Organometallics 1995, 14, 2246-2252
2246
Synthesis, Structure, and Properties of the q2 P-0-C helated Mono(ether- ph0sphine)ruthenium Complex [Cp*Ru(CO)(P-O)I[BPh41 Ekkehard Lindner,” Michael Haustein, Hermann A. Mayer, Karlheinz Gierling, Riad Fawzi, and Manfred Steimann Institut fur Anorganische Chemie der Universitat, A u f der Morgenstelle 18, 0-72076Tubingen, Germany Received September 12, 1994@ The 16-electron complex Cp*RuCl(P-0) (2; Cp* = $-CbMes; P-0 = yl(P)-coordinated ligand) was synthesized by reaction of oligomeric [Cp*RuClzl, (1) with the basic etherphosphine (CsHI1)2PCH2CH20CH3(0,P)in the presence of zinc. Carbonylation of 2 afforded the chloro carbonyl species Cp*RuCl(CO)(P-0) (3),which was converted into the cationic, monochelated compound [Cp*Ru(CO)(P-O)l[BPh4] (4[BPh41; P-0 = y2(0,P)-chelatedligand) by chloride abstraction with NaBPh4. The structure of 4 was elucidated by a single-crystal X-ray structural analysis. 4 crystallizes in the monoclinic space group P2dc with 2 = 4. The cell dimensions are a = 11.739(3) b = 17.620(5) c = 22.919(6) and p = 98.80(2)’. The cleavage of the Ru-0 bond was achieved by 2 bar pressure of carbon monoxide, resulting in the formation of the dicarbonyl complex [Cp*Ru(C0)2(P-O)I[BPh41 (5[BPh41). By treatment of 4 with triphenylphosphine the mixed-phosphine derivative [Cp*Ru(CO)(P-O)(PPh3)][BPh4] (6[BPh4])was formed. A single-crystal X-ray structural determination of 6 shows that it crystallizes in the monoclinic space group Cc with 2 = 4. The cell dimensions are a = 25.683(6) b = 15.496(4) c = 15.653(7) and p = 110.96(3)”.
A,
A,
Introduction The interest in coordinatively unsaturated transitionmetal complexes stems from the fact that they represent very reactive intermediates in catalytically operating processes. The introduction of bifunctional etherphosphines (0,P) instead of “classical” tertiary phosphines has significantly affected the isolation and thus the examination of such undercoordinated species.l These ligands are provided with oxygen atoms incorporated in open-chain or cyclic ether moieties which form a weak metal-oxygen contact while the phosphorus atom is strongly coordinated to the central atom. From this “hemilabile” character, it has been reported that the ether oxygen donor may be regarded as an intramolecular solvent molecule stabilizing the empty coordination site and hence make these complexes much more stable than simple solvent adducts.l In a recent study we investigated half-sandwich cyclopentadienyl- and (pentamethylcyclopentadienyl)ruthenium(11)comple_xes containing monodentate (P-0) and bidentate (P 0 ) et&er-phosphines (P-0 = ql(P)-coordinated ligand; P 0 = q2 (0,P)-chelated ligand) in order to obtain experimental information about the ruthenium-oxygen bond strength in these systems.2 The strength of the metal-oxygen bond is responsible for the ease of the dissociation of the 0 , P chelating ligand and hence for the reactivity of the complex toward an incoming substrate. As one result of these studies we observed a significant decrease of the Ru-0 interaction by replacement of the Cp with the more basic, electron-donating Cp* ligand.2 In addition we determined the different @Abstractpublished in Advance A C S Abstracts, April 15, 1995. (1)Bader, A.; Lindner, E. Coord. Chem. Rev. 1991,108, 27. (2) Lindner, E.; Haustein, M.; Mayer, H. A,; Kiihbauch, H.; Vrieze, K.; de Klerk-Engels, B. Inorg. Chim. Acta 1994,215, 165.
0276-733319512314-2246$09.00/0
A,
A,
A,
A,
chelating abilities of a variety of diphenyl(ether-phosphine) ligands in dependence on the kind of ether moiety, the ring size of the cyclic ethers, and the number and position of the ether atoms in the ring via 31P DNMR spectroscopy and line-shape analyses.2 The last target was now to clear up the influence of the phosphorus basicity on the Ru-0 bond strength in complexes of this type. The use of the basic 0,P ligand Cy2PCH2CH20CH3 has already been reported to be responsible for a weaker metal-oxygen bond in Rh(II1) complexes, compared to the case for the diphenyl analogue^.^ Therefore, the present paper reports the synthesis and structure of the y2(0,P)-chelatedcomplex [C~*RU(CO)(P^O)~[SP~I (4[BPh1; 0,P = Cy2PCH2CH2OCH3). In order t o examine the reactivity of the Ru-0 bond, complex 4 was allowed t o react with carbon monoxide and triphenylphosphine.
Experimental Section General Procedures. All manipulations were carried out under an atmosphere of argon by use of standard Schlenk techniques. Solvents were dried over appropriate reagents and stored under argon. IR data were obtained with a Bruker IFS 48 instrument. FD mass spectra were taken on a Finnigan MAT 711 A instrument (8kV, 60 “C), modified by AMD; FAB mass spectra were recorded on a Finnigan MAT TSQ 70 (10 kV,50 “C). Elemental analyses were performed with a Carlo Erba 1106 analyzer; C1 analyses were carried out according to Schoniger4 and analyzed as described by Dirscherl and Erne.j Ru was determined according to the literature.6 31P(3) Lindner, E.; Wang, Q.;Mayer, H. A.; Fawzi, R.; Steimann, M. Organometallics 1993,12, 1865. (4)(a) Schoniger, W. Microchim. Acta 1955,123.(b) Schoniger, W. Microchim. Acta 1956,869. (5) Dirscherl, A,; Erne, F. Microchim. Acta 1961,866.
0 1995 American Chemical Society
An Ru Mono(ether-phosphine) Complex
Organometallics, Vol. 14, No. 5, 1995 2247
{'H} NMR spectra were measured on a Bruker AC 80 spectrometer operating at 32.44 MHz; the external standard (coaxial insert) at low temperatures (0 to -80 "C) was 1% H3PO4 in acetone-& and above 0 "C was 1% H3P04 in D2O. I3C{'H} NMR spectra were measured on Bruker DRX 250 and Bruker AMX 400 spectrometers at 62.90 and 100.62 MHz, respectively. I3C chemical shifts were measured relative to partially deuterated solvent peaks which are reported relative t o TMS. The 'WIP HETCOR spectrum of compound 6 was recorded on a Bruker AMX 400 spectrometer (400.14 MHz for 'H, 161.98 MHz for 31P)using a standard pulse sequence.' The starting compounds [Cp*RuCl~ln(118and (CsH&PCH2CH2OCH3 (0,P)9 were prepared as described in the literature.
dried in vacuo: yield 711 mg (94%); mp 148-150 "C; MS (FD, 60 "C) m l e 521 [M+ - BPh41. Anal. Calcd (found) for C, 71.50 (71.26); H, 7.68 (7.84); Ru, 12.03 C~OHMBO~PRU: (11.74). IR (KBr,cm-'): v(C0) 1940 (vs). 31P{1H}NMR (32.44 MHz, CH2C12, -30 "C): 6 56.8 (SI. 13C{'H} NMR (100.62 MHz, CD2C12, 22 "C): 6 205.4 (d, J ' pc = 16.5 Hz, CO), 164.6 (q, 'JCB = 48.3 Hz, ipso-C of BPL), 136.5-122.2 (m, CPh), 96.2 ( 6 , C5Me5), 78.5 (s, CHzO), 71.0 (s, OCH3), 38.1, 35.0 (d, lJpc = 26.7 and 19.1 Hz, PCH), 29.7-26.4 (m, CH2 Of CsHii), 22.6 (d, 'JPC = 21.6 Hz, PCHd, 10.9 (s, CsMe5).
Chloro[dicyclohexyl(2-methoxyethyl)phosphine-Pl(pentamethylcyclopentadienyl)ruthenium(I1)(2). To a
mmol) in 10 mL of dichloromethane was treated with carbon monoxide (2 bar) at ambient temperature. The solution turned from yellow to colorless within 30 min. Subsequently the solvent was removed under vacuum. The residue was stirred in 20 mL of n-pentane to give a white air-stable powder, which was collected by filtration (G3) and dried in vacuo: yield 312 mg (100%);mp 206 "C; MS (FD, 60 "C) m l e 549 [M+ - BPh41. Anal. Calcd (found) for C S ~ H S ~ B O ~ P C, R U70.58 : (70.92); H, 7.43 (7.62); Ru, 11.65 (11.38). IR (CH2C12,cm-I): v(C0) 2043 (vs), 1994 (vs). 31P{1H}NMR (32.44 MHz, CH2C12, -30 "C): 6 46.6 (s). 13C{1H}NMR (100.62 MHz, CD2C12,22 "C): 6 199.7 (d, V p c = 15.3 Hz, CO), 164.4 (q, 'JCB = 49.6 Hz, ipso-C of BPL), 136.3-122.0 (m, CPh), 103.1 (s, CsMes),67.9 (s, CHzO), 58.7 (s, OCHs), 38.3 (d, ' J p c = 24.2 Hz, PCH), 29.9-26.1 (m, CH2 of C6Hll), 25.1 (d, l J p c = 26.7 Hz, PCHZ),10.6 (s, csMe5).
solution of [Cp*RuC121n(1; 1.0 g, 3.26 mmol) in toluene (30 mL) were added 836 mg (3.26 mmol) of the ligand (C6H11)ZPCHzCH20CH3 (0,P)and zinc (1.0 g). After it was stirred for 4 h at 60 "C, the dark reaction mixture had turned color t o dark purple. ZnCl2 and excess Zn were separated by filtration (G3). After concentration of the solution under reduced pressure t o -10 mL, the reaction mixture was purified by column chromatography on activated silica gel (length of the column 25 cm). With n-hexaneldiethyl ether (1/1) a dark purple fraction was eluted which contained pure 2. The solvent was removed completely and the residue was dried under vacuum t o give 551 mg (32%) of a dark purple precipitate, which was very air-sensitive: mp 62 "C dec; MS (FAB, 50 "C) m l e 528 [M+]. Anal. Calcd (found) for C25H44ClOPRu: C, 56.86 (56.52); H, 8.40 (8.22); C1, 6.71 (6.67); Ru, 19.14 (18.92). 31P{1H}NMR (32.44 MHz, toluene, -30 "C): 6 36.6 (5). l3C('H} NMR (62.90 MHz, C6D6, 22 "C): 6 75.6 (s, C5Me5), 70.1 (s, CHzO), 59.7 (s, OCH3), 34.2 (d, ' J p c = 18.2 Hz, PCH), 29.6-26.5 (m, CH2 of C6H11), 23.2 (d, ' J p c = 16.4 Hz, PCHz), 11.0 (s, CsMe5).
Carbonylchloro[dicyclohexyl(2-methoxyethy1)phosphine-PI(pentamethylcyclopentadienyl)ruthenium(II) (3). Carbon monoxide was bubbled into a solution of 2 (550 mg, 1.04 mmol) in 20 mL of toluene a t ambient temperature. The solution was stirred for 10 min resulting in a dark yellow color, After concentration of the solution t o -10 mL under reduced pressure, the reaction mixture was purified by column chromatography on activated silica gel (length of the column 20 cm). With n-hexaneldiethyl ether (1l1)a yellow fraction was eluted which contained pure 3. The solvent was removed under vacuum. Compound 3 was obtained as a yellow airstable powder after recrystallization from methanol: yield 486 mg (84%); mp 154 "C; MS (FD, 60 "C) m l e 557 [M+l. Anal. Calcd (found) for C26H44C102PRu: C, 56.16 (55.81); H, 7.98 (8.21); C1, 6.38 (6.65); Ru, 18.17 (17.84). IR (KBr, cm-'): v (CO) 1920 (vs). 31P(1H) NMR (32.44 MHz, CH2C12, -30 "C): 6 38.1 (s). I3C{lH}NMR (100.62 MHz, CDC13,22 "C): 6 207.9 (d, VPc = 20.0 Hz, CO), 95.6 (s, CsMes), 69.1 ( 8 , CH201, 58.3 (s, OCHs), 37.3 (d, l J p c = 22.3 Hz, PCH), 29.7-26.2 (m, CHZ of C&1), 23.6 (d, l J p c = 21.1 Hz, PCHz), 10.1 (s, CsMe5).
Carbonyl[dicyclohexyl(2-methoxyethyl)phosphine-O,Pl(pentamethylcyclopentadieny1)rutheniudII)Tetraphenylborate (4[BPb]). To a solution of 3 (500 mg, 0.90 mmol) in 20 mL of dichloromethane was added NaBPL (308 mg, 0.90 mmol) in one portion. The reaction mixture was stirred for 3 days a t ambient temperature. After removal of the solvent under vacuum the residue was redissolved in 20 mL of dichloromethane. NaCl was separated by filtration (G4). The solvent was again completely removed under vacuum. The residue was stirred in 20 mL of n-pentane to give a yellow air-stable powder, which was collected by filtration (G3) and (6)Lindner, E.; Bader, A.; Mayer, H. A. Z. Anorg. Allg. Chem. 1991, 598/599, 235. (7) Bax, A,; Subramanian, S. J. Magn. Reson. 1986,67, 565. (8)Oshima, N.;Suzuki, H.; Moro-Oka, Y. Chem. Lett. 1984,1161. (9) Lindner, E.; Meyer, S.; Wegner, P.; Karle, B.; Sickinger, A.; Steger, B. J. Organomet. Chem. 1987,335,59.
Dicarbonyl[dicyclohexyl(2-methoxyethyl)phosphineP](pentamethylcyclopentadienyl)ruthenium(II) Tetraphenylborate (5[BPb]). A solution of 4 (300 mg, 0.36
Carbonyl[dicyclohexyl(2-methoxyethy1)phosphine-PI(pentamethylcyclopentadienyl)(triphenylphosphine)ruthenium(I1) Tetraphenylborate (G[BPb]). To a solution of 4 (500 mg, 0.60 mmol) in 20 mL of dichloromethane was added PPh3 (315 mg, 1.20 mmol). The reaction mixture was stirred for 1h a t ambient temperature. Excess PPh3 was separated by column chromatography on activated silica gel (length of the column 20 cm) with diethyl ether as eluent. The pale yellow fraction which contained pure 6 was eluted with dichloromethaneldiethyl ether (1l1)and evaporated to dryness. The residue was stirred in 20 mL of n-pentane to give a pale yellow air-stable powder, which was collected by filtration (G3) and dried in vacuo: yield 602 mg (91%);mp 168-169 "C; MS (FD, 60 "C) m l e 783 [M+ - BPh1. Anal. Calcd (found) for C ~ ~ H ~ ~ B O ~C,P ~74.02 R U :(73.78); H, 7.22 (7.36); Ru, 9.17 (9.39). IR (KBr, cm-I): v(C0) 1939 (vs). 31P{1H}NMR (32.44 MHz, CHC13, 33 "C): 6 47.1 (d, 2 J p p = 26.9 Hz, PPh3), 30.9 (d, 'Jpp = 26.9 Hz, P-0). 13C{1H}NMR (100.62 MHz, CD2C12, 22 "C): 6 209.1 (dd, ' J p c = 17.2 Hz, CO), 164.5 (9, 'JCB = 49.6 Hz, ipso-C of BPL), 136.6-122.0 (m, CPh), 101.3 (s, CsMes), = 22.9 and 68.3 (s, CH20), 58.5 (s, OCHs), 38.4, 37.7 (d, 'JPC 19.1 Hz, PCH), 29.3-26.0 (m, CHZ of C6H11), 24.9 (d, 'JPC = 20.3 Hz, PCHz), 10.9 (s, C a e ~ ) . Crystallographic Analyses. Single crystals of 4 were grown from a 2/1 diethyl etherldichloromethane solvent mixture a t -30 "C. Single crystals of 6 were obtained by slow diffusion of diethyl ether into a concentrated dichloromethane solution a t ambient temperature. Both crystals were mounted on a glass fiber and transferred to a P4 Siemens difbactometer, using graphite-monochromated Mo Ka radiation. The lattice constants were determined with 25 precisely centered highangle reflections and refined by least-squares methods. The final cell parameters and specific data collection parameters for 4 and 6 are summarized in Table 1. Intensities were collected with the w-scan technique with scan speed varying from 8 to 30" min-l in o. Scan ranges for 4 and 6 were 1.5 and 1.0",respectively. All structures were solved by Patterson methods'O and refined by least squares with anisotropic thermal parameters for all non-hydrogen atoms. Hydrogen atoms were included in calculated positions (riding model). Maximum and minimum peaks in the final difference synthe(10) Sheldrick, G.M.SHEIXL 93 program; University of mttingen, Gottingen, Germany, 1993.
2248 Organometallics, Vol. 14, No. 5, 1995
Table 1. Crystal Data and Refinement Details for Compounds 4 and 6 compd formula fw color cryst dimens cryst syst space group
a,A b, A C,
A
A deg
v, A 3
Z
dcaled,
g
T,“C F(OOO),e AMo %I, mm-l 20 limits, deg no. of rflns measd no. of unique data with Z 2 2u(Z) no. of variables
S Rla w R ~ ~ a
4[BPh&H20 6[BPh41 C ~ ~ H ~ ~ B O ~ P CseH79BOzPzRu RU 1102.1 857.9 yellow plates red plates 0.15 x 0.2 x 0.2 0.15 x 0.3 x 0.3 monoclinic monoclinic CC P21lc 11.739(3) 25.683(6) 17.620(5) 15.496(4) 22.919(6) 15.653(7) 110.96(3) 98.80(2) 5817(3) 4685(2) 4 4 1.259 1.216 -100 -100 2328 1816 0.373 0.405 4-50 4-50 16 452 11 761 5511 4231 498 1.28 0.054 0.135
667 1.36 0.038 0.080
R1= XllFol - IFcliEIFol. wR2 = [EMF2- F,2)2MX[W(F2)2110~5.
sis were 2.24 and -1.31 e A-3 (41, and 0.53 and -0.41 e A-3 (61,respectively. The asymmetric unit of compound 4 contains one molecule of H2O. The high maximum peak in the final difference Fourier map of 4 was located around the H2O molecule. Final atomic coordinates are collected in Tables 2 and 3.
Results and Discussion The generation of bidether-phosphine) derivatives Cp*RuCl(P-O)z (P-0 = ql(P)-coordinated diphenyl(ether-phosphine) was achieved by treatment of oligomeric [Cp*RuCl& (1)with an excess of the 0,P ligand in the presence of Zn.2 No evidence for the formation of an analogous 18-electron complex with the basic and large ether-phosphine Cy2PCHzCHzOCH3 was obtained by following the same reaction pathway. Thus, the treatment of 1 with a stoichiometric amount and even with a 2-fold excess of this ligand resulted in the development of a dark purple color of the reaction mixture from which a dark purple precipitate analyzed as the very air-sensitive, 16-electron complex Cp*RuCl(P-0) (2) (Scheme 1)can be isolated. This behavior is obviously due to the steric demand of the 0 , P ligand employed, which is in agreement with reports on the syntheses of mono(phosphine) complexes of the type Cp*RuCl(PR3) (R = Cy, iPr, tBu).11J2 Compound 2 reveals a single peak in the 31P{lH} NMR spectrum a t 36.6 ppm. The 13C NMR resonances of the methylene (dc 70.1) and the methyl group (dc 59.7) of the ether chain in 2 are quite comparable to those observed for Cp*RuCl(CO)(P-O) (3)and are in the typical range of an ql(P)-coordinated 0,P ligand (vide infra). This is surprising, because the coordinativelyunsaturated metal center in 2 would be expected t o allow the bidentate 0,P ligand to chelate, leading to a significant stabilization of the complex. However, the electron-rich ruthenium (11)Arliguie, T.; Border, C.; Chaudret, B.; Devillers, J.; Poilblanc, R. Organometallics 1989, 8, 1308. (12)Campion, B. K.; Heyn, R. H.; Tilley, T. D. J. Chem. Soc., Chem.
Commun. 1988, 278.
Lindner et al.
Table 2. Atomic Coordinates ( x lo4, Esd’s in Parentheses) of 4 with Equivalent Isotropic Displacement Coefficients (kx los)” atom
X
Y
z
1722(1) 2207(1) 227(2) 2349(2) 7669(3) 6459(3) 5969(4) 6009(3) 6538(3) 7029(3) 7012(3) 799x3) 7820(4) 7086(5) 6524(4) 6692(4) 743x31 8927(3) 9519(3) 9610(3) 9100(3) 8506(3) 8395(3) 7297(3) 7429(3) 8147(4) 8713(3) 8568(3) 7858(3) 2274(3) 2187(3) 2324(4) 824(3) 3522(4) 4318(4) 4848(4) 45 17(3) 3724(3) 3193(3) 1778(4) 1359(4) 530(4) 433(3) 841(3) 1686(3) 2354(3) 2230(3) 1427(3) 1061(3) 1632(3) 3099(3) 2815(3) 1023(3) 229(3) 1503(3) 5000 defined as
seems to prevent the contact of a further donor. Attempts t o force the v2(0,P)chelation a t this system via chloride abstraction with NaBPh, failed, resulting in the decomposition of the compound. The corresponding 16-electron complexes provided with “classical”tertiary phosphines have been reported to react with carbon monoxide, leading to stable, 18electron ‘species under mild reaction conditions.11J2 Thus, the treatment of 2 with CO in toluene afforded the yellow air-stable compound Cp*RuCl(CO)(P-0) (3) (Scheme l),which was anticipated t o be a suitable precursor for the generation of an q2(0,P)-coordinated species. The yl(P)-coordinated 0,P ligand in complex
An Ru Mono(ether-phosphine) Complex
Organometallics, Vol. 14, No. 5, 1995 2249
Table 3. Atomic Coordinates ( x 104, Esd's in Parentheses) of 6 with Equivalent Isotropic Displacement Coefficients (A2x lo3)" atom
X
10000(1) 10937(1) 9961(1) 10331(2) 12016(2) 10242(3) 10567(4) 10998(5) 11402(5) 11375(4) 10948(3) 10537(3) 9922(3) 9829(3) 9661(3) 9603(3) 9706(3) 9861(3) 9250(3) 8801(3) 8447(3) 8555(3) 9010(3) 9355(2) 11568(3) 11505(3) 11308(3) 10765(3) 10821(3) 11012(3) 11805(3) 11933(3) 11899(3) 11327(3) 11176(3) 11213(3) 11492(3) 11536(3) 12091(4) 9187(3) 9069(3) 9378(3) 9680(3) 9562(3) 8868(3) 8616(3) 9252(3) 9939(3) 9707(3) 3442(3) 3468(3) 3247(3) 2724(3) 2421(3) 2644(3) 3186(3) 2738(3) 2505(3) 2714(4) 3161(4) 3403(3) 3192(3) 4461(3) 5037(3) 5307(3) 5003(3) 4442(3) 4134(3) 3224(3) 3046(3) 2879(3) 2901(3) 3081(3) 3252(3)
Y
z
8407(1) 8370(1) 6882(1) 8688(3) 7568(3) 8532(4) 6271(6) 5834(8) 5416(8) 5446(7) 5887(5) 6302(5) 5349(4) 4912(5) 5342(5) 6224(5) 6682(5) 6255(4) 6977(5) 6734(5) 6066(5) 5641(5) 5868(5) 6540(5) 7316(4) 6766(5) 7293(5) 7749(5) 8303(5) 7761(4) 9513(4) 10447(5) 11048(5) 10980(4) 10053(4) 9461(4) 7872(5) 8025(5) 7604(6) 9059(5) 8523(4) 8853(4) 9590(4) 9709(4) 9064(5) 7846(6) 8665(4) 10230(4) 10497(5) 12264(5) 10705(4) 9902(5) 9678(4) 10259(4) 11063(4) 11306(4) 12795(5) 13405(6) 14223(6) 14431(6) 13826(5) 12984(5) 12558(4) 12453(5) 12007(5) 11656(5) 11752(5) 12222(4) 11955(5) 12156(6) 12985(6) 13606(5) 13388(5) 12547(4)
0 5U1) 109(2) 2018(3) 2567(3) 1264(4) 1878(6) 2527(8) 2292(10) 1405(10) 738(7) 978(5) -920(5) -1741(6) -2571(6) -2581(5) -1763(4) -938(5) 1115(5) 1355(4) 887(5) 190(5) -39(5) 415(4) -812(5) -1647(5) -2523(5) -2640(4) -1805(4) -933(4) -14(5) -202(5) 546(5) 627(6) 772(5) 7(4) 1032(5) 2018(4) 3522(5) -113(5) -900(5) -1444(5) -981(4) -167(5) 535(6) -1219(6) -2449(4) -1418(5) 450(5) 3820(5) 3124(4) 2777(5) 2746(4) 3056(4) 3394(4) 3449(4) 2198(5) 1498(6) 1575(8) 2351(8) 3046(6) 2994(5) 3698(5) 3991(5) 4777(6) 5267(4) 4966(5) 4177(5) 5349(5) 6066(5) 6158(6) 5521(6) 4807(5) 4696(5)
Equivalent isotropic U,defined as one-third of the trace of the orthogonalized U, tensor. a
Scheme 1
co
l*l+
*l+ 5
6
3 exhibits a single resonance at 38.1 ppm in the 31P{lH} NMR spectrum. One strong IR absorption at 1920 cm-' is observed for the CO ligand. In the l3C(lH} NMR spectrum13of 3 the low-intensity doublet at 207.9 ppm is assigned to the carbonyl group. Moreover, the two singlets a t 69.1 and 58.3 ppm, respectively, are attributed to the two carbon nuclei adjacent t o the ether oxygen atom. The two diastereotopic methine carbon atoms of the cyclohexyl fragments appear as only one doublet due t o the coupling t o the phosphorus atom in the high-field range of the spectrum. Synthesis and Spectroscopic Data of [Cp*Ru(CO)(P-O)I[BPhd (4[BPh&. The intramolecular coordination of the ether function involving the cleavage of the Ru-Cl bond from complex 3 was attempted according to a previously published study.14 However, the quantitative fo-ation of the q2(0,P)-chelatedcomplex [Cp*Ru(CO)(P O)I[BPh41 (4[BPh41) (Scheme 1) was found t o require a prolonged reaction time (3days) compared t o the synthesis of the corresponding bis(phosphine) derivative [Cp*Ru(P-O)(P O)I[BPhI (0,P = (1.3-dioxan-2-ylmethyl)diphenylphosphine~.14 This (13)The assignment of the 13C NMR resonances was supported by 135 NMR spectroscopy: Gunther, H.NMR-Spektroskopie;
13C DEFT
Thieme Verlag: Stuttgart, Germany, 1992. (14)Lindner, E.; Haustein, M.; Mayer, H. A.; Schneller, T.; Fawzi, R.;Steimann, M.Inorg. Chim. Acta 1996,231, 201.
2250 Organometallics, Vol. 14,No. 5, 1995 c49
Q
Lindner et al. C 48
c44
c43
c37
w
L.51
Figure 1. ORTEP plot of 4. indicates a strong Ru-C1 bond in complex 3. Complex 4, which represents an y2(0,P)-coordinatedmono(etherphosphine) ruthenium complex, was obtained as a yellow air-stable powder in 94% isolated yield. Its 31P{'H} NMR spectrum displays a single peak at 56.8 ppm which is shifted (Ad -19 ppm) to lower field due to the ring contribution A R . ' ~Due t o the y2(0,P)-coordination of the ligand the 13C NMR resonances13 of the two carbon atoms of the ether moiety in positions a to the oxygen are also significantly shifted to lower field (-9 ppm (CH20), -13 ppm (OCH3))compared to the corresponding signals of the V'(P)-coordinated ether moiety in 3. Moreover, the two inequivalent methine carbon atoms of the two cyclohexyl groups reveal two doublets (dc 38.1 and 35.0, 'Jpc = 26.7 and 19.1 Hz)which are caused by their different positions above and below the five-membered chelate ring. The CO ligand in 4 appears as a low-intensity doublet at 205.4 ppm C2Jpc = 16.5 Hz). In the IR spectrum the CO stretching frequency at 1940 cm-l is shifted 20 cm-l to higher wavelengths relative t o the neutral species 3, demonstrating the decreased electron density at the ruthenium center. Crystal Structure of 4. A single-crystal X-ray determination of 4 was undertaken to determine the coordination geometry about ruthenium. The ORTEP drawing of the cation of 4 is shown in Figure 1. A listing of selected bond distances and angles is given in Table 4. The environment about the Ru atom corresponds t o that of a three-legged piano stool with near 90' angles between P(l)-Ru(l)-C(28) and C(28)-Ru(l)-O(1). However, the O(l)-Ru(l)-P(l) angle (75.35(9)') of the q2(0,P)-coordinated ligand is significantly smaller but is comparable with_the corresponding angle reported for [Cp*Ru(P-O)(P O)][BPh4], 77.2 @)'.I4 The five-membered chelate ring consists of two planes, which are determined by the atoms P(U, C(25), C(26), O(1) and P(1), Ru(l), O(1). These planes form an angle of 143.5' at their common edge, which is defined by P(1)and 0(1), (15)Garrou, P. E. Chem. Reu. 1981,81,229.
Table 4. Selected Interatomic Distances (A)and Angles (deg) for 4 Ru(l)-P( 1) Ru(1)-0(1) Ru(l)-C(28) C(28)-0(2)
Bond Lengths 2.349(1) P(l)-C(25) 2.231(3) C(25)-C(26) 1.861(5) C(26)-0(1) 1.155(6) 0(1)-C(27)
Bond Angles P(l)-Ru(l)-C(28) 91.9(1) Ru(l)-P(l)-C(25) C(28)-R~(l)-O(l) 91.2(2) P(l)-C(25)-C(26) O(l)-Ru(l)-P(l) 75.35(9) C(25)-C(26)-0(1) R~(l)-C(28)-0(2) 172.0(4) C(26)-0(1)-Ru(l)
1.840(5) 1.512(7) 1.457(6) 1.436(6) 103.4(2) 112.9(3) 110.0(4) 114.5(3)
giving an envelope conformation with Ru(1) at the top. The Ru-C-0 unit deviates from the expected linear geometry, forming an angle of 172.0(4)". The rutheis nium-oxygen distance (Ru(1)-O(1) = 2.231(3) slightly shorter relative to that of [Cp*Ru(P-O)(P 011rBPhd(2.262 (6) A), which is indicative of an increased Ru-0 bond strength.
4)
Reactivity of 4 toward Carbon Monoxide and Triphenylphosphine. The strength of the Ru-0 bond and hence the chelating ability of an y2(0,P)-coordinating ether-phosphine ligand is of interest with regard to the easy dissociation and protective effect of the functional oxygen. In complexes with at least two "hemilabile"ether-phosphine ligands the oxygen donors compete for one coordination site. This reveals a fluxional behavior in solution which can be studied by variable-temperature 31PNMR spectroscopy. Therefore, the determination of the Ru-0 bond strength in complexes of the type [Cp*Ru(P-O)(P-O)l+ (0,P = diphenyKether-phosphine)) was achieved by evaluation of the thermodynamic data based on line-shape analyses.2 An alternative route to give a qualitative estimation of the chelating properties of bifunctional 0 , P ligands is to study the reactivity of such complexes toward incoming substrates. Hence, we reported the use of [Cp*Ru(P-O)(P-O)I[BPh41 (0,P = (1,3-dioxan-2-ylmethyl)diphenylphosphine) as a reactive precursor for the
An Ru Mono(ether-phosphine) Complex
Organometallics, Vol. 14, No. 5, 1995 2251 C66
C52
C40
C30
C29
C27 C28
&3
C58
Figure 2. ORTEP plot of 6. coordination of a variety of small molecules.16 In the case of the q2(0,P)-chelated mono(ether-phosphine) complex 4 information concerning the strength of the Ru-0 bond can be obtained by investigations of the reactivity of 4 toward simple molecules such as carbon monoxide and triphenylphosphine. If carbon monoxide is bubbled into a solution of 4 in dichloromethane a t ambient temperature, only slight conversion is observed after 10 min. This is in marked contrast t o the fast coordination of CO to the corresponding bidphosphine) derivative.2 However, treatment of 4 with CO under forced reaction conditions (2 bar) resulted in the quantitative formation of the dicarbonyl species 5 (Scheme 1)within 30 min. The reaction was monitored by the appearance of a single peak a t 46.6 ppm in the 31P{1H} NMR spectrum. Complex 5 is an air-stable white powder; the two CO stretching frequencies are observed a t 2043 and 1994 cm-', respectively, in the IR spectrum. The two equivalent carbon monoxide ligands reveal a low-intensity doublet at 199.7 ppm PJpc = 15.3 Hz) in the l3C{lH) NMR spectrum. Moreover, the single resonances of the methylene (Bc 67.9) and the methyl (Bc 58.7) carbon atoms of the ether moiety are in the range of the corresponding signals of compounds 2 and 3, respectively, indicating the ql(P)coordination of the 0,P ligand in complex 5 . The addition of a 2-fold excess of triphenylphosphine to a solution of 4 in dichloromethane a t ambient temperature is accompanied by a continuous color change from bright yellow to pale yellow. The complete conversion into the new complex [Cp*Ru(CO)(P-0)(PPh,)l[BPhd (6[BPLI) (Scheme 1)required approximately 60 min. Compound 6 was obtained as a pale yellow air-stable powder after separation of excess PPh3 via column chromatography in 91% yield and represents an example for a mixed-phosphine complex. Its 31P{1H} NMR spectrum at 33 'C displays an AB pattern caused (16)Lindner, E.; Haustein, M.; Fawzi, R.; Steimann, M.; Wegner,
P.Organometallics 1994,13, 5021.
by PPh3 (Bp 47.1, 2 J p p = 26.9 Hz) and the 0,P ligand (BP 30.9, 2 J ~ = p 26.9 Hz). The assignment of the two phosphorus nuclei was supported by a 'WIP HETCOR spectrum7 at room temperature. At -30 "C the doublet due t o the phosphorus atom of the 0,P ligand is broadened. Further cooling t o -80 "C gives rise t o two doublets of different intensities. The signal which is assigned t o the PPh3 ligand remains sharp in the whole temperature range. This dynamic phenomenon is consistent with a restricted Ru-P rotation which was also observed in Cp*Ru(P-0)2 systems provided with sterically encumbering ancillary ligands such as chlorine2 or ethene.16 Therefore, no further investigations were carried out concerning the observed decoalescence in the present case. The fact that only the rotation around the metal-(ether-phosphine) bond axis can be frozen at -80 "C is reasonable with regard to the increased steric constraint of the Cy2PCHzCH20CH3 ligand relative to PPh3. The coordinated carbon monoxide in 6 reveals a strong absorption at 1939 cm-l in the IR spectrum and a low-intensity doublet of doublets (dc 209.1, ?-Jpc = 17.2 Hz) due to the coupling with two inequivalent phosphines in the 13C{'H} NMR spectrum. The two single peaks at 68.3 and 58.5 ppm are respectively assigned t o the methylene and methyl carbon atoms of the ether chain and are in the typical range observed for ql(P) coordination (vide supra). The two diastereotopic methine carbon atoms of the cyclohexyl fragments of 6 display two resonances (6c 38.4 and 37.7, 'Jpc = 22.9 and 19.1 Hz). To determine the coordination geometry about ruthenium and t o get an impression of the sterically encumbered ruthenium center, a single-crystal X-ray determination of 6 was carried out. The ORTEP drawing of the cation of 6 is shown in Figure 2. A listing of selected bond distances and angles is presented in Table 5. The geometry of 6 is octahedral about the metal center, with the Cp* occupying three coordination sites. This is evidenced by the near-90' angles between P(l)-Ru(l)P(2), P(l)-Ru(l)-C(25), and P(2)-Ru( 1)-C(25), respec-
2252 Organometallics, Vol. 14,No. 5, 1995
Lindner et al.
Table 5. Selected Interatomic Distances (A)and Angles (deg) for 6 Bond Lengths 2.379(2) P(l)-C(56) 2.373(2) C(56)-C(57) 1.860(6) C(57)-0(2) 1.144(7) 0(2)-C(58) P(1)-Ru( 1)-P(2) P(l)-Ru(l)-C(25) P(2)-Ru(l)-C(25) Ru(l)-C(25)-0(1)
Bond Angles 92.44(7) Ru(l)-P(l)-C(56) 91.0(2) P(l)-C(56)-C(57) 92.0(2) C(56)-C(57)-0(2) 170.5(6) C(57)-0(2)-C(58)
1.849(7) 1.525(9) 1.415(7) 1.438(8) 120.5(2) 122.1(5) 105.7(5) 112.2(5)
tively. The distances between ruthenium and each of the two different phosphorus atoms are nearly equivalent (Ru(l)-P(l) = 2.379(2) A,Ru(l)-P(2) = 2.373(2) A) and only slightly longer compared with the Ru-P bond length in 4 (2.349(1) A). The coordination geometry of the Ru-C-0 unit is in good agreement with that of compound 4. The CO bond lengths as well as the IR data for both complexes are comparable, indicating almost the same back-donation from the metal to the carbonyl ligand and hence a similar electron density at both ruthenium centers.
Conclusion The employment of the basic 0,P ligand CyzPCHzCH20CH3 in the synthesis of (ether-phosphine)(pentamethylcyclopentadieny1)ruthenium complexes was taken into consideration with the intention of creating an electron-rich ruthenium center relative to the corresponding diphenyKether-phosphine) derivatives. Therefore, a very weak Ru-0 contact was anticipated if the 0,P ligand is allowed to function as a bidentate
chelate. The steric constraint of this ligand reveals the formation of the 16-electron mono(ether-phosphine) complex 2. A potential v2(0,P)chelation in this compound is prevented, which is attributed to the increased electron density at the ruthenium. However, the stabilization of the coordinatively unsaturated metal center with carbon monoxide has led to a valuable precursor for the generation of the y2(0,P)-chelatedmono(etherphosphine) complex 4. The cleavage of the Ru-0 bond in 4 was achieved by treatment of 4 with carbon monoxide and triphenylphosphine. In the case of the latter the sterically encumbering mixed-phosphine complex 6 was obtained. In general, however, the reactivity of 4 toward an incoming substrate is slowed down compared t o the analogous bidether-phosphine) systems. This is further evidence for the increased metaloxygen contact in 4 beside the shortened Ru-0 bond length and is equivalent to a reduced electron density at the metal. These results may be best interpreted with a compensation of the electronically enriched ruthenium (caused by the basic 0,P ligand employed) by the electron-withdrawingeffect of the carbonyl group.
Acknowledgment. The support of this research by the Fonds der Chemischen Industrie is gratefully acknowledged. We thank the BASF Aktiengesellschaft for starting materials. Supplementary Material Available: Tables of crystal data and refinement details, hydrogen atom positional parameters, anisotropic thermal parameters, and interatomic distances and angles for 4 and 6 (14 pages). Ordering information is given on any current masthead page. OM940712W
