Chapter 7 Experimental

Chapter 7 Experimental 7 Experimental 7.1 General Procedures All manipulations of metal complexes and air sensitive reagents were performed under an inert atmosphere of nitrogen either by the use of standard Schlenk and vacuum line techniques or in a nitrogen-filled glove box. Solutions were transferred using double ended needles (cannulae) and gas tight syringes. Glassware and double ended needles were oven dried at 160°C overnight. All reagents, including 1 5 N labelled compounds, were purchased from Sigma-Aldrich Pty. Ltd., except dimethylphenylphosphine, triallylphosphine, 1,2-bis (dimethylphosphino)ethane, and 1,2-bis (diethylphosphino)ethane, which were purchased from Strem Chemicals, Inc. and used as received. For the purposes of air sensitive manipulations and in the preparation of metal complexes, diethyl ether, tetrahydrofuran, hexane, toluene and benzene were stored over sodium wire and distilled prior to use from sodium/benzophenone ketyl under nitrogen. Methanol was dried over and distilled from magnesium turnings. Acetone was dried over and distilled from CaSO 4 . Dimethylformamide was dried over activated molecular sieves. Absolute ethanol, 2-methoxyethanol, 2,2-dimethoxypropane and anhydrous chloroform were used as received. - 221 - Chapter 7 Experimental All bulk compressed gases were obtained from British Oxygen Company (BOC Gases). Argon (>99.99%) and nitrogen (>99.5%) were passed through drying columns of potassium hydroxide before use. Methyl bromide (>95%), carbon monoxide (>98%) and dihydrogen (>99%) were used as supplied. Vinyl bromide was purchased from Sigma-Aldrich and used as supplied. Air sensitive NMR samples were either prepared in a nitrogen-filled glove-box or by transferring the solutions by double ended needles through an air tight septum seal. Deuterated solvents for NMR purposes were obtained from Merck and Cambridge Isotopes, degassed using three consecutive freeze-pump-thaw cycles and vacuum distilled from suitable drying agents. All deuterated solvents were distilled immediately prior to use. 1 H, 1 1 B, 1 3 C, 1 5 N and 3 1 P NMR spectra were recorded on Bruker Avance spectrometers (proton frequency = 300.13, 400.13 or 500.13 MHz). NMR Spectra were recorded at 300 K unless otherwise stated as determined using a variable temperature unit ( ±5 K). Chemical shifts ( δ) are quoted in ppm, the downfield direction being positive. 1 H and 1 3 C chemical shifts are referenced to internal solvent resonances. 1 5 N NMR chemical shifts were referenced to external neat aniline, taken to be 56.5 ppm at 300 K (liquid ammonia scale). 3 1 P NMR chemical shifts were referenced to external neat trimethylphosphite, taken to be at 140.85 ppm at 300 K. - 222 - Chapter 7 Experimental 1 1 B NMR chemical shifts were referenced to external 15% BF 3 .Et 2 O in CDCl 3 . Variable temperature NMR spectra are uncorrected for chemical shift drift with changing temperature. Uncertainties in chemical shifts (at 298/300 K) are typically ±0.02 ppm for 1 H, ±0.1 ppm for 1 3 C and 3 1 P, and ±0.2 ppm for 1 1 B and 1 5 N. Coupling constants ( J) are given in Hz and have an uncertainty of ±0.05 Hz. For convenience, the following abbreviations are used in reporting NMR resonances: s, singlet; d, doublet; t, triplet; q, quartet; p, pentet; hex., hexet; sept., septet; dd, doublet of doublets, etc; m, multiplet; b., broad; app., apparent. The following two-dimensional NMR techniques were used for the assignment of some organometallic compounds: COSY ( COrrelation Spectroscop Y), HSQC ( Heteronuclear Single-Quantum Coherence), HMQC ( Heteronuclear Multiple-Quantum Coherence), EXSY ( EX change Spectroscop Y). T 1 measurements were carried out by the inversion-recovery method using standard 180°-τ-90° pulse sequences. NMR data were processed on Intel PC workstations using standard Bruker software (XWinNMR/TopSpin). Accurate chemical shift and coupling constant values of cis unsymmetrical complexes were determined via simulations carried out using the NUMARIT routines (NUMARIT algorithm as described in: J. S. Martin and A. R. Quirt, J. Magn. Reson. 5, 318 (1971), modified by Rudy Sebastian) built into SpinWORKS 2.5.4 (© 1999-2006 Kirk Marat). Phosphine labelling for unsymmetrically substituted cis complexes was kept consistent for all spectra, with a labelling scheme as shown in Figure 7.1. The phosphine position trans to - 223 - Chapter 7 Experimental the coordinated chloride was labelled position A whilst the remaining 2 phosphine positions were determined via J (PP) measurements. PC PB Cl Ru PA X PD Figure 7.1 – Phosphine labelling for unsymmetrical cis complexes prepared in this work Electrospray ionisation (ESI) and atmospheric pressure chemical ionisation (APCI) mass spectra were recorded on a Finnigan LCQ mass spectrometer. Typical experimental conditions for an ESI experiment were: ESI spray voltage 5 kV; nitrogen sheath gas pressure 60 psi; heated capillary temperature 200 °C; full scan m/z 50 to 2000. For loop injection, the typical mobile flow phase was 50% methanol/50% water with 1% acetic acid with a flow rate of 100 microliter per minute. Matrix assisted laser desorption / ionisation – time of flight (MALDI-TOF) spectra were recorded on a Micromass TOF SPEC 2E spectrometer with a 337 nm dinitrogen UV laser, using C 6 0 /C 7 0 soot as both the matrix and as an internal calibrant ( m/z = 720 and 840, two-point calibration). Ions with molecular masses greater than 720 generally required a calibration of a + higher order, and when available known [RuCl(P-P) 2 ] (P-P = dmpe, depe) ions were used along with C 6 0 /C 7 0 in a three-point calibration curve. Both - 224 - Chapter 7 Experimental positive and negative ions were detected in reflectron mode at 20kV. A typical sample was prepared by spotting a solution of the analyte of interest in a suitable solvent on a marked stainless steel plate in an N 2 -filled glove box, allowing the solvent to evaporate to dryness, then coating the sample with a saturated solution of C 6 0 /C 7 0 in toluene, which was also allowed to evaporate to dryness. Typical spotting volumes were ca. 4 µL. Care was taken to minimise air contact ( ca. <8 s) when transferring the sample plate from the glove box to the spectrometer vacuum chamber. Data is quoted in the form x(assignment, y) where x is the mass/charge ( m/z) ratio and y is the percentage abundance relative to the base peak. Only peaks of interest are quoted. Infrared spectra were obtained either on a Shimadzu 8400 series FTIR spectrometer as pressed discs (KBr – hand press), or as powder samples on a Bruker IFS 66/S FT-IR with MIR light source and DTGS detector operating in ATR reflection mode. Raman spectra were collected on a Bruker IFS 66/S-FRA 106/S at 1064 nm as neat solid discs. For convenience, the following abbreviations are used in reporting IR data: w, weak; m, medium; st, strong; b, broad; sh, sharp. Collection of Raman spectra was hampered by the decomposition of most intensely coloured complexes, even at low (< 5 mW) powers. Compounds which were white to yellow gave spectra with a good signal to noise ratio, whilst compounds which were green to blue generally “burned”, occasionally giving signal, but most frequently resulting in an extremely - 225 - Chapter 7 Experimental large and asymmetric baseline “hump” ranging from 3580–1500 cm − 1 with a maxima at 3216 cm − 1 . 7.2 Ligand synthesis 1 7.2.1 Trichlorophosphine sulfide, PSCl 3 Sulfur powder (49.1 g, 1.53 mol) and phosphorus trichloride (211 g, 1.53 mol) were added to a two-necked round-bottom flask. A reflux condenser and nitrogen line were attached and the system sparged with nitrogen. Anhydrous aluminium trichloride (2.40 g, 18.0 mmol) was added through the side-arm in small portions to the cooled solution; after each addition the solution was heated to reflux, and cooled before further addition of AlCl 3 . Upon addition of sufficient AlCl 3 ( ca. 2.5 g), a vigorous exothermic reaction occurred, producing a dark brown homogenous solution. The solution was heated at reflux for a further 30 minutes, and the resulting mixture was distilled under nitrogen (123 − 125 °C) to afford trichlorophosphine sulfide as a colourless liquid (206 g, 80%). 3 1 1 P{ H} NMR (162 MHz, diethyl ether): δ P 30.5 (1P, s) 7.2.2 Methylmagnesium iodide, MeMgI Magnesium turnings (81.7 g, 3.36 mol) was added to a 3 L wide-necked flange flask and a 5-necked flange cover was secured, to which an overhead mechanical stirrer, 1 L dropping funnel, reflux condenser and a - 226 - Chapter 7 Experimental nitrogen/vacuum line were attached. The entire flask was evacuated overnight to activate the magnesium turnings. Diethyl ether (1 L) was added along with a single crystal of iodine. Methyl iodide (452 g, 3.18 mol) in diethyl ether (200 mL) was added slowly (1 mL / min) to the Mg/ether mixture, and the mixture heated without stirring until the reaction initiated, as indicated by the fading of the iodine colour from solution. Once the reaction had commenced, the mixture was stirred, heating was ceased and the MeI addition adjusted to maintain a gentle reflux. After complete addition, the reaction mixture was a dark grey solution, with traces of excess magnesium. The mixture was allowed to stir overnight and used directly in the next step. 7.2.3 Tetramethyldiphosphine disulfide, 2 Me 2 P(=S)-P(=S)Me 2 The reaction vessel from the preparation of methylmagnesium iodide was cooled to 0 °C. Additional diethyl ether (400 mL) was added and trichlorophosphine sulfide (163 g, 0.960 mol) was added dropwise over four hours, during which a thick, white precipitate formed.

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