Organometallics 1995,14, 3603-3606
3603
Synthesis, Structure, and Reactivity of the First Phosphaazaallene-Metal Complex John B. Alexander and David S. Glueck* 6128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755
Glenn P. A. Yap and Arnold L. Rheingold Department of Chemistry, University of Delaware, Newark, Delaware 19716 Received February 13, 1995@ Summary: The first phosphaazaallene metal complex, Cp;NbCCl)[~-CN,C)-P~CPMes*l[3; Cp' = C&SiMe3, Mes" = 2,4,6-(t-Bu)3C&ld,was prepared from Cp'fibCl and the cumulene. Spectroscopic and crystallographic characterization of 3 and some transformations of the complexed phosphaazaallene are described.
From hard-soft considerationss and the bulk of the Mes* group, coordination of Nb t o N or the N=C bond rather than to P or the P-C bond is predicted. The 31P NMR chemical shift of the phosphaazaallene changes from -106 to 14.3 ppm on coordination; the lack of broadening of the 31Psignal by the 93Nb quadrupoleg suggests the phosphorus is not coordinated. The coordination chemical shift of the central allene carbon from Introduction 200.8 to 171.5 ppm and the change in& for this carbon Phosphaazaallenes RP-C-NR are reactive molfrom 67 to 155 Hz are consistent with n(N,C) coordination. The IR spectrum shows a signal at 1505 cm-' ecules' which could conceivably bind t o a transition which may be assigned to an uncomplexed P-C group. metal either in a n (C,N or C,P) or in a (T (N or P) fashion. Cowley has shown that WL4C12 (L= PMePh2) The n(N,C) coordination of Mes*P=C=NPh in 3 was can cleave the P-C bond in Mes*P=C-NPh [l,Mes* confirmed by X-ray crystallography (Figure 1). Crystal, = 2,4,6-(t-Bu)3CsHzI2to generate the phosphinidene data collection, and refinement parameters are given complex trans-LzWCl~(CNPh)(PMes*).~ We recently in Table 1. Atomic coordinates and equivalent isotropic described the related reaction of 1with Rh(PCy3)zCl(Cy displacement coefficients are given in Table 2, while = cyclo-CsH11), which gives trans-Rh(PCy3)~Cl(CNPh) selected bond lengths and angles are found in Tables and the phosphaindan [ ~ , ~ ( ~ - B u ) ~ C & ( ~ - C M ~ ~ C H ~ P H ) IComplexation of 1'0 to Nb causes an increase in 3-4. (2): presumably via intramolecular decomposition of the the C-N bond length (1.209(4) to 1.301(23) A) and a free phosphinidene M ~ S * PHowever, .~ the coordination decrease in the N-C-P bond angle (171.1(2) to chemistry of these cumulenes has been otherwise ne156.2(13)"). The isoelectronic ketenimine complex, glected. We report here the synthesis of the first Cp'2Nb(C1)[v2-(N,C)-PhNCCPh21,11 has a longer Nb-N phosphaazaallene-metal complex Cp'2Nb(C1)[v2-(N,C)bond than in 3 (2.140(4)A vs 2.075(12) A)and a smaller PhNCPMes*l(3, Cp' = C5&SiMe3), its characterization N-C-C bond angle than the N-C-P bond angle in 3 by spectroscopic methods and by X-ray crystallography, (140.0 (4)" vs 156.2 (14)"). and a brief survey of its reactivity (Scheme 1). Photolysis of 3 in either benzene or THF with a Hg lamp forms Cp'zNbC1(CNPh)12(4) and phosphaindan 2. Monitoring the reaction in THF by 31PNMR showed Results and Discussion that this transformation does not occur at the metal center. Instead, irradiation causes dissociation of 1from As reported for other heterocumulenes,61reacts with 3; the free phosphaazaallene is then converted to 2 as Cp'zNbC17 t o form complex 3 as red air-stable crystals, previously reported for the analogous phosphaketene which are thermally stable in solution, remaining M ~ s * P = C - O ~and ~ as confirmed by control experiunchanged on heating t o 80 "C in THF for 1 week. ments. The isocyanide formed is trapped by Cp'2NbCl to give 4. @Abstractpublished in Advance ACS Abstracts, June 1, 1995. (1)Appel, R.; Knoll, F. Adu. Inorg. Chem. 1989, 33, 259-361. Adding HBF4.OMe2 to 3 in petroleum ether gives (2) Yoshifuji, M.; Toyota, K.; Shibayama, K.; Inamoto, N. Tetrahe(51, white {C~'ZN~(C~)[~~-(N,C)-P~N==CPHM~~*~}B dron Lett. 19E4,25, 1809-1812. the first example of a phospha-imino acyl complex. The (3)Cowley, A. H.; Pellerin, B.; Atwood, J. L.; Bott, S. G. J. Am. Chem. Soc. 1990,112,6734-6735. P-H bond is observed in the 31PNMR spectrum (6 (4) (a) Cowley, A. H.; Pakulski, M. Tetrahedron Lett. 1984,25,21252126. (b) Yoshifuji, M.; Sato, T.; Inamoto, N. Chem. Lett. 1988, 17351738. ( 5 ) David, M.-A.; Paisner, S. N.; Glueck, D. S. Organometallics 1996, 14, 17-19. (6) (a) Antinolo, A.; Fajardo, M.; Jalon, F. A.; Lopez Mardomingo, C.; Otero, A.; Sanz-Bernabe, C. J. Organomet. Chem. 1989,369,187196. (b) Halfon, S. E.; Fermin, M. C.; Bruno, J. W. J.Am. Chem. Soc. 1989, 111, 5490-5491. (c) Antinolo, A.; Fajardo, M.;Lopez Mardom-
ingo, C.; Otero,A.; Mourad, Y.;Mugnier, Y.; Sanz-Aparicio, J.; Fonseca, I.; Florencio, F. Organometallics 1990,9,2919-2925. (d)Antinolo, A.; Garcia-Lledo, S.; Martinez de Ilarduya, J.; Otero, A. J. Organomet. Chem. 1987,335,85-90. (7) See: (a)Reference 6d. (b) Fermin, M. C.; Hneihen, A. S.; Maas, J. J.; Bruno, J. W. Organometallics 1993, 12, 1845-1856.
(8) Pearson, R. G. Inorg. Chem. 1988,27, 734. (9) Antinolo, A.; Gomez-Sal, P.; Martinez de Ilarduya, J.; Otero, A.; Royo, P.; Martinez Carrera, S.; Garcia Blanco, S. J. Chem. Soc., Dalton Trans. 1987, 975-980. (10) Yoshifuji, M.; Niitsu, T.; Toyota, K.; Inamoto, N.; Hirotsu, K.; Odagaki, Y.; Higuchi, T.; Nagase, S. Polyhedron 1988, 7, 2213-2216. (11) Antinolo, A.; Fajardo, M.; Lopez Mardomingo, C.; Otero, A.;
Mourad, Y.; Mugnier, Y.; Sanz-Aparicio, J.; Fonseca, J.; Florencio, F. Organometallics 1990, 9, 2919-2926. (12) Martinez de Ilarduya, J. M.; Otero,A.; Royo, P. J. Organomet. Chem. 1988,340, 187-193. (13) Cowley, A. H.; Gabbai, F.; Schluter,R.; Atwood, D. J.Am. Chem. SOC.1992, 114, 3142-3144.
0276-7333/95/2314-3603$09.00/00 1995 American Chemical Society
3604 Organometallics, Vol. 14, No. 7, 1995
Notes
Scheme 1 Mes'P=C=NPh (1) Cp'*NbCI(CNPh) (4)
+
I
Cp'2NbCI
L
J
Table 1. Structure Determination Summary empirical formula color; habit cryst size cryet system space group unit cell dimens
Crystal Data C41HsoClNNbPSiz red block 0.10 x 0.20 x 0.35 mm3 monoclinic
P2 1Ic
a = 15.361(8)A, b = 18.898(8)A, c = 31.849(9)A, = 98.03(6)"
9155(3)A3 8 fw 782.4 D(ca1cd) 1.140 g/cm3 abs coeff 0.437 mm-l 3296 F(000) Data Collection m a c t o m e t e r used Siemens P4 radiation Mo Ka (1= 0.710 73 A) 296 K temp monochromator highly oriented graphite cryst 28 range 4.0-45.0' scan type Wyckoff scan speed variable; 8.37-29.30"lmin in w scan range ( w ) 1.00" plus Ka separation bckgd measment stationary cryst and stationary counter at beginning and end of scan, each for 50.0% of tot. scan time std reflcns 3 measd every 197 reflcns -15 I h I 15,O I k I 19,O 5 1 5 32 index ranges reflcns collcd 10 747 independent reflcns 10514 (Rint = 2.41%) 6092 (F > 4.OdF)) obsd reflcns NIA abs COR Solution and Refinement system used Siemens SHELXTL PLUS (PCVersion) solution direct methods refinement method full-matrix least squares quantity minimized Zw(F0 - FCY absolute structure NIA extinctn corr NIA H atoms riding model, fixed isotropic U weighting scheme w-1 = a2(F) 0.001oFI no. of params refined 763 final R indices (obsd data) R = 9.61(F) 0.001OF no. of params refined 763 final R indices (obed data) R = 9.61%,WR= 12.53% R indices (all data) R = 15.07%,WR= 14.22% goodness-of-tit 2.22 largest and mean 610 0.331, 0.011 data-to-param ratio 8.0:l largest d S peak 1.08 e A-3 largest diff hole -0.76 e A-3 V
z
u
c1391
Figure 1. ORTEP diagram of complex 3.The figure shows one of the two independent but chemically equivalent molecules found in the unit cell.
-37.4, d, 'JPH = 302 Hz) and the 'H NMR spectrum (6 7.32, 'JPH = 302 Hz). Exchange with D2O gives { [Cp'2Nb(Cl)(PhN=CPDMes*IBF4} (SD), (JPD= 44.3 Hz),14 confirming the unusual 'H N M R shift for the acidic P-H proton. Deprotonation of 5 with 1equiv of potassium tert-butoxide affords 3 quantitatively by 31P Nh!IR. Further studies of the reactivity of 3 and 5 with small molecules, and of related phosphacumulene complexes, are currently under way. Experimental Section General Experimental Details. All manipulations were carried out under a nitrogen atmosphere using either standard Schlenck apparatus or a glovebox. Solvents were distilled from sodium and benzophenone (toluene, THF, ether, petroleum ether) or from CaHz (methylene chloride) and stored under nitrogen in ampules until needed. IR spectra were recorded on a Perkin-Elmer 1600 Series FTIR infrared spectrometer. NMR spectra were obtained on a Varian 300 FT NMR spectrometer at the following frequencies (MHz): 31P, 121.4; 13C, 75.4; 'H, 299.9. Elemental analyses were done by SchwarzkopfLabs, Woodside, NY. The cumulene Mes*PCNPhz was prepared by the literature method. Cp'JV'b(Cl)[(~*-N,C)PhNCPMes*] (3). C p ' w l was prepared according to a literature methodm and used without recrystallization; we found that a n excess of this impure material must be used to get good yields. A brown solution of Cp'zNbCl(1.062 g, 2.63 mmol) and Mes*PCNPh (1.00 g, 2.63 mmol) in THF (10 mL) was stirred overnight at ambient temperature to give a red solution, whose 31PNMR spectrum showed -85% conversion of 1 to 3. Addition of more C p ' a C 1 (180 mg, 0.48 mmol) induced complete conversion to 3 overnight. The solvent was removed under vacuum, and the red (14)From the gyromagnetic ratios y ~ / =y 6.6144, ~ JPDis expected to be 46.4 Hz: Sergeyev, N. M. In Isotope Effects in NMR Spectroscopy; Diehl, P., Fluck, E., Gtinther, H., Kosfeld, R., Selig, J., Eds.;Springer Verlag: Berlin, 1990;p 42.
+ +
solid was extracted with petroleum ether. Concentration of the resulting red solution gave a red powder, which was collected on a fine frit. The mother liquor was layered with nitromethane and cooled to induce further crystallization. In total, 908 mg (45%) of pure 3 was collected. Crystals suitable for X-ray crystallography were obtained by slow recrystallization from petroleum ether at -20 "C over 4 months. lH N M R ( C a e ) (6): 7.51 (d, JPH = 0.9 Hz, 2H, Mea*); 7.04 (d, J = 6 Hz, 2H, 0-Ph); 6.97 (t,J = 6 Hz, 2H, m-Ph); 6.78 (t, J = 6 Hz, l H , p-Ph); 6.28 (d, J = 2.1 Hz, 2H, Cp'); 6.07 (d, J
Notes
Organometallics, Vol. 14, No. 7,1995 3605
Table 2. Atomic Coordinates ( x 104) and Equivalent Isotropic Displacement Coefficients (& X
4361.9(9) 9314(1) 3893(4) 5745(4) 10300(4) 9549(5) 3371(3) 7859(3) 5006(9) 9671(9) 5888(3) 10931(3) 4452(8) 4135 3309 3115 3821 3964(9) 3232 3492 4385 4676 4128(8) 4543 4647 4337 3923 3818 6195(9) 6832 6973 6479 5842 5700 4207(12) 3653(27) 3048(21) 5004(21) 6324(14) 5425(16) 6447(14) 4148(18) 4611(22) 3044(22) 3974(18) 5901(35) 5117(27) a
Y
2371.7(8) 2571.8(9) 2510(4) 3926(3) 1118(3) 227214) 1703(3) 3330(3) 1825(7) 3189(7) 2536(3) 2375(3) 1528(8) 1142 1431 1995 2055 3292(6) 3209 3426 3643 3560 1561(4) 1207 474 96 450 1183 1028(7) 527 352 677 1178 1353 1864(9) 1749(18) 3234(14) 2876(17) 4369(11) 4661(12) 3231(12) 2562(11) 2806(12) 2628(12) 2375(10) -197(45) 497(20)
UeqP
z
X
4675(30) 5 115(21) 2495(12) 3512(16) 4031(15) 3468(15) 8599(10) 8090 8607 9435 9431 8362(8) 8399 9268 9768 9208 8142(8) 8356 8457 8344 8131 8030 10215(8) 10800 11470 11555 10969 10300 8836(12) 9691(17) 10841(14) 11167(15) 10497(28) 8541(26) 9776(36) 7860(17) 8721(13) 7033(14) 7969(14) 9685(19) 8682(25) 8140(22) 8750(15) 7034(23) 7875(19) 8634(20) 7941(17)
59.3(5) -155(5) -1193(2) 619(2) -819(3) 1083(2) 944(2) -1028(2) 576(4) -638(4) -115(1) 16(2) -529(4) - 199 -138 -430 -672 535(3) 213 -178 -98 343 1808(4) 2165 2156 1789 1432 1442 457(3) 606 1036 1317 1168 738 665(5) -1588(8) -1287(8) -1239(9) 198(7) 985(7) 942(7) 2364(7) 1664(7) 1741(7) 1886(6) 2466(15) 2966(10)
Y
-624(20) 47(17) 142(12) -824(10) 50(10) -25(10) 1701(7) 1752 1496 1286 1413 2903(8) 3496 3770 3346 2810 4660(8) 5085 4783 4056 3631 3933 3909(7) 4414 4674 4431 3926 3666 3161(8) 529(14) 1831(11) 604(11) 1701(29) 1729(19) 2928(19) 5917(11) 4961(11) 4876(12) 5100(10) 5489(16) 4897(20) 5955(20) 5275(16) 2636(13) 2756(15) 2376(14) 2858(13)
2
x
10s) UeqP
2614(13) 2553(9) 925(7) 1204(6) 699(6) 1068(6) -673(4) -335 38 -69 -509 351(5) 81 151 465 589 -1433(3) -1762 -2152 -2213 -1884 -1494 -1192(4) -1308 -1006 -589 -473 -774 -736(5) -1250(10) -1083(7) -407(9) 1080(10) 1211(9) 1508(8) -1103(7) -674(5) -898(6) -1018(6) -2366(8) -2911(8) -2547(10) -2503(7) -1901(8) -2500(8) -1803(8) -2019(8)
Equivalent isotropic U defined as one-third of the trace of the orthogonalized Uv tensor.
Table 3. Selected Bond Lengths (A). Nb-N Nb-C(23) Nb-c1 Nb-Cp' centroid (Cnt)
2.075(12) 2.198(17) 2.503(5) 2.13 (av)
N-C(23) N-C(22) P-C(23) P-C(16)
1.301(23) 1.429(18) 1.688(19) 1.908(12)
"These data refer to one of the two independent but chemically equivalent molecules found in the unit cell. Complete lists of bond lengths and angles for both molecules are included in the supplementary material.
Table 4. Selected Bond Angles (deg). 83.1(4) Nb-C(23)-N 67.2(9) N-Nb-C1 147.8(10) N-Nb-C(23) 35.3(6) Nb-N-C(22) P-C(23)-N 156.2(13) 117.9(5) Cl-Nb-C(23) 108.5(7) C(16)-P-C(23) Cnt-Nb-Cnt 128 (av) 129.5(13) 77.5(9) C(22)-N-C(23) Nb-N-C(23) =Thesedata refer to one of the two independent but chemically equivalent molecules found in the unit cell. Complete lists of bond lengths and angles for both molecules are included in the supplementary material. = 2.1 Hz, 2H, Cp'); 5.92 (d, J = 2.1 Hz, 2H, Cp'); 5.60 (d, J = 2.1 Hz, 2H, Cp'); 1.80 (18H, 0-t-Bu); 1.41 (9H, p 4 - B ~ )0.20 ; (18H, SiMe3). I3C(IH} NMR (CDzC12) (8): 171.5 (d, ' J p c 155.3 Hz, P-C-N); 155.0 (d, 2 J= ~ 3.8 Hz, ~ o-Mes*); 148.9 ( p -
Mes*); 144.3 (ipso Ph); 140.3 (d, Jpc = 87.7 Hz, ipso Mes*); 127.7 (m-Ph); 126.1 (d, Jpc = 1.6 Hz, Cp'); 124.0 (O-Ph); 123.0 (p-Ph); 121.9 (m-Mes*); 117.8 (Cp'C-SiMe3); 112.5 (d, Jpc = 3.8 Hz,Cp'); 112.1 (Cp'); 108.8 (d, Jpc = 5.0 Hz, Cp'); 38.7 (d, Jpc = 1.6 Hz, o-CMes); 35.0 (p-CMe3); 33.4 (d, Jpc = 4.4 Hz, o-CMe3); 31.6 (p-CMe3);0.2 (d, Jpc = 1.1Hz, SiMe3). 31P{1H} NhfR (C6Ds): 6 14.3. IR (KBr): 2951,2361, 1652, 1592, 1558, 1540, 1505, 1456, 1387, 1358, 1248, 1170, 837 cm-'. Anal. c, 62.94; H, 7.73; N, 1.77; Calcd for C&&lNNbPSi2: Found: C, 62.89; H, 7.79; N, 1.83. X-ray Crystal Structure Determination of 3. Crystal, data collection, and refinement parameters are given in Table 1. Suitable crystals were selected and mounted e t h epoxy cement to glass fibers. The unit-cell parameters were obtained by the least-squares refinement of the angular settings of 24 reflections (20"I2 0 I25"). The systematic absences in the diffraction data for 3 are uniquely consistent for space group P21Ic. The structure was solved using direct methods, completed by subsequent difference Fourier syntheses and refined by full-matrix least-squares procedures. Two independent bu.t chemically equiv compound molecules were loeated in the asymmetric unit. The centroid to niobium distances are 2.125(14), 2.131(15), 2.137(14), and 2.125( 14) A. The centroid-niobium-centroid angles are 127.8(5)and 128.9(5)". All non-hydrogen atoms were refined
Notes
3606 Organometallics, Vol. 14, No. 7, 1995 with anisotropic displacement coefficients. Hydrogen atoms were ignored. Phenyl rings were refined as rigid planar hexagons and Cp rings as rigid pentagons to conserve data. Additional results of the structure determination are available as supporting information. All software and sources of the scattering factors are contained in either the SHELXTL (5.1)or the SHELXTL PLUS (4.2)program libraries (G.Sheldrick, Siemens XRD, Madison, WI). PhotochemicalConversion of 3 to Cp’&bCl(CNPh)(4) and 2,4-(t-Bu)~-6-CgIzCMegH (2). A red benzeneds (1 mL) solution of 3 (10 mg, 13 pmol) with a tetramethylsilane internal standard was irradiated with a water-cooled 450 W Ace-Hanovia Mercury photochemical lamp for 5 h. The solution darkened to a deep brown. The ‘H NMR spectrum, after irradiation, showed formation of 2 and 4 in 79% yield. The isocyanide complex 4 was characterized by ‘H NMR and IR of the reaction mixture, while phosphaindan 2 was identified by lH and NMR in comparison to an authentic sample. In a separate experiment, a similar sample of 3 was irradiated for 1 h, after which the solution contained an -2:3 mixture of 3 and 1 by 31PNMR. Additional irradiation (2h) completed the conversion to 2 and 4. In a third experiment, a sample of 1 (10 mg, 26 pmol) in benzene-& (1 mL) was irradiated for 3 h and showed only 2 in the 31PNMR spectrum. [Cp’zNb(Cl)[(t12-N,C)P~~CP~es*]]B (5). F ~ Tetrafluoroboric acid dimethyl ether complex (14.9pL, 0.128mmol) was added to a solution of 3 (100mg, 0.128mmol) in petroleum ether (5 mL). The clear red solution became yellow after 1 h of stirring, with precipitation of the product. The white powder was collected on a fine frit and washed with petroleum ether (99 mg, 89%). An analytical sample, obtained from a 1:l mixture of methylene chloride and petroleum ether (5 mL), cocrystallized with CHZC12, as confirmed quantitatively by ‘H NMR. ‘HNMR (CD2C12) (6): 7.44(d, 3 J p ~= 2.4 Hz, 2H, Mes*); 7.32(d, ‘JPH = 302 Hz, 1 H, P-H); 7.19 (t, J = 8.0 Hz, 1 H, p-Ph); 7.04(t, J = 8.0 Hz, 2H, m-Ph); 6.83(2H, Cp’); 6.54(d, J = 7.6Hz, 2H, 0-Ph); 6.36(4H, Cp’); 6.03(2H, Cp’); 1.47(18H, o-t-Bu); 1.36(9H,p-t-Bu); 0.17 (18H, SiMe3). 13C{’H) NMR
(CD2C12)(6):208.5 (d, ‘Jpc = 115.6Hz, P-C-N); 157.2(d, 3Jpc = 11.0 Hz, ipso Ph); 154.6 (quat-Mes*); 137.4 (quat-Mes*); 130.8 (Cp’C-SiMea); 128.95-128.9 (overlapping p-Ph and m-Ph); 126.2(Cp‘); 124.2(m-Mes*);123.9 (0-Ph);121.4(d, ~JPC = 35.0 Hz, ipso Mes*); 112.3 (Cp’); 110.2 (Cp’); 109.9 (Cp‘); 38.3(0-CMe3); 35.7 (p-C Med; 33.8 (d, JPC = 6.0Hz, 0-CMej); 31.4@-CMed; 0.3 (SiMes). NMR (CD2CL): 6 -37.4 ppm (d, JPH= 302 Hz). IR (KBr): 3113,2957,2902, 1641,1590,
1484,1408,1364,1248,1167, 1051,904,837,755,687,636, 522 cm-’. Anal. Calcd for C ~ ~ H ~ I B C ~ F & N ~ P S ~ ~ . O . ~ ~ C H Z C C, 52.98;H, 6.67;N, 1.47. Found: C, 52.63;H, 6.87,N, 1.53. Reaction of 5 with DzO. An excess of D2O (-0.1 mL, 99.9% D) was added t o a solution of 5 (10mg, 11.5pmol) in either nitromethane-da or m e t h y l e n e 4 chloride in an NMR tube. After the tube was vigorously shaken for several minutes, the and ’H NMR spectra were recorded. The P-H signal disappeared in the lH spectrum, and the 31P spectrum showed a 1:l:l triplet (6 -38.4,JPD = 44.3 Hz). Reaction of 5 with KO-t-Bu. A clear solution of 5 (14mg, 16 pmol) in THF (1mL) was added to solid KO-t-Bu (2mg, 16 pmol). The solution became red, and NMR showed that 3 was the only P-containing product.
Acknowledgment. We thank Dartmouth College and the Petroleum Research Fund, administered by the ACS, for partial support of this work. J.B.A. thanks Dartmouth College for a Presidential Scholarship and the NSF for a REU fellowship. Supporting Information Available: Additional structural results for 3, including complete tables of bond lengths and angles and anisotropic displacement coefficients (7pages). This material is contained in many libraries on microfiche, immediately follows this article in the microfilm version of the journal, can be ordered from the ACS, and can be downloaded from the Internet; see any current masthead page for ordering information and Internet access instructions.
OM950116H
