Organometallics 1995, 14, 3762-3767
3762
Novel Ring Expansion Isomerism of a Fluorenylidenephosphonium Neil Burford," Jason A. C. Clyburne, Sergey V. Sereda, T. Stanley Cameron,* James A. Pincock, and Michael Lumsden Department of Chemistry, Dalhousie University, Halifxx, Nova Scotia B3H 4J3, Canada Received February 13, 1995@ The synthesis and conclusive characterization of a series of fluorenyl- and fluorenylidenetetraalkyldiaminophosphorus compounds (alkyl = ethyl and isopropyl) are described. The phosphines 6 are obtained by reaction of chlorodiaminophosphines with fluorenyllithium
and are quantitatively oxidized to the phosphorane 7 by reaction with cc4. Crystal MZ=P , structures of the isopropyl derivatives are reported. (Crystal data for 6a: C Z ~ H ~ ~ N 396.55, P21/n, a = 15.710(5) b = 9.66(1) c = 15.93(2)A, ,6 = 91.48(6)",V = 2417(7) Hi3, Z = 4, D,= 1.089 Mg/m3,R = 0.0538. For 7a: C Z E H ~ & ~ NM~= P ,431.00, P21/c, a = 8.69(1) A, b = 16.24(1) c = 17.16 (2)& ,8 = 96.0(1)",V = 2409(8) Hi3, 2 = 4, D,= 1.188 Mg/m3,R = 0.0481.) Contrary to previous reports (with Nc13) reaction of the phosphoranes with GaC13 gives the covalent complexes 7-GaCls. The ethyl derivative is stable, while the isopropyl derivative undergoes a quantitative isomerization to give 9-(diisopropylamino)-lO-(diisopropyliminio)-9,10-dihydro-9-phosphaphenanthrene tetrachlorogallate 5[GaC14] via a novel ring expansion rearrangement. (Crystal data for 5[GaC41: C25H3&14GaN2P, M = 607.08; P21/n; a = 9.884(3) A; b = 21.189(4) c = 14.639(4)A; ,6 = 95.12(2)";V = 3054(2) Hi3; 2 = 4; D,= 1.320 Mg/m3; R = 0.0393.)
A,
A,
A,
A;
Introduction The fluorenylidene unit is an attractive substituent for the development of new bonding environments offering both steric and electronic stabilizing features. Consequently, it has been used for the isolation of the first stable methylenegermene 1,l as well as compounds
1
the result of a halide ion abstraction from derivatives of fluorenylidenephosphoranes on the basis of spectroscopic data.4 These conclusions were refuted after comparison with the first structurally characterized example of an alkenephosphonium salt.5 We have re-examined two diamino-substituted phosphorus systems that have the potential t o adopt structure 4 and report observations that are consistent with a covalent formulation. Moreover, promotion of an ionic structure in a polar solvent facilitates a novel quantitative isomerism t o give the tricyclic iminiumphosphine salt 5[GaC141.
2 5
Experimental Section
containing low-coordinate environments for boron 22 and phosphorus 3.3 The first alkenephosphonium cations 4 (fluorenylidenephosphonium) were speculated as
Fluorene and 1.6 M butyllithium in hexanes (Aldrich)were used as supplied. ['Pr2NI2PC1 and [Et2Nl2PCl were prepared following literature procedures.6 GaC13 was sublimed under vacuum before use. Fluorenyllithium (0.25 M) was prepared in situ by adding BuLi in hexanes to a stirred solution ( 0 "C) of fluorene in ether. CHzClz and hexanes were dried over CaH2 and P 2 0 5 and stored in evacuated bulbs. Benzene was dried over sodiumhenzophenone, and CC14 was dried over PzO5. Solids were handled in a Vacuum Atmospheres nitrogen-filled
@Abstractpublished in Advance ACS Abstracts, July 1, 1995. (11 Couret, C.; Escudie, J.; Satge, J.; Lazraq, M. J.Am. Chem. Soc. 1987,109, 4411-4412. Lazraq, M.;Escudie, J.; Couret, C.; Satge, J.; Drager, M.; Dammel, R. Angew. Chem., Int. Ed. Engl. 1988,27,828829. (2) Glaser, B.; Noth, H. Angew. Chem., Int. Ed. Engl. 1986,24,416417.
(3)van der Knaap, T.; Bickelhaupt, F. Chem. Ber. 1984,117,915924. (4)Appel, R.;Schmitz, R. Chem. Ber. 1983,116, 3521-3523. ( 5 )Igau, A.; Baceiredo, A,; Griitzmacher, H.; Pritzkow, H.; Bertrand, G. J . Am. Chem. SOC.1989,111, 6853-6854. (6)King, R. B.; Sundaram, P. M. J . Org. Chem. 1984,49, 17841789.
3
4
0276-7333/95/2314-3762$09.00/0
0 1995 American Chemical Society
Organometallics, Vol. 14,No. 8, 1995 3763
Novel Ring Expansion Isomerism compd formula M cryst sizelmm3 syst space group alA blA CIA
DJMg m-3 F(OO0) plcm-' no. of measd reflns no. of unique reflns no. of obsd reflns [I > 3 d ) I no. of params refined lOOR 100R, goodness of fit max, min peak in difference maple k 3
Table 1. Table of Crystallographic Data 7a 0.20 x 0.30 x 0.40 monoclinic P21ln 15.710(5) 9.66(1) 15.93(2) 91.48(6) 2417(7) 4 1.089 864 1.210 3768 3619 1354 262 5.38 4.86 2.47 0.32, -0.18
drybox. Reactions were performed in an evacuated Torr) reactor using established procedures.' Melting points were recorded on a Fisher-Johns apparatus and are uncorrected. Elemental analyses were performed by Beller Laboratories, Gottingen, Germany. Infrared spectra were recorded as Nujol mulls on CsI plates with a Nicolet 510P spectrometer. NMR spectra were recorded with a Bruker AC-250 spectrometer or a Nicolet AMX 400 spectrometer in 5 mm flame-sealed Pyrex tubes. All chemical shifts are reported in ppm relative to external standards, 85% for 31P,and TMS for 'H and I3C. Preparative procedures and characterization data for each compound are described below. [iPr2N12P-Fluorenyl 6a. Fluorenyllithium was prepared in situ by slow addition of butyllithium in hexane (4.8 mL; 1.6 M) to fluorene (1.27 g, 7.64 mmol) in 30 mL of ether ( 0 "C). After it was stirred for 30 min, the bright yellow solution was added over ~ 1 min 0 to a stirred solution ( 0 "C) of ['Pr2N]2P-C1 in ~ 3 mL 0 of ether. Precipitation of LiCl occurred on warming to room temperature. Volatiles were removed in uacuo, the resulting solids were extracted with hexanes, and slow removal of the solvent gave pink crystals which were characterized as 6a: yield 2.78 g, 7.02 mmol, 92%, mp 120-122 "C. Anal. Calcd: C, 75.72; H, 9.40; N, 7.06. Found: C, 75.80; H, 9.37; N, 6.89. IR (cm-'1: 1343 m, 1297 s, 1192 m, 1175 s, 1155 m, 1117 m, 1092 m, 1018 m, 948 s, 865 m, 529 m, 520 s. NMR (CD2C12): 31P{1H},71; 'H, 7.86-7.27 (8 H, aromatic), 4.34 (s, lH), 3.58-3.35 (multiplet, 4 H), 1.17 ~ 12 H), 0.77 (d, 3 J =~7 Hz, ~ 12 H); '3C{'H}, (d, 3 J =~7 Hz, 126.7 (s), 126.5 (s), 126.3 (s), 119.7(~), 57.4 (d, 'Jpc = 35 Hz), 48.9 (d, 'Jpc = 13 Hz), 24.1 (d, 3 J p c = 7 Hz), 23.9 (d, 3Jpc = 7 Hz), quaternary carbons not observed. Reaction mixture: 31P{lH}, 71 (quantitative). [Et2N]zP-Fluorenyl6b. Prepared in the same fashion as 6a: yield, 1.27 g, 3.73 mmol, 50%, mp 121-123 "C. Elemental analysis not obtained, characterization made by comparison with 6a. IR (cm-I): 1939 w, 1901 w, 1373 w, 1345 w, 1290 s, 1189 s, 1010 s, 904 s, 791 m, 776 m, 688 m, 661 m, 636 m, 504 m, 476 w, 427 w, 411 w. NMR (CD2C12): 31P{1H},95; 'H, 7.827.24 (8 H, aromatic), 4.75 (d, 2 J =~4 ~ Hz, 1 HI, 3.31-3.18 (multiplet, 8 H), 1.14 (t, 3 J =~7 Hz, ~ 12 HI; 13C('H), 126.8, 126.6, 126.4, 119.7, 47.6 (d, 'Jpc = 21 Hz), 44.1 (d, 'Jpc = 17 Hz), 14.6 (d, 3 J p ~= 4 Hz), quaternary carbons not observed. [iPr2N]zP(C1)=Fluorenylidene7a. cc14 ( ~ mL) 1 was 0 of poured into a solution of 6a (1.4 g, 3.6 mmol) in ~ 2 mL pentanes. The clear solution stood for 2 days a t room tem(7) Burford, N; Muller, J; Parks, T. M. J. Chem. Educ. 1994, 71, -801-803.
C25H3&1NzP 431.00 0.35 x 0.20 x 0.15 monoc1inic P2 'IC 8.69(1) 16.24(1) 17.16(2) 96.0(1) 2409(8) 4 1.188 928 2.351 3757 3757 1437 263 4.81 4.51 2.04 0.24, -0.22
5[GaC14] C25H36C14GaN2P 607.08 0.30 x 0.20 x 0.50 monoclinic P21ln 9.884(3) 21.189(4) 14.639(4) 95.12(2) 3054(2) 4 1.320 1256 13.18 4677 4388 1729 299 3.93 3.71 1.73 0.46, -0.28
perature, forming yellow block crystals. The supernatant was decanted from the crystalline material, and the crystals were washed with a small amount of pentanes and characterized as 7a (0.47 g, 1.09 mmol, 30%); mp 207-209 "C (decomp).Anal. Calcd: C, 69.67; H, 8.42; N, 6.50. Found: C, 69.88; H, 8.38; N, 6.45. IR (cm-l): 1609 m, 1588 m, 1553 m, 1420 m, 1322 m, 1299 s, 1278 s, 1193 s, 1167 s, 1148 s, 1118 s, 1111 s, 889 m, 875 m, 855 m, 753 s, 694 s, 642 m, 599 m, 558 s, 542 s, 536 s, 525 m, 503 m, 469 s, 452 m, 425 m. NMR (CD2C12): 31P{1H}, 53; 'H (298 K), 8.33-7.31 (aromatic, 8 H), 3.84-3.60 (m, 4 H), 1.02 (d$JHH = 7 Hz, 12 H), 0.98 (d, 3 J = ~7 Hz, ~ 12 H); 13C{1H} (213 K), 140.7 (d, J p c = 21 Hz), 139.5 (d, J p c = 19 Hz), 130.7 (d, J p c = 18 Hz), 130.0 (d, J p c = 19 Hz), 122.8 (d, J p c = 29 Hz), 119.1 (d, J p c = 58 Hz), 118.2 (d, J p c = 68 Hz), 117.0 (d, J p c = 20 Hz), 66.3 (d, J p c = 201 Hz), alkyl region is broad, a t 293 K aryl region is broad, but alkyl region is sharp, 66.3 (d, J p c = 201 Hz), 50.0 (d, J p c = 4 Hz), 24.2 (d, J p c = 4 Hz), 23.4 (d, J p c = 4 Hz). Reaction mixture: 31P{1H),53 (quantitative). [Et2N]zP(Cl)=Fluorenylidene 7b. cc14 ( ~ mL) 1 was added to a solution of 6b (1.07 g, 3.14 mmol) in hexanes (25 mL), giving instantaneous precipitation. All volatiles were removed in uacuo and the yellow residue was recrystallized from benzene and characterized as 7b,yield 1.10 g, 2.93 mmol, 90%, mp 103-104 "C. Elemental analyses were not obtained, and characterization was made by comparison with 7a. IR (cm-I): 1610 m, 1588 m, 1557 w, 1421 s, 1356 s, 1326 s, 1289 s, 1234 m, 1203 s, 1153 s, 1115 m, 1095 m, 1061 s, 1035 s, 1022 s, 892 m, 788 s, 753 s, 704 s, 675 s, 597 w, 528 s, 504 m, 453 m, 422 m, 365 w, 332 w. NMR (CD2C12): 31P{'H}, 58; 'H, = 8.09-7.09 (aromatic, 8 H), 3.52-3.20 (m, 8 HI, 1.29 (t, JHH 7 Hz, 12 H); 13C{'H}, 124.4 ( s ) , 118.7 (SI, 117.8 (s), 64.5 (d, 'Jpc = 205 Hz), 40.8 (d, 'Jpc = 5 Hz), 13.5 (d, 3Jpc = 2 Hz), quaternary carbon nuclei were not observed. Reaction of [iPr2N2P(C1)=Flu~renylidene7a with GaCls. A solution of 7a (0.21 g, 0.47 mmol) in benzene ( ~ 2 0 mL) was added to a stirred solution of GaC13 (0.085 g, 0.47 mmol) in benzene ( ~ 2 mL) 0 in a 10 "C bath to give a white precipitate. After decantation of the solution, the solid was washed by back-distillation: mp 105 "C (decomp). IR (cm-'): 1305 m, 1195 m, 1165 m, 1149 m, 1140 m, 1110 m, 994 s, 972 s, 942 m, 799 m, 740 s, 681 m, 606 m, 558 m, 540 s, 366 s, 359 s, 345 s. NMR (CD2C12, -80 "C): 31P{1H}, 71; 13C and 'H exhibit broad unresolved signals in the regions of those reported above. Solid state CP/MAS 31PNMR 9.4 T: 72.2, 70.2,68.7 (quadrupolar I4N splitting). The white powder was (0.77 mmol) was dissolved in CH~C12/pentanes(75125, ~ 4 0 mL), and slow removal of solvent overnight yielded light pink crystals which were characterized as 9-(diisopropylamino)-10-
3764 Organometallics, Vol. 14,No. 8, 1995
Burford et al.
Table 2. Positional Parameters and B(eq) for 6a
Table 3. Positional Parameters and B(eq) for 7a
atom
atom
Y
X
0.4928(1) 0.5131(6) 0.5172(3) 0.5662(3) 0.3919(4) 0.3835(4) 0.4033(5) 0.3921(5) 0.3589(6) 0.3363(5) 0.3484(4) 0.3268(4) 0.2877(4) 0.2700(5) 0.2913(5) 0.3319(4) 0.3497(4) 0.5359(5) 0.4670(5) 0.6234(5) 0.5035(5) 0.5617(5) 0.4131(6) 0.6091(6) 0.5539(5) 0.6617(5) 0.5962(6) 0.6838(5) 0.5774(5)
0.1318(2) 0.147(1) -0.0137(5) 0.2555(5) 0.1997(6) 0.2962(7) 0.2748(8) 0.382(1) 0.507(1) 0.5312(7) 0.4232(7) 0.4139(8) 0.5115(8) 0.474(1) 0.346(1) 0.2483(8) 0.2828(8) -0.0323(9) -0.1056(8) -0.0938(8) -0.1377(9) -0.1617(8) -0.1671(7) 0.2949(9) 0.3775(9) 0.189(1) 0.3277(8) 0.291( 1) 0.4789(8)
2
B(ed
0.6900(1) 0.7807(5) 0.7456(3) 0.7092(3) 0.7413(4) 0.8160(4) 0.9000(5) 0.9566(4) 0.9308(5) 0.8477(5) 0.7906(4) 0.7007(4) 0.6476(5) 0.5656(6) 0.5364(5) 0.5881(5) 0.6722(4) 0.8350(5) 0.8842(4) 0.8550(5) 0.6970(6) 0.6268(5) 0.6720(5) 0.6322(5) 0.5726(5) 0.5923(5) 0.7836(5) 0.8140(5) 0.7875(5)
(diisopropyliminio)-9,lO-dihydro-9-phosphaphenanthrene tetrachlorogallate 5[GaC14] (0.39 g, 0.64 mmol, 83%), mp 166-
Crystals of 5[GaC141,6a, and 7a, were obtained as described in the preparations of the compounds and were selected and mounted in Pyrex capillaries in the drybox. Unit cell parameters were obtained from the setting angles of a minimum of 16 carefully centered reflections having 28 > 20"; the choice of space groups was based on systematically absent reflections and confirmed by the successful solution and refinement of the structures. All pertinent crystallographic data are summarized in Table 1. Data were collected a t room temperature (23 f 1 "C) on a Rigaku AFC5R diffractometer using the 0-28 scan technique, and the stability of the crystals was monitored using three
0.1301(1) 0.1962( 1) 0.1710(3) 0.2946(3) 0.1699(4) 0.2204(5) 0.3015(5) 0.3328(5) 0.2874(8) 0.2087(7) 0.1748(6) 0.0890(5) 0.0937(6) 0.0246(7) -0.0464(7) -0.0526(6) 0.0140(5) 0.3156(4) 0.3814(5) 0.3355(5) 0.3494(4) 0.4333(4) 0.3600(5) 0.1495(4) 0.2220(5) 0.0743(5) 0.1599(4) 0.2088(5) 0.0698(5)
2
B(ea)
0.4849(1) 0.3821(1) 0.3596(3) 0.4094(3) 0.3177(4) 0.2562(4) 0.2305(4) 0.1663(5) 0.1275(5) 0.1515(6) 0.2140(4) 0.3105(4) 0.2474(5) 0.2272(6) 0.2689(7) 0.3287(6) 0.3505(5) 0.4513(4) 0.4112(5) 0.5366(5) 0.4102(4) 0.3742(5) 0.4886(4) 0.2787(4) 0.2234(4) 0.2430(5) 0.4209(4) 0.4029(4) 0.4338(5)
Table 4. Positional Parameters and B(eq) for 5lGaCLI
atom 167 "C. Anal. Calcd: C, 49.46; H, 5.98; N, 4.61. Found: C, 49.23; H, 6.08; N, 4.54. IR (cm-'1: 1582 s, 1195 s, 1167 s, 1138 s, 1113 s, 1017 s, 964 s, 874 m, 785 m, 758 s, 738 s, 687 m, 678 m, 517 m, 489 m, 456 m, 372 s. NMR (CD2C12, -80 C): 31P{1H},22; 'H, 8.03-7.17 (aromatic, 8 HI, 4.79 (m, 1HI, 4.42 (m, 1 HI, 3.22 (m, 1 H), 2.74 (m, 1 HI,2.01 (d, 3 J =~6.4~Hz), 6.1 HZ), ~ 1.44 (d, 3 J =~6.8~HZ), 1.39 (d, 3 J ~ ~ 1.52 (d, 3 5= ~ = 6.0 Hz), 1.07 (d, 3 J =~5.9~ HZ), 0.97 (d, 3 J =~5.9~Hz), ~ Hz), -0.04 (d, 3 J =~ 6.0 ~ HZ) total 0.48 (d, 3 J =~ 5.7 integration 24 H; 13C{lH}, 213.9 (d, lJpc = 89.2 Hz, C=N), complex and unresolved. Reaction Mixtures: 31P{lH}, 22 (quantitative). 31P(1H}NMR studies of reactions between 7b and GaCl3 in CHzClz reveal a single phosphorus-containing product (with a signal at b 72) which remains unchanged for more than 1 month, but attempts a t isolation produced oily materials. NMR studies of reactions between 7 and HOS02CF3 in CD2Clz indicate quantitative formation of [I1Pr2N12P(C1)31P{lH}, 71, and [[Et2N12P(Cl)fluorenyll8a[OSO~CF~1, fluorenyll8b[OSO2CF31: 31P{lH}, 72; lH, 7.92-7.33 ( 8 H, aromatic), 5.74 (d, ' J P H= 18 Hz, 1 H), 3.17-2.93 (m, 8 H), 0.97 (t,J = 7 Hz, 12 H); 13C{'H}, 130.7(d, Jpc = 3 Hz), 128.7 (d, Jpc = 4 Hz), 127.l(d, Jpc = 4 Hz), 121.6 (d, Jpc = 2 Hz), 50.4 (d, lJpc = 89 Hz), 42.1 (s), 12.5 (SI, 12.4 (s). Multiplicity analysis (JMOD) confirms the assignment of the methine center.
X-ray Crystallography
Y
X
0.9978(2) 1.0162(2) 1.1880(6) 1.0098(6) 0.8624(8) 0.7895(9) 0.818(1) 0.728(1) 0.607(1) 0.578(1) 0.669(1) 0.787(1) 0.666(1) 0.570(1) 0.597(1) 0.715(1) 0.809(1) 0.872(1) 0.766(1) 0.909(1) 1.1459(9) 1.107(1) 1.243(1) 1.2213(9) 1.200(1) 1.137(1) 1.3229(9) 1.4648(9) 1.359(1)
X
Y
2
B(ea)
0.2568(1) -0.00658(5) 0.26644(7) 0.2365(3) -0.0639(2) 0.3855(2) 0.2012(2) 0.0900( 1) 0.2931(2) 0.4651(2) -0.0077(1) 0.23112(2) 0.1238(3) -0.0443( 1) 0.1553(2) 0.8266(2) -0.2057(1) 0.1404(1) 0.7488(6) -0.3325(3) 0.1787(4) 0.7465(6) 00.1629(3) 0.0566(4) 0.7092(7) -0.2749(4) 0.1591(5) 0.5627(7) -0.2562(3) 0.1576(6) 0.4624(8) -0.2810(4) 0.0950(6) 0.3305(9) -0.2585(4) 0.0964(7) 0.2998(8) -0.2130(5) 0.1561(7) 0.399(1) -0.1877(4) 0.2167(6) 0.5350(8) -0.2075(4) 0.2187(6) 0.6480(8) -0.1763(3) 0.2777(5) 0.624(1) -0.1500(4) 0.3617(7) 0.723(1) -0.1170(4) 0.4147(6) 0.850(1) -0.1109(4) 0.3832(6) 0.8773(8) -0.1382(4) 0.3006(6) 0.7777(7) -0.1706(4) 0.2462(5) 0.6540(8) -0.1086(4) 0.0679(5) 0.5203(9) -0.1140(4) 0.0073(6) 0.722(1) -0.0459(4) 0.0533(6) 0.788(1) -0.1726(4) -0.0375(6) 0.739(1) -0.2355(5) -0.0751(6) 0.939(1) -0.1648(6) -0.0434(7) 0.8964(8) -0.3527(4) 0.1835(6) 0.9539(8) -0.3504(4) 0.0901(6) 0.9838(8) -0.3184(4) 0.2578(6) 0.6530(8) -0.3824(4) 0.2060(7) 0.649(1) -0.4362(4) 0.1388(8) 0.692(1) -0.4026(5) 0.3045(8) standard reflections; no significant decay was observed. Data were corrected for Lorentz and polarization effects; azimuthal scans of several reflections indicated no need for an absorption correction. Structures were solved by direct methods8 which revealed the positions of all non-hydrogen atoms. The non-hydrogen (8) Busing, W. R., Martin, K. 0.; Levy, H. A. ORFLS. A Fortran crystallographic least squares program. Report ORNL-TM-305; Oak Ridge National Laboratory: Oak Ridge, TN, 1962.
Novel Ring Expansion Isomerism
Organometallics, Vol. 14, No. 8,1995 3765
atoms were refined anisotropically. All of the hydrogen atoms were placed in geometrically calculated positions with a C-H distance of 0.95 A. Their positions were not refined, and they were assigned fixed isotropic temperature factors with a value of 1.2 x B(eq)of the atom to which it was bonded. The function , the minimized by full-matrix least squares was Z U ( A ~ F I )w~ is weight derived from counting statistics. Neutral atom scattering factors for non-hydrogen atoms were taken from Cromer and Waber: and the scattering factors for hydrogen atoms were taken from Stewart, Davidson, and Simpson.lo Anomalous dispersion effects were included in Fcalcd;ll the values for Af‘ and A 7 were those of Cromer.12 All calculations were performed using the T E X S W 3 crystallographic software package of Molecular Structure Corporation. In the structure of 6a the phosphorus is pyramidal with interbond angles C(l)-P(l)-N( l ) , 103.8(3)”;C(l)-P(l)-N(2), 104.5(3)”,and N( l)-P(l)-N(2), 110.4(3)”. It is disordered with a second position P(2), roughly the mirror image of the pyramid, which gives the corresponding interbond angles to C(1), N(1), and N(2) of 100.0(5)”, 96.1(4)”, and 108.4(5)”, respectively. If the occupation of the two disordered sites P(l), P(2) is 80%:20%, then the thermal parameters of the two disordered phosphorus atoms are approximately equal (B(eq) = 3.5(1) and 3.8(5), respectively). The phosphorus atom can occupy these two disordered positions with minor adjustments of the position of C(l), N(1), and N(2). In order to maintain the correct valence angles at C(l), NU), and N(2) (P(l)-N(l)C(14), etc.), there must be some significant adjustment in the position of at least one of the other substituents at these atoms. However, with disorder occupancies in the ratio of 4:1, these adjustments could not be reliably detected, and nonbonded contacts (particularly to C(14) and C(23))to atom P(2) should be disregarded.
W
Figure 1. ORTEP view of [‘Pr2N]2P-fluorenyl6a.
Results and Discussion
Fluorenylphosphine and Fluorenylidenephosphorane Derivatives. The fluorenylphosphoruslinkage is readily obtained by the quantitative reaction of to give chlorodiaminophosphineswith fluorenyllithi~m,~ the fluorenyldiaminophosphines 6 as stable isolable
6
solids. Spectroscopic data are consistent with the observed crystal structure of 6a illustrated in Figure 1, which shows a tetrahedral geometry for C(1) of the fluorenyl fragment. The average P-C bond length (1.99(7) A> is comparable with those observed in pentamethylcyclopentadienylphosphorus compounds (9) Cromer, D. T.; Waber, J. T. International Tables for Crystallography; The Kynoch Press: Birmingham, England, 1974; Vol. IV, Table 2.2A. (10) Stewart, R.F.,Davidson, E. R.; Simpson, W. T. J. Chem. Phys. 1965,42,3175-3187. (11) Ibers, J. A.; Hamilton, W. C. Acta CrystaUogr. 1964,17, 781782. ( 12) Cromer, D. T. International Tables for X-ray Crystallography; The Kynoch Press: Birmingham, England, 1974; Vol. IV,Table 2.3.1, pp 149- 150 (Present distributor Kluwer Academic Publishers, Dordrecht.). (13) TEXSAN-TEXRAYSingle-Crystal StructureAnalysis Package, Version 5.0; Molecular Structure Corporation: The Woodlands, TX, 1989.
Figure 2. ORTEP view of [‘Pr2N]2P(Cl)-fluorenylidene 7a. Important bond lengths (Hi> a n d angles (deg): P(1)C(l), 1.698(7);P(l)-Cl(l), 2.085(3);P(1)-N(l), 1.634(6); P(l)-N(2), 1.668(5); C1(l)-P(l)-N( l), 102.9(2); C1(1)P(l)-N(2), 104.4(2);Cl(l)-P( 1)-C( l),107.3(3);N(1)-P( 1)N(2), 111.4(3);N(l)-P(l)-C(l), 117.3(3);N(2)-P(l)-C(l), 112.1(3);P(l)-C( 1)-(2), 126.4(6);P(1)-C( l)-C(8), 126.5(6); C(2)-C(l)-C(8), 106.9(6);C1( 1)-P( l)-C(l)-C(2) torsion angle, 151.5(6)”; C1( 1)-P( 1)-C( 1)- C(8) torsion angle, -33.7( 7)”. (Cp*P=PCp*, 1.893(7)and 1.883(7)A,14 [Cp*-P-N(H)). Although each of these tBu][AlC14], 1.990(2) compounds exhibits ring whizzing by NMR spectroscopy in solution and in the solid state, the phosphorus atom is attached to a specific out-of-plane distorted carbon center of the Cp* ring indicating a monohapto interaction. Recognizing fluorenyl as a derivative of cyclopentadienyl, 6a may be considered an intimate ion-pair coordination complex involving the fluorenyl anion and the tetraisopropyldiaminophospheniumcation, [‘PrN2P+. However, the 31PNMR chemical shifi for 6a (71 ppm) is substantially upfield from that of the free cation ([(iPr2N)2Pl[GaC14]31P,3 13 ppm)16 but is comparable with the DBU complex ([(‘Pra)2PDBUI[PFs],108 ppm).17 (14) Jutzi, P Meyer, U.; Krebs, B.; Dartmann, M. Angew. Chem., Int. Ed. Engl. 1986,25, 919-921. (15) Gudat, D.; Nieger, M.; Niecke, E. J. Chem. SOC.,Dalton Trans. 1989,693-700.
3766 Organometallics, Vol. 14,No. 8,1995
Burford et al. Scheme 1
/ Figure 3. ORTEP view of cation 5. Important bond lengths (A) and angles (deg): P(l)-N(2), 1.667(6);P(1)C(l>, 1.905(8);P(l)-C(13), 1.822(8);N(1)-C(l), 1.305(9); N(2)-P(l)-C(l), 105.6(3);N(2)-P(l)-C(l3), 105.0(3);C(1)P(l)-C(13), 88.8(3);I:angles at N(1), 359.9(6);Z angles at N(2), 359.2(5); C angles at C(1), 359.8(6).
GaC: 1
GaCIF
& .
\
, o \
Both derivatives of 6 are quantitatively oxidized by CC4, as described by Appel,18to give the phosphoranes 7. lH and 13CNMR spectra show two types of isopropyl
/
GaCIF
5
7
groups for 7a, implying restricted rotation about the N-P bond. At room temperature a single line is observed for the ethyl groups of 7b, but this broadens on cooling implying a slowing down of a dynamic process, possibly a restriction of the N-P bond rotation. The X-ray crystal structure of 7a (Figure 2) confirms the steric crowding and reveals a short P-C bond (1.698(7) A),typical of methylenephosphoranes (tB~2(C1)P=CPh2,19 1.673(5), 1.667(5), and 1.668(5) A; Ph3P=C(~yclopropyl),~~ 1.696(6) A; 'Pr~P=cMe2,~l 1.731(3)A). The ylidic carbon center is planar (sum of the bond angles, 360"), consistent with cyclopentadiene substituted phosphoranes.22 Interestingly, the chlorine atom of 7a is almost in the plane defined by the fluorenylidene substituent (Cl-P-Cl-C2 torsion, 151.5(6)"; Cl-P-Cl-cS torsion, -33.7(7)"). Such a n (16) Burford, N.; Losier, P.; Kyrimis, V.; Macdonald, C.; Bakshi, P. K.; Cameron, T. S. Inorg. Chem. 1994,33, 1434-1439. (17) Reed, R.; Reau, R.; Dahan, F.; Bertrand, G. Angew. Chem., Int. Ed. Engl. 1993, 32, 399-401. (18) Appel, R.; Peters, J.; Schmitz, R. 2. Anorg. AZZg. Chem. 1981, 475, 18-26. (19)Grutzmacher, H.; Pritzkow, H. Angew. Chem., Int. Ed. Engl. 1992,31,99-101. (20)Schmidbaur, H.; Schier, A.; Milewski-Mahrla, B.; Schubert, U. Chem. Ber. 1982, 1155, 722-730. (21) Schmidbaur, H.; Schier, A.; Frazao, C.; Muller, G. J . Am. Chem. SOC. 1986, 108, 976-982. (22) Bacharach, S. M.; Nitsche, C. I. In The Chemistry of Orgunophosphorus Compounds; Hartley, F. R., Ed; Wiley & Sons: Toronto, 1994; Vol. 13, p 280.
a
R
= 'Pr.
arrangement precludes interaction between the n-network of the fluorenylidene and the CPorbital of the P-C1 bond (hyperconjugation), as speculated for other methylenephosphoranes tBu2(C1)P=CPh2, 2.195(2), 2.228(2), and 2.235(2)A,19 and is manifest in the short P-C1 bond of 2.085(3) A. FluorenylphosphoniumDerivatives. Reactions of 7 with GaC13 produce white solids, which are quantitatively precipitated from benzene and are soluble in polar solvents such as CH2C12. In contrast to previous observations for reactions of 7a with and the ionic structures observed for [tBu2P=C(SiMe3)21[MC14] from the reaction of tBu2(C1)P=C(SiMe& with 31P NMR chemical shifts in solution (7a-GaCl3, 71
7-GaC13
ppm; 7b-GaCl3, 72 ppm) and in the solid state (7aGaCls, 70 ppm) are comparable to the covalent phos(23) Grutzmacher, H.; Pritzkow, H. Angew. Chem., Znt. Ed. Engl. 1991,30, 709-710.
Novel Ring Expansion Isomerism
Organometallics, Vol. 14,No. 8, 1995 3767
phorane 7 precursor (53 ppm) and are substantially isopropyldiamino substituent from phosphorus to the upfield from those of the established phosphonium unique carbon of the fluorenyl substituent, and a cations (cf. [(‘PrzN)zP=C(SiMe3)21+, 130 ~ p m ; ~ reductive ring insertion of the phosphorus center into the Cl-C2 bond of 7. In Scheme 1, we provide a [tBu2P=CPh2]+, 183 ppmlg). Although it has not been possible to obtain informative lH and 13CNMR data for speculative mechanism with 4 undergoing a reductive 7a-GaCla or 7b-GaCla and recrystallization has been cyclization through an ammonium center followed by a unsuccessful, we speculate the formation of coordination two-step insertion of the resulting phosphine center into complexes involving a carbon-gallium coordinate bond, the Cl-C2 bond via an arenium intermediate. It similar t o those reported for other ylidekewis acid should be noted that the oxime of fluorenone undergoes adducts.24 Further convincing support for this phosan analogous ring expansion in the Beckmann rearphonium assignment is provided by the reactions of 7 ~-angement.~~ with HOS02CF3 which give the corresponding phosphoThe isomerization of cation 4 is consistent with nium cations 8 exhibiting identical 31PNMR chemical previous observations for tricoordinate phosphonium shifts (8a, 71 ppm; 8b,72 ppm). cations which undergo intramolecular electrocyclic ring closure,26 adopt “covalent alternative’’ structures27or rearrange in other ways.lg The quantitative rearrangement described here is unique in terms of the nature of the bonds broken and formed and is unprecedented in the chemistry of phosphorus ylides despite extensive studies.24 8
Isomerism of a Fluorenylphosphonium. Solutions of 7a-GaCk in CH2C12 quickly become red, and a new 31PNMR signal appears a t 21 ppm coincident with the loss of the signal a t 71 ppm (reaction complete within 8 h). A red crystalline material isolated in high yield has been characterized as the tetrachlorogallate salt of the tricyclic iminumphosphine 5. A crystallographic view of the cation is shown in Figure 3. The salt is isomeric with 7a-GaCk and is the result of heterolytic cleavage of the C-Ga and P-Cl bonds with subsequent formation of GaC14-, a 1,3-shift of a tetra124)Ylides and Imines of Phosphorus; Johnson, A. W., Ed.; Wiley: New York, 1993;p 153.Schmidbaur, H.; Fuller, H.-J.; Kohler, F. H. J . Organomet. Chem. 1975,99,353-357. Alcaraz, G.; Reed, R.; Baceiredo, A.; Bertrand, G. J . Chem. Soc., Chem. Commun. 1993,1354-1355.
Acknowledgment. This work has been funded by the Natural Sciences and Engineering Research Council of Canada. We thank the Atlantic Region Magnetic Resonance Centre for the use of instrumentation. Supporting Information Available: Tables of positional parameters, anisotropic thermal parameters, and intramolecular bond distances and angles for [’PrzNIzP-fluorenyl 6a, [lPrzN]zP=-fluorenylidene 7a, and 9-(diisopropy1amino)-10(diisopropyliminio)-Q,lO-dihydro-Q-phosphaphenanthrene tetrachlorogallate 5[GaC14] (34 pages). Ordering information is given on any current masthead page.
OM9501182 (25)Moore, F.J.;Huntress, E. H. J . A m . Chem. SOC.1927,49,26182624. (26)Heim, U.;Pritzkow, H.; Fleischer, U.; Grutzmacher, H. Angew. Chem., Int. Ed. Engl. 1993,32,1359-1361. (27)Burford, N.: Spence, R. E. v. H.: Richardson, J. F. J . Chem. Soc., Dalton Trans. 1991, 1615-1619.
