Organometallics 1995, 14, 2585-2588
2585
Notes Preparation and Structures of Arylmolybdenum(6+) Nitrido Compounds: (2,4,6-Me&H2)8Mo=N and (~-M~~NCH~C tBuO)Mo=N GH~)~( Kenneth G . Caulton," Malcolm H. Chisholm," Simon Doherty, and Kirsten Folting Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, Indiana 47405 Received September 20, 1994@ Summary: (tBuO)3Mo~N, 1, and the mesityl Grignard, MesMgBr, react in diethyl ether to give green solutions from which amber crystals of (Mes)sMo=N, 2, were obtained by crystallization from pentane lether. I n a related reaction 1 and LiC&CHflMez (2 equiv) were found to yield (tBuO)(C&CHflMed~Mo=N, 3, which was also isolated as dark amber crystals from ether1 pentane. Compounds 2 and 3 have been crystallographically characterized. I n 2 there is a central pyramidal C ~ M O E N moiety with Mo-N = 1.649(4) A, Mo-C = 2.125(5) A (av), and N-M-C = 100". I n 3 the coordination at molybdenum is that of a distorted octahedron with M o z N = 1.620(22) A. The chelate CGH4CHflMez ligand forms five-membered rings and the N-Mo distance trans to the MOEN bond is longer, cfi 2.742(2) A us 2.434(2) A. These are the first crystallographically characterized metal nitrides supported by hydrocarbyl ligands for a group 6 element and contrast with the recently reported ( t B u C H d 3 M o ~ Nthat was proposed to be polymeric [Herrmann; et al. J. Am. Chem. SOC.1994, 116, 49891.
Introduction The recent communication by Herrmann and coworkers1 on the preparation and reactivity of PBuCH2)3Mo=N prompts us to report on our synthesis of related hydrocarbyl-supported molybdenum(V1) nitrides together with their structural characterization and some initial comments on the reactivity of the Mo-C bonds.2
Results and Discussion Treatment of a ether solution of Mo(N)(OtBu)3, 1,at -78 "C with 3 equiv MesMgBr (Mes = mesityl) followed by gradual warming to room temperature gave a deep green solution from which (Mes)sMo=N, 2, could be isolated aRer filtration and extraction into pentane. The absence of structural data for o-carbon-supported metal nitrido complexes of group 6 prompted us to undertake a single-crystal X-ray analysis. X-ray quality crystals @
Abstract published in Advance ACS Abstracts, March 15, 1995.
(1)Herrmann, W. A.; Bogdanovic,S.; Poli, R.; Priermeier, T. J.Am.
Chem. SOC.1994,116,4989. (2)For osmium nitride complexes see: (a) Marshman, R. W.; Shapley, P. A. J.Am. Chem. SOC.1990,112,8369.(b) Shapley, P. A.; Kim, H. S.; Wilson, S. R. Organometallics 1988,7,928.(c) Marshman, R. W.; Shusta, J. M.; Wilson, S. R.; Shapley, P. A. Organometallics 1991,10,1671.
C19)
cfa
K28,
Figure 1. ORTEP diagram of (Mes)3Mo=N, 2, illustrating the trigonal pyramidal environment of molybdenum. Selected bond distances (A) and angles (deg): Mo(l)-N(2) = 1.649(4),Mo(l)-C(3) = 2.142(4), Mo(l)-C(12) = 2.100(5), Mo(l)-C(21) = 2.133(5); N(2)-Mo(l)-C(3) = 97.52(17), N(2)-Mo(l)--C(12) = 102.31, N(2)-Mo(l)--C(21) = 99.93(18), C(3)-Mo(l)-C(12) = 118.88(17),C(3)-Mo(l)-C(21) = 122.24(17), C(12)-Mo(l)-C(21) = 110.26(17). of 2 were obtained as deep amber prisms by cooling a pentane-layered ether solution at -20 "C overnight. The lH NMR data of 2, reveal three resonances assignable to the aromatic mesityl (6= 6.63 ppm, 6H) and methyl (6 = 2.66 ppm, 18H; 6 = 2.02 ppm, 9H) protons. We observed no significant line broadening in the low-temperature 'H N M R spectrum of 2, confirming that rotation about the Mo-C(sp2) bonds is still rapid at these temperatures. We assign the Mo=N stretch to an absorption band at 1041 cm-' in the IR spectrum (Kl3r)which is some 40 cm-l higher than that reported for (tBuCH2)3Mo=N, consistent with the absence of Mo=N to Mo dative bonding in 2. Unlike (tBuCH2)3Mo=N, which is presumed to be polymeric in the solid state, compound 2 is monomeric and shows interesting stacking, as shown in Figures 1 and 2, respectively. In contrast to (R0)3Mo=N compounds which are linear polymers with alternating short
0276-733319512314-2585$09.00/0 0 1995 American Chemical Society
Notes
2586 Organometallics, Vol. 14,No. 5, 1995
b
C
Figure 2. Stereoscopic view of the unit cell of (Mes)sMo=N, 2. Two cells along a show the intermolecular stacking between the mesityl rings. and long Mo-N distance^,^ the shortest intermolecular Mo-N distance in 2 is 6.63 A. The local trigonal C3Mo=N geometry is as might have been expected with C-Mo-N angles close to 100". The close intermolecular interactions of the "stacked" aromatic rings average 3.76
A.
Their nonparallel arrangement is reflected in an angle of 26" between the least squares planes defining their rings. Treatment of a benzene solution of Mo(N)(OtBu)3(1) with 2 mol equiv of Li[CcH&H2NMe21 resulted in smooth metathesis and replacement of two tert-butoxide ligands to afford (tBuO)(CsH4NMe&Mo=N (3). The 'H NMR spectrum of 3 consists of a single resonance corresponding to the tBuO ligand, an appropriate number of signals consistent with the presence of diasterotopic methylene protons, and broad resonances for the dimethylamino substituents. A single-crystal X-ray study of 3 was undertaken, revealing a pseudooctahedral geometry at molybdenum, as shown in Figure 3. A dimethylamino substituent occupies the site trans to the nitrido ligand [N(2)-Mo( 1)-N(25) = 166.86(9)"1. The elongated metal nitrogen-amine bond [Mo(l)-N(25) = 2.742(2) AI reflects the strong trans influence of the nitrido ligand4 compared with the alkoxide [Mo(l)-N(15) = 2.434(2) AI. Similar trans bond lengthening effects have been observed for high-valent imido- and oxo-containing group 6 complexes. The Mo-C(ipso) distances [Mo(l)-C(8) = 2.188(3) 8,Mo(l)-C(18) = 2.176(2)AI are within the range expected for high-valent
(3) (a) Chisholm, M. H.; Huffman, J. C.; Hoffman, D. M. Inorg. Chem. 1983,22,2903. (b) Chan, D.M.-T.;Chisholm, M. H.; Folting, K.; Huffman, J. C.; Marchant, N. S. Inorg. Chem. 1986,25,4170. (4)Nugent, W. A.; Mayer, J. M. Metal Ligand Multiple Bonds: The Chemistry of Transition Metal Complexes Containing Oxo, Nitrido, Imido, Alkylidene, or Alkylidyne Ligands; Wiley: New York, 1988;p 156. (b) Shustorovich, E. M.; Pora-Koshits. M. A,: Buslaev, Yu. A. Coord. Chem. Rev. 1976,17, 1.
Figure 3. ORTEP diagram of (tBuO)(CsH4CH~NMe& MosN, 3, illustrating the trans arrangement of the nitrido and elongated dimeth lamino chelate substituent. Selected bond distances ( ) and angles (deg): Mo(l)-o(3) =
x
1.886(2),Mo(l)-N(Z) = 1.663(2),Mo(l)-N(15) = 2.434(2), Mo(l)-N(25) = 2.742(2),MO(l)-C(8) = 2.188(3),Mo(l)-C(18) = 2.176(2);0(3)-Mo(l)-N(2) = 104.00(9), O(~)-MO(1)-N(15) = 167.04(8), 0(3)-Mo(l)"bdN(25) = 77.64(7), 0(3)-Mo(l)-C(8) = 95.94(9), 0(3)-Mo(l)-C(18) = 109.63(9), N(2)-Mo(l)-N(15) = 82.55(9), N(2)-Mo(l)--N(25) = 166.86(9),N(Z)-Mo(l)-C(8) = 102.93(10),N(2)-Mo(l)-C(18) = 97.32(10),N(15>-Mo(l)-N(25) = 98.58(7),N(15)-Mo(1)-C(8) = 71.51(9), N(15)-Mo(l)-C(18) = 80.13(8), N(25)-Mo(l)-C(8) = 89.77(8), N(25)-Mo(l)-C(18) = 142.30(10). Mo-C(sp2) bonds of chelate-supported MoEN length [Mo(l)-N(2) = (5) (a) Sullivan, A. C.; Wilkinson, G.; Matevallil, M.; Hursthouse, M. B. J.Chem. Soc., Dalton Trans. 1988,53. (b) Lai, R.; Mabille, S.; Croux, A,; LeBot, S. Polyhedron 1991,10, 463.
Organometallics, Vol. 14,No. 5, 1995 2587
Notes Table 1. Fractional Coordinates and Isotropic Thermal Parameters for Compound 2 atom
1 0 4 ~
7530.6(4) 5483(5) 7592(5) 7011(5) 6970(6) 7439(5) 7976(6) 8090(5) 6329(7) 7245(8) 8646(7) 8261(6) 7254(6) 8010(7) 9722(6) 10695(6) 10019(5) 5392(7) 10495(8) 11167(6) 8121(6) 7309(5) 7719(6) 8884(5) 9695(6) 9341(5) 5983(7) 9260(7) 10307(6)
104y 4553.3(2) 4625(2) 3583(3) 3762(3) 3124(3) 2298(3) 2131(3) 2751(3) 4621(3) 1600(4) 2484(3) 4254(3) 3986(3) 3806(3) 3871(3) 4121(3) 4319(3) 3868(5) 3661(4) 4598(4) 5839(3) 6513(3) 7339(3) 7539(3) 6867(3) 6028(3) 6362(4) 8443(3) 5362(3)
1042 2414.1(2) 2148(2) 3235(2) 3892(2) 4409(3) 4286(2) 3635(3) 3110(2) 4026(3) 4823(3) 2408(3) 1412(3) 729(3) 135(3) 181(3) 853(3) 1467(2) 623(3) -474(3) 2179(3) 2709(2) 2269(2) 2487(3) 3122(3) 3542(3) 3349(2) 1576(3) 3354(3) 3850(3)
10Biso 15 21
104~
104r
104%
7051.5(3) 7934(3) 8200(2) 9469(3) 10218(4) 8792(4 10630(4) 5051(3) 4757(3) 3468(3) 2458(3) 2722(3) 4014(3) 4405(3) 5088(3) 3817(3) 5748(4) 7675(3) 8858(3) 9416(3) 8796(3) 7636(3) 7067(3) 5826(3) 6023(3) 7297(4) 4595(3)
2758.2(1) 3502(1) 1718(1) 1432(2) 668(2) 1108(2) 2190(2) 2307(2) 1414(2) 1170(2) 1809(2) 2695(2) 2937(2) 3883(2) 3891(1) 3722(2) 4798(2) 3385(2) 4052(2) 4402(2) 4086(2) 3430(2) 3076(2) 2356(2) 1708(1) 1123(2) 1161(2)
2691.7(3) 1863(3) 2604(2) 1943(3) 2937(4) 155(4) 2081(4) 688(3) 75(3) -1229(4) -1944(4) -1355(3) -63(3) 613(3) 2418(3) 3182(4) 2996(4) 5162(3) 5630(3) 7235(3) 8431(3) 8017(3) 6403(3) 6023(3) 4714(3) 5425(4) 4069(4)
18 19 21 20 17 24 28 22 19 22 27 24 23 19 36 35 24 18 19 21 19 22 17 25 25 21
1OBim 9 12 12 15 18
20 21 12 14 18 20 18 14 15 13 16 17 11
14 16 16 15 12 13
12 16 18
that observed in 2 [1.648(4) AI and other nitridocontaining c ~ m p l e x e s , ~reflecting t~ the retention of Mo-N triple bond character upon increasing the coordination from 4 to 6 in 2 and 3, respectively. Our preliminary studies of the reactivity of 2 reveal significant differences from that recently reported for (6) (a) Kim, J. C.; Rees, W. S.; Geodken, V. L. Inorg. Chem. 1994, 33,3191. (b)Herrmann, W. A.; Bogdanovic, S.; Behm, J.;Denk, M. J. Orgunomet. Chem. 1992,430, C33. (c) Schmitte, V. J.; Friebel, C.; Weller, F.; Dehnicke, K. Z. Anorg. AZZg. Chem. 1982,495, 149. (d) Dehnicke, K.; Kruger, N.; Kujanek, R.; Weller, F. 2.KristulZogr. 1980, 153, 181.
compd 2 empirical formula color of cryst
18
Table 2. Fractional Coordinates and Isotropic Thermal Parameters for Compound 3 atom
Table 3. Selected Crystal Data for Compounds 2 and 3
cryst dimens space group cell dimens temp ("C) a (A) b (A) c
-173 8.184(2) 15.814(3) 18.318(4)
(A)
compd 3
C Z ~ H ~ ~ M OCmH33N3MpC N dark amber pale yellow/ colorless 0.10 x 0.25 x 0.08 x 0.16 x 0.30 0.35 Pi P21/a
a (deg) /3 (deg) 102.00(1) y (deg) 2 (molecules/cell) 4 2319.06 vol (A31 calc dens (g/cm3) 1.339 wavelength (A) 0.710 69 467.50 mol wt linear abs coeff 5.631 detector to sample dist (cm) 22.5 23.5 sample to source dist (cm) av w scan width at half-height (degN.25 scan speed (deglmin) 8.0 2.0 scan width (deg dispersion) 4 individual background ( s ) 3.0 x 4.0 aperture size (cm) 28 range (deg) 6-45 5625 total no. of reflns collcd no. of unique intensities 3048 2884 no. with F > 0.0 2652 no. with F > 3*a(F) R(F) 0.0332 RdF) 0.0349 1.092 goodness of fit for the last cycle 0.02 max d/a for last cycle
+
-168 8.929(2) 15.054(3) 8.533(1) 94.11(1) 105.21(1) 90.43(1) 4 1103.44 1.359 0.710 69 451.46 5.944 22.5 23.5 0.25 8.0 2.0 4 3.0 x 4.0 6-55 7836 5092 4887 4627 0.0341 0.0348 1.010 0.03
the neopentyl complex (CHztBu)3Mo=N, the chemistry of which is dominated by addition across the MosN bond to yield imido (NH) complexes of increased coordination number and by a-C-H activation. These will be described in detail a t a later time.
Experimental Section (Mes)&lorN, 2. To a diethyl solution of Mo(N)(OtBu)3 (2.75 g, 8.36 mmol) at -78 "C was added a solution of MesMgBr (25.0 mL, 25 mmol) dropwise over a period of 1h. The reaction mixture was left to stir for 3 h, during which time a precipitate formed and a deep green coloration appeared. After warming to room temperature, filtration afforded a clear green solution. The solvent was removed in uucuo and the residue extracted with 6 x 50 mL of pentane to afford spectroscopically pure 2 in 45% (1.70 g) yield as a yellow brown solid. Crystallization from ethedpentane afforded deep amber prisms suitable for X-ray analysis. Selected data for 2 follow. Anal. Calcd for C27H33N0: C, 69.35; H, 7.11; N, 3.00. Found: C, 67.94; H, 6.91; N, 3.02. 'H NMR (300 MHz, C6D6, 6): 6.62 (br, s, 6H), 2.66 (s, 18H, o-Me), 2.02 (s, 9H, p-Me). l3C(lH} NMR (75 MHz, C & 3 , 6 ) : 192.94 (@SO), 141.51 (pura), 128.60 (ortho), 127.0 (metu),25.02 (CH3),21.35 (CH3). IR (KBr, cm-1): 3011 (m), 2950 (m), 2914 (m), 1591 ( s ) , 1448 (br, s ) , 1398 (m), 1280 (s), 1041 (s), 846 (s), 702 (w), 584 (m). (2-MezNCH&&)&BuO)Mo~N, 3. To a n ether solution of Mo(N)(O~BU)~ (0.250 g, 0.76 mmol) was added a suspension of Li[CsH&HzNMez] (0.214 g, 1.52 mmol) with rapid stirring. The reaction mixture was stirred overnight and the solvent removed to leave a gummy yellow oil. Extraction with pentane afforded a clear yellow solution and a white precipitate was filtered out. Crystallization from pentane/ether afforded 3 as pale yellow crystals in 67% yield (0.21 g). Selected data for 3 follow. Anal. Calcd for C ~ ~ H ~ ~ N ~C, M58.33; O O : H, 7.37; N,
Notes
2588 Organometallics, Vol. 14, No. 5, 1995 9.31. Found: C, 58.46; H, 7.36; N, 9.47. 'H NMR (300 MHz, C6H6, 6): 9.32 (d, 1H, ' J H H= 7.42 Hz, c&4), 7.98 (dd, 1H, ' J H H= 5.8 Hz, 2.7 Hz, C&4), 7.31 (t, l H , 'JHH = 6.6 Hz, C&4), 7.15-7.25 (m, 4H, C&), 6.98 (d, l H , 'JHH = 8.4 Hz), 4.75 (d, = 14.7 Hz, CHz), l H , ' J H H= 12.3 Hz, CH'), 3.46 (d, l H , 'JHH 2.96 (d, l H , ' J H H= 12.3 Hz,CHz), 2.85 (d, l H , 'JHH = 14.7 Hz, CHz), 2.6 (br, 6H, NMeZ), 1.99 (s, 6H, NMeZ), 1.55 (s, 9H, C(CHd3). Crystallographic Studies. General operating procedures and a listing of programs have been previously given.' Atomic coordinates for compounds 2 and 3 are given in Tables 1 and 2, respectively, and a summary of the crystal data and procedures is given in Table 3. (Mes)&Io=N,2. Dark amber prisms of 2 were grown by slow cooling of a ethedpentane solution at -20 "C overnight. Crystals of Mo(N)(Mes)sare monoclinic, space group P2du with unit cell constants a = 8.184(2)A, b = 15.814(3)A, c = 18.318(4) A, p = 102.00(1)",T = 173 " c , v = 2319.06 As, dcalcd = 1.339 g/cm3, and 2 = 4. Data were collected by using the standard moving crystal-moving detector technique in the 28 range 6.0-45.0". A total of 3048 unique reflections were collected of which 2652 were observed ( F > 3 d F ) ) . The structure was solved using a combination of direct methods and difference Fourier methods and refined by full matrix least-squares techniques. Refinement converged a t R(F) 0.033 and R d F ) = 0.035. (7) Chisholm, M. H.; Folting, K.; Huffman, J. C.; Kirkpatrick, C. C. Inorg. Chen. 1984,23,1021.
(2-Me2NCH2C&)2(tBuO)MoEN, 3. Pale yellow crystals of 3 were grown by the slow cooling of an ethedpentane solution at -20 "C overnight. Crystals of (tBuO)C6H&H~NMe&Mo=N are triclinic, space group Pi with unit cell constants a = 8.929(2)A, b = 15.054(3)A, c = 8.533(1) A, a = 94.11(1)", /3 = 105.21(1)", y = 90.43(1)", T = -168 "C, V = 1103.44 A3, d & d = 1.359 g cm3,and 2 = 2. Data were collected by using the standard moving crystal-moving detector technique in the 28 range 6.0-55.0'. A total of 5092 unique reflections were collected of which 4627 were observed ( F > 3dF)). The structure was solved by using a combination of direct methods (MULTAN-78) and difference Fourier techniques. The full matrix least-squares refinement was completed with anisotropic thermal parameters on all nonhydrogen atoms. Refinement converged a t R(F) = 0.0341 and RJF) = 0.0348. The final difference map was essentially featureless, the largest peak was 0.61 e k3in the vicinity of the molybdenum atom. The deepest hole was -0.87 e As.
Acknowledgment. We thank the National Science Foundation for financial support. Supplementary Material Available: For compounds 2 and 3,listing of atomic coordinates, thermal parameters, bond distances, and bond angles (11pages). OM940732Y
