New chiral bidentate nitrogen donor ligands: synthesis of 1,2-diiminophosphoranes and their palladium complexes

C. R. Acad. Sci. Paris, t. 1, SCrie II c, p. 661-666,1998 Synthke organique et organomktallique/Organic and organometallic

synthesis

New chiral bidentate nitrogen donor ligands: synthesis of 1,2=diiminophosphoranes and their palladium complexes Olivier

TARDIF

a, Bruno DONNADIEU

b, Rdgis RFMJ a+

a Organomttalliques et catalyse : chimie et Clectrochimie mokculaires, UMR CNRS-universitk de Rennes 6509, campus de Beaulieu, 35042 Rennes cedex, France ’ Laboratoire de chimie de coordination, 205, roure de Narbonne, 3 1077 Toulouse cedex 4, France (Received 19 June 1998, accepted after revision 21 July 1998)

Abstract

-The reaction of 1,2-diamines la-c with Ph3PBr2 in the presence of triethylamine gives rise to the corresponding diphosphonium salts 2a-c in good yields. Treatment of these salts with NaH at room temper3a-c in near quantitative yields. Derivatives 3a,b react with ature in CH,Cl, affords the diiminophosphoranes complexes 4a,b. The solid state structure of (CH,CN),PdCll giving stable (diiminophosphorane)PdClz complex 4a is described. 0 AcadPmie des sciences/Elsevier, Paris diiminophosphoranes

/ nitrogen

donors / chiral ligands / palladium(I1)

complexes

RCsumC - Nouveaux ligands azotk bidentates chiraux : synthPse de 1,2-diiminophosphoranes de leurs complexes de palladium(ll). Les 1,2-d’ lamines la-c rkagissent avec Ph,PBr, en prkence

et de tritthylamine pour donner respectivement les sels de diphosphonium 2a-c. Uaction B temptrature ambiante de NaH sur ces sels conduit quantitativement aux diiminophosphoranes 3a-c. Les compose% 3a,b rkagissent avec (CH&N),PdClz pour donner les complexes (diiminophosphorane)PdCll 4a,b. La structure de 4a, determinCe par diffraction des rayons X, est pr&entCe. 0 Academic des sciences/Elsevier, Paris

diiminophosphoranes

I ligands azotks / ligands chiraux / complexes de palladium(I1)

Version franqaise abr4gCe Les ligands azotks optiquement actifs jouent un r61e crucial dans le developpement de nouvelles rtactions tnantiostlectives catalyskes par les mktaux de transition [l]. Par exemple, les complexes Pd(II)-bisoxazolines chirales se sont r&Cl& &re de bons catalyseurs pour la copolymtrisation sttreoselective de styrenes substitu& et de CO ou encore la substitution allylique. Afin d’obtenir de nouveaux ligands pour ce type de &actions, nous avons envisagt de synthitiser des l,Zdiiminophosphoranes optiquement actifs B partir de diamines chirales, maintenant facilement accessibles. Nous prksentons ici la prbparation d’une skrie de ces nouveaux ligands ainsi que de leurs complexes de Pd(I1).

Communicated

by Franpis

MATHEY.

* Correspondenceand reprints. 1251-8069/98/00010661

0 AcadCmie

des sciences/Elsevier,

Paris

661

0. Tardif

et al.

Les syntheses ont tout d’abord et& menees avec des melanges ractmiques de diamines afin d’optimiser les conditions operatoires [2]. Les diamines la et 1b rtagissent avec 2 equiv de Ph3PBr2, en presence de triethylamine, pour donner les sels de diphosphonium 2a et 2b, avec des rendements respectifs de 70 et 65 % (schbmti I). Ces sels ont ete caracterises par RMN multinoyaux [3] et spectroscopie de masse FAB haute resolution. La deprotonation est realisee B temperature ambiante, en presence d’un exces de NaH, et conduit aux diiminophosphoranes correspondants 3a et 3b, avec des rendements quasi quantitatifs (schkma I). Cette sequence rtactionnelle a pu etre reproduite dans les memes conditions operatoires B partir des diamines optiquement actives (RR)-la et @,I?)-lc. Durant ces travaux, Reetz et al. ont decrit une synthese identique de deux I ,2-diiminophosphoranes dont le derive (R,R)-3a [4]. Des etudes par diffraction des rayons X ont permis de montrer que le complexe tetraedrique 3a-CoC12 ttait plus proche d’une symetrie C’, que le complexe plan carre Sa-Rh(cod)BF* [4]. De manikre concomitante, nous avons prepare des complexes 1,2-diiminophosphorane-Pd(I1) en vue d’applications en catalyse homogene. Les diiminophosphoranes 3a et 3b reagissent a temperature ambiante avec (CH3CN)2PdCl,, pour donner respectivement les derives 4a (76 %) et 4b (62 %). L’etude par spectroscopic RMN B temperature variable du complexe 4a rtvtle l’existence d’un processus dynamique, mettant probablement en jeu une isomerie conformationneile, pour des temperatures suptrieures a 260 K. A 240 K, les donntes RMN montrent que le complexe ne possttde aucune symetrie. Le derive 4a a et& caracterist par une etude par diffraction des rayons X (&.w I). La g&ometric autour de l’atome de Pd(I1) est approximativement plan carrt et le fragment cyclohexyle pos&de une symttrie locale de type C,. Cependant, l’atome de Pd n’est pas sit& sur cet axe, ce qui entraine une perte de symetrie. Notons que la structure de ce derive du palladium 4a est tres semblable a celle observte pour le complexe de Sa-Rh(1) [4] qui est lui aussi plan carre. En resume, nos travaux associes a ceux de Reetz [4] prouvent que les 1,2-diiminophosphoranes 3 sont aisement accessibles B partir de diamines commerciales, et possedent un potentiel important en tant que ligands pour les metaux de transition. Nous avons montrt qu’ils se cornportent comme des ligands azotes bidentates vis-a-vis du Pd(I1) p our donner des complexes stables. La synthkse de ces complexes du Pd(I1) ouvre la voie B I’obtention de nouveaux catalyseurs pour des reactions de copolymerisation oltfine-CO ou encore de substitution allylique.

1. Results and discussion Chiral nitrogen ligands play a crucial role in the development of novel transition metal-catalyzed enantioselective syntheses [ 11. A recent notable example is the perfectly alternating copolymerisation of substituted styrenes with CO catalyzed by Pd(II)-bisoxazoline complexes to give highly isotactic, optically active copolymers [ 1b-d]. H owever, progress in terms of efficiency and enantioselectivity is still needed for many reactions and this motivates the search for new ligands. Iminophosphoranes (R,P=NR’) are valuable ylides which have found widespread application and have proved to be versatile nitrogen donor ligands for transition metals [2]. They can be easily prepared by deprotonation of aminophosphonium salts (R,P’NHR’) which are themselves readily obtained from R,PBr, and primary amines [2b,e]. Since a number of optically active 1,2diamines

662

are now

accessible,

we have

investi-

gated the synthesis of the corresponding 1,2diiminophosphoranes as potential chiral chelating ligands for palladium-catalyzed reactions [I 1. Herein we report on the synthesis of a series of these new bidentate nitrogen ligands and of the corresponding Pd(I1) complexes. Commercially available racemic mixtures of 1,2-diamines la,b were used initially in order to optimize the reaction conditions. Derivatives la and lb react readily with two equivalents of Ph,PBr,, in the presence of triethylamine at room temperature, to give the corresponding diphosphonium salts 2a (70 % yield) and 2b (65 % yield), respectively (scheme I). The 31P NMR chemical shifts of these derivatives (6: 2a, +37.5; 2b, +37.2 and +38.9) are typical of aminotriarylphosphonium salts [2e, 3a], while the presence of two phosphorus atoms was clearly indicated by the multiplicity of the 13C NMR signals for the NCH moieties [2a: 57.99, dd, /r,c = 2.7 and 10.1 Hz; 2b: 50.14, dd,j,, = 1.8 and 10.3 Hz]. Addition, at room temperature,

1,Zdiiminophosphoranes

R’

NH*

Fl*Y ““NH2

+ 2 Ph3PBr, -

complexes

Et,N

CH2Cb

la-C a : R’ --R* = -(CH2),b:R’ =CH3,R2=H c : R’ = R2 = Ph

and their palladium

2a-c

3a b ,

CJ-4GWdCb

c

Scheme 1.

of an excess of NaH to CH,Cl, solutions of 2a and 2b afforded the corresponding 1,2-diiminophosphoranes 3a and 3b in near quantitative yields. These derivatives were characterized in solution by multinuclear NMR spectroscopy and high resolution FAB mass spectrometry. As expected [3], when compared to the corresponding phosphonium salts, the jlP chemical shifts appeared at lower field (6: 3a, +0.5; 3b, +7.2 and +9.4) and the 13C NMR signals for the were more deshielded (A& 3a/2a, p-cipso I4 ppm; 3b/2b, I2 ppm). Finally, the same stepwise reaction procedure was used employing (R,R)-la and (R,R)-lc to afford the corresponding optically active diphosphonium salts 2a,c and diiminophosphoranes 3a,c. Derivatives 3a (72 % yield) and 3c (66 % yield) exhibited the expected spectroscopic data. During the course of our work, Reetz et al. described an identical synthesis, and structural characterization, of two chiral 1,2-diiminophosphoranes including (R,R)-3a [4]. The coordination behaviour of 3a towards Co(I1) and Rh(1) was also reported in this paper. In line with our aims of developing new palladium-based catalysts, we have prepared Pd(I1) complexes of the 1,2-diiminophosphoranes 3a-b (scheme I). The reaction of derivative 3a with (CHJCN),PdC1, was monitored by 31P NMR spectroscopy in CD,CI,. After a few minutes at room temperature, the signal due to the free diiminophosphorane (-0.8 ppm) had disappeared to be replaced by a very broad signal at +30.5 ppm (V,,2 = 180 Hz). This chemical shift is typical for Pd(II)-coordinated iminophoshoranes [2d]. However, at this temperature, no “C NMR signals could be observed. The fluxional nature of the complex became apparent on cooling the sample down which resulted in the splitting of the broad 3’P NMR signal into two well-resolved lines with a coalescence tempera-

cure of approximately 260 IS. At 240 K, the 31P NMR spectrum consisted of two sharp peaks (+29.5, +32.5) while the 13C NMR spectrum revealed that all the carbon atoms of the cyclohexyl fragment were inequivalent. These data as a whole clearly indicate that, at 240 K, complex 4a possesses no C, symmetry. Single crystals of 4a were grown from a CH,CI,CHCI, mixture at room temperature and subjected to an X-ray diffraction study (&WY I). The complex shows a slightly distorted-square planar geometry around the palladium center [N(l)PdC1(2), 173.1(l)“; N(2)PdCI(l), 167.3(l)“] with the diiminocyclohexane moiety exhibiting local C, symmetry. However, the five-membered metallacycle adopts an envelope conformation [the palladium atom is 1.124 A out of the mean plane defined by the N(l)C(l)C(b)N(2) atoms] with the two phosphorus groups in a mutually &configuration. Overall, it is these structural features which induce a loss of symmetry. It is noteworthy that the solid state structure of Pd-complex 4a is in agreement with the spectroscopic data recorded in solution at 240 K. One point of interest is the structural similarity between the Pd(I1) derivative 4a with that of the 3a-Rh(1) complex [4] which possess the same coordination environment around the metal center. It is very unlikely that the dynamic process taking place in solution at temperatures above 260 K involves the decomplexation of one phosphazene moiety since the 31P NMR chemical shift does not vary dramatically with temperature (A6 - 2 ppm), and remains distinct from that of the free ligand. Thus, it is reasonable to suggest that the observed behavior is due to a facile conformational isomerization involving the cyclohexane ring. This is supported by the absence of any room temperature fluxionality of the corresponding Pd(II)-complex 4b (62 % yield) containing the acyclic ligand 3b.

663

0. Tardif

et al.

Figure 1. Molecular structure of 4a, as determined by a single X-ray diffraction study. Selected bond lengths (A) and angles (“). The phenyl rings have been omitted for clarity.

Figure 1. Structure moltculaire de 4a ttablie par diffraction de rayons X sur monocristal. Les noyaux aromatiques ne sont pas rep&sent& pour plus de clar&. Selection de longueurs (A) et d’angles de liaisons (“): Pd-Cl(l) 2,3l l(l), Pd-Cl(2) 2,294(l), Pd-N(l) 2,056(4), Pd-N(2) 2,071(4), P(l)-N(1) 1,590(4), P(2)-N(2) 1,595(4), N(l)-C(1) 1,448(6), N(2)-C(6) 1,463(6), Cl(l)-Pd-N(1) 96,5(l), Cl(l)-Pd-Cl(2) 90,21(4), C](2)-Pd-N(2) 95,0(l), N(I)-Pd-N(2) 78,0(l), P(l)-N(I)-C(1) 130,3(3), Pd-N(I)-P(1) 129,2(2), Pd-N(l)-C(1) 99,6(3). P(2)-N(2)-C(6) 124,1(3), Pd-N(2)-P(2) 126,0(2), I’d-N(2)-C(6) 108,7(3). 6 carts par rapport au plan moyen : N(l), 0.097; C(l), -0.172; C(6), 0.171; N(2), -0.096.

In summary, works by both our group and that of Reetz [4] highlight the potential of readily prepared chiral 1,2-iminophosphoranes from commercially available diamines. Here, we report that these nitrogen donors act as bidentate ligands towards Pd(I1) giving novel, stable complexes. The ready accessibility of these complexes opens up routes to new catalysts for organic tranformations including olefin-CO copolymerization.

2. Experimental

section

All experiments were performed under an atmosphere of dry argon. ‘H, 31P and 13C NMR spectra were recorded on Bruker AM300 or DPX200 spectrometers. ‘H and 13C chemical shifts are reported in ppm relative to Me&i as external standard. “P down-field shifts are expressed with a positive sign, in ppm, relative to external 85 % H,PO,. High-resolution mass spectra were obtained on a Varian MAT 3 11 or ZabSpec TOF Micromass at CRMPO, Univer-

664

sity of Rennes. Conventional glassware was used. Diamines were obtained from Aldrich Chemical Co. and were used as received. PPhRBr, was prepared according to the literature procedure [2e] using dichloromethane as solvent.

2.1. Preparation

of derivatives 2a-c

Neat trans-1,2-diaminocyclohexane (0.43 mg, 3.6 mmol) was added dropwise to a CH,Cl, solution (15 mL) of Ph,PBr, (3.04 g, 7.2 mmol) and triethylamine (1.10 mL, 8.0 mmol) at room temperature. After 30 min, cold water (10 mL) was added, the organic layer was dried over MgSO, and the solvent was removed under vacuum. The residue was washed with THF (2 x 15 mL). Derivative 2a was obtained as a white solid (2.01 g, 70 % yield). ‘H (CDCl,; 300.133 MHz): 6 0.91 (m, 2H, CHJ, 1.40 (m, 2H, CH,), 1.51 (m, 2H, CH,), 1.93 (m, 2H, CH,), 3.65 (s broad, 2H, NCH), 7.43-8.10 (m, 3OH, CH,,,,), the NH are not observed; ” C (CDCl,; 75.469 MHz):

1,2-diiminophosphoranes

6 24.40

36.11 (s, (s, NCHCHJI-I,), NCHCH,), 57.99 (dd, j,, = 2.7 and 10.1 Hz, NCH), 121.85 (d,j,, = 102.5 Hz, C,), 129.69 (d, j,, = 13.4 Hz, C,,,), 134.41 (d, jpc = 3.1 Hz, C ), 134.56 (d,],, = 11.0 Hz, Corn); “P

(cDd3;

81.019

MHZ):

6 +37.5. I-h-MS

(FAB-mNBA) m/z 7 15.2007 (calculated: 715.2007, M2+ + Br-, 7 %), 318.1414 (calculated: 318.1412, M2+, 100 %). Anal. talc. for C4,H4,N,P,Br2: C, 63.37; H, 5.31; N, 3.52; P, 7.78. Found: C, 63.31; H, 5.41; N, 3.51; P

7.90. The same procedure was used to obtain derivatives (R,R)-2a (2.21 g, 77 % yield), 2b (1.77 g, 65 % yield) and (R,R)-2c (2.35 g, 73 % yield). 2b: ‘H (CD@,; 200.130 MHz): 6 0.87 (d,j,, = 6.2 Hz, 3H, CH,), 3.43 (m, 2H, NCH,), 3.85 (m, II-I, NCH), 7.38-7.89 (m, 30H, CH,,,,,), the NH are not observed. 13C (CDCI,; 50.323 MHz): 6 19.56 (d, j,, = 3.9Hz,CH3),46.86(dd,JPC=2.5and6.0Hz, NCHJ, 50.14 (dd, Jpc = 1.8 and 10.3 Hz, NCH), 120.95 (d,j,, = 102.5 HZ, Ci), 121.57 (d,j,, = 103.7 HZ, Ci), 129.97 (d,j,, = 13.3 Hz, Co,,), 130.08 (d, /&; = 13.3 Hz, C,,,,), 133.87(d,j,,= ll.OHz,C,,), 133.92(d,J,, = 11.3 Hz, C,,), 134.68 (d,j,,= 3.1 Hz, C ), 134.85 (d, /p;: = 2.7 Hz, C,); “P (CDC!,; 81.019 MHz): 6 +37.2, +38.9. HR-MS (FABmNBA) m/z 595.2437 (calculated: 595.2432, M”’ - H’, 100 %), 298.1266 (calculated: 298.1255, M2+, 12 %). 2c: ‘H (CDCl,; 200.130 MHz): 6 4.45 (m, 2H, CH), 7.01-8.01 (m, 40H, CH,,,,), the NH are not observed. 13C (CDCl,; 50.323 MHz): 6 64.62 (dd,j,, = 9.7 and 1.2 Hz, CH), 119.95 (d,J,,,: = 103.2 HZ, Ci), 128.07 (s, C ), 128.47 and 128.79 (s, C,,), 129.69 (d, & = 13.4 Hz, C,,,,), 133.95’(d,j,, = 7.5 Hz, C,,,), 134.91 (d, /~c = 2.4 HZ, C ), 138.80 (s, Ci); “P (CDCl,; 81.019 MH$: 6 +40.21. HR-MS (FAB-mNBA) m/z 733.2901 (calculated: 733.2902, M2+ - H’, 100 %).

2.2. Preparation ranes 3a-c

of 1,.%diiminophospho-

NaH (0.24 g, 10.0 mmol) was added in portions, at room temperature, to a CH,CI, solution (10 mL) of derivative 2a (1 .OO g, 1.25 mmol). The solution was stirred for I h and filtered. The solvent was removed in vacua, and the residue extracted with pentane. Compound 3a [4] was obtained as a moisture sensitive white solid (0.75 g, 95 % yield): ‘H (C,D,;

and their palladium complexes

200.130 MHz): 6 l-42-1.80 (m, 4H, CH,), 2.00-2.31 (m, 4H, CH,), 3.65 (m, lH, NCH), 3.74 (m, IH, NCH), 6.90-7.21 (m, 18H, CH ,,,,.), 7.88-8.03 (m, 12H, CH,,,,); 13C (C,D,; 50.332 MHz): 6 24.99 (s, NCHCH,CH,), 35.05 (s broad, NCHCH,), 61.43 (dd, /PC = 4.9 and 17.2 Hz, NCH), 128.35 (d,j,, = 11.7 Hz, C,,,), 130.65 (d,J,, = 2.5 Hz, C,), 133.42 (d,j,, = 9.8 Hz, C,,,,), 135.53 (d, /PC = 94.4 HZ, Ci); 31P (CDCl,; 81.019 MHz): 6 +0.5 (s). HR-MS (EI, 70eV) mlz 634.2674 (calculated: 634.2666, M’, 30 %). The same procedure was used to obtain derivatives (RR)-3a (0.74 g, 94 % yield), 3b (0.69 g, 92 % yield) and 3c (0.83 g, 90 % yield) which exhibit the following spectroscopic data. 3b: ‘H (CDCI,; 200.130 MHz): 6 1.13 (d,],, = 5.9 Hz, 3H, CH,), 2.90-3.05 (m, lH, NCH), 3.20-3.35 (m, 2H, NCH,), 7.15-7.40 (m, 18H, CH,,,,), 7.47-7.65 (m, 12H, CH aro,nJ 13C (CDCl,; 50.323 MHz): 6 24.38 (d,],,,; = 8.6 Hz, CH,), 54.60 (dd,J,, =4.7and21.5Hz,NCH),56.53(dd,JpC=5.9 and 18.0 Hz, NCH,), 128.10 (d,/,,: = 11.3 Hz, Co,,,), 128.17 (d, jpc = 11.3 Hz, C,,,), 130.83 (d,j,, = 3.1 Hz, C,), 130.89 (d,],, = 3,l Hz, C,), 132.63 (d, & = 9.0 Hz, C,,,,), 132.74 (d,j,>, = 9.0 Hz, C “,“, ), 132.31 (d+ = 94.9 HZ, Ci), 133.07 (d,jPC = 95.1 HZ, Ci); ‘P (CDCI,; 81.019 MHz): 6 +7.2 (s), +9.4 (s). 3c: ‘k (C,D,; 50.323 MHz): 6 69.35 (dd, jr,,; = 3.9 and 20.3 Hz, NCH), 124.85 (s, C ), 126.27 (s, C,,,), 127.95 (d, Jpc = 11.7 I-!,,

Co,,,), 129.51’(s, Co,,), 130.25 (d, jpc = I,1 Hz, C,), 132.79 (d,],, = 9.4 Hz, C,,,), 134.03 (d,jT;(; = 95.5 HZ, Ci), 148.18 (d,j,,

Ci);

= 5.3 HZ,

P (C,D,; 81.019 MHZ): 6 +0.84.

2.3. Preparation complexes Pa, b

ofpalladium

A CH,Cl, solution (10 mL) of racemic derivative 3a (0.48 g; 0.75 mmol) was added at room temperature to a CH,CI, solution of (CH3CN),PdCI, (0.19 g; 0.75 mmol). After 2 h, the solvent was removed under vacuum. The residue was washed with pentane (3 x 10 mL) and with ether (3 x 10 mL). Complex 4a was obtained as’orange crystals from a CH,CI,/ CHCl, solution at room temperature (0.46 g, 76 % yield): ‘H (CD&I,; 200.130 MHz, 240 K): 6 0.10-0.42 (m, 2H, CH,), 0.61-1.60 (m, 6H, CHJ, 2.06 (rn,/&r = 7.6 Hz,],, c: 1 Hz, ‘H, NCH), 4.82 (m, JHH = 11.6 and 7.6 Hz,jpH = 10.4 HZ, lH, NCH), 7.21-8.15 (m,

665

0. Tardif et al. 30H, CH,,,,); 13C (CD&l,; 50.332 MHz, 240 K): 6 24.92, 26.44 (s, NCHCH,CH,), 34.25, 37.61 (s broad, NCHCH,), 67.43 (d, jpc = 5.7, NCH), 72.64 (dd,j,, = 3.4 and 15.6 HZ, NCH), 128.25 (d, Jpc = 100.3 HZ, Ci), 128.94(d,j,,=11.3Hz,C,%,), 133.06(s,C ), 133.64 (d, j,, = 10.7 Hz, Corn); ‘lI’ (CD&P,; 121.496 MHz): 6 (295 K) +30.5 (s broad, v,,~ = 180 Hz), 6 (240 K): 6 +29.5 (s), +32.5 (s). The same procedure was used to obtain derivatives 4b (0.28 g, 62 % yield) which exhibit the following spectroscopic data. 4b: 13C (CD,CI,; 50.323 MHz): 6 23.21 (d,jpC = 1.8 Hz, CH,), 59.25 (dd, Jpc = 1.2 and 14.7 Hz, NCH), 61.85 (dd, /,,c = 2.0 et 12.5 Hz, NCH,), 128.60 (d,j,, = 12.2 Hz, C,,), 128.71 (d,],, = 12.2 Hz, C,,,), 129.11 (d,j,, = 102.3 Hz, C,), 129.33 (d,jpC = 106.6 Hz, C,), 132.56 (d broad,lpc = 2.4 Hz, C ), 134.12 (d,j,, = 9.2 Hz, C,,), 134.31 (d,& = 9.2 Hz, C,,); “I’ (CD&; 81.019 MHz): 6 +32.7 (s),+33.0 (s).

2.4. X-ray structure determination 4a

20(1)) and 493 variables. The calculations were carried out with the aid of the CRYSTALS package programs [5b] running of the PC. The drawing of the molecule was realized with CAMERON [5c] with thermal ellipsoids at the 50 % probability level. The atomic scaterring factors were taken from International tables for X-ray crystallography. Acknowledgements Thanks are due to S. Sinbandhit for helpful discussions and J.J. Brunet and D. Neibecker for their friendly help. Supplementary

material

available

Supplementary material data have been deposited at the Cambridge Crystallographic Data Center, 12 Union Road, Cambridge, CB2 lEZ, UK, as supplementary publication No. SUP 102745 (32 pages) and are available on request from the CCDC.

for References ill (a) Togni A., Venanzi, L.M., Angew. Chem. Int. Ed.

data: C4,H4,N,P,PdC1,-0.5 Crystal CH,Cl,-0.5 CHCl,, M = 893.47, monoclinic, spacegroupP2/c,a= 18.897(2), 6= 11.851(2), and c = 19.509(2) A, p = 99.93(l)", I/ = 4303(l) A3, 2 = 4, F(OO0) = 1822.33, ~(Mo-Ka) = 7.79 cm-‘, DC = 1.38 g cmm3, crystal size 0.37 x 0.25 x 0.15 mm3. There were 30391 total reflexions collected (6779 independent) on a STOE-IPDS diffractometer [MoKa radiation a = 0.71073 A, q-scans, 20 I48.4”]. The stucture was solved by direct methods (SIR92) [5a] and refined by leastsquares procedures on Fobs. H atoms were located on a difference Fourier maps, but they were introduced in calculation in idealized positions (d(C-H) = 0.96 A) and their atomic coordinates were recalculated after each cycle of refinement. They were given isotropic thermal parameters 20 % higher than those of the carbon to which they are attached. All non hydrogen atoms were refined anisotropically. Leastsquares refinements were carried out by minimizing the function xw( [ IF, I- 1F, ) ))2, where F, and F, are the observed and calculated structure. A weighting scheme was used [7]. Model reached convergence with R = C( I I F I

-I&

b/IF

I, Rw = [Ewd IF I-IF

1 Ij%

I F, I)2]q’2. The final R (~w)ovalueCswere 0.0525 (0.0533) for 4788 reflections (I > (CW(

666

Engl. 33 (1994) 497-526; (b) Brookhart M., Wagner M.I., Balavoine G., Ait Haddou H., J. Am. Chem. Sot. 116 (1994) 3641-3642; (c) Brookhart M., Wagner M.I., J. Am. Chem. Sot. 118 (1996) 7219-7220; (d) Abu-Surrah A., Rieger B., Angew. Chem. Int. Ed. Engl. 35 (1996) 2475-2477; (e) Tsuji J., Palladium Reagents and Catalysts, John Wiley and Sons, Baffins Lane, 1995.

PI (a) Gololobov Y.G., Kashukin L.F., Tetrahedron 48 (1992) 1354-1406: (b) Johnson A. W., Kaska W.C., Mides and Imines of Phosphorus, Wiley, New York, 1993; (c) Li J.. Pinkerton A., Finnen D.C., Kummer M., Martin A., Wiesemann E, Cavell R.G., Inorg. Chem. 35 (1996) 5684-5692; (d) Avis M.W., Vrieze K., Ernsting J.M., Else& C.J., Veldman N., Spek A.L., Katri K.V, Barnes C.L., Organometallics 15 (1996) 23762392; (e) Lee K.W., Singer L.A., J. Org. Chem. 25 (1971) 37X0-378 1.

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