Abstract
C30H28O6P2Pt, monoclinic, C2/c (no. 15), a = 16.911(3) Å, b = 9.516(2) Å, c = 16.790(3) Å, β = 100.830(4)°, V = 2653.8(9) Å3, Z = 4, Rgt(F) = 0.0126, wRref(F2) = 0.0310, T = 293 K.
The complex title structure is shown in the figure. Table 1 contains crystallographic data and Table 2 contains the list of the atoms including atomic coordinates and displacement parameters.
Data collection and handling.
| Crystal: | Brown needle |
| Size: | 0.30 × 0.20 × 0.20 mm |
| Wavelength: | Mo Kα radiation (0.71073 Å) |
| μ: | 5.45 mm−1 |
| Diffractometer, scan mode: | Bruker APEX-II, ω |
| θmax, completeness: | 26.3°, >99% |
| N(hkl)measured, N(hkl)unique, Rint: | 18368, 2675, 0.021 |
| Criterion for Iobs, N(hkl)gt: | Iobs > 2 σ(Iobs), 2653 |
| N(param)refined: | 183 |
| Programs: | Bruker [1], SHELX [2] |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2).
| Atom | x | y | z | Uiso*/Ueq |
|---|---|---|---|---|
| C1 | 0.44711(12) | 0.5225(2) | 0.63025(11) | 0.0133(4) |
| C2 | 0.37156(12) | 0.4801(2) | 0.58769(12) | 0.0155(4) |
| H2 | 0.36282(12) | 0.3851(2) | 0.57082(12) | 0.0186(5)* |
| C3 | 0.30961(12) | 0.5772(2) | 0.57029(13) | 0.0184(4) |
| H3 | 0.25859(12) | 0.5490(2) | 0.54067(13) | 0.0220(5)* |
| C4 | 0.32192(13) | 0.7156(2) | 0.59605(13) | 0.0185(4) |
| H4 | 0.27880(13) | 0.7811(2) | 0.58555(13) | 0.0222(5)* |
| C5 | 0.39700(13) | 0.7584(2) | 0.63702(13) | 0.0173(4) |
| H5 | 0.40539(13) | 0.8534(2) | 0.65395(13) | 0.0208(5)* |
| C6 | 0.46002(12) | 0.6626(2) | 0.65337(12) | 0.0147(4) |
| H6 | 0.51178(12) | 0.6925(2) | 0.68026(12) | 0.0176(5)* |
| C7 | 0.62125(12) | 0.4721(2) | 0.68086(12) | 0.0146(4) |
| C8 | 0.64127(12) | 0.5775(2) | 0.62994(13) | 0.0177(4) |
| H8 | 0.60066(12) | 0.6188(2) | 0.59002(13) | 0.0212(5)* |
| C9 | 0.72043(13) | 0.6213(2) | 0.63794(14) | 0.0205(4) |
| H9 | 0.73415(13) | 0.6930(2) | 0.60361(14) | 0.0246(5)* |
| C11 | 0.76032(12) | 0.4574(2) | 0.74725(13) | 0.0200(4) |
| H11 | 0.80102(12) | 0.4170(2) | 0.78744(13) | 0.0240(5)* |
| C12 | 0.68106(12) | 0.4134(2) | 0.73956(12) | 0.0164(4) |
| H12 | 0.66757(12) | 0.3426(2) | 0.77462(12) | 0.0196(5)* |
| C13 | 0.52914(13) | 0.2961(2) | 0.56534(12) | 0.0167(4) |
| H13a | 0.47483(13) | 0.2624(2) | 0.54003(12) | 0.0201(5)* |
| H13b | 0.54777(13) | 0.3617(2) | 0.52699(12) | 0.0201(5)* |
| C15 | 0.55317(12) | 0.0447(2) | 0.61826(12) | 0.0146(4) |
| C16 | 0.77982(13) | 0.5604(2) | 0.69612(14) | 0.0209(4) |
| H16 | 0.83419(13) | 0.5898(2) | 0.70084(14) | 0.0251(5)* |
| C17 | 0.58688(12) | 0.1706(2) | 0.58063(13) | 0.0171(4) |
| H17a | 0.60102(12) | 0.1416(2) | 0.52844(13) | 0.0205(5)* |
| H17b | 0.63708(12) | 0.2010(2) | 0.61684(13) | 0.0205(5)* |
| O1 | 0.51177(9) | 0.06433(15) | 0.67441(9) | 0.0182(3) |
| O2 | 0.56517(9) | −0.07417(16) | 0.59461(9) | 0.0217(3) |
| O3 | 0.64613(11) | −0.1206(2) | 0.47227(12) | 0.0365(4) |
| H3a | 0.6097(17) | −0.088(4) | 0.4284(14) | 0.0548(6)* |
| H3b | 0.6201(18) | −0.098(4) | 0.5148(14) | 0.0548(6)* |
| P1 | 0.52316(3) | 0.38910(5) | 0.65876(3) | 0.01164(10) |
| Pt1 | 0.5 | 0.232461(10) | 0.75 | 0.01130(4) |
Source of material
Treatment of 4-formyl-3-hydroxybenzoic acid (0.401 g, 2.41 mmol) with one equivalent of 4-amino-3-hydroxybenzoic acid (0.396 g, 2.41 mmol) in ethanol yielded a mixture, which was refluxed for 10 h. This procedure resulted in the formation of (E)-4-(4-carboxy-2-hydroxybenzylidene)amino-3-hydroxybenzoic acid [3]. This educt (0.100 g, 0.332 mmol) was further treated with (0.115 g, 0.166 mmol) [PtCl2(C15H15O2P)2] salt precursor to isolate a tridentate O–N–O Pt(II) Schiff base complex for 24 h as an orange solid in good yield (75%). Upon growing crystals of this complex, ligand substitution of the imine resulted in a second mole of the propionic acid ligand coordinating to the metal. This resulted in simultaneous deprotonation of the propionic acid resulting in a bis coordination fashion.
Brown crystals suitable for single X-ray diffraction were obtained by slow evaporation from dimethylsulfoxide and methanol from a solution of the complex for 3 weeks at room temperature.
Experimental details
Crystal data was collected on a Bruker APEXII diffractometer with detector to crystal distance of 4.00 cm. The initial cell matrix was obtained from three series at different starting angles. Each series consisted of 12 frames collected at intervals of 0.5° in approximately a 6° range with an exposure time of 10 s per frame. Structure solution was achieved by direct methods (program SHELX) within the XSEED interface and all non-hydrogen atoms from F-map. All hydrogen atoms were included at idealized positions and were allowed to ride on the parent atoms with relative isotropic displacement coefficients.
Comment
Phosphine ligands have a general formula PR3 (where R = alkyl, halide, aryl, hydrogen etc.) [4]. These ligands play an important role in stabilizing many transition metal catalysts and can activate the metal centre while also assist in fine-tuning the selectivity of products in catalytic transformations. This is done by modifying the steric and electronic environment around the phosphine by simply varying the substituents on the phosphorus atom [5], [6]. These ligands are well known for their versatility to perform various applications [7], [8]. Phosphine ligands can be coordinated to various transition metals (Pt, Pd, Rh, Ru etc.) for various applications such as hydroformylation, hydrogenation, Mizoroki-Heck and Suzuki cross-coupling reactions [9], [10], [11], [12], [13]. Our interests in phosphine ligands includes application of platinum complexes in catalytic as well as biological studies. Trettenbrein and co-workers reported the synthesis of an electron rich, highly stable new phosphanyl-carboxylate ligand and its coordination to Pt(II). These organometallic compounds with functionalised phosphanes have revealed a great in homogenous catalysis [14]. However, the synthesis procedure of this Pt-based phosphanyl-carboxylate ligand involves several steps. Our work, reports the synthesis and characterisation of bis(3-diphenylphosphinopropanoate)platinum(II), following a single-step process under ambient conditions. Single crystal X-ray diffraction showed that the title structure is best described in the space group C2/c. The central Pt(II) has a square planar coordination geometry which is found in d8 complexes reported in the literature [15], [16]. The crystal structure shows coordination of Pt metal to two oxygen atoms and two phosphorus atoms in a bis fashion with a pendant carboxylate group forming the oxygen donor ligands. The connectivity in the title compound together with the bond lengths and bond angles are in expected ranges. The Pt—O and Pt—P bond lengths are 2.0744 Å and 2.2242 Å, respectively which is similar to what has been reported in literature [17], [18], [19], [20].
Acknowledgements
This work was supported by the South African National Research Foundation (Grant Numbers: 117989), UJ Centre for Synthesis and Catalysis and SASOL (under the Sasol University Collaboration Programme).
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©2020 Pamela Moyo et al., published by De Gruyter, Berlin/Boston
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