- Email: [email protected]
Synthesis of the new metalloligands [η6-(PPh2)xC6H6−x]Cr(CO)2(L) [x = 1,2; L = CO and PR3] and some rhodium(I) complexes
M. E. WRIGHT et al.
324
(1)
In this paper we present a transmetallation reaction of the tri-n-butylstannyl group on (q6-arene) Cr(CO),(L) systems where L = PPh3 and PBu3. The new metalloligands prepared in the present study were used in the synthesis of new coordination polymers. The principal driving force behind preparing the phosphine substituted complexes was to increase the solubility of these novel macromolecular building blocks. RESULTS AND DISCUSSION Transmetallation reactions
butylstannane groups is known to involve an equilibriumLo process ; hence, the stability of the dilithio product, {$-l,4-(Li)2C6H4}Cr(CO)Z(PBun~) (3), can directly influence the success of the reaction. In the case where {#‘-1,4-(Li)&6H4}Cr(C0)3 was generated cleanly, the equilibrium clearly favoured transmetallation of both tri-n-butylstannane groups. However, now with the more electron rich Cr(CO),(PBu”,) moiety it appears the equilibrium reaction of 3 with tetra-n-butylstannane is competitive. Photolysis of a benzene solution containing (r16-(Bu”$n)C6HS}Cr(C0)3 (6) and triphenylphosphine produced the substituted complex {@-(Bun3 Sn)C6HS)Cr(CO)Z(PPh3) (7) in good yield. Both complexes 6 and 7 have been cleanly transmetallated with “BuLi and quenched with Ph2PCl to afford the substituted metalloligands (8) in excellent yield (Scheme 2).
Irradiation of {16-1,4-(SUBUn3)2CsH4)C~(co)~6 in a benzene solution containing tri-n-butylphosphine (1.2 mol equiv.) for 6 h affords the substituted complex {$-1,4-(SnBUnJ&H4} Cr(CO)* (PBu”,) (2) (Scheme 1).9 Column chromatography on alumina gave analytically pure 2 as a red oil. Treatment of 2 with “BuLi (2.2 mol equiv.) in tetrahydrofuran (thf) at -78°C followed by a quench Preparation of heterobimetallic coordination with PhZPCl afforded as the major product {q6- polymers l,4-(PPh2)C6H4}Cr(CO)2(PBu”R) (4) (50% isoComplex 4 and {$-l,4-(PPh2)C6H4}Cr(CO)3 lated yield) along with a minor amount of {q6-l(SnBu”&4-(PPhZ)C6H4}Cr(CO)2(PBu”3) (5). A sig- (9)6 reacted with [(CO),RhCl], (0.5 mol equiv.) in benzene solution to produce free carbon monoxide nificant amount of material is lost in the purification through column chromatography. The identity of and the coordination polymers I ’ {[q 6-1,4-(PPh2) 2 C,H,Cr(CO),L]Rh(CO)Cl}, (lOa, L = CO; lob, the by-product(s) is not known. The transmetallation reaction involving tri-n- L = PBu”,) as yellow and orange powders B”3sne
SnBu3
Benzene
Bu3Snw
SnBu3
I
oc-hr. 1
I I
.
co
PBua , irradiation
;;;co
oc-
co 1
3
1. n-BuLi, 2 equiv 2. Ph2PCI
/
J
Ph2Pa
PPh2 t&r 06
1 ‘CO
Bu3Sna
+
PBu3
PPh2
oc’
k 1
PBu3
5
4 Scheme 1.
co
2
Synthesis of new metalloligands
325
e
SnB% I
o&go
6 1. PPh3, in 2. RBuLi 3. Ph,PCI
\ e
I oc
.
PPh:!
I Cr-t CO oc” bPh 3
Cr‘CO 60
8a
8b Scheme 2.
(Scheme 3). Monito~ng the fo~ation of 1Oa by 3’P NMR spectroscopy indicated the absence of uncoordinated PPh2 groups (i.e. < 1%) suggesting that n (Scheme 3) is large or that rings are formed. l2 As the solution ages, the yellow product precipitates and cannot be redissolved in benzene, dichloromethane or thf. The solid mull IR spectrum of the precipitated solid contains terminal carbonyl bands at 1995 (Rh-bound), 1970 and 1905 cm-’ (Cr-bound) vs 1988, 1966 and 1905 cm-’ for the benzene filtrate. The 31P NMR spectrum of the latter consists of a major doublet at 29.2 [J(P-Rh) = 132 Hz] and minor doublets at 29.0 and 28.7 ppm [J(P-Rh) = 133 Hz for both]. While the solubility of 1Ob in benzene also decreases with time, the process is much slower and the resulting orange solid can be redissolved in dichloromethane. Reliable gel-permeation chromatography results were not obtained due to the thermal- and air-sensitivity of lob. The IR spectrum of lob showed three carbonyl bands, a virtual composite of 4 and the rhodium carbonyl band from lOa, as expected in the absence of significant
-czz, 0
P&P
Cr-Rh electronic interactions. The “H and 31P NMR spectra of lob at 25°C both contained broad resonances suggestive of a dynamic process. Attaining the high tem~rat~e exchange limit was hindered by sample decomposition above 50°C and attempts to cool toluene solutions of 1Obled to glass formation as high as - 20°C again pointing to the polymeric nature of these compounds. Dichloromethane solutions of lob proved to be suitable for low-temperature work and the 3’P DNMR spectra (Fig, I) indicate the presence of two types of PPhL, substituents trans to each other [J(P-P) = 356 Hz] on rhodium [J(P-Rh) = 128 Hz], suggesting that rotation of the Cr(C0)2PBu”3 vertex with respect to the q6-arene ring is slow on the NMR time scale below -60°C. As the “P NMR spectrum of 4 contains two sharp singlet resonances at - 90°C we conclude that the hindered chromium-arene bond rotation is a reszdt of theformat~~~ of the coordination polymer. Simulation of the 3‘P DNMR spectra of lob allows us to estimate the activation parameters for the q6-arene-chromium bond rotation : A@ = 11.7+0.1.AHf = 10.1rfiOSkcalmol-‘and
PPh2
I
oc-cr-W i CO
lOa,L=co lob, L= PBy Scheme 3.
,Cr
Oc ixco
321
Synthesis of new metalloligands
24.6 (d, J= 11 Hz), 13.8 (CH,), 13.6 (CHJ, 9.9 (CHJ; IR (hexanes) v(C0) 1883 and 1835 cm-‘. Found : C, 54.8 ; H, 8.9. Calc. for C44Hs80ZPSn2 : C, 54.7 ; H, 8.9%.
General All manipulations of compounds and solvents were carried out using standard Schlenk techniques. ’ 4 Solvents were degassed and purified by distillation under nitrogen from standard drying agents. NMR spectra were obtained using the following spectrometers : ‘H, Varian XL 300 or GE QE-300 ; ’ 3C, Varian XL 300 (at 75.4 MHz) ; 3’P, Nicolet NMC-300 (121 MHz). The 3’P NMR chemical shifts are reported positive downfield from external 85% H3P04. Proton and carbon NMR spectra are reported in 6 vs Me,Si as the reference. The NMR simulations were performed using a locally-modified version of DNMR3. IR spectra were recorded on either a Perkin-Elmer 983 or 1750 spectrometer. Photolysis experiments utilized a 175 Watt medium pressure mercury lamp (a modified yard lamp) and the sample contained in a water jacketed quartz reaction vessel. The {$-1,4-(&r Bu”3)2C,H4)Cr(CQ)3,6 tributylphenylstannane, ’ ’ ~(CO)*Rh~l]*‘6 and [(COD)RhCl]~” were prepared by literature methods. The tributylchlorostannane, ~ibutylphosphine, “BuLi (2.5 M in hexanes) and diphenylchlorophosphine were purchased from Aldrich Chemical Company and used as received. The chromium hexacarbonyl was purchased from Pressure Chemical Company. The neutral MPLC grade alumina (non-activated) used in the study was purchased from Universal Scientific Co. and used as received. Elemental analyses were performed at Atlantic Microlab Inc. and Pascher Mikroanalytisches Laboratory, Germany. Prepapatio~
(PBu” 3)
of
~~6-l,~(SnBun~)~C~H~~Cr(CO)~
121
A benzene (2.04 cm3) solution containing ($- 1,4~SnBun~)~C~H~~~r(CO)~(3.7 g, 5.0 mmol) and trin-butylphosphine (1.2 g, 6.0 mmol) was photolysed for 5 h. The mixture was allowed to cool and the solvent was removed under reduced pressure. The crude product was subjected to cohuun chromatography (2 x 25 cm) on neutral alumina, eluting with petroleum ether. The yellow band was collected and the solvents were removed to afford spectroscopically pure ~~6-l,4-(SnBun3)~~~H~~ Cr(CO),(PBu”,) (2) (4.01 g, 86%). ‘H NMR (CDC13) 6 4.63 (d, J = 2.0 Hz, 4 H), 1.68-1.57 (m, 18 H), 1.45-1.38 (m, 24 H), 1.04-1.18 (m, 12 H), 0.96-0.89 (m, 27 H) ; 13C NMR &DC&) 6 241.7 (d, J = 21 Hz), 136.2 ($-phenyl), 98.6 (@-phenyl), 94.4 (s with ’ ’ 7*1“Sn satellites}, 31. I (d, J = 18 Hz), 29.1 (CH,), 27.4 (CH,), 25.8 (CH,),
Preparation Wu”3)
of
(q” - I,4 - (PPhz),CbH.,)Cr(CO)z
(41
A chilled (- 78°C) thf (20 cm3) solution containing {@-1,4-(SnBu”3)2C6H4)Cr(CO)rPBu”~ (0.78 g, 0.81 mmol) was treated with 2.5 equiv. of “Bu Li (0.80 cm3, 2.0 mmol) and TMEDA (1.0 cm3> and was allowed to stir for 30 min. Chlorodiphenylphosphine (0.53 g, 2.4 mmol) was added to the solution. The mixture was stirred for an additional 25 min and allowed to warm to ambient temperature. The solvents were removed under reduced pressure and the crude product was subjected to column chromatography (2 x 25 cm) on alumina eluting wth petroleum ether~ethyl acetate (50/ 1, v/v). The crude product split into two bands, the first was a minor yellow band identified as ($l-l-(SnBu”3)-4-(PPh&H~~Cr(CO)Z(PBu~) (5), the second major orange band was collected and the solvents removed under reduced pressure to afford 0.30 g (50%) of ~~6-l,4-(PPh~)~c6H~~ Cr(C0)2PBu”3 (4). ‘H NMR (CDCI,) 6 7.44 (br s, 20 H), 4.57 (br s, 4 H), 1.71-1.58 (m, 6H), 1.56 1.37 (m, 12 H), Loo-O.92 (m, 9H); 13C NMR (CDC13) 6 240.1 (dt, J = 21, 3 Hz, CO), 136.7 (d, J= 13 Hz), 134.2 (d, J= 20 Hz), 129.1, 128.6 (d, J = 28 Hz), 98.0 (d, J = 14 Hz), 89.4 (dd, J = 5,21 Hz), 29.6 (d, J = 20 Hz), 25.5 (d, J = 15 Hz), 24.5 (d, J== 15 Hz), 13.8 (CH,); “P NMR (C,D,) S I 59.9 (s, PBun3), - 5.0 (s, PPh2) ; IR (hexanes) v(C0) 1901 and 1856cm-‘. Found: C, 69.8; H, 6.9. Calc. for C44H5tCr02P3: C, 69.8; H, 6.8%. Spectroscopic data for 5 (contaminated by an unidentified by-product): ‘H NMR (CDC13) distinguishing peaks at d 4.58 (m, 2 H), 4.47 (m, 2H) and IR (hexanes) v(C0) 1891 and 1844 cm- ‘. Preparation
of ~~6-(SnBun~)~~H~~Cr~CO)~(6)
A solution of acetonitrile (60 cm3) containing Cr(CC& (3.0 g, 13.6 mmol) and tetrahydrofuran (5 cm3) was heated at reflux for 12 h. The mixture was allowed to cool and the solvents removed. The yellow solid was redissolved in p-dioxane (75 cm3) and tributylphenylstannane (5.0 g, 13.7 mmol) and the mixture was heated at reflux for 24 h. The mixture was allowed to cool, diluted with petroleum ether (100 cm3), and then filtered through a pad of alumina. The alumina pad was washed with benzene (50 cm’) and the solvent removed from the filtrate under reduced pressure. The crude product
328
M. E. WRlGHT
was chromatographed on neutral alumina eluting with petroleum ether. The yellow band was collected and the solvent was removed to afford pure 6 (2.51 g, 90%) as a yellow oil. ‘H NMR (CDC13) 6 5.39 (m, 1 H), 5.26 (m, 2H), 5.15 (m, 2 H), 1.58 1.49 (m, 6 H), 1.37-1.27 (m, 6 H), 1.25-1.08 (m, 6 H), (X92-0.81 (m, 9 H); ‘3C NMR (CDC13) 6 233.7 (CO), 101.5 (s with satellites, q”-phenyl), 100.5 (ipso-carbon, $-phenyl), 94.8 (@-phenyl), 92.5 (s with satellites, q6-phenyl), 28.9 (CH,), 27.3 (CH,), 13.6 (CH,), 10.4 (CH,) ; IR (hexanes) v(C0) 1974 and 1906 cm- ‘. Found : C, 50.5 ; H, 6.6. Calc. for C,,H,,OKrSn: C. 50.1 ; H, 6.4%. Preparation of (~6-(SnBu”3)C6Hs)Cr(CO)z(PPh~)
(7) A benzene (30 cm3) solution containing 6 (2.0 g, 4.0mmol) and triphenylphosphine (2.5 g, 9.5 mmol) was irradiated for 42 h. The solvents were removed under reduced pressure to afford an orange oil. The crude product was column chromatographed in a separatory funnel (250 cm3 size) eluting with petroleum ether. The orange band was collected and the solvents were removed to yield 7 (2.51 g, 86%) as an orange solid. ‘H NMR (CDC13) 6 7.49 7.33 (m, 15 H), 4.92 (m, 2 H), 4.30 (m, 3 H), 1.631.55 (m, 6 H), l-41-1.34 (m, 6 H), 1.31-1.09 (m, 6 H), 0.96-0.88 (m, 9 H) ; ’3C NMR (CDC13) S 242.2 (d, J= 21 Hz), 139.6 (d, J= 33 Hz), 133.6 (d, J = 20 Hz), 132.8 (d, J = 1I Hz), 128.7 (d, J = 28 Hz), 127.7 (d, J = 9 Hz), 96.7 (@-phenyl), 93.6 ($-phenyl), 92.2 (ipso-carbon, qbphenyl), 91.4 (06phenyl), 29.0 (CH,), 27.4 (CH,), 13.7 (CH,), 10.2 (CH,) ; IR (hexanes) v(C0) 1902 and 1852 cm-‘. Samples were contaminated by solvent which could not be removed under reduced pressure or eliminated by recrystallization. Preparation of f@-(PPh,)C6H,)Cr(Co)o>2(L) (8)
A chilled (- 78°C) thf (15 cm3) solution containing (?6-(SnBu3)C6H5)Cr(C0)2PPh3 (0.35 g, 0.48 mmol) was treated with 2.5 equiv. of “BuLi (0.23 cm3, 0.57 mmol) and allowed to stir for 30 min. Chlorodiphenylphosphine (0.13 g, 0.57 mmol) was then added and the solution was allowed to warm to ambient temperature for 25 min. The solvents were removed under reduced pressure and the crude product was subjected to separatory funnel (250 cm3 size funnel) column chromatography on neutral alumina, eluting with petroleum ether/ethyl acetate (50/l, v/v). The yellow-orange band was collected and the solvents were removed under reduced pressure to yield 0.27 g (87%) of 8b as an orange solid. ‘H NMR (CDCl,) 6 7.55-7.33 (m, 25
et al.
H), 4.78 (apparent t, J = 5 Hz, 2 H), 4.49 (m, 2 H), 4.45 (m, 1 H); 31P NMR (CDCl,) 6 92.0 (PPh,), -2.9 (PPh,), IR (hexanes) v(C0) 1912 and 1866 cm-‘. Found: C, 72.5; H, 4.9. Calc. for C&H30 @C&P? : C, 72.1; H, 4.8%. In a similar manner complex 8a was prepared in 93% isolated yield. Spectroscopic data was identical to that previously reported for 8a. 5
A solution of 137 mg (0.2 mmol) [$‘-1,4(PPhZ)ZC6H&r(CG)3 in 2 cm3 of benzene was added dropwise to a solution of 39 mg (0.12 mmol) fRhCI(CO)& in 1 cm3 of benzene. Gas evolution was accompanied by the slow formation of a yellow precipitate from the orange solution. After 14 h the precipitate was filtered off, washed with pentane (2 x 5 cm3) and dried under reduced pressure to yield 112 mg (75%) of 10a. Some benzene was retained in the product even after drying for severaf hours. Found: C, 55.9; H, 3.5; Cl, 4.6; Cr, 7.0; Rh, 12.8. Cak. for 0.33[c~H6]c~6H~~clc~~P*Rh : c, 55.8; H, 3.4; Cl, 4.6; Cr, 6.7; Rh, 13.3%. IR (mineral oil mull, Csl) v(C0) = 1995, 1970, 1905 cm-‘. IR of filtrate (benzene) v(C0) = 1988, 1966, 1905 cm-‘. 31P(‘H) NMR of filtrate (C,D,) 29.2 [d, J(P-Rh) = 132 Hz] plus minor resonances at 29.0 [d, J(P-Rh) = 133 Hz] and 28.7 ppm [d, J(P-Rh) = 133 Hz]. Pr~par~tjo~ of ~[~‘-l,~(PPh*~~~~H~Cr(CO)*PBu*~] Rh(CO)Cl 1, (lob)
A solution of 179 mg (0.24 mmol) [$-1,4(PPh2)2C6H,]Cr(C0)2(P13un3) in 2 cm3 of benzene was added dropwise to a solution of 39 mg (O.l2 mmol) [RhCl(CO)~]~ in 1 cm3 of benzene. The solution turned red with visible gas evolution. After 4 h the solvent was removed under reduced pressure and the residue washed with pentane (2 x 5 cm3) and dried under reduced pressure to give 187 mg (84%) of lob as an orange solid. Found: C, 58.7; H, 5.7; Cl, 3.9; Cr, 5.5; Rh, 10.1. CaIc. for C4jHj1ClCT03P&h: C, 58.5; H, 5.6; Cl, 3.8; Cr, 5.6 ; Rh, 11.1%. IR (benzene) 1987 (s), 1892 (vs), 1845 (s) cm- ‘. ‘H NMR (C6D6) 6 7.91 (br, 8H, PPh2), 7.20 (br, 4H, PPh& 7.07 (br, 8H, PPh& 5.55 (v br, 4H, C,H& 2.32 (br, 6H, C~~CH~CH*CH3~, 1.52 (br, 6H, CH&N&ZH,CH,), 1.36 (br, 6H, CH,CH&HL7CH3), 0.79 (br, 9H, CH,); 31P NMR (toluene-ds, 50°C) 6 48.3 (s, PBun3), 23.8 [d, J(P-Rh) = 128 Hz, PPh2]; in dichloromethane/ toluene-d, (3/l, v/v) at - 60°C 52.9 (s), 31.5 [dd,
Synthesis of new metalloligands J(P-P)=356 Hz, f(P-Rh) J(P-Rh) = 128 Hz].
= 128 Hz], 20.7 [dd,
Ack~~~ie~ge~e~~~-MEW wishes to thank the donors of the Petroleum Research Fund, administered by the American Chemical Society for partial funding of this research. LL ackuow~~ges partial support of this work through a grant from the Undergraduate Research Of&e and the Department of Chemistry and Biochemistry at Utah State University. RTB thanks T. J. Onley for expert technical assistance. Suppleme~tury material avai~abl~One plot of In k versus I IT (one page).
linear Arrhenius
REFERENCES 1. E, 0. Fischer and K. Ofele, Z. ~a~u~f~r~~~., Tiel B
2.
3.
4. 5. 6. 7.
1958, 13,458 : B. Nicholls and M. C. Whiting, Proc. Chem. Sot. 1958, 152; G. Natta, R, Ercoii and F. Calderazzo, C&m. I&. f958,40,287. (a) S. Top and G. Jaouen, J. ~rg~omet. Ckem. 1979, 182, 381; (bj C. A. L. Mahaffy and P. L. Pauson, Znorg. Synth. 1979, 39, 154 ; (c) G. R. Knox, D. G. Leppard, P. L. Pauson and W. E. Watts, J. &gem+ mef. Chem. 1972,34,347. We have recently prepared {q6-1,4-bis(CH,SO,) C,H,fCr(CO), indirectly through the reaction of (16-1,4-bis(OH)C6HsfC~C0)3 with methanesuipbonyl chloride. M. E. Wright, J. ~r~~~ornet. Chem. 1990,376,353. M. D. Rausch and R. E. Gloth, J. Or~~~rne~. Chem. 1978, 153, 59. M. F. Semmelhack, J. Bisaha and M. Czarny, J. Am. Chem. Sot, 1979,101,768. M. E. Wright, ~rgo~ometa~i~cs 1989,8,407. D. Seyferth and M. A. Weiner, f. Am. Chem. Sot. 1961, 83, 3583; D. Seyferth and L. G. Vaughn, J. Am. Chem. Sot. 1962, 84, 361; 3. Am. Chem. Sot. 1964, 86, 883. For a more recent application of this
329
reaction see: W. D. Wulff, G. A. Peterson, W. E. Bauta, K. Chart, K. L. Faron, S. R. Gilbertson, R. W. Kaesler, D. C. Yang and C. K. Murray, J. Org. C&em. 1986,51,279 and refs therein. 8. For example see: D. W. Macomber, W. P. Hart and M. D. Rausch, Adv. Organomet. Chem. 1982,21,1; M. E. Wright, ~rg~~~~e~~~~~c~1990, 9, 853 and refs therein. For $‘-arene ligands see: J. A. Heppert, J. Aube, M. E. Thomas-Miller, M. L. Milligan and F. Takusagawa, ~rg~ometailics 1990, 9, 727 and refs therein. 9. For a general treatment of ligand substitution on ~~6-arene~Cr(CO)~ complexes see. R. Davis and L. A. P. Kane-Maguire, Comprehe~~e ~r~~o~tQll~c Chem~try (Edited by G. Wilkinson. F. G. A. Stone and E. W. Abel), Vol. 3, pp. ~001-10~. Pergamon Press, Oxford (1982) and refs therein. IO. D. Seyferth and M, A. Weiner, J. Am. Chem. Sot. 1962,84,361. II. Org~~ometaIlic Polymers (Edited by C. E. Carraher Jr, J. Sheets and C. U. Pittman Jr). Academic Press, New York (1978) and refs therein. (2. Molecular modeling for rings of n = 3 (21 membered ring) and n = 4 (28 membered ring) indicated that these systems could be formed with no apparent ring strain. 13. For another illustration comparing the Cr(CO), and Cr(CO),(L) systems see: M. E. Wright, in ~~~~g~~jc and petal-Containjng Polymeric Mater&& (Edited by J. E. Sheats, C. E. Carraher Jr, C. U. Pittman Jr. M. Zeldin and B. Curteil), pp. 151-160. Plenum Press. New York (1991). 14. A. J. Gordon and R. A. Ford, The Chemists Companion. Wiley, New York (1972). 15. K. L. Jaura, H. S. Hundal and R. D. Handa, Znd. J. Chem. 1967,5,21 I. 16. J. A. McCleverty and G. Wilkinson, irnorg. Synth. 1966,8,211. 17. G. Giordano and R. H. Crabtree, inorg. Synth. 1979, 19,218.
324
(1)
In this paper we present a transmetallation reaction of the tri-n-butylstannyl group on (q6-arene) Cr(CO),(L) systems where L = PPh3 and PBu3. The new metalloligands prepared in the present study were used in the synthesis of new coordination polymers. The principal driving force behind preparing the phosphine substituted complexes was to increase the solubility of these novel macromolecular building blocks. RESULTS AND DISCUSSION Transmetallation reactions
butylstannane groups is known to involve an equilibriumLo process ; hence, the stability of the dilithio product, {$-l,4-(Li)2C6H4}Cr(CO)Z(PBun~) (3), can directly influence the success of the reaction. In the case where {#‘-1,4-(Li)&6H4}Cr(C0)3 was generated cleanly, the equilibrium clearly favoured transmetallation of both tri-n-butylstannane groups. However, now with the more electron rich Cr(CO),(PBu”,) moiety it appears the equilibrium reaction of 3 with tetra-n-butylstannane is competitive. Photolysis of a benzene solution containing (r16-(Bu”$n)C6HS}Cr(C0)3 (6) and triphenylphosphine produced the substituted complex {@-(Bun3 Sn)C6HS)Cr(CO)Z(PPh3) (7) in good yield. Both complexes 6 and 7 have been cleanly transmetallated with “BuLi and quenched with Ph2PCl to afford the substituted metalloligands (8) in excellent yield (Scheme 2).
Irradiation of {16-1,4-(SUBUn3)2CsH4)C~(co)~6 in a benzene solution containing tri-n-butylphosphine (1.2 mol equiv.) for 6 h affords the substituted complex {$-1,4-(SnBUnJ&H4} Cr(CO)* (PBu”,) (2) (Scheme 1).9 Column chromatography on alumina gave analytically pure 2 as a red oil. Treatment of 2 with “BuLi (2.2 mol equiv.) in tetrahydrofuran (thf) at -78°C followed by a quench Preparation of heterobimetallic coordination with PhZPCl afforded as the major product {q6- polymers l,4-(PPh2)C6H4}Cr(CO)2(PBu”R) (4) (50% isoComplex 4 and {$-l,4-(PPh2)C6H4}Cr(CO)3 lated yield) along with a minor amount of {q6-l(SnBu”&4-(PPhZ)C6H4}Cr(CO)2(PBu”3) (5). A sig- (9)6 reacted with [(CO),RhCl], (0.5 mol equiv.) in benzene solution to produce free carbon monoxide nificant amount of material is lost in the purification through column chromatography. The identity of and the coordination polymers I ’ {[q 6-1,4-(PPh2) 2 C,H,Cr(CO),L]Rh(CO)Cl}, (lOa, L = CO; lob, the by-product(s) is not known. The transmetallation reaction involving tri-n- L = PBu”,) as yellow and orange powders B”3sne
SnBu3
Benzene
Bu3Snw
SnBu3
I
oc-hr. 1
I I
.
co
PBua , irradiation
;;;co
oc-
co 1
3
1. n-BuLi, 2 equiv 2. Ph2PCI
/
J
Ph2Pa
PPh2 t&r 06
1 ‘CO
Bu3Sna
+
PBu3
PPh2
oc’
k 1
PBu3
5
4 Scheme 1.
co
2
Synthesis of new metalloligands
325
e
SnB% I
o&go
6 1. PPh3, in 2. RBuLi 3. Ph,PCI
\ e
I oc
.
PPh:!
I Cr-t CO oc” bPh 3
Cr‘CO 60
8a
8b Scheme 2.
(Scheme 3). Monito~ng the fo~ation of 1Oa by 3’P NMR spectroscopy indicated the absence of uncoordinated PPh2 groups (i.e. < 1%) suggesting that n (Scheme 3) is large or that rings are formed. l2 As the solution ages, the yellow product precipitates and cannot be redissolved in benzene, dichloromethane or thf. The solid mull IR spectrum of the precipitated solid contains terminal carbonyl bands at 1995 (Rh-bound), 1970 and 1905 cm-’ (Cr-bound) vs 1988, 1966 and 1905 cm-’ for the benzene filtrate. The 31P NMR spectrum of the latter consists of a major doublet at 29.2 [J(P-Rh) = 132 Hz] and minor doublets at 29.0 and 28.7 ppm [J(P-Rh) = 133 Hz for both]. While the solubility of 1Ob in benzene also decreases with time, the process is much slower and the resulting orange solid can be redissolved in dichloromethane. Reliable gel-permeation chromatography results were not obtained due to the thermal- and air-sensitivity of lob. The IR spectrum of lob showed three carbonyl bands, a virtual composite of 4 and the rhodium carbonyl band from lOa, as expected in the absence of significant
-czz, 0
P&P
Cr-Rh electronic interactions. The “H and 31P NMR spectra of lob at 25°C both contained broad resonances suggestive of a dynamic process. Attaining the high tem~rat~e exchange limit was hindered by sample decomposition above 50°C and attempts to cool toluene solutions of 1Obled to glass formation as high as - 20°C again pointing to the polymeric nature of these compounds. Dichloromethane solutions of lob proved to be suitable for low-temperature work and the 3’P DNMR spectra (Fig, I) indicate the presence of two types of PPhL, substituents trans to each other [J(P-P) = 356 Hz] on rhodium [J(P-Rh) = 128 Hz], suggesting that rotation of the Cr(C0)2PBu”3 vertex with respect to the q6-arene ring is slow on the NMR time scale below -60°C. As the “P NMR spectrum of 4 contains two sharp singlet resonances at - 90°C we conclude that the hindered chromium-arene bond rotation is a reszdt of theformat~~~ of the coordination polymer. Simulation of the 3‘P DNMR spectra of lob allows us to estimate the activation parameters for the q6-arene-chromium bond rotation : A@ = 11.7+0.1.AHf = 10.1rfiOSkcalmol-‘and
PPh2
I
oc-cr-W i CO
lOa,L=co lob, L= PBy Scheme 3.
,Cr
Oc ixco
321
Synthesis of new metalloligands
24.6 (d, J= 11 Hz), 13.8 (CH,), 13.6 (CHJ, 9.9 (CHJ; IR (hexanes) v(C0) 1883 and 1835 cm-‘. Found : C, 54.8 ; H, 8.9. Calc. for C44Hs80ZPSn2 : C, 54.7 ; H, 8.9%.
General All manipulations of compounds and solvents were carried out using standard Schlenk techniques. ’ 4 Solvents were degassed and purified by distillation under nitrogen from standard drying agents. NMR spectra were obtained using the following spectrometers : ‘H, Varian XL 300 or GE QE-300 ; ’ 3C, Varian XL 300 (at 75.4 MHz) ; 3’P, Nicolet NMC-300 (121 MHz). The 3’P NMR chemical shifts are reported positive downfield from external 85% H3P04. Proton and carbon NMR spectra are reported in 6 vs Me,Si as the reference. The NMR simulations were performed using a locally-modified version of DNMR3. IR spectra were recorded on either a Perkin-Elmer 983 or 1750 spectrometer. Photolysis experiments utilized a 175 Watt medium pressure mercury lamp (a modified yard lamp) and the sample contained in a water jacketed quartz reaction vessel. The {$-1,4-(&r Bu”3)2C,H4)Cr(CQ)3,6 tributylphenylstannane, ’ ’ ~(CO)*Rh~l]*‘6 and [(COD)RhCl]~” were prepared by literature methods. The tributylchlorostannane, ~ibutylphosphine, “BuLi (2.5 M in hexanes) and diphenylchlorophosphine were purchased from Aldrich Chemical Company and used as received. The chromium hexacarbonyl was purchased from Pressure Chemical Company. The neutral MPLC grade alumina (non-activated) used in the study was purchased from Universal Scientific Co. and used as received. Elemental analyses were performed at Atlantic Microlab Inc. and Pascher Mikroanalytisches Laboratory, Germany. Prepapatio~
(PBu” 3)
of
~~6-l,~(SnBun~)~C~H~~Cr(CO)~
121
A benzene (2.04 cm3) solution containing ($- 1,4~SnBun~)~C~H~~~r(CO)~(3.7 g, 5.0 mmol) and trin-butylphosphine (1.2 g, 6.0 mmol) was photolysed for 5 h. The mixture was allowed to cool and the solvent was removed under reduced pressure. The crude product was subjected to cohuun chromatography (2 x 25 cm) on neutral alumina, eluting with petroleum ether. The yellow band was collected and the solvents were removed to afford spectroscopically pure ~~6-l,4-(SnBun3)~~~H~~ Cr(CO),(PBu”,) (2) (4.01 g, 86%). ‘H NMR (CDC13) 6 4.63 (d, J = 2.0 Hz, 4 H), 1.68-1.57 (m, 18 H), 1.45-1.38 (m, 24 H), 1.04-1.18 (m, 12 H), 0.96-0.89 (m, 27 H) ; 13C NMR &DC&) 6 241.7 (d, J = 21 Hz), 136.2 ($-phenyl), 98.6 (@-phenyl), 94.4 (s with ’ ’ 7*1“Sn satellites}, 31. I (d, J = 18 Hz), 29.1 (CH,), 27.4 (CH,), 25.8 (CH,),
Preparation Wu”3)
of
(q” - I,4 - (PPhz),CbH.,)Cr(CO)z
(41
A chilled (- 78°C) thf (20 cm3) solution containing {@-1,4-(SnBu”3)2C6H4)Cr(CO)rPBu”~ (0.78 g, 0.81 mmol) was treated with 2.5 equiv. of “Bu Li (0.80 cm3, 2.0 mmol) and TMEDA (1.0 cm3> and was allowed to stir for 30 min. Chlorodiphenylphosphine (0.53 g, 2.4 mmol) was added to the solution. The mixture was stirred for an additional 25 min and allowed to warm to ambient temperature. The solvents were removed under reduced pressure and the crude product was subjected to column chromatography (2 x 25 cm) on alumina eluting wth petroleum ether~ethyl acetate (50/ 1, v/v). The crude product split into two bands, the first was a minor yellow band identified as ($l-l-(SnBu”3)-4-(PPh&H~~Cr(CO)Z(PBu~) (5), the second major orange band was collected and the solvents removed under reduced pressure to afford 0.30 g (50%) of ~~6-l,4-(PPh~)~c6H~~ Cr(C0)2PBu”3 (4). ‘H NMR (CDCI,) 6 7.44 (br s, 20 H), 4.57 (br s, 4 H), 1.71-1.58 (m, 6H), 1.56 1.37 (m, 12 H), Loo-O.92 (m, 9H); 13C NMR (CDC13) 6 240.1 (dt, J = 21, 3 Hz, CO), 136.7 (d, J= 13 Hz), 134.2 (d, J= 20 Hz), 129.1, 128.6 (d, J = 28 Hz), 98.0 (d, J = 14 Hz), 89.4 (dd, J = 5,21 Hz), 29.6 (d, J = 20 Hz), 25.5 (d, J = 15 Hz), 24.5 (d, J== 15 Hz), 13.8 (CH,); “P NMR (C,D,) S I 59.9 (s, PBun3), - 5.0 (s, PPh2) ; IR (hexanes) v(C0) 1901 and 1856cm-‘. Found: C, 69.8; H, 6.9. Calc. for C44H5tCr02P3: C, 69.8; H, 6.8%. Spectroscopic data for 5 (contaminated by an unidentified by-product): ‘H NMR (CDC13) distinguishing peaks at d 4.58 (m, 2 H), 4.47 (m, 2H) and IR (hexanes) v(C0) 1891 and 1844 cm- ‘. Preparation
of ~~6-(SnBun~)~~H~~Cr~CO)~(6)
A solution of acetonitrile (60 cm3) containing Cr(CC& (3.0 g, 13.6 mmol) and tetrahydrofuran (5 cm3) was heated at reflux for 12 h. The mixture was allowed to cool and the solvents removed. The yellow solid was redissolved in p-dioxane (75 cm3) and tributylphenylstannane (5.0 g, 13.7 mmol) and the mixture was heated at reflux for 24 h. The mixture was allowed to cool, diluted with petroleum ether (100 cm3), and then filtered through a pad of alumina. The alumina pad was washed with benzene (50 cm’) and the solvent removed from the filtrate under reduced pressure. The crude product
328
M. E. WRlGHT
was chromatographed on neutral alumina eluting with petroleum ether. The yellow band was collected and the solvent was removed to afford pure 6 (2.51 g, 90%) as a yellow oil. ‘H NMR (CDC13) 6 5.39 (m, 1 H), 5.26 (m, 2H), 5.15 (m, 2 H), 1.58 1.49 (m, 6 H), 1.37-1.27 (m, 6 H), 1.25-1.08 (m, 6 H), (X92-0.81 (m, 9 H); ‘3C NMR (CDC13) 6 233.7 (CO), 101.5 (s with satellites, q”-phenyl), 100.5 (ipso-carbon, $-phenyl), 94.8 (@-phenyl), 92.5 (s with satellites, q6-phenyl), 28.9 (CH,), 27.3 (CH,), 13.6 (CH,), 10.4 (CH,) ; IR (hexanes) v(C0) 1974 and 1906 cm- ‘. Found : C, 50.5 ; H, 6.6. Calc. for C,,H,,OKrSn: C. 50.1 ; H, 6.4%. Preparation of (~6-(SnBu”3)C6Hs)Cr(CO)z(PPh~)
(7) A benzene (30 cm3) solution containing 6 (2.0 g, 4.0mmol) and triphenylphosphine (2.5 g, 9.5 mmol) was irradiated for 42 h. The solvents were removed under reduced pressure to afford an orange oil. The crude product was column chromatographed in a separatory funnel (250 cm3 size) eluting with petroleum ether. The orange band was collected and the solvents were removed to yield 7 (2.51 g, 86%) as an orange solid. ‘H NMR (CDC13) 6 7.49 7.33 (m, 15 H), 4.92 (m, 2 H), 4.30 (m, 3 H), 1.631.55 (m, 6 H), l-41-1.34 (m, 6 H), 1.31-1.09 (m, 6 H), 0.96-0.88 (m, 9 H) ; ’3C NMR (CDC13) S 242.2 (d, J= 21 Hz), 139.6 (d, J= 33 Hz), 133.6 (d, J = 20 Hz), 132.8 (d, J = 1I Hz), 128.7 (d, J = 28 Hz), 127.7 (d, J = 9 Hz), 96.7 (@-phenyl), 93.6 ($-phenyl), 92.2 (ipso-carbon, qbphenyl), 91.4 (06phenyl), 29.0 (CH,), 27.4 (CH,), 13.7 (CH,), 10.2 (CH,) ; IR (hexanes) v(C0) 1902 and 1852 cm-‘. Samples were contaminated by solvent which could not be removed under reduced pressure or eliminated by recrystallization. Preparation of f@-(PPh,)C6H,)Cr(Co)o>2(L) (8)
A chilled (- 78°C) thf (15 cm3) solution containing (?6-(SnBu3)C6H5)Cr(C0)2PPh3 (0.35 g, 0.48 mmol) was treated with 2.5 equiv. of “BuLi (0.23 cm3, 0.57 mmol) and allowed to stir for 30 min. Chlorodiphenylphosphine (0.13 g, 0.57 mmol) was then added and the solution was allowed to warm to ambient temperature for 25 min. The solvents were removed under reduced pressure and the crude product was subjected to separatory funnel (250 cm3 size funnel) column chromatography on neutral alumina, eluting with petroleum ether/ethyl acetate (50/l, v/v). The yellow-orange band was collected and the solvents were removed under reduced pressure to yield 0.27 g (87%) of 8b as an orange solid. ‘H NMR (CDCl,) 6 7.55-7.33 (m, 25
et al.
H), 4.78 (apparent t, J = 5 Hz, 2 H), 4.49 (m, 2 H), 4.45 (m, 1 H); 31P NMR (CDCl,) 6 92.0 (PPh,), -2.9 (PPh,), IR (hexanes) v(C0) 1912 and 1866 cm-‘. Found: C, 72.5; H, 4.9. Calc. for C&H30 @C&P? : C, 72.1; H, 4.8%. In a similar manner complex 8a was prepared in 93% isolated yield. Spectroscopic data was identical to that previously reported for 8a. 5
A solution of 137 mg (0.2 mmol) [$‘-1,4(PPhZ)ZC6H&r(CG)3 in 2 cm3 of benzene was added dropwise to a solution of 39 mg (0.12 mmol) fRhCI(CO)& in 1 cm3 of benzene. Gas evolution was accompanied by the slow formation of a yellow precipitate from the orange solution. After 14 h the precipitate was filtered off, washed with pentane (2 x 5 cm3) and dried under reduced pressure to yield 112 mg (75%) of 10a. Some benzene was retained in the product even after drying for severaf hours. Found: C, 55.9; H, 3.5; Cl, 4.6; Cr, 7.0; Rh, 12.8. Cak. for 0.33[c~H6]c~6H~~clc~~P*Rh : c, 55.8; H, 3.4; Cl, 4.6; Cr, 6.7; Rh, 13.3%. IR (mineral oil mull, Csl) v(C0) = 1995, 1970, 1905 cm-‘. IR of filtrate (benzene) v(C0) = 1988, 1966, 1905 cm-‘. 31P(‘H) NMR of filtrate (C,D,) 29.2 [d, J(P-Rh) = 132 Hz] plus minor resonances at 29.0 [d, J(P-Rh) = 133 Hz] and 28.7 ppm [d, J(P-Rh) = 133 Hz]. Pr~par~tjo~ of ~[~‘-l,~(PPh*~~~~H~Cr(CO)*PBu*~] Rh(CO)Cl 1, (lob)
A solution of 179 mg (0.24 mmol) [$-1,4(PPh2)2C6H,]Cr(C0)2(P13un3) in 2 cm3 of benzene was added dropwise to a solution of 39 mg (O.l2 mmol) [RhCl(CO)~]~ in 1 cm3 of benzene. The solution turned red with visible gas evolution. After 4 h the solvent was removed under reduced pressure and the residue washed with pentane (2 x 5 cm3) and dried under reduced pressure to give 187 mg (84%) of lob as an orange solid. Found: C, 58.7; H, 5.7; Cl, 3.9; Cr, 5.5; Rh, 10.1. CaIc. for C4jHj1ClCT03P&h: C, 58.5; H, 5.6; Cl, 3.8; Cr, 5.6 ; Rh, 11.1%. IR (benzene) 1987 (s), 1892 (vs), 1845 (s) cm- ‘. ‘H NMR (C6D6) 6 7.91 (br, 8H, PPh2), 7.20 (br, 4H, PPh& 7.07 (br, 8H, PPh& 5.55 (v br, 4H, C,H& 2.32 (br, 6H, C~~CH~CH*CH3~, 1.52 (br, 6H, CH&N&ZH,CH,), 1.36 (br, 6H, CH,CH&HL7CH3), 0.79 (br, 9H, CH,); 31P NMR (toluene-ds, 50°C) 6 48.3 (s, PBun3), 23.8 [d, J(P-Rh) = 128 Hz, PPh2]; in dichloromethane/ toluene-d, (3/l, v/v) at - 60°C 52.9 (s), 31.5 [dd,
Synthesis of new metalloligands J(P-P)=356 Hz, f(P-Rh) J(P-Rh) = 128 Hz].
= 128 Hz], 20.7 [dd,
Ack~~~ie~ge~e~~~-MEW wishes to thank the donors of the Petroleum Research Fund, administered by the American Chemical Society for partial funding of this research. LL ackuow~~ges partial support of this work through a grant from the Undergraduate Research Of&e and the Department of Chemistry and Biochemistry at Utah State University. RTB thanks T. J. Onley for expert technical assistance. Suppleme~tury material avai~abl~One plot of In k versus I IT (one page).
linear Arrhenius
REFERENCES 1. E, 0. Fischer and K. Ofele, Z. ~a~u~f~r~~~., Tiel B
2.
3.
4. 5. 6. 7.
1958, 13,458 : B. Nicholls and M. C. Whiting, Proc. Chem. Sot. 1958, 152; G. Natta, R, Ercoii and F. Calderazzo, C&m. I&. f958,40,287. (a) S. Top and G. Jaouen, J. ~rg~omet. Ckem. 1979, 182, 381; (bj C. A. L. Mahaffy and P. L. Pauson, Znorg. Synth. 1979, 39, 154 ; (c) G. R. Knox, D. G. Leppard, P. L. Pauson and W. E. Watts, J. &gem+ mef. Chem. 1972,34,347. We have recently prepared {q6-1,4-bis(CH,SO,) C,H,fCr(CO), indirectly through the reaction of (16-1,4-bis(OH)C6HsfC~C0)3 with methanesuipbonyl chloride. M. E. Wright, J. ~r~~~ornet. Chem. 1990,376,353. M. D. Rausch and R. E. Gloth, J. Or~~~rne~. Chem. 1978, 153, 59. M. F. Semmelhack, J. Bisaha and M. Czarny, J. Am. Chem. Sot, 1979,101,768. M. E. Wright, ~rgo~ometa~i~cs 1989,8,407. D. Seyferth and M. A. Weiner, f. Am. Chem. Sot. 1961, 83, 3583; D. Seyferth and L. G. Vaughn, J. Am. Chem. Sot. 1962, 84, 361; 3. Am. Chem. Sot. 1964, 86, 883. For a more recent application of this
329
reaction see: W. D. Wulff, G. A. Peterson, W. E. Bauta, K. Chart, K. L. Faron, S. R. Gilbertson, R. W. Kaesler, D. C. Yang and C. K. Murray, J. Org. C&em. 1986,51,279 and refs therein. 8. For example see: D. W. Macomber, W. P. Hart and M. D. Rausch, Adv. Organomet. Chem. 1982,21,1; M. E. Wright, ~rg~~~~e~~~~~c~1990, 9, 853 and refs therein. For $‘-arene ligands see: J. A. Heppert, J. Aube, M. E. Thomas-Miller, M. L. Milligan and F. Takusagawa, ~rg~ometailics 1990, 9, 727 and refs therein. 9. For a general treatment of ligand substitution on ~~6-arene~Cr(CO)~ complexes see. R. Davis and L. A. P. Kane-Maguire, Comprehe~~e ~r~~o~tQll~c Chem~try (Edited by G. Wilkinson. F. G. A. Stone and E. W. Abel), Vol. 3, pp. ~001-10~. Pergamon Press, Oxford (1982) and refs therein. IO. D. Seyferth and M, A. Weiner, J. Am. Chem. Sot. 1962,84,361. II. Org~~ometaIlic Polymers (Edited by C. E. Carraher Jr, J. Sheets and C. U. Pittman Jr). Academic Press, New York (1978) and refs therein. (2. Molecular modeling for rings of n = 3 (21 membered ring) and n = 4 (28 membered ring) indicated that these systems could be formed with no apparent ring strain. 13. For another illustration comparing the Cr(CO), and Cr(CO),(L) systems see: M. E. Wright, in ~~~~g~~jc and petal-Containjng Polymeric Mater&& (Edited by J. E. Sheats, C. E. Carraher Jr, C. U. Pittman Jr. M. Zeldin and B. Curteil), pp. 151-160. Plenum Press. New York (1991). 14. A. J. Gordon and R. A. Ford, The Chemists Companion. Wiley, New York (1972). 15. K. L. Jaura, H. S. Hundal and R. D. Handa, Znd. J. Chem. 1967,5,21 I. 16. J. A. McCleverty and G. Wilkinson, irnorg. Synth. 1966,8,211. 17. G. Giordano and R. H. Crabtree, inorg. Synth. 1979, 19,218.