Organometallics 1995, 14, 4983-4985
4983
Mono- and Binuclear Rhodium Complexes of a Chiral 1,l-Diphosphine. Syntheses and Crystal Structures Angela Marinetti," Claude Le Menn, and Louis Ricard Laboratoire "Hktkroklkmentset Coordination", URA CNRS 1499, DCPH, Ecole Polytechnique, 91128 Palaiseau Cedex, France Received August 2, 1995@ Summary: The homochiral diphosphine 3, bearing PPhz and menthylphosphetane moieties, has been prepared fiom the phosphetane oxide 1 through a stereoselective phosphorylation reaction. Monometallic and bimetallic "A-frame"rhodium complexes of 3 have been synthesized and characterized by X-ray diffraction.
step synthesis from the optically pure P-menthylphosphetane oxide 1.6 1. nBuLi, -78"C,THF c
2. Ph*P(O)CI, -78.0"C 3. HCI 3N
Men/'+
Bis(dipheny1phosphino)methane (dppm) and analog ous 1,l-diphosphines hold a special place in organometallic chemistry, owing t o their ability to assemble unusual mono- and bimetallic complexes. The monometallic species I have a strained' fourmembered-ring chelated structure. The abnormally small P-M-P bite angle and the concomitant anomalous structure of the valence orbitals confer an improved reactivity on the metal center in such complexes. Thus, 14-electronintermediates I, with [MI = Ni, Pd, Pt,RhC1, are high-energy fragments2 displaying various intermolecular bond activation reactions as well as interesting catalytic properties.3
I
1 P(R) Men-P = I menthyl-P
-
Men +!,
-HSiCIB/ Et+
toluene reflux, 16h
II
In the binuclear complexes4 11, the two metals are kept in close proximity and are able to react cooperatively with substrate molecules in stoichiometric or catalytic s y ~ t e m s . ~ *Remarkable ,~ results in hydroformylation reactions have been reported recently.5c Hundreds of papers on 1,l-diphosphine-transitionmetal complexes have appeared over the last 20 years. Nevertheless, as far as we know, no chiral optically pure 1,l-diphosphines have been used as ligands for the synthesis of mononuclear or binuclear complexes. We report here the synthesis of the new chiral 1,ldiphosphine 3 and the syntheses and X-ray structures of the two rhodium complexes 4 and 5, in which 3 acts as a chelating and a bridging ligand, respectively. The phosphine 3 has been prepared through a twoAbstract published in Advance ACS Abstracts, October 15,1995. (1)Li, C.; Cucullu, M. E.; McIntyre, R. A.; Stevens, E. D.; Nolan, S. P. Organometallics 1994,13, 3621. (2)(a) Hofmann, P.; Perez-Moya, L. A.; Krause, M. E.; Kumberger, 0.;Muller, G. 2. Naturforsch., B 19w),45,897.(b)Hofmann, P.; Heiss, H.; Muller, G. 2. Naturforsch., E 1987,42,395.(c)Hofmann, P.; Meier, C.; Englert, U.; Schmidt, M. U. Chem. Ber. 1992,125, 353. (3)See for example: (a) Hofmann, P.; Unfried, G. Chem. Ber. 1992, 125, 659. (b) Hofmann, P.; Meier, C.; Hiller, W . ;Heckel, M.; Riede, J . ; Schmidt, M. U. J . Organomet. Chem. 1995,490,51and references therein. (4)(a) Chaudret, B.; Delavaux, B.; Poilblanc, R. Coord. Chem. Rev. 1988,86, 191. (b)Anderson, G.K. Adu. Organomet. Chem. 1993,35, @
1.
(5)(a) Kubiak, C. P.; Eisenberg, R. J. Am. Chem. Soc. 1980,102, 3637. (b) Kubiak, C. P.; Woodcock, C.; Eisenberg, R. Znorg. Chem. 1982,21, 2119. (c) Broussard, M. E.; Juma, B.; Train, S. G.; Peng, W.-J.;Laneman, S. A.; Stanley, G. G. Science 1993,260, 1784.
Metalation of 1 with nBuLi, followed by treatment with 1 equiv of diphenylphosphinyl chloride, afforded the dioxide 27(eq 1)in about 50%yield after purification by column chromatography as a single isomer. On the basis of previous results concerning the a-alkylation6g8 of the same phosphetane oxide 1,the Ph2P(O) substituent is expected to occupy an equatorial position, anti with respect t o the menthyl group. The assumed stereochemistry for 2 has been confirmed by the X-ray (6)Marinetti, A.;Ricard, L. Tetrahedron 1993,49,10291. (7) nButyllithium (1.2mL, 1.6M solution in hexane) was added to a solution of phosphetane oxide 1 (500mg, 1.8mmol) in THF (25mL) a t -78 "C. After a few minutes, 1 equiv of PhZP(0)Cl was added. The reaction mixture was warmed slowly to 0 "Cand hydrolyzed with 3 N HCl (1 mL). After extraction with ether, the organic phase was chromatographed on a silica gel column with an ether-methanol gradient. The final product was eluted with ether-methanol (9O:lO): yield 0.4 g (48%);colorless solid. Selected data for 2 are as follows. Anal. Calcd for CZ~H~ZPZOZ: C, 71.88;H, 8.74. Found: C, 70.55;H, 8.44. 31PNMR (81MHz, C6D6): 6 64.6and 25.7( V p - p = 17.1Hz). 'H NMR (200 MHz, C&): 6 0.51 (d, 3 J ~=- 6.3 ~ Hz, CHMe), 0.68 (d, 35H-H = 6.8 Hz, 3H,CHMeZ),0.84 (d, 3 J ~ - p= 19.1 Hz, 3H, PCMeZ), 1.03(d, '5H-H = 6.7Hz, 3H, CHMeZ), 1.13(s, 3H, CMeZ), 1.27 ( 8 , 3H, CMeZ), 1.34(d, 3JH-p = 16.9 Hz, 3H,PCMeZ), 3.27 (dd, 2 J ~ - p= 15.9 Hz, 2 J ~ - p= 11.9 Hz, PCHP), 7.1,8.0,and 8.6 (m, Ph). 13C NMR (50 MHz, C&): 6 17.4(Me), 18.4(broad s,Me), 21.4 (Me), 22.0(Me), 22.7 (Me), 23.3 (t, J c - p = 7.0Hz, Me), 24.5 (d, J c - p = 11.5 Hz, CHd, 29.0 (dd, V - p = 9.2Hz, J c - p = 2.9 Hz, Me), 30.6 (d, Jc-p = 2.5 Hz, CHI, 33.0(d, J c - p = 12.4Hz, CH), 32.8 (CHZ),34.6(d, Jc-p = 2.2Hz, CHz), 41.5 (dd, V c - p = 9.2Hz, ZJ~-p = 4.6 Hz, CMe21, 41.7(d, UC-P= 43.8 Hz, PCH), 41.9 (CHI, 51.2 (dd, V - p = 57.4 Hz, 3 J c - p = 10.4 Hz, PCMeZ), 55.1 (dd, l J ~ - p= 60.5Hz, U - p = 34.8Hz, PCHP). MS(E1): d e 484 (M, 50%), 201 (PhZPO, loo%), [al~ = -141 (c = 1, CHC13). (8)Marinetti, A.; Ricard, L. Organometallics 1994,13, 3956.
Q276-7333/95/2314-4983$Q9.QQ/Q 0 1995 American Chemical Society
Communications
4984 Organometallics, Vol. 14,No. 11, 1995 structure determinations reported hereafter. The syn orientation of the PhzP(0) substituent with respect to the P=O bond, and hence the phosphetane phosphorus lone pair, is required to furnish a potential chelating diphosphine. Reduction of 2 (eq 2) was performed with an excess (10 equiv) of HSiC13/Et3N, in toluene at 110 "C in a sealed glass ampule. The conversion is quantitative according to 31PNMR analysis of the reaction mixture. After hydrolysis with 20% NaOH, the final diphosphine 39 was purified by filtration of the organic phase over an alumina column with hexane-ether (9O:lO) as eluent. The reduction proceeds with total retention of configuration of the phosphetane phosphorus atom. Diphosphine 3 is slightly air sensitive, and it must be handled under an inert atmosphere. In the next step of our work, we examined the coordinating properties of 3 toward rhodium(1) derivatives, as an exploratory study preceding the use of this ligand in conventional asymmetric catalytic reactions. The synthesis of homochiral 1,l-diphosphines, as well as the catalytic properties of the corresponding transition-metal complexes, has been barely mentioned in the 1iterature;lO therefore, their potential has not been clearly established at present. The diphosphine 3 reacts easily at room temperature with the cationic rhodium complex (COD)zRh+PFs- to afford the chelated complex 411 as an orange solid (eq 3). Formation of the four-membered Rh-P-C-P ring PPho
r
Ph2
1+
4
of 4 is shown by the 31PN M R chemical shifts a t high field with respect to the starting phosphine: 6 (CDCl3) 'Jp-p 4.2 ( l J p - ~= 121Hz)and -37.3 ( l J p - a = 126 Hz), = 62 Hz. The lH and 13C NMR spectra of 4 are poorly resolved, due to the low solubility of 4 in CDCla and the number of coupling constants to rhodium and phosphorus atoms; nevertheless, the signals of the COD (13C NMR: triplets at 89.0, 94.7, 95.2, and 97.7 ppm) and phosphetane ligands are observed. Crystals of 4, suitable for an X-ray structure determination,12 could be grown from a CHzClz solution by slow addition of an ether-hexane mixture. The molec-
C15
C14 c9 r79
\ '
C16
c19
:3 1
Figure 1. Crystal structure of complex 4. Selected bond distances (A) and angles (deg): Rh-P(l), 2.364(2); RhP(5), 2.309(2); P(5)-C(4), 1.827(7); P(1)-C(4), 1.873(8); P(l)-C(2), 1.898(7),C(2)-C(3), 1.56(1);C(4)-C(3), 1.60(1); Rh-C(39), 2.201(8);Rh-C(32), 2.225(8);Rh-C(35), 2.185(9); Rh-C(36), 2.194(8); P(l)-Rh-P(B), 70.99(6); Rh-P(l)C(4),92.2(2);P(l)-C(4)-P(5), 94.3(3);C(4)-P(5)-Rh, 95.2(2); C(2)-P(l)-C(4), 78.3(3); P(l)-C(4)-C(3), 87.7(5); C(4)C(3)-C(2), 97.9(5);C(3)-C(2)-P(l), 88.1(4). ular structure of 4 and the main bond distances and angles are given in Figure 1. The most unique feature of complex 4 is the bicyclic structure formed by two fused four-memberedrings, one of them containing the metal and the two phosphorus atoms. As a result, the ligand frame and its connection to the metal are conformationally fully fixed. A noteworthy structural parameter is the bond angle P(1)Rh-P(5) of 70.99(6)",which is significantly smaller than the corresponding P-M-P angles (ca. 75°)2c,3bin all other known 1,l-diphosphine complexes. As it appears that the P-M-P angle strain is responsible for the high reactivity of 14-electron metal fragments toward oxidative-addition processes? we can expect an improved activity when 2-phosphinophosphetanes,such as 3, are used as ligands in such complexes. The potential
(11)A 90 mg amount of phosphine 3 (0.2mmol) was reacted with 0.2mmol of (COD)2RhfPF6- in 2 mL of CHzCl2 at room temperature for a few minutes. The reaction was quantitative according to 3lP NMR analysis of the mixture. The solvent was partially removed. Orange crystals separated after addition of ether to the CHzClz solution. (9)Diphosphine 3 (240 mg, 85% yield) is obtained, as a colorless Cooling at -20 "C overnight afforded 95 mg of 4 (60%). Complex 4: solid, from 300 mg of 2. Selected data for 3 are as follows. 31P NMR Anal. Calcd for C ~ ~ H U F ~C,P54.96; ~ R ~H, 6.73. Found: C, 54.38; (CtjDs): 6 24.4and -18.6 ('Jp-p = 87.0Hz). 'H NMR (c&): 6 -0.63 H, 6.59. ID = -194 (C = 1, CHCls). (qd, J = 13 Hz, J = 4.5 Hz, lH, PCHCHz), 0.61 (d, 3 J ~=- 6.4 ~ Hz, (12)Crystal data for complex 4: C ~ , H S ~ F ~ PCH2C12; ~ R ~ . ~space / CHMe), 0.71 (d, 3 J H - H = 6.8 Hz, 3H,CHMeZ), 0.86 ( 8 , Me), 0.97 (d, 35H-H = 6.8 Hz, 3H,CHMeZ), 1.13 (d, 'JH-p = 17.1 Hz, 3H,PCMeZ), A, b = 27.952(1) c = 11.318(2) oup P212121 (No. 18). a = 25.47~42) 1.16(d, 3&-p = 4.0Hz, 3H,PCMeZ), 1.54(d, 4 J ~ - p= 2.5Hz, 3H, CMeZ), V = 8058.96(1.04)A3, 2 = 8;deald= 1.403g/cm3. Crystals contain 2.24(m,1H,CHMe2),3.15(dd,2J~-p=5.1H~,2J~-p=2.6Hz,PCHP), two identical molecules in the asymmetric unit. Data were collected at -150 0.5 "C on a n Enraf-Nonius CAD4 diffractometer using Mo 7.0and 7.6 (m, Ph). 13C NMR (CtjDe): tentative assignment d 16.2 K a radiation ( A = 0.71073 A) and a graphite monochromator. The (Me), 22.4(Me), 22.6 (d, J c - p = 4.5Hz, Me), 22.7(Me), 24.8(dd, Jc-p crystal structure was solved and refined using the Enraf-Nonius = 25.7,J c - p = 3.2 Hz, Me), 25.4 (d, J c - p = 9.3 Hz, CHz), 25.5 (dd, MOLEN package. The SIR92 direct methods suite yielded a solution J c - p = 23.9,J c - p = 7.1 Hz, Me), 26.9(d, J c - p = 4.4 Hz, Me), 29.1 (d, for all atoms. Anisotropic temperature factors were used for all nonJ c - p = 20.0Hz, CH), 33.8(d, J c - p = 3.0Hz, CH), 34.7(CHg), 34.8(dd, hydrogen atoms in the final stages of least-squares refinement, and a ' J c - p = 36.5 Hz, 3 J c - p = 2.9 Hz, PCH), 37.3 (dd, J c - p = 16.7,J c - p = non-Poisson weighting scheme was applied with a p factor equal to 3.2CMeZ), 37.6(CHz), 38.4(dd, V c - p = 26.9,lJc-p = 12.6Hz, PCHP), 0.08.The hydrogen atoms were included as fixed contributions in the 44.4(dd, J c - p = 10.7, J c - p = 2.9,CMeZ), 47.8 (d, VC-P= 24.5 Hz, final least-squares cycles: number of observed reflections 7496;final CH). MS(E1): m/e 452 (M, 25%), 183 (Men PCH, 100%). R = 0.048. (10)Brunner, H.; Fiirst, J. Tetrahedron 1994,50,4303.
x
1,
*
Communications
Organometallics, Vol. 14, No. 11, 1995 4985
applicability of 3 t o stoichiometric and catalytic reactions including an oxidative-addition step is thus suggested and open t o investigation. A second obvious use of the 1,l-diphosphine 3 is the building of new bimetallic complexes and the exploration of their reactivity. The chirality of the ligand provides a supplementary dimension with respect to previous studies. A bimetallic rhodium complex was synthesized, as shown in eq 4. The diphosphine 3 was 2 Men- ~
P32 e
-
3
3 c35
~ p p ~ ~ R h ~ c o D ~ c l 1 2co
C6H6,25’C
C
w Rh2
3 P(S) C(S) I
L
1
l
I
5
reacted with [(COD)RhC1]2 in benzene; then, carbon Figure 2. Crystal structure of complex 5. For clarity, only monoxide was bubbled through the solution. Stirring the ipso carbon atoms of the phenyl rings are illustrated. under a CO atmosphere for about 2 h led to a yellow Main bond lengths (A) and angles (deg): Rh(l)-Cl(l), solution containing mainly the complex 5,13which was 2.390(1);Rh(B)-Cl(l), 2.372(1);Rh(l)-P(5), 2.354(1);Rh(1)purified by column chromatography (alumina, etherP(32),2.324(1);Rh(2)-P(36), 2.352(1);Rh(2)-P(l), 2.336(1); Rh(l)-C(65), 1.796(6); P(5)-C(4), 1.839(5); C(4)-P(1), methanol (9O:lO)) and obtained in 60% yield. 1.879(5);P(l)-C(2), 1.881(5);C(2)-C(3), 1.564(9);C(3)The 31PNMR spectrum of 5 indicates the CZ symC(4), 1.585(7);Rh(l)-Cl(l)-Rh(P), 85.87(4); Rh(l)-P(5)metry of the molecule with two equivalent phosphetane C(4),110.9(2);P(5)-C(4)-P(l), 121.7(3);C(4)-P(l)-Rh(2), phosphorus atoms and two equivalent PPhz groups. 31P 120.2(2);C(4)-P(l)-C(2). 77.1(2);P(l)-C(2)-C(3), 89.8(3); NMR (CDCl3): 6 84.2, ddd, ‘ J p - m = 110 Hz, ‘Jp-p = 310 Hz (trans to Rh),2 J ~ = 26 -~ Hz; 6 16.5, ddd, ~ J P - R C( ~2)-C( 3)-C(4), 96.2(4);C(3)-C(4)-P( l),89.3(3). = 122 Hz. respective configuration, complex 5 shows a bridging The molecular structure of 5 was established by X-ray chlorine atom, the second one acting as a counterion to diffraction ana1y~is.l~Figure 2 shows the ORTEP the cationic complex. The structure of 5 is then much diagram and lists the main bond distances and angles. more similar to that of the cationic “A-frame”complex In comparison to the corresponding dppm complex Rhz[Rh~(CO)~Cl(dppm)21+BF4-.~~ The bridging chlorine Clz(CO)~(dppmh,~~ complex 5 shows very different atom lies on the Cz symmetry axis of the molecule. structural features. Whereas the dppm complex bears Bonding angles and distances are in reasonable agreetwo terminal C1 ligands, one on each rhodium, in a trans ment with the above-cited structural determinations,except for those directly affected by the phosphetane (13)[(COD)RhCl]z(50 mg) was added to a solution of 3 (90 mg, 0.2 mmol) in benzene (1mL) at room temperature. After about 10 min, moiety.l7 carbon monoxide was bubbled through the solution. The mixture was To our knowledge, complex 5 is the first bimetallic then stirred under the CO atmosphere for 2 h. The solution was “A-frame”complex of a homochiral 1,l-diphosphine. Its directly chromatographed on a short alumina column, first with ether and then with ether-methanol (9O:lO) as eluent. The yellow band, easy accessibility encourages the development of the eluted with the ether-methanol mixture, was collected. Removal of synthesis and reactivity of new homo- and heterobimethe solvent gave 75 mg (60%) of complex 5. Selected data for complex 5 are as follows. Anal. Calcd for C B ~ H ~ O Z P & ~ Z R ~ Z . ~C, CH 52.90; Z C ~ Z : tallic complexes of 3 and the exploration of their implications regarding bimetallic homogeneous asymH, 6.30. Found: C, 52.47; H, 6.48. IR: v(C0) 1990 cm-’. 13C NMR (CDClQ):6 17.6 (Me). 21.9 (Me). 23.0 (2 Me). 24.0 (Me). 25.0 (d. JLD metric catalysis. = l 2 . i H z , CHz), 27.3 (dd, Jc-p’=30.2, Jc-p’= 10.9 Hz; Me), 3i.076, Supporting InformationAvailable: For 4 and 5, tables J c - p = 5.5 Hz, Me), 32.8 (d, Jc-p = 9.8 Hz, CH), 34.6 (CHz), 36.5 (CHz), 42.0 (CH), 45.4 (dd, Jc-p = 16.8, Jc-p = 10.7 Hz, PCHP), 46.7 (d, Jc-p of X-ray crystal data and experimental details,positional and = 4.5 Hz, CMeZ), 47.9 (dd, J c - p = 28.9, J c - p = 17.9 Hz, CMeZ), 48.8 thermal parameters, and bond lengths and angles (18 pages). (d, Jc-p = 7.5 Hz, CH). information is given on any currrent masthead page. (14) Crystal data for complex 5: C H ~ & ~ z O ~ P ~ R ~ Z . space ~ C H Z C ~ Ordering ~;
2,
oup P212121 (No. 19);a = 15.079(2) b = 17.910(2)A, c = 25.125(2) V = 6785.4(2.2)A3, Z = 4; dcale= 1.378 g/cm3. Data were collected at -150 & 0.5 “C on a n Enraf-Nonius CAD4 diffractometer using Mo Ku radiation ( I = 0.710 73 A) and a graphite monochromator. The crystal structure was solved and refined using the Enraf-Nonius MOLEN package. The SIR92 direct methods suite yielded a solution for all atoms. Anisotropic temperature factors were used for all nonhydrogen atoms in the final stages of least-squares refinement, and a non-Poisson weighting scheme was applied with a p factor equal to 0.08: number of observed reflections 8046; final R = 0.054.
OM950601C (15)(a) Cowie, M.; Dwight, S. K. Inorg. Chem. 1980,19, 2500. (b) Mague, J. T. Inorg. Chem. 1969, 8, 119. (16) Cowie, D.; Dwight, S. K. Inorg. Chem. 1979, 18, 2700. (17) As an example, the Rh(2)-P(l)-C(4) and P(l)-C(4)-P(5) angles (120.2(2) and 121.7(3)”,respectively) are significantly larger than those previously observed in dppm complexes (112 and 115”. respectively).
