FULL PAPER DOI: 10.1002/ejic.200801104 Late Transition-Metal Complexes of 2-Ph 2 PC 6 H 4 NHC(O)CH 2 NHCO 2 Bz: Observation of Three Distinct Ligation Modes (κ 1 -P,κ 2 -P/N and κ 3 -P/N/N') Mark R. J. Elsegood, [a] Andrew J. Lake, [a] and Martin B. Smith* [a] Keywords: Coordination modes / Metallacycles / P ligands / Late-transition metals The one-step synthesis of the amide-functionalised tertiary phosphane 2-Ph 2 PC 6 H 4 NHC(O)CH 2 NHCO 2 Bz (Bz = CH 2 Ph), 2·HH, by condensation of the known aminophos- phane, 2-Ph 2 PC 6 H 4 (NH 2 )(1), with N-(benzyloxycarbonyl)- glycine and dicyclohexylcarbodiimide (DCC) in THF at room temperature is reported. The new ligand 2·HH displays vari- ous coordination modes when complexed to a range of late transition-metal precursors. Hence κ 1 -P-coordination for 2·HH is observed in the complexes ClAu(2·HH)(3), MCl 2 (η 5 - Cp*)(2·HH) (M = Rh 4; Ir 5), RuCl 2 (η 6 -p-cymene)(2·HH)(6), Pd(κ 2 -CN-C 12 H 12 N)Cl(2·HH)(7) and MCl 2 (2·HH) 2 (M = Pd 8; Pt 9). Treatment of 8 or 9 with tBuOK in CH 3 OH gave the bis-κ 2 -P/N-chelate complexes cis-M{2-Ph 2 PC 6 H 4 NC(O)CH 2 - NHCO 2 Bz} 2 (M = Pt 10; Pd 11) in which both monoanionic ligands 2·H – are disposed in a cis geometry. The related nickel(II) complex cis-Ni{2-Ph 2 PC 6 H 4 NC(O)CH 2 NHCO 2 - Bz} 2 (12) was prepared from NiCl 2 ·6H 2 O, 2 equiv. of 2·HH and tBuOK in refluxing CH 3 OH. Reaction of the piano-stool Introduction Coordination compounds of tridentate and tetradentate ligands continue to attract much interest for their variable ligating capabilities, [1–3] stabilisation of G-quadruplex DNA, [4] sensor, [5] magnetic [6] and luminescent [7–9] proper- ties and catalytic applications. [10] Various donor atom com- binations have been documented that contain at least one phosphorus donor atom and include for example P/N/C, [11] P/C/N, [12] P/N/N, [13] P/N/O, [14] P/N/S, [15] P/N/P [16] and P/N/ Se. [17] Pincer ligands based on P/C/P [18] or P/Si/P [19] donor sets afford interesting complexes, display unusual reactivity and find applications in catalysis. Furthermore, P/O/O and P/O/P ligands have been employed in self-assembly reac- tions. [20,21] More recently the use of one or two soft sele- nium donor atoms in tridentate ligands of the type Se/N/O and Se/C/Se have been documented. [22,23] One of the most common methods for the synthesis of potentially tridentate ligand systems usually involves a Schiff base condensation reaction. [24] This method is par- [a] Department of Chemistry, Loughborough University, Loughborough, Leics, LE11 3TU, UK Fax: +44-1509-223925 E-mail: m.b.smith@lboro.ac.uk Supporting information for this article is available on the WWW under http://www.eurjic.org or from the author. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2009, 1068–1078 1068 complex 5 with tBuOK in CH 3 OH gave the chiral-at-metal complex Ir(η 5 -Cp*){2-Ph 2 PC 6 H 4 NC(O)CH 2 NCO 2 Bz} (14), present in solution as two diastereomers. A single-crystal X- ray diffraction study of 14 confirmed the κ 3 -P/N/N'-tridentate coordination mode. Under similar conditions the chiral- at-metal ruthenium(II) complex Ru(η 6 -p-cymene){2- Ph 2 PC 6 H 4 NC(O)CH 2 NCO 2 Bz} (15) was prepared in which 2 2– functions efficiently as a dianionic tridentate ligand. All new compounds have been characterised by multinuclear NMR [ 31 P{ 1 H}, 1 H], FT-IR, EI-MS, ES-MS and microanalysis. Furthermore, the X-ray structures of ten compounds have been determined and reveal, in the majority of cases, a strong propensity for the –NHC(O)CH 2 NHCO 2 Bz group to engage in N–H···N, N–H···O and N–H···Cl hydrogen bond- ing. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) ticularly applicable to P/N/N and P/N/O ligands. Many of these ligands bind to metals in a neutral κ 3 -tridentate fash- ion or ligate in a singly deprotonated form. Examples of κ 3 - tridentate ligands that utilise all three donor centres in a doubly deprotonated form are uncommon. [15] Herein, we report the synthesis of an unsymmetrical κ 3 -P/N/N'-ligand and demonstrate the flexible ligation behaviour of this new ligand (in its neutral, monoanionic and dianionic forms) through complexation studies towards linear, pseudo-tetra- hedral and square-planar transition-metal centres. All com- pounds have been characterized by multinuclear NMR and FT-IR spectroscopy and in ten cases by single-crystal X-ray diffraction studies. Results and Discussion Ligand Synthesis The new ligand 2-Ph 2 PC 6 H 4 NHC(O)CH 2 NHCO 2 Bz (Bz = CH 2 Ph) (2·HH) was synthesised in moderate yield (36%) by condensation of the amine-functionalised tertiary phos- phane 2-Ph 2 PC 6 H 4 (NH 2 )(1) with N-(benzyloxycarbonyl)- glycine and DCC in THF (Scheme 1). Purification of the crude material comprising 2·HH and unreacted 1 was read- ily accomplished by recrystallisation from CH 2 Cl 2 /Et 2 O.