Characterisation, electrochemical and oxidative addition data of organophosphorus-containing rhodium(I) complexes

This data article contains the 1H Nuclear Magnetic Resonance (NMR), ultraviolet and visible (UV–vis) and Attenuated Total Reflectance Fourier Transformed Infra-red (ATR FTIR) characterization of a series of organophosphorus-containing rhodium(I) complexes. The electrochemical data acquired by means of cyclic voltammetry of the three organophosphorus-containing ligands (with the structure C6H5XPPh2, where X = O, S and NH) and their acetylacetonato (monocarbonyl) organophosphorus rhodium(I) compounds, [Rh(acac)CO(C6H5XPPh2)] are reported. Additionally, the kinetic data of the oxidative addition of methyl iodide to the rhodium(I) complexes, are also presented.

How data were acquired NMR were recorded on a Bruker Avance DPX 300 NMR spectrometer, ATR FTIR were recorded on a Nicolet IS50 FTIR Tri-detector gold spectrometer, with a build-in diamond ATR module as well as in a KCl liquid cell connected to a water bath for temperature control, Cyclic voltammograms were recorded on a Princeton Applied Research PARSTAT 2273 voltammograph, running PowerSuite (Version 2.58), UV-vis were recorded on a Shimadzu UV/Vis spectrometer Data format Analyzed Experimental factors All electrochemical data are reported, using the potential of the ferrocene/ferricinium redox couple [FcH/FcH þ ] (E°`¼ 0.00 V) as an internal reference.
The kinetic measurements were recorded at four temperatures ranges between 15 and 45°C.

Experimental features
Electrochemical measurements were conducted on ca. 0.2 mmol dm -3 solutions of the analyte in acetonitrile, containing 0.10 mmol dm -3 tetra-n-butylammonium hexafluorophosphate as supporting electrolyte. The data can be used during catalyst design to compare how variation of X in the ligand structure C 6 H 5 XPPh 2 with O, S and NH, influences the oxidative addition of methyl iodide to the rhodium (I) complexes.
The data can be used for comparison with related compounds; here, we present the 1 H NMR, 31 P NMR, UV-vis and ATR FTIR spectroscopy which provides characterisation data for research community on organophosphorus ligands and their Rh(I) complexes.

Data
The characterisation by means of Nuclear Magnetic Resonance ( 1 H NMR see Figs. 1-6 and 31 P NMR see Figs. 7-12), ultraviolet and visible (see Fig. 13 and Table 1 for the UV-vis spectra, the Beer-Lambert law is shown in Fig. 14) and Attenuated Total Reflectance Fourier Transformed Infra-red (see Table 1, for the summary of the ATR FTIR data) of three organophosphorus ligands with the structure C 6 H 5 XPPh 2 , where, X ¼ O (1), S (2) and NH (3) and their acetylacetonato (monocarbonyl) organophosphorus rhodium(I) compounds, [Rh(acac)CO(C 6 H 5 XPPh 2 )] where X ¼ O (4), S (5) and NH (6) are presented.   The electrochemical behavior is presented as comparative graphs of the cyclic voltammograms of ligands 1-3 (see Fig. 15 and Fig. 16 with the data reported in Table 2), while the acetylacetonato (monocarbonyl) organophosphorus rhodium(I) compounds, 4-6, are given in Fig. 16 and the data are summarized in Table 3 (Fig. 17).  Time-based UV/vis spectra for the oxidative addition of CH 3 I onto the Rh(I) metal centre are shown in Fig. 18, while the temperature dependence and Eyring plots are given in Fig. 19 and Fig. 20, respectively, with the kinetic data obtained from the plots summarised in Table 4.
The oxidative addition reaction was also followed by FTIR; Fig. 21 represents the time-based FTIR, while Fig. 22 depicts the absorbance/time graph and concentration dependence graph, as monitored by FTIR. The data obtained the kinetic measurement from the FTIR are given in Table 5, while Table 6 gives a comparative summary of the kinetic data as measured by UV-vis and FTIR.

Electrochemistry
Electrochemical measurements were conducted on ca. 0.2 mmol dm À 3 solutions of the four rhodium(I) complexes in acetonitrile, containing 0.10 mmol dm À 3 tetra-n-butylammonium hexafluorophosphate (Fluka, electrochemical grade) as supporting electrolyte, under a blanket of purified argon, at 25°C, utilizing a Princeton Applied Research PARSTAT 2273 voltammograph, running PowerSuite (Version 2.58). A three-electrode cell, utilizing a Pt auxiliary electrode, a glassy carbon  working electrode, and an Ag reference electrode, was employed. Temperature was kept constant within 0.5°C. All electrode peak potentials were reported, using the potential of the ferrocene/ferricinium redox couple [FcH/FcH þ ] (E°`¼ 0.00 V) as an internal reference [2]. Successive experiments under the same experimental conditions showed that all formal reduction and oxidation peak potentials were reproducible within 5 mV.

Kinetic measurements
The methyl iodide oxidative addition onto the various rhodium complexes was studied by means of FTIR, at 25°C in a KCl liquid cell connected to a water bath for temperature control, while monitoring the disappearance of the Rh(I) and formation of the Rh(III) carbonyl peaks. This reaction was also followed using the UV-vis of the dilute rhodium complexes in quartz cuvettes on the  , on a glassy carbon working-electrode, at 25°C, and a scan rate of 100 mV s À 1 . Right: cyclic voltammogram of 2, in acetonitrile on a glassy carbon working electrode at 25°C and at scan rates of 100-500 mV s À 1 (100 mV increments). Fig. 16. Graph illustrating the linear relationship between the anodic and cathodic peak currents and (scan rate) 1/2 for ligand 2 as an example.

Table 2
The data obtained for a 0.2 mM solution of the organophosphorus ligands (1-3) in CH 3 CN/0.1 mol dm À 3 [NBu 4 ][PF 6 ] at 25°C, at different scan rates and reference against FcH/FcH þ as the internal standard. The diffusion coefficient, D, E pa (anodic peak potential) as well as i pa (anodic peak current and, E pc (cathodic peak potential) peak for each compound is shown.

Name
No. D for i pa and i pc (cm 2 s À 1 ) ʋ/mV s À 1 E pa /mV i pa /mA E pc /mV       Table 4 Kinetic rate constants, activation parameters and Pauling electronegativity (χ R ) for the UV/vis-monitored reaction between CH 3 I and 4, 5 and 6.
No. χ X Temperature (°C) k 1 (dm 3 mol À 1 s À 1 ) ΔH* (J mol À 1 ) ΔS* (J mol À 1 K À 1 ) ΔG* (J mol À 1 ) a Shimadzu UV/Vis spectrometer. At least four temperatures ranges between 15 and 45°C was monitored, from which the activation parameters ΔH * and ΔS * were obtained. Chloroform was used as solvent and passed through basic alumina just before use to make it acid free. All kinetic measurements were monitored under pseudo first-order conditions with a 500-2000 times molar excess of CH 3 I over the concentration of the rhodium complex. Pseudo first-order rate constants, k 1 , were calculated using MicroMath Scientist 2.0 program. Fig. 22. Left: the absorbance vs time graph measuring the decrease in vibration height (2085 cm À 1 ) vs time was used to determine k obs . Right: the methyl iodide concentration dependence of the oxidative addition reaction between CH 3 I and Rh (H 3 CCOCHCOCH 3 )CO(C 6 H 5 OPPh 2 ), (4), as monitored by FTIR.

Table 5
Kinetic rate constants and Pauling electronegativity (χ X ) for the FTIR-monitored reaction between CH 3 I and 4, 5 and 6.