Synthesis, characterization, and crystal structure of mercury(II) complex containing new phosphine oxide salt

Accepted Manuscript Synthesis, characterization, and crystal structure of mercury(II) complex containing new phosphine oxide salt Sepideh Samiee, Nadieh Kooti, Robert W. Gable PII:

S0022-2860(16)31027-4

DOI:

10.1016/j.molstruc.2016.09.079

Reference:

MOLSTR 22991

To appear in:

Journal of Molecular Structure

Received Date: 18 July 2016 Revised Date:

23 September 2016

Accepted Date: 28 September 2016

Please cite this article as: S. Samiee, N. Kooti, R.W. Gable, Synthesis, characterization, and crystal structure of mercury(II) complex containing new phosphine oxide salt, Journal of Molecular Structure (2016), doi: 10.1016/j.molstruc.2016.09.079. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

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Synthesis, characterization, and crystal

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structure of mercury(II) complex containing

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new phosphine oxide salt

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Sepideh Samieea*, Nadieh Kootia, Robert W. Gableb

Department of Chemistry, Faculty of Science, Shahid Chamran University of Ahvaz, Ahvaz, Iran School of Chemistry, University of Melbourne, Victoria 3010, Australia

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b

*Corresponding

author.

Tel:

+986113331042;

[email protected] and [email protected]

1

Fax:

+986113337009;

E-mail

address:

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Abstract The

reaction

of

new

phosphonium-phosphine

oxide

salt

[P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]Br (1) with mercury(II) iodide in a methanolic solution

fully characterized by elemental analysis, IR, 1H,

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P, and

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yielded [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2[Hg2I5Br](2). These two compounds were C NMR spectra. Crystal and

molecular structure of 2 has been determined by means of X-ray diffraction. In mercury

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compound, the phosphine oxide salt is found as a counter ion letting the mercury(II) ion to bound halides to all four coordination sites and to give dimermercurate(II) ions as the structure-

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constructing species. The neighboring [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2+cations are joined together by intramolecular C–H…O hydrogen bonds to give a 1-D chain structure along the crystallographic b-axis. The [Hg2I5Br]2-anions act as cross-linkers between neighbouring strands extending the supramolecular structure into 2D layers in (110) planes as well as

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balances the charge of the complex. The significant effects of C–H…X (X = O, Br and I) and π…π aromatic interactions play a major role in the crystal packing of compound 2.

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Keywords: Phosphine oxide salt, Mercury (II) complex, Crystal structure.

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1. Introduction For more than 60 years, phosphonium derivatives has been extensively investigated in organic synthesis, especially in constructing C=C double bonds. These types of compounds

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have been widely used as reactants in the Wittig olefination reaction of carbonyl compounds (aldehydes, ketones, lactones, etc.) [1–4]. Much investigation concerning ylide compounds have been conducted by experimental and theoretical chemists. In between studies, oxidation is an

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important preparation process in the phosphonium ylide chemistry, which can be performed with a lot of oxidizing agents [5–14]. Wasserman et al. applied the sequence of reactions

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(acylation, oxidation, aminolysis) to the α-cyanomethyl phosphonium ylide in order to synthesize various peptidic biological active compounds [5–7,10]. Moreover, the groups of Kawamura [12] and Lee [13,14] synthesized 1,2,3-tricarbonyl compounds by oxidation of disubstituted stabilized ylides. The preparation of all-(Z)-cyclododecatetraene by oxidation of

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the appropriate bis-ylide is also reported in recent years [15].

On the other hand, bisphosphine monoxides are also known as an important class of phosphorus ligands containing both soft (P) and hard (O) donor centers [16–19]. However, the

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synthesis of entitle ligands, and the study of their complexation to transition metals, is a less documented field; in spite of their practical importance. These compounds can be used as ligand

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incoordination chemistry and catalyst in chemistry reactions [20–27]. The reaction of 1,2bis(diphenylphosphino)ethane monoxide (dppeO) with various mercury(II) halides reported in 2007 by Ebrahim et al. [25]. However, in the present work we have found quite different patterns of reactivity of similar ligand toward mercury(II) halides. With the aim to expand this research theme, we have studied the reactivity of the new phosphonium-phosphine oxide salt [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]Br (1) toward mercury(II) iodide. Herein, the synthesis,

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spectral and structural characterization of this ligand (1) and its mercury(II) iodide complex (2) are reported.

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2. Experimental 2.1. Materials and physical measurements

The chemicals and solvents used in this work are of analytical grade and available

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commercially and were used without further purification. NMR spectra were acquired on a 300 MHz Bruker spectrometer in CDCl3 and DMSO-d6 with TMS as the internal standard. All

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chemical shift values were recorded in ppm (δ). Coupling constants are given in Hz. IR spectra were recorded on a FT BOMEM MB102 spectrophotometer and the measurements were made by the KBr disk method. Elemental analyses (C, H, N) were performed using a Perkin-Elmer

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2400 series analyzer. Melting points were measured on a SMP3 apparatus without correction.

2.2. Synthesis of [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]Br (1) To acetone solution of (diphenylphosphino) ethane (dppe) (0.398 g, 1 mmol) was added 4-

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nitrophenacyl bromide (0.256 g, 1.05 mmol)and the resulting mixture was stirred for 12 h at room temperature.The resulting yellow solution was filtered off, washed with petroleum diethyl

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ether, and dried under vacuum. Yield: 0.49 g, 75%; m.p.:220–222˚C. Anal. Calc. for C34H30BrNO4P2: C, 62.02; H, 4.59; N, 2.13. Found: C, 62.27; H, 4.61; N, 2.15%. Selected IR absorption in KBr (cm-1): 1684 (νC=O), 1191 (νP=O).

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P{1H} NMR (CDCl3): δP = 19.45 (d,

PCH2, 3JPP = 58.37); 31.66 (d, P(O)Ph2, 3JPP = 54.82). 1H NMR (CDCl3): δH = 2.83 (m, 2H, CH2); 3.82 (m, 2H, CH2); 6.32 (d, 1H, PCH2CO, 2JPH = 12.25), 6.52 (d, 1H, PCH2CO, 2JPH =

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12.00); 7.18–8.37 (m, 24H, Ph).

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C{1H} NMR (CDCl3): δC = 18.06 (t, CH2, 1JPC = 26.03);

36.32 (pseudot, PCH2CO, 1JPC = 29.13); 116.03–134.95 (Ph); 191.31 (s, CO).

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2.3. Synthesis of[P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2[Hg2I5Br]2-(2)

To a solution of HgI2 (0.122 g, 0.27 mmol) in methanol(8 mL), a solution of 1 (0.177 g, 0.27mmol) in the same solvent(8 mL) was added dropwise and the reaction allowed to

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proceedunder stirring for 2 h. The pale yellow solid product was separated by filtration and washed with Et2O. Yield: 0.19 g, 63%; m.p.:212–214˚C. Anal. Calc. for C68H30BrI5Hg2N2O8P4:

(cm-1): 1685 (νC=O), 1192 (νP=O).

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C, 35.94; H, 2.66 N, 1.23. Found: C, 36.17; H, 2.76; N, 1.29%.Selected IR absorption in KBr P{1H} NMR (DMSO-d6): δP = 24.22 (br, PCH2); 38.95 (d,

P(O)Ph2, 3JPP = 47.16). 1H NMR (DMSO-d6): δH = 2.40 (m, 2H, CH2); 3.51 (m, 2H, CH2); 6.25 (d, 1H, PCH2CO, 2JPH = 12.25), 6.48 (d, 1H, PCH2CO, 2JPH = 12.00); 7.31–9.20 (m, 24H, Ph). C{1H} NMR(DMSO-d6):δC = 19.20 (br, CH2); 29.04 (br, PCH2CO); 124.48–151.29 (Ph);

192.16 (s, CO).

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2.4. X-ray Crystallography

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Suitable single crystal of [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2)][Hg2I5Br]2-(2) was grown

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by vapour diffusion of ethanol onto dichloromethane/diethyl ether. Single-crystal X-ray diffraction of compound2was collected on an Agilent Technologies SuperNova diffractometer using mirror mono-chromated Cu Kα radiation (λ = 0.71073 Å) at 130 K. The structure was solved by direct methods with SHELXS-97 [29] and refined by a full-matrix least-squares procedure on F2 using SHELXL-97 [30] with anisotropic displacement parameters for nonhydrogen atoms, hydrogen atoms in their calculated positions and a weighting scheme of the

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form w = 1/[σ2(Fo2) + 0.1P2] where P = (Fo2 +2Fc2)/3.Crystal data and refinement details are given in Table 1. The molecular structures and their atom labeling schemes for 2 are illustrated

relevant hydrogen bond parameters are provided in Table 3.

3. Results and Discussion

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3.1. Synthesis and General Characterization

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in Fig. 2. Selected bond lengths and angles for this complex are listed in Table 2 as well as the

The preparation of the phosphonium-phosphine oxide salt (1) was carried out by reaction of

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the diphosphine (dppe) with 4-nitrophenacyl bromide. The 31P NMR and IR of the compound 1 give some evidence for the formation of the phosphonium-phosphine monoxide salt. Recently, we have reported the synthesis of corresponding phosphonium-phosphine salt using a similar reaction under dry nitrogen atmospheres [28]. The IR spectra of the compound 1 shows strong

the

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bands at 1191and 1684cm-1, attributed to the(P=O) and (C=O) group, respectively. Furthermore, P NMR spectrum of this compound presents two doublets at 19.45 and 31.66 ppm

attributable to the phosphonium group and to the phosphine oxide, respectively (Fig. 1a). The

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structure of 1 was deduced from their IR and NMR spectra. Aiming to expand our knowledge of the reactivity of phosphine ligands towards metallic substrates, we have reacted the

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phosphonium monoxide salt with mercury(II) iodide. This reaction is represented in Scheme 1. The obtained complex from this reaction is characterized by IR, NMR spectra, and X-ray crystallography. Interestingly, different structure of mercury(II) complex has been observed with this typical ligand.

Fig. 1.here

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Scheme 1.here The chemical nature of the complex (2) was checked by means of IR, 31P, 1H and 13CNMR spectroscopy. In the IR spectra, the strong absorption bands υ(C=O) at 1685 cm-1 and υ(P=O) at

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1192 cm-1, which is close to the same frequency in free salt (1684 cm-1) indicates the noninvolvement of the phosphonium and phosphine oxide groups in the reactions [25,28]. Similar variation of about 2–3 cm-1 with reference to the parent ylide have also been observed in

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the case of the mercury derivative {HgX2Br(PPh2(CH2)2PPh2CH2C(O)C6H4R)} (X = Cl, Br, I; R = Cl, NO2) [28]. It should be note that coordination of the ylide through C-coordination

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causes an increase in υ(CO) while for O-coordination a lowering of υ(CO) is expected [31]. Therefore, the Infrared data is suggested the ligand (1) is not coordinated to the Hg atom. The

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PNMR spectrum for complex (2) exhibit the presence of the Ph2P(O) and Ph2PCH2

groups as abroad δ 24.22 ppm and doublet δ 38.95 ppm, respectively (Fig. 1b). These chemical

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shift being similar to that observed for the free ligand (1) (δ 19.45 and 31.66 ppm), which means that the P=O group remain free and no significant interaction with the mercury has been observed. Noted that the chemical shifts and the coupling constants is completely different with

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the 31PNMR data of Hg(II)–phosphine complexes reported previously [25, 28]. In the 1H NMR spectra of complex 2, the doublet due to methyl PCH2 group at 6.48 ppm

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with a coupling constant 2JP–H of 12.00 Hz, appears in the same region as observed for the free ligand (δ 6.52 ppm). Analogously, in the

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C{1H} NMR spectra of this compound, the signals

related to the carbonyl group have remained unaffected due to complexation. It is worth noting that the most interesting features of the 13C spectra of the ylidic complex is the up-field shift of the signal due to the carbonyl group [32, 33]. The expected lower shielding of 13C and 1H nuclei for the PCH2CO group due to complexation were not found in the corresponding spectra, as

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noted previously in the case of some Hg(II)–phosphine complexes formed by the similar phosphonium salt [28]. Thus, the results of spectroscopic studies clearly show that no functional

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groups in molecular structure of ligand (1) have coordinated to the metal center.

3.2. Crystal Structure Analysis

The molecular structure of 2 is shown in Fig. 2. Relevant parameters concerning data

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collection and refinement are given in Table1. Selected molecular geometry parameters are listed in Table 2, while the details on non-classical hydrogen bonding geometry are listed in

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Table 3. Fractional atomic coordinates and equivalent isotropic displacement coefficients (Ueq) for the non-hydrogen atoms of the complexes are available as Supplementary material. Fig. 2.here

Table 1.here

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Table 2.here Table 3.here

Single crystal X-ray studies indicate that compound 2 crystallizes in the triclinic space

dimermercurat(II)

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group P-1. The crystal structure consists of phosphonium-phosphine oxide cations and anions

(Fig.

2).

In

this

structure,

the

neighboring

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[P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2+cations are linked together by the phosphino and nitro groups through C–H…O hydrogen bonds, with H…O bond lengths of 2.0200–2.5900 Å, to form a 1D polymeric chain structure along the crystallographic b-axis (Fig. 3a) [34,35]. Moreover, the intramolecular π…π aromatic interactions occur between two neighboring almost parallel 4-nitrophenacyl rings, with centroid-centroid distances of 3.888(2) Å and with dihedral angle of 0.202(19)° (Fig. 3b). Not that the latter interactions involving the phenyl rings from

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neighbouring molecules and above mentioned hydrogen bonds stabilize additionally the crystal structure. The [Hg2I5Br]2-anions act as cross-linkers between neighbouring strands extending

and C–H…Br types involving phenyl protons and halides (Fig. 4). Fig. 3.here Fig. 4.here

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the supramolecular structure into 2D layers in [110] planes through two interactions of C–H…I

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As shown in Fig. 2, the Hg atom was not attached to the ligand, instead the phosphorous atom had been oxidized to the phosphine oxide, with the mercury and halogens forming the

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[X2HgX2HgX2]2- anion. The Hg(II) center in this complex is four-coordinate with sp3 hybridization. This environment involves two asymmetric terminal Hg–X bonds and two asymmetric bridging Hg–X bonds at distances of 2.707(3), 2.672(5), 2.899(3) and 2.870(2) Å. Note that the terminal Hg–I bonds is shorter than the bridging bonds. The two mercury atoms

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and two bridging iodides in 2 are perfectly coplanar. It should be noted that one of the terminal halogen atoms attached to the mercury atom was a mixture of iodine and bromine (during the refinement); the other halogen positions were found to be fully occupied iodine. Refinement

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was carried out with the anisotropic displacement parameters being constrained to be equal; no restraints were applied to the Hg−Br and Hg−I distances. The final occupancy factors for I and

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Br were 0.499(4) and 0.501(4) giving rise to an anion having the formula [Hg2I5Br]2-. One of the oxygen atoms on the nitro group showed evidence of some disorder and the anisotropic displacement parameters were restrained to near isotropic values. The internuclear distance between mercury atoms in this complex was found to be 4.013Å, that are much longer than the sum of vander Waals radii (1.5 Å) of the two mercury atoms [36], indicating the absence of significant bonding interactions between the mercury atoms in the

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molecular structure. The adaptation of dimeric structures in Hg(II) complexes may be explained by both the preference of Hg(II) to four coordination and the stability of the 18 electron configuration around Hg(II).

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The angles around mercury vary from 91.860(10) to 118.581(10) for this complex, a much distorted tetrahedral environment. This distortion must be due to the higher s character of the sp3 hybrid mercury orbital involved in the formation of a strong halogen bridge between the Hg

terminal

Hg–I

bond

[(Ph3PCHC(O)C6H4NO2)HgI2]2

lengths

are

(2.6846(7)

comparable Å)

and

to

analogous

distances

in

[(p-tolyl)3PCHC(O)C6H4Cl)HgI2]2

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The

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atoms which requires the internal X−Hg−X angle to be considerably smaller.

(2.6999(6) Å), which has a tetrahedral coordination environment around mercury with a bridging structure [37]. The two bridged Hg–I bonds fall within the range 2.8704(4)–8996(3) Å reported for other similar structures containing iodide bridged mercury [25]. It is worth noting

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that the terminal Hg–Br bond length, 2.556(8) is in agreement with the values reported in [HgBr2(PPh3)2] (2.559(2) and 2.545(3) Å) [38].

It should be mentioned that the phosphorus and oxygen atoms are cis oriented due to strong

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1,4-P…O intramolecular interactions between the positively charged P atom and the negatively charged O atom, as reported previously for similar mercury(II) ylide complexes [39,40] (see

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Fig. 5). Also, the nitro group and keto group lie significantly out of the plane of the aromatic ring, the dihedral angles being 23.9(2)° and 20.06(12)°, respectively. In addition, the calculated dihedral angles between the phenyl rings related to P=O group (yellow and pink colored) and the phenyl rings related to PCH2 group (red and green colored) are 77.41° and 34.73°, respectively. It is interesting to note that the bond lengths (Ǻ) and angles (°) are in same range for mercury(II) complex containing similar phosphine–phosphonium salt [28].

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Fig. 5.here

4. Conclusion

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The reactions of the mercury(II) halide with new synthesized phosphonium-phosphine oxide salt revealed different product as a result of their various tendencies toward the halide ions. Formations of the latter complex have been confirmed by spectroscopic and crystallography

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techniques. The crystal structure consists of phosphonium-phosphine oxide cations, [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2+,and

dimermercurat(II)

anions,

[Hg2I5Br]2-.

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Interestingly, the phosphine oxide expressed its tendency toward the C–H…O hydrogen bonds in the formation of 1D polymeric chains, while the [Hg2I5Br]2-counter-anion counter balances the charge of the complex and act as cross-linkers between chains. The intramolecular C–H…I and C–H…Br interactions stabilized the structure and link the discrete 1-D chains into a 2-D

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network structure. Thus, the result of the interaction between mercury(II) and phosphine ligands can be considered as an active field of research leading to complexes with unusual structures.

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Acknowledgements

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We thank Shahid Chamran University of Ahvaz for financial support.

Appendix A. Supplementary material CCDC 1476103 contains the supplementary crystallographic data for compound 2. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associated with this article can be found, in the online version, at doi..…………..

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[40] A. Lledós, J.J. Carbó, R. Navarro, E.P. Urriolabeitia, Inorg. Chem. 357 (2004) 1444.

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CH2

P H2C H2C

Ph Ph

O C

NO2 Br

P

CH2

P +

HgI2

H2C

CH3OH

H2C

O

Ph Ph

O

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Ph Ph

C

NO2

Br

P

O

I

2

(2)

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Scheme 1. The synthesis route for preparation of compound (2).

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I Hg

Hg

Ph Ph (1)

2 I

I

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C68H60N2O8P4BrI5Hg2 2272.65 130.01(10) 1.54184 triclinic P-1 12.0718(6) 13.3173(7) 13.3532(5) 60.500(5) 73.576(4) 74.588(4) 1771.46(17)

Z

1 7.215

376 0.3345 × 0.119 × 0.0362 65.916 to 60.674 -15 ≤ h ≤ 16 -18 ≤ k ≤ 15 -18 ≤ l ≤ 18 18494 9213 [Rint = 0.0244, Rsigma = 0.0413] 9213/6/410 1.049 R1 = 0.0297, wR2= 0.0632 R1= 0.0400, wR2 = 0.0689 1.54, -1.76 1476103

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Reflections collected Independent reflections Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I>2σ(I)] R indices (all data) Largest difference peak and hole (Å-3) CCDC deposition no.

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Absorption coefficient(mm-1) F(000) Crystal size (mm) 2θ range for data collection (°) Index ranges

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Empirical formula Formula weight Temperature (K) Wavelength (Å) Crystal system Space group a (Å) b (Å) c (Å) α (º) β (º) γ (º) Volume (Å3)

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Table 1. Crystal data and experimental details for (2).

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Table 2. Selected bond lengths (Å) and bond angles (°) for (2).

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91.86(10) 104.94(10) 118.58(10) 106.06(12) 116.33(10) 116.81(10) 111.70(16) 105.70(19) 120.37(16) 88.140(10) 113.98(15) 111.89(16) 111.90(16) 110.69(16) 112.40(16) 110.07(17) 124.3(3) 117.8(3) 117.8(3)

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Bond angles I(1)–Hg(1)–I(1a) I(2)–Hg(1)–I(1a) I(2)–Hg(1)–I(1) I(3)–Hg(1)–I(1) I(3)–Hg(1)–I(1a) I(3)–Hg(1)–I(2) Br(3)–Hg(1)–I(1a) Br(3)–Hg(1)–I(2) I(1)–Hg(1)–I(1a) Hg(1)–I(1)–Hg(1a) O(4)–P(1)–C(1) O(4)–P(1)–C(7) O(4)–P(1)–C(13) C(15)–P(2)–C(14) C(15)–P(2)–C(27) C(15)–P(2)–C(21) O(2)–N(1)–O(3) O(2)–N(1)–C(32) O(3)–N(1)–C(32)

2.870(4) 2.899(3) 2.707(3) 2.672(5) 2.556(8) 2.899(3) 1.489(3) 1.814(4) 1.811(4) 1.805(3) 1.547(4) 1.210(5) 1.221(4) 1.488(4)

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Bond lengths Hg(1)–I(1) Hg(1)–I(1a) Hg(1)–I(2) Hg(1)–I(3) Hg(1)–Br(3) Hg(1a)–I(1) P(1)–O(4) P(1)–C(13) P(2)–C(14) P(2)–C(27) C(13)–C(14) N(1)–O(2) N(1)–O(3) N(1)–C(32)

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H… A 2.86 2.87 2.91 2.85 3.18 3.20 2.37 2.57 2.02

D–H 0.95 0.95 0.95 0.95 0.99 0.99 0.95 0.95 0.99

D… A 3.638(7) 3.635(10) 3.818(7) 3.744(9) 4.016(4) 4.069(6) 3.249(5) 3.093(4) 2.992(4)

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1-x,1-y,1-z 1-x,-y,1-z

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<(DHA) 139.7 138.2 159.8 156.2 143.7 147.0 153.4 115.1 166.6

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D–H…A C2–H2…I3 C2–H2…Br3 Cl2–H12…I3i Cl2–H12…Br3i C13–H13… I2 C13–H13… I3i C20–H20…O4ii C26–H26…O1 C27–H27…O4ii

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Table 3. Significant non-classical hydrogen bonds (interatomic distance (Å) and bond angles °) found in the structures of compound 2.

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Fig. 1. 31P-NMR spectrum of compound (a) 1 (b) 2.

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Fig. 2. ORTEP view of the X-ray crystal structure of 2, showing the atomic numbering scheme.

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Fig. 3. (a) 1-D chain of [P(O)Ph2(CH2)2PPh2CH2C(O)C6H4NO2]2+ cations formed by intermolecular C–H…O hydrogen bonds; (b) intramolecular π…π aromatic interactions. (All hydrogen bonds and intramolecular interaction are shown as dashed lines)

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Fig. 4. Supramolecular 2D layers of 2 formed by linking of neighbouring phosphine oxide and locked [Hg2I5Br]2anions between chains.

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Fig. 5. Schematic view of phosphonium- phoshine oxide in crystal structure of 2.

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