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J. CHEM. SOC. DALTON TRANS. 1992 2663Synthesis of I ,I -Bis(pyrazol-1 -ylmethyl)ethene and theStructure of a Trimethylplatinum(1v) Derivative containingan Eight-membered Chelate Ring"Allan J. Canty,a R. Thomas Honeyman,e Brian W. Skeltonb and Allan H. Whiteba Chemistry Department, University of Tasmania, Hobart, Tasmania 700 I , AustraliaDepartment of Chemistry, University of Western Australia, Nedlands 6009, AustraliaThe bidentate pyrazole-donor ligand 1 , l - bis(pyrazo1-1 -ylmethyl)ethene, [ (pz)CH,],C=CH,, may besynthesized in high yield on reaction of the readily obtained potassium pyrazolide with commerciallyavailable (CICH,),C=CH,. Reaction of the ligand with [{PtMe,(SEt,)},], followed by addition ofiodomethane, gives the platinum(iv) complex fac-[PtlMe,{[(pz)CH,],C=CH,-N,N'}]. Proton NMR andX-ray structural studies show that the eight-membered chelate ring PtNNC,NN adopts a configuration inwhich the pyrazole rings are in different environments, forming angles of 26.0(3) and 38.2(3)' with the'PtC,N,' mean plane.Thus, the four methylene protons are also in different environments, as are the PtMegroups trans to pyrazole groups. The eight-membered chelate ring is fluxional, undergoing inversion withAGt z 15 kcal mol-' ( ~ 6 3 kJ mol-l) at 1 0 "C.Bis(pyrazo1- 1 -yl)alkanes, e.g. (pz),CH,, form a rich organome-tallic chemistry with platinum(I1) and platinum(Iv), includingco-ordination as N,N'-bidentate donors, and C- and N,C-cyclometallation systems involving binding of platinum at C(5)of one pyrazole ring.' We are now extending this chemistry toinclude ligands forming larger chelate rings, instead of the six-membered rings in complexes of bidentate bis(pyrazo1-1 -yl)-alkanes.As the initial part of this work we report here the synthesis of1,l-bis(pyrazo1-1-ylmethyl)ethene, [(pz)CH,],C=CH,, and theisolation and structural study of a platinum(1v) complexcontaining an eight-membered chelate ring, [PtIMe3{ [(pz)-CH2],C==CH2}].This work has coincided with the report of thesynthesis of [(~z)CH,]~C==C[CH,(~Z)],, and its application asan interesting new class of tetrapod ligand related to theporphyrin group.,ExperimentalThe reagent [{ PtMe,(SEt,)),] was prepared as described,(ClCH,),C=CH, was used as received (Aldrich), and allsolvents were dried and distilled.Proton NMR spectra wererecorded with a Bruker AM 300 spectrometer ('H chemicalshifts given in ppm relative to SiMe,) and the molecular weightof the complex was determined with a Knauer vapour-pressureosmometer for cu. (1-3) x lo-, mol dm-3 solutions at 37 "C.1,l -Bis(pyruzof- 1 -yfmethy/)ethene, [(pz)CH,],C-<H,.-Pyrazole (30 g, 441 mmol) was added to a suspension ofpotassium (17.24 g, 441 mmol) in tetrahydrofuran (400 cm3)under nitrogen, and the mixture was refluxed until thepotassium had been consumed (ca. 1.5 h). 3-Chloro-2-(chloro-methy1)prop-1-ene (27.5 g, 220 mmol) was added in one portionat ambient temperature under nitrogen, and after 30 min ofstirring the suspension was heated under reflux for 4 h.Thesolution was filtered hot, and the filtrate reduced to a minimumvolume under vacuum. Vacuum distillation gave the product as* Supplemtwtury duta avuilable: see Instructions for Authors, J. Chem.Soc., Dalton Trans., 1992, Issue I , pp. xx-xxv.N-N,p42 C=CH2 UCH2a viscous oil (33.1 g, 80%). 'H NMR (CDC1,): 6 7.55 [d, 2 H, H3,,J(H3H4) 1.6],7.35 [d, 2 H, H5, ,J(H4H5) 2.3 Hz], 6.28 ('t', 2 H,H4), 5.13 ('t', 2 H, =CH,) and 4.64 ('t', 4 H, CH,). Massspectrum: m/z 188 (M, 2), 121 (100) and 81 (52%).CPtIMe, { C(PZ)CH,I 2 M H 2 )].-A solution of[(pz)CH,],MH, (0.092 g, 0.49 mmol) and [{PtMe,-(SEt,)},] (0.15 g, 0.24 mmol) in acetone (20 cm3) wasrefluxed under nitrogen. After 15 min the yellow solution wascooled, excess of iodomethane (ca.five-fold) was added andthe solution stirred for 30 min. Excess of iodomethane wasremoved and hexane added until cloudiness developed.Microcrystals formed overnight (0.15 g, 58%) (Found: C, 27.7;H, 3.8; N, 9.4. Calc. for C,,H,,IN,Pt: C, 28.1; H, 3.8; N,10.1%). 'H NMR [(CD,),CO]: 6 8.15 (s, 1 H, H3), 7.98 (br, 2H, H5), 7.74 (br, 1 H, H3), 6.54 (br, 2 H, H4), 5.61 [d, 1 H,CH,, ,J(HH) 14.71, 5.35 (s, 2 H, =CH,), 4.84 [d, 1 H, CH,,,J(HH) 14.41, 4.71 [d, 1 H, CH,, ,J(HH) 14.73, 4.45 [d, 1 H,CH,, ,J(HH) 14.4 Hz], 1.53 and 1.49 ['td', 3 H, PtMe, transto pz, ,J(HPt) 73.61 and 1.10 rtd', 3 H, PtMe trans to I,J(HPt), 69.7 Hz]. Molecular weight in chloroform: 523 (calc.555).Crystallography.-A unique data set measured to 26,,, =55" was collected with an Enraf-Nonius CAD-4 diffractometeroperating in conventional 26-8 scan mode.A total of 3741independent reflections were obtained at ca. 295 K, 2882 withI > 30(I) being considered 'observed' and used in the full-matrix least-squares refinement after analytical absorptioncorrection and solution of the structure by vector methods.Anisotropic thermal parameters were refined for non-hydrogenatoms; (x, y , z, cTisJH were included constrained at estimate2664 J. CHEM. SOC. DALTON TRANS. 1992Fig. 1 The molecular structure of [PtIMe,{ [(pz)CH,],C=CH,}] intwo orientations to illustrate the conformation of the chelate ring, andthe geometry at platinum. Hydrogen atoms are shown with an arbitraryradius of 0.1 A, and 20% thermal ellipsoids are shown for the non-hydrogen atomsTable 1 Non-hydrogen atom coordinates for [PtIMe,([(pz)-CH2I,C=CH,IIX0.447 9 l(5)0.172 60(9)0.436(2)0.643( 1)0.651(2)0.379 6(9)0.494 3(9)0.651( 1)0.637( 1)0.465( 1)0.205 3(9)0.225( 1)0.086( 1)0.055(1)0.3 19( 1)0.229( 1)0.1 83( 2)0.201(1)- 0.024( 1)Y0.405 61(2)0.270 69(5)0.470 3(7)0.316 4(8)0.504 O(9)0.3 163(5)0.333 l(5)0.288 7(7)0.245 4(7)0.265 9(6)0.367 5(6)0.559 6(5)0.506 O ( 5 )0.533 O ( 8 )0.601 2(7)0.615 5(6)0.540 3(6)0.464 9(6)0.481 O ( 8 )L0.705 61(2)0.614 74(4)0.592 9(7)0.692 2(6)0.769 O(7)0.876 O(4)0.833 2(4)0.883 l(6)0.956 4(6)0.951 O(6)0.853 l(5)0.768 7(4)0.703 5(5)0.631 9(6)0.648 8(7)0.736 4(6)0.860 3(5)0.896 8(5)0.964 O(7)Table 2 Co-ordination and ligand geometry for [PtIMe,{ [(pz)-CH,l,C=CH,}ICo-ordination geometryPt-C(a) 2.03( 1) Pt-N(2a) 2.227(7)2.2 14( 8)Pt-C(c) 2.04( 1) Pt-I 2.803( 1)Pt-C( b) 2.04( 1) Pt-N(2b)C( a)-P t-C( b,c)C(a)-Pt-N(2a,2b)C(b)-Pt-N(2a,2b)C(c)-Pt-N(2a,2b)N( 2a)-Pt-N( 2b)I-Pt-C(a,b,c)I-Pt-N(2a,2b)Pt-N(2a)-N( la)Pt-N( 2a)-C( 3a)C(b)-Pt-C(c)Pt-N(2b)-N( 1 b)Pt-N( 2b)-C( 3b)Ligand geometryN( la)-N(2a)N( 1 a)-C(6a)C-C(6a)c-C'N( 1 a)-C(5a)N (2a)-C (3 a)C(3a)-C(4a)C(4a)-C( 5a)N(2a)-N( la)-C(6a)N(2a)-N( l a jC(5a)C( 5 a)-N ( 1 a)-C (6a)N( 1 a)-C(6a)-CC(6a)-C-C'C( 6a)-C-C(6b)N( laFN(2a jC(3a)N (2a)-C (3 a)-C( 4a)C( 3a)-C(4a)-C( 5a)N(la)-C(Sa)-C(4a)86.5(5), 85.8(4)89.6(5)173.7(4), 87.3(4)88.5(4), 173.3(3)90.3(4), 92.3(4)92.8(3), 89.6(3), 178.5(4)9 1.0(2), 88.4(2)124.4(7)13 1.0(5)124.5(7)97.9(3)13 1.9(4)1.36( 1) N( 1 b)-N(2b) 1.36(1)1.48(1) N( 1 b)-C(6b) 1.45( 1)1 SO( 1) C-C(6b) 1.50(1)1.31(2)1.35(1) N( 1 b)-C( 5b) 1.33(1)1.33(1) N(2b)-C(3 b) 1.31( 1)1.39(2) C( 3b)-C(4b) 1.3 8( 2)1.35(2) C(4b)-C( 5b) 1.35(1)122.2(6)11 1.8(7)124.5(8)1 1 1.0(6)121 3 9 )1 15.6(8)103.6( 7)1 1 1.9(9)105.3(8)107.4(9)N(2b)-N( 1 b jC(6b)N(2b)-N( 1 b)-C(5b)C(Sb)-N( 1 b)-C(6b)N( 1 b)-C(6b)-CC(6b)-C-C'N( 1 b)-N( 2b)-C( 3b)N( 2 b)-C( 3 b)-C(4 b)C( 3b)-C(4b)-C(5b)N( 1 b)-C(Sb)-C(4b)120.7(7)110.6(7)127.8(8)110.6(6)122.9(9)104.3( 8)1 12.3(9)104.6(8)108.2(9)values. Residuals R and R' on IF1 at convergence were 0.037 and0.040; statistical weights derived from u2(I> = 02(Idiff) +0.0004 u4(ldiff) were employed.Neutral atom complexscattering factors were used;4 computation used the XTAL 3.0program system implemented by S. R. Hall.' Coordinates forthe non-hydrogen atoms, and the co-ordination geometry forthe complex, are given in Tables 1 and 2, and projections of thestructure are shown in Fig. 1.Crystal data. C , 3H2 ,IN,Pt, M 555.3, monoclinic, spacegroup P2,/c (C2h5), a 7.813(4), b 13.807(3), c 16.471(6) A, p112.67(3)", U 1640 A3, D, (2 = 4) 2.25 g ~ m - ~ , F(O00) 1032.Specimen size: pale yellow plate, 0.28 x 0.18 x 0.12 mm.Monochromatic Mo-Ka radiation, h 0.7107, A, p 99.9 cm-';A*,i,,,ax 2.89, 6.22.Additional material available from the Cambridge Crystallo-graphic Data Centre comprises H-atom coordinates andthermal parameters.Results and DiscussionReaction of 3-chloro-2-(chloromethyl)prop- 1-ene with potas-sium pyrazolide in the manner reported for the synthesis of(PZ)~CH gave the required ligand in 80% yield [equation (l)].(CICH2)2C=CH2 + 2K(pz) -[(Pz)CH,]~C=CH~ + 2KC1 (1)The ligand reacts with [{PtMe,(SEt,)),] in refluxing acetone tJ.CHEM. SOC. DALTON TRANS. 1992 2665AcetoneH(6aB) Water ,I---P t M e (I)IFig. 2 Proton NMR spectrum of [PtIMe,{ [(pz)CH,],C==CH,}] in(CD,),CO, illustrating the presence of two pz environments, threePtMe environments, and four environments for the methine protons ofthe ligand. The atoms trans to the PtMe groups are indicated inparenthesesproduce a dark oil on removal of acetone which proved difficultto purify or characterize. However, the product does reactreadily with iodomethane, by an oxidative-addition reaction, toform crystalline [PtIMe,{ [(pz)CH,],C==CH,}] [equation (2)].Results of the structural determination for [PtIMe,-{[(pz)CH,],C=CH,)] are shown in Fig.1 and Tables 1 and 2.The complex has a ‘PtIC,’ geometry very similar to that ofclosely related [PtIMe,{(pz),CHMe)],’ e.g. bond lengths arewithin 30. However, the ‘PtN,’ geometry for the chelate ring isdifferent, as the N-Pt-N angle [97.9(3)”] is ca. 13” larger in thepresent complex and the Pt-N bonds [2.214(8), 2.227(7) A] areca. 0.06 8, longer. In the six-membered chelate ring of[PtJMe,((pz),CHMe}] the angles formed at the nitrogen-donor atoms are Pt-N-N 123.3(9), 122.6(8)” and Pt--N-C129.3(9), 13 1.8(9)”; these are reversed in the expanded eight-membered chelate system with the larger angles formed withinthe chelate ring [Pt-N-N 131.9(4), 131.0(5)”; Pt-N-C 124.4(7),124.5(7)”].Torsion angles outward from the platinum atom(sections a, b) for this ring are 28.4(7), 41.2(8); - 16(1), - 15(1);-82.9(9), - 88.1(10); and 71.9(9), 61.5(9)”, showing that theoverall symmetry of the molecule, disregarding the truns Me, Igroups, is quasi-2.The planar pyrazole rings form angles of 26.0(3) (ring a) and38.2(3)‘ (ring b) with the ‘PtC,N,’ mean plane, and 51.1(4)’between themselves, compared with corresponding angles of30.4(5), 31.2(5) and 57.1(6)’ for [PtIMe,{(pz),CHMe}].Thealkene group, ‘CC’C(6a),C(6b)’ is planar and forms angles of79.9(4) and 80.0(4)” with the pz rings a and b, respectively.Disorder in the structure of the cobalt(1r) complex of[(pz)CH,],C==C[CH,(pz)], prevents a detailed comparison ofligand geometry with that of the platinum(1v) complex ofThe pyrazole rings in the complex are in different environ-ments, e.g. Fig. l(b) indicates that H(3a) is ‘above’ the ‘PtC,N,’plane and H(3b) is ‘below’ this plane. Similarly, there are twoenvironments for the methylene carbon atoms, with C(6b)above and C(6a) below the plane, and thus four methyleneproton environments. The asymmetry in the structure isindicated also by the ‘H NMR spectrum of the complex in(CD,),CO, shown in Fig.2. The connectivity of the methyleneprotons is readily revealed by shift correlation spectroscopy(COSY), indicating that H(6aA) is coupled with H(6aB) andthat H(6bA) is coupled with H(6bB). The doublet furthestdownfield has been assigned to the proton adjacent to the iodineatom, and the proton furthest upfield to the proton adjacent tothe methyl group, in accord with assignments in relatedcomplexes.’.* Resonances for H(3a) and H(3b) are assignedsimilarly.Proton NMR spectra obtained in CDCl, as solvent givepoorer separation of the four methylene resonances, but allowbetter variable-temperature spectra (268-288 K) showingcoalescence of the two PtMe resonances for methyl groups transto the pyrazole donor rings. Broadening of resonances for theligand protons also occurs on warming, but resonances assignedto the PtMe group truns to iodine remain sharp.Thus, thevariable-temperature behaviour is most readily interpreted asresulting from fluxional behaviour of the chelate ring, mostlikely inversion of conformation, and the simple approach ofCramer and Mrowca’ gives AGS = 15 kcal mol-’ ( ~ 6 3 kJmol-’) at 283 K for this process (Av 6.8 Hz).[(PZ)CH,I *C==CH2*AcknowledgementsWe thank the University of Tasmania and the AustralianResearch Council for financial support, and Johnson Mattheyfor generous loans of platinum salts.References1 P. K. Byers, A. J. Canty and R. T. Honeyman, Adc. Orgunomet. Chem.,2 T. G. Traylor, P. S. Traylor and B. Y. Liu, Znorg. Chem., 1991,30,4874.3 J. Kuyper, R. van der Laan, F. Jeanneaus and K. Vrieze, Transition4 J. A. Ibers and W. C. Hamilton (Editors), International Tables for5 S. R. Hall and J. M. Stewart, The XTAL User’s Manual-Version 3.0,6 P. K. Byers, A. J. Canty and R. T. Honeyman, J. Organomet. Chem.,7 P. K. Byers, A. J. Canty, R. T. Honeyman, B. W. Skelton and A. H.8 P. K. Byers, A. J. Canty, R. T. Honeyman and A. A. Watson, J.9 R. Cramer and J. J. Mrowca, Inorg. Chim. Acta, 1971,5, 528.1992,34, in the press.Met. Chem., 1976, 1, 199.X-Ray Crystallography, Kynoch Press, Birmingham, 1974, vol. 4.Universities of Western Australia and Maryland, 1990.1990,385,4 1 7.White, J. Organomet. Chem., 1992, in the press.Organomet. Chem., 1990,385,429.Received 13th April 1992; Paper 2/01916

ISSN:1477-9226    

DOI:10.1039/DT9920002663

出版商:RSC    

年代:1992

数据来源: RSC