390 Full Paper Received: 26 November 2010 Revised: 6 January 2011 Accepted: 6 January 2011 Published online in Wiley Online Library: 4 April 2011 (wileyonlinelibrary.com) DOI 10.1002/aoc.1779 Synthesis of new boron complexes: application to transfer hydrogenation of acetophenone derivatives Ahmet Kilic a * , Cezmi Kayan b , Murat Aydemir b , Feyyaz Durap b , Mustafa Durgun a , Akın Baysal b , Esref Tas c and Bahattin G ¨ umg ¨ um b Two new boron complexes were synthesized from N-[3-(methylmercapto)aniline]-3,5-di-tert-butylsalicylaldimine (LH) with boron reagent BPh 3 or BF 3 .Et 2 O. These boron complexes are stable and easily soluble in protic solvents such as ethanol (C 2 H 5 OH) but hardly soluble in nonprotic solvents such as chloroform (CHCl 3 ), dichloromethane (CH 2 Cl 2 ) and tetrahydrofuran (THF). All new boron complexes have been fully characterized by both analytical and spectroscopic methods. The catalytic activities of complexes [LBPh 2 ], 2, and [LBF 2 ], 3, in the transfer hydrogenation of acetophenone derivatives were tested. Stable boron complexes were found to be efficient catalysts in the transfer hydrogenation of aromatic ketones in good conversions up to 99% in the presence of iso-PrOH/KOH. Copyright c  2011 John Wiley & Sons, Ltd. Keywords: boron complexes; transfer hydrogenation; BPh 3 ; BF 3 .Et 2 O; synthesis Introduction Boron is essential for healthy plants. Its biochemical role is not fully understood even 60 years after its recognition as an essential element, although it is known to be involved in nucleic acid synthesis, possibly linked to adequate provision of pyrimidine nucleotides. Boron also plays a part in carbohydrate metabolism, hormone action and membrane formation. [1] Its complexes with conjugated light-emitting π -systems have recently received considerable attention due to their potential use in organic light- emitting devices (OLEDs) [2,3] as well as fluorescent probes for proton or heavy metal ion detection. [4] There are three main types of fluorine–boron complexes, classified as N,N bidentate, N,O bidentate and O,O bidentate compounds (Scheme 1). For the former two kinds of fluorine-boron complexes, BODIPY (boradipyrromethane) and 1,3,2-dioxaborine are their correspond- ing representatives. [5] Four-coordinate organoboron compounds have been extensively investigated in the past decade as emissive materials for use in OLEDs, because of their high thermal and chemical stability. [6,7] In contrast to three-coordinate boron com- pounds, which can function as a Lewis acid or an electron-transport material in optoelectronic devices through the empty p orbital of the boron center, [8] four-coordinate organoboron compounds can also function as electron-transport materials by means of the boron-stabilized π ∗ orbital of the conjugated chelate ligands. [7,8] It is known that boron is strongly electrophilic by virtue of its tendency to fill the vacant orbital and complete the octet, so in contrast to organometallic compounds, organoboron compounds are in general more stable owing to the increased covalency of B ← O and B ← N bonds. Thus, boron complexes may pro- vide extra stability to counteract the instability of C N bonds in salicylaldimines as catalyts compounds. In this paper, we report the synthesis, characterization and catalytic activity in transfer hydrogenation of aromatic ketones of the two boron complexes bearing BPh 2 or BF 2 and ligand (LH). We have found that both steric and electronic factors have a significant impact on the catalytic properties of this class of molecules. Experimental All reagents and solvents were of reagent-grade quality and obtained from commercial suppliers (Aldrich or Merck). IR spectra were recorded on a Perkin Elmer Spectrum 100 FT-IR spectrometer as KBr pellets. 1 H (400.1 MHz) and 13 C NMR (100.6 MHz) spectra were recorded on a Bruker AV 400 spectrometer, with δ referenced to external tetramethylsilane (TMS). Elemental analysis was carried out on a Fisons EA 1108 CHNS-O instrument. Electronic spectral studies were conducted on a Perkin-Elmer model Lambda 25 UV–vis spectrophotometer in the wavelength range from 200 to 1100 nm. Melting points were measured in open capillary tubes with an Electrothermal 9100 melting point apparatus and are uncorrected. GC Analyses GC analyses were performed on a HP 6890N gas chromatograph equipped with a capillary column (5% biphenyl, 95% dimethylsilox- ane; 30 m × 0.32 mm × 0.25 μm). The GC parameters for transfer hydrogenation of ketones were as follows: initial temperature, 110 ◦ C; initial time, 1 min; solvent delay, 4.48 min; temperature ∗ Correspondence to: Ahmet Kilic, Harran University, Department of Chemistry, 63190, Sanliurfa, Turkey. E-mail: kilica63@harran.edu.tr a Harran University, Department of Chemistry, 63190, Sanliurfa, Turkey b Dicle University, Department of Chemistry, 21280 Diyarbakır, Turkey c Siirt University, Department of Chemistry, 56100 Siirt, Turkey Appl. Organometal. Chem. 2011, 25, 390–394 Copyright c  2011 John Wiley & Sons, Ltd.