- Email: [email protected]
Fischer-type alkylidyne tungsten complexes containing strong π donor ligands
ELSEVIER
InorganicaChimicaActa252 (1996) 131-139
Fischer-type alkylidyne tungsten complexes containing strong 7r donor ligands Andreas Mayr a,b,:~,l,Tsung-Yi Lee
a
a Department of Chemisuy. State University of New York at Stony Brook. Stony Brook, NY ! 1794-3400. USA h Department cfChemistry, The University ofHong Kong, Poyulam Road. Hong Kong, Hong Kong
Received 19 March 1996;revised3 June 1996
Abstract Reaction of [W(CPh)CI(CO)(PMe3)3] (1), with NaNC4H4, NaNCsH6, NaOC6Hs and NaSR (R=CMe3, C6HH) in THF affords the alkylidyne tungsten complexes [W(CPh)X(CO)(PMe3)3] (2a-e), containing pyrrolide, indolide, phenoxide and alkylsulfide ligands, X, respectively. The ¢r donor ligands X occupy the coordination site trans to the alkylidyne ligand. The anionic complexes [NEh][W(CPh)X2(CO)(PMe3)2] ((3a) X=NC,,H,,), ((3b) X=NCsH6), form upon reaction of I with 2 equiv, of NaNC41-h and NaNCsH6 in THF, followed by metathesis with NEt4CIin CH2C12.Reaction of I with the sodium salt of pyrrole-2-carboxaldehyde methylimine affords [W(CPh)(NC4H3-CHNMe-2 ) (CO)(PMe3)2] (4). The solid state structures of complexes 2a and 2e were determined by X-ray crystallography. Complex 2d reacts in THF solution with carbon monoxide to afford cis- [W(CPh) (SCMe3) (CO)2(PMe3)2] (6). In contxast, the analogous bromo complex [W(CPh)Br(CO)(PMe3)3] (7) gives under the same conditions an equilibrium mixture of 7 and trans[W(CPh)Br(CO)2(PMe3)2]. Keywords: Crystalstructures;Tungstencomplexes;Alkylidynecoml:-iexes;lr Donorligandcomplexes
!. Introduction Strong ~r donor ligands are strikingly absent in Fischertype [ 1 ], or low-valent, alkylidyne metal complexes, but are commonly found in Schrock-type [2], or high-valent, systems [3]. This situation is a consequence of the electronic structure of these compounds [ 4]. The Schrock-type systems possess empty low-lying d orbitals while the Fischer-type systems do not. Since Fischer-type alkylidyne metal complexes are, in most cases, electronically saturated species, 7r donor ligands will not enhance their stability. Rather, it can be expected that the presence of ~'donor ligands will bolster their reactivity. In particular, the presence of strong Ir donor ligands should enhance the reactivity towards electrophiles. This feature could be quite useful, since, except for the addition of protons, only few reactions of Iow-valent alkylidyne complexes with electrophiles have been described [ 3]. The presence of ~"donor ligands might also facilitate intramolecular alkylidyne-ligand coupling reactions [5]. Among the strategies to develop the synthetic potential of low-valent alkylidyne metal complexes [6], two different approaches * Con'espor~dingauthor. 1On leaveat the Universityof HongKong. 0020-16931961515.00© 1996ElsevierScienceS.A. All rightsreserved P!!S0020-1693(96)05306-6
have been particularly successful: reactions of cationic Group 7 metal aikylidyne complexes with nucleophilic substrates [ 7 ] and photochemical transformations [ 8 ] of functionalized Group 6 metal alkylidyne complexes. Clearly, the development of new methods to activate alkylidyne ligands towards reactions with Lewis-acids would be of considerable synthetic value. The introduction of strong ~rdonor ligands could serve this purpose. In the pursuit of this goal, several alkylidyne tungsten complexes of the Fischer-type containing nitrogen, oxygen and sulfur ¢r donor ligands have been prepared.
2. Experimental Standard inert-atmosphere techniques were used in the execution of the experiments. The solvents methylene chloride (Call2), diethyl ether, tetrahydrofuran (Na/benzophenone) and hexane (CaH2) were dried and distilled prior to use. Complexes 1 [9] and 7 [10] and cis[ W(CPh) Cl(CO) 2( PMe3 ) 2] [ 11 ] were prepared as previt, usly reported. Pyrrole-2-carboxaldehyde methylimine was prepared as reported in the literature [ 12]. All other reagents were obtained from commercial sources. The NMR spectra were measured at 250 or 300 MHz (for tH NMR) at room
132
A. Mayr. T.-Y. Lee / Inorganica ChimicaActv 252 (1996) 131-139
temperature, unless otlaerwise noted; solvent peaks were used as internal reference; the chemical shifts are reported in 8 relative to TMS. Elemental analyses were performed by Schwarzkopf Micronalytica! Laboratory. 2.1. Syntheses 2.1.1. W(CPh)(NC4H4)(CO)(PMea)3 (2a)
An oil dispersion containing 80% sodium hydride (0.080 g, 3.32 mmol) is washed with hexane ( 3 × 15 mi). The sodium hydride is suspended in 25 ml THF and 77.0 /zl distilled colorless pyrrole (0.075 mg, 1.11 mmol) is added. The solution is refluxed for 50 rain and filtered after cooling to r.t. A pale yellow NaNCaH4 in THF solution is obtained. Complex 1 (0.437 g, 0.77 mmol) is added to a 50 ml flask containing 20 ml THF, and the solution of NaNC4I-I4 in THF is added. After stirring for 36 h, the solvent is removed under vacuum. The product is extracted with diethyl ether and recrystallized from the same solvent to give orange crystals (0.139 g, 30%). IR (THF): 1888 (s, CO) cm - j . IH NMR (THF-ds): 8 7.11-7.03 (m, 5H, Ph), 6.4! (s, 2H, NCH), 5.81 (s, 2H, NCCH), 1.75 (d, J(PH) =6.5 Hz, 9H, PMe3 trans to CO ), 1.40 ( virtual t, 2.5 Hz, 18H, 2PMe3 cis to CO ). 13C NMR (THF-ds): ~$269.7 (q, J(PC) = i0.8 Hz, CPh), 227.0 (dt, 2j(PCtrans)=39.5, 2J(pccis)=7.2 Hz, CO), 153.8 (i-Ph), 131.9, 131.8, 128.5, 128.3, 125.2, 107.6 (2C) (Ph, NC4H4), 23.3 (d, J(PC ) = 21.9 Hz, PMea trans to CO ), 20.8 (t, J ( P C ) = 12.6 Hz, 2PMe3 cis to CO). alp NMR (THF-ds): c$ - 214.6 (d, J(WP) = 268.4, J(PP) = 18.2 Hz, 2PMe3 cis to CO), - 225.1 (t, J(WP) = 213.6, J(PP) = 18.2 Hz, PMea trans to CO). 2.1.2. W( CPh )( NCsH6)( CO )( PMe j)3 (2b )
An oil dispersion containing 80% sodium hydride (0.048 g, 1.99 mmol) is washed with hexane ( 3 × 10 ml). The sodium hydride is suspended in 20 ml THF and 0.075 g indole (0.64 mmol) is added. The solution is refluxed for 20 min and filtered after cooling to r.t. A colorless solution of NaNCsH6 in THF is obtained. Complex 1 (0.293 g, 0.52 mmol) is added to a 50 ml flask containing 15 ml THF, and the solution ol NaNCsH6 is added. The mixture is stirred for 36 h. The solvent is removed under vacuum, the product is extracted with diethyl ether and recrystalhzed from the same solvent to give orange needle crystals (0.135 g, 40%). IR (THF): 1882 (s, CO) cm -I. IH NMR (THF-ds): 87.696.20 (m, IIH, Ph, NCsHt), 1.77 (d, J ( P H ) = 6 . 3 Hz, 9H, PMea trans to CO), 1.38 (virtual t, 3.0 Hz, 18H, 2PMea cis to CO). maCNMR (THF-da): 8 270.0 (q, J(PC) = 10.7 Hz, CPh), 226.0 (m, CO), 148.6 (i-Ph), 14C.8, 140.6, 128.8, 128.5, 125.6, 121.7, 119.6, 118.4, 117.8, 116.5, 101.1 (Ph, NCsH6), 23.0 (d, J(PC ) = 21.5 Hz, PMea trans to CO ), 20.8 (virtual t, 12.6 Hz, 2PMea cis to CO). alp NMR (THF-d8): 8 -214.6 (d, J(WP) =268.4, J(PP) = 18.2 Hz, 2PMea cis to CO), - 225. ! (t, J(WP) = 213.6, J(PP) = 18.2 Hz, PMe3 trans to CO ~. anal. Calc. for C2sHasNOPaW (MW 645.35 ): C, 46.53; H, 5.93. Found: C, 46.62; H, 6.19%.
2.1.3. W(CPh):OCtHs)(CO)(PMesb (2c)
Phenol (0.074 g, 0.79 mmol) is added to a flask containing 15 ml hexane, and an excess of sodium (0.086 g, 3.74 mmoi) is added. The solution is stirred at r.t. for 4 h and the solvent is removed under vacuum. Excess sodium is removed mechanically. The solid NaOCtHs is transferred to a 50 ml flask and 25 ml THF is added. Then a solution of 1 (0.106 g, 0.19 mmol) in 15 ml THF is added. After stirring for 19 h, the solvent is removed under vacuum. The product is extracted with diethyl ether and recrystallized from the same solvent to give red-orange crystals (0.050 g, 43%). IR (THF): 1883 (s, CO) cm -I. IH NMR (CDCI3): ~ 7.106.36 (m, 10H, CPh, OPh), 1.61 (d, J ( P H ) = 6 . 5 Hz, 9H, PMe3 trans to CO), 1.54 (virtual t, 2.9 Hz, 18H, 2PMe3 cis to CO). 13C NMR (CDCIa): 8 263.3 (m, CPh), 227.2 (dt, 2J(PCtrans)=47.8, 2j(PCcis)=5.3 Hz, CO), 168.9 (iOPh), 152.7 (i-Ph), 128.8, 127.5, 127.1,123.7, 119.3, 112.7 (CPh, OPh), 20.8 (virtual t, 12.6 Hz, 2PMe3 cis to CO), 19.6 (d, J(PC) =20.3 Hz, PMe3 trans to CO). alp NMR (CDCla): 8 - 1 8 . 3 (d, J(WP)=273.6, J ( P P ) = 2 1 . 3 Hz, 2PMe3 cis to CO), - 22.8 (t, J(WP) = 225.3, J(PP) = 21.3 Hz, PMea trans to CO). Anal. Caic. for C2aHaTO2PaW (MW 622.32): C, 44.39; H, 5.99. Found: C, 44.23; H, 6.00%. 2.1.4. W(CPh)(SCMe~)(CO)(PMea)3(2d)
2-Methyl-2-propanethiol ( 1.60 g, 17.74 mmoi) is added to a Schlenk flask containing 30 ml hexane, and an excess of sodium (1.523 g, 66.25 mmol) is added. The mixture is stirred at r.t. for 8 h. The solvent is removed under vacuum. Excess sodium is removed mechanically from the white salt. The solid NaSCMe3 is transferred into a 100 ml flask containing 60 ml THF. Then a solution of 1 (1.!7 ° g, 2.086 mmol) in 20 ml THF is added. After stirring for 24 h, the solvent is removed under vacuum. The product is extracted with hexane and recrystallized from the same solvent to give red-orange crystals (1.103 g, 86%). IR (THF): 1883 (s, CO) cm - t . IH NMR (CDCI3): 8 7.27 (s, 5H, Ph), 1.64 (virtual t, 3.0 Hz, 18H, 2PMe3 cis to CO), 1.60 (d, J(PH ) = 7.0 Hz, 9H, PMe3 trans to CO ), 1.41 (s, 9H, CMea ). taC NMR (CDCI3): 8 259.0 (q, J(PC) = 13.2 Hz, CPh), 230.3 (dt, 2j(PCtrans)=34.5, "~J(PCcis)=5.3 Hz, CO), 153.4 (i-Ph), 127.6, 125 7, 123.5 (Pn), 40.4 (SC), 38.0 (CMe3), 21.9 (virtual t, 13.2 lqz, 2 PMe3 cis to CO), 21.0 (d, J(PC)=23.2 Hz, PMe3 trans to CO). 3tp NMR (CDCI3): 8 - 2 9 . 6 (t, J(WP)=216.3, J ( P P ) = 2 1 . 3 Hz, PMe 3 trans to CO), - 33.9 (d, J(WP) = 259.3, J(PP) = 21.3 Hz, 2PMe3 cis to CO). Anal. Cult. for C21H4~OP3SW (MW 618.39): C, 40.79; H, 6.68. Found: C, 41.00; H, 6.45%. 2.1.5. W(CPh)(SCtHn)(CO)(PMes)3(2e)
An oil dispersion containing 60% sodium hydride (0.96 g, 40 n~mol) is washed with pentane (4 × 50 ml). The sodium hydride is suspended in 100 ml tetrahydrofuran and excess cyelohexyl mercaptan (6.2 ml, 50 mmol) is added. The 3olution is stirred for 6 h, then the solvent is removed. The remain-
A. Mayr. T.-Y. Lee/InorganicaChirmcaActa252 (1996)131-139 ing white salt is washed with pentane (4 × 50 ml) and dried under vacuum. Sodium cyciohexylsulfide (0.5 g, 3.6 retool) is transferred to a 100 ml flask and suspended in 40 ml THF. Complex 1 ( 1.13 g, 2.0 mmol) is added to the flask, and the mixture is stirred at 50°C for 2 days The solvent is removed under vacuum, the product is extracted with pentane and recrystallized from the same solvent ( ,,- 150 ml) to gi ve golden brown crystals ( 1.17 g, 91%). M.p. 112-113°C. IR (CH2Ci2): 1883 (s, CO) cm - t . tHNMR (CDCI3): 87.05 (m,5H, Ph), 2.50-1.20 (m, l l H , C6HH), 1.61, 1.58 (m, 27H, P(CH3)3). 13C{IH} NMR: (CDCI3, 256 K): 8261.1 (t,J(WC) = 175.9, 2 J ( p C ) = I I . 4 Hz, CPh), 230.8 (dt, J(WC)=159.8, 2J(PCtrans) = 35.6, 2j(PCcis) = 6.2 Hz, CO), 153.3 (i-Ph), 127.5, 126.0, 123.5 (Ph), 44.8 (d, 3,/(PC) = 10.7 Hz, SCH), 40.9, 27.6, 25.7 (SCHCsH~o), 21.7 (virtual t, 14.4 Hz, 2P(CH3)3), 21.1 (d, J ( P C ) = 2 2 . 9 Hz, P(CH3)3). Anal. Calc. for C23H43OP3SW (MW 644.42): C, 42.87; H, 6.73. Found: C, 42.59; H, 6.70%.
2.1.6. [Et4NIIW(~CPh)(NC4H4)2(CO)(PMej)zI(3a) An oil dispersion containing 80% sodium hydride (0.057 g, 2.37 mmol) is washed with hexane ( 3 × l0 ml). The sodium hydride is suspended in 20 ml of THF and 0.048 g of pyrrole (0.72 retool) is added. The solution is refluxed for 20 min and then cooled to r.t. The filtered solution is transferred into a 50 ml flask containing a solution of 1 (0.062 g, 0.11 mmol) in 15 ml THF. The mixture is stirred for 16.5 h. After addition of excess Et4NCI (0.206 g, 1.24 mmol) the solvent is removed under vacuum. The product is extracted with THF and recrystallized from THF/hexane to give a small amount of the product. IR (THF): 1832 (s, CO ) em - 1. 2.1.7. [Et4N]IW(=CPh)(NC6Hs)2(CO)(PMe3)z] (3b) An oil dispersion containing 80% sodium hydride (0.048 g, 1.99 mmoi) is washed with hexane ( 3 x 10 ml). The sodium hydride is suspended in 20 ml THF and 0.094 g of indole (0.80 mmol) is added. After refluxing for 20 rain and cooling to r.t., the colorless solution is transferred into a 50 ml flask containing a solution of I (0.213 g, 0.38 retool) in 15 ml THF. After stirring for 14 h, excess Et4NCI (0.086 g, 0.52 mmol, pre-dried at 100°C under vacuum) is added. The solvent is removed under vacuum. The product is extracted with THF and recrystallized from THF/hexane to give tiny red crystals (0.163 g, 53%). IR (THF): 1835 (s, CO) c m - i. tH NMR (acetone-dt): 8 8A2--6.13 (m, 17H, Ph, NCsHt), 3.42 (q, J--7.3 Hz, 8H, NCH2CH3), 1.33 (t, Jffi7.3 Hz, 12H, NCH2CH3), 1.11 ( v ~ , a l t, 3.3 Hz, 18H, PMe3). 3~p NMR (acetone-d~): 8 - 8.95 (J(WP) ffi280.7 Hz, PMe3). Anal. Calc. for C3sHssN3OP2W (MW 815.68): C, 55.96; H, 6.80. Found: C, 55.75; H, 6.75%. 2.1.8. W(--CPh)(NC¢Hj-CHNMe-2)(CO)(PMe~)~ (4) Excess sodium (0.054 rag, 2.35 mmol) is added to a solution of pyrrolecarboxaldehyde-N-methylimine( 0.045 g, 0A2 mmol) in 20 ml hexane. After stirring for 8 h, the solvent is
133
removed under vacuum. The solid is taken up in 20 ml THF and filtered to remove unreacted sodium. "the solution is transferred into a 50 ml flask containing a solution of I (0.168 g, 0.30 retool) in 15 ml THF. After stirring for 10 h the solvent is removed under vacuum. The product is excxacted with hexane and recrystallized from the same solvent to give brown crystals (0.065 g, 51%). IR (THF): 1864 (s, CO) c m - L IH NMR (CDCI3): 8 8.03 (s, IH, CHNCH3), 7.197.15 (m, 5H, Ph), 6.83, 6.60, 6.17 (3H, C~-I~I), 3.90 (s, 3H, NCH3), 1.22 (virtual t, 3.3 Hz, 18H, 2PMe3). z3C NMR (CDCi3): 8 268.8 (t, J ( P C ) = 10.2 Hz, CPh), 244.3 (t, J(PC) =5.8 Hz, CO), 157.3, 153.3, 142.2, 137.3, 125.5 (2C), 124.0,113.8,112. i (CsH4N2, Ph), 51.7 (NCH3), 17A (virtual t, 11.6 Hz, PMe3). 31p NMR (CDCI3): 8 - 1 5 . 2 ( J(WP) = 281.0 Hz, PMe3). Anal. Calc. for ~ 3 o N e O P e W (MW 560.27): C, 42.88; H, 5.40. Found: C, 42.69; H, 5.43%.
2.1.9. Reaction of W(=CPh)(SCMejXCOXPMej)3(2d)with carbon monoxide A small amount of complex 2d is dissolved in "D-IF and placed under 1 arm of c~bon monoxide. After 12 h, the IR spectrum of the solution shows only two peaks at 1983 and 1912 c m - i . These absorptions indicate the presence of c/sW(-CPh)(SCMe3)(CO)(PMe3)2 (6). The solvent is removed under vacuum, and the residue is redissolved in CDCI3 to reco~'d the tH NMR spectrum. The spectrum is identical with that of the sample of 6 obtained by reaction of cis-W(-CPh) (Ci) (CO) 2(PMe3)2 with NaSCMe3. 2.1.10. Reaction of cis-W(~CPhXCI)(CO)2(PMe3)z with NaSCMej to give cis- W(-CPhXSCMe3X COXPMe3)z (6) Excess of sodium (0.060 g, 2.61 retool) is added to a solution of 50 pl of 2-methyl-2-propanethiol (0.040 g, 0.44 retool) in 20 ml of hexaue. After stirring for 8 h, the solvent is removed under vacuum. Then 15 ml TI-IF is added and the resulting solution is filtered to remove unreacted sodium. The solution is transferred into a 50 ml flask containing a solution ofcis-W(--CPh) (CI) (CO)2(PMe3)2 (0.062 g, 0.12 retool) in 15 ml THF. The mixture is stirred for 48 h. During this time, the color of the solution changes from yeh-w to orange and hhe carbonyl IR absorptions shift from 1999 and 1927 c m - i to 1983 and 1913 c m - L The solvent is removed ~mder vacuum. The product is extracted with hcxane and reorystallizcd from the same solvent to give a few milligramsof orange crystals. IR (THF): 1983 (s, CO), 1913 (s, CO) c m - L tH NMR (CDCI3): 8 7.23-7.18 (m, 5H, Ph), 1.66-1.63 (m, 18H, PMe3), 1.44 (s, 9H, CMe3). 2.1.11. Reaction of W(=-CPhXBrX COXPMes)3 (7) with carbon monoxide A small amount of complex 7 is dissolved in THF and placed under 1 arm of carbon monoxide. After 12 h, the IR spectrum of the solution shows three peaks at 2015,1929 and 1904 c m - L The peak at 1904 cm - t is due to unreacted starting material, the peaks at 2015 and 1929 c m - i indicate the presence of trans-W(--CPh) (Br) (CO)2(PMe3)2 (8).
134
A. Mayr. T.-Y. Lee/bwrganica ChimicaActa 252 (1996) 131-139
Table I Crystallographicdata for complexes2a and 2e
Formula Formulaweight a (.A) b (,A) c (p,) (°) /3 (°) y (o) v (A3) z Spacegroup Temperature Radiation(graphitemonochromator)(A) Linearabsorptioncoefficient(cm- t ) Scan mode 20 Range (°) Unique2eflectionswith IFo12>3oqFol2 Finalno. variables R'=E[IFol -F~I]IY-IFol R~= JEw( IFol - lEvi)"lEwFo 2] i/2 Standarderror observationunit weight
2a
2e
C21H36NOP3W 595.29 16.238(5) 9.487(3) 17.415(3) 90.0 100.80(2) 90.0 2635( I ) 4
C23H430[33s w
P2,1a
ambient Me Ka (A=0.71073) 46.661
644.43 ! 1.384(4) 9.265(3) 27.595(6) 90.0 90.0 90.0 2910(3) 4 P2,2,2, ambient Me Ka (A=0.71073) 42.964
0120
0120
0<20<60.8 4690 229 0.042 0.048 1.714
2.2<20<60.8 3115 262 0.029 0.029 1.086
~Quantityminimized(Y2w(IFol - IFcl)2); weightw= 1/(o'2 + 0.0016Fo2). The solvent is removed under vacuum, and the residue is redissolved in CDCI3 to record the ~H NMR spectrum. The tH NMR spectrum shows that 7 and 8 are present in a 60:40 ratio. Complex 8 was independently prepared by photoisomerization of c i s - W (=-CPh) (Br) (CO) 2(PMe3) 2.
of the P (3) Me3 ligand are disordered. The three carbon atoms C(19), C(20) and C(21 ) were kept isotropic, because when placed anisotropically, their temperature factors became too large. Selected crystallographic data for complexes 2a and 2e are listed in Table 1.
2.1.12. trans-W(=--CPh)(Br)(CO)z(PMe3)z (8) A solution of cis-W(-=CPh) (Br) (CO)2(PMe3) 2 (0.052
3. Results and discussion
g, 0.09 mmol) in 20 ml CH2C12 is irradiated with a 300 W projection lamp at 0°C for 80 min. Completion of the reaction is monitored by IR. During this time, the carbonyl IR bands shift from 2003 and 1930 c m - t to 2021 and 1930 c m - ~. The solvent is removed under vacuum and the product is recrystallized from diethyl ether to give orange-yellow crystals (0.041 g, 79%). IR (THF): 2016 (w, CO), 1929 (s, CO) era-". ~H NMR (CDCI3): 6 7.18-7.09 (m, 5H, Ph), 1.73 (virtual t, 3.7 Hz, 18H, PMe3). t3C NMR (CDCI3): ~ 269.2 (t, J(PC) = 10.2 Hz, CPh), 209.4 (t, J(PC) = 6.8 Hz, CO), 149.6 (i-Ph), 127.7, 127.5, 126.4 (CPh), 20.6 (virtual t, 13.7 Hz, PMe3). 3tp NMR (CDCI3): 6 - 2 7 . 5 (J(WP) = 274.5 Hz, PMe3). 2.2. Crytallographic studies
The general procedures for unit cell determination, data collection and structure solution have been previously described in detail [ 13]. All intensity measurements were made on an Enraf-Nonius CAD4A automated diffractometer, using a variable-rate, o.~--20 scan technique. Empirical absorption corrections (DIFABS) were applied. All calculations were performed using the TEXRAY programs. The structures were solved by direct methods and difference Fourier methods. In the structure of complex 2a, the three methyl groups
Reaction of [W(CPh)CI(CO)(PMe3)3] (1), with NaNC4H4, NaNCaH6, NaOC6Hs and NaSR (R--CMe3, C6H~I) in THF affords the alkylidyne tungsten complexes 2a--e containing pyrrolide, indolide, phenoxide and alkylsulfide ligands, respectively (Eq. ( 1) ). The products are recrystallized from hexane. In all complexes (2a-e) the anionic Ir donor ligand is occupying the coordination site trans to the alkylidyne ligand. This arrangement of the ligands is evident from the ~3C NMR data. The signal for the alkylidyne carbon atom in all of these compounds appears as a pseudo-quartet due to approximately equal couplings between the alkylidyne carbon atom and the three phosphorus atoms, while the signal of the carbonyl carbon atom appears in each case as a doublet of triplets due to large trans and small cis couplings.
o 1
o 2a: 2b: 2c: 2d: 2e:
~- ~-4~ ~ - NCsHs ~ - OCd.Is 3o~. SO~ 3 XR- SCsHi1
(1)
A. Mayr, T.-Y.
Lee/InorganicaChimica Acta 252 (1996)
The reaction of complex 1 with sodium pyrrolide and sodium indolide affords initially mixtures of the complexes 2a and 2b and the anionic complexes 3a and 3b (sodium salts), respectively, even when only equivalent amounts of the reagents are used. In these cases, the complexes 3a and 3b disappear after prolonged reaction times with concomitant complete formation of the complexes 2a and 2b. If, however, 2 equiv, of sodium pyrrolide and sodium indolide are added to 1, then complexes 3a and 3b form quantitatively as judged by IR (Eq. (2)). Complexes 3a and 3b were isolated as the tetraethylammonium salts, although 3a was not obtained in pure form due to its high reactivity. In the formation of 2e--e according to Eq. (1) no anionic intermediates of the type [W(CPh) (RX)2(CO)(PMe3)2] - could be detected by IR spectroscopy. Complex 4, a neutral analogue of compounds 3, was obtained by reaction of 1 with the sodium salt of pyrrole-2-carboxaldehyde methylimine (Eq. (3)). This anionic chelate ligand has previously been employed in reactions with alkylidyne complexes of the type [W(CR)Cl(pyfidine)2(CO)2] ( R = M e , Ph) to afford the ketenyl complexes [W(RCCO) (NC4H3-CHNMe-2) 2(CO) ] - [ 14]. The synthesis of the related complex $ from 1 and sodium diethyldithiocarbamate has previously been reported [ 15]. Me~ .PId~j c,~c--~
./!
21 ~t4C!/01-~12 r
[../!
NEt, ~ . ' - - ~ c - - .
1
135
131-139
1864 cm- ~.The ' 3C NMR resonance of the alkylidynecarbon atom is also relatively insensitive towards the introduction of the ~r donor ligands in the t r a n s position. The signal for 1 is at 6 261, and the signals for complexes 2 and 4 range from 6 259-270. The molecular structures of complexes 2a and 2e were determined by X-ray crystallography and are shown in Figs. 1 and 2, respectively. The crystallographic data for both compounds are collected in Table 1. The final atomic positional parameters of 2a and 2e are listed in Tables 2 and 3, selected bond distances and bond angles in "Fables 4 and 5, respectively. The structural features of 2a and 2e are within the expected range. In both structures, the ~r donor ligands and the phenyl group of the alkylidyne ligand are nea,,y coplanar. This feature may indicate the presence of an extended ~" system involving the ~rdonor ligand, the metal-carbon triple bond, and the phenyl group. A coplanar arrangement of these groups is also found in the related complex $ [ 14]. The alkylidyne iigand in complex 2e is only slightly bent, not
)
o(1)
(2)
3a: ~ - L'~H4
3b: )~- NC~o
Iq~P
._~ N ~ W ~ . . . _ C ~ p
...,/!
w~ O
_/I--
h
(3)
~P
1
•
~
Fig. I. Molecularst~mctureof complex2a.
4
C_.e~.- S Iv~
)
0(1) C(14)
s
The replacement of the chloride ligand in complex 1 by the ~" donor ligands exerts only a small influence on the IR stretching frequency of the cart~3nyi lignnd, e.g. v(CO) o f l shifts from 1896 to 1888 c m - ' for 2a. On the other hand, the replacement of PMe3 by pyrrolide or indolide in the position t r a n s to the carbonyl ligand in 3a and 3b causes a significant shift of the carbonyl stretching frequency to lower energies. For example, the carbonyl stretching frequency of 3a is at 1832 c m - ' and even in the neutral complex 4 it is as low as
C(21)
Fig. 2. Molecular sU-acture of corn flex 2e.
136
A. Mayr, T.- K Lee/Inorganica Chimica Acre 252 (1996) 131-139
Table 2 Final atomiccoordinatesand B,~ valuesof complex2a Atom
x
w(I) P(l) P(2) P(3) O(1) N(I) C(I) C(2) C(3) C(4) C(5) C,6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21)
0.39937(I) 0.07701(3) 0.5181(1) -0.0669(2) 0.4981(I) 0.1849(2) 0.2907(1) 0.0111(3) 0.2611(4) 0.2451(7) 0.4221(4) 0.2601(7) 0.3659(4) -0.0601(6) 0.3263(4) -0.1525(7) 0.2606(5) -0.1039(8) 0,2220(6) -0.190(1) 0.2474(7) -0.324(1) 0.3098(8) -0.377(1) 0.3511(6) -0.291(1) 0.3132(5) 0.1877(8) 0.5390(6) -0.226(1) 0.5078(6) -0,140(1) 0.6211(5) 0.012(I) 0.4683(7) 0.265(1) 0.460(1) 0.395(2) 0.409(1) 0.472(I) 0.3846(7) 0.386(I) 0.5537(7) 0.341(1) 0.5819(8) 0.085(1) 0.4469(7) 0.242(2) 0.247(1) -0.165(2) 0,309(1) 0.016(2) 0.206(1) 0.138(3)
y
z
Table 4 Selectedbond distances (A) and bond angles (°) for complex2a B~q
0.74316(2) 3.87(1) 0.7012(I) 4.90(8) 0.8541(I) 5.01(8) 0.6277(1) 6.2(I) 0,8052(4) 9.6(4) 0.6688(4) 6.3(3) 0.8036(4) 4.2(3) 0.8525(4) 4.5(3) 0.8868(5) 5.7(4) 0.9334(5) 7.2(5) 0.9476(6) 8.0(6) 0.9151(7) 9.6(6) 0.8676(6) 8.6(5) 0.7804(5) 5.9(4) 0.7571(6) 8.6(5) 0.6030(5) 8.2(5) 0.7080(7) 9.6(6) 0 . 6 1 2 4 ( 7 ) 10.6(7) 0,578(1) 15(I) 0.611(1) 11.3(8) 0.6666(6) 9.1(6) 0 . 8 3 4 7 ( 6 ) 10.8(7) 0 . 9 0 7 6 ( 6 ) 11.4(7) 0 . 9 3 3 2 ( 6 ) 13.0(8) 0.627(1) 16.3(5) 0.528(1) 16.6(5) 0.602(1) 22.1(8)
Table 3 Final atomiccoordinatesand B~ valuesof complex2e Atom
x
y
z
B~4
W(l) P(I) P(2) P(3) O(!) N(I) C(i) C(2) C(3) C(4) C(5) C16) C(7) C(8) C(9) C(IO) C(II) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(2~) C(21)
0.39937(1) 0.5181(1) 0.4981(1) 0.2907(!) 0.2611(4) 0.4221(4) 0.3659(4) 0.3263(4) 0.2606(5) 0.2220(6) 0.2474(7) 0.3098(8) 0.3511(6) 0.3132(5) 0.5390(6) 0.5078(6) 0.6211(5) 0.4683(7) 0.460(!) 0.409(!) 0.3846(7) 0.5537(7) 0.5819(8) 0.4469(7) 0.247(1) 0.309(I) 0.206(1)
0.07701(3) -0.0669(2) 0.1849(2) 0.0111(3) 0.2451(7) 0.2601(7) -0.0601(6) -0.1525(7) -0.1039(8) -0.190(1) -0.324(1) -0.377(i) -0.291(!) 0.1877(8) -0.226(1) -0.140(I) 0.012(I) 0.265(!) 0.395(2) 0.472(!) 0.386(I) 0.341(I) 0.085(!) 0.242(2) -0.165(2) 0.016(2) 0,138(3)
0.74316(2) 0.7012(1) 0.8541(!) 0.6277(i) 0.8052(4) 0.6688(4) 0.8036(4) 0.8525(4) 0.8868(5) 0.9334(5) 0.9476(6) 0.9151(7) 0.8676(6) 0.7804(5) 0.7571(6) 0.6030(5) 0.7080(7) 0.6124(7) 0.578(!) 0.611(1) 0.6666(6) 0.8347(6) 0.9076(6) 0.9332(6) 0.627(1) 0.528(1) 0.602(I)
3.87(1) 4.90(8) 5.01(8) 6.2(!) 9.6(4) 6.3(3) 4.2(3) 4.5(3) 5.7(4) 7.2(5) 8.0(6) 9.6(6) 8.6(5) 5.9(4) 8.6(5) 8.2(5) 9.6(6) 1&6(7) 15(1) !!.3(8) 9.1(6) 15.8(7) 11.4(7) 13.0(8) 16.3(5) 16.6(5) 22.1(8)
Bond distances
W(I)-P(I) W(I)-P(2) W(I)-P(3) W(I)-N(I) W( I )-(2( I ) W( I )~C(8) P( I )-C(9) P(I)-C(10) P(1)-C(II) P(2)-C(16) P(2)-C(17) P(2)-C(18) P(3)-C(19) P(3)--C(20)
2.576(2) 2.488(2) 2.493(2) 2.238(6) 1.819(6) 1.954(8) 1.794(9) 1.825(9) 1.818(8) 1.80( I ) 1.77(1) 1.818(9) 1.81(2) 1.81(2)
P(3)--C(21) O(I)--C(8) N(I)-C(12) N( I)--C(15) C( I )--C(2) C(2)-C(3) C(2)-C(7) C(3)--C(4) C(4)-C(5) C(5)-C(6) C(6)-C(7) C(12)-C(13) C(13)-C(14) C(14)-C(CI5)
1.82(2) 1.157(8) 1.34(1) i.34(!) 1.454(9) 1.40( I ) 1.38( I ) 1.38(i) 1.35(I) 1.35( 1) 1.41(I) !.36(2) 1.31(2) 1.38(2)
91.75(6) 95.32(7) 91.9(2) 96.0(2) 176.9(2) 170.06(7) 88.7(2) 93.7(2) 85.3(2) 84.1(2) 92,5(2) 87.7(2) 171.6(3) 88.9(3) 83.3(3) !11.6(3) 121.7(3)
W(I)-P(I)-C(I I) W(I)-P(2)-C(16) W(I)-P(2)-C(17) W(I)-P(2)-C(18) W(I)-P(3)-C(19) W(I)-P(3)-C(20) W(I)-P(3)-C(21) W(1)-N(I)-C(12) W( 1)-N( i)-C(15) C(12)-N(1)-C(15) W( I)-C( I )--C(2) W(I)-C(8)-O(I) N(I)-C(12)-C(13) N( I)-C(15)-C(14) C(12)-C(13)--C(14) C(13)-C(14)--C(15)
il9.4(4) !17.8(4) 120.5(4) 113.0(4) !16.7(5) 122.9(6) !15.1(7) 128.9(7) 125.8(7) 104.9(8) 169.5(5) 175.3(7) 109(I) I11(1) ll0(l) 105(i)
Bond angles
P(I)-W(I)-P(2) P(I)-W(I)-P(3) P(I)-W(I)-N(I) P(I)-W(I)-C(I) P(I)-W(I)-C(8) P(2)-W(I)-P(3) P(2)-W(I)-N(I) P(2)-W(I)-C(I) P(2)-W(I )-C(8) P(3)-W(I)-N(I) P(3)-W(I)-C(I) P(3)-W(i)-C(8) N(I)-W(I)-C(I) N(I)-W(I)-C(8) C(I)-W(I)-C(8) W(I )-P(I)-C(9) W(I)-P(I)-C(10)
more than in many other alkylidyne complexes. In complex 2a, however, the a!kylidyne ligand is nat only bent by about 10°, but also pushed towards the carbonyl ligand. The C( 1) W ( 1 ) - C ( 8 ) angle is only 83.3(3) °. This feature is apparently a consequence of steric interactions of the coplanar pyrrolide and phenyl groups with the central trimethylphosphine ligand. This situation is clearly visible in Fig. 3. The shortest interligand distance between the phenyl group and the trimethylphospine ligand in 2a, C ( 7 ) - C ( 9 ) is about 4.0 ,~, which is the same as the corresponding C( 13)-C(17) distance in 2e. In contrast to 2e, however, where the P(2)Me3 ligand can relax towards the sterically little demanding S( 1 ) atom, the P( 1)Me3 ligand in 2a cannot move away from the alkylidyne ligand because of the presence of the coplanar pyrrolide ligand. There are correspondingly short distances between C(12) on the pyrrolide ligand and the carbon atoms C(10) and C ( I I ) on the central PMe3 ligand of about 3.9 and 3.6 ,~, respectively. Consequently, the bending of the alkylidyne ligand in 2a and its shift towards the carbonyl ligand result from sterie interactions and are not due to an intrinsic electronic influence of the 1r donor ligand. Nevertheless, the coplanar arrangement of the pyrrolide and phenyl groups, which is ultimately responsible for these steric repulsions, may be the stabilized by ~r conjugation through the
137
A. Mayr, 7".-Y.Lee I Inorganica Chimica Acta 252 (1996) 131-139
Table5 Selectedbonddistances(,~) andbondangles(o) for complex2e Bonddismnces
W(I)-S(I) W(I)-P(I) W(I)-P(2) W(I)-P(3) W(I)-C(7) W(I)~(23) S(I)-C(I) P(I)-C(14) P(I)-C(15)
2.576(2) 2.482(2) 2.533(2) 2.480(3) 1.817(7) 1.979(8) 1.836(8) 1.802(9) 1.816(8)
P(I)-C(16) P(2)-C(17) P(2)~C(18) P(2)-C(19) P(3)-C(20) P(3)-C(21) P(3)-C(22) O(1)-C(23)
1.833(8) 1.80(I) 1.834(9) 1.82(I) 1.83(I) 1.79(I) !.80(I) 1.151(9)
93.63(7) 79.81(7) 92.36(8) 178.3(2) 90.2(2) 92.32(8) 172.08(7) 87.8(2) 87.8(2) 93.83(8) 101.1(2) 170.0(2) 86.2(2) 87.0(2)
C(7)-W(1)-C23 W(I)-S(1)-C(I) W(I)-P(i)-C(14) W(I)-P(I)-C(15) W(I)-P(I)-C(16) W(I)-P(2)-C(17) W(I)-P(2)-C(18) W(I)-P(2)--CI9 W(I)-P(3)-C(20) W(I)-P(3)-C(21) W(i)-P(3)-C(22) S(I)-C(I)~C(2) S(I)-C(I)-C(6) W(I)-C(7)-C(8)
88.9(3) 112.2(2) 112.9(3) 117.5(3) i19.7(3) 115,1(3) !i7,2(3) 117.0(3) 118.4(4) !11.6(5) 121.1(4) !10.8(6) i11.6(6) 175.6(6)
Bondang~s
S(I)-W(I)-P(I) S(I)-W(I)-P(2) S(I)-W(I)-P(3) S(I)-W(I)-C(7) S(i)-W(I)-C23 P(i)-W(I)-P(2) P(I)-W(I)-P(3) P(I)-W(I)--C(7) P(I)-W(i)-C23 P(2)-W(I)-P(3) P(2)-W(I)-C(7) P(2)-W(I)-C23 P(3)-W(I)-C(7) P(3)-W(I)-C23
metal-carbon triple bond. The methylidyne ligand in [ W (=-C-H) (n-butyl) ( Me2PCH2CH2PMe2) 2] was found to be bent by about 18° [ 16]. In this case, the bendin~ may be induced or facilitated by the presence of the trans n-butyl ligand, which is a very strong donor, although primarily a 6-
donor. Probably as a result of the steric interactions,the bond distance between tungsten and the central trimethylphosphine ligand is distinctly longer in 2a, W( l ) - P ( 1 ) -- 2.576(2) ,A, than in 2e, W ( I ) - P ( 2 ) =2.533(2) ,~. This feature is consistent with the observed facile substitution of one PMe3 ligand in 2a and 2b to give the anionic complexes 3. As a preliminary test of the reactivity of the new ~rdonor ligand-substituted alkylidyne tungsten complexes, a solution of compound 2d was exposed to one atmosphere of carbon monoxide (Eq. (4)). After 12 h, the IR spectrum of the solution showed two strong absorptions of similar intensity at 1983 and 1912 cm- t. This pattern is characteristic of a cis-dicarbonyl system. The identity of the product as cis[W(CPh)(SCMe3)(CO)2(PMe3)2] (6), was confirmed by the synthesis of the same compound from c/s[W(CPh)(SCMe3)(CO)2(PMe3)2] (6), was confirmed by the synthesis of the same compound from cis[W(CPh)CI(CO)2(PMe3)2] and NaSCMe3. The reactivity
u~cs-- =
c(7)
(a)
c(.)
c~) c(lo)
(1:)
Fig. 3. View of the complexes 211 (a) and 2e (b) showing the plane con-
rainingthe alkylidyneligand,the CO ligand,the ~"donorligandand one trimethyiphosphineiigand.The methylgroupsof the trimethylphosphine ligandsaboveandbelowthisplanehavebeenomittedfor clarity.
C.Ollatm
~ ~.~:s~*~c--~
2d
ue~i . . - ~
(4)
6
co/tarm tz,
o 7
c(12)
~
~:Y~
(5~
~ / o 8
of 2d towards carbon monoxide differs from that of the analogous brmno complex [W(CPh)Br(CO)(PMe3)3] (7). When a THF solution of 7 is placed under one atmosphere of carbon monoxide, an equilibrium mixture of 7 and trans[ W(CPh)Br(CO)a(PMe3) 2] (8), in a relative ratio of 60:.40 is obtained (Eq. (5)). The formation oftbe trans complex 8 is as expected. The substitution of the central uimethylphosphine ligand in complexes of the type [W(CPh)X(CO)(PMe3) 3] ( X = halogen) is a proven method for the synthesis of tungsten alkylidyne complexes of the general type trans- [W(CPh)X(CO) (L) (PMe3)2] [ 17]. The complete conversion of complex 2d upon reaction with carbon monoxide under I atm can be attributed to the increasedelectronrichness of the system, compared to complex 7, but the formation of the c/s complex 6 represents a qualitative difference in reactivity between the thiolato- and bromo-substituted alkylidynetungsten complexes 2d and 7. In the reaction of 2d with carbon monoxide, no :~'kylidyne-carbonyl conpiing product, i.e. a ketenyl tungsten complex [ 18], was observed. In contrast, complex 5 easily takes up carbon monoxide to afford the ketenyl tungsten complex [W(PhCCO) (S2CNEt2) (CO) (PMe3)2] [ 15].
138
A. Mayr, Z- Y. Lee/Inorganica Chimica Acta 252 (1996) 131-139
Several low-valent aikylidyne metal complexes which are of interest in the current context have been reported in the literature. Fischer and co-workers prepared complex 9 containing a diphenylarsenido ligand [ 19]. Hopkins and coworkers recently described a family of acetylide-substituted tungsten alkylidyne complexes (10) [20]. As indicated by the electronic spectra of these compounds, there is significant ~-conjugation between the M = C and C---C systems. Attempts in our laboratory to synthesize alkylidyne complexes containing alkyne ligands of the type of complex 11 resulted in the isolation of the alkylidene alkyne tungsten complex (12) [ 21 ]. Alkylidyne alkyne complexes of the type of complex 11 are presumably intermediates in the formation of complex 12, but due to 7r donation by the alkyne ligand, the alkylidyne carbon atom is quite basic and easily picks up a proton [22]. Thermally labile alkylidyne alkyne tungsten complexes of the type of complex 13 were successfully characterized by Mayer and co-workers [ 23 ].
5. Supplementary material Further details of the crystal structure investigations of complexes 2a and 2e may be obtained from the authors upon request.
Acknowledgements Support for this work by the Donors of the Petroleum Research Fund, administered by the American Chemical Society, and by the National Science Foundation is gratefully acknowledged. We thank Michael P. Rickenbach and Professor Stephen A. Koch for the X-ray crystallographic studies and Michael A. Kjelsberg and On Ki Cheung for preliminary experimental work.
Mez?'7 I .~e2 References
/Ph
/eh
/
IZn~C [ ..~e3 ~
M~/!, ,z"
"~'/~ ,t oC/! o
oC/! 14
0
"J"~°',3
15
Schrock and Williams have recently reported the synthesis of several low-valent alkylidyne rhenium complexes containing aryloxide and alkoxide ligands [24]. "lae existence of the electronically unsaturated species 14 and 15 is without doubt a consequence of the stabilization of the metal center by the ~r donor ligands.
4. Conclusions The synthesis of tungsten alkylidyne complexes of the Fischer-type containing pyrrolide, indolide, phenoxide and aikylsulfide ligands has been demonstrated. The presence of the ~r donor ligands leads to an increase of the electronrichness of the metal-alkylidyne system. In reactions with the ~acid carbon monoxide, these 1rdonor ligand-substituted systems exhibit an increase in reactivity compared to the corresponding halo-substituted Fischer-type alkylidyne complexes.
[ I ] E.O.Fischer,Angew. Chem., 86 ( 1974) 651;Adv. Organomet. Chem., 14 ( 19761 1. [2l R.R. Schrock,Ace. Chem. Res., 19 ( 19861 342. [3] (a) H. Fischer, P. Hofmann,F.R. Kreissl, R.R. Schrock, U. Schubert and K Weiss, Carbyne Complexes, VCH, Weinheim, 1988; (b) H.P. Kim and R.J. Angelici,Adv. Organomet. Chem., 27 (1987) 51; (c) M.A. Gallop and W.R. Roper, Adv. Organomet. Chem., 25 (1986) 121; (d) F.G.A. Stone,Adv. Organomet. Chem., 31 (1991) 53; (e) A. Mayrand H. Hoffmeister,Adv. Organomet. Chem., 32 (19911 227; (f) A. Mayrand C.M. Bastos, Prog. Inorg. Chem, 40 ( 19921 l. 14l (a) N.M. Kosti~ and R.F. Fenske, Organometallics, I (1982) 489; (b) P. Hofmann,Carbyne Complexes, VCH,Weinheim, 1988. [ 5] A. Mayr, Transition Metal Carbyne Complexes, NATO AS! Set. (7,392 (1993) 219. [6l P.F. Engel and M. Pfeffer,Chem. Rev., 95 ( 19951 2281. [7] (a) H. Fischerand C. Troll, Chem. Bet., 126 (t993) 2373; (b) M.R. Terry, L.A. Mercando,C. Kelly,G.L. Geoffroy,P. Nombel,N. Lugan, R. Mathieu, R.L. Ostrander, B.E. Owens-Waltermire and A.L. Rbeingold, OrganometaUics, 13 (1994) 843. [ 8] M.D.Mortimer,J.D. Carterand L. McEIwee-White,Organometallics, 12 ( 19931 4493. [9] A. Mayf, M.F. Asaro, MA. Kjelsberg,K.S. Lee and D. Van Engen, Organometallics, 6 (1987) 432. [ 10l P. Steil and A. Mayr, Z. Naturforsch., Teil B, 47 (1992) 656. [ ! i ] G.A. McDermott, AM. Domes and A. Mayr, OrganometaUics, 6 ( 19871 925. [12] B. Emmert, K. Diehl and F. Gollwitzer, Chem. Bet., 62 (1929) 1733. [ 13l S. Lincolnand S.A. Koch,lnorg. Chem., 25 (1986) 1594. [14l A. Mayr, G.A. McDermott, A.M. Dorries and D. Van Engen, Organometallics, 6 (19871 1503. [ 15l A. Mayr, R.T, Chang, T.-Y. Lee, O,K. Cheung,"M.A. Kjelsberg, G.A. McDermott and D. Van Engen, J. Organomet. Chem., 479 (1994) 47. [ 16] J. Manna, S.J. Geiband M.D. Hopkins,Angew. Chem., Int. Ed. Engl., 32 (1993) 858. [ 17] A. Mayr, T.-Y. Lee, M.A. Kjelsbergand K,S. Lee, Organometallics, 13 (1994) 2512.
A. Mayr, T.- Y. Lee / lnorganica Chimica Acta 252 (1996) 131-139 [18]F.R. Kreissl, in A. de Meijere and H. tom Dieck (eds.), Organometallics in Organic Synthesis, Springer, Berlin, 1987, p. 105. [ 19] A.C. Filippou, E.O. Fischer, K. Ofele and HG. Air, J. Organomet. Chem., 308 (1986) 1 I. [ 20 ] J. Manna, S 3. Geib and M.D. Hopkins, J. Am. Chem. Soc., 114 ( 1992 ) 9199.
139
[21] A. Mayr, K.S. Lee, MA. Kjelsberg and D. Van Engen, J. Am. Chem. Soc., 108 (1986) 6079 [22] A. Mayr, Comments inorg. Chem., i 0 (1990) 227. [23] L.M. Atagi, S.C. Critchlow and J.M. Mayer, J. Am. Chem. Soc., 114 (1992) 9223. [24] D.S. Williams and R.R. Schrock, Organometallics, 13 (1994) 2101.
InorganicaChimicaActa252 (1996) 131-139
Fischer-type alkylidyne tungsten complexes containing strong 7r donor ligands Andreas Mayr a,b,:~,l,Tsung-Yi Lee
a
a Department of Chemisuy. State University of New York at Stony Brook. Stony Brook, NY ! 1794-3400. USA h Department cfChemistry, The University ofHong Kong, Poyulam Road. Hong Kong, Hong Kong
Received 19 March 1996;revised3 June 1996
Abstract Reaction of [W(CPh)CI(CO)(PMe3)3] (1), with NaNC4H4, NaNCsH6, NaOC6Hs and NaSR (R=CMe3, C6HH) in THF affords the alkylidyne tungsten complexes [W(CPh)X(CO)(PMe3)3] (2a-e), containing pyrrolide, indolide, phenoxide and alkylsulfide ligands, X, respectively. The ¢r donor ligands X occupy the coordination site trans to the alkylidyne ligand. The anionic complexes [NEh][W(CPh)X2(CO)(PMe3)2] ((3a) X=NC,,H,,), ((3b) X=NCsH6), form upon reaction of I with 2 equiv, of NaNC41-h and NaNCsH6 in THF, followed by metathesis with NEt4CIin CH2C12.Reaction of I with the sodium salt of pyrrole-2-carboxaldehyde methylimine affords [W(CPh)(NC4H3-CHNMe-2 ) (CO)(PMe3)2] (4). The solid state structures of complexes 2a and 2e were determined by X-ray crystallography. Complex 2d reacts in THF solution with carbon monoxide to afford cis- [W(CPh) (SCMe3) (CO)2(PMe3)2] (6). In contxast, the analogous bromo complex [W(CPh)Br(CO)(PMe3)3] (7) gives under the same conditions an equilibrium mixture of 7 and trans[W(CPh)Br(CO)2(PMe3)2]. Keywords: Crystalstructures;Tungstencomplexes;Alkylidynecoml:-iexes;lr Donorligandcomplexes
!. Introduction Strong ~r donor ligands are strikingly absent in Fischertype [ 1 ], or low-valent, alkylidyne metal complexes, but are commonly found in Schrock-type [2], or high-valent, systems [3]. This situation is a consequence of the electronic structure of these compounds [ 4]. The Schrock-type systems possess empty low-lying d orbitals while the Fischer-type systems do not. Since Fischer-type alkylidyne metal complexes are, in most cases, electronically saturated species, 7r donor ligands will not enhance their stability. Rather, it can be expected that the presence of ~'donor ligands will bolster their reactivity. In particular, the presence of strong Ir donor ligands should enhance the reactivity towards electrophiles. This feature could be quite useful, since, except for the addition of protons, only few reactions of Iow-valent alkylidyne complexes with electrophiles have been described [ 3]. The presence of ~"donor ligands might also facilitate intramolecular alkylidyne-ligand coupling reactions [5]. Among the strategies to develop the synthetic potential of low-valent alkylidyne metal complexes [6], two different approaches * Con'espor~dingauthor. 1On leaveat the Universityof HongKong. 0020-16931961515.00© 1996ElsevierScienceS.A. All rightsreserved P!!S0020-1693(96)05306-6
have been particularly successful: reactions of cationic Group 7 metal aikylidyne complexes with nucleophilic substrates [ 7 ] and photochemical transformations [ 8 ] of functionalized Group 6 metal alkylidyne complexes. Clearly, the development of new methods to activate alkylidyne ligands towards reactions with Lewis-acids would be of considerable synthetic value. The introduction of strong ~rdonor ligands could serve this purpose. In the pursuit of this goal, several alkylidyne tungsten complexes of the Fischer-type containing nitrogen, oxygen and sulfur ¢r donor ligands have been prepared.
2. Experimental Standard inert-atmosphere techniques were used in the execution of the experiments. The solvents methylene chloride (Call2), diethyl ether, tetrahydrofuran (Na/benzophenone) and hexane (CaH2) were dried and distilled prior to use. Complexes 1 [9] and 7 [10] and cis[ W(CPh) Cl(CO) 2( PMe3 ) 2] [ 11 ] were prepared as previt, usly reported. Pyrrole-2-carboxaldehyde methylimine was prepared as reported in the literature [ 12]. All other reagents were obtained from commercial sources. The NMR spectra were measured at 250 or 300 MHz (for tH NMR) at room
132
A. Mayr. T.-Y. Lee / Inorganica ChimicaActv 252 (1996) 131-139
temperature, unless otlaerwise noted; solvent peaks were used as internal reference; the chemical shifts are reported in 8 relative to TMS. Elemental analyses were performed by Schwarzkopf Micronalytica! Laboratory. 2.1. Syntheses 2.1.1. W(CPh)(NC4H4)(CO)(PMea)3 (2a)
An oil dispersion containing 80% sodium hydride (0.080 g, 3.32 mmol) is washed with hexane ( 3 × 15 mi). The sodium hydride is suspended in 25 ml THF and 77.0 /zl distilled colorless pyrrole (0.075 mg, 1.11 mmol) is added. The solution is refluxed for 50 rain and filtered after cooling to r.t. A pale yellow NaNCaH4 in THF solution is obtained. Complex 1 (0.437 g, 0.77 mmol) is added to a 50 ml flask containing 20 ml THF, and the solution of NaNC4I-I4 in THF is added. After stirring for 36 h, the solvent is removed under vacuum. The product is extracted with diethyl ether and recrystallized from the same solvent to give orange crystals (0.139 g, 30%). IR (THF): 1888 (s, CO) cm - j . IH NMR (THF-ds): 8 7.11-7.03 (m, 5H, Ph), 6.4! (s, 2H, NCH), 5.81 (s, 2H, NCCH), 1.75 (d, J(PH) =6.5 Hz, 9H, PMe3 trans to CO ), 1.40 ( virtual t, 2.5 Hz, 18H, 2PMe3 cis to CO ). 13C NMR (THF-ds): ~$269.7 (q, J(PC) = i0.8 Hz, CPh), 227.0 (dt, 2j(PCtrans)=39.5, 2J(pccis)=7.2 Hz, CO), 153.8 (i-Ph), 131.9, 131.8, 128.5, 128.3, 125.2, 107.6 (2C) (Ph, NC4H4), 23.3 (d, J(PC ) = 21.9 Hz, PMea trans to CO ), 20.8 (t, J ( P C ) = 12.6 Hz, 2PMe3 cis to CO). alp NMR (THF-ds): c$ - 214.6 (d, J(WP) = 268.4, J(PP) = 18.2 Hz, 2PMe3 cis to CO), - 225.1 (t, J(WP) = 213.6, J(PP) = 18.2 Hz, PMea trans to CO). 2.1.2. W( CPh )( NCsH6)( CO )( PMe j)3 (2b )
An oil dispersion containing 80% sodium hydride (0.048 g, 1.99 mmol) is washed with hexane ( 3 × 10 ml). The sodium hydride is suspended in 20 ml THF and 0.075 g indole (0.64 mmol) is added. The solution is refluxed for 20 min and filtered after cooling to r.t. A colorless solution of NaNCsH6 in THF is obtained. Complex 1 (0.293 g, 0.52 mmol) is added to a 50 ml flask containing 15 ml THF, and the solution ol NaNCsH6 is added. The mixture is stirred for 36 h. The solvent is removed under vacuum, the product is extracted with diethyl ether and recrystalhzed from the same solvent to give orange needle crystals (0.135 g, 40%). IR (THF): 1882 (s, CO) cm -I. IH NMR (THF-ds): 87.696.20 (m, IIH, Ph, NCsHt), 1.77 (d, J ( P H ) = 6 . 3 Hz, 9H, PMea trans to CO), 1.38 (virtual t, 3.0 Hz, 18H, 2PMea cis to CO). maCNMR (THF-da): 8 270.0 (q, J(PC) = 10.7 Hz, CPh), 226.0 (m, CO), 148.6 (i-Ph), 14C.8, 140.6, 128.8, 128.5, 125.6, 121.7, 119.6, 118.4, 117.8, 116.5, 101.1 (Ph, NCsH6), 23.0 (d, J(PC ) = 21.5 Hz, PMea trans to CO ), 20.8 (virtual t, 12.6 Hz, 2PMea cis to CO). alp NMR (THF-d8): 8 -214.6 (d, J(WP) =268.4, J(PP) = 18.2 Hz, 2PMea cis to CO), - 225. ! (t, J(WP) = 213.6, J(PP) = 18.2 Hz, PMe3 trans to CO ~. anal. Calc. for C2sHasNOPaW (MW 645.35 ): C, 46.53; H, 5.93. Found: C, 46.62; H, 6.19%.
2.1.3. W(CPh):OCtHs)(CO)(PMesb (2c)
Phenol (0.074 g, 0.79 mmol) is added to a flask containing 15 ml hexane, and an excess of sodium (0.086 g, 3.74 mmoi) is added. The solution is stirred at r.t. for 4 h and the solvent is removed under vacuum. Excess sodium is removed mechanically. The solid NaOCtHs is transferred to a 50 ml flask and 25 ml THF is added. Then a solution of 1 (0.106 g, 0.19 mmol) in 15 ml THF is added. After stirring for 19 h, the solvent is removed under vacuum. The product is extracted with diethyl ether and recrystallized from the same solvent to give red-orange crystals (0.050 g, 43%). IR (THF): 1883 (s, CO) cm -I. IH NMR (CDCI3): ~ 7.106.36 (m, 10H, CPh, OPh), 1.61 (d, J ( P H ) = 6 . 5 Hz, 9H, PMe3 trans to CO), 1.54 (virtual t, 2.9 Hz, 18H, 2PMe3 cis to CO). 13C NMR (CDCIa): 8 263.3 (m, CPh), 227.2 (dt, 2J(PCtrans)=47.8, 2j(PCcis)=5.3 Hz, CO), 168.9 (iOPh), 152.7 (i-Ph), 128.8, 127.5, 127.1,123.7, 119.3, 112.7 (CPh, OPh), 20.8 (virtual t, 12.6 Hz, 2PMe3 cis to CO), 19.6 (d, J(PC) =20.3 Hz, PMe3 trans to CO). alp NMR (CDCla): 8 - 1 8 . 3 (d, J(WP)=273.6, J ( P P ) = 2 1 . 3 Hz, 2PMe3 cis to CO), - 22.8 (t, J(WP) = 225.3, J(PP) = 21.3 Hz, PMea trans to CO). Anal. Caic. for C2aHaTO2PaW (MW 622.32): C, 44.39; H, 5.99. Found: C, 44.23; H, 6.00%. 2.1.4. W(CPh)(SCMe~)(CO)(PMea)3(2d)
2-Methyl-2-propanethiol ( 1.60 g, 17.74 mmoi) is added to a Schlenk flask containing 30 ml hexane, and an excess of sodium (1.523 g, 66.25 mmol) is added. The mixture is stirred at r.t. for 8 h. The solvent is removed under vacuum. Excess sodium is removed mechanically from the white salt. The solid NaSCMe3 is transferred into a 100 ml flask containing 60 ml THF. Then a solution of 1 (1.!7 ° g, 2.086 mmol) in 20 ml THF is added. After stirring for 24 h, the solvent is removed under vacuum. The product is extracted with hexane and recrystallized from the same solvent to give red-orange crystals (1.103 g, 86%). IR (THF): 1883 (s, CO) cm - t . IH NMR (CDCI3): 8 7.27 (s, 5H, Ph), 1.64 (virtual t, 3.0 Hz, 18H, 2PMe3 cis to CO), 1.60 (d, J(PH ) = 7.0 Hz, 9H, PMe3 trans to CO ), 1.41 (s, 9H, CMea ). taC NMR (CDCI3): 8 259.0 (q, J(PC) = 13.2 Hz, CPh), 230.3 (dt, 2j(PCtrans)=34.5, "~J(PCcis)=5.3 Hz, CO), 153.4 (i-Ph), 127.6, 125 7, 123.5 (Pn), 40.4 (SC), 38.0 (CMe3), 21.9 (virtual t, 13.2 lqz, 2 PMe3 cis to CO), 21.0 (d, J(PC)=23.2 Hz, PMe3 trans to CO). 3tp NMR (CDCI3): 8 - 2 9 . 6 (t, J(WP)=216.3, J ( P P ) = 2 1 . 3 Hz, PMe 3 trans to CO), - 33.9 (d, J(WP) = 259.3, J(PP) = 21.3 Hz, 2PMe3 cis to CO). Anal. Cult. for C21H4~OP3SW (MW 618.39): C, 40.79; H, 6.68. Found: C, 41.00; H, 6.45%. 2.1.5. W(CPh)(SCtHn)(CO)(PMes)3(2e)
An oil dispersion containing 60% sodium hydride (0.96 g, 40 n~mol) is washed with pentane (4 × 50 ml). The sodium hydride is suspended in 100 ml tetrahydrofuran and excess cyelohexyl mercaptan (6.2 ml, 50 mmol) is added. The 3olution is stirred for 6 h, then the solvent is removed. The remain-
A. Mayr. T.-Y. Lee/InorganicaChirmcaActa252 (1996)131-139 ing white salt is washed with pentane (4 × 50 ml) and dried under vacuum. Sodium cyciohexylsulfide (0.5 g, 3.6 retool) is transferred to a 100 ml flask and suspended in 40 ml THF. Complex 1 ( 1.13 g, 2.0 mmol) is added to the flask, and the mixture is stirred at 50°C for 2 days The solvent is removed under vacuum, the product is extracted with pentane and recrystallized from the same solvent ( ,,- 150 ml) to gi ve golden brown crystals ( 1.17 g, 91%). M.p. 112-113°C. IR (CH2Ci2): 1883 (s, CO) cm - t . tHNMR (CDCI3): 87.05 (m,5H, Ph), 2.50-1.20 (m, l l H , C6HH), 1.61, 1.58 (m, 27H, P(CH3)3). 13C{IH} NMR: (CDCI3, 256 K): 8261.1 (t,J(WC) = 175.9, 2 J ( p C ) = I I . 4 Hz, CPh), 230.8 (dt, J(WC)=159.8, 2J(PCtrans) = 35.6, 2j(PCcis) = 6.2 Hz, CO), 153.3 (i-Ph), 127.5, 126.0, 123.5 (Ph), 44.8 (d, 3,/(PC) = 10.7 Hz, SCH), 40.9, 27.6, 25.7 (SCHCsH~o), 21.7 (virtual t, 14.4 Hz, 2P(CH3)3), 21.1 (d, J ( P C ) = 2 2 . 9 Hz, P(CH3)3). Anal. Calc. for C23H43OP3SW (MW 644.42): C, 42.87; H, 6.73. Found: C, 42.59; H, 6.70%.
2.1.6. [Et4NIIW(~CPh)(NC4H4)2(CO)(PMej)zI(3a) An oil dispersion containing 80% sodium hydride (0.057 g, 2.37 mmol) is washed with hexane ( 3 × l0 ml). The sodium hydride is suspended in 20 ml of THF and 0.048 g of pyrrole (0.72 retool) is added. The solution is refluxed for 20 min and then cooled to r.t. The filtered solution is transferred into a 50 ml flask containing a solution of 1 (0.062 g, 0.11 mmol) in 15 ml THF. The mixture is stirred for 16.5 h. After addition of excess Et4NCI (0.206 g, 1.24 mmol) the solvent is removed under vacuum. The product is extracted with THF and recrystallized from THF/hexane to give a small amount of the product. IR (THF): 1832 (s, CO ) em - 1. 2.1.7. [Et4N]IW(=CPh)(NC6Hs)2(CO)(PMe3)z] (3b) An oil dispersion containing 80% sodium hydride (0.048 g, 1.99 mmoi) is washed with hexane ( 3 x 10 ml). The sodium hydride is suspended in 20 ml THF and 0.094 g of indole (0.80 mmol) is added. After refluxing for 20 rain and cooling to r.t., the colorless solution is transferred into a 50 ml flask containing a solution of I (0.213 g, 0.38 retool) in 15 ml THF. After stirring for 14 h, excess Et4NCI (0.086 g, 0.52 mmol, pre-dried at 100°C under vacuum) is added. The solvent is removed under vacuum. The product is extracted with THF and recrystallized from THF/hexane to give tiny red crystals (0.163 g, 53%). IR (THF): 1835 (s, CO) c m - i. tH NMR (acetone-dt): 8 8A2--6.13 (m, 17H, Ph, NCsHt), 3.42 (q, J--7.3 Hz, 8H, NCH2CH3), 1.33 (t, Jffi7.3 Hz, 12H, NCH2CH3), 1.11 ( v ~ , a l t, 3.3 Hz, 18H, PMe3). 3~p NMR (acetone-d~): 8 - 8.95 (J(WP) ffi280.7 Hz, PMe3). Anal. Calc. for C3sHssN3OP2W (MW 815.68): C, 55.96; H, 6.80. Found: C, 55.75; H, 6.75%. 2.1.8. W(--CPh)(NC¢Hj-CHNMe-2)(CO)(PMe~)~ (4) Excess sodium (0.054 rag, 2.35 mmol) is added to a solution of pyrrolecarboxaldehyde-N-methylimine( 0.045 g, 0A2 mmol) in 20 ml hexane. After stirring for 8 h, the solvent is
133
removed under vacuum. The solid is taken up in 20 ml THF and filtered to remove unreacted sodium. "the solution is transferred into a 50 ml flask containing a solution of I (0.168 g, 0.30 retool) in 15 ml THF. After stirring for 10 h the solvent is removed under vacuum. The product is excxacted with hexane and recrystallized from the same solvent to give brown crystals (0.065 g, 51%). IR (THF): 1864 (s, CO) c m - L IH NMR (CDCI3): 8 8.03 (s, IH, CHNCH3), 7.197.15 (m, 5H, Ph), 6.83, 6.60, 6.17 (3H, C~-I~I), 3.90 (s, 3H, NCH3), 1.22 (virtual t, 3.3 Hz, 18H, 2PMe3). z3C NMR (CDCi3): 8 268.8 (t, J ( P C ) = 10.2 Hz, CPh), 244.3 (t, J(PC) =5.8 Hz, CO), 157.3, 153.3, 142.2, 137.3, 125.5 (2C), 124.0,113.8,112. i (CsH4N2, Ph), 51.7 (NCH3), 17A (virtual t, 11.6 Hz, PMe3). 31p NMR (CDCI3): 8 - 1 5 . 2 ( J(WP) = 281.0 Hz, PMe3). Anal. Calc. for ~ 3 o N e O P e W (MW 560.27): C, 42.88; H, 5.40. Found: C, 42.69; H, 5.43%.
2.1.9. Reaction of W(=CPh)(SCMejXCOXPMej)3(2d)with carbon monoxide A small amount of complex 2d is dissolved in "D-IF and placed under 1 arm of c~bon monoxide. After 12 h, the IR spectrum of the solution shows only two peaks at 1983 and 1912 c m - i . These absorptions indicate the presence of c/sW(-CPh)(SCMe3)(CO)(PMe3)2 (6). The solvent is removed under vacuum, and the residue is redissolved in CDCI3 to reco~'d the tH NMR spectrum. The spectrum is identical with that of the sample of 6 obtained by reaction of cis-W(-CPh) (Ci) (CO) 2(PMe3)2 with NaSCMe3. 2.1.10. Reaction of cis-W(~CPhXCI)(CO)2(PMe3)z with NaSCMej to give cis- W(-CPhXSCMe3X COXPMe3)z (6) Excess of sodium (0.060 g, 2.61 retool) is added to a solution of 50 pl of 2-methyl-2-propanethiol (0.040 g, 0.44 retool) in 20 ml of hexaue. After stirring for 8 h, the solvent is removed under vacuum. Then 15 ml TI-IF is added and the resulting solution is filtered to remove unreacted sodium. The solution is transferred into a 50 ml flask containing a solution ofcis-W(--CPh) (CI) (CO)2(PMe3)2 (0.062 g, 0.12 retool) in 15 ml THF. The mixture is stirred for 48 h. During this time, the color of the solution changes from yeh-w to orange and hhe carbonyl IR absorptions shift from 1999 and 1927 c m - i to 1983 and 1913 c m - L The solvent is removed ~mder vacuum. The product is extracted with hcxane and reorystallizcd from the same solvent to give a few milligramsof orange crystals. IR (THF): 1983 (s, CO), 1913 (s, CO) c m - L tH NMR (CDCI3): 8 7.23-7.18 (m, 5H, Ph), 1.66-1.63 (m, 18H, PMe3), 1.44 (s, 9H, CMe3). 2.1.11. Reaction of W(=-CPhXBrX COXPMes)3 (7) with carbon monoxide A small amount of complex 7 is dissolved in THF and placed under 1 arm of carbon monoxide. After 12 h, the IR spectrum of the solution shows three peaks at 2015,1929 and 1904 c m - L The peak at 1904 cm - t is due to unreacted starting material, the peaks at 2015 and 1929 c m - i indicate the presence of trans-W(--CPh) (Br) (CO)2(PMe3)2 (8).
134
A. Mayr. T.-Y. Lee/bwrganica ChimicaActa 252 (1996) 131-139
Table I Crystallographicdata for complexes2a and 2e
Formula Formulaweight a (.A) b (,A) c (p,) (°) /3 (°) y (o) v (A3) z Spacegroup Temperature Radiation(graphitemonochromator)(A) Linearabsorptioncoefficient(cm- t ) Scan mode 20 Range (°) Unique2eflectionswith IFo12>3oqFol2 Finalno. variables R'=E[IFol -F~I]IY-IFol R~= JEw( IFol - lEvi)"lEwFo 2] i/2 Standarderror observationunit weight
2a
2e
C21H36NOP3W 595.29 16.238(5) 9.487(3) 17.415(3) 90.0 100.80(2) 90.0 2635( I ) 4
C23H430[33s w
P2,1a
ambient Me Ka (A=0.71073) 46.661
644.43 ! 1.384(4) 9.265(3) 27.595(6) 90.0 90.0 90.0 2910(3) 4 P2,2,2, ambient Me Ka (A=0.71073) 42.964
0120
0120
0<20<60.8 4690 229 0.042 0.048 1.714
2.2<20<60.8 3115 262 0.029 0.029 1.086
~Quantityminimized(Y2w(IFol - IFcl)2); weightw= 1/(o'2 + 0.0016Fo2). The solvent is removed under vacuum, and the residue is redissolved in CDCI3 to record the ~H NMR spectrum. The tH NMR spectrum shows that 7 and 8 are present in a 60:40 ratio. Complex 8 was independently prepared by photoisomerization of c i s - W (=-CPh) (Br) (CO) 2(PMe3) 2.
of the P (3) Me3 ligand are disordered. The three carbon atoms C(19), C(20) and C(21 ) were kept isotropic, because when placed anisotropically, their temperature factors became too large. Selected crystallographic data for complexes 2a and 2e are listed in Table 1.
2.1.12. trans-W(=--CPh)(Br)(CO)z(PMe3)z (8) A solution of cis-W(-=CPh) (Br) (CO)2(PMe3) 2 (0.052
3. Results and discussion
g, 0.09 mmol) in 20 ml CH2C12 is irradiated with a 300 W projection lamp at 0°C for 80 min. Completion of the reaction is monitored by IR. During this time, the carbonyl IR bands shift from 2003 and 1930 c m - t to 2021 and 1930 c m - ~. The solvent is removed under vacuum and the product is recrystallized from diethyl ether to give orange-yellow crystals (0.041 g, 79%). IR (THF): 2016 (w, CO), 1929 (s, CO) era-". ~H NMR (CDCI3): 6 7.18-7.09 (m, 5H, Ph), 1.73 (virtual t, 3.7 Hz, 18H, PMe3). t3C NMR (CDCI3): ~ 269.2 (t, J(PC) = 10.2 Hz, CPh), 209.4 (t, J(PC) = 6.8 Hz, CO), 149.6 (i-Ph), 127.7, 127.5, 126.4 (CPh), 20.6 (virtual t, 13.7 Hz, PMe3). 3tp NMR (CDCI3): 6 - 2 7 . 5 (J(WP) = 274.5 Hz, PMe3). 2.2. Crytallographic studies
The general procedures for unit cell determination, data collection and structure solution have been previously described in detail [ 13]. All intensity measurements were made on an Enraf-Nonius CAD4A automated diffractometer, using a variable-rate, o.~--20 scan technique. Empirical absorption corrections (DIFABS) were applied. All calculations were performed using the TEXRAY programs. The structures were solved by direct methods and difference Fourier methods. In the structure of complex 2a, the three methyl groups
Reaction of [W(CPh)CI(CO)(PMe3)3] (1), with NaNC4H4, NaNCaH6, NaOC6Hs and NaSR (R--CMe3, C6H~I) in THF affords the alkylidyne tungsten complexes 2a--e containing pyrrolide, indolide, phenoxide and alkylsulfide ligands, respectively (Eq. ( 1) ). The products are recrystallized from hexane. In all complexes (2a-e) the anionic Ir donor ligand is occupying the coordination site trans to the alkylidyne ligand. This arrangement of the ligands is evident from the ~3C NMR data. The signal for the alkylidyne carbon atom in all of these compounds appears as a pseudo-quartet due to approximately equal couplings between the alkylidyne carbon atom and the three phosphorus atoms, while the signal of the carbonyl carbon atom appears in each case as a doublet of triplets due to large trans and small cis couplings.
o 1
o 2a: 2b: 2c: 2d: 2e:
~- ~-4~ ~ - NCsHs ~ - OCd.Is 3o~. SO~ 3 XR- SCsHi1
(1)
A. Mayr, T.-Y.
Lee/InorganicaChimica Acta 252 (1996)
The reaction of complex 1 with sodium pyrrolide and sodium indolide affords initially mixtures of the complexes 2a and 2b and the anionic complexes 3a and 3b (sodium salts), respectively, even when only equivalent amounts of the reagents are used. In these cases, the complexes 3a and 3b disappear after prolonged reaction times with concomitant complete formation of the complexes 2a and 2b. If, however, 2 equiv, of sodium pyrrolide and sodium indolide are added to 1, then complexes 3a and 3b form quantitatively as judged by IR (Eq. (2)). Complexes 3a and 3b were isolated as the tetraethylammonium salts, although 3a was not obtained in pure form due to its high reactivity. In the formation of 2e--e according to Eq. (1) no anionic intermediates of the type [W(CPh) (RX)2(CO)(PMe3)2] - could be detected by IR spectroscopy. Complex 4, a neutral analogue of compounds 3, was obtained by reaction of 1 with the sodium salt of pyrrole-2-carboxaldehyde methylimine (Eq. (3)). This anionic chelate ligand has previously been employed in reactions with alkylidyne complexes of the type [W(CR)Cl(pyfidine)2(CO)2] ( R = M e , Ph) to afford the ketenyl complexes [W(RCCO) (NC4H3-CHNMe-2) 2(CO) ] - [ 14]. The synthesis of the related complex $ from 1 and sodium diethyldithiocarbamate has previously been reported [ 15]. Me~ .PId~j c,~c--~
./!
21 ~t4C!/01-~12 r
[../!
NEt, ~ . ' - - ~ c - - .
1
135
131-139
1864 cm- ~.The ' 3C NMR resonance of the alkylidynecarbon atom is also relatively insensitive towards the introduction of the ~r donor ligands in the t r a n s position. The signal for 1 is at 6 261, and the signals for complexes 2 and 4 range from 6 259-270. The molecular structures of complexes 2a and 2e were determined by X-ray crystallography and are shown in Figs. 1 and 2, respectively. The crystallographic data for both compounds are collected in Table 1. The final atomic positional parameters of 2a and 2e are listed in Tables 2 and 3, selected bond distances and bond angles in "Fables 4 and 5, respectively. The structural features of 2a and 2e are within the expected range. In both structures, the ~r donor ligands and the phenyl group of the alkylidyne ligand are nea,,y coplanar. This feature may indicate the presence of an extended ~" system involving the ~rdonor ligand, the metal-carbon triple bond, and the phenyl group. A coplanar arrangement of these groups is also found in the related complex $ [ 14]. The alkylidyne iigand in complex 2e is only slightly bent, not
)
o(1)
(2)
3a: ~ - L'~H4
3b: )~- NC~o
Iq~P
._~ N ~ W ~ . . . _ C ~ p
...,/!
w~ O
_/I--
h
(3)
~P
1
•
~
Fig. I. Molecularst~mctureof complex2a.
4
C_.e~.- S Iv~
)
0(1) C(14)
s
The replacement of the chloride ligand in complex 1 by the ~" donor ligands exerts only a small influence on the IR stretching frequency of the cart~3nyi lignnd, e.g. v(CO) o f l shifts from 1896 to 1888 c m - ' for 2a. On the other hand, the replacement of PMe3 by pyrrolide or indolide in the position t r a n s to the carbonyl ligand in 3a and 3b causes a significant shift of the carbonyl stretching frequency to lower energies. For example, the carbonyl stretching frequency of 3a is at 1832 c m - ' and even in the neutral complex 4 it is as low as
C(21)
Fig. 2. Molecular sU-acture of corn flex 2e.
136
A. Mayr, T.- K Lee/Inorganica Chimica Acre 252 (1996) 131-139
Table 2 Final atomiccoordinatesand B,~ valuesof complex2a Atom
x
w(I) P(l) P(2) P(3) O(1) N(I) C(I) C(2) C(3) C(4) C(5) C,6) C(7) C(8) C(9) C(10) C(ll) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21)
0.39937(I) 0.07701(3) 0.5181(1) -0.0669(2) 0.4981(I) 0.1849(2) 0.2907(1) 0.0111(3) 0.2611(4) 0.2451(7) 0.4221(4) 0.2601(7) 0.3659(4) -0.0601(6) 0.3263(4) -0.1525(7) 0.2606(5) -0.1039(8) 0,2220(6) -0.190(1) 0.2474(7) -0.324(1) 0.3098(8) -0.377(1) 0.3511(6) -0.291(1) 0.3132(5) 0.1877(8) 0.5390(6) -0.226(1) 0.5078(6) -0,140(1) 0.6211(5) 0.012(I) 0.4683(7) 0.265(1) 0.460(1) 0.395(2) 0.409(1) 0.472(I) 0.3846(7) 0.386(I) 0.5537(7) 0.341(1) 0.5819(8) 0.085(1) 0.4469(7) 0.242(2) 0.247(1) -0.165(2) 0,309(1) 0.016(2) 0.206(1) 0.138(3)
y
z
Table 4 Selectedbond distances (A) and bond angles (°) for complex2a B~q
0.74316(2) 3.87(1) 0.7012(I) 4.90(8) 0.8541(I) 5.01(8) 0.6277(1) 6.2(I) 0,8052(4) 9.6(4) 0.6688(4) 6.3(3) 0.8036(4) 4.2(3) 0.8525(4) 4.5(3) 0.8868(5) 5.7(4) 0.9334(5) 7.2(5) 0.9476(6) 8.0(6) 0.9151(7) 9.6(6) 0.8676(6) 8.6(5) 0.7804(5) 5.9(4) 0.7571(6) 8.6(5) 0.6030(5) 8.2(5) 0.7080(7) 9.6(6) 0 . 6 1 2 4 ( 7 ) 10.6(7) 0,578(1) 15(I) 0.611(1) 11.3(8) 0.6666(6) 9.1(6) 0 . 8 3 4 7 ( 6 ) 10.8(7) 0 . 9 0 7 6 ( 6 ) 11.4(7) 0 . 9 3 3 2 ( 6 ) 13.0(8) 0.627(1) 16.3(5) 0.528(1) 16.6(5) 0.602(1) 22.1(8)
Table 3 Final atomiccoordinatesand B~ valuesof complex2e Atom
x
y
z
B~4
W(l) P(I) P(2) P(3) O(!) N(I) C(i) C(2) C(3) C(4) C(5) C16) C(7) C(8) C(9) C(IO) C(II) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(2~) C(21)
0.39937(1) 0.5181(1) 0.4981(1) 0.2907(!) 0.2611(4) 0.4221(4) 0.3659(4) 0.3263(4) 0.2606(5) 0.2220(6) 0.2474(7) 0.3098(8) 0.3511(6) 0.3132(5) 0.5390(6) 0.5078(6) 0.6211(5) 0.4683(7) 0.460(!) 0.409(!) 0.3846(7) 0.5537(7) 0.5819(8) 0.4469(7) 0.247(1) 0.309(I) 0.206(1)
0.07701(3) -0.0669(2) 0.1849(2) 0.0111(3) 0.2451(7) 0.2601(7) -0.0601(6) -0.1525(7) -0.1039(8) -0.190(1) -0.324(1) -0.377(i) -0.291(!) 0.1877(8) -0.226(1) -0.140(I) 0.012(I) 0.265(!) 0.395(2) 0.472(!) 0.386(I) 0.341(I) 0.085(!) 0.242(2) -0.165(2) 0.016(2) 0,138(3)
0.74316(2) 0.7012(1) 0.8541(!) 0.6277(i) 0.8052(4) 0.6688(4) 0.8036(4) 0.8525(4) 0.8868(5) 0.9334(5) 0.9476(6) 0.9151(7) 0.8676(6) 0.7804(5) 0.7571(6) 0.6030(5) 0.7080(7) 0.6124(7) 0.578(!) 0.611(1) 0.6666(6) 0.8347(6) 0.9076(6) 0.9332(6) 0.627(1) 0.528(1) 0.602(I)
3.87(1) 4.90(8) 5.01(8) 6.2(!) 9.6(4) 6.3(3) 4.2(3) 4.5(3) 5.7(4) 7.2(5) 8.0(6) 9.6(6) 8.6(5) 5.9(4) 8.6(5) 8.2(5) 9.6(6) 1&6(7) 15(1) !!.3(8) 9.1(6) 15.8(7) 11.4(7) 13.0(8) 16.3(5) 16.6(5) 22.1(8)
Bond distances
W(I)-P(I) W(I)-P(2) W(I)-P(3) W(I)-N(I) W( I )-(2( I ) W( I )~C(8) P( I )-C(9) P(I)-C(10) P(1)-C(II) P(2)-C(16) P(2)-C(17) P(2)-C(18) P(3)-C(19) P(3)--C(20)
2.576(2) 2.488(2) 2.493(2) 2.238(6) 1.819(6) 1.954(8) 1.794(9) 1.825(9) 1.818(8) 1.80( I ) 1.77(1) 1.818(9) 1.81(2) 1.81(2)
P(3)--C(21) O(I)--C(8) N(I)-C(12) N( I)--C(15) C( I )--C(2) C(2)-C(3) C(2)-C(7) C(3)--C(4) C(4)-C(5) C(5)-C(6) C(6)-C(7) C(12)-C(13) C(13)-C(14) C(14)-C(CI5)
1.82(2) 1.157(8) 1.34(1) i.34(!) 1.454(9) 1.40( I ) 1.38( I ) 1.38(i) 1.35(I) 1.35( 1) 1.41(I) !.36(2) 1.31(2) 1.38(2)
91.75(6) 95.32(7) 91.9(2) 96.0(2) 176.9(2) 170.06(7) 88.7(2) 93.7(2) 85.3(2) 84.1(2) 92,5(2) 87.7(2) 171.6(3) 88.9(3) 83.3(3) !11.6(3) 121.7(3)
W(I)-P(I)-C(I I) W(I)-P(2)-C(16) W(I)-P(2)-C(17) W(I)-P(2)-C(18) W(I)-P(3)-C(19) W(I)-P(3)-C(20) W(I)-P(3)-C(21) W(1)-N(I)-C(12) W( 1)-N( i)-C(15) C(12)-N(1)-C(15) W( I)-C( I )--C(2) W(I)-C(8)-O(I) N(I)-C(12)-C(13) N( I)-C(15)-C(14) C(12)-C(13)--C(14) C(13)-C(14)--C(15)
il9.4(4) !17.8(4) 120.5(4) 113.0(4) !16.7(5) 122.9(6) !15.1(7) 128.9(7) 125.8(7) 104.9(8) 169.5(5) 175.3(7) 109(I) I11(1) ll0(l) 105(i)
Bond angles
P(I)-W(I)-P(2) P(I)-W(I)-P(3) P(I)-W(I)-N(I) P(I)-W(I)-C(I) P(I)-W(I)-C(8) P(2)-W(I)-P(3) P(2)-W(I)-N(I) P(2)-W(I)-C(I) P(2)-W(I )-C(8) P(3)-W(I)-N(I) P(3)-W(I)-C(I) P(3)-W(i)-C(8) N(I)-W(I)-C(I) N(I)-W(I)-C(8) C(I)-W(I)-C(8) W(I )-P(I)-C(9) W(I)-P(I)-C(10)
more than in many other alkylidyne complexes. In complex 2a, however, the a!kylidyne ligand is nat only bent by about 10°, but also pushed towards the carbonyl ligand. The C( 1) W ( 1 ) - C ( 8 ) angle is only 83.3(3) °. This feature is apparently a consequence of steric interactions of the coplanar pyrrolide and phenyl groups with the central trimethylphosphine ligand. This situation is clearly visible in Fig. 3. The shortest interligand distance between the phenyl group and the trimethylphospine ligand in 2a, C ( 7 ) - C ( 9 ) is about 4.0 ,~, which is the same as the corresponding C( 13)-C(17) distance in 2e. In contrast to 2e, however, where the P(2)Me3 ligand can relax towards the sterically little demanding S( 1 ) atom, the P( 1)Me3 ligand in 2a cannot move away from the alkylidyne ligand because of the presence of the coplanar pyrrolide ligand. There are correspondingly short distances between C(12) on the pyrrolide ligand and the carbon atoms C(10) and C ( I I ) on the central PMe3 ligand of about 3.9 and 3.6 ,~, respectively. Consequently, the bending of the alkylidyne ligand in 2a and its shift towards the carbonyl ligand result from sterie interactions and are not due to an intrinsic electronic influence of the 1r donor ligand. Nevertheless, the coplanar arrangement of the pyrrolide and phenyl groups, which is ultimately responsible for these steric repulsions, may be the stabilized by ~r conjugation through the
137
A. Mayr, 7".-Y.Lee I Inorganica Chimica Acta 252 (1996) 131-139
Table5 Selectedbonddistances(,~) andbondangles(o) for complex2e Bonddismnces
W(I)-S(I) W(I)-P(I) W(I)-P(2) W(I)-P(3) W(I)-C(7) W(I)~(23) S(I)-C(I) P(I)-C(14) P(I)-C(15)
2.576(2) 2.482(2) 2.533(2) 2.480(3) 1.817(7) 1.979(8) 1.836(8) 1.802(9) 1.816(8)
P(I)-C(16) P(2)-C(17) P(2)~C(18) P(2)-C(19) P(3)-C(20) P(3)-C(21) P(3)-C(22) O(1)-C(23)
1.833(8) 1.80(I) 1.834(9) 1.82(I) 1.83(I) 1.79(I) !.80(I) 1.151(9)
93.63(7) 79.81(7) 92.36(8) 178.3(2) 90.2(2) 92.32(8) 172.08(7) 87.8(2) 87.8(2) 93.83(8) 101.1(2) 170.0(2) 86.2(2) 87.0(2)
C(7)-W(1)-C23 W(I)-S(1)-C(I) W(I)-P(i)-C(14) W(I)-P(I)-C(15) W(I)-P(I)-C(16) W(I)-P(2)-C(17) W(I)-P(2)-C(18) W(I)-P(2)--CI9 W(I)-P(3)-C(20) W(I)-P(3)-C(21) W(i)-P(3)-C(22) S(I)-C(I)~C(2) S(I)-C(I)-C(6) W(I)-C(7)-C(8)
88.9(3) 112.2(2) 112.9(3) 117.5(3) i19.7(3) 115,1(3) !i7,2(3) 117.0(3) 118.4(4) !11.6(5) 121.1(4) !10.8(6) i11.6(6) 175.6(6)
Bondang~s
S(I)-W(I)-P(I) S(I)-W(I)-P(2) S(I)-W(I)-P(3) S(I)-W(I)-C(7) S(i)-W(I)-C23 P(i)-W(I)-P(2) P(I)-W(I)-P(3) P(I)-W(I)--C(7) P(I)-W(i)-C23 P(2)-W(I)-P(3) P(2)-W(I)-C(7) P(2)-W(I)-C23 P(3)-W(I)-C(7) P(3)-W(I)-C23
metal-carbon triple bond. The methylidyne ligand in [ W (=-C-H) (n-butyl) ( Me2PCH2CH2PMe2) 2] was found to be bent by about 18° [ 16]. In this case, the bendin~ may be induced or facilitated by the presence of the trans n-butyl ligand, which is a very strong donor, although primarily a 6-
donor. Probably as a result of the steric interactions,the bond distance between tungsten and the central trimethylphosphine ligand is distinctly longer in 2a, W( l ) - P ( 1 ) -- 2.576(2) ,A, than in 2e, W ( I ) - P ( 2 ) =2.533(2) ,~. This feature is consistent with the observed facile substitution of one PMe3 ligand in 2a and 2b to give the anionic complexes 3. As a preliminary test of the reactivity of the new ~rdonor ligand-substituted alkylidyne tungsten complexes, a solution of compound 2d was exposed to one atmosphere of carbon monoxide (Eq. (4)). After 12 h, the IR spectrum of the solution showed two strong absorptions of similar intensity at 1983 and 1912 cm- t. This pattern is characteristic of a cis-dicarbonyl system. The identity of the product as cis[W(CPh)(SCMe3)(CO)2(PMe3)2] (6), was confirmed by the synthesis of the same compound from c/s[W(CPh)(SCMe3)(CO)2(PMe3)2] (6), was confirmed by the synthesis of the same compound from cis[W(CPh)CI(CO)2(PMe3)2] and NaSCMe3. The reactivity
u~cs-- =
c(7)
(a)
c(.)
c~) c(lo)
(1:)
Fig. 3. View of the complexes 211 (a) and 2e (b) showing the plane con-
rainingthe alkylidyneligand,the CO ligand,the ~"donorligandand one trimethyiphosphineiigand.The methylgroupsof the trimethylphosphine ligandsaboveandbelowthisplanehavebeenomittedfor clarity.
C.Ollatm
~ ~.~:s~*~c--~
2d
ue~i . . - ~
(4)
6
co/tarm tz,
o 7
c(12)
~
~:Y~
(5~
~ / o 8
of 2d towards carbon monoxide differs from that of the analogous brmno complex [W(CPh)Br(CO)(PMe3)3] (7). When a THF solution of 7 is placed under one atmosphere of carbon monoxide, an equilibrium mixture of 7 and trans[ W(CPh)Br(CO)a(PMe3) 2] (8), in a relative ratio of 60:.40 is obtained (Eq. (5)). The formation oftbe trans complex 8 is as expected. The substitution of the central uimethylphosphine ligand in complexes of the type [W(CPh)X(CO)(PMe3) 3] ( X = halogen) is a proven method for the synthesis of tungsten alkylidyne complexes of the general type trans- [W(CPh)X(CO) (L) (PMe3)2] [ 17]. The complete conversion of complex 2d upon reaction with carbon monoxide under I atm can be attributed to the increasedelectronrichness of the system, compared to complex 7, but the formation of the c/s complex 6 represents a qualitative difference in reactivity between the thiolato- and bromo-substituted alkylidynetungsten complexes 2d and 7. In the reaction of 2d with carbon monoxide, no :~'kylidyne-carbonyl conpiing product, i.e. a ketenyl tungsten complex [ 18], was observed. In contrast, complex 5 easily takes up carbon monoxide to afford the ketenyl tungsten complex [W(PhCCO) (S2CNEt2) (CO) (PMe3)2] [ 15].
138
A. Mayr, Z- Y. Lee/Inorganica Chimica Acta 252 (1996) 131-139
Several low-valent aikylidyne metal complexes which are of interest in the current context have been reported in the literature. Fischer and co-workers prepared complex 9 containing a diphenylarsenido ligand [ 19]. Hopkins and coworkers recently described a family of acetylide-substituted tungsten alkylidyne complexes (10) [20]. As indicated by the electronic spectra of these compounds, there is significant ~-conjugation between the M = C and C---C systems. Attempts in our laboratory to synthesize alkylidyne complexes containing alkyne ligands of the type of complex 11 resulted in the isolation of the alkylidene alkyne tungsten complex (12) [ 21 ]. Alkylidyne alkyne complexes of the type of complex 11 are presumably intermediates in the formation of complex 12, but due to 7r donation by the alkyne ligand, the alkylidyne carbon atom is quite basic and easily picks up a proton [22]. Thermally labile alkylidyne alkyne tungsten complexes of the type of complex 13 were successfully characterized by Mayer and co-workers [ 23 ].
5. Supplementary material Further details of the crystal structure investigations of complexes 2a and 2e may be obtained from the authors upon request.
Acknowledgements Support for this work by the Donors of the Petroleum Research Fund, administered by the American Chemical Society, and by the National Science Foundation is gratefully acknowledged. We thank Michael P. Rickenbach and Professor Stephen A. Koch for the X-ray crystallographic studies and Michael A. Kjelsberg and On Ki Cheung for preliminary experimental work.
Mez?'7 I .~e2 References
/Ph
/eh
/
IZn~C [ ..~e3 ~
M~/!, ,z"
"~'/~ ,t oC/! o
oC/! 14
0
"J"~°',3
15
Schrock and Williams have recently reported the synthesis of several low-valent alkylidyne rhenium complexes containing aryloxide and alkoxide ligands [24]. "lae existence of the electronically unsaturated species 14 and 15 is without doubt a consequence of the stabilization of the metal center by the ~r donor ligands.
4. Conclusions The synthesis of tungsten alkylidyne complexes of the Fischer-type containing pyrrolide, indolide, phenoxide and aikylsulfide ligands has been demonstrated. The presence of the ~r donor ligands leads to an increase of the electronrichness of the metal-alkylidyne system. In reactions with the ~acid carbon monoxide, these 1rdonor ligand-substituted systems exhibit an increase in reactivity compared to the corresponding halo-substituted Fischer-type alkylidyne complexes.
[ I ] E.O.Fischer,Angew. Chem., 86 ( 1974) 651;Adv. Organomet. Chem., 14 ( 19761 1. [2l R.R. Schrock,Ace. Chem. Res., 19 ( 19861 342. [3] (a) H. Fischer, P. Hofmann,F.R. Kreissl, R.R. Schrock, U. Schubert and K Weiss, Carbyne Complexes, VCH, Weinheim, 1988; (b) H.P. Kim and R.J. Angelici,Adv. Organomet. Chem., 27 (1987) 51; (c) M.A. Gallop and W.R. Roper, Adv. Organomet. Chem., 25 (1986) 121; (d) F.G.A. Stone,Adv. Organomet. Chem., 31 (1991) 53; (e) A. Mayrand H. Hoffmeister,Adv. Organomet. Chem., 32 (19911 227; (f) A. Mayrand C.M. Bastos, Prog. Inorg. Chem, 40 ( 19921 l. 14l (a) N.M. Kosti~ and R.F. Fenske, Organometallics, I (1982) 489; (b) P. Hofmann,Carbyne Complexes, VCH,Weinheim, 1988. [ 5] A. Mayr, Transition Metal Carbyne Complexes, NATO AS! Set. (7,392 (1993) 219. [6l P.F. Engel and M. Pfeffer,Chem. Rev., 95 ( 19951 2281. [7] (a) H. Fischerand C. Troll, Chem. Bet., 126 (t993) 2373; (b) M.R. Terry, L.A. Mercando,C. Kelly,G.L. Geoffroy,P. Nombel,N. Lugan, R. Mathieu, R.L. Ostrander, B.E. Owens-Waltermire and A.L. Rbeingold, OrganometaUics, 13 (1994) 843. [ 8] M.D.Mortimer,J.D. Carterand L. McEIwee-White,Organometallics, 12 ( 19931 4493. [9] A. Mayf, M.F. Asaro, MA. Kjelsberg,K.S. Lee and D. Van Engen, Organometallics, 6 (1987) 432. [ 10l P. Steil and A. Mayr, Z. Naturforsch., Teil B, 47 (1992) 656. [ ! i ] G.A. McDermott, AM. Domes and A. Mayr, OrganometaUics, 6 ( 19871 925. [12] B. Emmert, K. Diehl and F. Gollwitzer, Chem. Bet., 62 (1929) 1733. [ 13l S. Lincolnand S.A. Koch,lnorg. Chem., 25 (1986) 1594. [14l A. Mayr, G.A. McDermott, A.M. Dorries and D. Van Engen, Organometallics, 6 (19871 1503. [ 15l A. Mayr, R.T, Chang, T.-Y. Lee, O,K. Cheung,"M.A. Kjelsberg, G.A. McDermott and D. Van Engen, J. Organomet. Chem., 479 (1994) 47. [ 16] J. Manna, S.J. Geiband M.D. Hopkins,Angew. Chem., Int. Ed. Engl., 32 (1993) 858. [ 17] A. Mayr, T.-Y. Lee, M.A. Kjelsbergand K,S. Lee, Organometallics, 13 (1994) 2512.
A. Mayr, T.- Y. Lee / lnorganica Chimica Acta 252 (1996) 131-139 [18]F.R. Kreissl, in A. de Meijere and H. tom Dieck (eds.), Organometallics in Organic Synthesis, Springer, Berlin, 1987, p. 105. [ 19] A.C. Filippou, E.O. Fischer, K. Ofele and HG. Air, J. Organomet. Chem., 308 (1986) 1 I. [ 20 ] J. Manna, S 3. Geib and M.D. Hopkins, J. Am. Chem. Soc., 114 ( 1992 ) 9199.
139
[21] A. Mayr, K.S. Lee, MA. Kjelsberg and D. Van Engen, J. Am. Chem. Soc., 108 (1986) 6079 [22] A. Mayr, Comments inorg. Chem., i 0 (1990) 227. [23] L.M. Atagi, S.C. Critchlow and J.M. Mayer, J. Am. Chem. Soc., 114 (1992) 9223. [24] D.S. Williams and R.R. Schrock, Organometallics, 13 (1994) 2101.