Alkenyl-functionalized NHC iridium-based catalysts for hydrosilylation w

A family of alkenyl-functionalized N-heterocyclic-carbene–iridium(I) complexes has been synthesized, providing a series of mono-coordinated, bis-chelate and pincer alkenyl-NHC species. Olefin coordination is highly influenced by the nature of the substituents on the NHC ring, and on the length of the alkenyl branch. A fluxional process involving coordination/decoordination of the olefin in bis-allyl-NHC complexes has been studied, and the activation parameters have been determined by means of VT-NMR spectroscopy. The mono-coordinated complexes are highly active in the hydrosilylation of terminal alkynes, showing high selectivity for the Z-isomers, with no a-isomers or dehydrogenative silylation processes being observed. The molecular structures reported that are representative of the species have been determined by means of X-ray crystallography.

5.2 Line shape analysis data for complex 1a signal at 6.9 ppm. 5.3 Line shape analysis data for complex 1a signal at 6.7 ppm.

6.-Ligand precursors
Supplementary Material (ESI) for New Journal of Chemistry This journal is © The Royal Society of Chemistry and The Centre National de la Recherche Scientifique, 2007 3

1.-General Procedures.
Syntheses and catalytic experiments were carried out under aerobic conditions and without solvent pretreatment. Reagents and solvents (reagent grade) commercially available were used as received unless otherwise stated. NMR spectra were recorded on Variant spectrometers operating at 300 or 500 MHz ( 1 H NMR) and 75 and 125 MHz ( 13 C NMR), respectively, and referenced to SiMe 4 (δ in ppm and J in Hertz). NMR spectra were recorded at room temperature with CDCl 3 unless for the VT-NMR analyses. Assignments are based on 1 H, 13 C, APT and COSY experiments. A QTOF I (quadrupole-hexapole-TOF) mass spectrometer with an orthogonal Z-spray-electrospray interface (Micromass, Manchester, UK) was used. The drying gas as well as nebulizing gas was nitrogen at a flow of 400L/h and 80 L/h respectively. The temperature of the source block was set to 120 ºC and the desolvation temperature to 150ºC. A capillary voltage of 3.5 KV was used in the positive scan mode and the cone voltage was set to 30V. Mass calibration was performed using a solution of sodium iodide in isopropanol:water (50:50) from m/z 150 to 1000 a.m.u. Sample solutions (aprox 1x10 -4 M) in dichlormethane:methanol (50:50) were infused via syringe pump directly connected to the interface at a flow of 10 μl/min. A 1 μg/mL solution of 3,5-diiodo-L-tyrosine was used as lock mass. Elemental analyses were carried out in a Euro EA 3000 Eurovector Analyser.

2.-Catalytic studies.
Hydrosilylation reactions were carried out in Schlenk tubes under aerobic conditions. In a typical experiment, alkyne (1 Eq.), dimethylphenylsilane (1 Eq.), catalyst (1 mol %), ferrocene (0.1 Eq.; Internal reference) and 10 ml of CHCl 3 , were stirred at room temperature or 60 ºC for 24 h. Conversion and isomer distribution was monitored by 1 H NMR. Several aliquots of 0.5 mL were taken at the desired sampling time.
Supplementary Material (ESI) for New Journal of Chemistry This journal is © The Royal Society of Chemistry and The Centre National de la Recherche Scientifique, 2007  and 230 respectively) were collected at 0.3º intervals and 40 s per frame.