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Organometallics 1996, 14, 1522-1524
Photochemical C-Sb Bond Fission in a Palladium-Distibine Complex. Synthesis and Structure of [Pd2@-PhzSbCH@bPhz)2Cl2Ph2] Andrew F. Chiffey, John Evans, William Levason,* and Michael Webster Department of Chemistry, University of Southampton, Southampton SO1 7 l B J , U.K. Received September 8, 1994@ Summary: Photolysis of TPd(Ph2SbCHzSbPh~zCldi n CHzClz generates the dimeric a-phenyl complex [PddpPhzSbCHzSbPh2)zC12Phd. The X-ray structure of the title compound was found to be monoclinic with space grou P21Ia (a = 11.527(8), b = 20.264(5), c = 12.717(4) l / 3 = 112.12(8)”,Z = 2). The data was refined to R = 0.033 on the basis of 3462 reflections (F > 44F)). The dimeric discrete centrosymmetric molecule contains bridging distibine ligands (Pd-Sb 2.560(1), 2.530(1) 4. The square planar geometry at Pd has trans S b donors and trans Cl and phenyl groups. We have recently examined the use of group 16 donor ligands including RSCHzSR and RSeCHzSeR (R= Me or Ph) as building blocks to heterobimetallic comp1exes.l In an extension of this work, we examined similar reactions of [M(PhzSbCH2SbPh2)2ClzI (M = Pd or Pt). These complexes were reported some years ago and, on the basis of conductance and molecular weight data and IR spectroscopy, assigned cis planar structures with qlcoordinated ditertiary stibines.2 In order to confirm that, we attempted to determine the structure of the palladium complex. Vapor diffusion of diethyl ether into a solution of [Pd(PhzSbCH2SbPh2)2C121in CHzCl2 produced a number of small pale yellow crystals over a period of four days, during which the solution was exposed to laboratory sunlight. The structure determination of these crystals revealed a discrete centrosymmetric dimeric molecule [Pdz@-PhzSbCHzSbPh2)2ClzPhzl. The geometry at the palladium is square planar with trans antimony donors and with each ditertiary stibine bridging to two palladium atoms (Figure l, Table l). The two square planar units are aligned parallel (“face-to-face”)to each other and this is clearly shown in Figure 2. The SbPd distances (2.530(1), 2.560(1) A) are similar to those found in palladium(I1)- triphenylantimony complexes3s4 ([Pdz(MeCO2)4(Ph3Sb)212.508(4), [Pd3(MeC02)4(Ph3Sbh,Ph212.473(4),trans-[Pd(Ph3Sb)zInI2.578(1)A). This complex appears to be the first structurally characterized example of this ligand5 and only the second reported structure of a distibine complex;6the majority of structural chemistry involves triphenyl~tibine.~ The
Figure 1. View of the molecule showing the atom numbering scheme. Thermal ellipsoids are drawn at the 50% probability level and hydrogen atoms are omitted for clarity. Primed atoms are symmetry related to unprimed as - x , -y, 1 - z . Table 1. Selected Interatomic Distances (A) and Angles (degY Pd-Sb(1) Pd-Sb(2’) Sb(1)-C(l) Sb(1)-C(l1) Sb(l)-C(21) C(51)-C(52) C(52)-C(53) C(53)-C(54)
2.560(1) 2.530(1) 2.115(6) 2.128(5) 2.132(5) 1.390(8) 1.393(8) 1.370(8)
C-C (phenyl on Sb atoms) Sb(l)-Pd-Sb(2’) Sb( 1)-Pd-CI Sb( 1)-Pd-C(5 1) Pd-Sb(1)-C( 1) Pd-Sb(1)-C(11) Pd-Sb( 1)-C(21) C(l)-Sb(l)-C(ll) C( l)-Sb(l)-C(21) C(ll)-Sb(l)-C(21) Pd-C(51)-C(52) Sb(l)-C(l)-Sb(2)
173.0(1) 94.3(1) 89.2(2) 113.1(1) 122.3(2) 121.1(1) 101.0(2) 99.6(2) 95.7(2) 117.8(4) 115.0(2)
Pd-C1 Pd-C(5 1) Sb(2)-C( 1) Sb(2)-C(31) Sb(2)-C(41) C(54)-C(55) C(55)-C(56) C(56)-C(5 1)
min 1.364(8)
2.411(1) 2.023(5) 2.158(5) 2.128(5) 2.133(5) 1.390(9) 1.395(8) 1.382(7) max 1.403(7)
Sb(2’)-Pd-C1 Sb(2’)-Pd-C(51) C1-Pd-C(51) Pd’-Sb(2)-C(1) Pd’-Sb(2)-C(31) Pd’-Sb(2)-C(41) C(l)-Sb(2)-C(31) C(l)-Sb(2)-C(41) C(31)-Sb(2)-C(41) Pd-C(51)-C(56)
88.5(1) 89.0(2) 170.3(2) 114.7(2) 111.8(1) 123.2(2) 100.1(2) 100.3(2) 103.8(2) 124.1(4)
Abstract published in Advance ACS Abstracts, February 1, 1995. (1)Chiffey, A. F.;Evans, J.;Levason, W.; Webster, M. J.Chem. Soc., C-C-C (phenyl) min 118.1(6) max 121.4(5) Dalton Trans. 1994,2835. transformation: prime (’) -x, -y, 1 z. Symmetry Levason, W.; McAuliffe, C. A. J. Coord. Chem. 1974,4,47. (2) (3)Matthew, M.; Palenik, G. J.; McAuliffe, C. A. Acta Crystallogr. Sect. C 1987,43,21. Pd-C and Pd-C1 distances are unexceptional as is the (4)Barton, D. H. R.; Khamsi, J.; Ozbalik, N.; Reibenspies, J. angle at the methylene atom (Sb(l)-C(l)-Sb(Z)) (115.0Tetrahedron 1990, 46,3111. (2)”);there is no evidence for any interaction between (5) Champness, N. R.; Levason, W. Coord. Chem. Rev. 1994,133, 115. C1 and Pd‘. Inspection of Figure 2 and the angles (6)The other example is [C~{~-C~&(S~M~Z)~}ZC~ZIZ[C~C~~I: Jewiss, around Pd (Table 1)show that the C1 appears to have H. C.; Levason, W.; Spicer, M. D.; Webster, M. Inorg. Chem. 1987,26, 2102. moved away from the nonbonded Pd atom.
0276-733319512314-1522$09.00/0 0 1995 American Chemical Society
Organometallics, Vol. 14, No. 3, 1995 1523
Notes
Table 2. Atomic Coordinates and Isotropic Temperature Factors ( x loJ)
Figure 2. Partial view of the molecule showing the relationship between the two square planar groups. Only the C atoms bonded to Sb are shown. Pd' is related to Pd as - x , -y, 1 - z .
Bulk samples of [Pd2@-Ph2SbCH2SbPh2)2Cl2Ph21were obtained by photolyzing CHzCl2 solutions of [Pd(PhzSbCHzSbPh2)&12] either with a 30 W fluorescent tube (method 2) or simply by exposure to bright sunlight (method 11, as described in the Experimental Section. The lH NMR spectra obtained from the crystals and from the products of both the bulk photolysis routes were identical, and showed only a single methylene resonance a t 2.60 ppm, which may be compared with a value of 2.44 ppm in the starting material. The lH NMR data also show that only a single palladiumcontaining product was formed in all three preparations. During the course of this work both bulk photolysis routes were carried out several times with identical results. The shift to high frequency in d(CH2) is consistent with the change from monodentate to bridging bidentate coordination of the ligand. The a-phenyl group must come from the cleavage of one distibine ligand, but the other products have not been identified. Fragmentation of tertiary stibines, on reaction with metal carbonyls and unsaturated metal centers, is well established and usually indicated by the appearance of black solid^.^ In very few cases have the products been identified. Barton et ~ 2 1structurally .~ characterized the obtained o-Ph-Pd species, [Pds(MeCOz)r(PhsSb)2Phzl, by heating (47 "C) palladium acetate and PhsSb in tetrahydrofuraddioxan, while [Rh(Ph3Sb)s(o-Ph)Cl21 was formed from RhCly3H20 and PhsSb in refluxing ethan01.~The formation of [Pd2@-PhzSbCHzSbPh2)&12Ph2l is the first example of cleavage of a distibine ligand on a metal center and occurs under unusually facile conditions. A solution of [Pd(Ph2SbCH2SbPh2)2C121in CHzClz in a vessel covered with aluminum foil to exclude light was unchanged after several days, proving that the reaction is photochemically induced. ~
~~
(7) Cini, R.; Giorgi, G.;Pasquini, L. Znorg.Chim. Acta 1992,196, 7.
atom
X
Y
Z
u (AZ)"
Pd Sb(1) Sb(2) c1 C(l) C(11) C(12) C(13) C(14) C(15) C(16) C(21) C(22) C(23) C(24) C(25) C(26) C(31) C(32) C(33) C(34) C(35) C(36) C(41) C(42) C(43) C(44) C(45) C(46) C(51) C(52) C(53) C(54) C(55) C(56)
0.13578(4) 0.01266(3) -0.23431(3) 0.13518(13) -0.1823(5) 0.0159(5) -0.0886(5) -0.0794(6) 0.0361(6) 0.1431(6) 0.1340(5) 0.0444(5) -0.0152(5) 0.0034(6) 0.0850(5) 0.1467(5) 0.1273(5) -0.4315(5) -0.4762(5) -0.6037(5) -0.6862(5) -0.6435(5) -0.5173(5) -0.2129(5) -0.1047(6) -0.0843(6) -0.1711(6) -0.2797(7) -0.3001(6) 0.1676(5) 0.2894(5) 0.3167(6) 0.2241(6) 0.1022(6) 0.0749(5)
0.05571(2) 0.15515(2) 0.04554(2) -0.00117(6) 0.1376(2) 0.2484(2) 0.2856(3) 0.3482(3) 0.3753(3) 0.3388(3) 0.2740(3) 0.1931(2) 0.2493(3) 0.2748(3) 0.2423(3) 0.1864(3) 0.1618(2) 0.0478(2) 0.0579(3) 0.0527(3) 0.0381(3) 0.0291(3) 0.0318(3) 0.07 lO(2) 0.0514(3) 0.0732(3) 0.1129(3) 0.1312(3) 0.1 104(3) 0.1053(2) 0.1260(3) 0.1655(3) 0.184(3) 0.1634(3) 0.1233(3)
0.58089(3) 0.47016(3) 0.30367(3) 0.41414(11) 0.3945(4) 0.5482(4) 0.5303(5) 0.5749(5) 0.6370(5) 0.6540(5) 0.6124(5) 0.3269(4) 0.2739(5) 0.1796(5) 0.1400(5) 0.1927(5) 0.2874(5) 0.2601(5) 0.3463(5) 0.3253(6) 0.2169(6) 0.1314(5) 0.1526(5) 0.1492(5) 0.1331(5) 0.0396(5) -0.0404(5) -0.0276(5) 0.0675(5) 0.727l(4) 0.7891(5) 0.8851(5) 0.9216(5) 0.86 12(5) 0.7657(5)
16.8(2) 16.4(2) 16.8(2) 23.8(6) 20.6(25) 16.0(24) 25.1(28) 33.4(32) 33.6(31) 37.5(32) 29.9(30) 18.6(24) 25.8(28) 29.1(29) 25.2(27) 25.6(28) 2 1.6(26) 18.7(25) 27.7(29) 32.6(31) 33.2(31) 32.2(30) 26.5(29) 22.0(26) 33.9(32) 40.8(36) 40.6(35) 37333) 32.4(31) 21.7(26) 29.6(30) 33.0(31) 32.5(31) 35.9(33) 28.0(29)
a Equivalent isotropic temperature factor from anisotropic atom. Phenyl groups are labeled C(1J) where I (1-5) indicates the group and J (1-6) indicates the atoms within one group.
Experimental Section
Physical measurements were made as described previously.' The yellow [Pd(Ph2SbCHzSbPhz)zClz]was prepared as described2 from [PdC1J2- and the ligand in a 1:2 mol ratio in = 27 400 aqueous acetone: yield 45%;E,, 32 000 cm-l mol-l dm3cm-l); v(Pd-Cl) = 297 (sh),278 cm-l, lH NMR (CDzClz relative to TMS) 6(CH2) = 2.44, S(Ph) = 7.0-7.5. Anal. Calcd for CsOH&lzPdSbd: C, 45.9; H, 3.4. Found: C, 45.6; H, 3.4%. [Pdz@-Ph~SbCHzSbPhz)zClzPhz].Solutions of [Pd(PhzSbCH2SbPhz)zClzl (0.04 g, 0.03 mmol) in CHzClz (5 cm3) were photolyzed in two ways. Method 1. The sample in a pyrex flask was exposed t o direct sunlight for a total of 24 h over a period of 3 days. The solution was evaporated to dryness and the residue washed with diethyl ether (5 cm3) and dried thoroughly in uacuo: yield = 20 700 mol-' dm3cm-l); '90% on Pd; E,, 32 100 cm-l v(Pd-Cl) = 271 cm-l; lH NMR (CDZC12 relative to TMS) 6(CHz)= 2.60,6(Ph)= 7.0-7.6. Anal. Calcd for CezHNClzPdzSbr: C, 47.4; H, 3.4. Found: C, 47.9; H, 3.2%. Method 2. A sample in a pyrex vessel was photolyzed for 24 h with a 30 W fluorescent tube, and the product was worked up in the same manner: yield essentially quantitative based on Pd; 'H NMR (CDZC12 relative to TMS) S(CH2)= 2.60,6(Ph) = 7.0-7.6. An identical solution of [Pd(PhzSbCHzSbPhz)zClzl in CHzClz kept in the dark by covering the vessel completely with aluminum foil was unchanged after 3 days. Crystal Growth. A solution of [Pd(PhzSbCHzSbPhz)zCl~l (ca. 0.05 g) in CHzClz(2 cm3)in a small sample tube was placed in a 100 cm3stoppered flask containing 10 cm3of diethyl ether, which was left for 4 days exposed to laboratory sunlight. Crystals grew on the walls of the tube, one of which was used
1524 Organometallics, Vol. 14, No. 3, 1995
Notes
Table 3. Crystal Data for [ P ~ z O ~ - P ~ Z S ~ C H Z S ~ P ~ Z250 ) Z reflections C ~ Z P ~ ~and ~ intensity data for approximately half of mol formula mol wt cryst syst space group a, 8, b, A c, A deg
8
3
v,A3
T, K density (calcd), g
C62Hs4C12PdzSb4 1569.86 monoclinic P2Ja 11.527(8) 20.264(5) 12.717(4) 112.12(8) 2751.8 120 1.895
Z F(OOO), e cryst size, mm type of data collection total no. of observations total no. of unique observations abs cor no. of data used in refinement no. of parameters weighting scheme (w-l)
1,8,(Mo Ka) y,cm-’ max 28, deg S max shift/esd R (F > 4u(F), 3462 refs)” R (all data) wR2 (all data)b
1512 0.24 x 0.20 x 0.14 w
12226 4240 Difabs 4240 317 uZ(Fo2) (O.O368P)* where P = [Max(Fo2,0) 2FC2]/3 0.71069 27.2 50.2 0.98 0.01 0.033 0.045 0.078
+
+
for the X-ray study below: lH NMR (CDZC12) 6(CHz) 2.60,6(Ph) 7.0-7.6. X-ray Structure Determination of [Pda@-Ph2SbCH2SbPh2)&12Ph2]. The air-stable platy rhomb-shaped crystal was mounted on a glass fiber using the oil-film methods and mounted on a n Enraf-Nonius FAST area detector diffractometer. The temperature was maintained at 120 K using a n Oxford Cryostream unit. Cell dimensions were obtained from ( 8 ) Hope, H. Acta Crystallogr. Sect. B 1988, 44, 22.
reciprocal space r e c ~ r d e d .Systematic ~ absences established the space group P21Ia (no. 14) and the direct method in SHEIXS861° yielded the heavy atom positions which were fully consistent with the Patterson function. Repeated structure factor and electron density calculations revealed the C atoms. The H atoms were not convincingly located and were added t o the model in calculated positions. Ten reflections which overflowed the data collection system were omitted from the refinement. The Difabs absorption correctionll was applied to the isotropic model (correction: max 1.10, min 0.91) and full-matrix least-squares12 refinement on F converged satisfactorily. Neutral atom scattering fadors were taken from ref 13 (Pd, Sb) and SHEIXL9312 (Cl, C, H). Diagrams were prepared using ORTEPIP4and PLUT0.15 Additional experimental details are given in Table 3, and Table 2 lists the atomic coordinates.
Acknowledgment. We thank the SERC and B.P. Chemicals Ltd for support (A.F.C.), and Professor M. B. Hursthouse for the X-ray data collection by the SERC X-ray service. Supplementary Material Available: Listings of anisotropic thermal parameters, hydrogen calculated atomic coordinates, and bond distances and angles (4 pages). Ordering information is given on any current masthead page. OM940707S (9)Hursthouse, M. B.; Karaulov, A. I.; Ciechanowicz-Rutkowska, M.; Kolasa, A.; Zankowska-Jasinska, W. Acta Crystullogr. Sect. C 1992, 48, 1257. (10)Sheldrick, G. M. SHELXS86, Program for the Solution of Crystal Structures; University of Gijttingen: Gijttingen, FRG, 1986. (11)Walker, N.; Stuart, D. Acta Crystallogr. Sect. A 1983,39, 158. (12)Sheldrick, G. M. SHELXL93, Program for the Refinement of Crystal Structures; University of Gijttingen: Gijttingen, FRG, 1993. (13) International Tables for X-ray Crystallography; Kynoch: Birmingham, England, 1974; Vol IV. (14) Johnson, C. K. ORTEP-II;Oak Ridge National Laboratory: Oak Ridge, TN, 1976; Report ORNL-5138. (15) Motherwell, W. D. S.; Clegg, W. PLUTO, Program for Plotting Molecular and Crystal Structures; Universities of Cambridge and Gijttingen: Cambridge and Gijttingen, 1978.
