J. CHEM. soc DALTON TRANS. 1986 2289cis and trans Palladium(ii) and Platinum(ii) Complexes with 1,8-Bis(diphenylphosphino)-3,6-dioxaoctane and their Structural Characterizati0n.tThe First Example of an Eleven-membered Diphosphine Chelate involving cisGeometryW. Eugene Hill and John G. TaylorChemistry Department, Auburn University, Auburn, A L 36849, U.S.A.Christopher P. Falshaw and (the late) Trevor J. KingChemistry Department, University of Nottingham, Nottingham NG7 2RDBrian Beagley, David M. Tonge, Robin G. Pritchard, and Charles A. McAuliffe *Chemistry Department, University of Manchester Institute of Science and Technology, Manchester M 13 9PLMonomeric cis and trans complexes of Pt" and Pd" with 1,8-bis(diphenylphosphino)-3,6-dioxaoctane (dpdo) of general formulae [M(dpdo)X,] (M = Pd, X = CI, Br, I, or NCS; M = Pt,X = CI or I ) , in which the ligand binds only by the two phosphine donor atoms, have beensynthesized and characterized by i.r., electronic, and 31 P n.m.r. spectroscopy and molecular weightmeasurements.The isolation of these complexes illustrates that both cis and trans 11 -memberedchelate rings are obtainable under appropriate conditions; for example, both cis- and trans-monomeric [ Pt(dpdo)CI,] are reported. Syntheses of cis-palladium ( 1 1 ) complexes were carried outin polar solvents while trans isomers were prepared in less polar solvents. cis- Platinum complexeswere prepared from [PtCIJ2- while the trans isomers were prepared from Zeise's salt. Crystalstructures of cis- [ Pd(dpdo)CI,] and trans- [ Pd(dpdo) I,] are reported and discussed.A number of recent studiesip7 have shown that bidentatetertiary phosphine and arsine ligands with suitably long carbonbackbones connecting the donor atoms can form trans che-late square-planar complexes with rhodium(i), iridium([),palladium(it), and platinum(1i).Although it does appear that thepresence of bulky substituents at the donor atoms, notably t-butyl groups, seems to aid the isolation of trans ~helates,'.~we5-7 and others4 have shown that ligands with methyl orphenyl substrtuents can form this kind of trans species providedthat a suitable backbone connecting the two donor atoms existsand a kinetically labile precursor complex is used. Moreover,phosphorus or arsenic donor atoms are not necessary sincewe have recently isolated and characterized trans chelatecomplexes of the type [MLCl,] (M = Pd or Pt) and [PdLBr,],where L = 1,12-bis(phenylthio)dodecane.*I n addition, it has now become obvious that certainfacultative potentially quadridentate ligands can act asquadridentate chelating or truns-bidentate chelating agents.Thus, for example, 1,3-bis(3'-dimethylarsinopropylthio)-propane ( L ' ) forms complexes with MCl, (M = Pd or Pt)which initially exist as the As,S,-bonded five-co-ordinate[M L'ClICI complexes in dichloromethane, but rapidly cleavetwo M-S bonds to form the As2-bonded trans-bidentatechelates [M(L,')C12].6 We have extended our interest in thistype of ligand to include 1,8-bis(diphenylphosphino)-3,6-dioxaoctane. Ph,P(CH,),O(CH,),O(CH,),PPh, (dpdo),which was previously investigated by Dapporto and Sacconi.'These workers prepared diamagnetic [Ni(dpdo)I,], the X-raycrystal structure of which showed it to be a distorted planarcomplex (P-Ni--P 162.1") with a bidentate P, ligand; theN i - 0 distances are large, 3.20 and 3.16 A.A further crystalstructure of rrclns-[Rh(dpdo)(EtOH)(CO)]PF, by Alcock c'tU I . ~ . ' ~ similarly showed that the ligand can act as a trans--I Suppkiwc~nturi h r u ui~uilahk (No. SUP 56553, 8 pp.): H-atom co-ordinates, thermal parameters. See Instructions for Authors, J . Chem.Soc.., Dullon Tron.\., 1986, Issue 1 , pp. xvii-xix. Structure factors areavailable from the editorial office.bidentate diphosphine.We have prepared a series ofnickel(r1) complexes of dpdo of varied stereochemistry andreported the X-ray crystal structure of planar truns-[Ni(dpdo)(NCS),]." We here wish to report our studies ofpalladium(i1) and platinum(ii) complexes of dpdo, whichinclude the X-ray crystal structures of the monomericcomplexes cis-[Pd(dpdo)Cl,] and trans-[ Pd(dpdo)I,]. Theformer is the first example of an 11-membered chelatingbidentate ligand co-ordinating cis to a metal.ExperimentalMaterials.-Palladium(ii) chloride, potassium tetrachloro-platinate("), lithium salts, sodium iodide, and ammoniumthiocyanate were reagent grade and were used without furtherpurification. Zeise's salt, K[Pt(C,H,)Cl,], was prepared by astandard literature method; ' lithium tetrachloropalladate(i1)was prepared by stirring a 2: 1 molar ratio of LiCl and PdCl,in methanol; the ligand dpdo was prepared as previouslydescribed.'Phjisical Meusurements.-Phosphorus-3 1 n.m.r.spectra wererecorded on a Varian CFT-20 Fourier-transform n.m.r.spectrometer at 32.1 MHz. Infrared spectra were recorded on aPerkin-Elmer 580 spectrometer. Molecular weight measure-ments were determined in chloroform solution by vapour phaseosmometry.Preprution of' the Compfe.ues.- -cis-[ Pd(dpdo)CI ,I. Theligand dpdo ( 1 .OO g, 2.0 mmol), dissolved in absolute ethanol (20cm3), was mixed with a solution of lithium tetrachloro-palladate(i1) (0.52 g, 2.0 mmol) in dry methanol (20 cm3) andstirred for 20 min. The resulting mixture was filtered andanhydrous diethyl ether (200 cm3) added to the filtrate.Uponstanding for ca. 24 h the resulting pale yellow crystals werecollected by filtration and washed successively (10 cm3portions) with water (in order to remove any possible lithiumchloride remaining), cold methanol and, finally, diethyl ether2290 J. CHEM. SOC. DALTON TRANS. 1986Table 1. Summary of crystal data(u) Crystal parametersComplexMolecular formulaMCrystal systemSpace grouphlAC I Atruns-[ Pd(dpdo)12]846.74MonoclinicC30H 3 Z1 2O2 p2 Pdp2 1 In15.21 9(3)18.37 l(3)11.756(3)113.92(3)1.87 (2 = 4)3 004.51640(h) Measurement of intensities'Laboratory NottinghamDiffractometer Y 290Reflections measured hkl, hkrNo. measured 5 507Reflections used I > 30(l)No.used 400025Crystaldimensions/mm 0.3 x 0.3 x 0.2p/mm-' 2.8 1cis-[Pd(dpdo)Cl,]663.84Monoclinic'30 3 2''2O2 '2 Pdp2 1 lc11.097(6)12.380(4)2 1.456( 18)103.96(7)1.54 (2 = 4)2 860.61352UMISTCAD4hkl, hkTI > 3a(I)3 4413 081230.3 x 0.3 x 0.20.96(c) Solution of the structuresMethod Heavy atom Heavy atomMinimized function WA WAWeighting function Chebyshev scheme H' = 1.86461[02(F) + 0.00049F2]Anomalous dispersion Pd, C1, PRefined scale factor 0.322 4( 1) 1.376(2)Residual,R = ~ l A l / ~ l F , l 0.0559 0.0322' Mo-K, radiation, h = 0.710 69 I$. A = F, - F,.trans-[Pd(dpdo)X,] (X = Br, I, or NCS). A ten-molar excessof the appropriate halide or pseudohalide salt was added to asolution of Li,[PdCI,] (0.52 g, 2.0 mmol) in methanol (20 cm3)and to this, dpdo (1.00 g, 2.0 mmol), dissolved in toluene (20cm3), was added.The mixture was stirred for 30 min, filtered,and n-pentane (200 cm3) added to the filtrate. Upon standingovernight, crystals of the complexes formed. These werecollected by filtration and washed successively with 10-cm3portions of water, cold methanol, and n-pentane.cis-[Pt(dpdo)I,J*NaCI. Potassium tetrachloroplatinate(I1)(0.83 g, 2.0 mmol), the dpdo (1 .OO g, 2.0 mmol), and a ten-molarexcess of NaI were stirred in acetone (50 cm3) for 12 h. Thesolution was filtered and n-pentane (250 cm3) added to thefiltrate. After standing overnight, the pale orange-yellowcomplex was collected by filtration and washed successivelywith 10-cm3 portions of water, ethanol, and n-pentane.cis-[Pt(dpdo)Cl,]. The ligand (1.00 g, 2.0 mmol) andK,[PtCI,J (0.83 g, 2.0 mmol) were refluxed with stirring inabsolute ethanol (30 cm3) for 12 h.The solvent was thenremoved in uucuo and the residue treated with CH,CI, (10 cm3)and filtered to remove KCI. n-Pentane (50 cm3) was added tothc filtrate followed by refrigeration overnight. The whitecomplex was collected by filtration, washed successively with10-cm3 portions of water, ethanol, and n-pentane and dried inuacuo.trans-[Pt(dpdo)CI,]. A solution of dpdo (0.50 g, 1.0 mmol) inacetone (30 cm3) was added dropwise to a stirred solution ofK[Pt(C,H,)CI,] (0.30 g, 1.0 mmol) in acetone (100 cm3) andfiltered. n-Pentane (300 cm3) was added to the filtrate resultingin the precipitation of a pale yellow complex.The precipitatewas collected and washed successively with 10-cm3 portions ofwater, ethanol and, finally, n-pentane.trans-[Pt(dpdo)I,]-KCI. A ten-fold excess of NaI was addedto a solution of K[Pt(C,H,)Cl,] (0.18 g, 0.5 mmol) in acetone(100 cm3). The mixture was stirred at room temperature for 0.5h. The ligand (0.24 g, 0.50 mmol), dissolved in acetone (30 cm3),was added dropwise over 0.5 h. After stirring for a further 0.5 h,the solution was filtered and the volume reduced to ca. 20 cm3 inuacuo. Approximately 100 cm3 of n-pentane was added and theresulting mixture was left standing overnight in a refrigerator.Orange crystals were collected by filtration, washed successivelywith 10-cm3 portions of water, ethanol, and n-pentane and driedin a vacuum desiccator.trans-[ Pt(dpdo)(NCS),] was prepared similarly usingammonium thiocyanate instead of NaI for the metathesisreaction.Collection and Reduction of X-Ray Data.-Light browncrystals of trans-[Pd(dpdo)I, J were obtained by dissolving thecomplex in methanol-toluene (1 : l), diluting with a five-foldexcess of n-pentane, and cooling.Single-crystal X-raydiffraction data were collected on a Hilger and Watts four-circlediffractometer. The positions of the palladium, iodine, andphosphorus atoms were obtained by using the direct methodsSHELX l 3 program. The remaining portion of the structure wassolved using Fourier methods and the CRYSTALS programat the University of Nottingham.The trial structure was refinedusing first isotropic and then anisotropic thermal parameters.After several cycles of such refinement the majority of thehydrogen atoms were located in a Fourier difference map.Hydrogen atoms were then included in their calculatedpositions, then further refinement, excluding the hydrogenatoms, gave a final R value of 0.0559.Pale yellow crystals of cis-[Pd(dpdo)CI, J were obtained byrecrystallization from methanol-chloroform (1 : 1) diluted with afive-fold excess of n-pentane. Approximate unit-cell parametersobtained photographically were refined after measurement ofselected reflections by computer control on the CAD 4diffractometer. Consideration of systematic absences establishedthe space group, and, after collection of the intensity data,subsequent calculations were carried out on the jointCDC7600/ICL 1906 computer system at the University ofManchester Regional Computing Centre.The phase problemwas solved by the heavy-atom method and the structure wasrefined using SHELX.I3Other details of the collection and reduction of the data forboth complexes appear in Table 1.Results and DiscussionPreparation of the Complexes.-The complexes isolated arelisted in Table 2, and full preparative details are given in theExperimental section. Here we give brief details and items ofspecial interest.The complex cis-[Pt(dpdo)CI,] was prepared by treatingK,[PtCI,] with dpdo in absolute ethanol or K,[PtCI,] withdpdo in acetone.The corresponding iodides and thiocyanateswere prepared by addition of a ten-fold excess of sodium iodideor sodium thiocyanate respectively.The trans-[Pt(dpdo)X,] (X = CI or I) species were isolatedfrom the reaction of Zeise's salt, K[Pt(C,H,)CI,], with dpdo(X = C1 or I) in the presence of a large excess of sodium iodide(X = I). An acetone solution of the ligand was added to Zeise'ssalt dissolved in a large volume of acetone in order to minimizethe formation of oligomeric species. Isomerization to the cisisomer was avoided by keeping Zeise's salt in excess of thJ. CHEM. SOC. DALTON TRANS. 1986 229 1Table 2. Elemental analyses and molecular weight data for the complexesAnalysis " (%)IComplex Colourcis-[ Pd(dpdo)Cl ,] Yellowrrans-[ Pd(dpdo)Br,] Yellow1r0ns-c Pd(dpdo)I,] Browntrans-[ Pd(dpdo)(NCS) 23 Orangecis-[ Pt(dpdo)Cl,] Whitetrans-[ Pt(dpdo)C123 Pale yellowcis-[ Pt(dpdo)I ,]*NaCl Orange-yellowvans-[ Pt(dpdo)I,]-KCl OrangeC53.0 (54.2)48.1 (47.9)42.3 (42.5)54.3 (54.2)47.8 (47.9)47.6 (47.9)36.7 (36.2)35.6 (35.6)H4.8 (4.9)3.7 (3.8)4.5 (4.3)4.7 (4.5)4.3 (4.3)4.2 (4.3)3.4 (3.2)3.1 (3.2)- M b.r X10.5 (10.7) 680 (663)20.9 (21.3) 734 (752)29.0 (30.0)3.7 (4.0)' 715 (708)9.7 (9.4) 743 (752)9.4 (9.4) 770 (752)342 (935")" Calculated values in parentheses.Determined in CHCl, solution. ' Calculated molecular weight for monomers in parentheses. Contains oneN-bonded and one S-bonded thiocyanato group. ' X = N. I For cis-[Pt(dpdo)I,] the calculated value of M would be 935.Table 3."P N.m.r. and electronic spectra of dpdo and the palladium(u) complexesSolid SolutiondApproximate reflectance electronicCompound ' P/p.p.m." A,/p.p.m.' %' 10 3v,a,/cm ' 10 3~max/cm ' &/dm3 mol ' cm '+21.8- 32.0 - 53.8 100 25.5 29.4 Shoulderdpdorruns-[Pd(dpdo)Br,] - 14.5 - 36.3 100c~.Y-[ Pd(dpd0)ClJrrans-[ Pd( dpdo)I,] - 6.5 - 28.3 100 20.9 30.6 9 515rrans-[ Pd(dpdo)(NCS),] - 13.8 - 35.6 44' 21.1 1 940- 14.8 36.6 34- 11.7 - 33.5 15- 16.2 - 38.0 6" Relative to 8%" H,PO, (downfield negative). * Co-ordination chemical shift (A,) = chemical shift of ligand - chemical shift of complex. ' Basedon 31P-{ 'H) n.m.r. spectra. dChloroform solvent. Mixture of N,N-, N,S-, and S,S-bonded isomers.Table 4.3 1 P N.m.r. and electronic spectra of the platinum(i1) complexesSolid SolutionApproximate reflectance electronicComplex 'P/p.p.m." 'J(Pt-P)/Hz % b 10-3v,ax~/cm-' 1 0 3 ~ m a x /cm-' 4dm3 mol cm 'ci.~-[ Pt( dpd0)C12] - 10.4 3 719 100 29.3t r ~ n . ~ - [ Pt (dpdo)Cl,] - 14.8 2 660 59 31.4 36.9 8 460- 8.6 2 560 31 23.0- 9.2 2 567 6-4.1 3 632 4- 7.3 3 481 86 23.6 + 0.2 2 420 8- 5.5 2 506 6+ 0.9 2411 41 20.0- 5.4 2 506 14 + 0.3 2 420 12- 7.3 3 482 12-3.1 3 632 5" Relative to 85",, H,PO, (downfield negative). Based on "P-{ 'Hf n.m.r. spectra. Chloroform solvent.ci.~-[ Pt( dpdo)I,]*NaCl[~uH.Y-[ Pt(dpd~)I,].KCl27.730.23 120Shoulderphosphine during the reaction, which was carried out at roomtemperature. Excess phosphine or elevated temperatures havebeen shown to cause trans-cis isomerization in complexes of thetype truns-[Pt(PR,),X,] (R = alkyl or aryl, X = anionicligand)." Our method is a modified version of that used toprepare complexes of the type ~rans-[Pt(PR,),Cl,] (R = Ph orBu').'' Elemental analyses of the cis and trans iodo complexesindicate that, in the solid state, one molecule of salt (NaCI orKCl) is associated with the complex. Molecular weight data forcis-[ Pt(dpdo)IJNaCI are in agreement with the presence ofNa+, C1-, and [Pt(dpdojI,] in solution, the observed value(342) being extremely close to that calculated from anequimolar mixture of these species (333).The complex cis-[ Pd(dpdo)CI,] was prepared from thereaction of Li,[PdCI,] in methanol with dpdo in ethanol; andthe other palladium(i1) derivatives from [PdX,]' - dissolved inmethanol and dpdo dissolved in toluene.For the majority of complexes it was possible to obtainmolecular weight data in chloroform; all those examined weremonomeric (Table 2).31P N.M.R.of the Complexes.-The 31P n.m.r. spectra ofall the palladium complexes (Table 3) consist of a single peak,except the spectrum of the thiocyanate derivative which consistsof two strong, equally intense lines at - 13.8 and - 14.8 p.p.m.as well as two relatively weak lines at - 16.2 and - 11.7 p.p.m.The major lines are assigned to the N,S-bonded isomer. The twominor components are assigned to the linkage isomers, N,N at- 16.2 p.p.m. and S,S at - 11.7 p.p.m.It is expected that theN,N-bonded isomer would be shifted to lower field relative tothe N,S-isomer, due to the higher electronegativity of thenitrogen. It should be noted that, upon standing in CDCI,solution, the resonance at - 16.2 p.p.m. ascribed to the N,N-bonded isomer grew at the expense of the - 13.8 p.p.m. an2292 J. CHEM. SOC. DALTON TRANS. 1986Table 5. Infrared data (cm I ) for the complexesComplex v(C0C) v(M-X)~ v(M-P) v(CN)dpdo 1 110 (sh)c~is-[Pd(dpdo)CI,] 1 093s 2923151 063stt+f~~.~-[Pd(dpdo)I,] 1 098 (sh) hI070w(NCS)( SCN )I I070wtran.S-[Pd(dpdo)- c 280wcis-[ Pt(dpdo)CI,] 1 096s 299m1 0 6 0 ~ 325m~r~n.v-[Pt(dpdo)Cl,l 1 0 9 5 (sh) 338s3483 74hh 2 090s350w375w362w2 104 (sh)' X = C1, I, or S. Not observed.Obscured by other bands.Table 6. Fractional co-ordinates for trans-[Pd(dpdo)I,], with estimatedstandard deviations in parenthesesXIU0.328 64(5)0.434 7(2)0.527 4(7)0.573( 1)0.560 l(9)0.604 O(9)0.562 l(9)0.464 7(7)0.407 4(9)0.305 O(8)0.260 2(2)0.296 03(6)0.768 lO(5)0.291 4(7)0.380 O(8)0.409( 1 )0.349( 1 )0.259( 1 )0.229( 1)0.131 2(7)0.088 l(9)- 0.01 3 O(9)- 0.067 6( 8)- 0.026( 1 )0.073 l(9)0.384 4(7)0.32 I ( 1)0.285( 1)0.309( I )0.373( 1)0.410( 1)0.507 O(7)0.554 7(9)0.61 5 7(9)0.629 2(8)0.579 9(8)0.519 2(7)Ylb0.3 19 72( 3)0.251 5(1)0.208 8 ( 5 )0.258 8(7)0.326 9(5)0.379 8(8)0.450 3(8)0.448 9(6)0.500 1(6)0.491 l(5)0.397 5( 1 )0.201 93(3)0.093 04( 3)0.376 2(5)0.348 5(6)0.336 6(7)0.355 O(7)0.381 2(8)0.392 4(8)0.407 9( 5)0.475 6(7)0.480 3(8)0.420 2(8)0.356 l(8)0.349 6(6)0.I77 9(5)0.196 7(7)0.145 5 ( 8 )0.074 l(8)0.055 9(8)0.105 4(6)0.298 7(5)0.259 6(6)0.293 2(7)0.368 2(7)0.407 6(6)0.372 9( 5)Zjc0.162 70(6)0. I08 2( 2)0.245 7(9)0.354( 1)0.328( I )0.423( 1)0.372( 1)0.358( I )0.292( 1 )0.268 l(8)0.259 6(2)0.265 02( 7)0.468 34(6)0.424 9(8)0.493 8(9)0.620( 1 )0.678( 1)0.606( 1 )0.479( 1)0. I92 3(9)0.190( 1 )0.143( 2)0.099( 1 )0.101 (2)0.149(1)- 0.002( 1 )-0.120(1)-0.214(1)-0.187(2)- 0.072( 2)0.024( 1 )0.039 8(9)- 0.020( 1 )- 0.062( 1 )-0.050( 1)0.003( 1)0.05 1 ( 1 )- 14.8 p.p.m. resonances of the N,S-isomer, suggestingisomerization of the mixed complex to the N,N-bonded species.Such isomerization has been previously noted," and isconsistent with our observations of the i.r.spectrum of achloroform solution of this complex (see below).The 31P n.m.r. spectra of cis-[Pt(dpdo)X,] (X = C1 or I )(Table 4) exhibit the expected 1 :4: 1 pattern centred at - 10.4p.p.m. ['J(Pt-P) = 3 7191 and -7.3 p.p.m. ['J(Pt-P) = 3 481Hz], respectively. The coupling constants are typical of cis-[ Pt( PR3),X2] complexes. '' The co-ordination chemical shiftsof - 32.2 p.p.m. for the chloride and - 29.1 p.p.m. for the iodideTable 7. Distances (A), angles ( ), and torsion angles ( ) in /rum-[Pd(dpdo)I,], with estimated standard deviations in parentheses(i) Around Pd(1) atomPd( 1)-P(2) 2.330(2) P(2)-Pd(l)-P(11) 164.9(1)Pd(1)-P(1I) 2.321(2) I( 12)-Pd( 1 )-I( 13) I46.8( 1 )Pd( 1 )-I( 1 2) 2.620( 1 ) P( 2)-Pd( I )-I( 12)P(2)-Pd( ])-I( 13)Sum of last four 368.687.9( 1 )97.2( 1 )Pd( ])-I( 13) 2.636( 1) P( 1 1 )-Pd( I )-I( I 3) 89.1 ( 1 )P( 1 1 )-Pd( I )-I( 12) 94.4( I )( i i ) Around P(2) atomP(2)-Pd( 1) 2.330(2) Pd( 1 )-P(2)-C(3) 1 10.9( 3)P@)-C( 3) 1.84(1) Pd(l)-P(2)-C(26) 117.3(3)P(2)-C(32) 1.83(1) C( 3)-P(2)-C( 26) 105.3( 5)C( 3)-P(2)-C( 32) 101.9(4)P( 2)-C( 26) 1.81(1) Pd( I)-P(2)-C(32) 118.4(3)C(26)-P(2)-C(32) 101.2(4)(iii) Phenyl groupsAv. C-C Av.C-CC ( 2 6 3 1 ) 1.375(8) C(32-37) 1.388(7)C(14-19) 1.380(7) C(2&-25) 1.370(8)(ir) I 1 -Membered ringRing torsionangle2.330(2) 43( I )1.84(1) -47(1)1.50(2) - 16(1)1.29(2) - 177(1)1.42(2) - 170(1)1.46( 2) 69( 1 )1.30(2) 173(1)1.42(2) -167(1)1.48(2) -30(1)1.84(1) -38(1)2.321(2) 59(1)1 10.9( 3)1 14.7( 7)1 15.0( 1 1 )120.0( 1 1 )107.1( 10)107.0( 12)118.2( 13)115.9( 1 1 )I 17.0(7)1 1 1.9( 3)164.9( I )are in accordance with the lower electronegativity of the iodideligands.The chemical shift difference between the twocomplexes (+ 3.1 p.p.m.) compares favourably with thatobserved for cis-[Pt(PBu",),X,] of +2.6 p.p.m. from X = CIto X = I. Two minor components are observed in the spectrumof the cis-iodide complex at - 5.5 p.p,m. [ ' J ( Pt-P) = 2 5061and +0.2 p.p.m. ['J(Pt-P) = 2 420 Hz]. These componentshave coupling constants typical of truns-Pt( PR3), complexes.The spectra of truns-[Pt(dpdo)X,] (X = CI or Br) are muchmore complex even though molecular weight measurementsare consistent with a monomeric formulation in chloroform.In CDCI, truns-[Pt(dpdo)CI,] exhibits three resonancessuggestive of trans species, uiz.at - 14.8 ['J(Pt-P) = 2 6601,- 8.6 [ 'J(Pt-P) = 2 5601, and - 9.2 p.p.m. [ 'J(Pt-P) = 2 567Hz]; in addition, a very small amount of cis species is present, asevidenced by a resonance at -4.1 p.p.m. ['J(Pt-P) = 3 632Hz]. The existence of more than one species in solutions of trans-bonded phosphine chelates has been previously observed and itwas suggested by Shaw and co-workers ' that this arises fromthe presence of different stable conformers. In view of ourmolecular weight data, it seems that the n.m.r.data also point tothe presence of different stable conformers in these complexes.However, the minor cis component is not a cis monomer, sinceits chemical shift and coupling constants differ from that of themonomeric cis complex detailed above.The spectrum of rruns-[Pt(dpdo)I,] also consists of threJ. CHEM. soc. DALTON TRANS. 1986 2293C(Figure 1. Molecular structure of rrans-[Pd(dpdo)I,] showing the atom- Figure 2. Molecular structure of ris-[Pd(dpdo)CI,] showing thenumbering scheme atom-numbering scheme-conformers at +0.3 and - 5.4 p.p.m. are the minor componentsTable 8. Final fractional co-ordinates for cis-[Pd(dpdo)CI,], with observed in the spectrum cis-[Pt(dpdo)l,]. Two minor cisestimated standard deviations in parentheses species at -7.3 ['J(Pt-P) = 3 4821, and -3.1 p.p.m.X / a0.132 34(3)0.209 4( 1 )0.149 l(4)0.1344(5)0.244 9(3)0.235 l(6)0.348 4(6)0.369 l(3)0.276 O ( 5 )0.308 2(5)0.299 6( I )0.056 l ( 1 )0.022 5( 1 )0.281 7(4)0.347 8(6)0.338 3(7)0.262 8(7)0.197 8( 6)0.206 8(5)0.455 9(4)0.556 3(4)0.671 5 ( 5 )0.689 l(5)0.588 9( 5)0.472 l(5)0.152 4(4)0.152 6(5)0.1 12 6(5)0.069 7(6)0.067 2(6)0.109 7(6)0.373 l(4)0.450 O(4)0.571 8(5)0.614 6(5)0.538 3 6 )0.41 7 7(5)Ylb0.330 37(3)0.373 8( 1)0.504 3(4)0.587 8(4)0.592 7(3)0.657 l(5)0.639 6(5)0.530 4(3)0.487 2(4)0.371 4(4)0.282 7( 1)0.371 7( 1 )0.298 3( 1 )0.148 O(4)0.120 5( 5)0.017 l(6)- 0.056 2( 5)-0.031 l(5)0.072 O( 5)0.270 4(4)0.327 6(4)0.311 l(5)0.238 5 ( 5 )0.181 7(5)0.197 3(4)0.274 8(4)0.167 5(4)0.090 3( 5 )0.120 9(6)0.226 7(6)0.304 O( 5)0.386 8(4)0.446 1(4)0.466 9(4)0.431 2(5)0.373 7(6)0.349 9( 5)z/c0.318 43(2)0.233 2( 1)0.I98 8(2)0.246 5(2)0.295 l(2)0.347 4(3)0.400 l(3)0.420 9(2)0.448 2(3)0.465 8(2)0.397 3( 1)0.247 O( 1)0.396 2( 1)0.428 2(2)0.488 7(3)0.51 1 4(3)0.474 4(3)0.414 9(3)0.391 O(3)0.385 5(2)0.419 3(2)0.408 O(3)0.363 l(3)0.328 2(5)0.339 3(3)0.171 O(2)0.187 O(3)0.140 8(3)0.078 5(3)0.062 3(3)0.107 5(2)0.234 O(2)0.281 2(3)0.278 4(3)0.228 l(3)0.179 4(3)0.182 7(3)['J(Pt-P) = 3 632 Hz] are observed in the spectrum of trans-[Pt(dpdo)I,], one of which is readily assignable to the cismonomer, since its coupling constant and chemical shift areidentical to that observed for the monomer.Z.r.Spectra of the Cornpie-yes. The i.r. spectra of thecomplexes, Table 5, support the conclusions drawn from the31P n.m.r. studies. The spectrum of cis-[Pd(dpdo)Cl,] in thesolid state shows two bands at 292 and 315 cm-', assignable tov(Pd-CI) of cis geometry." Similarly, two bands at 299 and325 cm-' are observed for cis-[Pt(dpdo)Cl,]. We are alsoable to assign v(M-P) bands for these two complexes at 348and 374 cm-' (M = Pd) and 350 and 375 cm-' (M = Pt) inagreement with other reported values." As expected, weobserve only one v(Pt-CI) band at 338 cm-I for trans-[Pt(dpdo)Cl,], in close agreement with other complexes of thetype trans- [ Pt( PR 3) ,C1 J.' 'The i.r. spectrum of trans-[Pd(dpdo)(NCS)(SCN)] exhibits astrong v(CN) stretch at 2 090 cm-' with a pronounced shoulderat 2 104 cm-'. Ligand absorptions obscured the v(CS) andG(NCS) regions, making these assignments impossible. Theobserved v(CN) values are in the generally accepted range for acomplex which contains Pd-NCS (2 090 cm-') and Pd-SCN(2 104 cm-') linkages,,' and we also detected the N,S-bondedspecies links in solution oia 31P n.m.r. (see above). Palladium(rr)complexes containing both N - and S-bonded thiocyanategroups are well known.,' Additional evidence for a mixed-linkage complex comes from the presence of a weak band at 280cm-', assignable to v(Pd-S)."The v(C0C) absorptions for the free ligand occur at I 110and 1 063 cm-'.It is well established that co-ordination of theether function affects these absorptions a great deal, shiftingthem to significantly lower energy.23 However, these ligandabsorptions occur at essentially the same energies in thecomplexes (Table 5) and are strong evidence for the absence ofM - 0 bonds.trans components, presumably different conformers, centred at Electronic Spectra of the CompIeses.-The solid reflectance+0.9 ['J(Pt-P) = 2 41 13, - 5.4 ['J(Pt-P) = 2 5061, and +0.3 and solution electronic spectra of the complexes are listed inP.p.m. ['J(Pt-P) = 2420 HzJ. Interestingly, the trans Tables 3 and 4. In general, a high-energy visible band i2294 J.CHEM. SOC. DALTON TRANS. 1986Table 9. Distances (A), angles ("), and torsion angles (") in cis-[Pd(dpdo)Cl,], with estimated standard deviations in parentheses( i ) Around Pd(1) atomPd( 1 j P ( 2 ) 2.263( 1 )Pd( 1 )-P( 1 1 )Pd( 1 )-C1( 12)2.268( 1 )2.332( 1)Pd( 1 )-C1( 13) 2.326( 1)( i i ) Around P(2) atomP(2bPd( I ) 2.263( 1)P(2 j C ( 3 ) 1.834(5)P(2)-C(26) 1.809(5)P(ZkC(32) 1.820(5)( i i i ) Around P( 1 1 ) atomP( 1 1 kPd( 1) 2.268( 1)P(I I)-C(iO) 1.819(5)P(11)-C(14) 1.822(5)P( 11)-C(20) 1.819(5)( i c ) Phenyl groupsav. C-CC( 26-3 1 ) 1.367( 3)C( 14-19) 1.369(3)(c) 1 1-Membered ring2.263( 1 )1.834( 5)1.49 1 (7)1.406( 6)1.403( 7)1.490( 8)1.423 7)1.409( 6)I . 504( 8)I .819(5)2.268( 1 )P(2)-Pd( 1 )-P( 1 1)C1( 12)-Pd( 1 )-C( 1 3)P(2)-Pd( 1 )-CI( 12)P( 1 1 )-Pd( 1 )-Cl( 13)SumPd(1 FP(2)-C(3)Pd( 1 )-P(2)-C(26)Pd( ljP(2)-C(32)C (3 )- P( 2)-C (2 6)C( 3 )- P(2 bC(3 2 1C(26tP(2)-C(32)Pd(1)-P(l1)-C(l0)Pd( 1 )-P( 1 1 jC(20)Pd(1 )-P(ll)-C(l4)C( 10)-P( 1 1)-C( 14)C( lO)-P( I 1 )-C(20)C( 14)-P( 1 1 )-C(20)Ring torsionangle- 131(1)37( 1)50( 1)- 171(1)169( 1)- 58( 1)-63(1)179(1)-68(1)-39(1)121( 1 )C(32-37)C( 20-2 5)( r i ) Phenyl-phenyl interaction *C(32) * * C(20) 3.47C(33) * * * C(21) 3.26C(34) * - C(22) 3.35(rii) Interplanar anglesC( 32-37)-C(2&25) 17( 1 )C(32-37)-C(26-31) 101 (1 )105.4( 1)88.1( I )8 2 3 1)84.0( 1 )360.0I 1 1.2(2)107.6( 2)125.7(2)105.8(2)101.1(2)103.8(2)108.6(2)I 1 1.6(2)123.6( 2)104.4( 2)107.3(2)99.5(2)av.C-C1.378(3)1.376(3)1 1 1.2(2)I15.1(3)108.6(4)1 13.3(4)l08.1(5)1 14.8( 5)114.2(4)108.2(4)1 14.2(4)C( 10)-P( 1 1 )-Pd( 1 ) 108.6(2)P(l IkPd(l)-P(2) 105.4(1)C(35) - * C(23) 3.70C(36) * * C(24) 3.90C(37) * * C(25) 3.78C(2O-25 j C ( 14-49) 88(1)C(26-31)- C(14-19) 19(1)* C(32).distance above PPdP plane = 0.22; C(25),distance below PPdPplane = 0.17 A.observed and, in addition, a weakly defined shoulder is seen insome cases in the solid state. These spectra are consistent withplanar d* species,24 although it is not possible to distinguish cis-and tr~ns-isomers.~~Molt.cdur Structures of trans-[ Pd(dpdo)I ,] and cis-[Pd(dpdo)CI,].-Tables 6 and 7 present the atomic co-ordinates, bond distances, bond angles, and ring torsion anglesfor trans-[Pd(dpdo)I,].Tables 8 and 9 contain the corres-ponding information for cis-[ Pd(dpdo)CI,]. The molecularstructure of the iodide is shown in Figure 1 and that of thechloride in Figure 2.The co-ordination at palladium is trans for [Pd(dpdo)I,] butthere is a small deviation from square-planar geometry (seeTable 7). The 11-membered ring and, indeed, the wholemolecule has an approximate two-fold axis passing through thePd atom and the midpoint of C(6 jC(7). The bond anglesI-Pd-I and P-Pd-P are slightly larger than those of theanalogous complex [Ni(dpdo)I,],' as expected due to the largermetal-ion radius of Pd. The Pd-P bond lengths are not unusualfor trans palladium(I1) phosphine complexes.26 However, incontrast to [Ni(dpdo)I,], where more than one conformer ofthe chelate backbone was observed, only one conformationexists for [Pd(dpdo)I,] and the 0-CH,-CH,-0 torsion angleof 69" supports the earlier prediction for [Ni(dpdo)I,] thatstaggered conformations would be the most stable.In cis-[Pd(dpdo)CI,] the P-Pd-P and Cl-Pd-CI bond anglesand bond lengths are very similar to those observed for cis-[Pd(PPr,),C1,].27 In the latter complex the deviation of theP-Pd-P angle from 90" was ascribed to steric effects, which mayalso be present in the chelate.A highlight of the intramolecularpacking for the chelate is the juxtapositioning of the two phenylrings C(32-37) and C(2&25) (see Figure 2).These rings arenot exactly superimposed and are inclined 17" from beingparallel, but corresponding C C distances between the ringsare all less than 4 A, Table 9. Interaction between the x systemsis suggested, and this is supported by the longer C-C distanceswithin these two henyl rings (1.376, 1.378 A), compared with1.367 and 1.369 1 for the other two phenyl rings, which aredistant from each other. The 11-membered chelate ring isasymmetrical, as its ring torsion angles show (Table 9); pseudo-mirror symmetry is destroyed in the C(6)-C(7) region, althoughelsewhere a pseudo-mirror plane containing the Pd atom andbisecting C(6)-C(7) approximately relates the remaining ringatoms.A unique feature of this study is the isolation of square-planarpalladium(i1) complexes which contain either a cis or trans11-membered chelate ring.Such a phenomenon has not beenpreviously observed.AcknowledgementsWe are grateful to the S.E.R.C. for support and to AuburnUniversity for the Award of a Teaching Assistantship (toJ. G. T.).ReferencesI A. Pryde, B. L. Shaw, and B. Weeks, J. Chem. Soc., Dalton Trans.,2 N. J. DeStefano, D. K. Johnson, and L. M. Venanzi, Angen,. 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