摘要:
J. CHEM. SOC. DALTON TRANS. 1992 225 1Cyclometallation Reactions of 6 4 2-Thienyl) -2,2'- bipyridinewith d8 Transition Metal lonstEdwin C. Constable,*re Roland P. G. Henney/ Paul R. Raithbya and Lynn R. Sousaba University Chemical Laboratory, L ensfield Road, Cambridge CB2 I E W, UKDepartment of Chemistry, Ball State University, Muncie, IN 47306, USAThe potentially terdentate ligand 6- (2-thienyl) -2,2'-bipyridine (Hthbipy) reacts with [MCI,I2- (M = Pdor Pt) under mild conditions to give cyclometallated complexes in which the thienyl ring is metallated at the3 position. The metallated complexes [M(thbipy)CI] (M = Pd or Pt) react with trimethyl phosphite togive phosphonate complexes [M(thbipy){P(=O) (OMe),}] and with Na[acac] (Hacac = acetylacetone)to give [M(thbipy) (acac)] with a C-bonded acac ligand.Under mild conditions, the non-metallatedcompound [Pd(Hthbipy)CI,] can be isolated. In contrast, the reaction of Hthbipy with Na[AuCI,] atambient temperature yields the non-metallated complex [Au( Hthbipy)CI,], but upon heating this, orperforming the reaction at higher temperatures, the metallated compound [Au(thbipy)CI,] is obtained.X-Ray structural analysis of this complex reveals it to be dimeric where the ligand has metallated at th_e5 position of the thienyl ring and adopts a bridging bidentate N,C mode [triclinic, space group PI,a=9.271(5), 6=14.214(10), c=16.194(10) A, a=108.11(5), ~=96.55(5),y=111.46(5)", Z = 2 ,R = 0.075, R' = 0.0941.Cyclometallated compounds contain chelated ligands in whichone of the donor sites is an anionic carbon centre.", Thephotochemical and photophysical properties of such com-pounds have been extensively investigated in recent years, andexamples incorporating a wide combination of donor atomsare known.A particularly common structural feature is aligand in which the anionic carbon donor centre is generated bydeprotonation of a C-H bond of an aromatic ring bonded to aheteroaryl ring; the latter acts as the heteroatom donor. Themajority of examples of cyclometallated complexes which havebeen described are with d8 or d6 transition metals andincorporate a five-membered chelate ring, although specificexamples with other ring sizes are known.The ligand 2-(2-thienyl)pyridine (Hthpy) may act as amonodentate N-donor and it has recently been demonstratedthat the thiophene ring may be cyclometallated at C3 toyield complexes with interesting photophysical and electronicproper tie^.^,^ We have independently been studying a series of2-(2-thienyl)pyridine derivatives as part of a wider investigationinto the preparation of cyclometallated complexe~,~ and haveshown that the ligand 6-(2- thieny1)-2,2'- bipyridine (Hth bipy)may co-ordinate to a metal ion in a number of differentmanner^.^,^ In this paper we describe the interaction of Hthbipywith platinum(Ir), palladium(r1) and gold(rI1) compounds; wehave briefly described some aspects of the interaction of gold(w)with Hthbipy previou~ly.~.~ExperimentalInfrared spectra were recorded on Perkin-Elmer 1710 orPhilips PU9624 Fourier-transform spectrophotometers, withthe samples in compressed KBr discs, proton and 31P NMRspectra on Bruker WM-250 or AM400 spectrometers. Fastatom bombardment (FAB) and electron-impact (EI) massspectra were recorded on a Kratos MS-50 spectrometer, with3-nitrobenzyl alcohol as matrix for the FAB spectra.Thecompounds Na[AuCl,], K2[PdCl,], K,[PtCl,] and [{ Pd-t Supplementary data available: see Instructions for Authors, J. Chem.SOC., Dalton Trans., 1992, Issue 1, pp. xx-xxv.(O,CMe),} 3] (Johnson Matthey) were used as supplied; 6-(2-thienyl)-2,2'-bipyridine was prepared by the literature m e t h ~ d . ~Preparations.-[Pd(thbipy)Cl]. A solution of Hthbipy(0.016 g, 0.066 mmol) in acetonitrile (1.5 cm3) was added to asolution of K2[PdC14] (0.022 g, 0.066 mmol) in water (1 cm3)and heated to 60" C for 2 h, during which period a yellow solidprecipitated.This solid was filtered off and air-dried to give[Pd(thbipy)Cl] (0.026 g, 99%). Recrystallisation from dimethylsulfoxide (dmso) yielded small orange needles (Found: C, 44.75;H, 2.4; C1,9.3; N, 7.2. Calc. for Cl4H9C1N2PdS: C, 44.35; H, 2.4;C1, 9.35; N, 7.4%). FAB mass spectrum: m/z 378 ([Pd(thbipy)-Cl]} and 343 ([Pd(thbipy)]}. IR (KBr): 1594s, 1557m, 1493s,1459m, 1434m, 872m, 766s, 644m and 370w cm-'.[Pt(thbipy)Cl]. A solution of K,[PtCl,] (0.085 g, 0.205mmol) in water (4 cm3) was added to a solution of Hthbipy(0.050 g, 0.21 mmol) in acetonitrile (3 cm3) and heated to 60 "Cfor 20 h, during which period a brown solid precipitated. Thissolid was filtered off, washed with water and MeCN, and air-dried to give [Pt(thbipy)Cl] (0.086 g, 97%) (Found: C, 35.7; H,2.1; C1,4.75; N, 5.8.Calc. for C,,H,ClN,PtS: C, 35.9; H, 2.0; Cl,7.6; N, 5.8%). FAB mass spectrum: m/z 468 ([Pt(thbipy)Cl])and 432 {[Pt(thbipy)]}. IR (KBr): 1600s, 1554m, 1494s, 1459m,1438m, 881m, 764s, 647m and 343w cm-'.[ Pd( thbipy ){ P( OMe), 011. A solution of [Pd( t hbip y)Cl](0.019 g, 0.05 mmol) in CH2C12 (4 cm3) was added to a solutionof P(OMe), (6.0 pl) in CH2C12 (3 cm3) and stirred at 30 "C for5 h. After this period the solvent was removed in V ~ C U O to givea yellow-brown solid. This solid was recrystallised by thediffusion of diethyl ether vapour into a CH,Cl, solution to give[Pd(thbipy){ P(OMe),O}] as small yellow needles (0.021 g,93%) (Found: C, 42.15; H, 3.2; N, 6.1.Calc. for CI6H,,-N,O,PPdS: C, 42.45; H, 3.35; N, 6.2%. FAB mass spectrum: m/z453 ([Pd(thbipy){ P(OMe),O)]) and 343 { [Pd(thbipy)]}. IR(KBr): 1592s, 1559m, 1492s, 1459m, 1436m, 1131s, 1091m,1016vs, 869m, 778s, 739m, 721s and 571m cm-'.[Pt(t h bipy) { P( OMe),O)]. A solution of [Pt(thbipy)Cl](0.041 g, 0.088 mmol) in CH2C12 (4 cm3) was added to asolution of P(OMe), (5.0 pl) in CH,Cl, (3 cm3) and stirred at30 "C for 5 h. After this period the solvent was removed in uacuoto give an orange solid. This solid was recrystallised by th2252 J. CHEM. SOC. DALTON TRANS. 1992diffusion of diethyl ether vapour into a CH2C12 solution to give[Pt(thbipy){P(OMe),O}] as small orange needles (0.038 g,80%) (Found: C, 34.7; H, 2.8; N, 4.95.Calc. for C16H15-N,03PPtS: C, 34.7; H, 2.8; N, 5.0%). FAB mass spectrum: m/z541 ([Pd(thbipy){P(OMe),O}]). IR (KBr): 1596s, 1559m,1491s, 1459m, 1438m, 1380m, 1133s, 1021vs, 778s, 741m, 721sand 576 cm-'.[Pd(thbipy)(acac)]. A solution of Na[acac] in methanol[prepared by the addition of excess of acetylacetone (Hacac) toa freshly prepared sodium methoxide solution made fromsodium (0.012 g, 0.5 mmol) and methanol ( 5 cm3)] was addedto a suspension of [Pd(thbipy)Cl] (0.053 g, 0.14 mmol) inmethanol (4 cm3) and stirred at 30 "C for 2 d. After this periodthe solvent was removed in uacuo, and the yellow-brown residuewashed with water and a small amount of methanol.The yellowsolid was filtered off and air-dried to give [Pd(thbipy)(acac)](0.060 g, 97%) (Found: C, 51.65; H, 3.6; N, 6.2. Calc. forC19H,6N,02PdS: C, 51.55; H, 3.65; N, 6.35%). FAB massspectrum: m/z 343 {[Pd(thbipy)]}. IR (KBr): 1667s, 1644m,1618m, 1595s, 1493m, 1459m, 1400m and 769s cm-'.[Pt(thbipy)(acac)]. A solution of Nacacac] in methanol[prepared by the addition of excess of Hacac to a freshlyprepared sodium methoxide solution made from sodium(0.006 g, 0.25 mmol) and methanol (3 cm3)] was added to asuspension of [Pt(thbipy)Cl] (0.017 g, 0.036 mmol) in methanol(4 cm3) and the solution stirred at 30 "C for 2 d. After this periodthe solvent was removed in uacuo, and the brown residue washedwith water and a small amount of methanol.This solid wasrecrystallised by the diffusion of diethyl ether vapour into aCH,Cl, solution to give orange-brown needles of [Pt(thbipy)-(acac)] (0.014 g, 73%) (Found: C, 42.25; H, 3.1; N, 5.2. Calc. forspectrum: m/z 532 {[Pt(thbipy)(acac)]} and 432 {[Pt(thbipy)]}.IR (KBr): 1676s, 1655m, 1637m, 1594m, 1466m, 1383m and767s cm-'.[Pt(thbipy)(MeCN)] [PF6]. A suspension of [ Pt( thbipy)Cl](0.018 g, 0.038 mmol) in acetonitrile ( 5 cm3) and water (1 cm3)was heated to reflux for 3 h. After this period the solution wasfiltered hot, and the filtrate treated with [NH,][PF,] (0.5 g) togive a brown precipitate. This brown product was filtered off,washed with water and dried in U ~ C U O to give [Pt(thbipy)-(MeCN)][PF,] (0.015 g, 63%). FAB mass spectrum: m/z 473([Pt(thbipy)(MeCN)]}.IR (KBr): 1600m, 1553w, 1497m,1466m, 1441m, 840vs, 809m and 773ms cm-'.[Pd(Hthbipy)Cl,]. A solution of Hthbipy (0.071 g, 0.30mmol) in acetonitrile (3 cm3) was added to a stirred suspensionof K,[PdCl,] (0.098 g, 0.30 mmol) in water (2 cm3) and stirredat 10 "C for 3 h, after which period an orange solid hadprecipitated. This was filtered off, washed with water and driedin uamo to give [Pd(Hthbipy)Cl,] (0.123 g, 98%) (Found: C,40.0; H, 2.45; N, 6.95. Calc. for C14H10C12N2PdS: C, 40.45; H,2.45; N, 6.75%). FAB mass spectrum: m/z 379 {[Pd(thbipy)Cl]}and 343 {[Pd(thbipy)]}. IR (KBr): 1599m, 1556m, 1490m,1455s, 773s, 758m, 745m, 347m and 329m cm-'.Conuersion of [ Pd(Hthbipy)Cl,] into [ Pd(t h bipy)Cl].Method 1. A solution of [Pd(Hthbipy)Cl,] in dmso waswarmed to 40 "C.Upon cooling, orange crystals of [Pd(thbipy)-CI] identical in all respects to the material obtained earlierwere obtained.Method 2. A suspension of [Pd(Hthbipy)Cl,] (0.018 g, 0.043mmol) in water-MeCN (1 : 1, 4 cm3) was warmed to 50 "C for2 h. Upon cooling, orange-yellow crystals of [Pd(thbipy)Cl]identical in all respects to the material obtained earlier wereobtained.Method 3. A suspension of [Pd(Hthbipy)Cl,] in CH2C1, washeated to reflux for 1.5 h. After filtration to remove unreacted[Pd(Hthbipy)Cl,], treatment of the yellow filtrate with hexanegave orange-yellow crystals of [Pd(thbipy)Cl] identical in allrespects to the material obtained earlier.[Au(Hthbipy)Cl,]. A solution of Hthbipy (0.145 g, 0.61mmol) in acetonitrile (3 cm3) was added to a solution ofC19H16N202PfS: C, 42.85; H, 3.05; N, 5.25%).FAB massNaCAuCl,] (0.22 g, 0.061 mmol) in water ( 5 cm3) and thesolution heated to 45 "C for 5 h, with the addition of water (3cm3) over this period. An orange solid was deposited over the5 h, which was filtered off and air-dried to give [Au(Hthbipy)-CI,] (0.288 g, 87%). Recrystallisation from dimethyl sulfoxideyielded small orange needles (Found: C, 30.9; H, 1.85; N, 5.3.Calc. for C,4H10A~C13N2S: C, 31.05; H, 1.85; N, 5.15%). IR(KBr): 1587m, 1565m, 1450s, 815m, 770s, 716m and 364m cm-'.[{Au(thbipy)Cl,},]. Method 1. A solution of Hthbipy(0.024 g, 0.10 mmol) in acetonitrile (1.5 cm3) was added to astirred solution of Na[AuCl,] (0.036 g, 0.10 mmol) in water(2 cm3) and heated to 100°C for 5 h.After this period, theorange-brown solid was filtered off and air-dried to give[{Au(thbipy)Cl,},] (0.05 g, 95%) (Found: C, 33.15; H, 1.9; N,5.4. Calc. for Cl4H9AuCl2N2S: C, 33.25; H, 1.8; N, 5.55%). IR(KBr): 1588m, 1561m, 1445s, 770s and 691m cm-'.Method 2. A suspension of [Au(Hthbipy)Cl,] (0.10 g, 0.185mmol) in 1 : 1 aqueous acetonitrile (8 cm3) was heated to 100 "Cfor 6 h. After this period the orange-brown solid was filtered offand air-dried to give [{Au(thbipy)Cl,},] (0.077 g, 83%).Crystal Structure Determination of [{Au(thbipy)Cl,},].-Poor quality single crystals of [ { Au(thbipy)Cl,} ,] wereobtained by the slow diffusion of diethyl ether vapour into asolution of the compound in dimethylformamide.Crystal data.C2,H 18AU2C14N4S2 + disordered solvent,irregular red blocks, crystal size 0.22 x 0.25 x 0.30 mm,M = 1010.3 + disordered solvent, triclinic, space group Pi,a = 9.271(5), b = 14.214(10), c = 16.194(10) A, a = 108.11(5),p = 96.55(5), y = 111.46(5)", U = 1824(2) A3, F(OO0) = 944,2 = 2, D, not measured, D, = 1.84 g ~ m - ~ , Mo-Ka radiation(h = 0.710 73 A), p(Mo-Ka) = 8.464 mm-'.Data collection and processing. A suitable red single crystalof [(Au(thbipy)Cl,},] was mounted on a glass fibre. All geo-metric and intensity data were taken using a Siemens R3m/Vdiffractometer equipped with graphite-monochromated Mo-Ka radiation. 5170 Data were collected using a 96-step w 2 8scan over the range 5 < 28 < 45".Three standard reflectionswere measured every 97 scans, and showed no significant loss inintensity during the data collection. The data were corrected forLorentz and polarisation effects and an empirical absorptioncorrection applied (transmission factors: minimum, maximum0.455, 0.7 10). 4668 Independent reflections were collected and2422 with F 2 4a(F) were used in the refinement.Structure analysis and re-nement. The structure was solved bydirect methods followed by iterative application of full-matrixleast-squares refinement and Fourier difference syntheses. Adisordered solvent molecule, for which no chemically reason-able model could be found, was present in the lattice; this wastreated as seven partially occupied carbon sites.Atoms Au, C1and S were refined anisotropically. The last cycle of refinement(249 parameters) gave R' = 0.094, R = 0.075 [w-' = 0 2 ( F ) +0.0040F2] with the largest peak in the final Fourier differencesynthesis being 2.50 e A-3. Structure solutions employedSHELXTL-PLUS on a MicroVax TI computer.8Atomic coordinates and selected bond distances and anglesfor [(Au(thbipy)Cl,},] are in Tables 1 and 2.Additional material available from the Cambridge Crystal-lographic Data Centre comprises H-atom coordinates, thermalparameters and remaining bond lengths and angles.Results and DiscussionThe potentially terdentate ligand Hthbipy has been shown toexhibit a variety of N,N'-, N,N',S- and N,N',C-bonded modesin d6 ruthenium(I1) and rhodium(II1) complexes.' The reactionsof Hthbipy with d8 centres such as palladium(rI), platinum(r1)and gold(r1r) are expected to parallel this range of bondingmodes.The reaction of Hthbipy with an aqueous acetonitrilesolution of K,[PdCl,] at 60 "C results in the deposition of ayellow solid. This yellow solid may be recrystallised as verJ. CHEM. SOC. DALTON TRANS. 1992 2253Table 1 Atomic coordinates ( x lo4) for [{Au(thbipy)Cl,),]X403(2)478( 12)262( 13)-1 872(2)-3 238(15)-455(13)2 739(36)3 077(42)4 404(48)5 78q47)5 584(46)4 073(43)3 777(35)4 541(38)4 297(42)3 226(39)2 534(39)2 828(30)1437(39)646( 3 7)- 364(39)- 392(42)954( 1 1)-3 572(39)Y3 399( 1)- 665( 1)3 782(9)3 210(9)1016(9)4 639(25)5 681(29)6 489(35)6 389(33)5 351(32)4 480(30)3 344(25)3 205(27)2 179(30)1283(28)1501(28)2 566(22)679(27)- 2 405(9)- 436(27)- 1 027(28)- 327(30)1 Oll(8)- 1 052(26)Z6x1)1399(7)- 3 497( 1)- 1 206(7)- 3 629(8)-3 517(7)686(21)769(23)1 126(27)1 426(26)1372(26)971(25)91 l(21)1610(22)1 503(25)722(22)61(23)128(18)- 772(22)- 987(22)-1 893(22)- 2 337(24)-1 669(7)-4 691(22)X- 2 796(48)-3 769(60)- 5 259(65)-6 043(55)-4 977(49)- 5 728(52)- 7 244(56)- 7 886(69)- 6 824(49)- 5 332(48)-4 750(31)-4 218(35)-4 390(39)- 3 lOO(42)-1 743(41)-2 356(12)11 014(155)7 594(157)11 503(490)9 188(135)8 OlO(118)9 951(194)11 920(516)Y- 1 060(3 1)-1 349(40)-1 634(41)-1 560(35)- 1 207(33)- 1 152(35)-1 842(39)- 1 721(45)- 928(34)- 251(33)- 370(22)598(25)877(27)1769(29)2 221(29)4 460( 104)4 620( 107)4 203(321)4 676(88)4 253(79)4 270( 124)3 738(362)1490(9)Z- 5 409(26)- 6 248(36)- 6 368(38)- 5 605(30)- 4 805(28)- 3 985(29)-4 109(33)-3 304(36)-2 504(29)- 2 475(28)-3 216(19)- 1 639(21)- 808(22)- 175(25)-561(24)-1 665(7)6 542(88)5 980(91)6 212(280)6 283(73)6 441(66)6 002( 106)5 741(308)Table 2 Selected bond lengths (A) and angles (") for [{Au(thbipy)-C12}21Au(l)-CI(l) 2.285( 14) Au( 1)-Cl(2) 2.275( 12)Au(l )-N(1) 2.10 l(25) Au( 1)-C(28) 1.959(29)Au(2)-C1(3) 2.255(13) Au(2)-C1(4) 2.279(12)Au(2)-C( 14) 2.002( 3 9) Au(2)-N(3) 2.130(35)Cl(l)-A~(l)-Cl(2) 172.6(5) C1( l)-Au( 1)-N( 1) 89.9( 10)C1(2)-Au( 1)-N( 1) 88.7( 10) C1( l)-Au( 1)-C(28) 88.6( 13)C1(2)-A~(l jC(28) 93.0(12) N(l)-Au(l)-C(28) 177.7(16)C1(3)-Au(2)-C1(4) 173.7(4) C1(3)-Au(2)-C(14) 91.1(12)C1(4)-Au(2 )-C( 14) 92.6( 12) C1(3)-A~(2)-N(3) 87.1(10)C1(4)-Au(2)-N(3) 89.6(10) C(14)-Au(2)-N(3) 176.3(16)Au( 1)-N(1)-C(1) 120.4(28) Au(l)-N( l)-C(5) 125.4(26)small orange crystals by the diffusion of diethyl ether vapourinto a dmso solution.Microanalysis suggests the formulation[Pd(thbipy)Cl] to be appropriate, and the complex is formedin quantitative yield. A comparable reaction of Hthbipy withK,[PtCl,] in boiling aqueous acetonitrile results in theformation of the analogous compound [Pt(thbipy)Cl] as abrown solid in 97% yield.The FAB mass spectra (3-nitrobenzylalcohol matrix) of each of these complexes exhibit peaksassigned to [M(thbipy)Cl]+ (M = Pd, m/z 378; M = Pt, m/z468) and [M(thbipy)]+ (M = Pd, m/z 343; M = Pt, m/z 432),all of which show the expected isotopomer distributions. The IRspectra of the two complexes are almost identical, suggestingthat they possess similar structures. The spectrum of the freeligand Hthbipy exhibits a strong absorption at 853 cm-' whichis a characteristic aromatic C-H out-of-plane deformation of a2-substituted thiophene.' For both the platinum and palladiumcomplexes this band is absent and a new absorption (M = Pd,872; M = Pt, 881 cm-') typical of the out-of-plane C-Hdeformation of a 2,3-disubstituted thiophene is seen.' Thespectra also show single weak but sharp absorptions which areassigned to the M-Cl stretching modes (M = Pt, 343; M = Pd,370 cm-I).The 'H NMR spectra of solutions of the complexes inCD,CI, are sharp and well resolved. In CD3SOCD, solutionsome signals were broadened, but the greater dispersion ofresonances in this solvent allowed facile assignment.There areconsiderable differences between the spectra in the two solvents,but it is possible to recover intact the [Pd(thbipy)Cl] complexesfrom CD3SOCD3 solutions, suggesting that the variations aredue to solvent effects rather than displacement of the chlorideby the CD3SOCD3. Similar solvent effects are observed inthe 'H NMR spectra of [Pd(thbipy)Cl,] and [Pt(bipy)Cl,],and data for these complexes are also included in Table 3.Theco-ordination shifts A6 [ = 6(co-ordinated ligand) - G(freeligand)] are remarkably similar in the two solvents (Table 4).Details of the 'H NMR spectra of the complexes [M(thbipy)Cl](M = Pd or Pt) and Hthbipy in a variety of solvents arepresented in Table 3, and it is clear that those of the palladiumand platinum complexes are very similar. The one-dimensional'H NMR spectrum and the COSY (correlation spectroscopy)spectrum of a CD3SOCD3 solution of [Pd(thbipy)Cl] is shownin Fig. 1. The most noticeable feature is the observation of onlynine resonances in contrast to the 10 seen for Hthbipy. Thelowest-field resonance at 6 8.62 may be unambiguously assignedto H6' of the terminal pyridine ring C3J(H5'H6') 5 Hz]; theCOSY spectrum then allows the sequential assignment of H5',H4' and H3' of this ring.For the central pyridine ring theresonances for H4 and one of either H3 or H5 are coincident; wehave been unable to make an unambiguous assignment of thehigher-field resonance to H3 or H5. No nuclear Overhausereffect (NOE) was observed between H3' of the terminalpyridine ring and any of the central ring protons. However, theco-ordination shifts support the assignment given in Table 3; thealternative assignments of H3 and H5 in the complexes gavewidely varying and inconsistent values (the assignments of H3and H5 for the free ligands is unambiguous). The mostsignificant feature of the spectrum is the presence of only twodoublet resonances for the protons on the thienyl ring.Thesetwo doublets exhibit a coupling constant of 4.7 Hz, whichstrongly suggests that they are to be assigned to H4" and H5" ofthe thiophene (in thiophenes 3J(H2H3) [ = 3J(H4H5)] lies inthe range 4.90-5.80 Hz, whereas 3J(H3H4) is in the range 2.45-4.35 Hz)]." In the case of the platinum complexes some of theresonances exhibit satellites due to coupling with 195Pt. Thesesatellites are particularly noticeable on H6' i3J(Pt-H) 15 Hz, cf:19 Hz for [Pt(thbipy),]), H4" {3J(Pt-H) 19 Hz, cf: 21 Hz for[Pt(thbipy),]), H5" C4J(Pt-H> 5 Hz] and also on H3 and H5c4J(Pt-H) z 12 Hz]. These data are all in accord with theformation of a cyclometallated complex, in which a terdentateligand is bonded to the metal through C3" and the two nitroge2254 J.CHEM. SOC. DALTON TRANS. 1992Table 3 Proton NMR data for complexes of Hthbipy and some related compounds6(3JH"/Hz)c JHPtlHZICompound H6' H5' H4' H3' H3 H4 H5 H3" H4" H5"Hthbipy " 8.67 7.32 7.87 8.56 8.30 7.84 7.70 7.68 7.16 7.45[Pd(thbipy)Cl] " 8.80 7.60 8.05 7.96 7.50 7.84 7.3 1 7.24 7.45(5.1) (5.3, 7.0) (7.6, 7.6) (7.8) (8.1) (8.0, 8.0) (8.1) (4-8) (4.8)(5.0) (5.0, 7.6) (7.9,7.9) (7.9) (4.7) (4.7)(5.5) [14] (5,5. 7.6) (7.6, 7.7) (7.7) (8.2) [12] (8.2,S.l) (8.1) [I41 (4.8) c201 (4.8) C8l(5.2) [l5] (5.4,7.0) (7.8, 7.8) (7.8) (8.1) (8.0,S.O) (8.1) (4.7) c191 (4.7) PIHthbipy 8.70 7.48 8.01 8.45 8.26 7.97 7.97 7.89 7.20 7.69[Pd(thbipy)Cl) 8.62 7.80 8.28 8.49 8.05 8.05 7.60 7.14 7.63[Pt(thbipy)Cl] a 9.03 7.69 8.11 7.91 7.42 7.75 7.28 7.14 7.63[Pt(thbipy)Cl] 8.85 7.91 8.35 8.47 7.98 7.98 7.56 6.97 7.83CPd(biPY)C1,1 " 9.41 7.65 8.15 8.05CPd(biPY)Cl,I 9.12 7.8 1 8.36 8.59CPt(biPY)C121 " 9.80 7.68 8.20 8.06CPt(biPY)C121 9.41 7.84 8.42 8.58[ Pd(thbipy) (PO( OMe),}] '9' 9.6 1 7.58 8.02 7.97 7.55d 7.83 7.31 7.4 1 7.41(4.9) (4.9)[Pt(thbipy)(PO(OMe),)] a*e 9.92 7.57 8.04 7.92 7.53' 7.72 7.26 7.32 7.43[ Pd(t hbipy )(acac)] "J 9.46 7.68 7.99 7.91 7.51 7.8 1 7.31 7.45 7.53c141 c221 c111c231 (4.9) [26] (4.9) [14][ Pt(th bipy)(acac)] " v g 9.61 7.73 8.06 7.88 7.47 7.77 7.33 7.38 7.66[Pt(thbipy)(MeCN)][PF,] 8.56 7.71 8.22 8.03 7.51 7.79 7.24 6.84 7.63[Pd(Hthbipy)CI,] " 9.21 7.57 8.12 7.99 7.96' 8.09 7.72d 7.85 7.20 7.68(5.6) (5.6, 7.7) (7.7, 7.7) (7.7) (7.9)d (7.9) (7.9Id (3.7) (3.7, 5.1) (5.1)(5.9) (5.9, 7.6) (7.6, 7.7) (7.7) (3.7) (3.7, 5.0) (5.0)c121 c171[Au(Hthbipy)CI,] a 9.07 7.78 8.26 8.12 7.95 7.98 7.73 8.04 7.21 7.54[Au(thbipy)Cl,] " 9.09 7.73 8.18 8.07 7.7Sd 7.90 7.65 ' 7.06 7.44(5.5) (4.0) (4.0)(5.7) (5.7, 7.7) (7.7, 7.8) (7.8) (7.8)d (7.8) (7Wd (3.9) (3.9)[Au(thbipy)Cl,] 9.22 7.94 8.41 8.41 8.05 8.05 7.94 6.92 7.69" In CD,CI, solution.11 Hz.In CD,SOCD, solution.' OCH,, 6 3.62, 3J(P-H) 12.2 Hz. Ambiguity in the assignments of H3 and H5. OCH,,6 3.60, ,J(P-H) 11.8 Hz. 'CH,, 6 2.17; CH, 6 4.84. 'CH3, 6 2.19, 4J(Pt-H) 14 Hz; CH, 6 5.52, 'J(Pt-H) 120 HZ. 'CH,, 6 2.64, 4J(Pt-H)Table 4 Proton NMR co-ordination shift (A6) data for complexes of Hthbipy [A6 = 6(co-ordinated ligand) - 6(free ligand)]A6Compound H6' H " H4' H3' H3 H4 H5 H4" H5"[Pd(thbipy)Cl] a +0.13 +0.28 +0.18 -0.60 -0.80 (-0.2') 0.00 -0.39 (- 1.0') + 0.08 0.00[Pd(thbipy)Cl] -0.08 +0.32 +0.27 +0.04 -0.21 (+0.08') 0.08 -0.37 (-0.66") -0.13 -0.02[Pt(thbipy)CI] " +0.36 +0.37 +0.24 -0.65 -0.88 (-0.28') 0.09 -0.42 (-1.02') -0.02 +0.18[Pt(thbipy)Cl] +0.15 +0.43 +0.34 +0.02 -0.28 (-0.01 ') 0.01 -0.41 (-0.04') -0.23 +0.14a In CD2CI, solution. In CD,SOCD, solution.' Value based upon the alternative assignments of H3 and H5 in the complexes.donors (Scheme 1). This is fully in accord with the knownability of 2-(2-thienyl)pyridine to form cyclometallatedcomplexes which exhibit the analogous C,N-bonding mode.The halide ligand in [M(thbipy)Cl] (M = Pd or Pt) isexpected to be readily displaced by other ligands, and thereaction with trimethyl phosphite in CH,CI, at room tem-perature results in the formation of orange-yellow solutions,from which orange-yellow solids may be obtained.The 'HNMR spectra of these complexes are reported in Table 3, andthe aromatic region of the spectrum of the platinum complex ispresented in Fig. 2. Each spectrum exhibits a complex aromaticregion integrating to nine protons and a doublet at w6 3.6integrating to six protons, and showing a typical 3J(P-H)coupling for a methyl group directly bonded to phosphorus ofx 12 Hz. The 31P NMR spectra of each complex show a singleresonance; in the case of the palladium complex this is observedat 6 -62 [relative to external P(OMe),], whereas for theplatinum compound it is found at 6 -85.3, and exhibitssatellites due to coupling to '"Pt['J(Pt-P) 5650 Hz].Thesedata, together with partial elemental analysis, are all in accordwith the formation of phosphonate complexes, [M(thbipy)-(P(=O)(OMe),}], in which the ligand has undergone anArbusov-type reaction where halide has attacked one of themethyl groups of the ligand with loss of chloromethane. Thecomplexes are formed in 80-90% yield. The infrared spectra ofthe complexes support the presence of this ligand, and showstrong absorptions at 1021-1016 and 1131-1 133 cm-', whichare assigned to the P-0-C and the P=O stretching modesrespectively." The FAB mass spectra (3-nitrobenzyl alcoholmatrix) of each of these complexes exhibit peaks assigned to[M(thbipy)(P(=O)(OMe),}]+ (M = Pd, m/z 453; M = Pt,m/z 541) which show the expected isotopomer distributions.The aromatic regions of the 'H NMR spectra confirm that thecyclometallated ligand persists, with the resonances assigned tothe cyclometallated thienyl ring appearing as two doublets with4.9 Hz coupling constants.The platinum complex showssatellite peaks about the resonances assigned to H6'C3J(Pt-H)23.2 Hz], H4"C3J(Pt-H) 26 Hz] and H5"C4J(Pt-H) 14 Hz]confirming the co-ordination of the terminal pyridine ring andthe terdentate mode. The chemical shifts of the methyl groupJ. CHEM. SOC. DALTON TRANS. 1992 22557.5cg8.0.a.58.7 8.5 8.3 8.1 7.9 7.7 7.5 7.3 7.16Fig. 1solution of [Pd(thbipy)Cl]Proton one-dimensional and COSY spectra of a CD,SOCD,are typical of those for phosphonates co-ordinated to platinum(trans-[PtC1{PO(OMe)2}(PBu3)2], 6 3.58, ,J(H-P) 11.8 Hz).’,We suggest that these complexes possess the structuresindicated in Scheme 1.The complexes [M(thbipy)Cl] (M = Pd or Pt) also reactsmoothly with Na[acac] in methanol to yield yellow-brownsolutions from which yellow or brown solids may be obtained.Elemental analysis indicates a formulation [M(thbipy)(acac)];the FAB mass spectrum (3-nitrobenzyl alcohol matrix) of [Pd-(thbipy)(acac)] only shows peaks assigned to [Pd(thbipy)] +,but that of the platinum compound exhibits peaks assigned to[Pt(thbipy)(acac)] +.In these complexes the acac ligand couldbe acting as a bidentate O,O’-donor, in which case the com-plexes must either be five-co-ordinate or contain a bidentatethbipy ligand, or contain a monodentate C-bonded acac with aterdentate thbipy ligand.The infrared spectra show two or threestrong absorptions in the region 1615-1680 cm-’, which arecharacteristic of the C=O stretching modes of monodentateC-bonded acac ligands. ‘ Further evidence for this bondingmode comes from the absence of absorptions in the 1600-1500cm-I region which are characteristic of bidentate O,O’-bondedacac ligands. The ‘H NMR spectra of the complexes arereported in Table 3, and confirm both the presence of acyclometallated thbipy ligand and single acac ligand perthbipy. The platinum complex shows satellite peaks about theresonances assigned to H6’C3J(Pt-H) 14 Hz], H4”C3J(Pt-H) 22Hz] and H5”C4J(Pt-H) 11 Hz], once again confirming theco-ordination of the terminal pyridine ring and the terdentatemode for the ligand.The methyl groups of the acac areequivalent, and in the platinum complex both the methylgroups C4J(Pt-H) 14 Hz] and the methine proton C2J(Pt-H)120 Hz] of the acac show satellites due to coupling to 195Pt.The large coupling to the methine carbon is only compatiblewith a monodentate C-bonded mode.’ Accordingly, thesecomplexes may be confidently assigned the structures indicatedin Scheme 1, which indicates the high stability of the terdentateN,N’,C-bonding mode for the thbipy- with the d8 centres.Upon heating a solution of [Pt(thbipy)Cl] in acetonitrilea brown solution is obtained, from which the complex[Pt(thbipy)(MeCN)][PF,] may be isolated as a brown solidupon the addition of [NH,][PF,].The ‘H NMR data for thiscompound are presented in Table 3; once again the presenceof only nine resonances and the coupling of platinum toH6’[3J(Pt-H) 12 Hz] and H4”C3J(Pt-H) 17 Hz] confirm thepresence of the terdentate N,N’,C-bonded cyclometallatedligand. The FAB mass spectrum of the complex exhibits aparent-ion peak at m/z 473 exhibiting the expected isotopicpattern. The palladium complex did not undergo an analogousreaction.We were somewhat surprised at the facile formation of thecyclometallated complexes in these systems, particularly in viewof our previous studies of 2-phenylpyridine reactions in whichit was possible to isolate intermediate non-metallated com-pounds.Accordingly, we investigated the reaction of Hthbipywith K2[PdC14] in aqueous acetonitrile at 10°C in the hopeof isolating intermediate non-metallated complexes. After stir-ring for 3 h at 10 “C an orange crystalline product had beenprecipitated. The FAB mass spectrum of this compoundexhibits peaks at m/z 343 {[Pd(thbipy)]+) and 379/381{ [Pd(thbipy)CI] ’}. Elemental analysis suggested that this com-pound was the non-metallated intermediate species, [Pd-(Hthbipy)Cl,]. We suggest that this complex contains an N,N’-bonded non-metallated bidentate Hthbipy ligand which be-haves simply as a substituted 2,2‘-bipyridine. The infraredspectrum of the complex exhibits two M-Cl stretching modes at347 and 329 cm-’ {cf: [Pd(bipy)Cl,] 353 and 343 ~ m - ’ ) .’ ~ The‘H NMR spectra of solutions of the complex in CD,SOCD, orCD,Cl, exhibit two separate sub-spectra, one of which isidentical to that of [Pd(thbipy)Cl] in the same solvent.The second sub-spectrum is assumed to be that of [Pd-(Hthbipy)Cl,], and is reported as such in Table 3. The similaritybetween the chemical shifts of the terminal pyridine ring in[Pd(Hthbipy)Cl,] (H6’, 6 9.21; H5’, 6 7.57; H4’, 6 8.12; H3’, 6 7.99)are very similar to those for [Pd(bipy)Cl,] (H6, 6 9.41; H5,6 7.65; H4’, 6 8.15; H3’, 6 8.05), providing further evidence for thepresence of an N,N’-bonded bidentate Hthbipy ligand in thiscomplex. Upon standing, solutions of [Pd(Hthbipy)Cl,] arecompletely converted into [Pd(thbipy)Cl].The non-metallatedcomplex [Pd(Hthbipy)Cl,] is converted quantitatively into[Pd(thbipy)Cl] upon warming to 40°C in dmso, aqueousacetonitrile or CH,Cl,. No such non-metallated complex couldbe isolated from reactions with platinum(I1) compounds undera wide variety of reaction conditions,In view of the ready formation of cyclometallated d8palladium(I1) and platinum(1r) complexes we have also in-vestigated the interactions of Hthbipy with gold(Ir1). We havepreviously reported the reaction of Hthbipy with Na[AuCl,]to yield the complex [Au(Hthbipy)CI,], which contains abidentate N,N’-bonded ligand.6a In this same paper we alsodescribed the thermal conversion of [Au(Hthbipy)Cl,] into[Au(thbipy)Cl,], a compound to which we assigned a cyclo-metallated structure [Fig. 3(a)] analogous to those of thepalladium(I1) and platinum(r1) complexes.We now describe ourfurther studies on this complex and correct our earlier assign-ment of structure. In related studies we have demonstrated thatHthpy cyclometallates cleanly at the 3 position upon reactionwith palladium(r1) or platinum(r1) centres, but only forms anN-bonded complex, [Au(Hthpy)Cl,], upon reaction withNa[A~cl,].~ This compound undergoes further complex re-actions under forcing conditions which include halogenationand C-C bond formation at the 5 p ~ s i t i o n . ~The complex [Au(thbipy)Cl,] is obtained in high yield (80-90%) as an orange microcrystalline solid by the direct reactio2256 J. CHEM. SOC. DALTON TRANS.1992* 0 0INCMeScheme 1 (i) [MC1412-, MeCN, H20, 60 "C (M = Pd or Pt); (ii) [MC1,I2-, MeCN, H,O, 30 "C (M = Pd); (iii) P(OMe), (M = Pd or Pt);(iu) MeCN (M = Pd or Pt); ( u ) warming; (ui) Na[AuCl,], MeCN, H,O, 45 "C; ( u i i ) MeCN, H,O, 100 "C; (uiii) MeCN, H,O, 90 "C; (ix) Nacacac],MeOH. .10.0 9:6 ' 9:2 ' 8.8 814 8:O 7:6 7:2bFig. 2 Proton NMR spectrum of a CD,Cl, solution of [Pt(thbipy)-P(=O)(OMe),)lof Hthbipy with NaCAuCl,] in boiling aqueous acetonitrile orby heating [Au(Hthbipy)Cl,] in boiling aqueous acetonitrile.The latter compound is the product of the low-temperaturereaction of NaCAuCl,] with Hthbipy. Elemental analysis is fullyin accord with the formulation [Au(thbipy)CI,], but the onlypeaks which could be assigned in the FAB or EI mass spectrawere at m/z 272/274 ([thbipy + Cl]') and 238 ([Hthbipy]');no Au-Cl stretching modes could be detected in the infraredspectrum.The complex is insoluble in water and alcohols,sparingly soluble in chlorinated solvents and readily soluble indmf or dmso.The 'H NMR and COSY spectra of a CD3SOCD3 solutionof [Au(thbipy)Cl,] are shown in Fig. 4; it is evident that onlynine proton environments are present, and that the thiophenering gives rise to an AM doublet of doublets. It was this featurewhich initially led us to propose the cyclometallatedformulation. However, there are a number of features in thisCI' %IAu'CI7(c 1Fig. 3 Possible structures for the complex [Au(thbipy)Cl,]: (a)cyclometallated, (6) a gold(1) complex of 6-(5-chloro-2-thieny1)-2,2'-bipyridine and (c) metallated at C5spectrum which are not fully consistznt with the proposedcyclometallated structure.The AM pattern assigned to the twoprotons of the metallated thiophene ring exhibit a couplingconstant of 4.0 Hz. This is indicative of a coupling between H3"and H4" rather than H4" and H5" as expected for a cyclo-metallated complex. This is suggestive of a compound which hasbeen substituted at C5" rather than C3". The 'H NMR spectraof solutions of the complex are solvent dependent, and CD2C12solutions exhibit rather different spectra (see Table 3). Anumber of interesting features emerge from a comparison of the'H NMR spectra of [Au(Hthbipy)Cl,] and [Au(thbipy)Cl,]; ifwe consider the terminal pyridine ring of the ligand, thesimilarities in chemical shifts (H6', AS -0.02; H5', A6 0.05; H4'A6 0.08; H3', A6 0.05; A6 = G[Au(Hthbipy)Cl,] - ~ [ A u J.CHEM. SOC. DALTON TRANS. 1992 2257(thbipy)Cl,]) are quite remarkable, indicating that in bothcases this ring is co-ordinated to the gold(ri1) centre. However,these correlations are not found for the central pyridine ring,and chemical shift arguments suggest that the central rings arein rather different environments in the two complexes.On the basis of these observations a number of possiblestructures may be suggested; the originally proposed structure[Fig. 3(a)] could be correct, and the coupling constant betweenH5” and H4” is abnormally low in the compound. In view of the43 6 5Fig.4solutiiu 4,315. 4”3’,4’ 3”7 .7.0‘8.0 a.9.0I 9.0 I 816 8.2 7.8 ’ 7.4 ‘ 7.0I I I I6Proton one-dimensional and COSY spectra of a CD,SOCD,I of [(Au(thbipy)Cl,),]‘normal’ coupling constants in the palladium(Ii), platinum(I1)and ruthenium(r1) cyclometallates this did not appear to belikely. Alternative formulations which maintain the stoichio-metry include a gold(i) complex of the derivatised ligand 6-(5-chloro-2-thienyl)-2,2’-bipyridine [Fig. 3(b)] or a complex whichhas been metallated at C’”. In order to maintain the four-co-ordination about the gold it is necessary for a 5”-metallatedcomplex to be oligomeric or polymeric [Fig. 3(c)].We have performed a number of experiments to investigatethese various possibilities. Reaction of [Au(thbipy)Cl,] withhydrazine under aqueous conditions results in reduction andthe deposition of gold metal as a mirror on the flask.Extraction of the aqueous suspension with dichloromethaneyields a brown solid. The EI mass spectrum and the ‘NMRspectrum of this reveals it to be predominantly Hthbipy.Thissuggests that the formulation in Fig. 3(b) is unlikely to becorrect, since hydrazine is not expected to reduce 6-(5-chloro-2-thienyl)-2,2’-bipyridine to Hthbipy under these mild condi-tions. This result is not conclusive, however, since the FABmass spectrum of [Au(thbipy)Cl,] exhibits a small butreproducible peak at m/z 272/274 assigned to 6-(5-chloro-2-thienyl)-2,2’-bipyridine!The ‘H NMR spectra of solutions of [Au(thbipy)Cl,] inCD,SOCD, (but not in CD2Cl,) change with time.Thisappears to be associated with the formation of an, as yet,unidentified solvento species. However, two features of thespectrum of this solvento species are of note; first the AMsystem of the thiophene is retained and little shifted, and,secondly, the resonance due to H6’ shifts upfield to 6 8.70, whichis exactly the position observed for the free ligand. These twoobservations suggest that it is possible to displace the terminalring from the metal at the same time as retaining an Au-Cbond. In order to resolve these problems we have deter-mined the crystal and molecular structure of the compound[Au(thbipy)Cl,].Very poor quality crystals of [Au(thbipy)Cl,] were obtainedby the diffusion of diethyl ether vapour into a solution of thecomplex in dimethylformamide.The crystal and molecularstructure is presented in Fig. 5; the compound is dimeric, ofstoichiometry [(Au(thbipy)Cl,),], with two crystallographi-cally non-equivalent gold centres. Each gold centre is four-co-ordinate in an approximately square-planar CNCI, environ-ment. At each gold centre, the two bonded chlorine ligands aremutually trans with C1-Au-C1 angles of 172.6(5) and 173.7(4)”.The gold-chlorine distances [2.255(13)-2.285( 14) A] are all inthe typical range for gold(iIi)-chlorine bonds; an analysis of the236 Au-CI distances for four-co-ordinate gold(1ir) complexes inthe Cambridge Crystallographic Data Base yielded bonddistances in the range 2.235-2.666 A, with a mean value of2.281(42) A.’ The remaining co-ordination sites of the gold areoccupied by mutually trans nitrogen and carbon donors fromtwo different thbipy ligands. The carbon donor is provided by athienyl ring metallated at the 5” position, and the gold-carbonFig.5 Crystal and molecular structure of the dimeric complex [{Au(thbipy)Cl,),] showing the numbering scheme adopte2258 J. CHEM. SOC. DALTON TRANS. 1992bond distances Au(ljC(28) 1.96(3) 8, and Au(2)-C(14)2.00(4) A are unremarkable and typical of gold(m) organometal-lic compounds; an analysis of the 96 Au-C distances for four-co-ordinate gold(II1 j a r y l complexes in the Cambridge Crystallo-graphic Data Base yielded bond distances in the range 1.871-2.733 A, with a mean value of 2.07(12) A.15 The two gold centresare approximately square planar, with the greatest deviation ofany atom from each of the square planes being 0.1 A.The co-ordination sphere about each gold is completed by the nitrogenof the terminal pyridine ring of a second ligand. Each ligandacts as a bridging C,N-donor to two gold centres; the ligandsare metallated but not cyclometallated. The central pyridinering of each ligand is non-co-ordinated. The dimeric structureis achieved by twisting about the internuclear C-C bondsbetween the pyridyl (33.4, 41.5") and the pyridyl and thienylrings (14.8,4.4").The auration of the ligand at the 5 position of the thienyl ringis somewhat unexpected in view of the palladation andplatination results discussed above, and-of our previous resultsfor ruthenation and rh~dation,~ although fully in accord withour recent studies with Hthpy which undergoes clean cyclo-palladation and cycloplatination reactions at the 3' position ofthe thienyl ring, but which gives products derived from reactionat the 5' position upon reaction with gold(111).~ The origins ofthese differences are not easily discerned.Simple argumentsbased upon size do not appear to be solely responsible as thecovalent radii for gold, palladium and platinum are similar(1.5 A), as are ionic radii for the four-co-ordinate metal ions[gold(m), 0.68; palladium(Ir), 0.64; platinum(II), 0.60 A].Similarly, charge effects cannot be solely responsible since wehave previously shown that Hthbipy cyclometallates at the 3position of the thienyl ring with rhodium(II1).The observedreactivity patterns appear to reflect a subtle balance of chargeand steric effects.We are currently further investigating the metal-iondependency of metallation reactions involving isoelectronicmetal centres.AcknowledgementsWe thank the SERC for support, Johnson Matthey for the loanof precious metals and the Royal Society and the Isaac NewtonTrust for grants towards the cost of spectrometers. 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ISSN:1477-9226
DOI:10.1039/DT9920002251
出版商:RSC
年代:1992
数据来源: RSC