter, 1966] or [PtCl2(en)] [3.381 Å; Iball et al., 1975], and is considerably shorter than that of [PtCl2(tn)] [3.646 Å; Odoko & Okabe, 2006], all of which have similar columnar structures.
The intermolecular Pt⋯Pt distance of (I) suggests that the columnar structure is stabilized by weak metal–metal interactions. The columnar structure of (I) is further stabilized by intermolecular N—H⋯Cl hydrogen bonds between adjacent molecules in the column (Fig. 2 and Table 2). Intercolumnar hydrogen bonds also help to stabilize the crystal packing of the columns (Fig. 3, and Table 2).
4. Synthesis and crystallization
Compound (I) was prepared using a method modified from that described by Connors et al. (1972) as follows. To an aqueous HCl solution (1.0 M, 15 ml) of K2[PtCl4] (0.241 mmol, 100 mg) was slowly added an aqueous HCl solution (1.0 M, 15 ml) of 1,2-phenylenediamine (0.241 mmol, 26 mg), and then the solution was sealed in a screw-cap vial and was kept at room temperature for one week in the dark. Pale-brown needle-like crystals suitable for X-ray analysis were obtained (yield 52%). Elemental analysis found: C 19.26, H 2.23, N 7.30%; calculated for C6H8Cl2N2Pt: C 19.26, H 2.16, N 7.49%. Elemental analysis was carried out by the Laboratory of Organic Elemental Analysis, Department of Chemistry, Graduate School of Science, The University of Tokyo.
5. Refinement
Crystal data, data collection and structure . One reflection (010) was omitted in the final because it was obstructed by the beam-stop. H atoms were placed in geometrically calculated positions and refined as riding, with C(aromatic)—H = 0.93 and N—H = 0.90 Å, and with Uiso(H) = 1.2Ueq(C,N). The maximum and minimum electron density peaks are located 0.80 and 0.74 Å, respectively, from atom Pt1.
details are summarized in Table 3
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Supporting information
CCDC reference: 1055177
https://doi.org/10.1107/S2056989017008477/wm5396sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989017008477/wm5396Isup2.hkl
Data collection: RAPID-AUTO (Rigaku, 1998); cell
RAPID-AUTO (Rigaku, 1998); data reduction: RAPID-AUTO (Rigaku, 1998); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2017); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008) and publCIF (Westrip, 2010).[PtCl2(C6H8N2)] | F(000) = 340 |
Mr = 374.13 | Dx = 2.805 Mg m−3 |
Monoclinic, P2/c | Mo Kα radiation, λ = 0.71075 Å |
Hall symbol: -P 2yc | Cell parameters from 12924 reflections |
a = 7.087 (2) Å | θ = 2.0–32.6° |
b = 10.446 (3) Å | µ = 16.38 mm−1 |
c = 6.6920 (16) Å | T = 296 K |
β = 116.61 (2)° | Needle, pale brown |
V = 442.9 (2) Å3 | 0.26 × 0.13 × 0.07 mm |
Z = 2 |
Rigaku R-AXIS RAPID imaging-plate diffractometer | 1587 independent reflections |
Radiation source: X-ray sealed tube | 1480 reflections with F2 > 2σ(F2) |
Graphite monochromator | Rint = 0.030 |
Detector resolution: 10.00 pixels mm-1 | θmax = 32.6°, θmin = 3.2° |
ω scans | h = −10→10 |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | k = −15→15 |
Tmin = 0.116, Tmax = 0.304 | l = −10→8 |
10875 measured reflections |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.034 | H-atom parameters constrained |
wR(F2) = 0.099 | w = 1/[σ2(Fo2) + (0.0669P)2 + 0.3105P] where P = (Fo2 + 2Fc2)/3 |
S = 1.18 | (Δ/σ)max = 0.001 |
1587 reflections | Δρmax = 4.62 e Å−3 |
52 parameters | Δρmin = −1.74 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0039 (12) |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. Least-squares planes (x,y,z in crystal coordinates) and deviations from them (* indicates atom used to define plane) - 2.7022 (0.0123) x - 0.0000 (0.0000) y + 6.6740 (0.0026) z = 0.3174 (0.0059) * 0.0000 (0.0000) Pt1 * -0.0185 (0.0028) Cl1 * 0.0206 (0.0042) N1 * 0.0050 (0.0039) C1 * -0.0017 (0.0044) C2 * 0.0031 (0.0116) C3 * 0.0185 (0.0028) Cl1_$6 * -0.0206 (0.0042) N1_$6 * -0.0050 (0.0039) C1_$6 * 0.0017 (0.0044) C2_$6 * -0.0031 (0.0116) C3_$6 Rms deviation of fitted atoms = 0.0121 |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
Pt1 | 0.5000 | 0.504875 (16) | 0.2500 | 0.03029 (13) | |
Cl1 | 0.23327 (19) | 0.65687 (13) | 0.1392 (2) | 0.0429 (3) | |
N1 | 0.2863 (7) | 0.3592 (4) | 0.1666 (8) | 0.0407 (9) | |
H1A | 0.2144 | 0.3653 | 0.2480 | 0.049* | |
H1B | 0.1934 | 0.3657 | 0.0213 | 0.049* | |
C1 | 0.3910 (7) | 0.2364 (4) | 0.2066 (6) | 0.0400 (8) | |
C2 | 0.2835 (10) | 0.1225 (5) | 0.1621 (9) | 0.0563 (12) | |
H2 | 0.1370 | 0.1224 | 0.1016 | 0.068* | |
C3 | 0.391 (3) | 0.0081 (5) | 0.207 (2) | 0.068 (3) | |
H3 | 0.3182 | −0.0690 | 0.1780 | 0.082* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Pt1 | 0.02635 (17) | 0.02835 (16) | 0.03208 (18) | 0.000 | 0.00944 (11) | 0.000 |
Cl1 | 0.0335 (5) | 0.0383 (5) | 0.0513 (6) | 0.0058 (4) | 0.0140 (4) | 0.0012 (4) |
N1 | 0.0347 (18) | 0.0371 (18) | 0.043 (2) | −0.0017 (14) | 0.0108 (16) | −0.0011 (15) |
C1 | 0.050 (2) | 0.0328 (18) | 0.0365 (18) | −0.0028 (15) | 0.0185 (17) | −0.0012 (14) |
C2 | 0.067 (3) | 0.046 (3) | 0.054 (3) | −0.018 (2) | 0.026 (2) | −0.005 (2) |
C3 | 0.112 (10) | 0.037 (3) | 0.063 (6) | −0.017 (3) | 0.047 (6) | −0.006 (2) |
Pt1—N1 | 2.040 (4) | N1—H1B | 0.9000 |
Pt1—N1i | 2.040 (4) | C1—C2 | 1.372 (6) |
Pt1—Cl1i | 2.3213 (13) | C1—C1i | 1.386 (9) |
Pt1—Cl1 | 2.3213 (13) | C2—C3 | 1.377 (11) |
Pt1—Pt1ii | 3.3475 (8) | C2—H2 | 0.9300 |
Pt1—Pt1iii | 3.3475 (8) | C3—C3i | 1.38 (3) |
N1—C1 | 1.445 (6) | C3—H3 | 0.9300 |
N1—H1A | 0.9000 | ||
N1—Pt1—N1i | 83.6 (3) | C1—N1—Pt1 | 110.8 (3) |
N1—Pt1—Cl1i | 174.82 (12) | C1—N1—H1A | 109.5 |
N1i—Pt1—Cl1i | 91.39 (15) | Pt1—N1—H1A | 109.5 |
N1—Pt1—Cl1 | 91.39 (15) | C1—N1—H1B | 109.5 |
N1i—Pt1—Cl1 | 174.82 (12) | Pt1—N1—H1B | 109.5 |
Cl1i—Pt1—Cl1 | 93.69 (7) | H1A—N1—H1B | 108.1 |
N1—Pt1—Pt1ii | 92.07 (14) | C2—C1—C1i | 119.8 (3) |
N1i—Pt1—Pt1ii | 85.32 (14) | C2—C1—N1 | 122.7 (5) |
Cl1i—Pt1—Pt1ii | 88.59 (4) | C1i—C1—N1 | 117.4 (2) |
Cl1—Pt1—Pt1ii | 93.80 (4) | C1—C2—C3 | 120.3 (8) |
N1—Pt1—Pt1iii | 85.32 (14) | C1—C2—H2 | 119.8 |
N1i—Pt1—Pt1iii | 92.07 (14) | C3—C2—H2 | 119.8 |
Cl1i—Pt1—Pt1iii | 93.80 (4) | C2—C3—C3i | 119.8 (6) |
Cl1—Pt1—Pt1iii | 88.59 (4) | C2—C3—H3 | 120.1 |
Pt1ii—Pt1—Pt1iii | 176.513 (11) | C3i—C3—H3 | 120.1 |
Pt1ii—Pt1—N1—C1 | 84.8 (3) | Pt1iii—Pt1—N1—C1 | −92.9 (3) |
Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+1, −y+1, −z; (iii) −x+1, −y+1, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···Cl1iv | 0.90 | 2.57 | 3.353 (4) | 146 |
N1—H1B···Cl1v | 0.90 | 2.71 | 3.381 (4) | 133 |
N1—H1B···Cl1vi | 0.90 | 2.73 | 3.320 (5) | 124 |
Symmetry codes: (iv) x, −y+1, z+1/2; (v) x, −y+1, z−1/2; (vi) −x, −y+1, −z. |
Funding information
Funding for this research was provided by: Ministry of Education, Culture, Sports, Science and Technology, MEXT-Supported Program for the Strategic Research Foundation at Private Universities (award No. S1311027).
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