Available online at www.sciencedirect.com Journal of Organometallic Chemistry 693 (2008) 349–356 www.elsevier.com/locate/jorganchem Note Cyclometallated platinum(II) complexes containing the chiral ligand [2-(diphenyl-phosphanyl)-benzylidene]-(1-phenyl-ethyl)-amine: Synthesis and molecular structures of the compounds [PtCl(Me){j2-(R)-Ph2P(C6H4)CH@NCH(Ph)Me-P,N}] and [Pt{j3-(S)-Ph2P(C6H4)CH@NCH(C6H4)Me-P,N,C}Py]BF4 Paola Ramı́rez a, Raúl Contreras a,*, Mauricio Valderrama a, Daniel Carmona b, Fernando J. Lahoz b, Ana I. Balana b a Departamento de Quı́mica Inorgánica, Facultad de Quı́mica, Pontificia Universidad Católica de Chile, Casilla 306, Santiago 6094411, Chile b Departamento de Quı́mica Inorgánica, Instituto de Ciencia de Materiales de Aragón, Instituto Universitario de Catálisis Homogénea, Universidad de Zaragoza-CSIC, 50009 Zaragoza, Spain Received 22 August 2007; received in revised form 18 October 2007; accepted 18 October 2007 Available online 25 October 2007 Abstract Diastoreoisomeric mixtures of the complex [PtIMe3{j2-Ph2P(C6H4)CH@NCH(Ph)Me-P,N}] (Rc-1) react with AgBF4 and SMePh to give a mixture of complexes [PtMe(SMePh){j2-Ph2P(C6H4)CH@NCH(Ph)Me-P,N}]BF4 (2) and [Pt{j3-Ph2P(C6H4)CH@NCH(C6H4)Me-P,N,C}(PhSMe)]BF4 (3) which subsequently render the corresponding chloride compounds [PtClMe{j2-(R)-Ph2P(C6H4)CH@ NCH(Ph)Me-P,N}] (4) and [PtCl{j3-(R)-Ph2P(C6H4)CH@NCH(C6H4)Me-P,N,C}] (5), by elution with CH2Cl2 on a aluminium oxide chromatography column. Refluxing of [PtIMe3{j2-Ph2P(C6H4)CH@NC*H(Ph)Me-P,N}] (Sc-1) with AgBF4 in a 1:1, CH2Cl2:Me2CO mixture followed by the addition of SMePh, NCMe or pyridine (Py) affords the corresponding cyclometallated compounds [Pt{j3(S)-Ph2P(C6H4)CH@NCH(C6H4)Me-P,N,C}(L)]BF4 [L = SMePh (3), NCMe (9), Py (10)]. These compounds have been characterised by analytical and spectroscopic means and by the molecular structure determination of complexes 4 and 10.  2007 Elsevier B.V. All rights reserved. Keywords: Trimethylplatinum; Chiral Schiff base complexes; Reductive elimination reactions; Cyclometallated platinum complexes 1. Introduction In the last decades the chemistry of cyclometallated transition metal complexes has attracted much interest [1]. In particular, cyclometallated complexes of Group 10 elements have been extensively studied due to their behaviour as versatile starting materials for organic synthesis [2–4], photochemistry [5,6], homogeneous catalysis [7], liquid crystal [8], asymmetric synthesis [9] and optical resolution [10,11] purposes. * Corresponding author. Fax: +562 6864744. E-mail address: rcontrer@puc.cl (R. Contreras). 0022-328X/$ - see front matter  2007 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2007.10.032 Diarylplatinum(II) complexes containing labile dialkylsulfide ligands, of the type {PtR2(l-SMe2)}2 are suitable materials for preparing cyclometallated platinum(II) compounds. Thus, their reaction with iminic ligands, derived from halobenzylamines [12], N,N 0 -dimethylethylendiamine [13] or (S)-a-methylbenzylamine [14] and a variety of aldehydes, affords cyclometallated compounds through C–X (X = H, Cl, Br, I) bond activation. Moreover, taking advantage of the presence of Pt–N and Pt–C donor bonds, related cyclometallated Pt(IV) derivatives can be easily obtained from them by oxidative addition of alkyl halides [15]. In addition, cycloplatination of these type of ligands can be promoted by other platinum(II) substrates such as 350 P. Ramı́rez et al. / Journal of Organometallic Chemistry 693 (2008) 349–356 cis-[PtCl2(DMSO)2] [16] or [Pt(dba)2] (dba = dibenzylideneacetone) [17]. Recently, we reported that the reaction of diastereoisomeric mixtures of the complex [PtIMe3{j2-Ph2P(C6H4)CH@NCH(Ph)Me-P,N}] with AgBF4 in the presence of PPh3 renders the cyclometallated complex [Pt{j3-Ph2P(C6H4)CH@NCH(C6H4)Me-P,N,C}(PPh3)][BF4] via consecutive reductive elimination and orthometallation processes. However, when pyridine (Py) was used instead of PPh3 only the reductive elimination step occurred and [PtMe(Py){j2-Ph2P(C6H4)CH@ NCH(Ph)Me-P,N}][BF4] was the product obtained [18]. Following our interest in the synthesis and reactivity of orthometallated Pt(II) complexes, in this note we report a more direct method for the synthesis of cyclometallated compounds of formula [Pt{j3-Ph2P(C6H4)CH@NCH(C6H4)Me-P,N,C}(L)][BF4]. The molecular structures of complexes [PtClMe{j2-(R)-Ph2P(C6H4)CH@NCH(Ph)Me-P,N}] and [Pt{j3-(S)-Ph2P(C6H4)H@NCH(C6H4)MeP,N,C}Py]BF4 are also reported. 2. Experimental 2.1. General All reactions were carried out by standard Schlenk techniques under a dry nitrogen atmosphere. Reagent grade solvents were dried, distilled, and stored under a nitrogen atmosphere. The starting complex [PtIMe3]4 [19], the ligands (S)- and (R)-Ph2PC6H4CH@NCH(Ph)Me [20] and diastereomeric mixtures of the complex [PtIMe3{j2Ph2P(C6H4)CH@NCH(Ph)Me-P,N}] (1) [18] were synthesized according to literature procedures. 1H, 31P{1H} and 13 C{1H} NMR spectra were recorded on a Bruker AC200P and Avance-400 spectrometers. Chemical shifts are reported in ppm relative to SiMe4 (1H, 13C) and 85% H3PO4 in D2O (31P) (positive shifts downfield) as internal and external standards, respectively. Elemental analyses (C, H, N, S) were carried out with a Fisons EA-118 microanalyser. 2.2. Synthesis of the complexes 2.2.1. [PtClMe{j2-(R)-Ph2P(C6H4)CH@NCH(Ph)Me-P,N}] (4) and [PtCl{j3-(R)-Ph2P(C6H4)CH@ NCH(C6H4)Me-P,N,C}] (5) Complex (Rc-1, 150.6 mg, 0.198 mmol) in a mixture dichloromethane-acetone (1:1, 20 mL) was treated with AgBF4 (40.9 mg, 0.210 mmol). After stirring the mixture for 1 h at room temperature, the AgI formed was removed by filtration. The filtrate was vacuum-evaporated to dryness and the solid residue was dissolved in dichloromethane (25 mL). To the resulting solution thioanisole (23.3 lL, 0.198 mmol) was added. The mixture was stirred under reflux for 1 h. After cooling, the resulting solution was vacuum-concentrated. Addition of diethyl ether gave a yellow solid (125.8 mg), which was characterized by 1H and 31 P{1H} NMR spectroscopy as a mixture of [PtMe{j2(R)-Ph2P(C6H4)CH@NCH(Ph)Me-P,N}(SMePh)][BF4] [2; 101.9 mg (81%); 1H NMR (CDCl3)d 8.51 (s, 3JHPt = 43.3 Hz, 1H, CH@N), 5.45 (q, 3JHH = 6.8 Hz, 1H, C*H), 2,77 (s, 3JHPt = 29.8 Hz, 3H, MeS), 1.52 (d, 3H, C*Me), 0.26 (d, 3JHP = 3.3 Hz, 2JHPt = 69.1 Hz, 3H, PtMe). 31 P{1H} NMR (CDCl3): d 17.26 (s, 1JPPt = 1812.2 Hz)] and [Pt{j3-(R)-Ph2P(C6H4)CH@NCH- (C6H4)Me-P,N,C}(SMePh)][BF4] [3; 23.9 mg (19%); NMR: see Section 2.2.2]. The solid residue was dissolved in dichloromethane and chromatographed on neutral aluminium oxide in diethyl ether. A yellow band, eluted in dichloromethane, was collected. This solution was vacuum-evaporated to dryness giving complex 4 as a pale yellow solid. A second yellow band, eluted in ethanol, was collected and vacuum-evaporated to dryness to give complex 5 as a yellow solid. Compound 4. Yield: 50.3 mg (61.8%). Anal. Calc. for C28H27ClNPPt: C, 52.6; H, 4.3; N, 2.2. Found: C, 52.2; H, 4.1; N, 2.1%. 1H NMR (CDCl3): d 8.10 (s, 3JHPt = 39.0 Hz, 1H, CH@N), 6.89 (q, 3JHH = 6.8 Hz, 1H, C*H), 1.53 (d, 3H, C*Me), 0.63 (d, 3JHP = 3.5 Hz, 2JHPt = 72.2 Hz, 3H, PtMe). 31P{1H} NMR (CDCl3): d 15.31 (s, 1 JPPt = 4712.2 Hz). Compound 5. Yield: 16.3 mg (85.9%). Anal. Calc. for C27H23ClNPPt: C, 52.1; H, 3.7; N, 2.3. Found: C, 51.9; H, 3.5; N, 2.1%. 1H NMR (CDCl3): d 8.51 (s, 3JHPt = 119.3 Hz, 1H, CH@N), d 5.25 (q, 3JHH = 6.7 Hz, 3 JHPt = 49.1 Hz, 1H, C*H), 1.54 (d, 3JHH = 6.7 Hz, 3H, C*Me). 31P{1H} NMR (CDCl3): d 17.30 (d, 1JPPt = 1883.2 Hz). 2.2.2. [Pt{j3-(S)-Ph2P(C6H4)CH@NCH(C6H4)MeC,N,P}(L)]BF4 {L = SMePh (3), NCMe (9), Py (10)} Complex (Sc-1, 150.6 mg, 0.198 mmol) and AgBF4 (40.9 mg, 0.210 mmol) were stirred under reflux for 4 h in dichloromethane:acetone (30 mL, 1:1). The AgI formed was removed by filtration. The filtrate was vacuum-evaporated to dryness and the residue dissolved in dichloromethane. To the solution the corresponding L was added (L = SMePh (23.3 lL, 0.198 mmol), NCMe (21.1 lL, 0.400 mmol), Py (16.1 lL, 0.200 mmol). The mixture was stirred under reflux for 2 h and the resulting solution vacuum-concentrated. Addition of diethyl ether gave a pale yellow solid. Compound 10 was recrystallised from dichloromethane:diethyl ether. Compound 3. Yield: 71.3 mg (48.8%). Anal. Calc. for C34H31NPPtSBF4: C, 51.1; H, 3.9; N, 1.8; S, 4.0. Found: C, 50.9; H, 4.3; N, 1.6; S, 3.8%. 1H NMR (CDCl3): d 9.05 (s, 3JHPt = 114.1 Hz, 1H, CH@N), 5.73 (q, 3 JHH = 6.5 Hz, 3JHPt = 50.7 Hz, 1H, C*H), 2,85 (s, 3 JHPt = 55.2 Hz, 3H, MeS), 1.68 (d, 3H, C*Me). 31P{1H} NMR (CDCl3): d 17.81(s, 1JPPt = 1808.4 Hz). Compound 9. Yield: 53.4 mg (40.8%). Anal. Calc. for C29H26N2PPtBF4: C, 48.7; H, 3.7; N, 3.9. Found: C, 49.1; H, 3.9; N, 3.6%. 1H NMR (CDCl3): d 8.80 (s, 3 JHPt = 124.2 Hz, 1H, CH@N), 5.55 (q, 3JHH = 6.6 Hz, 3 JHPt = 48.9 Hz, 1H, C*H), 2.25 (d, 5JHP = 1.5 Hz, P. Ramı́rez et al. / Journal of Organometallic Chemistry 693 (2008) 349–356 3 JHPt = 15.4 Hz, 3H, NCMe), 1.51 (d, 3 H, C*Me). P{1H} NMR (CDCl3): d 17.33 (s, 1JPPt = 1772.6 Hz). Compound 10. Yield: 78% (95 mg). Anal. Calc. for C32H28N2PPtBF4: C, 51.01; H, 3.74; N, 3.72. Found: C, 50.86; H, 3.58; N, 3.70%. Atom numbering for compound 10 is as follows: 31 Ph1 H3 H4 C6 P Pt C2 C5 C8 A C1 N CB H6 C Ph2 H 12 C7 C3 C4 H5 N C CH3 =C C12 C9 C11 H11 C10 H10 HA H9 HB 1 H NMR (CDCl3, room temperature): d 8.97 (s, 1H, HA, JHPt = 104 Hz), d 8.16 (m, 1H, H9), d 7.79 {t, 1H, (Py: Hp)3 JHH = 6.9 Hz}, d 7.71 (m, 3H, H10 + H11 + H12), d 7.26 [m, 4H, {H6 + (Py: 2Hm + 1Ho)}], d 7.17 (t, 1H, H5, 3 JHH = 7.4 Hz), d 6.95 (t, 1H, H4,3JHH = 7.4 Hz), d 6.13 (st, 1H, H3,3JHH = 6.4 Hz, 4JHP = 6.2 Hz, 3JHPt = 34.7 Hz); d 5.66 (c, 1H, HB, 3JHBHC = 6.6 Hz, 3JHPt = 44.8 Hz), d 1.77 (d, 3H, HC,3JHCHB = 6.6 Hz,); Ph1: d 7.87 (d, 1H, H2, 3 JH2H3 = 11 Hz), d 7.88 (d, 1H, H6, 3JH6H5 = 11 Hz), d 7.53 {(m, 4H, H3 + H4 + H5 + (Py: 1Ho)}; Ph2: d 7.06 (d, 1H, H2, 3JH2H3 = 11 Hz), d 7.07 (d, 1H, H6, 3JH6H5 = 11 Hz), d 7.39 (st, 1H, H4, 3JH4H3 = 3JH4H5 = 6 Hz), d 7.26 (m, 2H, H3 + H5). 13C{1H} NMR (CDCl3, room temperature): d 165.8 (d, 1C, CA, 3JCP = 5.9 Hz), d 85.3 (s, 1C, CB), d 29.3 (s, 1C, CC), d 157.2 (d, 1C, C2, 2JCP = 109 Hz), d 150.2 (s, 1C, C1), d 130.9 (s, 1C, C3,), d 126.8 (s, 1C, C5), d 125.8 (d, 1C, C4, 4JCP = 7 Hz), d 120.4 (d, 1C, C6, 3 JCP = 5 Hz), d 124.0 (d, 1C, C7, 1JCP = 44 Hz), d 130.9 (d, 1C, C8, 2JCP = 18 Hz), d 139.2 (d, 1C, C9, 3JCP = 9 Hz), d 133.5 (s, 1C, C10), d 133.1 (d, 1C, C11, 3JCP = 2 Hz), d 134.2 (d, 1C, C12, 3JCP = 6 Hz), {Py: d 152.4 (s, 2C, 2C0), d 138.9 (s, 1C, Cp), d 127.1 (s, 2C; 2Cm)}; Ph1: d 130.1 (d, 1C, C1, 1JCP = 48 Hz) d 134.38 (d, 2C, C2 + C6, 2JC2P = 2 JC6P = 14 Hz), d 132.56 (s, 1C, C4), d 129.88 (d, 2C, C3 + C5, 3JC3P = 3JC3P = 11 Hz)]; Ph2: d 126.5 (d, 1C, C1, 1 JCP = 51 Hz) d 132.0 (d, 2C, C2 + C6, 2JC2P = 2JC6P = 11 Hz), d 131.27 (s, 1C, C4), d 129.31 (d, 2C, C3 + C5, 3 JC3P = 3JC3P = 10 Hz)], 31P{1H} NMR (CDCl3, room temperature): d 18.67 (s, 1JPPt = 1844 Hz, 1P, P–Pt), 19 F{1H} NMR (CDCl3, room temperature): d 79 ppm. 3 2.3. Crystal structure determination of complexes 4 and 10 Suitable crystals for X-ray diffraction were grown by slow diffusion of n-pentane into THF (4) or toluene (10) solutions of the complexes. Intensity data were collected for both compounds at low temperature (100(2) K) on a Bruker SMART APEX area detector diffractometer 351 equipped with graphite-monochromated Mo Ka radiation (k = 0.71073 Å) and using x narrow frames (0.3). The SMART software package was used for data collection [21a]. Lorentz, polarisation and absorption corrections were applied on raw frame data with SAINT [21b] and SADABS [21c] programmes. The structures were solved by direct methods and refined on F2 by full-matrix least-squares techniques using the SHELXTL suite of programmes [21d]. All non-hydrogen atoms were refined with isotropic and subsequent anisotropic displacement parameters. All hydrogen atoms (except those of the two methyl groups) were included in 4 from observed positions and refined as free isotropic atoms; those of the methyl groups were obtained from geometric considerations and refined riding on carbon atoms. In the case of 10, all hydrogens were included from calculated positions and refined with thermal and positional riding parameters. The absolute configuration of the two molecules was estimated from the refinement of the absolute structure Flack parameter (x) [21e]. A summary of crystal data and refinement parameters is reported in Table 1. 3. Results and discussion 3.1. Synthesis and characterization of the complexes Treatment of diastereomeric mixtures of [PtIMe3{j2Ph2P(C6H4)CH@NCH(Ph)Me-P,N}] (Sc-1) [18] with silver tetrafluoroborate followed by addition of thioanisol gives rise to a mixture of complexes 2 and 3 (Scheme 1). Formation of compounds 2 and 3 from Sc-1 implies a common step involving the reductive elimination of ethane and iodide abstraction but, while complex 2 retains the remaining Me–Pt group (dMe = 0.26 ppm, 2JHPt = 69.1 Hz, 3 JHP = 3.3 Hz), complex 3 can be described as the result of a further elimination of methane accompanied by an orthometallation reaction. Complex 3 was isolated as a pure sample by a direct preparative route (see below). Therefore, the mixture was characterized and quantified by 1H NMR spectroscopy. Attempts to separate this mixture by column chromatography on aluminium oxide were unsuccessful. Instead, and the new chloride complexes, 4 and 5, were obtained. The formation of these complexes is probably due to the presence of traces of hydrochloric acid originated from the dichloromethane used as eluent in the chromatography column. We recently reported the preparation of the related complexes 7 and 8, following a similar route, but using pyridine 7 or triphenylphosphine 8 as ancillary ligands (Scheme 2) [18]. It has been proposed the solvate 6 as a common intermediate for the formation of both types of products [18]. It seems that triphenylphosphine promotes the elimination of methane from 6 whereas other donor ligands such as pyridine stabilise this intermediate avoiding further reaction steps. The mixture of compounds 2 and 3 obtained by using thioanisol indicates that this ligand would occupy an intermediate position in this reaction pattern. 352 P. Ramı́rez et al. / Journal of Organometallic Chemistry 693 (2008) 349–356 Table 1 Crystallographic data and structure refinement for compounds 4 and 10 Compound 4 10 Empirical formula Formula weight Crystal system Space group Unit cell dimensions a (Å) b(Å) c (Å) b () V (Å3) Z Dcalc (Mg m 3) Absorption coefficient (mm 1) F(0 0 0) Crystal size (mm) h Range data collection () Index ranges C28H27ClNPPt 639.02 Monoclinic P21 C32H28BF4N2PPt 753.43 Monoclinic P21 8.6976(6) 14.4583(10) 10.5402(7) 108.2050(10) 1259.11(15) 2 1.685 5.757 9.3557(7) 19.8924(15) 15.0843(11) 90.7580(10) 2807.1(4) 4 1.783 5.108 624 0.28 · 0.26 · 0.11 2.03–28.44 11 6 h 6 11, 19 6 k 6 19, 13 6 l 6 14 14,792 5808(Rint = 0.0199) 5808/1/353 1.043 R1 = 0.0167, wR2 = 0.0399 R1 = 0.0174, wR2 = 0.0402 0.014(4) 1472 0.27 · 0.17 · 0.02 1.35–28.54 12 6 h 6 12, 26 6 k 6 26, 20 6 l 6 20 34,085 13005(Rint = 0.0461) 13005/1/741 1.002 R1 = 0.0357, wR2 = 0.0723 R1 = 0.0435, wR2 = 0.0752 0.005(5) 0.615 and 1.332 and Reflections collected Independent reflections Data/restraints/parameters Goodness-of-fit Final R indices [I > 2r(I)] R indices (all data) Absolute structure parameter Largest difference peak and hole (e Å 3) 0.471 1.509 At this point, searching for a general route to orthometallated compounds, we envisaged the possibility of forcing methane elimination from intermediate 6 in the absence of any additional donor ligand. Bearing this goal in mind, the metathetic reaction of Sc-1 with silver tetrafluoroborate was carried out in a refluxing 1:1, dichloromethane:acetone mixture, for four hours. After separation by filtration of the silver iodide formed, addition of thioanisole, acetonitrile or pyridine afforded the corresponding orthometallated complexes (Scheme 3). The new complexes 2–5, 9 and 10, were characterised by analytical and spectroscopic means and by the molecular structure determination of complexes 4 and 10. The most noticeable features of their 1H NMR spectra are a low field singlet in the 8.10–9.05 ppm region assigned to the amine proton and a quartet at 5.25–6.90 ppm and a doublet at 1.51–1.77 ppm corresponding to the HC*Me protons. Notably, while in complexes 2 and 4, the 3JPtH coupling constant for the amine proton is around 40 Hz, it takes a value on the range 104–124 Hz in the orthometallated complexes 3, 5, 9, and 10 [22,23]. Most probably, the low value of the 3JHPt coupling constant of complexes 2 and 4 is due to the presence of a methyl group in a trans disposition to the HC@N fragment; the change of the coordination mode of the chelate phosphino-amine ligand from bidentate to orthometallated tridentate accounts for this significant difference. Resonances corresponding to the ancillary ligand are also present. Thus, one doublet at 0.26 ppm, 2JHPt = 69.1 Hz (complex 2) and at 0.63 ppm, 2JHPt = 72.2 Hz (complex 4) is assigned to the Me–Pt protons. The MeS protons resonate as a singlet at 2.85 ppm, 3JHPt = 55.2 Hz (complex 3) and a doublet at 2.25 ppm, 5JHP = 1.5 Hz, is attributed to the methyl acetonitrile protons of complex 9. The 31P{1H} NMR spectra consist in a singlet at ca. 17.5 ppm. The 1JPPt coupling constants are characteristic for Pt(II) compounds with a carbon atom trans to a phosphorus (from 1773 to 1881 Hz) [24] or to a chloride (4713.0 Hz) [22,25] atom. The 13C{1H} NMR spectra of compounds show a very complex pattern. For complex 10 the signals were assigned + H Ph H Ph * * Me N Me N SMePh Cl iii) Pt Pt P Ph2 Me H Me Ph Me Me Pt Me Me 4 2 ii) i) + I * N P Ph2 PPh2 + Me Me H H N 1 * * iv) N Pt P Ph2 Pt SMePh 3 P Ph2 Cl 5 Scheme 1. Preparative route to complexes 4 and 5. Only the RC isomers are shown. (i) 1. AgBF4, 1 h, r.t.; 2.SMePh, reflux, 1 h; CH2Cl2/(CH3)2CO. (ii) Al2O3 (column). (iii) CH2Cl2. (iv) CH3CH2OH. 353 P. Ramı́rez et al. / Journal of Organometallic Chemistry 693 (2008) 349–356 + H Ph * Me N Py ii) Pt Me Me Pt i) I * N H Ph Me Me Me * Ph H P Ph2 + Me 7 N Solvent PPh2 Pt P Ph2 H * iii) 6 + Me Me N 1 Pt P Ph2 PPh3 8 Scheme 2. Preparation of complexes 7 and 8 according to Ref. 18. (i) AgBF4, 1 h, r.t., CH2Cl2/(CH3)2CO or CH2Cl2/THF ( –AgI, –CH3CH3). (ii) Py, CH2Cl2, reflux, 2 h. (iii) PPh3, CH2Cl2, reflux, 2 h (–CH4). Me H Me Me Pt * Ph Me Me i) I * N + H N PPh2 Pt P Ph2 L L = SMePh (3), NCMe (9), Py (10) 1 Scheme 3. Preparation of the cyclometallated complexes 3, 9, and 10. (i) 1. – AgBF4, CH2Cl2/(CH3)2CO, reflux, 4 h (– AgI, –CH3–CH3, –CH4). 2. – L, CH2Cl2, reflux, 2 h. 2 31 with the aid of D experiments ( P-HMQC, HMQC, HMBC and NOESY). The 13C{1H} NMR data show that the phenyl groups bonded to the phosphorus atom are not equivalent, and the satellites signals due to 13C–195Pt coupling are not observed. Ph1 N 3.2. X-ray molecular structures of compounds 4 and 10 A perspective view of the molecular structure of complex 4 is shown in Fig. 1, while that of the cation of complex 10 is shown in Fig. 2. Relevant bond distances and bond angles are given in Table 2. Ph2 P C C7 C Pt C2 C [1JCP = 44 Hz], respectively. The high value of the carbonphosphorus coupling observed for the carbon atom bonded to the metal centre (C2) is attributed to the trans influence of the phosphorus atom [22,24a,26]. Moreover, two doublet signals at d 130.1 [1JCP = 48 Hz] and 126.5 ppm [1JCP = 51 Hz] are assigned to the phenyl carbon atoms (Ph1 y Ph2) bonded to the phosphorus atom, respectively. Finally, the 13C NMR spectrum shows a doublet signal corresponding to the iminic carbon (CA) at d 165.8 ppm [3JCP = 5.9 Hz]. C1 C8 N = CA C CB C C The 13C{1H} NMR spectrum shows a singlet and three doublet signals corresponding to the quaternary carbon atoms C1, C2, C8 and C7, which appear at d 150.2, 157.2 [2JCP = 109 Hz], 130.9 [2JCP = 18 Hz] and 124.0 ppm Fig. 1. Molecular structure of complex 4 with the labelling scheme used. 354 P. Ramı́rez et al. / Journal of Organometallic Chemistry 693 (2008) 349–356 Fig. 2. Molecular structure of the cationic complex 10 with the labelling scheme used. In both complexes the platinum atom shows a distorted square-planar environment. In complex 4 the (R)-ligand [2(diphenylphosphine)benzylidene]-(1-phenyl-ethyl)-amine is bonded to the metal centre through the nitrogen and the phosphorus donor atoms; a chlorine atom and a methyl group complete the metal coordination sphere. Complex 10 consists of a fused (6,6,5,6) tetracycle system containing five and six-membered metallacycles, with the platinum atom coordinated in an analogous manner to that observed in 4 – to the nitrogen and phosphorus atoms of the phosphine-amine chelate ligand – but also bonded to an ortho-methallated phenyl group of the corresponding (S)phenyl-ethyl-amine moiety. A nitrogen atom of a pyridine group completes the square-planar coordination of the metal. The metal coordination bond distances show the high trans influence of the alkyl (4) and aryl (10) ligands. Thus, the Pt–P bond length is 2.1791(7) Å in 4 when the phosphorus is trans to a chloride ligand, but 2.2900(12) Å when it is trans to the phenyl group (10); the Pt–N bond distance is 1.996(5) Å in 10 where the amine group is trans to the pyridine ligand and 2.138(3) Å when the nitrogen atom is situated trans to the methyl group (4). Nevertheless, the Pt–C bond distances are identical in both structures (mean 2.043(3) Å) and similar to the values reported for analogous platinum (II) complexes [12,13,16,27]. The bite angle of the bidentate ligand P–Pt–N(1) ranges from 87.48(7) in 4 to 92.08(16) in one of the independent Table 2 Selected bond distances and angles for 4 and 10 Complex 10a Complex 4 Bond distances (Å) Pt–Cl Pt–P Pt–N(1) Pt–C(28) P(1)–C(1) N(1)–C(7) N(1)–C(8) C(1)–C(2) C(2)–C(7) C(8)–C(9) C(8)–C(10) C(10)–C(11) Bond angles () Cl–Pt–P Cl–Pt–N(1) Cl–Pt–C(28) P–Pt–N(1) P–Pt–C(28) N(1)–Pt–C(28) Pt–P–C(1) Pt–N(1)–C(7) Pt(1)–N(1)–C(8) C(7)–N(1)–C(8) P–C(1)–C(2) C(1)–C(2)–C(7) N(1)–C(7)–C(2) N(1)–C(8)–C(9) N(1)–C(8)–C(10) C(8)–C(10)–C(11) a 2.3693(8) 2.1791(7) 2.138(3) 2.047(3) 1.821(3) 1.276(4) 1.512(4) 1.409(4) 1.468(5) 1.520(5) 1.506(5) 1.390(6) 176.51(3) 91.55(7) 87.09(10) 87.48(7) 94.03(10) 177.08(13) 108.64(10) 126.8(2) 117.5(2) 115.7(3) 120.0(2) 124.9(3) 127.5(3) 110.0(3) 110.8(3) 118.5(4) Pt–N(2) Pt–P(1) Pt–N(1) Pt–C(11) P(1)–C(1) N(1)–C(7) N(1)–C(8) C(1)–C(2) C(2)–C(7) C(8)–C(9) C(8)–C(10) C(10)–C(11) N(2)–Pt–P(1) N(2)–Pt–N(1) N(2)–Pt–C(11) P(1)–Pt–N(1) P(1)–Pt–C(11) N(1)–Pt–C(11) Pt(1)–P(1)–C(1) Pt(1)–N(1)–C(7) Pt(1)–N(1)–C(8) C(7)–N(1)–C(8) P(1)–C(1)–C(2) C(1)–C(2)–C(7) N(1)–C(7)–C(2) N(1)–C(8)–C(9) N(1)–C(8)–C(10) C(8)–C(10)–C(11) Pt(1)–C(11)–C(10) Two crystallographic independent molecules were observed in the asymmetric unit of 10. 2.026(5) 2.2922 (17) 2.000(6) 2.035(6) 1.820(6) 1.273(8) 1.499(8) 1.394(9) 1.474(9) 1.509(9) 1.498(10) 1.406(9) 92.47(16) 170.7(2) 93.2(2) 92.08(16) 174.35(19) 82.3(2) 110.2(2) 128.9(5) 114.4(4) 116.5(6) 120.2(5) 126.6(6) 132.0(7) 110.0(5) 108.1(5) 117.5(6) 113.2(5) 2.010(5) 2.2879(16) 1.991(6) 2.047(6) 1.817(6) 1.287(9) 1.494(8) 1.402(8) 1.482(9) 1.526(9) 1.507(9) 1.386(9) 92.64(15) 176.7(2) 97.1(2) 89.17(16) 170.18(19) 81.0(2) 105.5(2) 129.2(5) 112.3(4) 118.1(6) 119.2(5) 126.4(6) 126.6(6) 108.7(5) 105.7(5) 117.7(6) 112.0(5) P. Ramı́rez et al. / Journal of Organometallic Chemistry 693 (2008) 349–356 molecules of 10; these values compare well with those of the closely related palladium complex [PClMe{Ph2P(C6H4)CH@NR*-P,N}] (R* = 1-mesitylethyl) (86.4(2)) [27] and are common for structurally related phosphinoamine metal complexes containing the same P,N-bidentate fragment Ph2P(C6H4)CR@NR 0 (range 85.7(3)–90.0(5)) [27–29]. These values indicate the reduced flexibility of this ligand and also its adequacy to orthogonal chelate coordination. The six-membered metalacycles Pt–P–C(1)–C(2)–C(7)– N(1) are not planar but twisted with significant puckering amplitudes. In the case of 4 a screw-boat 1S2 conformation is observed (Q = 0.702(2) Å, h = 62.7(3), / = 25.2(3)) with the –C6H4CH@ unit above the metal coordination plane (Fig. 1). For the two independent molecules in 10 analogous half-chair 4H5 conformations are observed (Q = 0.438(3) Å, h = 124.5(4), / = 214.3(5) and Q = 0.693(4) Å, h = 118.4(5), / = 210.1(6)) with the carbon atoms C(1), C(2) and C7 below the metal coordination plane (Fig. 2) [30]. If we compare the phosphine–amine conformation in 4 with that observed in 10, the major geometrical alterations affect the torsion angles around the N(1)–C(8) and C(8)– C(10) single bonds, which are modified to allow approximation of C(11) atom to bonding distances of the Pt metal (C(7)–N(1)–C(8)–C(10) 58.3(4) in 4, 151.5(8) in 10; N(1)–C(8)–C(10)–C(11) 79.9(5) in 4, 18.6 (9) in 10). The five-membered metallacycle formed in 10 after orthometallation at C(11) adopt a slightly puckered envelope conformation with the nitrogen atom out of the ring plane (Q = 0.224(4) Å, / = 43.7(6) and Q = 0.361(3) Å, / = 34.4(3)) [30]. An additional noteworthy feature detected in 10 is the p–p interaction between the co-ordinated pyridine ligand and one of the free phosphine phenyl groups (C(21)– C(26)). These aromatic rings show a typical p–p interaction with a nearly parallel disposition of their planes (mean dihedral angle 16.4(2)) and with a short interplanar separation (centroid–centroid 3.603(3) Å) [31]. Acknowledgement We thank ‘‘Fondo de Desarrollo Cientı́fico y Tecnológico’’ (FONDECYT), Chile, for financial support (Grant 1030520). Appendix A. Supplementary material CCDC 647957 and 647958 contain the supplementary crystallographic data for 4 and 10. These data can be obtained free of charge via http://www.ccdc.cam.ac.uk/ conts/retrieving.html, or from the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. 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