Synthesis and Characterization of Ambient Temperature Stable

Department of Chemistry, University of Western Australia, Nedlands, W.A. 6009, Australia. Received July 14, 1994®. The palladium(II) complexes ...
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Organometallics 1995,14, 199-206

Synthesis and Characterization of Ambient Temperature Stable Organopalladium(IV)Complexes, Including Aryl-, ql-Allyl-,Ethylpalladium(IV),and Pallada(IV)cyclopentane Complexes. Structures of the Poly(pyrazo1-l-y1)borateComplexes PdMe3{(pz)sBH} and PdMe3{(pz)rB} and Three Polymorphs of PdMezEti (pz)3BHI Allan J. Canty,*’?Hong Jin,? Andrew S. Roberts,? Brian W. Skelton,t Peter R. Traill,? and Allan H. White$ Department of Chemistry, University of Tasmania, Hobart, Tasmania 7001, Australia, and Department of Chemistry, University of Western Australia, Nedlands, W.A.6009, Australia Received July 14, 1994@ The palladium(I1) complexes PdMeZ(tmeda1, PdMePh(tmeda), and Pd(CH2CHzCHzCHz)(tmeda) (tmeda = tetramethylethylenediamine)react with potassium tris(pyrazo1-l-y1)borate and organohalides RX in acetone to form the octahedral palladium(IV) complexes PdMeRR”-

,

{(pz)sBH}(R = Me, Ph) and Pd(CH2CHzCHzCH~)R{(pz)3BH} (RX = MeI, EtI, PhCHzBr, CHz=CHCH&. The complexes are stable in the solid state and in solution at ambient temperature, PdMe3{(pz)3BH}is more stable than the iodide salt of isoelectronic [PdMes{(pz)aCH}]+, and the aryl- and 17l-propenylpalladium(IV)complexes are the first examples of aryland allylpalladium(IV) complexes that are stable above 0 “C. The tris(pyrazo1-l-y1)borate ligand considerably enhances the stability of palladium(IV)complexes when compared with related neutral donor ligands. The ethylpalladium(rV) complexes have stabilities in solution similar to that of the most stable ethylpalladium(I1)complexes reported. The complex PdMea{ ( ~ Z ) ~(2) B }has been prepared, and structural studies of this complex and PdMe~R{(pz)3BH} [ R= Me (l),E t (3>]completed, allowing the first comparison of structural parameters of ethylpalladium(11, IV) complexes and of PdMe3{ (pz)3BH} with the “isoelectronic”cation [PdMe3{(pz)3CH}]+. Three polymorphs of PdMezEt{(pz)3BH} were examined: complex 3a is ordered, but the other polymorphs exhibit disordering in the conformation of the ethyl group (3b) and in the position of the ethyl group and one of the methyl groups (3c). Crystallographic data: for 1, monoclinic, space group P21/c, a = 16.559(16) b = 7.859(4) c = 13.774(15)A, p = 118.88(8)”,2 = 4, R = 0.032, R, = 0,043; for 2, monoclinic, space group P21/c, a = 11.453(1) b = 9.729(2) A, c = 16.973(9) p = 107.25(3)”,2 = 4, R = 0.053, R, = 0.055; for 3a, monoclinic, P2&, a = 9.384(3) A, b = 12.795(3) A, c = 15.119(8) A, p = 115.22(3)”,2 = 4, R = 0.055, R, = 0.052; for 3b,orthorhombic, P212121, a = 13.955(3) A, b = 13.152(18) A, c = 9.047(6) A, 2 = 4, R = 0.052, R, = 0.053; for 3c,tetragonal, P43212, a = 12.305(4) c = 21.542(7) 2 = 8, R = R, = 0.035.

A,

A,

A,

A,

A,

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Introduction Synthetic, structural, and mechanistic aspects of organopalladium(IV)chemistry have developed rapidly since the initial report of the first hydrocarbyl complex T

University of Tasmania.

* University of Western Australia.

Abstract published in Advance ACS Abstracts, November 1,1994. ( l ) ( a )Byers, P. K.; Canty, A. J . ; Skelton, B. W.; White, A. H. J. Chem. Soc., Chem. Commun. 1986,1722. (b) Canty, A. J.Acc. Chem. Res. 1992,25,83,and references therein. (c) Canty, A. J.; Traill, P. R.; Skelton, B. W.; White, A. H. J.Organomet. Chem. 1992,433,213. (d) Byers, P.K; Canty, A. J . ; Honeyman, R. T.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 1992,433,223.(e) Byers, P.K.; Canty, A. J.; Skelton, B. W.; Traill,P. R.; Watson, A. A.; White, A. H. Organometallics 1992, 11, 3085. (0 Canty, A. J . Platinum Met. Rev. 1993, 37,2. (g) Bennett, M. A.; Canty, A. J . ; Felixberger, J. K.; Rendina, L. M.; Sunderland, C.; Willis, A. C. Inorg. Chem. 1993,32, 1951. (h) Canty, A. J . ; Traill, P. R.; Colton, R.; Thomas, I. M. Znorg. Chim. Acta 1993,210,91.(i)Markies, B. A.; Canty, A. J.; Boersma, J.;van Koten, G. Organometallics 1994,13,2053.(i)Ducker-Benfer, C.; van Eldik, R.; Canty, A. J . Organometallics 1994,13,2412.

in 1986, PdIMedbpy) (bpy = 2,2’-bip~ridyl).l-~All complexes isolated to date contain bidentate or tripodal donor ligands, although evidence has been presented in support of the proposal that PdBrzH(Cy)(PPh& is present as one component in a solid obtained on heating PdBrz(PPh3)~in cyclohexane.5 Most of the complexes isolated have low stability, decomposing at or below

@

(2)(a)de Graaf, W.; Boersma, J.; Smeets, W. J. J.; Spek, A. L.; van Koten, G. Organometallics 1989,8,2907. (b) de Graaf, W.; Boersma, J . ; van Koten, G. Organometallics 1990,9, 1479. (c) Asters, P. L.; Engel, P. F.; Hogerheide, M. P.; Copijn, M.; Spek, A. L.; van Koten, G. Organometallics 1993,12,1831. (3)(a) Catellani, M.;Chiusoli, G. P. Gam. Chim. Ital. 1993,123,1. (b) Bocelli, G.; Catellani, M.; Ghelli, S. J. Organomet. Chem. 1993,458, ~

n, 0

bL&.

(4)van Asselt, R.; Runberg, E.; Elsevier, C. J . Organometallics 1994, 13,706. (5)Vedernikov, A. N.;Kuramshin, A. I.; Solomonov, B. N. J. Chem. SOC.,Chem. Commun. 1994,121. (6)Klaui, W.; Glaum, M.; Wagner, T.; Bennett, M. A. J. Organomet. Chem. 1994,472,355.

0276-733319512314-0199$09.0010 0 1995 American Chemical Society

Canty et al.

200 Organometallics, Vol. 14, No. 1, 1995

ambient temperature, facilitating kinetic studies of their decomposition that have revealed insights into C-C bond formation mechanisms of direct interest to potential roles for palladium(IV) in organic synthesis.lb Kinetic studies of the decomposition of PdIMedbpy) in acetone, including a volume profile for the reaction, indicate that the major pathway for reductive elimination of ethane and formation of PdIMe(bpy)proceeds via iodide dissociation (eq 1, R = Me) and that the inter-

-

PdIMe,R(bpy) == [PdMe,R(bpy)(acetonel+IPdIR(bpy) Me-Me (1)

+

mediate cation probably contains probably contains coordinated acetone [PdMe3(bpy)(acetone)l+.ljr7 For nitrogen donor tripod ligands coordinated to trimethylpalladium(IV), [P~M~~(Ls-N,W,”)~+X-, the stability of the complexes increases with increasing basicity of the ligands; e.g., complexes of bis(1-methylimidazol-2-yl)(pyridin-2-yl)methaneare more stable than those of tris(pyrazol-l-yl)methane.8~9 In an attempt to gain further insight into these effects on stability, and to search for complexes that are stable a t ambient temperature, we have investigated the synthesis and properties of palladium(IV) tris(pyrazo11-y1)boratecomplexes, because poly(pyrazo1-1-yllborates are more basic than poly(pyrazo1-1-yllalkanesand the anticipated complexes “PdR3{(pz)3BH-iV,iV’,”)” are isoelectronic with [P~R~((~Z)~CH-N,W,”)I+. We have found that the [(pz)~BHl-ligand has a remarkable ability to stabilize the higher oxidation state for palladium, allowing the isolation of a range of ambient temperature stable palladium(IV) complexes. These include pallada(n7)cyclopentane complexes, complexes containing +allyl and ethyl groups where the ethylpalladium(IV) complexes have stabilities comparable to the most stable ethylpalladium(I1) complexes reported to data, and the first ambient temperature stable arylpalladium(IV) complexes and palladium(IV) complexes containing three different hydrocarbyl groups. Preliminary reports of parts of this work have appeared.lOJ1

Experimental Section The reagents PdMez(tmedaP and PdMePh(tmeda)12and the pallada(I1)cyclopentane complex Pd(C4H8)(tmeda)13were prepared as described. Solvents were dried and distilled, and all syntheses were carried out under nitrogen. Microanalyses were by the Central Science Laboratory, University of Tasmania, and NMR spectra were recorded with a Bruker AM 300 spectrometer, with chemical shifts given in ppm relative to Mersi. Synthesis of Complexes. PdMes{(pz)sBH} (1). A solution of PdMez(tmeda) (0.03 g, 0.12 mmol) and K[(pz)3BHl(O.O3 g, 0.12 mmol) in acetone (10 mL) was stirred at 0 “C for 1h. (7) Byers, P. K.; Canty, A. J.; Crespo, M.; Puddephatt, R. J.; Scott, J. D. Organometallics 1988,7, 1363. ( 8 ) Byers, P. K.; Canty, A. J.; Skelton, B. W.; White, A. H. Organometallics 1990,9, 826. (9)Brown, D. G.; Byers, P. K.; Canty, A.J. Organometallics 1990, 9, 1231. (10)Canty, A. J.; Traill, P. R. J. Organomet. Chem. 1992,435,C8. (11)Canty, A. J.; Honey”, R. T.; Colton, R.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 1994,471,C8. (12)Markies, B. A.; Canty, A. J.;de Grad, W.; Boersma, J.; Janssen, M. D.; Hogerheide, M. P.; Smeets, W. J. J.; Spek, A. L.; van Koten, G. J. Organomet. Chem., in press. (13)(a) Diversi, P.;Ingrosso, G.;Lucherini, A.; Murtas, S. J. Chem. SOC.,Dalton Trans. 1980,1633. (b) Diversi, P.;Ingrosso,G.; Lucherini, A.Inorg. Synth. 1983,22,167. (c) Canty, A. J.; Skelton, B. W.; Traill, P. R.; White, A. H. Aust. J. Chem. 1994,47, 2119.

Iodomethane (0.017 g, 0.12 mmol) was added, the solution was stirred for 3 h at ambient temperature, and after centrifugation to precipitate a fine powder, the yellow solution was collected and evaporated to dryness under vacuum at 0 “C. The residue was extracted with diethyl ether, filtered, and evaporated to dryness. The solid obtained was recrystallized from diethyl ethedpetroleum (bp 40-60 “C) to give a white crystalline product (0.037 g, 86%): ‘H NMR (CDC13) 6 7.64 (d, 3, H3 or 5), 7.54 (d, 3, H3 or 5), 6.20 (“t”,3, H4), 1.38 (s, 9, PdMe); 13C{lH}NMR (CDCl3) 6 138.3(H3 or 51, 135.4 (C3 or 5), 105.5 (C4), 12.9 (PdMe). Anal. Calcd for CIZHISBN~P~: C, 39.5; H, 5.2; N, 23.0. Found: C, 39.8; H, 5.2; N, 23.0. PdMes{(pz)rB} (2). A solution of PdMez(tmeda1 (0.036 g, 0.14 mmol) and K[(pz)4B] (0.045 g, 0.14 mmol) in acetone (10 mL) was stirred at 40 “C for 1 h, and on lowering the temperature to ambient, iodomethane (0.02 g, 0.14 mmol) was added. The solution was stirred overnight, the solvent removed and the residue extracted with diethyl ether t o give an orange solid. The solid was extracted with petroleum ether (2 x 5 mL, bp 40-60 “C) and evaporated t o give the product as a whie solid (61%): lH NMR (CDCl3) 6 8.03 (d, 35= 2.4 Hz, 1, H3 or 5 of uncoordinated pz), 7.96 (d(b), 1,H3 or 5 of uncoordinated pz), 7.66 (d, 35= 2.4 Hz, H3 or 51, 7.61 (d(b), 3, H3 or 5), 6.61 (“t”(b),1,H4 of uncoordinatd pz), 6.21 (“t”(b),3, H4), 1.42 (s,6, PdMe); l3C{lH) NMR (CDC13) 6 142 (C3 or 5 of uncoordinated pz), 139.2 (C3 or 5), 136.8 (C3 or 5 of uncoordinated pz), 133.3 (C3 or 5), 107.4 (C4 of uncoordinated pz), 105.9 (C4), 13.2 (PdMe). Anal. Calcd for CISHZ~BN&’~: C, 41.8; H, 4.9; N, 26.0. Found: C, 42.4; H, 5.1; N, 25.9. The following complexes were obtained by a procedure mostly similar to that for complex 1. PdMeJ3t{ (pz)sBH} (3):iodoethane as reagent, crystallization from pentane, yield 80%; lH NMR (CDC13)6 7.70 (d(b), 2, H3 or 5 trans t o Me), 7.66 (d(b), 1,H3 or 5 trans to Et), 7.63 (d(b), 2, H3 or 5 trans t o Me), 7.54 (d(b), 1, H3 or 5 trans to Et), 6.23 (“t”,2, H4 trans to Me), 6.19 (“t”, 1,H4 trans to Et), ~ ) , (9, 6, PdMe), 1.09 (t, 2.42 (9, = 7.6 Hz, 2, P ~ C H Z C H 1.42 35= 7.6 Hz, 3, PdCHzCH3); 13C{’H} NMR (CDC13)6 138.6 (C3 or 5), 138.3 (C3 or 5), 135.5 (C3 or 51, 135.1 (C3 or 51, 105.5 (C4), 105.3 (C4), 28.9 ( P ~ C H Z C H17.9 ~ ) , (PdMe), 15.6 (PdCHzCH3). Anal. Calcd for C13H21BNsPd: C, 41.3; H, 5.6; N, 22.2. Found: C, 41.5; H, 5.9; N, 21.9. PdMez(CH#h)((pz)sBH} (4): benzyl bromide as reagent, crystallization from petroleum ether, yield 55%; ‘H NMR (CDCl3) 6 9.80 (d, 35= 2.3 Hz, 2, H3 or 51, 9.77 (d, 35= 2.0 Hz, 1,H3 or 5 trans to CHZPh), 9.66 (d, = 2.0 Hz, 1, H3 or 5 trans to CHZPh), 9.22 (m, 3, Ph(3-511, 9.16 (m, 4, H3 or 5 trans t o Me and Ph(2,6)),8.33 (“t”,1, H4 trans to CHzPh), 8.24 (“t”,2, H4 trans to Me), 3.54 ( 8 , 2, PdCHZ), 1.55 (s, 6, PdMe); 13C{lH}NMR 6 146.7, 138.4, 135.4, 135.2, 130.1, 125.6, 105.5 (C4), 105.1 (C4), 36.1 (PdCHz), 18.5 (PdMe). Anal. Calcd for ClsHzsBNsPd: C, 49.1; H, 5.3; N, 19.1. Found: C, 49.0; H, 5.5; N, 19.1. PdMez(CH&H=CHz){ (pz)sBH} (5). A procedure similar to that for 1was followed except that oxidative addition with 2-propenyl iodide was carried out at -5 “C, and the complex was obtained by crystallization from petroleum ether, yield 71%: lH NMR ((CD3)&O) 6 7.96 (d, 3J = 2.1 Hz, H3 or 5 trans t o Me), 7.93 (d, 3J = 2.1 Hz, 1,H3 or 5 trans to allyl), 7.90 (d, 35= 2.1 Hz, 2, H3 or 5 trans t o Me), 7.80 (d, 3J = 2.1 Hz, 1, H3 or 5 trans t o allyl), 6.24 (“t”,2, H4 trans to Me), 6.39 (‘‘t”, 1,H4 trans to allyl), 6.09 (m, PdCHZCHCHz), 5.34 (m, PdCHzCHCHH trans to CH), 5.15 (dd, 2J = 9.9 Hz, 35= 1.2 Hz, 1, PdCHzCHCHH cis to CH), 3.20 (d, 35= 9 Hz, PdCHz), 1.61 (s, 6, PdMe); l3C(lH} NMR 6 144.3, 143.7, 139.5 (C3 or 51, 139.3 (C3 or 51, 136.5 (C3 or 51, 136.3 (C3 or 51, 113.3 (PdCHzCHCHz), 106.3 (C4), 106.1 (C4), 34.6 (PdCHZ), 18.2 (PdMe). Anal. Calcd for C14HzlBNsPd: C, 43.1; H, 5.4; N, 21.5. Found: C, 43.3; H, 5.6; N, 21.5. PdMezPh{ (pz)sBH} (6). A solution of PdMePh(tmeda) (0.030 g, 0.095 mmol) and K[(pz)3BHI in acetone (5 mL) was stirred at 35 “C for 4 h. The solution was cooled to ambient temperature, iodomethane (50 pL) added, the solution stirred

Organometallics, Vol. 14, No. 1, 1995 201

Organopalladium(N) Complexes

Table 1. Specific Crystallographic Details complex

formula

:p3 b (A)

c (A) B (deg) V (A) z

mol wt (g

crystalsize(”) P (cm-9 F(OCQ)

2&, (de@ A*,”,,, N

NO R RW

PdMed(pz)sBHI (1) CizH19BNd‘d P21/~(NO. 14) 16.559(16) 7.859(4) 13.774(15) 118.88(8) 1570(3) 4 364.5 1.54 0.22 x 0.40 x 0.50 10.7 736 55 1.21, 1.38 3593 3086 0.032 0.043

PdMed(pz)4BI (2) Ci5HziBNsPd P21/~(NO. 14) 11.453(1) 9.729(2) 16.973(9) 107.25(3) 1806(1) 4 430.6 1.58 0.08 x 0.18 x 0.20 8.9 872 55 1.07, 1.17 4149 2683 0.053 0.055

PdMeBt{(pz)sBHI (3a) Ci3HziBN6Pd P21/~(NO. 14) 9.384(3) 12.795(3) 15.119(8) 115.22(3) 1642(1) 4 378.6 1.53 0.12 x 0.24 x 0.04 11.3 768 50 1.05, 1.14 2873 1518 0.055 0.052

for 2 min, and water (2 mL) added. The solvents were removed to give a white solid which was dissolved in ethanol (4 mL) and filtered, and water (4 mL) was added to precipitate a white solid. Ethanol was removed by rotary evaporation, and the resulting suspension was centrifuged to precipitate the product, which was washed with water, recentrifuged, collected, and dried under vacuum (0.029 g, 71%): ‘H NMR (CDCl3) 6 7.70 (m, 3H, H3 or 5 ) , 7.62 (b, 1, H3 or H5), 7.24 (b, 2, H3 or 5), 7.03 and 6.96 (m(b), 5 , Ph), 6.25 (“t”, 1, H4), 6.15 (“t”, 2, H4), 1.82 (2, 6, PdMe); l3C{lH) NMR 6 140.0, 138.7, 136.9, 135.6,135.2,128.0 (Ph), 124.7 (Ph), 105.9 ((241,105.7 (C4), 19.1 (PdMe). Anal. Calcd for C1&1BN6Pd: C, 47.9; H, 5.0; N, 19.7. Found: C, 47.8; H, 4.9; N, 19.6. PdMeEtPh{(pz)sBH} (7). A procedure similar to that for 6 was followed, except that reaction with iodoethane was carried out at 55 “C, water was added at 45 “C until cloudiness occurred, and then iodomethane (100 pL) was added to convert any unreacted PdMePh(tmeda) to insoluble PdIPh(tmeda). Volatiles were removed on a vacuum line to give a white solid suspended in water. The product was extracted into diethyl ether, the diethyl ether layer was evaporated to dryness, the solid obtained was dissolved in acetone, and a solid precipitated with addition of water. Acetone was removed by rotary evaporation and the resulting suspension centrifuged to precipitate the product (84%): lH NMR (CDC13) 6 7.72 (m, 3, H3 or 5), 7.66 (d, 3J= 2.2 Hz 1, H3 or 51, 7.31 (d(b), 1, H3 or 5 ) , 7.17 (d(b), 1, H3 or 5 ) , 7.00 (m(b),5 , Ph), 6.27 (“t”, 1,H4), 6.19 (“t”,1, H4), 6.12 (“t”,1, H4), 2.83 (m, 2, P ~ C H Z C H 1.81 ~), ( s , 3, PdMe), 0.99 (t, 3J= 7.5 Hz, 3, PdCHzCH3); l3C{lH) NMR: 6 140.7, 140.1, 139.1, 136.5, 135.7, 135.3, 134.9, 127.9 (Ph), 124.7 (Ph), 105.7 (C4), 105.5 (C4), 35.8 (PdCHzCH3),21.7 (PdMe). Anal. Calcd for Cl&3BN6Pd: C, 49.1; H, 5.3; N, 19.1. Found: C, 49.2; H, 5.4; N, 18.3. PdMe(CHzPh)Ph{(pz)sBH} (8). A procedure similar to that for 6 was followed using benzyl bromide (95%): lH NMR (CDC13) 6 7.66 (d, 3J= 2.4 Hz, 1, H3 or 51, 7.64 (d, 3J= 2.2 Hz, 1, H3 or 5 ), 7.63 (d, 35= 2.2 Hz, 1, H3 or 51, 7.08 (d, 3J= 2.0 Hz, 1,H3 or 51, 7.04 (m, 5 , PdPh), 6.99 (‘8, 1, PdCHSh), 6.86 (“t”, 2, PdCHSh), 6.78 (‘d‘,2, PdCHSh), 6.56 (d, 3J= 1.9 Hz, 1, H3 or 5), 6.09 (“t”,1,H4), 6.07 (“t”, 1, H4), 6.01 (“t”,l, H4), 3.99 (d, 25= 8.2 Hz, 1, PdCHH), 3.89 (d, 2J= 8.2 Hz, PdCHH), 1.97 (s,3, PdMe); l3C{lH} NMR 6 146.1,140.3,138.8, 136.5, 135.6, 135.2, 135.0, 130.4, 128.6, 128.0, 126.0, 124.9, 105.6 (C4), 105.5 (C4), 105.3 ((241, 43.1 (PdCHzPh), 24.1 (PdMe). Anal. Calcd for Cz3HzaBNsPd: C, 54.9; H, 5.0; N, 16.7. Found: C, 54.8; H, 4.9; N, 16.3. PdMe(CH&H=CH2)Ph{ (pz)sBH} (9). A procedure similar to that for 6 was followed, except that the oxidative addition reaction with 2-propenyl iodide was carried out at 0 “C, and workup of the solid used acetonelwater (88%): lH NMR (CDC13) 6 7.73 (d, 3J = 2.2 Hz,1, H3 or 51, 7.69 (m, 2, H3 or 5 ) , 7.64 (d, 35= 2.2 Hz,1, H3 or 5 ) , 7.32 (b, 1,H3 or 51, 7.12 (d, 3J= 1.8 Hz, 1,H3 or 5 ) , 7.02 (m, Ph), 6.95 (m, Ph), 6.24

PdMezEt{(pz)sBH}(3b)

PdMeaEt{(pzhBHI ( 3 4

Ci3HziBN6Pd E212121 (NO. 19) 13.955(3) 13.152(18) 9.047(6)

Ci3HziBN6Pd P43212 (NO.96) 12.305(4)

1660(3) 4 378.6 1.51 0.06 x 0.75 x 0.55 11.2 768 55 1.07, 1.48 2166 1470 0.052 0.053

3262(2) 8 378.6 1.54 0.47 x 0.32 x 0.28 11.4 1536 50 1.25, 1.40 1723 1283 0.035 0.035

21.542(7)

(“t”, 1, H4), 6.18 (“t”, 1, H4), 6.11 (“t”,1, H4), 5.91 (m, 1, PdCHZCHCHz), 5.21 (d(b), 1, PdCHzCHCHH trans to CH), 5.02 (dd, 3J = 9.9 Hz, = 2.3 Hz, PdCHzCHCHH cis to CH), 3.51 (“t”,1, PdCHZ), 3.31 (“t”, 1, PdCHZ), 1.88 (s, PdMe); l3C{lH) NMR 6 143.4, 140.5, 140.2, 139.4, 136.4, 135.8, 135.4, 135.1, 128.0 (Ph), 124.8 (Ph), 114.7 (PdCHzCHCHz), 105.7 (C4), 39.3 (PdCHZ), 24.4 (PdMe). Anal. Calcd for C19H~3BNad:C, 50.4; H, 5.1; N, 18.6. Found: C, 50.4; H, 5.0; N, 18.5. Pd(C&)Me{ (pz)*H} (10). A solution of Pd(C&)(tmeda) (0.06 g, 0.24 mmol) and K[(pz)3BHl (0.06 g, 0.24 mmol) in acetone (15 mL) was stirred at 0 “C for 2 h. Iodomethane (0.015 mL, 0.24 mmol) was added, and the solution was allowed to warm to ambient temperature and stirred for 4 h. On evaporation of solvent, the residue was extracted with diethyl ether and filtered to remove a yellow solid. The solution was evaporated to -2 mL and cooled to -20 “C to give the product as a cream-colored solid (0.084 g, 90%): ‘H NMR (CDCl3) 6 7.78 (d, 3J= 1.8 Hz, 1,H3 or 5 trans t o Me), 7.64 (d, 35= 2.0 Hz, 3, H3 or 9,7.44 (d, 3J= 2.0 Hz,2, H3 or 5), 6.20 (“t”,3J= 3 Hz, 1, H4 trans t o Me), 6.17 (“t”, 3J = 3 Hz, 2, H4), 3.16 (m, 2, PdCHH), 2.87 (m, 2, P d O , 1.78 (m, 4, CH2), 1.44 (8, 3, PdMe); l3C{lH) NMR 6 138.9 (C3 or 5 ) , 135.3 (C3 or 51, 105.3 (C4), 45.6 (PdCHZ), 34.9 (CHz), 16.1 (PdMe). Anal. Calcd for C ~ J I Z I B N ~ C, P ~43.0; : H, 5.4; N, 21.5. Found: C, 43.0; H, 5.2; N, 20.5. The following complexes were obtained by a procedure mostly similar to that for complex 10. Pd(C&)Et{ (pz)sBH} (11): iodoethane as reagent, crystallization from pentane, yield 70%; ‘H NMR (CDCl3) 6 7.75 (d, 3 5 = 1.8Hz, 1, H3 or 5 trans to Et), 7.67 (d, 35= 1.8Hz, 2, H3 or 5), 7.60 (d, 3J= 1.8 Hz, 1,H3 or 5 or trans to Et), 7.51 (d, 3J = 1.8 Hz, 2, H3 or 5), 6.18 (“t”, 2, H4), 6.16 (“t”, 1, H4 trans to Et), 3.20 (m, 2, PdCHH), 2.75 (m, 2, PdCHH), 2.40 (9, 3J = 7.5 Hz, 2, P ~ C H Z C H 1.79 ~ ) , (m, 4, CHd, 0.93 (t, 35= 7.5 Hz, 3, PdCHzCHs); l3C{lH) NMR: 6 139.6 (C3 or 51,139.0 (C3 or 51, 135.5 (C3 or 51, 135.1 (C3 or 9,105.2 (C4),47.6 (PdCH2CHz), 34.8 (PdCHZCHz), 30.4 (PdCHzCH3), 18.6 (PdCHzCH3). Anal. Calcd for C16H23BN6Pd: C, 44.5; H, 5.7; N, 20.8. Found: C, 44.6; H, 5.9; N, 20.5. Pd(C&)(CHzPh){(pz)&?H} (12): benzyl bromide as reagent, crystallization from pentane, yield 67%; lH NMR (CDC13)6 7.77 (d, 3J= 2.0 Hz, 1, H3 or 5 , pz trans to CHZPh), 7.60 (d, 35= 2.2 Hz, 2, H3 or 51, 7.58 (d, 35= 2.0 Hz, 1,H3 or 5 trans t o CHZPh), 7.0-6.83 (m, 8, Ph and H3 or 51, 6.15 (“t”, 1, H4 trans to CHZPh), 6.01 (“t”,3J= 3.0 Hz, 2, H4), 3.58 ( 8 , 2, PdCH2Ph), 3.56 (m, 2, PdCHH), 2.85 (m, 2, PdCHH), 1.93 (m, 4, CHz); l3C{lH) NMR: 6 146.9, 135.2, 139.0, 135.2, 129.9 (Ph), 128.4 (Ph), 125.3 (Ph), 105.2 ((241, 105.0 (C4), 49.6 (PdCHZ), 39.0 (PdCHZPh), 34.7 (CHz). Anal. Calcd for CZOHz6BN6Pd: C, 51.5; H, 5.4; N, 18.0. Found: C, 51.5;H, 5.5; N, 17.9. Pd(C&)(CHzCH=CHd{ (pz)sBH} (13): oxidative addition of 2-propenyl iodide at -5 “C, crystallization from pentane,

202 Organometallics, Vol. 14, No. 1, 1995

Canty et al.

Table 2. Non-Hydrogen Atom Coordinates and Equivalent Isotropic Displacement Parameters for PdMe3{(pz)JBH} (1) atom

X

Y

Z

Ueq(A2)

Pd C(a) C(b) C(c) B N(a1) N(a2) C(a3) C(a4) C(a5) N(b1) N(b2) C(b3) C(b4) C(b5) N(c1) N(c2) C(c3) C(c4) C(c5)

0.16618(2) 0.0834(3) 0.0746(3) 0.0874(3) 0.3882(3) 0.3501(2) 0.2580(2) 0.2472(3) 0.3309(3) 0.3956(3) 0.3580(2) 0.2672(2) 0.2648(3) 0.3519(3) 0.4102(3) 0.3470(2) 0.2544(2) 0.2409(3) 0.3235(4) 0.3899(3)

0.22089(4) 0.3159(6) 0.3166(7) 0.0083(6) 0.2404(5) 0.1460(3) 0.1205(4) 0.0353(5) 0.0062(6) 0.0786(5) 0.1436(4) 0.1196(3) 0.0314(5) -0.0023(5) 0.0706(5) 0.4212(4) 0.4450(4) 0.6122(5) 0.6975(5) 0.5739(5)

0.21 123(2) 0.0570(3) 0.2555(4) 0.1626(3) 0.3505(3) 0.4183(2) 0.3754(2) 0.4522(3) 0.5447(3) 0.5208(3) 0.2415(2) 0.1681(2) 0.0848(3) 0.1016(3) 0.2024(3) 0.3243(2) 0.2670(3) 0.2597(4) 0.3122(4) 0.3530(3)

0.0409(1) 0.064(2) 0.079(3) 0.064(2) 0.041(2) 0.039(1) 0.045(1) 0.054(2) 0.060(2) 0.049(2) 0.039(1) 0.042(1) 0.054(2) 0.059(2) 0.050(2) 0.043(1) 0.049(1) 0.065(2) 0.069(3) 0.053(2)

Table 4. Non-Hydrogen Atom Coordinates and Equivalent Isotropic Displacement Parameters for PdMe$t{ (pz)JBH} (3a) X

0.8140(1) 0.843(1) 1.014(1) 0.959(2) 0.88 l(3) 0.495(2) 0.630(1) 0.777(1) 0.866(1) 0.774(2) 0.626(2) 0.468(1) 0.585(1) 0.522(2) 0.365(2) 0.333(1) 0.541(1) 0.671(1) 0.678(2) 0.554(2) 0.470( 1)

Table 3. Non-Hydrogen Atom Coordinates and Equivalent Isotropic Displacement Parameters for PdMe3{ (PZ)~} (2) 0.31895(5) 0.3872(8) 0.1957(8) 0.4363(8) 0.2658(7) 0.2349(5) 0.2493(5) 0.2137(7) 0.1768(7) 0.1912(6) 0.4014(5) 0.4462(5) 0.5610(7) 0.5935(7) 0.4900(7) 0.1885(5) 0.1964(5) 0.1270(6) 0.0740(7) 0.1 144(6) 0.2416(5) 0.1249(6) 0.1297(9) 0.2448(9) 0.3118(7)

0.44420(5) 0.2580(8) 0.3423(9) 0.4372(9) 0.6968(7) 0.7355(5) 0.647 l(6) 0.7 130(8) 0.8432(8) 0.8554(7) 0.6544(5) 0.5558(6) 0.5357(8) 0.6143(8) 0.6866(7) 0.5720(5) 0.4553(6) 0.3610(7) 0.4 163(7) 0.5468(8) 0.8222(6) 0.8501(7) 0.9793(8) 1.0364(8) 0.9354(8)

0.67790(3) 0.6625(5) 0.7206(5) 0.7944(4) 0.5469(4) 0.6276(3) 0.6906(3) 0.7480(4) 0.7228(4) 0.6465(4) 0.5682(3) 0.6283(3) 0.6313(4) 0.5726(5) 0.5329(4) 0.5067(3) 0.5520(3) 0.5032(4) 0.4255(4) 0.4299(4) 0.4916(3) 0.4429(3) 0.4184(5) 0.4517(5) 0.4989(4)

0.0388(2) 0.064(3) 0.060(3) 0.063(3) 0.032(3) 0.033(2) 0.040(2) 0.045(3) 0.051(3) 0.043(3) 0.033(2) 0.041(2) 0.045(3) 0.051(3) 0.040(3) 0.032(2) 0.037(2) 0.041(3) 0.048(3) 0.041(2) 0.036(2) 0.055(3) 0.064(4) 0.061(4) 0.047(3)

yield 76%; lH NMR (CDC13) 6 7.78 (d, 35= 2.0 Hz, 1, H3 or 5 trans t o allyl), 7.68 (d, 35= 2.0 Hz, 2, H3 or 5), 7.62 (d, 35= 2.0 Hz, 1,H3 or 5 trans to allyl), 7.52 (d, 3J= 2.0 Hz, 2, H3 or 5), 6.18 (m, 3, H4), 5.86 (m, 1, PdCHzCHCHz), 5.23 (dd, 35= 17 Hz, = 2.5 Hz, 1,PdCHzCHCHH trans to CHI, 4.96 (dd, 3J = 9.8 Hz, 25= 2.5 Hz, 1, PdCHzCHCHH cis to CH), 3.32 (m, 2, PdCHH), 3.07 (d, 35= 9 Hz, 2, PdCHZCHCHz), 2.76 (m, 2, PdCHH), 1.86 (m, 4, CHz); l3C{lH) NMR 6 144.4, 139.8, 139.0, 135.5, 135.3, 112.6 (PdCHZCHCHz), 105.3 (C4), 105.2 (C4), 50.2 (PdCHZCHz),37.7 (PdCHzCHCHz), 34.7 (CH2). Anal. Calcd for C16H23BNePd: C, 46.1; H, 5.6; N, 20.2. Found: C, 46.4; H, 5.7; N, 18.9. X-ray Structure Determinations. For each complex, a unique data set was measured at 295 K using an Enraf-Nonius CAD-4 diffractometer operating in conventional 26-6 scan mode with monochromatic Mo K a radiation (2 = 0.710 73 A), yielding N independent reflections, No,with Z > 3dn considered observed and used in the full matrix least-squares refinement after Gaussian absorption correction and solution (14)Ibers, J. A., Hamilton, W. C., Eds. International Tables for X-Ray Crystallography; Kynoch Press: Birmingham, England, 1974; VOl. 4. (15) Hall, S. R.;Stewart, J. M. The XTAL User's Manual, Version 3.0; Universities of Western Australia and Maryland, 1990.

Y 0.65674(7) 0.5207(9) 0.621(1) 0.728(1) 0.783(2) 0.744(1) 0.8228(6) 0.8002(6) 0.881(1) 0.9566(9) 0.9176(9) 0.7213(6) 0.6862(7) 0.668(1) 0.6917(9) 0.7248(8) 0.6396(6) 0.5862(6) 0.4986(9) 0.4937(9) 0.5827(9)

Z

Ueq(A2)

0.26100(7) 0.2025(9) 0.3804(9) 0.208(1) 0.116(1) 0.264(1) 0.3110(6) 0.3228(6) 0.3703(9) 0.3877(9) 0.3501(8) 0.1591(7) 0.1393(6) 0.0436(9) -0.0006(8) 0.0761(9) 0.3208(6) 0.3274(6) 0.3753(8) 0.4018(9) 0.3654(8)

0.0521(4) 0.078(7) 0.090(7) 0.11(1) 0.19(2) 0.060(7) 0.049(4) 0.052(4) 0.071(6) 0.080(8) 0.063(6) 0.049(4) 0.060(5) 0.070(6) 0.072(7) 0.058(5) 0.049(4) 0.046(4) 0.067(7) 0.076(7) 0.062(6)

Table 5. Non-Hydrogen Atom Coordinates and Equivalent Isotropic Displacement Parameters for PdMe$t{ (pz)JBH) (3b) atom

X

V

Z

U."(A2)

0.54445(7) 0.456(1) 0.614(1) 0.645(2) 0.686(3) 0.620(5) 0.469(1) 0.5753(6) 0.6257(6) 0.7154(8) 0.729(1) 0.639(1) 0.4429(7) 0.4747(6) 0.4479(9) 0.404(1) 0.4034(9) 0.4192(7) 0.4391(8) 0.392(1) 0.339(1) 0.361(1)

0.84129(6) 0.866(1) 0.973(1) 0.776(2) 0.690(3) 0.684(6) 0.768(1) 0.7842(6) 0.8223(7) 0.8276(9) 0.799( 1) 0.7724(8) 0.6892(5) 0.7009(6) 0.6176(8) 0.5512(8) 0.5987(9) 0.8719(7) 0.9145(7) 1.OO21(9) 1.015(1) 0.931(1)

0.52319(9) 0.7 12(1) 0.579(2) 0.656(2) 0.594(5) 0.723(9) 0.204( 1) 0.197(1) 0.3 169(9) 0.278( 1) 0.135(2) 0.085(1) 0.322(1) 0.459(1) 0.533(1) 0.439(2) 0.305(2) 0.249(1) 0.383(1) 0.381(2) 0.255(2) 0.166(2)

0.0678(3) 0.132(8) 0.113(6) 0.145(9) 0.14(1) 0.33(4) 0.067(5) 0.057(3) 0.060(3) 0.072(5) 0.085(6) 0.066(4) 0.060(3) 0.063(3) 0.083(5) 0.093(6) 0.079(5) 0.075(4) 0.083(4) 0.109(7) 0.132(9) 0.099(6)

Site occupancy factors, 0.5.

of the structures by vector methods. Residuals R and R , are quoted on F at convergence (preferred hand, 3b,3c); statistical O.O004d'(Zdiff) were weights derived from u2(n = u2(I& employed. Neutral atom complex scattering factors were used;I4 computation used the XTAL 3.0 program system implemented by Hall.I5 Crystal data, coordinates, and equivalent isotropic thermal parameters for the non-hydrogen atoms and geometries of the complexes are given in Tables 1-8, and views of the complexes are shown in Figures 1-3.

+

Results and Discussion Synthesis and Characterization of Complexes. The reagents PdMez(tmedaIza and PdMePh(tmeda)12 and the pallada(I1)cyclopentane complex Pd(C4Hs)(tmeda)13(tmeda = N,",iV'-tetramethylethylenediamine) were chosen as substrates for attempted synthesis of complexes containing [(pz)~BHl-because tmeda is known to be readily displaced by stronger donor Initial lH ligands such as 2,8'-bipyridyl.1g,2a,6,12,13a,b NMR studies of reactions indicated that displacement

Organopalladium(N) Complexes

Organometallics, Vol. 14,No. 1, 1995 203

Table 6. Non-Hydrogen Atom Coordinates and Equivalent Isotropic Displacement Parameters for PdMe&t{ (pz)JBH} (3c) atom

X

Y

Z

U,(A2)

Pd C(a) C(b) C(C) C(d)” C(d’)B B N(a1) N(a2) C(a3) C(a4) C(a5) N(b1) N(b2) C(b3) C(b4) C(b5) N(c1) N(c2) C(c3) C(c4) C(c5)

0.60270(6) 0.62i(ij ’ 0.6115(9) 0.444(1) 0.382(3) 0.618(3) 0.7262(9) 0.6543(5) 0.5902(5) 0.5330(7) 0.5593(9) 0.6365(8) 0.6552(5) 0.5969(6) 0.5399(8) 0.5629(9) 0.6331(8) 0.8084(6) 0.7764(6) 0.8639(9) 0.9552(9) 0.9170(9)

0.20744(6) om(ij ’ 0.1439(9) 0.222(2) 0.1776) 0.448(3) 0.1 162(8) 0.0273(5) 0.0479(5) -0.0407(8) -0.1198(7) -0.0739(7) 0.2132(6) 0.2693(5) 0.3432(8) 0.3368(9) 0.2548(8) 0.1531(5) 0.1953(5) 0.22 1l(9) 0.19% 1) 0.15 14(8)

0.51406(3) 0.5565(6) ’ 0.6016(4) 0.5258(9) 0.533(3) 0.518(2) 0.3934(4) 0.4201(3) 0.4697(3) 0.4792(4) 0.4357(5) 0.3997(4) 0.3749(3) 0.4179(3) 0.3870(5) 0.3256(5) 0.3186(4) 0.4424(3) 0.4970(3) 0.5282(5) 0.4939(7) 0.4414(6)

0.0642(3) 0.121(6) 0.103(4) 0.144(9) 0.25(3) 0.24(2) 0.068(4) 0.063(3) 0.062(2) 0.080(4) 0.090(4) 0.076(4) 0.066(2) 0.068(3) 0.082(4) 0.092(5) 0.077(4) 0.068(3) 0.070(3) 0.089(4) 0.117(6) 0.090(5)

Site occupancy factor, 0.5.

of tmeda by [(pz)3BHl- occurs readily at 0 “C for PdMez(tmeda) and Pd(C4Hs)(tmeda),but that heating to -35 “C is required for PdMePh(tmeda1. Oxidative addition of organohalides to [PdMez{(pz)3BH}I- or [Pd(C4Hs){(pz)aBH}]- occurs at 0-25 “C, but ambient temperatures or above were generally required t o observe reactions for [PdMePh{(pz)~BH}l-.Although temperatures required for synthesis were generally higher than the decomposition temperatures of most previously reported organopalladium(IV) complexes, a series of complexes were obtained in 55-95% yield (eq 2). Water

PdRR’R{(pz),BH}

+ tmeda (2)

PdMe,R{ (pz),BH} : R = Me (l),Et(3), CH,Ph (41, CH,CH=CH, (6) PdMePhR{ (pz),BH}: R = Me (6), E t (7),CH,Ph (81, CH,CH=CH, (9)

Pd(CH2CH,CH2CH,)R{(pz),BH}: R = Me (lo),Et (ll),CH,Ph (121,

Table 7. Selected Bond Distances (A) and Angles (deg) for PdMed(pz)JBW (1) and PdMe3{(~~)4Bl (2), and

~~

Pd-C(a) Pd-C(b) Pd-C(c) Pd-N(a2) Pd-N(b2) Pd- N(c2) C(a)-C(d’) C(c)-C(d) C(c)-C(d’) B-N(a1) B-N(b1) B-N(c1) B-N(d1)

1.45(3) 1.545(6) 1.536(5) 1.542(5)

1.560(9) 1.542(9) 1.538(8) 1.514(9)

1.54(2) 1.53(2) 1.54(2)

2.13(2) 2.05(1) 2.03(2) 2.198(9) 2.165(8) 2.17(1) 1.39(5) 1.40(8) 1.51(2) 1.53(2) 1.59(2)

2.04(1) 2.045(9) 1.97(2) 2.189(6) 2.208(6) 2.174(7) 1.42(4) 0.97(5) 1.52(1) 1.53(1) 1.53(1)

“Bite Distances” for the Poly(pyrazo1-1-y1)borate Ligands N(a2)-N(b2) 2.900(9) 2.932(6) 2.97(1) 2.94(1) 2.945(9) N(a2)-N(c2) 2.922(7) 2.941(5) 2.92(1) 2.93(1) 2.981(9) N(b2)-N(c2) 2.936(7) 2.952(5) 2.90(1) 2.94(1) 2.934(10) C(a)-Pd-C(b) C(a)-Pd-C(c) C(b)-Pd-C(c) N(Q-Pd-N(b2) N(d)-Pd-N(cZ) N(b2)-Pd-N(~2) C(a)-Pd-N(aa) C(a)-Pd-N(b2) C(a)-Pd-N(c2) C(b)-Pd-N(a2) C(b)-Pd-N(b2) C(b)-Pd-N(c2) C(c)-Pd-N(a2) C(c)-Pd-N(b2) C(c)-Pd-N(c2) Pd-N(aZ)-N(al) Pd-N(a2)-C(a3) Pd-N(b2)-N(bl) Pd-N(bZ)-C(b3) Pd-N(~2)-N(cl) Pd-N(cZ)-C(c3) Pd-C(a)-C(d’) Pd-C(c)-C(d) Pd-C(c)-C(d’) N(a1)-B-N(b1) N(a1)-B-N(c1) N(a1)-B-N(d1) N(b1)-B-N(c1) N(b1)-B-N(d1) N(c1)-B-N(d1)

87.3(2) 87.5(2) 87.1(2) 84.7(1) 85.1(1) 85.4(1) 178.4(2) 93.9(2) 94.0(2) 94.0(2) 178.5(1) 93.8(2) 93.4(1) 93.7(2) 178.3(1) 118.2(2) 135.5(3) 117.7(2) 136.2(2) 118.1(2) 135.6(3)

Bond Angles 86.8(4) 87.1(5) 85.8(3) 88.9(7) 88.0(3) 86.1(6) 83.8(2) 86.3(3) 84.5(2) 84.7(4) 84.6(2) 83.3(3) 177.3(3) 178.3(5) 93.9(3) 92.7(4) 94.5(3) 93.9(5) 95.4(3) 93.9(4) 178.0(2) 174.1(5) 93.4(2) 90.8(5) 95.2(3) 92.6(6) 93.9(3) 99.8(5) 178.5(3) 175.7(5) 117.8(4) 118.3(6) 135.8(5) 135.7(9) 119.1(4) 118.5(7) 133.4(5 ) 135.2(9) 120.7(4) 117.7(6) 131.8(4) 135.0(9) 116(1)

108.5(3) 108.7(4) 109.2(3)

109.5(4) 109.2(6) 107.6(5) 107.5(5) 110.3(6) 112.7(4)

87.1(6) 89.4(7) 83.4(7) 84.8(3) 84.4(4) 85.3(3) 175.0(5) 94.7(5) 90.6(5) 93.4(5) 178.2(5) 95.0(5) 95.6(6) 96.2(6) 178.5(6) 116.3(6) 135.9(8) 119.9(6) 133.7(8) 118.5(7) 137(1)

llO(1) 109.4(8)

113(2) 117(3) 111(1) 108.4(9)

107(1)

108(1)

85.4(5) 88.5(8) 88.3(7) 84.1(2) 86.2(2) 84.1(3) 177.4(5) 96.8(4) 91.5(5) 93.6(3) 177.4(3) 94.4(4) 93.9(7) 93.3(6) 177.3(7) 118.1(5) 135.6(6) 116.6(5) 136.4(6) 117.5(5) 134.8(6) 117(2) 139(4) 109.1(8) 109.6(7) 108.9(7)

Table 8. Deviations (A) of Palladium and Boron Atoms from the “Cfiz)’ Mean Planes of Pyrazole Rings, and Angles (deg) between Planes‘ (1)

CH,CH=CH, (13) was rigorously excluded from all reactions, up to but not including the working up stage, as it has been established that the palladium(I1) poly(pyrazo1-1-y1)borate complexes [PdMeR{(pz)aBH}l- (R = Me, Ph) are susceptible to oxidation by water.ll Extensive attempts to obtain crystals suitable for a structural study were successfulfor PdMes{(pz)aBH}(1) and PdMezEt{(pz)3BH)(3)only, and the tetrakidpyrazol-1-y1)borate complex PdMes{(pz)d3} (2) was synthesized and crystallized to allow a comparison with 1. lH and 13C NMR spectra of the complexes are in accord with the formulations presented and may be readily assigned, e.g., occurrence of two pyrazole ring environments in 2:l ratio for PdMezR{(pz)aBH} (R”= Et, CHzPh, CHzCH=CH2) and Pd(C4Hs)R{(pz)3BH}

2.034(4) 2.032(7) 2.024(5) 2.174(3) 2.178(4) 2.177(3)

Bond Dishnces 2.021(8) 2.02(1) 2.026(9) 2.03(1) 2.036(6) 2.06(2) 2.164(6) 2.155(9) 2.177(6) 2.183(7) 2.184(4) 2.18(1)

Pd (ring a) Pd (ring b) Pd (ring c) B (ring a) B (ring b) B (ring c)

0.041(7) 0.034(7) 0.022(7) -0.012(7) 0.013(7) 0.026(8)

rings a/b rings a/c rings b/c

119.0(2) 118.2(2) 122.3(2)

(2)

3a

Deviations O.oo(1) O.lO(2) 0.45(1) 0.19(2) 0.16(1) O.OO(2) O.Ol(1) -0.09(2) 0.07(1) 0.08(2) 0.08(1) -0.06(2) Angles 127.3(3) 127.5(6) 124.2(3) 120.7(6) 108.2(3) 111.4(6)

3b

3c

0.15(2) 0.03(2) 0.21(2) -0.01(2) -0.12(2) 0.06(3)

O.Ol(1) 0.21(2) O.Ol(2) -0.10(2) 0.07(2) -0.03(2)

117.1(5) 115.5(6) 126.8(6)

112.3(4) 124.8(4) 122.8(4)

O x z values for rings a-c, respectively: (1) 1.2, 0.3, 1.1; (2) 0.1, 13.1, 0.3, and for ring d 12.7; (3a) 0.2, 0.2, 0.4; (3b) 4.4, 8.7, 2.4; (3c) 0.3, 1.8, 1.7. Forring d Pd 1.29(2),B 0.33(1) A, ring a/d 91.1(3), ring b/d 134.8(3), and ring c/d 142.5(3)’.

( R= Me, Et, CHzPh, CHzCH=CHz), two pyrazole ring environments in 3:l ratio for PdMe3{(pz)rB}, and three

Canty et al.

204 Organometallics, Vol.14, No. 1, 1995

a

0

P

l

0

Figure 1. Molecular structures of (a, top) PdMes{(pz)sBH) (1)illustrating the noncrystallographicCsUsymmetry and (b, bottom) PdMes{(pz)a}(2) illustrating the deviation (0.45A) of the palladium atom from the mean plane of pyrazole ring b. Thermal ellipsoids (20%) are shown for the non-hydrogen atoms, and hydrogen atoms (constrained at estimated positions)have been given an arbitrary radius of 0.1 A. pyrazole ring environments for PdMePhR”{(pz)sBH}(R” = Et, CHZPh, CH2CH=CH2). Replacement of methyl groups in PdMes{(pz)sBH) by +propenyl, benzyl, or phenyl groups results in a downfield shift for the remaining methyl resonance, as shown in Scheme l a . The protons of the pallada(Iv)cyclopentane rings are present as three resonances in 4:2:2 ratio. For these complexes, the protons closest to R in Pd(C4H8)R”{(pz)gBH}, Ha in Scheme lb, are expected to experience changes in chemical shift similar to that of the methyl groups in PdMezR{(pz)sBH}, allowing assignment of resonances as shown in Scheme lb. Protons opposite to R , Hb, experience upfield shifts, in contrast to Ha. X-ray Structural Studies. Crystals of PdMe3{(pz)3BH} (1) and PdMes((pz)rB} (2) were obtained on dissolution in acetone followed by diffusion of diethyl ether vapor into the solution, and crystals of PdMezEt((pz)sBH} (3) formed from pentane. Three crystalline forms of 3 were detected: complex 3a is ordered, but 3b has disordering of the methyl

Figure 2. Unit cell contents of PdMea{(pz)sBH} (1) projected down b, illustrating the packing of molecules and showing views of the complex in a different orientation. group of PdCH2CH3 between two positions in equal proportions, and 3c has disorder in position between the ethyl group and one of the PdCH3 groups in equal proportions (Figure 3). Disorder in complexes of tripod ligands is not unexpected, and recent examples include octahedral [RIPh~{(pz)~CH}I[II[I~1 which has an asymmetric unit containing one ordered cation and one disordered cation in which the position of the iodine and one of the phenyl groups is disordered.16 All of the complexes have octahedral geometry for palladium (Figures 1-3), and complexes 3b and 3c have geometries similar to those of the other complexes, but in view of the disorder, data for these complexes are generally excluded in detailed comparisons of geometries. The trimethylpalladium(I)complexes 1 and 2 (Figure 1) have bond lengths and angles at the palladium centre within 30, except for C(a)-Pd-C(b) [87.5(2)’ in (l),85.8(3)’ in (211 (Table 7). Complexes 1, 2, and 3a have C-Pd-C angles 85.8(3)-88.9(7)’ and N-Pd-N chelate angles 83.3(3)-86.3(3)”, and complex 1 has noncrystallographic C3” symmetry. The palladium atoms in 1 and 3a-c lie within -0.2 A of the “C3N2” mean planes of coordinated pyrazole rings (Table 7), as found for the related cation [PdMes{(p~)3CH}l+,~ but for complex 2 the palladium atom lies 0.45(1)A from the mean plane of ring b (Figure lb). The larger deviation for the [(pz)rBl- complex appears to result from steric effects between ring d and the coordinated rings; steric interactions of this type between coordinated and uncoordinated rings of tridentate [B(pz)& have been documented recently in studies of complexes of group 2 metal ions.’7 Complex 1 has average values of Pd-C and Pd-N about 0.02 and 0.03 A shorter than those for isoelectronic [PdMe3{(pz)sCH}I+,but these differences are within 20 and the bond lengths in the cation occur over (16) Canty, A.J.;Honeyman, R. T.; Skelton, B. W.; White, A. H. J. Organomet. Chem. 1992,424. 381. (17) Sohrin, Y.;Kokusen, H.; Kihara, S.; Matsui, M.; Kushi, Y.; Shiro, M. J . Am. Chem. SOC.1993,115, 4128.

Organopalladium(N) Complexes

Organometallics, Vol. 14,No.1, 1995 205

Scheme 1. ‘HN M R Chemical Shifts for (a) Methylpalladium(IV)Groups in PdMeR’R“{(pz)sBH}and (b) Pallada(n3cyclopentane groups in Pd(Wb)R{(p)&H} (a) PdMe,

- PdMezEt< PdMe2(CHzPh)e PdMe2(CHzCH=CHz)

e

1.42

1.38

1.55

1.61

-

PdMezPh PdMeEtPh < PdMePh(CHzCH=CHz)< PdMePh(CH2Ph) 1.82 1.81 1.88 1.97

R I

Me

Et

CH,CH=CH*

CHzPh

Ha

3.16

3.20

3.32

3.56

Hb

2.87

2.75

2.76

2.85

Hc,d

1.78

1.79

1.86

1.93

distances” [2.90(1)-2.97(1) AI (Table 7) similar to that of PdMes((pz)&H} [2.89(1)-2.92(1) A], but form larger N-Pd-N bite angles, 83.3(3)-86.3(3)” compared with 8.17(3)-83.2(3)”. The larger angles appear to be directl attributable to B-N bond distances [1.53(2)-1.54that are longer than the analogous C-N bond (2) distances [1.45(1)-1.48(1) A]. The slightly more regular octahedral geometry of the [(pz)3BH]- complexes compared to PdMes((pz)&H) is also reflected in Pd-N(n1)C(n3) angles, which are -2” less in 1 and 3a [135.0(9)136.2(2)”1 than in [PdMe3{(pz)&H}l+ [137.1(7)138.2(6)”1. A similar trend in bite angles is found for P~{(Pz)~BH-N,”}~ [90.1(1Yland [Pd{(p~)&H-N,”)21[BF412 [87.4(5)OI,l8and in these complexes, angles closer to 90” are assumed to result from greater flexibility in the ligands when they are present as bidentates. Complex 3 is the only ethylpalladium(IV) complex for which a crystal structure has been determined, and only two structures appear to have been published for palladium(I1). These complexes, trans-[Pd(SPh)Etexhibit simi(PMe3)21lgaand truns-[PdBrEt(PMe3)21,lgb lar geometries for the ethylpalladium group, although they have smaller Pd-C-C angles, 107.6(6)”and 110.5(5)”,respectively, than that found for 3a, 116(1)”. Stabilities of the Complexes. All of the complexes are stable at ambient temperature and as suspensions in water. When heated in the solid state, they decompose to form black powders over wide temperature ranges, but the PdMePhR complexes appear to be generally less stable than the Pd(C4H8)R”and PdMe2R complexes, and the least stable complexes in each group have R = Et or CH2CH=CH2. These stability trends are consistent with solution behavior, e.g., when studied by lH NMR spectroscopy in toluene-&, the complexes PdMeaR”{(pz)aBH}and Pd(C&I8)R”{(pz)3BH)( R= Et, CH&H=CHz) are stable to a t least 80 “C, but PdMe-

&

P

Figure 3. Molecular structures of PdMezEt{(pz)sBH} showing (a, top) the ordered structure of 3a and disorder in (b, middle) the methyl positions of the ethyl group in 3b and (c, bottom) in positions of the ethyl and methyl groups in (3c). a wider range, Pd-C 2.036(11)-2.060(9) A.8 The [(pz)sBH]- ligands in 1 and 3a exhibit N-N “bite

(18)Canty, A. J.; Minchin, N. J.;Engelhardt, L. M.; Skelton, R W.; White, A. H. J. Chem. SOC., Dalton Trans. 1986,645. (19) (a) Osakada, Y.; Ozawa, Y.; Yamamoto, A. Bull. Chem. Soc. Jpn. 1991,64,2002. (b)Osakada, Y.; Ozawa, Y.; Yamamoto, A. J. Chem. SOC.,Dalton Trans. 1991,759.

Canty et al.

206 Organometallics, Vol. 14,No.1, 1995

PhEt((pz13BH) and PdMePh(CHzCH=CHd{(pz)sBH} decompose at 60-70 “C and -25 “C, respectively,to give black solids. The nature of organic products from these decomposition reactions has not been ascertained. A relatively small number of hydrocarbylpalladium(IV)complexes reported to date are stable at ambient temperature. 1b2g94,6 Hydrocarbylpalladium(IV) chemistry is usually characterized by clean and facile reductive elimination reactions a t low to moderate temperatures to form palladium(I1)products, in particular phenylpalladium(IV) complexes; e.g., PdXMePh(CHzPh)(bpy)(X = Br, I) decompose in both the solid state and solution a t 0 “C to form PdX(CHzPh)(bpy)and to1uene.l’ However, the stabilities of the pallada(IV1cyclopentaneand ethyl- and phenylpalladium(IV) complexes described here are similar to related diorganopalladium(I1) analogues involving bidentate nitrogen donor ligands;12J3ab,20 e.g., the decomposition of Pd(C4H8)(bpy)13aand PdEtn(bpyIz0has been studied in solution at 80 and 60 “C, respectively. Thus, with suitable choice of donor ligand systems, organopalladium(IV) complexes have stabilities comparable to that exhibited in well-established organopalladium(I1) chemistry. Although far fewer studies in organopalladium(IV) than organopalladium(I1)chemistry have been reported to date, it appears that similar principles govern stabilities for “cis-PdR? groups in square-planar palladium(11)and ‘)%c-PdRs”groups in octahedral palladium(IV) complexes. Enhanced stability occurs for complexes containing polydentate ligands that have high donor ability andor ability to adopt a conformation favoring (20) Sustmann, R.; Lau, J. Chem. Ber. 1986,119, 2531.

square-planar geometry for palladium(I1) or octahedral geometry for palladium(IV), because these properties reduce tendencies toward donor group dissociation. For example, Pd(C4Hs)(bpy)is more stable than Pd(C&)(tmeda) where bpy is more rigid than tmeda,13band PdMez(CHzPh)((pz)3BH}is more stable than [PdMez(CHzPh)((pz)3CH)lX (X = Br, BFd9 where [(pz)3BHlis a stronger donor than isoelectronic (pz)&H and presents coordination geometries closer t o octahedral. Similarly, although palladium(IV) appears to be stabilized by anionic “harder” nitrogen and oxygen6 donor ligands, the “soft” thioether donor 1,4,7-trithiacyclononane (9S3) forms very stable complexes [PdMes(9S3)IX (X = I, and the high stability of these complexes may be related to the fac-9S3 group adopting a conformation in the complex which is very similar to that adopted by free 9S3.21

Acknowledgment. We thank the Australian Research Council for financial support, and Johnson Matthey Ltd. for generous loans of palladium chloride. Supplementary Material Available: Listings of nonhydrogen atom thermal parameters, hydrogen atom parameters, and ligand geometry for the complexes (16 pages). Ordering information is given on any current masthead page.

OM9405192 (21)(a) Cooper, S.R.; Rawle, S. C. Stmct. Bonding 1990,72, 1. (b) Blake, A. J.; Schroder, M. Adu. Inorg. Chem. 1990,35,1. (c) Beech, J.; Cragg, P. J.; Drew, M. G. B. J. Chem. SOC.,Dalton Trans. 1994,

719.