cis-(Malonato-κ²O,O′)bis­(2-methyl­pyridine-κN)platinum(II)

In the crystal structure of the title compound, [Pt(C₃H₂O₄)(C₆H₇N)₂], the Pt^II ion is tetra­coordinated in a square-planar coordination geometry. There are intermolecular C—H...O hydrogen bonds.

Key indicators

• Single-crystal X-ray study
• T = 298 K
• Mean [sigma](C-C) = 0.006 Å
• R factor = 0.021
• wR factor = 0.046
• Data-to-parameter ratio = 17.6

checkCIF/PLATON results

No syntax errors found



Alert level G
PLAT794_ALERT_5_G Check Predicted Bond Valency for Pt1         (2)       2.16

   0 ALERT level A = In general: serious problem
   0 ALERT level B = Potentially serious problem
   0 ALERT level C = Check and explain
   1 ALERT level G = General alerts; check

   0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data
   0 ALERT type 2 Indicator that the structure model may be wrong or deficient
   0 ALERT type 3 Indicator that the structure quality may be low
   0 ALERT type 4 Improvement, methodology, query or suggestion
   1 ALERT type 5 Informative message, check

---

S1. Comment

cis-diammine(1,1-cyclobutanedicarboxylato) platinum(II) (Carboplatin) is commonly used for the treatment of testicular and overian cancer as well as cervical, bladder and head and neck tumors. It has proven to be the only second-generation platinum complex commercially available worldwide at present (Jakuper et al., 2003). But the application of carboplatin in therapy is limited by the dose-dependent nephrotoxicity and other side effects. Therefore, the search for the new potent platinum complexes possessing high antitumor activity and lack of cross-resistance is needed. The title compound is a new soluble carboplatin analogue containing an asymmetric chelating malonate anion as its carrier and anticancer tests are presently being carried out.

The title complex consists of discrete monomeric complexes, in which the Pt(II) is coordinated by two crystallographically independent 2-methylpyridine ligands and one malonate anions within an square planar geometry. The coordination behaviour of the tetradentate ligand displays similar features to those described in the literature (Tu et al., 2004; Zhang et al., 2002; Ali et al., 2002). The six-membered chelate ring built up of the Pt(II) atom and the malonate anion adopts a boat conformation and the two 2-methylpyridine liagnds are oriented perpendicular to each other.

Related literature

For related literature, see: Ali et al. (2002); Jakuper et al. (2003); Tu et al. (2004); Zhang et al. (2002).

S2. Experimental

Potassium tetrachloroplatinate(II) (5 g, 12 mmol) was dissolved in water (50 ml) and KI (12 g, 72 mmol) was added. The mixture were stored in the dark for 30 min at room temperature and afterwards a solution of 2-methylpyridine (1.08 g, 12 mmol in 50 ml water) was added dropwise. The mixture was stirred for 4 h and the yellow precipitate of di(2-methylpyridine)PtI₂ was filtered off. Afterwards 2.5 g (0.044 mmol) of di(2-methylpyridine)PtI₂, 75 ml of water and disilver malonate (1.36 g, 3.65 mmol) were stirred at 50°C for 72 h. The precipitate of AgI was filtered off and the filtrate was concentrated at 40°C under reduced pressure to about 5 ml until a white crystalline solid of the title compound precipitate. The compound was recrystallized from water to obtain crystals suitable for X-ray crystallography.

S3. Refinement

All H atoms were initially located in a difference Fourier map but were positioned with idealized geometry and refined isotropic with U_iso(H) = 1.2U_eq(C) (1.5 for methyl H atoms) using a riding model with C—H = 0.93 (aromatic), 0.97 (methylen) and 0.96 Å) (methyl).

Computing details

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 2000); software used to prepare material for publication: SHELXTL (Sheldrick, 2000).

Figures

Fig. 1. Molecular view of the complex, with the atomic labeling scheme. Displacement ellipsoids are drawn at the 30% probability level.

cis-(Malonato-κ²O,O')bis(2-methylpyridine-κN)platinum(II)

Crystal data

[Pt(C3H2O4)(C6H7N)2]	F(000) = 920
Mr = 483.39	Dx = 2.150 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 3532 reflections
a = 8.5790 (6) Å	θ = 2.3–28.3°
b = 15.8079 (11) Å	µ = 9.42 mm^−1
c = 11.5595 (8) Å	T = 298 K
β = 107.748 (1)°	Block, colourless
V = 1493.04 (18) Å^3	0.24 × 0.19 × 0.16 mm
Z = 4

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	3532 independent reflections
Radiation source: fine-focus sealed tube	3007 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
φ and ω scans	θmax = 28.3°, θmin = 2.3°
Absorption correction: numerical (APEX2; Bruker, 2004)	h = −11→11
Tmin = 0.141, Tmax = 0.235	k = −20→20
12687 measured reflections	l = −15→15

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.021	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.046	H-atom parameters constrained
S = 0.95	w = 1/[σ^2(Fo^2) + (0.0222P)^2 + 0.6402P] where P = (Fo^2 + 2Fc^2)/3
3532 reflections	(Δ/σ)max = 0.002
201 parameters	Δρmax = 0.53 e Å^−3
0 restraints	Δρmin = −0.76 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

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 > σ(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Pt1	0.636843 (15)	0.055740 (8)	0.171724 (11)	0.02722 (5)
N1	0.8270 (3)	−0.00984 (17)	0.1478 (2)	0.0287 (6)
N2	0.6310 (3)	−0.01854 (18)	0.3124 (3)	0.0306 (6)
O1	0.6260 (3)	0.12457 (15)	0.0230 (2)	0.0361 (6)
O2	0.4457 (3)	0.11978 (15)	0.1953 (2)	0.0384 (6)
O3	0.3179 (4)	0.24193 (18)	0.1819 (3)	0.0663 (9)
O4	0.5635 (5)	0.24575 (19)	−0.0733 (3)	0.0718 (10)
C1	0.8018 (4)	−0.0905 (2)	0.1111 (3)	0.0374 (8)
H1	0.6975	−0.1132	0.0956	0.045*
C2	0.9251 (5)	−0.1411 (2)	0.0956 (4)	0.0436 (9)
H2	0.9039	−0.1969	0.0700	0.052*
C3	1.0802 (5)	−0.1078 (3)	0.1186 (3)	0.0443 (9)
H3	1.1662	−0.1411	0.1117	0.053*
C4	1.1050 (4)	−0.0241 (3)	0.1521 (3)	0.0410 (9)
H4	1.2080	−0.0001	0.1656	0.049*
C5	0.9767 (4)	0.0250 (2)	0.1660 (3)	0.0318 (7)
C6	1.0016 (5)	0.1165 (2)	0.2008 (4)	0.0428 (9)
H6A	0.9258	0.1504	0.1402	0.064*
H6B	1.1115	0.1328	0.2066	0.064*
H6C	0.9832	0.1250	0.2779	0.064*
C7	0.5863 (4)	0.2049 (2)	0.0186 (3)	0.0400 (9)
C8	0.5686 (5)	0.2435 (2)	0.1339 (3)	0.0401 (9)
H8A	0.5444	0.3033	0.1208	0.048*
H8B	0.6714	0.2380	0.1984	0.048*
C9	0.4338 (4)	0.2013 (2)	0.1732 (3)	0.0392 (9)
C10	0.5415 (4)	−0.0904 (2)	0.2854 (4)	0.0395 (8)
H10	0.4901	−0.1035	0.2042	0.047*
C11	0.5237 (5)	−0.1446 (2)	0.3729 (4)	0.0520 (11)
H11	0.4602	−0.1931	0.3512	0.062*
C12	0.6005 (6)	−0.1267 (3)	0.4929 (4)	0.0576 (12)
H12	0.5932	−0.1635	0.5538	0.069*
C13	0.6891 (6)	−0.0524 (3)	0.5207 (4)	0.0547 (11)
H13	0.7399	−0.0384	0.6017	0.066*
C14	0.7036 (5)	0.0014 (3)	0.4304 (3)	0.0415 (9)
C15	0.7993 (6)	0.0816 (3)	0.4616 (4)	0.0636 (13)
H15A	0.9039	0.0744	0.4487	0.095*
H15B	0.8148	0.0954	0.5452	0.095*
H15C	0.7407	0.1265	0.4108	0.095*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Pt1	0.02567 (7)	0.02699 (8)	0.02939 (8)	0.00007 (5)	0.00899 (5)	−0.00007 (5)
N1	0.0244 (14)	0.0320 (15)	0.0288 (14)	0.0016 (12)	0.0070 (11)	0.0013 (12)
N2	0.0252 (14)	0.0321 (15)	0.0342 (15)	0.0014 (12)	0.0084 (12)	0.0009 (13)
O1	0.0420 (14)	0.0362 (14)	0.0310 (13)	0.0048 (11)	0.0125 (11)	0.0050 (11)
O2	0.0345 (14)	0.0330 (14)	0.0530 (16)	0.0052 (11)	0.0212 (12)	0.0032 (12)
O3	0.0483 (18)	0.0439 (17)	0.115 (3)	0.0094 (14)	0.0381 (19)	−0.0085 (18)
O4	0.120 (3)	0.0455 (18)	0.0496 (19)	0.0080 (18)	0.0254 (19)	0.0192 (15)
C1	0.0315 (19)	0.039 (2)	0.042 (2)	0.0010 (16)	0.0105 (16)	−0.0006 (17)
C2	0.052 (2)	0.033 (2)	0.047 (2)	0.0064 (18)	0.0173 (19)	−0.0038 (17)
C3	0.043 (2)	0.053 (3)	0.040 (2)	0.0174 (19)	0.0182 (18)	0.0073 (19)
C4	0.0287 (19)	0.057 (2)	0.038 (2)	0.0051 (17)	0.0111 (16)	0.0029 (18)
C5	0.0314 (18)	0.0384 (19)	0.0242 (17)	0.0017 (15)	0.0062 (14)	0.0038 (15)
C6	0.035 (2)	0.047 (2)	0.047 (2)	−0.0091 (17)	0.0132 (17)	−0.0061 (18)
C7	0.037 (2)	0.039 (2)	0.041 (2)	−0.0022 (16)	0.0071 (17)	0.0033 (17)
C8	0.042 (2)	0.0283 (19)	0.049 (2)	0.0016 (16)	0.0124 (18)	−0.0034 (17)
C9	0.0321 (19)	0.040 (2)	0.045 (2)	0.0001 (16)	0.0101 (17)	−0.0067 (17)
C10	0.037 (2)	0.035 (2)	0.047 (2)	−0.0030 (16)	0.0134 (17)	−0.0001 (17)
C11	0.053 (3)	0.034 (2)	0.074 (3)	−0.0059 (19)	0.027 (2)	0.010 (2)
C12	0.064 (3)	0.058 (3)	0.057 (3)	0.003 (2)	0.027 (2)	0.024 (2)
C13	0.056 (3)	0.070 (3)	0.036 (2)	0.000 (2)	0.010 (2)	0.011 (2)
C14	0.036 (2)	0.050 (2)	0.037 (2)	−0.0046 (18)	0.0102 (16)	−0.0012 (18)
C15	0.071 (3)	0.068 (3)	0.048 (3)	−0.028 (3)	0.013 (2)	−0.015 (2)

Geometric parameters (Å, º)

Pt1—O1	2.013 (2)	C5—C6	1.499 (5)
Pt1—O2	2.015 (2)	C6—H6A	0.9600
Pt1—N2	2.019 (3)	C6—H6B	0.9600
Pt1—N1	2.022 (3)	C6—H6C	0.9600
N1—C1	1.340 (5)	C7—C8	1.515 (5)
N1—C5	1.354 (4)	C8—C9	1.519 (5)
N2—C14	1.353 (4)	C8—H8A	0.9700
N2—C10	1.353 (5)	C8—H8B	0.9700
O1—C7	1.312 (4)	C10—C11	1.369 (5)
O2—C9	1.311 (4)	C10—H10	0.9300
O3—C9	1.213 (4)	C11—C12	1.371 (6)
O4—C7	1.207 (4)	C11—H11	0.9300
C1—C2	1.381 (5)	C12—C13	1.383 (6)
C1—H1	0.9300	C12—H12	0.9300
C2—C3	1.380 (5)	C13—C14	1.382 (5)
C2—H2	0.9300	C13—H13	0.9300
C3—C4	1.376 (6)	C14—C15	1.493 (6)
C3—H3	0.9300	C15—H15A	0.9600
C4—C5	1.395 (5)	C15—H15B	0.9600
C4—H4	0.9300	C15—H15C	0.9600
O1—Pt1—O2	90.94 (10)	H6B—C6—H6C	109.5
O1—Pt1—N2	175.20 (10)	O4—C7—O1	121.4 (4)
O2—Pt1—N2	87.82 (10)	O4—C7—C8	121.8 (3)
O1—Pt1—N1	89.39 (10)	O1—C7—C8	116.7 (3)
O2—Pt1—N1	179.30 (10)	C7—C8—C9	112.1 (3)
N2—Pt1—N1	91.80 (11)	C7—C8—H8A	109.2
C1—N1—C5	119.3 (3)	C9—C8—H8A	109.2
C1—N1—Pt1	118.2 (2)	C7—C8—H8B	109.2
C5—N1—Pt1	122.5 (2)	C9—C8—H8B	109.2
C14—N2—C10	118.9 (3)	H8A—C8—H8B	107.9
C14—N2—Pt1	124.0 (2)	O3—C9—O2	121.4 (3)
C10—N2—Pt1	117.0 (2)	O3—C9—C8	120.7 (3)
C7—O1—Pt1	120.0 (2)	O2—C9—C8	117.9 (3)
C9—O2—Pt1	119.0 (2)	N2—C10—C11	122.5 (4)
N1—C1—C2	122.4 (3)	N2—C10—H10	118.7
N1—C1—H1	118.8	C11—C10—H10	118.7
C2—C1—H1	118.8	C10—C11—C12	119.4 (4)
C3—C2—C1	119.0 (4)	C10—C11—H11	120.3
C3—C2—H2	120.5	C12—C11—H11	120.3
C1—C2—H2	120.5	C11—C12—C13	118.1 (4)
C4—C3—C2	118.6 (3)	C11—C12—H12	120.9
C4—C3—H3	120.7	C13—C12—H12	120.9
C2—C3—H3	120.7	C14—C13—C12	121.1 (4)
C3—C4—C5	120.5 (3)	C14—C13—H13	119.4
C3—C4—H4	119.8	C12—C13—H13	119.4
C5—C4—H4	119.8	N2—C14—C13	119.9 (4)
N1—C5—C4	120.0 (3)	N2—C14—C15	119.5 (3)
N1—C5—C6	119.0 (3)	C13—C14—C15	120.7 (4)
C4—C5—C6	121.0 (3)	C14—C15—H15A	109.5
C5—C6—H6A	109.5	C14—C15—H15B	109.5
C5—C6—H6B	109.5	H15A—C15—H15B	109.5
H6A—C6—H6B	109.5	C14—C15—H15C	109.5
C5—C6—H6C	109.5	H15A—C15—H15C	109.5
H6A—C6—H6C	109.5	H15B—C15—H15C	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C10—H10···O1^i	0.93	2.53	3.455 (5)	173
C6—H6B···O3^ii	0.96	2.55	3.422 (5)	151
C6—H6A···O1	0.96	2.55	3.254 (5)	130

Symmetry codes: (i) −x+1, −y, −z; (ii) x+1, y, z.