J. Am. Chem. SOC.1981, 103, 5115-5125
51 15
Complexes of Functional Phosphines. 4. Coordination Properties of (Diphenylphosphino)acetonitrile, Ethyl (Diphenylphosphino)acetate, and Corresponding Carbanions. Characterization of a New Facile Reversible C02 Insertion into Palladium( 11) Complexes Pierre Braunstein,*2aDominique Matt,2aYves Dusausoy,ZbJean Fischer,zc Andre Mitschler," and Louis Ricard" Contribution from the Laboratoire de Chimie de Coordination, Associd au CNRS (ERA 670), Universitd Louis Pasteur, 67070 Strasbourg Ctdex, France, the Laboratoire de Mindralogie-Cristallographie,Associd au CNRS (ERA 162), Universitd de Nancy 1 , C.O. 140, 54037 Nancy, France, and the Laboratoire de Cristallochimie, Associd au CNRS (ERA OS), Universite Louis Pasteur, 67070 Strasbourg Ctdex, France. Received December 12, 1980. Revised Manuscript Received March 23, 1981
Abstract: The coordination properties of Ph2PCH2CN(L') and Ph2PCH2COOC2H5(L2) have been investigated. Complexes have been prepared and characterized in which they behave either as monodentate ligands through the phosphorus only, as in (aph)PdC1L2 (aph-H = acetophenone N-phenylhydrazone), Pd(dmba)ClL (dmba-H = dimethylbenzylamine), and Pd(8mq)BrL2 (8-mq-H = 8-methylquinoline), or as bidentate ligands through the phosphorus and the functional group Y (Y = CN, COOC2H5),as in [Pd(d~nba)L']~(PF~)~, [Pd(dmba)L2]PF,, and [Pd(8-mq)L2]PFe The carbanions (Ph2PCHY)- derived n
n
n
from L' and L2 were prepared and reacted with the dinuclear [Pd(C N)X], complexes (C N = dmba, X = CI; C N = 8-mq, n
-
n
N) X = Br). When the ratio Pd/L- = 2 was used, dinuclear complexes of the general formula (C N)Pd(p-X)(p-PPh2CHY)Pd(C n were formed. For C N = dmba, X = C1, and Y = COOC2H5,the molecular structure of complex 10 has been determined by X-ray diffraction: monoclinic, space group C:,,-P2,/C with 2 = 4, a = 10.036 (4) A, b = 34.000 (9) A, c = 10.297 (4) A, /3 = 106.82 (2)", p(ca1cd) = 1.556 g/cm3. The structure was solved by using 2015 reflections with I > 3u(I) and refined to conventional R = 0.075. The functional carbanion bridges the two palladium units with Pd( 1)-P = 2.233 (6) A and Pd(2) 3 4 I ) and refined to conventional R = 0.056. The functional carbanion acts now as a ( P , 0)chelate ligand, with Pd-P = 2.242 (2) A and Pd-0 = 2.1 17 (5) A, the phosphorus being trans with respect to the Pd-N w
n
bond.
Complex 13 was reacted with [Pd(C N)X],, affording the dinuclear complexes (dmba)Pd(r-X)(r-Ph2PCHn
n
(COOC2H5)Pd(C N), showing the nucleophilic character of the carbon atom in a position a to the phosphorus. This was further shown by the reaction of 13 with C 0 2 in THF under ambient conditions leading to the C02-insertion product 16
,
i
((dmba)Pd [Ph2PC(C02C2H5)C(0)OH]). The analogous complex 17 ((8-mq)Pd [Ph2PC(C02C2H5)C(0)OH]),was obtained , , in a similar way from complex 14 ((8-mq)Pd[Ph2PCHC(0)OC2H5]).The molecular structure of 17 was established by X-ray diffraction: triclinic, C,'-PT with Z = 4, a = 12.206 (2) A, b = 15.113 (2) A, c = 15.156 (5) A, a = 108.47 (l)", fl = 105.36 (3)O, y = 99.05 (2)", p(ca1cd) = 1.46 g/cm3. The structure was solved by using 2442 reflections with I > 2u(I) and refined to conventional R = 0.070. C 0 2 insertion occurs with C-C coupling to the nucleophilic a-phosphino carbon of the ligand and formation of a new five-membered ring Pd,P,C(12),C(l l),O(l), the ester function no longer interacting with the palladium atom. Spectroscopic IR and IH, I3C, and 31P(1H)NMR data are discussed in relation with the structure and the reactivity of the new complexes. Both 16 and 17 in THF solution liberate C 0 2 when argon is bubbled through under ambient conditions, regenerating 13 and 14, respectively. The new C 0 2 carriers 13 and 14 therefore provide the first examples where reversible C 0 2 fmation by a transition-metal complex has been fully characterized by X-ray diffraction and shown to occur via carbon-carbon bond formation.
The transition-metal coordination chemistry of tertiary phosphines with functional substituents, e.g. nitrile^,^ ethers,6 alkene,'+ alkynes,'O ketones," and aldehydes,12 has aroused (1) Part 3: Braunstein, P.; Matt, D.; Fischer, J.; Ricard, L.; Mitschler, A. N o w . J. Chim. 1980, 4, 493. (2) (a) Labratoire de Chimie de Coordination, ERA 670 CNRS, Universitd Louis Pasteur. (b) Labratoire de Mindralogie-Cristallographie, Universitd de Nancy. (c) Laboratoire de Cristallochimie, Universitd Louis Pasteur. (3) Empsall, H. D.; Hyde, E. L.; Pawson, D.; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1977, 1292-1298. (4) Braunstein, P.; Matt, D.; Mathey, F.; Thavard, D. J. Chem. Res., Synop. 1978, 232-233; J. Chem. Res., Miniprint 1978, 3041-3063. ( 5 ) Cheng, K.; Foxman, B. M. J. Am. Chem. SOC.1977,100,8102-8103. (6) Jeffrey, J. C.; Rauchfuss, T. B. Inorg. Chem. 1978, 18, 2658-2666.
0002-7863/81/1503-5115$01.25/0
considerable interest in the recent past. This is due largely to the expected electronic and/or steric effects of the function. Their evaluation in transition-metal complexes may allow us to determine the role of the function on the overall properties of the metalligand system. In dealing with R2PCH2Y ligands (in which Y (7) Charrier, C.; Mathey, F. J. Organomet. Chem. 1977,128, C41-C43. (8) Mathey, F.; Santini, C. Can. J . Chem. 1979, 57, 753-759. (9) Bennet, M. A.; Johnson, R. N.; Tomkins, I. B. Inorg. Chem. 1975, 14 1908-191 5. (10) Carty, A. J.; Paik, H. N.; Palenik, G. J. Inorg. Chem. 1977, 16, 300-305. (11) Empsall, H. D.; Johnson, S.; Shaw, B. L. J . Chem. Soc., Dolton Trans. 1980, 302-307. (12) Rauchfuss, T. B. J . Am. Chem. SOC.1979, 101, 1045-1047.
0 1981 American Chemical Society
5116 J. Am. Chem. Soc., Vol. 103, No. 17, 1981 has potential donor properties), we have to examine the following features: donor/acceptor effects of Y on the coordination properties of the phosphino group; facilited C-H activation of the adjacent methylene group; evaluation of the bonding modes of the Y function. In the general case the behavior of such a ligand will be as depicted in compounds Ia, b, 11, and 111.
/ /
//
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With late transition-metal elements, the monodentate situation Ia is more frequent than Ib. Nevertheless an example of the latter has been describedI3 recently for M = R h and Y = SOT and is relevant to the preparation of water-soluble catalysts. When coordination properties of P and Y toward a given metal are different, a type I1 structure can lead to a type I structure through a facile M-Y (or M-P) cleavage and therefore create a vacant site a t the metal. These ligands have been called hemilabile6 and may play an important role in homogeneous catalysis. Clearly in a type I11 structure the bridging ligand introduces a dissymmetry in the molecule. An appropriate choice of the other ligands might enhance this effect. This can also be achieved when M and M' are metals of different types, thus making accessible new mixed heterobimetallic systems with or without metal-metal bonds. W e have reported4 the study of complexes of diphenylphosphinoacetonitrile L' or ethyl diphenylphosphinoacetate Lz ">PC Ph
H ECN
L'
P~pCHZCOOCzH5 Ph'
L2
with transition metals such as Fe(O), Au(1) Ni(II), Pd(II), Pt(II), Ir(III), and Rh(II1). All these complexes were of structure Ia except those of Ir(II1) and Rh(II1) with L2, which were of type 11, the latter showing an interesting stereodynamic behavior and illustrating the hemilabile character of Lz. We present here further examples of Pd(I1) complexes with these ligands. Our studies have been extended to the a-carbanions derived from L' and Lz, prepared from either the free or coordinated ligands. In a preliminary comm~nication'~ we have described the reaction of (L1)and (L2)- with cis-PtClz(PhCN)z leading unexpectedly to reaction with the coordinated nitrile. In this work we also report new reactions of these carbanions with cyclometalated Pd(I1) compounds, affording new structures of types I1 and 111. Their reactivity toward COz fixation has been tested and indicates in two examples a reversible fixation under ambient conditions in THF. The COz insertion product has been characterized crystallographically in one case.
Experimental Section A. Reagents and Physical Measurements. All reactions were performed in Schlenk-type flasks under argon. Solvents were distilled under argon from sodium benzophenone ketyl prior to use except dichloromethane, chlorobenzene, and acetone, which were dried and distilled over P205. Ethanol was distilled from Mg(OEt)2. Argon (Air Liquide purified grade) was passed through BASF R3-ll catalyst and molecular sieve columns to remove residual oxygen and water. COz was purchased from Air Liquide (N48). Elemental analysis of C, H, N, and F were performed by the Service Central de Microanalyses du C.N.R.S.. Infrared spectra were recorded in the region 4000-400 cm-' on a Perkin-Elmer 398 spectrophotometer as KBr pellets (unless otherwise sDecifiedl and on a Polvtec FIR 30 FT-interferometer as wlvthene . - disks i i the region 420-50 & - I . The 'H, 13C('H),and 31P(LH)NMR spectra were recorded at 90.00 and/or 250.00, 62.86, and 36.43 MHz, respectively, on a FT-Brucker
(13) Borowski, A. F.; Cole-Hamilton, D. J.; Wilkinson, G. Nouo. J. Chim. 1977,2, 137-144. (14) Braunstein, P.; Matt, D.; Dusausoy, Y.;Protas, J. J. Chem. Soc., Chem. Commun. 1979,163-764. (15) Mathey, F., private communication.
Braunstein et al. WH-90 or Cameca 250 instrument. Proton and carbon chemical shifts are positive downfield relative to external Me4% Positive phosphorus chemical shifts indicate a downfield position relative to H3P04. B. Syntheses. Ligands. Ph2PCHzCN (L')and Ph2PCH2C(0)OC2H5 (L2) were prepared by the method described previ~usly.~ Their NMR data are as follows. L': 'H NMR (CDCI,) 6 2.78 (2 H, d, PCH2, IJ(PH) = 4.5 Hz); "P('H) NMR (CDC13) 6 -17.8; I3C{'H]NMR 6 16.19 (d, PC, 'J(PC) = 28.5 Hz), 117.0 (CN, 2J(PC) cy 5 Hz). L2: 'H NMR (CDCI,) 6 1.11 (3 H, t, 'J = 7.0 Hz), 3.11 (2 H, s, PCH2, 'J(PH) = 0 Hz), 4.03 (2 H, q, )J = 7.0 Hz); 31P('H]NMR (CDC13) 6 -16.6; "C('HJ NMR (CD2C12) 6 14.03 (s, CH,CHz), 35.23 (d, PCH2, 'J(PC) 23.7 Hz), 60.93 (s, CHZCH,), 170.69 (d, C 4 ) . Ph2P(S)CH2C(S)OC2H5(L') was prepared by refluxing a solution of Ph2P(0)CH2C(O)OC2H5(3 g) in toluene (100 mL) with P4SIo(6 g) for 8 h." After being cooled, the mixture was filtered and neutralized with Na2C03. The solvent was removed and the residue was chromatographed on Kieselgel, eluting with toluene. The product was obtained from the first fraction (2.2 9): 'H NMR (CDCI,) 6 1.10 (3 H, t, 'J = 7.2 Hz), 4.17 (2 H, d, IJ(PH) = 14.0 Hz), 4.27 (2 H, q, 'J = 7.2 Hz, 5J(PH) = 0.7 Hz); 31P(1H)NMR (CDC1,) 6 +39.2; I3C('H)NMR (CDCl') 6 12.43 (s, CHj), 51.33 (d, PCH2, 'J(PC) = 41.2 Hz), 68.06 (9, OCH2), 209.02 (C=S). Anal. Calcd for CI6Hl70PS2:C, 59.98; H, 5.35. Found: C, 59.90; H, 5.45. Complexes. [Pd(C N)XI2 (X = Cl, Br) complexes were prepared by previously described methods, for the following cyclometalated (C N) ligands: acetophenoneN-phenylhydrazone (aph),16dimethylbenzylamine (dmba),17 8-methylquinoline (8-mq).I8 Pd(aph)CU2 (1). To a suspension of [Pd(aph)C1lZ (0.370 g, 0.53 mmol) in CH2C12(25 mL) was added dropwise L2 (0.288 g, 1.06 mmol) in CH2C12(5 mL). After 2 h of stirring, the clear solution was filtered. After concentration, pentane was added, affording a yellow-green, airstable, powder of 1 (0.560 g, 89%) (mp 136-138 "C): IR v(NH) 3210 (mbr), v(C0) 1722 (s) cm-l; 'H NMR (CD2C12)6 0.94 (3 H, t, CHICH,, 'J = 7.0 Hz), 2.33 (3 H, S, CCH,), 3.76 (2 H, d, PCHZ, 'J(PH) = 8.2 Hz), 3.77 (2 H, q, CHzCH3,'J = 7.0 Hz); slP(lH)NMR (CD2C12) 6 29.0; "C('HJ NMR (CD2Clz) 6 13.73 (s, CHzm3), 15.29 (s, CH'CN), 37.77 (d, PCH2, 'J(PC) = 29.6 Hz), 61.19 (s, CHzCH3). Anal. Calcd for C,nH,nCIN,O,PPd: C, 57.75; H, 4.85; N, 4.58; Found: C, 54.44;19 H,-j.f5; N,b.?7. Pd(dmbaKIL1(2). To a stirred susDension of IPd(dmba)Cll, . __ (0.552 . g, 1.Ommolj in THF (30 mL) was added slowly L l (0.450 g, 2.0 mmol) in THF (10 mL). After 0.2 h, the mixture was filtered and pentane added to produce green-yellow, air-stable, crystals of 2, which were dried in vacuo (0.920 g, 92%) (mp 99-100 "C): IR v(CN) 2246 (s) cm-'; 'H NMR (CDZCl,) 6 2.83 (6 H, d, 4J(PH) = 2.9 Hz), 3.82 (2 H, d, PCH2, 'J(PH) = 9.4 Hz), 4.06 (2 H, d, NCH2, 4J(PH) 2.6 Hz); "P('H) NMR (CDZC12) 6 33.8; "C('HJ NMR (CDzC12) 6 21.30 (d, PCH2, 'J(PC) = 25.9 Hz), 50.60 (s, N(CH,),), 73.23 (s, NCH2), 115.80 (d, C=N, IJ(PC) N 7 Hz). Anal. Calcd for Cz3HwC1N2PPd:C, 55.11; H, 4.83; N, 5.59. Found: C, 55.00; H, 4.90; N, 5.70. Pd(dmba)CU2(3). To a stirred suspension of [Pd(dmba)C1lZ(0.552 g, 1.0 mmol) in CH2C12(20 mL) was added dropwise a solution of L2 (0.544 g, 2 mmol). This mixture was stirred for 0.2 h and filtered and the solvent removed in vacuo. The residue was washed with pentane and recrystallized from toluene/pentane, affording a pale yellow, air-stable, powder of 3 (0.888 g, 81%) (mp 90-92 "C): IR v(C0) 1733 (s), 1721 (vs) cm-I; far-IR bands 373 (m),362 (m),294 (s), 265 (w). 241 (m), cm-'; 'H NMR (CD2C12)6 1.03 (3 H, t, )J = 7.0 Hz), 2.79 (6 H, d, 4J(PH) = 2.9 Hz), 3.82 (2 H, d, IJ(PH) = 10.6 Hz), 3.83 (2 H, q, 'J 7.0 Hz), 4.04 (2 H, d, 'J(PH) 2.3 Hz); "P('H) NMR (CDzCl2) 6 31.8; "C('H) NMR (CDzC12) 6 13.94 (s, CHzCH,), 37.94 (d, PCH2, 'J(PC) = 27.7 Hz), 50.51 (s, N(CH3)2), 61.22 (s, CHZCH,), 73.38 (s, NCHz), 168.27 (s, C=O). Anal. Calcd for Cz5HZ9C1NO2PPd:C, 54.76; H, 5.33; N, 2.55.
-
-
(16) Braunstein, P.; Dehand, J.; F'feffer, M. Imrg. Nucl. Chem. Len. 1974,
10, 521-524.
(17) Cope, A. C.; Friedrich, E. C. J. Am. Chem. SOC.1968,90,909-913. (18) Hartwell, G. E.; Lawrence, R.V.; Smas, M. J. J. Chem. Soc. D 1970, 912. (19) Experimental C analysis results which are lower than required by theory have also been found in related complexes.20 (20) Dehand, J.; Pfeffer, M.; Zinsius, M. Inorg. Chim. Acro 1975, 13, 229-332. (21) SHELX Crystallographic Calculation Program, G. M. Sheldrick, University of Gottingen, West Germany. (22) See paragraph at the end of paper regarding supplementary material.
Complexes of Functional Phosphines Found: C, 54.70; H, 5.21; N, 2.54. Pd(8-mq)BrL2(4). To a stirred suspension of [Pd(8-mq)BrI2(0.657 g, 1.0 mmol) in THF (30 mL) was added a solution of L2 (0.545 g, 2.0 mmol) in THF (10 mL). After 0.2 h, this solution was filtered and pentane added, affording yellow crystals of 4 (air-stable). These were recrystallized from CH2C12/pentane(1.05 g, 87%) (mp 141-143 "C): IR u(C0) 1711 (s), u(PdBr) 172 (s) or 161 (s) cm-I; 'H NMR (CD2CI2) 6 1.05 (3 H, t, ' J = 7.3 Hz), 3.02 (2 H, d, CH2Pd, 'J(PH) = 3.8 Hz), 3.93 (2 H, d, PCH2, 2J(PH) = 10.0 Hz); "PI'H) NMR (CD2Cl2) 6 28.7; "C('H) NMR (CD2C12) 6 13.84 (s, CH2CH3), 34.25 (s, CH2Pd), 37.34 (d, PCH2, 'J(PC) = 27.5 Hz), 61.22 (s, CH2CH3), 168.28 (d, C=O, 2J(PC) = 4.6 Hz). Anal. Calcd for C26H25BrN02PPd: C, 51.98; H, 4.19; N, 2.33. Found: C, 51.75; H, 4.15; N, 2.42. [Pd(dmba)(L2)]PF,(5). To a solution of 3 (0.274 g, 0.5 mmol) in CH2C12(30 mL) was added a suspension of AgPF6 (0.139 g, 0.55 mmol) in CH2C12 (10 mL). After ca. 0.5 h, the solution was filtered to remove AgCl and then was concentrated. Addition of pentane gave a pale yellow powder which was recrystallized from CH2CI2/pentane to afford airstable 5 (0.259 g, 79%) (mp 80 "C dec): IR (Nujol mull) u(C0) 1651 (s) cm-l; 'H NMR (CD2C12)6 1.35 (3 H, t, ' J = 7.3 Hz), 2.93 (6 H, d, 'J(PH) = 2.9 Hz), 3.86 (2 H, d, 2J(PH) = 11.1 Hz), 4.08 (2 H, d, 4J(PH) = 2.3 Hz), 4.41 (2 H, q, ' J = 7.2 Hz); "P('H} NMR (CD2CI2) 6 26.4 (s, PdP), -142.6 (sept, 'J(PF) = 710.5 Hz); "CI'H} NMR 6 13.64 (s, CHzCH,), 40.69 (d, 'J(PC) = 33.3 Hz), 50.48 (s, N(CH3)2), 66.93 (s, CH2CH3), 70.49 (s, NCH2). Anal. Calcd for C25H29F6N02P2Pd:C, 45.64; H, 4.44; N, 2.13. Found: C, 45.73; H, 4.49; N, 2.19. [Pd(8-mq)L2]PF6 (6). To a stirred solution of 4 (0.300 g, 0.5 mmol) in CH2C12 (20 mL) was added a suspension of AgPF6 (0.139 g, 0.55 mmol) in CH2C12 (10 mL). After 0.5 h of stirring the mixture was filtered. The addition of pentane gave, after cooling at -10 OC,white crystals of 6 (0.05 g, 15%) (mp 98-100 " C ) : IR u(C0) 1628 (sbr) cm-I; 'H NMR (CD2C12) 6 1.41 (3 H, t, ' J = 7.3 Hz), 3.59 (2 H, d, CH,Pd, 'J(PH) = 3.9 Hz), 3.92 (2 H, d, PCH2, zJ(PH) = 11.2 Hz), 4.44 (2 H, q, ' J = 7.3 Hz); 31P{1H) NMR (CD2CI2)6 24.5 (s, PdP), -142.5 (sept, PF6, 'J(PF) = 711 Hz); "C NMR (CDZC12) 6 13.64 (q, CH2CH3, ' J (CH) = 123 Hz), 25.24 (t, CH2Pd, 'J(CH) = 139 Hz), 39.37 (t of d, PCH2, 'J(PC) = 31.4 Hz, 'J(CH) = 134 Hz), 66.87 (t, CH2CH3,' J (CH) = 154 Hz), 180.50 (d, C=O, 2J(PC) = 10 Hz). Anal. Calcd for C26H2p6N02P2Pd: c , 46.90; H, 3.79; N, 2.10. Found: C, 46.96; H, 3.70; N, 2.16. [Pd(d~nba)L']~(PF~)~ (7). To a stirred solution of 2 (0.251 g, 0.50 mmol) in CH2CI2(30 mL),was added a suspension of AgPF, (0.139 g, 0.55 mmol) in CH2Clz(10 mL). The mixture was stirred for 0.5 h and carefully filtered. The solvent was then removed in vacuo, and the white product 7 was washed with pentane and dried (0.025 g, 8%) (mp 215 OC dec): IR u(CN) 2298 (m) cm-I; 'HNMR (CD2CI2)6 2.93 (N(CH?),, 'J(PH) = 2.9 Hz). More data were precluded by the very low solubility of 7. Anal. Calcd for C46H48F12N4P4Pd2: C, 45.23; H, 3.96; N, 4.59. Found: C, 45.25; H, 4.08; N, 4.69. Preparation of a Standard Solution of (L1)(A). To a solution of dry N-isopropylcyclohexylamine(0.706 g, 5.0 mmol) in THF (25 mL) was added dropwise at -20 OC a 1.73 M hexane solution of n-C4H9Li(2.9 mL). After ca. 0.5 h, this solution was added dropwise at -5 OC to a solution of L' (1.125 g, 5 mmol) in THF (25 mL). In the following, solution A will be considered as containing mainly the carbanion (L1)with some unreacted L1. Preparation of a Standard Solution of (L2)- (B). The procedure used was similar to that described for (L1)-, using 1.361 g (5.0 mmol) L2.
.
Pd(dmba)(r-CI)[p-P$PCH(CN)]Pd(dmba) (8). To a stirred suspension of [Pd(dmba)ClI2 (1.104 g, 2.0 mmol) in THF (30 mL) was added at -10 OC 20 mL of solution A. This solution was stirred for 0.5 h, and pentane (100 mL) was added. After 3 h at room temperature, white, air-stable, crystals of 8 were collected and recrystallized from THF/pentane (0.960 g, 65% based on Pd) (mp 244 "C dec): IR u(CN) 2192 (m) cm-'; 'H NMR (CD2C12)6 2.50 (3 H, s, CHpsNPdC*),2.60 (3 H, s, CH,bNPdC*), 2.73 (3 H, d, CH3sNPdP,4J(PH) = 2.1 Hz), 2.96 (3 H, d, CH'bNPdP, 4J(PH) = 2.9 Hz), 3.63 (2 H, S, CH2NPdC*), 3.64 ((1 H, d, PCH, 2J(PH) = 13.8 Hz), aA 3.67 and bB 4.45 (2 H, ABX spin system, CHApNPdP,J(HAHB)= 13.5 Hz, 'J(PHA) E 0 Hz, 4J(PHB) = 1 Hz); "P{IH) NMR (CD2C12)6 52.0 (s); "C('H) NMR (CD2C12) 6 14.51 (d, 'J(PC) = 20.34 Hz), 49.60 (s, NCHJ, 50.16 (s, NCH'), 51.04 (s, NCH'), 51.43 (s, NCHd, 71.76 (s, NCH,), 72.40 (s, NCH,). Anal. Calcd for C32H35CIN,PPd2:C, 51.88; H, 4.76; N, 5.67. Fouid C, 51.99; H, 4.71; N, 5.79. Complex 9 (See Results and Discussion). This compound was obtained in variable amounts (yield 20-30?6) when at -10 "C 40 mL of solution
J. Am. Chem. SOC.,Vol. 103, No. 17, 1981 5117 A was added to a stirred suspension of [Pd(dmba)C1I2(1.104 g, 2.0 mmol) in THF (50 mL). This solution was stirred for 0.5 h and pentane added, affording crystals of complex 8. After isolation of 8 and further addition of pentane, yellow-green crystals of 9 precipitated. These were recrystallized from CH2C12/pentane,affording stable pale yellow crystals in 9 (mp 168 OC dec): IR u(NH) 3285 (s), v(CN) 2158 (s) cm-I; 'H NMR (CD2C12) 6 2.86 (6 H, d, N(CH,)2, 2J(PH) = 2.6 Hz), 3.02 (6 H, d, N(CH3)2,2J(PH) = 2.2 Hz), 4.01 (6 H, unresolved signals); ,'P('H} NMR (CD2C12)6 40.3 and 44.2; "C('H) NMR 6 36.0 (center of 4 signals; tentative assignment, two different P C groups), 51.1 3 and 5 1.69 (2 signals; tentative assignment, two different N(CH3)2groups), 73.17 and 73.75 (2 signals; tentative assignment, two different NCH2 groups). Pd(dmba)(~-CI)(c(-Ph2PCH(C02C2H5)Pd(dmba) (10). To a stirred suspension of [Pd(dmba)CIl2(0.552 g, 1.0 mmol) in THF (20 mL) was added at -20 OC 10 mL of solution A. Solubilization rapidly occurred, and after 5 h of stirring, pentane was added to produce white crystals of 10 which were collected and recrystallized from THF/pentane (0.481 g, 61% based on Pd). Suitable single crystals for X-ray diffraction were obtained from THF/pentane at 20 OC (mp 205-209 "C dec): IR v(C0) 1672 (s) cm-I; 'H NMR (CD2C12)6 1.19 (3 H, t, ' J = 7.0 Hz), 2.46 (3 H, S, CH''NPdC*), 2.53 (3 H, S, CHSbNPdC*),2.72 (3 H, d, CH3'NPdP, 4J(PHa)= 1.5 Hz), 2.97 (3 H, d, CH,bNPdP, 4J(PHb) = 3.0 Hz), 3.03 (1 H, d, PCH, 'J(PH) = 11.4 Hz), 6 A 3.52 and 6 B 3.65 (2 H, AB spin system, CHAHBNPdC*,J(AB) = 13.6 Hz), 6,3.97 and 6 B 3.62 (2 H, ABX spin system, CHAHBNPdP,J(AB) = 13.6 Hz, 4J(PHA)= 0 Hz, 4J(PHB)= 3.4 Hz), 4.05 (2 H, OCH2CH3,center of the AB part of an ABX3 spin system); "P('H) NMR (CD2C12)6 50.7; "CI'H) NMR (CD2CI2) 6 14.74 (s, CH3CH20), 36.61 (d, PC, 'J(PC) = 24.4 Hz), 49.52 (d, H3CANPdP,'J(PCA) = 4 Hz), 49.86 (s, H,CANPdC*), 51.17 (s, H3@NPdC*), 51.53 (d, H3CBNPdP,'J(PCB) N 3 Hz), 59.33 (s, OCH;), 72.00 (s, CH,NPdC*): 72.58 (d, CH2NPdP, 'J(PC) = 3 Hz), 175.21 (d, C=O). 2J(PC) = 6.1 Hz). Anal.' Calcd for C34HiC1N202PPd2:C, 51.83; H, 5.12; N, 3.56. Found: C, 52.05; H, 4.90; N, 3.75.
.
Pd(8-mq)(~Br)[p-Ph2PCH(CN)]Pd(8-mq)(11). To a stirred suspension of [Pd(8-mq)BrI2 (0.657 g, 1.0 mmol) in THF (20 mL) was added 10 mL of solution A at -10 OC. Solubilization occurred, and after 0.3 h pentane (40 mL) was added, producing air-stable yellow-green crystals of 11 which were recrystallized from C6H5Cl/hexane (0.440 g, 55%) (mp 229-230 OC dec): IR v(CN) 2173 (m)cm-I; far-IR 329 (s), 265 (m), 244 (m), 203 (s), 172 (vs), 161 (sh) cm''; 'H NMR (CD2C12) 6A 3.00 and 68 3.1 1 (2 H, ABX spin system, CHAHBPdP,2J(HAHB)= 14.4 Hz, 'J(PHA) = 3.8 Hz, 'J(PHB) = 3.4 Hz), 6A 2.95 and 6B 3.23 (2 H, AB spin system, CHAHBPdC*,J(HAHB)= 14.8 Hz), 3.26 (1 H, PCH, 'J(PH) = 8.0 Hz); "P{'H} NMR (CD2Cl2) 6 35.3; "C('H) NMR (CD2C12) 6 1.44 (d, PC, 'J(PC) = 10.7 Hz), 31.85 (s, CH,Pd), 34.42 (s, CH2Pd). Anal. Calcd for Cj4H2,BrN3PPd2: C, 50.97; H, 3.40; N, 5.24. Found: C. 51.23:. H., 3.53:. N., 5.05.
.
,
Pd(8-mq)(p-Br)[p-Ph2PCH(C02C2H5)]Pd(8-mq) (12). To a stirred suspension of [Pd(l-mq)Brl, (0.657 I,1.0 mmol) in THF (20 mL) was The reaction rapidly occurred, added 10 mLof soluti& Bat -10 and after 0.3 h of stirring, pentane was added (150 mL), yielding a yellow air-stable powder. 12 was recrystallized from THF/pentane (0.407 g, 48%) (mp 209-21 1 OC dec): IR v(C0) 1672 (s) cm-l; far-IR bands 265 (s), 243 (m), 205 (m), 176 (vs) cm-'; 'H NMR (CD2CI2)6 1.18 (3 H, t, ' J = 7.2 Hz), aA 2.96 and dB 3.03 (2 H, ABX spin system, CHAHBPdP, 'J(PHA) = 3.4 Hz, 'J(PHB) = 2.7 Hz), 3.33 (s, 2 H, CH2PdC*), 3.51 (1 H, d, PCH, 2J(PH) = 4.5 Hz), 4.08 (2 H, OCH2CH3,center of the AB part of an ABX, spin system); )'P('H) NMR (CD2C12)6 39.5; I3C('H}NMR (CD2C12) 6 14.40 (s, CHjCH20), 25.59 (d, PC, 'J(PC) = 21.4 Hz), 28.48 (s, CH,Pd), 33.06 (s, CH,Pd), 58.67 (s, CHzCH,), 175.72 (s, C=O). Anal. Calcd for C36H32BrN202PPd2: C, 50.97; H, 3.80; N, 3.30. Found: C, 50.86; H, 3.93; N, 3.62.
'e.
Pd(dmba)[Ph2PCHC(0)02H5] (13). To a stirred suspension of [Pd(dmba)C1I2(1.104 g, 2 mmol) in THF (20 mL) was added at -20 "C 40 mL of solution B. Solubilization occurred, and after 0.3 h of stirring at +10 "C, pentane (100 mL) was added. White crystals of 13 developed. They were separated and recrystallized from THF/pentane (1.2 g, 58%). Suitable single crystals for X-ray diffraction were obtained from THF/pentane at 20 OC (mp 18G200 "C) (slow decomposition): IR u(C0) + u(CC) 1515 (vs) cm-I; 'H NMR (THF-d8) 6 1.37 (3 H,t, ' J = 7.0 Hz), 2.94 (6 H, d, N(CH')2, 4J(PH) = 2.0 Hz), 3.15 (1 H, d, 2J(PH) = 0.9 Hz), 4.10 (2 H, d, NCH2, 'J(PH) E 2 Hz), 4.18 (2 H, q, ' J = 7.0 Hz); "P('H} NMR (CD2Cl2) 6 20.6; "C('H) NMR (CD2Cl2) 6 15.22 (s, CH2CH3), 49.84 (d, (CH,)2N, 'J(PC) 3.0 Hz), 50.84 (d, PC, 'J(PC) = 77.8 Hz), 61.66 (s, CHZCHJ, 71.24 (d, CHIN, 'J(PC)
51 18 J. Am. Chem. SOC.,Vol. 103, No. 17, 1981
-
Braunstein et al.
Table I. Summary of Crystal Data and Intensity Collection of 10 and 13 compd formula fw cryst system a, A
(dmba)Pd&-Cl)[pPh, PCH(CO,C,H,)]Pd(dmba) (10) (dmba)Pd [Ph,PCH(O)OC, H, ] (13) C,,H,,ClN, 0, PPd, C,,H,,NO,PPd 787.93 511.88 monoclinic orthorhombic 10.036 (4) 17.285 (5) b, A 34.000 (9) 17.026 (5) c, A 10.297 (4) 15.687 (4) P, deg 106.82 (2) v,A 3 3363 4616 Z 4 8 d(calcd), g C I T - ~ 1.556 1.476 d(obsd), g 1.53 * 0.02 1.45 t 0.02 cryst dimens, mm 0.065 X 0.080 X 0.240 0.070 X 0.240 X 0.260 space group P21/C (C:h, NO. 14) Pbca (Dih, No. 61) temp, "C 25 "C 25 "C radiation Mo Ka from monochromator Mo K a from monochromator (h(Mo K a I ) = 0.709 30 A linear abs coeff, cm-I 12.08 8.82 scan speed, deg s-' 0.016 0.020 scan range 0.9" + (Mo K q a , splitting) 1.0" + (Mo K a I a z splitting) 28 limits, deg 4-45 6-5 5 data collected 4781 4208 unique data used 20151 > 3oQ 20371 > 3 0 0 R = X UFOI - IFc Il/X IFoI 0.075 0.056 R , = ( C W (IFoI- I F , I ) ~ / ~ W F ~ ~ 0.095 )~'~ 0.078 std error in an observn of unit weight 1.97e 1.63e p fudge factor 0.08 0.08 = 3.1 Hz)8, 179.26 (d, C=O, 2J(PC) u 32 Hz). Anal. Calcd for C25H28N02PPd:C, 58.66; H, 5.51; N, 2.74. Found: C, 58.71; H, 5.75; N, 2.77. Pd(8-mq)[PhzPCHC(0)OCzH5J (14). To a stirred solution of 4 (0.600 g, 1.0 mmol) in THF (25 mL) was added a suspension of NaH (0.026 g, 1.08 mmol) in THF (10 mL). After 48 h of stirring at room temperature, the mixture was carefully filtered and pentane added to precipitate 14. Recrystallization from THF/pentane afforded a pale yellow powder (0.473 g, 91%) (mp >115 "C): IR v(C0) + v(CC) 1508 (ssh), (ligand 8") 1504 (s) cm-'; IH NMR (CDzClz) 8 1.35 (3 H, t, 'J = 7.2 Hz), 3.22 (2 H, d, CHzPd, 'J(PH) N 2 Hz), 3.31 (s, 1 H, PCH), 4.16 (2 H, q, 'J = 7.2 Hz); 'IP(lHJ NMR (CD2CIz) 8 17.0; "C(IH) NMR (CDzCl2) 8 15.23 (s, CHIICHZ), 20.77 (d, CHzPd, 'J(PC) = 4.6 Hz), 48.81 (d, PC, 'J(PC) = 77.8 Hz), 61.57 (s, CH2CH3), 179.96 (d, C=O, 2J(PC) = 32.5 Hz). Anal. Calcd for Cz6Hz4N02PPd:C, 60.07; H, 4.65; N, 2.69. Found: C, 60.13; H, 4.79; N, 2.76. Compound 14 could also be obtained by a procedure analogous to 13, but this reaction proved to be less satisfactory, the compound being difficult to purify and obtained in lower yield. Pd(dmba)(p-Br)[rc-PhzPCH(COOCzH5)]Pd(8-mq) (15). To a solution of 13 (0.256 g, 0.5 mmol) in THF (20 mL) was added [Pd(S-mq)BrJ2(0.164 g, 0.25 mmol) suspended in THF (15 mL). After 12 h of stirring at room temperature the pale green solution was filtered and concentrated, and 15 was precipitated by addition of pentane, isolated as yellow-green powder, washed with pentane, and dried in vacuo (0.399 g, 95%) (mp 132-134 "C): IR v(C0) 1674 (vs) cm-I. 'H NMR (CDzClz) 8 1.19 (3 H, t, 'J = 7.0 Hz), 2.85 (3 H, d, CHIAN,4J(PHA)= 1.9 Hz), 3.03 (3 H, d, CH3BN,4J(PHB)= 2.7 Hz), 3.22 (1 H, d, PCH, 'J(PH) = 7.8 Hz), 3.37 (2 H, S, PdCHz), &A 3.83 and 4.34 (2 H, ABX spin s stem, CHAHBNPdP,2J(HAHB)= 13.6 Hz, J(PHA) = 2.7 Hz, J(PH ) N 0 Hz), 4.01 (2 H, OCHzCH3,center of the AB part of an ABX3 spin system); 31P(lH]NMR (CDZClz)8 50.8. Anal. Calcd for C35H,6BrN20zPPdz:C, 50.02; H, 4.32; N, 3.33. Found: C, 50.27; H, 3.97; N, 3.02. Reaction of 13 with COzTo Produce 16. This reaction was performed in an NMR tube when C 0 2 was bubbled through under ambient conditions into a THF-d8 solution of 13 (0.02 M). After 15 s the signals due to 13 had completely disappeared and were replaced by those of the new compound 16 'H NMR (THF-d8) 8 0.94 (3 H, t , CH3CHz,'J = 7.1 Hz), 2.94 (6 H, d, (H,C)2N, 4J(PH) = 1.9 Hz), 4.02 (2 H, q, CHzCH3, 3J=7.1Hz),4.07(2H,d,CHzN,4J(PH)lHz),13.91(=1H,br, OH); IR (THF) 1733 (w), 1643 (sh), 1612 (vs), 1582 (w), 1551 (s) cm-I. This reaction was shown to be reversible by bubbling pure argon into the previous solution. After 60 s the NMR signals of 16 were totally replaced by those of 13. This experiment could be repeated for many cycles without any noticeable signs of decomposition. Attempts to isolate pure 16 in the solid state failed, even on a larger preparative scale.
K
Reaction of 14 with COz To Prepare (8-mq)Pd[Ph2PC(COzC2H5)C(O)OH] (17). This quantitative reaction was performed in the Same way as the above one, but using 14 as substrate. Regeneration of 14 was observed by bubbling pure argon through a THF solution of 17. Suitable single crystals for X-ray diffraction were obtained at -70 "C from a toluene/pentane solution: IR (THF) 1730 (w), 1651 (sh), 1613 (vs), cm-'; 'H NMR (CD2C12)d 1578 (w), 1552 (s), 1504 (s) (ligand 8") 0.95 (3 H, t, CH3CH2, 'J = 7.1 Hz), 3.12 (2 H, d, CHZPd, 'J(PH) = 3.2 Hz), 4.00 (2 H, q, CHzCH3, ' J = 7.1 Hz), 13.90 (1 H, br, OH). Anal. Calcd for Cz7HZ1NO4PPd:C, 57.51; H, 4.29; N, 2.48. Found: C, 57.44; H, 4.25; N, 2.50. , C~S-P~[P~~PCHC(O)O (18). C ~ HTo ~ ]a~solution of cis-PtCl2(L2)2 (0.404 g, 0.5 mmol) in THF (20 mL) was added a suspension of NaH (0.026 g, 1.08 mmol) in THF (10 mL). After 48 h of stirring, the solution was carefully filtered and pentane added to precipitate 18 as a beige powder. It was recrystallized from THF/pentane (0.336 g, 91%) (mp >IO0 "C): IR v(C0) + v(CC) 1518 (vs) cm-I; 'H NMR (CDZCl2) 8 1.31 (6 H, t, 'J = 7.2 Hz), 3.27 (2 H, d, 2J(PH) = 4.2 Hz), 4.10 (4 H, q, ' J = 7.2 Hz). Anal. Calcd for CjzH3z04PzPt:C, 52.10; H, 4.37. Found: C, 51.71; H, 4.20. C. Collection of the X-ray Data and Structure Determination. The X-ray crystal and molecular structures of compounds 10 and 13 were determined by Fischer, Ricard, and Mitschler and that of compound 17 by Dusausoy. Compounds 10 and 13. Cell constants and other pertinent data are presented in Table I. Intensity data were collected on a four-circle Philips PW1100/ 16 diffractometer. No intensity decay was observed during the data collection periods. It was not possible to grow a crystal of 10 with greater dimensions, and the diffraction power of this crystal was low. The raw step-scan data were converted to intensities and standard deviations by using the Lehman-Larsen a l g ~ r i t h m . ~ ' The net intensities have been corrected for Lorentz and polarization factors and for absorption effects by using the Busing and Levy numerical integration. The structures were solved on a PDP 11/60 computer using the Enraf-Nonius structure determination package24 and the heavy-atom method. Refinements by full-matrix least squares
7
~~
(23) Lehmann, M. S.; Larsen, F. K.Acta Crystallogr.,Sect. A 1974, A30, 508.
(24) Frenz, B. A. "The Enraf-Nonius CAD4 SDP. Computing in Crystallography", Schenk, H., Orthof-Hazekamp, Van Konigsveld, H., Bassi, G. C.. Eds.: Universitv Press: Delft. Holland. 1978. D 64. (25) Redfield, D. A.;Nelson, J. H'.; Cary, L. W. Inorg. Nucl. Chem. Lett. 1974, 10, 727-133.
J. Am. Chem. Soc., Vol. 103, No. 17, 1981 5119
Complexes of Functional Phosphines Table 11. Summary of Crystal Data and Intensity Collection of 17 I
compd formula fw cryst system a, A
b, a c, A a,deg
P, deg 7,deg
v,A3
2
d(calcd), g cm-3 cryst dimens space group temp, "C radiation linear abs coeff, cm-' scan speed scan range, deg 28 limits, deg data collected unique data used R=ZllFoIlFcll/Z lFol R , = ( Z W ( IFoI IFc I)' / c wFo 2 )l "
p fudge factor
and Fourier methods. Refinements by full-matrix least squares (all nonhydrogen atoms anisotropic) have proceeded to the R factor values indicated in Table 11, using the She1 Xz' method. Final positional and thermal parameters for all atoms as well as a table listing the observed and calculated structure factor amplitudes of the reflections used in the refinement are available as supplementary materiaLZ2
I
(8-mq)Pd[Ph2PC(C0,C,H,)C(0)0H] (17) C,,H,,NO,PPd 563.87 triclinic 12.206 (2) 15.113 (2) 15.156 (5) 108.47 (1) 105.36 (3) 99.05 (2) 2461.7 (8) 4 1.46 Os6 X 0.07 X 0.07 mm P1 (Ci,No. 2) 25 CUKa (h(Cu Ka,)= 1.54051 A) 74 variable (1.25 + 0.14 tan 0 ) 4-60' 4800 24421 > 2 0 0 0.070
Results and Discussion Complexes with PhzPCHzY(Y = CN,COOCzH5). The neutral palladium complexes with L' or L2 were obtained in good yields (see Experimental Section) by reacting the cyclometalated n
[(C N)PdXl2 complexes with a stoichiometric amount of ligand (Scheme I). Bridge cleavage occurs easily, and for the resulting complexes 1-4, the spectroscopic data (IR, N M R ) indicate that the function Y does not interact with the metal and that the halogen is always found trans with respect to the u-bonded C atom, which is in agreement with the reluctance of phosphines to bind in this position. This has already been found in related complexes.zO From these and previous4 investigations it can be deduced that when L1' and Lz act as monodentate ligands, their coordinating power is very similar to PPh3. Their main interest is to be found in their chelating or bridging ability and in the facilitated C H cleavage in the position a to the coordinated phosphorus. These points will be discussed later (vide infra). In complexes 5 and 6, obtained according to eq 1, the C O
0.087 0
IC\ /PPh2CH2C00C2H5 D A
Scheme I
\N/'
"LX
AgPF6
CHZCIZ
n n
3, C N = dmba, X = C1 4, C N = 8-mq, X = Br
n
CN
Q
X
L
c1
L'
r 1
Ph
5
6
H/N\Ph
H3C
l+
L
I
?/
Ph
(dmba) (dmba)
c1 c1
L1 L'
2 3
Br
L2
4
'
\CH3
(all nonhydrogen atoms anisotropic) have proceeded to the R factor values indicated in Table 11. The coordinates of the hydrogen atoms were computed with a C-H distance of 0.95 A; their contributions were introduced in structure factor calculations. Final positional and thermal parameters for all atoms as well as a table listing the observed and calculated structure factor amplitudes of the reflections used in the refinement are available as supplementary material.22 Compound 17. Cell constants and other pertinent data are presented in Table 11. Intensity data were collected on a Nonius CAD 4 diffractometer. No intensity decay was observed during the data collection periods. It was not possible to obtain better diffracting crystals, and the quality of the structure determination is given by R , Rw Table 11), and the u values (Table VII). Absorption corrections were omitted in view of the low linear absorption coefficient. The structure were solved by Patterson
stretching frequencies at 55 1 and 1628 cm-I, respectively, accounted for the chelating behavior of the phosphine ester. Their difference is related to a Pd(I1) less electron deficient in 5 than in 6, requiring less electron donation from the ester function. As for 3 and 4, the phosphorus atom binds trans to nitrogen in 5 and 6 . This is easily deduced from the observation of the coupling constant of N(CH3)2 protons with phosphorus in 5 (4J(PH) = 2.9 Hz). For both compounds 5 and 6 a high-field shift of ca. 5 ppm of the 31PN M R signal has occurred when compared to the corresponding shifts for 3 and 4. Shaw and et al. have shown that similar phosphine ester ligands can undergo base-promoted 0-metallation with loss of the C2H5 group. We have also observed such a reaction from (8-mq)Pd(Br)L2 in the presence of BuLi in THF, leading to26 Ph
Ph
A further example of dealkylation is given in eq 2,27from which ( 2 6 ) This was a byproduct observed in variable quantities in the reaction
of [(8-mq)PdBrJ2with solution B, when a slight excess of BuLi was present
(coming from the lithium amide synthesis). We have checked that this compound does not result from reaction of 4 with the amide but with BuLi.
5120 J. Am. Chem. SOC.,Vol. 103, No. 17, 1981 N I C P ~t C,H,I
t P~~P-CH~-CC-OC~H~
IIS
IIS
Braunstein et al.
Ph \
@
'
t 2
c'\p+/N CI'
Ph
/
TH F
[PhzPCHYI-
0 *C
\Ph
we expected the obtention of a nickel(I1)-phosphine thioester complex, potential4 precursor of Ph2PCH2C(S)OC2H5.Instead, S-metalation and dealkylation occur, related to the affinity of nickel for sulfur. With L' on the other hand, chelation of the ligand was never observed because of the constraint imposed by the nitrile group. Bridge formation occurred in 7, prepared according to eq 3. In
Ph
Y = CN, COOC,H,
toward L-. In these complexes, the organometallic chelating ligand (dmba or 8-mq) was not expected to react with the carbanion, leaving therefore only two potential reactive coordination sites. Addition of 1 equiv of L- to [(C>)PdXl2
n
.Ph
in THF (eq 5 ) led
2, C N = dmba
r
N-
'i\
7
spite of the low solubility of 7 in usual organic solvents, its 'H N M R spectrum shows that the phosphorus atom is still coordinated trans to nitrogen (4J(PH) = 2.9 Hz). The increase of the v(CN) frequency (2298 cm-I) when compared with the value in the free ligand (2240 cm-I) indicates a u coordination of the -C=N function through the nitrogen. We therefore suggest for 7 the binuclear structure depicted above. Complexes with [Ph2PCHYr (Y = CN, COOC2H5). These ligands can be prepared by reacting LiN(c-C6Hll)(i-Pr)at -5 OC with a THF solution of L' or L2. Whereas the carbanion [L1]has previously been used in the Wittig reaction,28 [L2]- had not yet been reported. Beside the carbanions themselves, each of their solutions (solution A for Y = CN; solution B for Y = COOC2Hs) contained variable amounts of the corresponding phosphine (ca. 20%, see Experimental Section). This explains the isolation in each of the following reactions of secondary products with neutral ligands L1 or L2. These complexes have been described above and will not be further discussed. In view of the known lability of the nitrile ligand in PtC1,(PhCN)2, this complex was a good candidate for the preparation
n n 10, C N = dmba, X = C1, Y = COOC, H, n 11, C N = 8-mq, X = Br, Y = C N n 8 , C N = dmba, X = C1, Y = CN
12, C N = 8-mq, X = Br, Y = COOC,H,
to the binuclear Pd(I1) complexes 8, 10, 11, and 12. It is easily deduced from their I R spectra that the Y functions do not take part in the bonding to the metals ( v ( C 4 ) = 1672 and 1672 cm-' for 10 and 12; v(C=N) = 2192 and 2173 cm-' for 8 and 11, respectively). The presence of the single resonance in the jlP N M R spectrum excludes the existence of different isomers. The chirality of the C* atom in the bridge induces inequivalence of the OCH2 protons, giving for the ethyl protons in complexes 10 and 12 an ABX3 spin system. Because of their geometry the two different bridging groups between the metals give rise to nonen
quivalence for the two Pd(C N ) moieties. The ' H and 13CN M R spectra of 8 andd 10 clearly showed the inequivalence of the four N-methyl groups. The occurrences of an ABX pattern (X = P) for the CH2NPdP protons and of an AB pattern for the of the Pt-P-C triangular species by reaction with [L1]- or [L2]-. Such units should indeed present a very interesting r e a c t i ~ i t y . ~ ~ ' ~ CH2NPdC* protons are further evidence for the lack of symmetry in the molecules. The observation of 4J(P-H) coupling constants Surprisingly, nucleophilic attack occurs at the coordinated nitrile n and not at the metal center (eq 4), leading to a bis five-membered for one Pd(C N ) moiety indicates a trans NPdP arrangement as ring structure and presenting what appeared to be the first reaction found, e.g., in 5. This was confirmed by the X-ray structure of a carbanion with a coordinated nitrile." determination of 10 and is also suggested for complexes 11 and In reaction 4 the four ligands around the platinum contribute 12. to the formation of the new compound. In order to restrain the The molecular structure of 10 is shown in Figure 1. Crystal reaction possibilities with the functional carbanions, we decided data are given in Table I, the interatomic distances and angles to investigate the reactivity of cyclometalated Pd(I1) complexes in Table 111, and least-squares planes in Table IV. From the stereoview of the molecule (Figure 2) one clearly sees its folding along the C 1 4 ( 13) axis, the angles between the two square planes (27) Synthesis of CpNi[PhzPCHzC(0)S]: a toluene solution of Ph2Pbeing 36.3'. The Pd( 1)-Pd(2) distance (3.88 A) is too long for (S)CHzC(S)OC2HS(6.4 g, 20 mmol), NiCp, (9.44 g, 50 mmol),and C 3 H ~ I (3.36 g, 20 mmol) was refluxed for 7 h. This mixture was then chromatoany metal-metal interaction. Similarly no interaction is to be found between the ester function and the metals. The three fused graphed on a silica gel column (eluting with toluene) and afforded CpNimetallacycles are puckered, and their distorsion angles are given [Ph,PCH2C(0)S] (4.0 8): mp >180 OC; mass spectrum, m / e 382 (M'), IR in Table VI. The Pd-Cl distances (average 2.43 A) are consistent (KBr) u(C0) 1622 (s) cm-'; IH NMR (CD2CI2)6 3.53 (2 H, d, PCH,, 'J(PH) = 10.6 Hz), 5.33 (s, CsHs); "P('HJ NMR (CDzC12) 6 20.6. with a bridging C1 trans with respect to C(17) and C(26). The (28) Reetz, M. T.; Eibach, F. Justus Liebigs Ann. Chem. 1977,242-253. Ph2PCHCOOC2HSbridging unit deserves some comments. The (29) Karsch, H. H. Chem. Ber. 1977, 2213-2221. three P-C(l), P-C(7), and P-C(13) distances are equivalent, and (30) Rathke, J. W.; Muetterties, E. L. J. Am. Chem. SOC.1975, 97, thus no double-bond character is to be found in the P
