The complexation behavior of the α-ketostabilized phosphorus ylides Ph ₃ P=CHC(O) C ₆ H ₄ -X (X=Br, Ph) towards the transition metal ions mercury (II) and Silver (I) was investigated. The mercury(II) complex {HgX ₂ [Y]} 2 (Y ₁ =4-bromo benzoyl methylene triphenyl phosphorane; X=Cl(1), Br(2), I(3), Y ₂ =4-phenyl benzoyl methylene triphenyl phosphorane; X=Cl(4), Br(5), I(6)) have been prepared from the reaction of Y ₁ and Y ₂ with HgX ₂ (X=Cl, Br, I) respectively. Silver complexes [Ag(Y ₂ ) ₂ ] X(X=BF ₄ (7), OTf(8)) of the α-keto-stabilized phosphorus ylides (Y ₂ ) were obtained by reacting this ylide with AgX (X=BF ₄ , OTf) in Me ₂ CO. The crystal structure of complexes (1) and (4) was discussed. These reactions led to binuclear complexes C-coordination of ylide and trans-like structure of complexes [Y ₁ HgCl ₂ ] ₂ . CHCl ₃ (1) and [Y ₂ HgCl ₂ ] ₂ (4) is demonstrated by single crystal X-ray analyses. Not only all of complexes have been studied by IR, ¹ H and ³¹ P NMR spectroscopy, but also complexes 1-3 have been characterized by ¹³ CNMR. α-ketostabilized phosphorus ylides are versatile ligands for heavy metal ions 1 - 5 and interesting ligands in organometallic chemistry and useful intermediates for organic synthesis. 6 - 19 They are versatile ligands for catalysts in a very small number of catalytic reactions such as, for example, the hydrogenation of olefins 20 and the cyclotrimerization 21 and polymerization of acetylenes, 22 but the most important application is in the industrially used SHOP process. 23 The α-keto-stabilized phosphorus ylides are distinguishable from no stabilized ylides, since they can be easily handled due to an additional stabilization from delocalization of the negative charge. The α-keto-stabilized phosphorus ylides was shown interesting properties such as their high stability and their ambidentate character as ligands (C- versus O-coordination). 24 - 30 This ambidentate character can be rationalized in terms of the resonance forms A–C ( 1 ). We have been interested in investigating the different bonding modes have been adopted by ylides when coordinated to Hg (II), Ag (I) and Pd (II). 24 - 27 The C and Ocoordinated complexes of Hg (II) was formed. 28 - 30 In this paper, we report the reactivity of the ligands 4-Bromo benzoyl methylene triphenyl phosphorane (Y ₁ ) and 4-Phenyl benzoyl methylene triphenyl phosphorane (Y ₂ ), towards mercury (II) halides and silver (I) salts. One of the significance aspects of our work is to ascertain the preferred coordination modes of Y ₁ and Y ₂ to the Hg and Ag metals. In this study, we describe the preparation, spectroscopic characterization (IR and NMR) of mercury (II) and silver (I) complexes with the title ylides. By a comparison of the data collected and single crystal x-ray diffraction of 1 and 4, it demonstrates C-coordination of the ylides to the metals. IR and NMR spectroscopy are suitable indicators for judging the bonding mode of the α-keto ylides. The IR spectra of 1-8 ( 1 ) show that ν (CO) absorption at between 1600-1645 cm ^-1 in the region typical for the Cbonded phosphorus ylides. 16 The increasing carbonyl stretching frequency in the IR spectra of these complexes, confirm that the ligand is bound through the carbon of ylide to Hg (II) and Ag (I) center ( 1 , 2 ). Similarly, in the ¹ H and ³¹ P NMR spectra of complexes 1-6 the downfield shift of the signal due to the PCH group are ascribed to C-coordination of the ylide ( 1 ). In the ¹ H NMR spectra of 7 and 8, the singlet at 5.35 and 5.40 ppm, respectively due to the methine proton appear in the downfield. These downfield shifts of the signal due to Ccoordination of the ylide ( 1 , 3 ). The resonances of the ³¹ PNMR complexes 1-8 have been observed to occur at a lower field with respect to the free ylide ( 1 , 2 and 3 ). The expected downfield shifts of ³¹ P and ¹ H signals for the PCH group upon complexation were observed in their corresponding spectra. The appearance of single signals for the PCH group in both the ³¹ P and ¹ HNMR at ambient temperature indicates the presence of only one molecule for all the complexes as expected for C-coordination. 31 That the bonding of the ylide to Hg (II) in the chloride complex is much weaker than in the bromide and the iodide complexes is indicative in the ¹ H NMR spectra in which the methin group resonances appear at δ 4.2, 4.52, 5.22, 5.06, 4.96, 5.5, 5.1, 5.06 and for the free ylides (Y ₁ and Y ₂ ) and complexes 1-6 , respectively ( 1 ). Although two diasteroisomer (RR/SS and RS) are possible for each complex (because the methine carbons are chiral) NMR spectroscopy dose not distinguish them at room temperature. The methine resonances of complexes ( 1-8 ) are intermediate between those in the free ylides and phosphonium salts; this was observed for other C-coordinated carbonyl-stabilized phosphorus ylide complexes and ² J _PH values smaller than the free ylides and phosphonium salts: because the hybridization changes in the ylidic carbon (SP ² -SP ³ ) in the C-coordination mode. 32 Values of ² J _PH much larger (ca. 20 Hz) have been observed in complexes where coordination is through the oxygen atom. 26 The ¹³ C NMR spectra of the complexes 1-3 is the up field shift of the signals due to the ylidic carbon atoms. Such an up field shift was observed in other complexes is due to the change in hybridization of the ylidic carbon atom on coordination. 32 Similar up field shifts of 2-3 ppm with reference to the parent ylide were also observed in the case of complexes of Hg (II) with BPPY complex. 33 The ¹³ C shifts of the CO group in the complexes are between 186-189 ppm, which is higher field than the 183.1 ppm noted for the same carbon in the parent ylide, indicating much lower shielding of the carbon atom of the CO group in the complexes. No coupling to Hg was observed at room temperature in the ¹ H, ¹³ C and ³¹ P NMR spectra. Failure to observe satellites in the above spectra was previously noted in the ylide complexes of Hg (II) 33 and Ag (I), 34 which had been explained by fast exchange of the ylide with the metal. In other hand it is possible that a fast equilibrium between complexes and free ylides is responsible for the failure observed either the NMR couplings or presence of two diastereoisomers. 2 provides the crystallographic results and refinement information for complexes 1 and 4 ( 2 ). The molecular structures are shown in . 1 and 2 . Selected bond distances and angles for 1 and 4 are given in 3 and 4 , respectively. The Hg (II) centre in complex 1 forms four close contacts with sp ³ hybridization and has a 4-coordinate environment with one short Hg–Cl (2.393 A ^o ) bond, one Hg–C bond and two asymmetric bridging Hg–Cl (bonds at distances of 2.7345 and 2.7090A ( . 1 ). The crystal structure of 1 shows the strongly distorted tetrahedral geometry at the Hg(II) Cl1-Hg1-C19, 147.14. 24 The significant shortening of the Hg–C bond length, 2.1979 A compared to analogous distances in [C ₆ H ₅ ) ₃ PCHCOC ₆ H ₅ HgI ₂ ] ₂ 31 and in [(C ₅ H ₄ P (C ₆ H ₅ ) ₃ HgI ₂ ] ₂ 33 (2.312(13) and 2.292(8) A ^o , respectively) must be attributed to the use of mercury orbital with high s character for bonding to the ylidic carbon. The use of non-equivalent hybrid orbital with high s character to bond to low electronegative atoms was proposed by Bent in the concept of isovalent hybridization to account for the variation in bond lengths and bond angles around a central atom. 35 The terminal Hg–Cl bond length, 2.3953A ^o is comparable to 2.352 (3)A ^o 30 observed in the case of [(EPPY)(HgCl ₂ )] ₂ , which has a tetrahedral coordination environment around. The Hg(II) centre in complex 4 is coordinated by one carbon and three chloro atoms in a distorted tetrahedral geometry. The two different Hg–Cl distances in 4 (2.3898(10) and 2.5630(8)A ^o ) are less than those of found in mononuclear complex of [HgCl ₂ (PPh ₃ ) ₂ ] 36 (2.559(2) and 2.545(3) A), indicating relatively strong Hg–Cl bonds in 4. Difference between two distances in these complexes might be arising from steric effects of the large ylidic groups. The angles around mercury in complex 4 vary from 87.39(13) to 139.45(11), indicating a much distorted tetrahedral environment. This distortion must be due to the higher s character of the sp3 hybrid mercury orbital involved in the above bonds and the steric effects of phosphine group needing the C–Hg–Cl angle to be larger mercury with a bridging structure. 37 The two bridged Hg–Cl bonds fall within the range 2.620–3.080A ^o reported for other structures 38 containing chloro bridged mercury. The angles around mercury in complex 1 and 4 vary from 85.13 to 147.14 and 87.20(2) to 133.55(8) for the chloride very distorted tetrahedral environment. This distortion must be due to the higher s character of the sp ³ hybrid mercury orbital involved in the above bonds and the formation of a strong chloro bridge between the Hg atoms which requires the internal ClHgCl angle to be considerably smaller. The stabilized resonance structure for the title ylide have been destroyed by the complexes formation. Thus, the C(19)– C(20) bond lengths (1.4964, 1.489(4)A ^o ) is significantly longer than the corresponding bond found in a similar free ylide (1.407(8)A ^o ) ( 5 ). 39 On the other hand, the bond length of P(1)–C(19) in the similar elide is 1.706A ^o 24 , 27 , 40 which show that the above bond is considerably elongated to 1.7890 and 1.786(3) A in these complexes ( 5 ). The elongation of the P–C (methine) bond in 1 and 4 relative to the free ylide supports the localization of the positive charge at the phosphorus ( 5 ). The adaptation of dimeric structures in Hg(II) ylide 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). The lengthening of the C–O bond is in the range of a C–O double bond and comparable with that in free ylide ( 5 ). The C-coordination of the title ylides ( 2 and 3 ) is in contrast to the O-coordination of the phosphorus ylide Ph ₃ PC (COMe) (COPh) (ABPPY) in a different Hg (II) complex. 41 The difference in the coordination mode between ABPPY and the Y ₁ and Y ₂ to Hg (II) can be rationalized in terms of the electronic properties, steric requirements, and size and shape of the ligand in the final bonding mode. Belluco et al . have studied steric influences on the coordination modes of ylide molecules to Pt (II) systems. 42 These authors concluded that the preferred coordination mode is via the ylidic carbon, but that steric hindrance around the metal centre or the ylidic carbon will necessitate O-coordination. Indeed, this trend is reflected here, Y ₁ and Y ₂ are slightly less sterically demanding than ABPPY and are C-coordinated to Hg (II). All the reactions were performed in air. The starting materials were purchased from commercial sources and used without further purification. All solvents were reagent grade and used without further purifications. Solution-state ¹ H and ³¹ P NMR spectra at 300 K were obtained in CDCl ₃ using a 500 MHz Bruker spectrometer operating at 500.13 MHz for 1H and 161.97 MHz for ³¹ P and referenced to H ₃ PO ₄ (85%) for ³¹ P{ ¹ H}NMR spectra. IR spectra were recorded on a FT-IR JASCO 680 spectrophotometer, and the measurements were made by the KBr disk method. Melting points were measured on a Gallenhamp 9B 3707 F apparatus. Elemental analysis for C, H and N were performed using a PE 2400 series analyzer. The data collection was performed at room temperature using the X-scan technique and using the STOE X-AREA software package. 43 The crystal structures were solved by direct methods and refined by full-matrix leastsquares on F ² by SHELXL97 44 and using the ORTEP-3 crystallographic software package. 45 The independent reflections was measured on an automatic STOE IPDS 2 diffractometer (graphite monochromated Mo–Kα radiation). All non-hydrogen atoms were refined anisotropically using reflections I > 2r (I). Hydrogen atoms were inserted at calculated positions using a riding model with fixed thermal parameters. Synthesis of PhC₆H₄COCH=PPh₃: To dichloromethane solution (15 ml) of 2-Bromo 4-Phenyl acetophenone (1.38 g, 5 mmol) was added of PPh ₃ (1.31g, 5 mmol) and the resulting mixture was stirred for 5h, the suspension was filtered off, the precipitate washed with diethyl ether (25 ml) and air-dried. Further treatment with aqueous NaOH solution (0.5 M) led to elimination of HBr (PH = 7), giving the free ligand. M.p. 230-231 C; Yield (1.87 g, 81.9%); IR (KBr, cm ^-1 ): ν 1507; ¹ H NMR (500 MHz, CDCl ₃ , ppm): δ = 4.52 (d, 1H, CHP, ² J _PH = 24 Hz), 7.38 (t 1H, H _p , C ₆ H ₅ ) 7.48 (t, 2H, H _m , C ₆ H ₅ ), 7.47 (t 2H, H _m , C ₆ H ₄ ) 7.53 (m, 6H, H _m , PPh ₃ ), 7.6 (m, 2H, H _o , C ₆ H ₅ , ³ J _HH = 6 Hz), 7.65 (t, 3H, H _p , PPh ₃ , ³ J _HH = 6 Hz), 7.84 (m, 6H, H _o , PPh ₃ ), 8.08 (d, 2H, H _o , C ₆ H ₄ ), ³¹ P{- ¹ H}NMR (CDCl ₃ ): δ = 17.2 (s, 1P, CHP). 2.4.2. Data for BrC₆H₄COC=HPPh₃ [25]: M.p: 142 ℃, Anal. Calc for C ₂₆ H ₂₀ OPBr: C, 68.03; H, 4.39 Anal Found: C, 68.22; H, 4.28. 13C NMR (CDCl ₃ ) δ C: 51.3 (d, ¹ J _PC = 111.2 Hz, CH); 126.2 (d, ¹ J _PC = 93.24 Hz, PPh ₃ (i)); 127.81 (COPh (m)); 128.88 (PPh ₃ (p)); 129.34 (d, ³ JPC = 12.41 Hz, PPh ₃ (m)); 131.80 (d, ⁴ J _PC = 2.81 Hz, COPh (o)); 133.40 (d, ₂ J _PC = 10.25 Hz, PPh ₃ (o)); 135.86 (COPh (p)); 140.63 (d, ² JPC = 14.69 Hz, COPh (i)); 183.1 (d, ² J _PC = 3.3 Hz, CO). Synthesis of the complexes of complexes HgX₂Y₂ {Ye = Y₁; X = Cl (1), Br(2), I(3), Ye = Y₂; X = Cl(4), Br(5), I(6)}. General procedure for complexes The following general procedure was used for preparing the complexes 1-6. To a solution (5 ml) of HgX ₂ (0.5 mmol) in ethanol (5 ml), a solution of Y ₁ (0.223 g, 0.5 mmol) in ethanol (10 ml) was add drop wise at room temperature and stirred for 4h. The resulting solid was treated with dichloromethane (25 ml) and filtered through celit. Addition of excess diethylether (15 ml) to the concentrated filtrate caused the precipitation of products as white or pale yellow solids. These solid products have been separated by filtration and washed with ethanol. The complexes were purified by repeating the precipitation two times and the solid dried under vacuum. Data for [Y₁. HgCl₂]₂ (1): Yield: 92.0%, M.p: 214 ℃, IR (cm ^-1 ), v(C=O):1635 Anal. Calc for C ₅₂ H ₄₀ Br ₂ Cl ₄ Hg ₂ P ₂ O ₂ : C, 42.75; H, 2.76 Anal Found: C, 42.45; H, 2.83. ¹ H NMR (500 MHz, CDCl ₃ , and ppm); 5.51(d, 1H, CH, ² J _PH = 10.25 Hz), 7.1-8.2 (m, 19H, Ph) ppm and ³¹ P NMR (CDCl ₃ ): 21.79 ppm. ¹³ C NMR (CDCl ₃ ) δ: 47.2 (d, ¹ J _PC = 73.2 Hz, CH); 123.33 (d, ¹ J _PC = 86.7 Hz, PPh ₃ (i)); 127.81 (COPh (m)); 129.8 (d, ³ J _PC = 12.35 Hz, PPh ₃ (m)); 130.5 (COPh (p)); 129.74 (PPh ₃ (p)); 132.8 (d, ² J _PC = 9.46 Hz, PPh ₃ (o)); 136.8 (COPh (o)); 137.3(COPh (i)); 189.82 (s, CO). Data for [Y₁. HgBr₂]₂ (2): Yield: 81%, M.p: 214 ℃, IR (cm ^-1 ), v(C=O):1621 Anal. Calc for C ₅₂ H ₄₀ Br ₆ Hg ₂ P ₂ O ₂ : C, 38.10; H, 2.46 Anal Found: C, 38.08; H, 2.33. ¹ H NMR (500 MHz, CDCl ₃ , and ppm); 4.62 (d, 1H, CH, ² J _PH = 5.5 Hz), 7.1-8 (m, 19H, Ph) ppm and ³¹ P NMR (CDCl ₃ ): 20.34 ppm. ¹³ C NMR (CDCl ₃ ) δ: 48.45 (d, ¹ J _PC = 81.3 Hz, CH); 126.13 (d, ¹ J _PC = 89.97 Hz, PPh3 (i)); 129.12 (COPh (m)); 121.13(d, ³ J _PC = 11.52 Hz, PPh3 (m)); 130.54 (PPh ₃ (p)); 133.25 (d, ² J _PC = 9.61 Hz, PPh ₃ (o)); 134.43 (COPh (p)); 137.3(COPh (o)); 137.92 (COPh (i)); 188.31 (s, CO). Data for [Y₁. HgI₂]₂: Yield: 76%, M.p: 204 ℃ (dec), IR (cm ^-1 ), v(C=O): 1618 Anal. Calc for C ₅₂ H ₄₀ Br ₄ Hg ₂ I ₂ P ₂ O ₂ : C, 34.19; H, 2.21 Anal Found: C, 34.05; H, 2.13. ¹ H NMR (500 MHz, CDCl ₃ , ppm): 5.48 (s br, 1H, CH), 7. -8.1 (m, 19H, Ph) ppm and ³¹ P NMR (CDCl ₃ ): 21.86 ppm. ¹³ CNMR (CDCl ₃ ) δ: 49.52 (d, ¹ J _PC = 83.77 Hz, CH); 123.62 (d, ¹ J _PC = 90.23 Hz, PPh ₃ (i)); 126.15 (COPh (m)); 128.89 (d, ³ J _PC = 12.15 Hz, PPh ₃ (m)); 131.62 (PPh ₃ (p)); 133.25 (d, ² JPC = 10.12 Hz, PPh ₃ (o)); 134.21 (COPh (p)); 136.94 (COPh (o)); 138.65 (d, ³ J _PC = 10.64 Hz, COPh (i)); 186.83 (s, CO). Data for [Y₂. HgCl₂]₂ (4): M.p. 218-220 ℃. Yield: 0.1098 gr (75.4%), IR (cm ^-1 ), ν (C=O): 1644.98, Anal. Calc for C ₆₄ H ₅₀ Cl ₄ Hg ₂ P ₂ O ₂ : C, 52.78; H, 3.46; Found. C; 51.7 H; 3.19 ¹ H NMR (500 MHz, CDCl ₃ , ppm); δ = 5.5 (s, 1H, CHP ), δ = 7.36 (t, 1H, Hp C ₆ H ₅ , ³ j _HH = 7.3HZ), δ = 7.425 (t, 2H, Hm C6H5, ³ j _HH = 7.74Hz), δ = 7.56 (m, 6H, Hm, PPh ₃ ), δ = 7.625 (m, 5H, Hp PPh ₃ + Ho C ₆ H ₅ ), δ = 7.678 (d, 2H, Hm C ₆ H ₄ , ³ j _HH = 13.86HZ), δ = 7.775 (d of d, 6H, Ho, PPh ₃ ), δ = 8.21 (d, 2H, Ho C ₆ H ₄ , ³ j _HH = 8.235 HZ). ³¹ P{ ¹ H} NMR (CDCl ₃ ): δ = 27.45 (s, 1P CHP). Data for [Y₂. HgBr₂]₂ (5): M.p. 236 ℃. Yield: .126gr (77.1%), IR (cm ^-1 ), ν (C=O):1627.63, Anal. Calc for C ₆₄ H ₅₀ Br ₄ Hg ₂ P ₂ O ₂ : C, 47.05; H, 3.08. Found. C; 46.88, H; 3.12. ¹ H NMR (500 MHz, CDCl ₃ , ppm): δ = 5.1 (s, 1H, CHP), 7.38 (m, 2H, Hm, C ₆ H ₅ ), δ = 7.33(t, 2H, Hm, C ₆ H ₄ CO) δ = 7.46 (sbr, 6H, Hm) δ = 7.51(2H, Ho C ₆ H ₅ ), δ = 7.56 (sbr, 5H, Hp PPh ₃ +Ho C ₆ H ₄ ) δ = 7.65 (m, 6H, Ho PPh ₃ ) δ = 8.025 (d, 2H, Ho, C ₆ H ₄ CO, ³ j _HH = 7.6Hz), ³¹ P{- ¹ H}NMR (CDCl ₃ ): δ = 25.6 (s, 1P, PPh ₃ ) Data for [Y₂. HgI₂]₂ (6): M.p. 130-132 ℃. Yield: 1.27 gr (69.5%), IR (cm ^-1 ), ν (C=O):1622.8, Anal. Calc for C ₆₄ H ₅₀ Hg ₂ I ₄ P ₂ O ₂ : C, 42.19; H, 2.77. Found. C;41.7 H; 2.83 , ¹ H NMR (500 MHz, CDCl ₃ , ppm); δ = 5.06 (s, 1H CHP), δ = 7.36 (t, 1H Hp C ₆ H ₅ , ³ j _HH = 6.9HZ), δ = 7.45 (t, 2H, Hm C ₆ H ₅ , ³ j _HH = 7.14Hz), δ = 7.58 (s br, 6H, Hm, PPh ₃ ), δ = 7.70 (m, 13H, 3Hp PPh ₃ + 6Ho C ₆ H ₅ + 2Ho C ₆ H ₅ + 2Hm C ₆ H ₄ ), δ = 8.01 (d, 2H, Ho C ₆ H ₄ , ³ j _HH = 7.46HZ). ³¹ P { ¹ H} NMR (CDCl ₃ ): δ = 20.54 (s, 1P, PPh ₃ ). The ylide PhBPPY (0.457 g, 1 mmol) was added to a solution of AgX (0.5 mmol) in acetone (10 mL). The solution was stirred for 1 h during which it was protected from light and then filtered. The volume of solvent was reduced under vacuum to 2 mL. Diethyl ether (25 mL) was added to precipitate white solid. Data for [Ag (Y₂) ₂] BF4 (7): M.p.150 ℃ (dec). Yield: 0.068 (61.4%), IR (cm ^-1 ), ν (C=O): 1600.63, Anal. Calc for C ₆₄ H ₅₀ AgBF ₄ P ₂ O ₂ : C, 69.39; H, 4.55, Found: H; 69.12, H; 4.51. ¹ H NMR (500 MHz, CDCl ₃ , ppm): δ = 5.35 (s, 1H, CHP), 7.42(s br, 8H, Hm C ₆ H ₅ +Hm PPh ₃ ), δ = 7.65 (m br, 13H, Hp PPh ₃ +Ho C ₆ H ₅ +Hm C ₆ H ₄ ), δ = 8.11 (d, 2H, Ho C ₆ H ₄ , ³ j _HH = 7.65Hz), ³¹ P{ ¹ H}NMR (CDCl ₃ ): δ = 24.8 (s, 1P, PPh ₃ ). Data for [Ag (Y₂) ₂] TfO (8): M.p. 210 ℃, Yield: 0.0744gr (63.6%), IR (cm ^-1 ), ν (C=O): 1600.68, Anal. Calc C ₆₅ H ₅₀ AgF ₃ P ₂ O ₅ S,: C, 66.75; H, 4.31. Found: H; 65.15, H; 4.21. 1H NMR (500 MHz, CDCl ₃ , ppm): δ = 5.4 (s, 1H, CHP), 7.26 (m br, 6H, Hm PPh ₃ ), δ = 7.35(d, 1H, Hp C ₆ H ₅ , ³ j _HH = 7.86HZ), δ = 7.58 (d, 2H Hm, C ₆ H ₄ , ³ j _HH = 7.6 Hz), δ = 8.14 (d, 2H, Ho C ₆ H ₄ , ³ j _HH = 7.89Hz). ³¹ P{ ¹ H}NMR (CDCl ₃ ): δ = 24.48 (s, 1P, PPh ₃ ). The present study describes the synthesis and characterization of a series of dimeric mercury (II) and bisylide silver (I) complexes derived from mercuric halides or silevr (I) with phosphorus ylides. On the basis of the physico-chemical and spectroscopic data, we propose that the ligands herein exhibit monodentate C-coordination to the metal centre, which is further confirmed by the X-ray crystal structure of the complexes.