Organometallics 1995,14,4294-4299
4294
Synthesis and Structures of Vanadium(I1) Alkynide Complexes: [(L~TMEDA)~V@-CECP~)~(TMEDA)] and V(CSR)2(TMEDA)2 (R = Ph, t B ~TMEDA ; = N,N,W,W-Tetramethylethylenediamine) Hiroyuki Kawaguchi and Kazuyuki Tatsumi" Department of Chemistry, Faculty of Science, Nagoya University, Furo-cho Chikusa-ku, Nagoya 464-01, Japan Received March 28, 1995@ The V(I1) tetrakis- and bis(a1kynide) complexes, [(LiTMEDA)2V+-C=CPh)4(TMEDA)] (1) and V ( C G C P ~ ) ~ ( T M E D(2) A ) have ~ been synthesized from the reaction between VCl3(THF)3 and LiCECPh in THF in the presence of TMEDA (=N,N,N',N'-tetramethylethylenediamine). In the case of the analogous VC13(THF)3/LiC=CtBW"MEDAreaction system, only the bis(alkynide) complex V(C=CtBu)2 (TMEDAh (3)was isolable. Reduction of vanadium occurred during these reactions, and use of a divalent vanadium chloride, VCMTMEDA12, instead of VC13(THF)3was found to give 1-3 in higher yields. Complex 1 crystallizes in the monoclinic space group P21/c with 2 = 4 in a unit cell of dimensions a = 15.761(4)A, b = 14.325(4) A, c = 22.614(9) A, and 8, = 98.38(4)". Crystals of 2 are orthorhombic, space group C m c m , with a = 10.045(5)A, b = 22.379(7) A, c = 12.306(4)A, and 2 = 4. Crystals of 3 are triclinic, space group P1, with a = 9.402(2) A, b = 9.833(2) A, c = 8.907(2) A, and 2 = 1. Reactions of these alkynide complexes with electrophiles such a s MesSiCl, MeI, PhNCO, C02, and CO were examined. While alkynide complexes are ubiquitous in organometallic chemistry,' those of group 4 and 5 transition metals are still scarce, and the only structurally characterized examples are limited to those consisting of bent-metallocene fragment^.^-^ This is probably due to a lack of steric bulk of alkynide ligands that may allow high reactivity at these electron-deficient metal ~ e n t e r s . ~ We are interested in developing chemistry based on "alkynide rich" complexes of early transition metals and report herein the synthesis and structures of vanadium(11) complexes that carry two or four alkynides at a single metal center: [(LiTMEDA)zV(pu-C=CPh)4(TMEDA)] (11, V(CWPh)2(TMEDA)2 (21, and V(C= CtBu)2(TMEDA)2 (3). The only previously reported tetrakidalkynide) mononuclear complexes are LiLn(CWR)4(THF)(Ln = Sm, Er, Lu; R = tBu, Ph16 These have been shown to form from the reaction of homoleptic alkyl lanthanide complexes with monosubstituted alkynes, but no structural information is yet available. A related lanthanide alkynide is [(C5Me&Ybl2[(pC=CPh)dYb], which has four bridging alkynides.' Complexes 1-3 were synthesized from the reaction between VC13(THF)3 and lithium salts of the corre@Abstractpublished in Advance ACS Abstracts, July 15, 1995. (1)Nast, R. Coord. Chem. Reu. 1982,47, 89-124. (2)(a) Erker, G.; Fromberg, W.; Benn, R.; Mynott, R.; Angermund, K.; Kriiger, C. Organometallics 1989, 8, 991-920. (b) Lang, H.; Seyferth, D. 2. Nuturforsch. 1990,212, 45B. (3)Teuben, J. H.; DeLiefde Meijer, H. J. J . Orgunomet. Chem. 1968, 1.5.> 131-137. _. ---
(4)Evans, W. J.; Bloom, I.; Doedens, R. J . J . Organomet. Chem. 1984,265, 249-255. (5) (a)Heeres, H. J.; Teuben, J. H. Organometallics 1991, IO, 19801986. (b) Sekutowski, D. G.; Stucky, G. D. J. Am. Chem. Soc. 1976, 98, 1376-1382. (c) Evans, W. J.; Keyer, R. A,; Ziller, J. W. Orgunometallics 1993, 12, 2618-2633 and references therein. (6)Evans, W. J.;Wayda, A. L. J . Organomet. Chem. 1980,202, C6C8. (7) Boncella, J. M.; Tilley, T. D.; Andersen, R. A. J . Chem. SOC., Chem. Commun. 1984, 710-712.
sponding alkynides, in which the vanadium atom was reduced from V'II to VI1. We also found that the prereduced V(I1) chloride, VC12(TMEDA)2,8reacted with these lithium alkynides to give 1-3 in higher yields. The organometallic chemistry of vanadium(I1) is little explored, and is mostly based on half-sandwich-type cyclopentadienyl c o m p l e ~ e s .We ~ plan to utilize these alkynide V(I1) compounds as an entry into such chemistry, and thus we also report some initial results of reactions of 2 and 3 with Me3SiC1, MeI, PhNCO, C02, and CO.
Results and Discussion Synthesis of Vanadium(I1)Alkynides. Treatment of VC13(THF)3with 5 equiv of LiCsCPh in THFPTMEDA at 0 "C formed a brown solution, and a gradual color change to purple was observed upon warming the solution to room temperature. Removal of the solvent followed by recrystallization of the resulting solid from hexanePTMEDA generated 1 as purple crystals (see eqs 1 and 2). When the amount of LiCWPh was decreased VC13(THF)3 + n LiCiCPh
RMEDA
[(LiTMEDA)2V(pC=CPh)4(TMEDA)] 1 eq (1) : 64% yield eq (2) : 4%
1
(1 1
1+2
(2)
V(CICP~)~(TMEDA)~ 2 eq (2) : 71%
to 3 equiv, 2 was obtained as brown crystals, together with a small amount of 1. In all cases, the vanadium ( 8 ) Edema, J. J. H.; Gambarotta, S.; Stauthamer, W.; van Bolhuis, F.; Spek, A. L.; Smeets, W. J. Inorg. Chem. 1990, 29, 1302-1306.
0 1995 American Chemical Society
Organometallics, Vol. 14, No. 9, 1995 4295
Vanadium(II) Alkynide Complexes
Table 1. Crystal Data for [(LiTMEDAhV@-CiCPh)d(TMEDA)](l), V(CWPh)2(TMEDA)z(2), and V(C+YBu)z(TMEDA)2 (3) 1
formula
fw space group a,A b, A c,
A
a, deg
R, deg. Y , deg
v, A3
z
Dcaled,
ORTEP drawing of the structure of [(LiTMEDA)zV@-CzCPh)4(TMEDA)] (1).
Figure 1.
center is reduced from V(II1)to V(II), where the reducing agent is probably LiC=CPh, thus consuming 1equiv of LiCECPh during the reaction. Since 1 is soluble in hexane and other typical organic solvents, the lithium cations are probably tightly bound to the alkynides in solution. Interestingly the lithium-free neutral alkynide complex 2 is not very soluble in nonpolar organic solvents. The tetrakisalkynide complex 1 was also synthesized in 84% yield from the reaction between the prereduced V(I1) chloride VC12(TMEDA)2and 4 equiv of LiCECPh under similar reaction conditions. Likewise, the (1:2) VC12(TMEDA)fiiC=CPh reaction system gave rise to 2 in 85% yield in addition to a small amount of 1. Although this method starting from VC12(TMEDA)2 gives the alkynide complexes of V(I1) more cleanly and in higher yields, we have found it more convenient to use VCl3(THF)3because of the additional steps required in the synthesis of VClz(TMEDA12. Addition of 3 equiv of LiCWtBu to a THF/TMEDA solution of VC13(THF)3 afforded 3 as brown-purple crystals (eq 3).1° However, the reaction between 5 equiv VCIs(THF)s
+
3 LiC=C'Bu THF/TMEDA
* V ( C ~ B U ) ~ ( T M E D(3) A)~ 3 56% yield
of LiCECtBu and VCl3(THF)3resulted in an uncharacterized green product along with 3 (11%)as a side product, and our attempts to isolate the CNYBu analogue of 1 have not been successful. The lH NMR spectra of 1-3 are not informative due to the paramagnetic nature of these V(I1) compounds. The E1 mass spectra of 2 and 3 consist of the parent (9) (a) Hessen, B.; Teuben, J. H.; Lemmen, T. H.; Huffman, J. C.; Caulton, K. G. Organometallics 1985, 4, 946-948. (b) Hessen, B.; Lemmen, T. H.; Luttikhedde, H. J. G.; Teuben, J. H.; Petersen, J. L.; Huffman, J. C.; Jagner, S.; Caulton, K. G. Organometallics 1987, 6, 2354-2362. (10)Use of VC12(TMEDA)2,instead of VCla(THF)3,again increased the yield of 3 to 73%.
g/Cm3
3
2
C ~ O H ~ ~ N ~CLZ ~ Z ~VZ N ~ VC Z ~ H ~ O N ~ V EH 485.61 445.629 817.95 P21/c (No. 14) Cmcm (No. 63) P1 (No. 2) 10.040(5) 9.402(2) 15.761(4) 14.325(4) 22.379(7) 9.833(2) 22.614(9) 12.306(4) 8.907(2) 108.61(2) 98.38(4) 110.58(2) 73.18(1) 715.9(3) 5051(3) 2761(2) 4 1 4 1.076 1.169 1.034 55.0 45.0 55.0 0.92- 1.OO 0.90-1.00 0.96-1.00
2 L , , +g transmissn factors 7032 1388 no. of unique reflns 865 no. of observnsD 3137 0.0688 0.0695 R 0.0641 0.0705 RW function Cw(tFol Cw(lFol minimized IFcI)' IFcl)' least-sauares 1.5565/(02(F)+ 0.3181/(02(F)+ WtS 0.0005F2) 0.002F2) no. of refined 301 141 params
3130 2573 0.0661 0.0688 X ~ ( l F o lIFcI)'
0.5929/(02(F)+ 0.004F2) 207
a Z > 3.0o(I).
molecular ion along with fragments resulting from loss of the alkynide group and/or TMEDA. On the other hand, the mass spectrum of the lithiated complex 1 did not provide us with useful information. The IR spectrum of 1 features a sharp band at 2000 cm-l and a weaker band a t 1964 cm-l, both assignable to CEC stretching vibrations. In the case of 2 and 3, a single C=C stretching band appears which is shifted t o higher frequency relative to that of 1: 2020 cm-' for 2 and 2035 cm-l for 3. These vcIc frequencies are lower than those of the V(II1) alkynide complexes, (C5H&V(C=CPh) (2060 cm-lI3 and (C5H5)2V(C=CtBu)(2075 cm-lh4 In the absence of TMEDA, neither the VC13(THF)3/ LiCECPh nor the VC13(THF)&iC=CtBu reaction system in THF gave characterizable products. Thus chelation by TMEDA of either V(I1) or Li appears to be important to stabilize these alkynide complexes. However, in DME, the reaction between VCls(THF13 and LiCECPh allowed us t o isolate a DME containing lithiated alkynide complex Liz(DMElxV(C=CPh)4(4) as red-purple crystals (eq 4). The coordination geometry VC13(THF)3 + 5 LiCICPh
DME
Li2(DME)xV(C&Ph)4
(4)
4
at V(I1) of 4 is thought to be similar to 1. In fact the C=C stretching bands for 4 appear at 2000 (s) and 1960 cm-' (w), which are very close to those of 1. Structure of [(LiTMEDA)zV(I(-C~Ph)4(TMEDA)I (1). The molecular structure of 1 is shown in Figure 1. A summary of crystal data, fractional coordinates, and selected bond distances and angles are given in Tables (11)(a) Krausse, J.; Man, G. J. Organomet. Chem. 1974,65, 215222. (b) Muller, E.; Krausse, J.; Schmiedeknecht, K. J. Organomet. Chem. 1972,44, 127-140. (12) Olmstead, M. M.; Power, P. P.; Shoner, S. C. Organometallics 1988, 7, 1380-1385.
4296 Organometallics, Vol. 14,No.9,1995
Kawaguchi and Tatsumi
Table 2. Positional Parameters and U(eq)Values (A2)for [(L~TMEDA)zV~-C~CP~)~(TMEDA)I (l), V(C-CPh),(TMEDA)Z (21, and V(C=CtBu)z(TMEDA)z(3) atom V N1 N2 N3 N4 N5 N6 Li 1 Li2
c1
c2 c3 c4 c5 C6 c7 C8 c9 c10 c11 c12 C13 C14 C15 C16 C17 C18 c19 c20 c21 V N
c1
c2 c3 c4 c5 C6 c7 C8
V N1 N2
c1
c2 c3 c4 c5 C6 c7 C8 c9 a
X
0.32221(7) 0.3956(4) 0.3423(4) 0.3926(4) 0.4980(4) 0.0680(6) 0.0272(6) 0.4051(8) 0.1447(7) 0.4488(4) 0.5227(5) 0.6102(5) 0.6511(5) 0.7353(6) 0.7819(6) 0.7432(6) 0.6586(5) 0.3056(4) 0.2933(4) 0.2776(5) 0.2942(5) 0.2808(7) 0.2477(7) 0.2313(7) 0.2442(6) 0.2035(4) 0.1464(5) 0.0869(6) 0.1011(7) 0.043(1) 0.00 0.1743(5) 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00
0.00 0.1945(5) -0.0990(5) 0.1221(3) 0.1938(3) 0.2857(3) 0.2772(5) 0.2193(5) 0.4536(4) 0.3484(6) 0.2129(6) 0.1282(7)
Y
0.22753(8) 0.2470(5) 0.0716(4) 0.3781(4) 0.4749(4) 0.3501(6) 0.1570(8) 0.3647(7) 0.2328(9) 0.2254(5) 0.2130(5) 0.1898(5) 0.2118(5) 0.1870(6) 0.1415(7) 0.1184(6) 0.1430(5) 0.3743(5) 0.4568(6) 0.5518(5)
0.5793(6) 0.6699(8) 0.7324(8) 0.7112(7) 0.6184(7) 0.2219(5) 0.2166(6) 0.2075(8) 0.1423(8) 0.135(1) 0.12755(5) 0.1264(2) 0.2249(4) 0.2788(1) 0.3435(4) 0.3756(3) 0.4376(4) 0.4676(5) 0.0303(4) -0.0233(4) 0.50 0.4633(5) 0.3424(5) 0.3104(3) 0.2049(3) 0.0761(4) -0.0624(4) 0.0545(5) 0.0880(5)
0.3901(7) 0.6007(6) 0.3849(6)
z
U(eq)
atom
X
c22 -0.023(1) 0.07117(5) 0.046 C23 -0.0360(8) -0.111(2) 0.051 0.0452(3) 0.070 C24 0.0165(6) 0.2454(2) C25 0.2653(4) 0.065 0.1712(3) 0.069 C26 0.2412(4) C27 0.2208(5) 0.1034(4) 0.105 0.0966(5) 0.127 C28 0.1990(5) C29 0.1799(6) 0.1539(5) 0.061 0.0913(5) 0.079 C30 0.1830(6) C31 0.2021(6) 0.1256(3) 0.051 0.1489(3) 0.054 C32 0.2232(5) 0.1699(3) 0.054 c33 0.3431(5) c34 0.4727(5) 0.2275(3) 0.073 0.4262(8) 0.2458(4) 0.086 c35 0.2079(5) 0.101 C36 0.3748(7) 0.1520(5) 0.093 c37 0.4014(5) 0.2625(5) C38 0.1330(3) 0.069 0.4224(5) 0.0750(3) 0.056 c39 0.3048(6) 0.0653(3) 0.059 C40 0.4477(6) 0.0462(4) 0.063 C41 -0.0091(4) 0.5216(6) 0.091 C42 -0.0293(4) 0.4624(6) 0.108 c43 0.0055(6) 0.5739(5) 0.112 c44 0.0604(6) 0.134 c45 0.0594(5) 0.0792(4) 0.1054(7) 0.114 C46 -0.015(1) 0.0087(3) 0.064 c47 -0.032(1) 0.072 C48 -0.0331(3) 0.0251(7) c49 -0.0873(4) 0.091 0.006(1) -0.1286(5) 0.132 C50 -0.1818(6) 0.206 V(CECPh)Z(TMEDA)2(2) 0.25 0.036 C9 0.00 0.1274(4) 0.072 C10 -0.1186(8) 0.25 0.053 C11 -0.1164(9) 0.25 0.044 C12 0.166(3) 0.25 0.047 C13 0.7819(6) 0.1522(8) 0.066 C14 0.201(2) 0.085 0.157(1) C15 0.296(2) 0.25 0.092 C13xa 0.202(2) 0.049 C14x 0.160(2) 0.25 0.25 0.048 C15x 0.287(2) V(C=CtBu)2(TMEDA)z(3) 0.048 C10 0.0117(7) 0.50 0.7340(6) 0.079 C11 -0.1220(6) 0.5718(5) 0.070 C12 -0.2461(6) 0.3541(3) 0.063 Nlxa 0.2191(6) 0.2780(3) 0.061 N2x 0.1429(5) 0.25(0) 0.047 C7x 0.3015(7) 0.2317(6) 0.131 C8x 0.1797(6) 0.0052(4) 0.131 C9x 0.3026(6) 0.2492(6) 0.148 ClOx 0.2796(6) 0.7155(7) 0.138 Cllx 0.0434(6) 0.8745(6) 0.120 C12x 0.1647(6) 0.8032(7) 0.172
Y
z
Ueq)
0.190(2) 0.253(2) 0.265(1) 0.1827(5) 0.1437(5) 0.0939(6) 0.1372(6) 0.0852(9) -0.009( 1) -0.0534(7) -0.0033(7) 0.2875(6) 0.3064(7) 0.1545(9) 0.0798(7) 0.0212(5) 0.0171(5) 0.2900(5) 0.3945(6) 0.4571(6) 0.4683(7) 0.5650(6) 0.4612(6) 0.4128(7) 0.3999(8) 0.314(1) 0.226(2) 0.111(1) 0.093(1)
-0.1944(7) -0.1542(5) -0.1021(4) 0.1461(3) 0.1896(3) 0.2403(4) 0.2901(4) 0.3376(4) 0.3380(5) 0.2888(5) 0.2408(4) -0.0639(3 0.0014(3) -0.0223(4) -0.0124(5) 0.0906(4) 0.0361(4) 0.2744(3) 0.2581(4) 0.2680(4) 0.2360(4) 0.1528(4) 0.1423(4) 0.0530(5) 0.1554(5) 0.1102(9) 0.092(1) 0.1493(7) 0.0509(8)
0.250 0.271 0.194 0.052 0.061 0.063 0.090 0.109
-0.0873(1) -0.1197(3) -0.1813(3) 0.180(1) 0.1415(7) 0.0745(7) 0.1440(6)
0.039 0.053 0.063 0.102
0.0722(9) 0.1079(6)
0.25 0.25 0.25 0.040(2) 0.2079(5) 0.075(1) 0.205(2) 0.075(2) 0.032(1) 0.195(2)
0.3075(7) 0.2036(5) 0.4107(6) 0.4918(5) 0.6426(5) 0.3282(6) 0.5401(6) 0.05858(7) 0.6275(7) 0.8039(5) 0.6017(6)
0.7119(7) 0.4473(6) 0.6163(6) 0.7365(6) 0.4748(5) 0.7308(6) 0.8888(6) 0.7193(7) 0.5959(2) 0.4692(6) 0.3017(5)
0.170 0.094 0.102 0.097 0.080 0.126 0.116 0.160 0.166 0.104
0.181(1)
0.115 0.106 0.082 0.087 0.119 0.146 0.141 0.110 0.109 0.083 0.124 0.105 0.122 0.123 0.117 0.149 0.174 0.203 0.268 0.279 0.379
0.101
0.084 0.102 0.085 0.110
0.095
0.110
Atoms designated with an x are disordered and were refined with half-occupancy.
1-3. Four phenyl acetylides and one TMEDA molecule are bound to the vanadium atom approximately in an octahedral array. There are two lithium cations, each bridging the a-carbons of a pair of cis-alkynide ligands. Each lithium is further coordinated by a TMEDA molecule, completing a tetrahedral coordination geometry. The distances between the lithiums and the P-carbons of the alkynides, ranging from 2.80(1)to 2.87(1) A, are too long to invoke bonding interactions. Electron deficient early-transition metal complexes often accommodate lithium cations which are tightly bound to anionic ligands,11J2and in the yttrium alkynide complex, (C5Me5)2Y(C=CtBu)2Li(THF),the lithium also coordinates to the a-carbons of the alkynides.13 The LiCa distances of 2.20(1)-2.23(1) A for 1 are comparable
to those of (C5Me5)2Y(C=CtBu)2Li(thf)(2.09(3)All3 and (PhC=CLiTMEDA)d (2.20(1) Despite the lithium coordination at the a-carbons, the V-C-C bond angles do not deviate much from linearity. The V-Li separations of 2.89(1) and 2.90(1) A are longer than the sum of the ionic radius of Li+ and V(II), 2.66 A.15 The average V-Li distance (2.615 A) in a related homoleptic phenyl complex [LiOEt214[VF'h~lis clearly shorter than that of 1.12 Thus direct bonding interactions, if any, between V(I1) and Li+ in 1 would be very small. The (13)Evans, W. J.; Drummond, D. K.; Hanusa, T. P.; Olofson, J. M.
J. Organomet. Chem. 1989,376,311-320.
(14) Schubert, B.; Weiss, E. Angew. Chem. Int. Ed. Engl. 1983,22, 496-497. (15) Shannon, R. D. Acta Crystallogr. 1976,A32,751-767.
Vanadium(II)Alkynide Complexes
Organometallics, Vol. 14, No. 9, 1995 4297
Table 3. Selected Bond Distances (A) and Angles (deg) for [(LiTMEDA)2VO(-C=CPh)4(TMEDAII (l), V(C=CPh),(TMEDA)2 (21, and V(C=CtBu)2(TMEDA)2 (3) I(LiTMEDA)oV(u-C4Ph).dTMEDA)l(l)
v-c1
v-c9 V-C17 V-C25 V-N1 V-N2 V-Lil V-Li2 Lil-N3 Lil-N4 Li2-N5 v-c1-c2 V-C9-C10 V-Cl7-Cl8 V-C25-C26 N3 -Lil -N4 C1-Lil -C9 N5 -Li2 -N6 C17-Li2-C25
v-c1 v-c7 V-N C1-V-N N-V-N
v-c1 V-N2
v-c1-c2 N1-V-N2
2.1866y 2.122(8) 2.175(6) 2.128(7) 2.346(6) 2.343(6) 2.89( 1) 2.90( 1) 2.12( 1) 2.15(1) 2.11(2) 168.8(6) 167.5(6) 169.2(7) 169.2(6) 85.0(5) 92.1(5) 83.2(6) 91.0(5)
Li2-N6 Lil-C1 Lil-C9 Li2 -C 17 Li2-C25 Li2-C26 Cl-C2 C9-ClO C17-Cl8 C25-C26 C1-V-C9 C1-V-C17 C17-V-C25 C9-V-N1 C9-V-N2 C25-V-N1 C25-V-N2 N1-V-N2
V(C=CPh)2(TMEDA)2 (2) 2.18(1) C1-C2 2.18(1) C7-C8 2.311(5) 90.6(1) 81.5(3)
C7-V-N
V(C=CtBu)2(TMEDA)2(3) 2.179(2) V-N1 2.358(5) Cl-C2 177.8(2) 81.0(2)
C1-V-N1 C1-V-N2
2.17(2) 2.23(1) 2.20(1) 2.21(2) 2.23(1) 2.81(1) 1.220(9) 1.21(1) 1.210(9) 1.24(1) 95.7(2) 173.2(3) 94.8(3) 89.6(3) 167.6(2) 168.7(2) 90.0(2) 79.3(2) 1.21(1) 1.20(1) 89.4(1)
2.288(4) 1.207(3) 89.5(1) 89.7(1)
V-C1-Lil-C9 quadrilateral is puckered, and so is the V-C17-Li2-C25 quadrilateral. The dihedral angle between the C1-V-C9 and C1-Lil-C9 planes is 28.9', while the corresponding angle for the latter quadrilateral is 31.3'. The V-C1 and V-C17 bonds, which are trans to each other, are 0.047-0.064 A (6a-8a) longer than the other two V-C distances. The stronger trans influence of the alkynide donor relative to the N-donor of TMEDA must be one reason behind the different V-C bond lengths. Despite Li coordination at the a-carbons, the average V-C bond length of 1 (2.153 A) is clearly shorter than the V(I1)-alkyl (sp3 carbon) and V(I1)-aryl bonds (sp2 carbon) in (CsHs)V(CHs)(dmpe)(2.219(4) Alga and in trans-V(o-CsH4NMe2)2(py)2(2.233(4)A).8 The lithiated phenyl complex of V(II), [LiOEt2]4[VPhs], has even longer V-C bonds (2.342(3)-2.383(3)&.12 On the other hand, the V(II1)-alkynide distances in (C5H5)2V(C=CtBu) (2.075(5)AI4 and (C5Me4Et)2V(CECC&Me3) (2.03(1)All6 are shorter than those of 1. The C=C distances of 1 fall in the normal range.17 Thus neither Li coordination nor back-bonding from d3 V(I1) detectably lengthen the CGC bond. The phenyl rings of the transalkynides are situated nearly parallel to each other, which are then approximately perpendicular to the phenyl rings of the other two alkynides. Structures of V(C=CPh)2(TMEDA)2 (2) and V(C=CtBu)2(TMEDA)2(3). The molecular structures (16) Kohler, F. H.; Prossdorf, W.; Schubert, U.; Neugebauer, D. Angew. Chem., Int. Ed. Engl. 1978,17, 850-851. (17) Evans, W. J.; Ulibarri, T. A,; Chamberlain, L. R.; Ziller, J. W.; Alvarez, D., Jr. Organometallics 1990,9, 2124-2130 and references
therein.
Figure 2. ORTEP drawing of the structure of V(CsCPh),(TMEDA)z (2). Only one orientation of the disordered TMEDA ligands is shown.
c299
-
Figure 3. An ORTEP drawing of the structure of V(C=CtBu)2(TMEDA)2(3).The V atom is located on an inversion center, and only one of the positions of the disordered TMEDA ligand is shown. of 2 and 3 are shown in Figures 2 and 3, respectively, and their crystal data are summarized in Tables 1-3. For both 2 and 3, two alkynides coordinate V(I1) in a trans configuration, while two TMEDA molecules form an equatorial girdle. In the case of 2, there is crystallographic mm symmetry, in which one alkynide ligand, Cl-C6, lies on one mirror plane, while the other ligand, C7-Cl2, lies on the perpendicular mirror plane. Thus, unlike 1, the two trans phenyl groups are inherently perpendicular, and the C2-Cl-V-C7-C8 spine is exactly linear. Due to this mm symmetry, the TMEDA ligands are disordered across the mirror planes. For 3 the vanadium atom sits a t a crystallographic inversion center, so that the two alkynide groups are equivalent and so are the two TMEDA groups. These TMEDA ligands are again disordered.18 The V-C bond lengths
4298 Organometallics, Vol. 14, No. 9, 1995
Kawaguchi and Tatsumi
of 2 (2.18(1) A) and 3 (2.179(4) A) are practically identical, and differing the alkynide substituent does not affect the V-C bond length. Interestingly, the V-C bond lengths in these Li-free complexes, Le., V-C1 and V-C19, are indistinguishable from those of 1,in which the alkynides are trans to each other. The V-N distances, on the other hand, even in these sterically crowded bis-TMEDA complexes, are shorter than in 1, in which they are trans to alkynides. In the Cmcm space group, the two TMEDA chelates of 2 should assume either a I I or a 66 configuration in order to avoid steric repulsion between the methyl groups of neighboring amine units. The N-V-N chelate angle of 81.5(3)' is slightly larger than that of 1 (79.3(2)"), and the V-N distance is shorter. The two phenyl groups, situated perpendicular to each other, are both staggered with respect t o the nitrogen atoms of TMEDA. Complex 3 crystallizes in the space group Pi, and the TMEDA molecules are disordered in a different way from 2. The inversion center at vanadium forces a pair of the symmetrically related TMEDA molecules to have the opposite configuration. The N1-V-N2 angle of 81.0(2)Ois similar that of 2. With the exception of the V-N distances trans to an alkynide ligand in 1, all other V-N distances appear normal. The V-N distance in 2, 2.311(5) A similar to that reported for VC12(TMEDAh, 2.319(2) is (averagehs The V-N distances in 3 vary widely. However, this variation is likely artificial, because of the disorder in this complex, and the average V-N distance in 3 is indistinguishable from that observed in the other compounds. Reactions of 1-3. The neutral, bidalkynide) complex 2 smoothly reacts with LiCECPh to afford 1 in good yield. The V(I1) center accommodates four PhCECligands, resulting in the dianionic complex 1 (eq 5), V(CtCPh)2(TMEDA)2 + 2 LiCSCPh 2
THF/TMEDA c
[( LiTMEDA)2V(p-C=CPh)4(TMEDA)] 1 84% yield
-
[(LiTMEDA)2V(pC=CPh)4(TMEDA)]+ 2 RX 1 V(CICP~)~(TMEDA)~+ RCECPh 2 RX = Me3SiCI,73% yield Mel, 66%
(6)
NHPh. Thus, a facile insertion of isocyanate into the V-C a-bond took place. Carbon dioxide inserted in a similar way for 1 and 2 and generated PhCSCC02H after hydrolysis. Thus, in case of the vanadium(I1) acetylide complexes 1-3, electrophiles attack at C, of the CEC fragment. This is similar to the chemistry reported for (C5H&M(C=CPh)2 (M = V, Ti), which was ~ reported to react with HC1 to produce H C E C P ~ .There is no evidence for enhanced nucleophilicity at the 4, carbon as has been observed for some electron rich acetylide compound^.'^-^^ Finally, 2 and 3 were found to react with carbon monoxide under mild conditions to yield a pyrophoric black precipitate with an IR band at 1850 cm-l. This precipitate is tentatively identified as [V(CO)& by reference to the vco band of [Na(diglyme)zI[V(CO)6l (1859 cm-lhZ2 Compounds 2 and 3 may be reduced from WII) to V(-I) upon reaction with CO. The vanadium(111)compound, [V(Mes)3(THF)I,has also been shown to undergo reaction with co to form [v(Co)Sl-(vco = 1862 cm-') and M e ~ C ( 0 ) M e s . ~ ~
Experimental Section General Procedure. All reactions were carried out using standard Schlenk techniques under an argon atmosphere. Solvents were dried and distilled before use according to known methods. VC13(THF)sZ4and VC12(TMEDA)z8were prepared as reported. Infrared spectra were recorded on a Hitachi model 295, while E1 mass spectra were obtained on a JEOL JMS-DX-303 spectrometer. Elemental analyses were performed on a LECO CHN-900 microanalyzer. '
Preparation of [(LiTMEDA)2VOI-C~CPh)4(TMEDA)] (5)
while in the case of t B u C ~ C - ,only two ligands are incorporated t o form the neutral complex 2. The choice may be delicately controlled by the size of the acetylide substituent and/or electronic factors. The high-yield syntheses of the lithiated, anionic complex 1 and the neutral complexes 2 and 3, which are the first alkynide complexes of V(II), provide us with a good opportunity t o examine differences in the reactivity between neutral and anionic alkynide complexes and to compare this reactivity with that of electron rich metals. The reactivity of these complexes is an ongoing study, and we report here some initial results. In the case of 1-3, the alkynide ligands were found to react with organic electrophiles at the a-carbon. For instance, treatment of 1 with 2 equiv of MesSiCl and Me1 resulted in formation of 2 along with MesSiCSCPh and MeCZCPh, respectively (eq 6). Addition of phenyl isocyanate to a THF solution of 3, and subsequent hydrolysis with aqueous HC1 generated tBuCWC(0)(18)See supporting information, in which the disordered structures of 2 and 3 are described in detail.
(1). Method 1. A THF (30 mL) solution of LiC=CPh (16.4 mmol) was added to VCldTHF)3 (1.09 g, 2.92 mmol) in THF (30 mL) containing TMEDA (10 mL) a t 0 "C. The solution was stirred a t room temperature for 2 h, during which time the color gradually turned from brown to purple. After removal of solvent in uucuo, the purple residue was treated with hexane (100mL)A'MEDA (1mL). The hexane solution was centrifuged to remove insoluble LiCl and was concentrated to yield 1 as purple crystals (1.52 g, 64%): IR (Nujol) 2000 (s), 1964 (w) cm-'; UV-visible (A,,,, nm, THF) 490. Anal. Calcd for CsoHssNsLizV: c, 73.42; H, 8.38; N, 10.27. Found: C, 72.02; H, 7.36; N, 9.32. All of the vanadium(I1) alkynide complexes reported in this paper are sensitive to air and moisture, hindering attempts t o obtain satisfactory elemental analyses. Method 2. A THF (30 mL) solution of L i C 4 P h (16.4 mmol) was added at 0 "C to VClZ(TMEDA)z(1.40 g, 4.05 mmol) in THF (30 mL)/TMEDA (2 mL). Workup similar to that in method 1 above yielded 1 (2.77 g, 84%). ~ _ _ _ _
(19)Kelly, C.; Lugan, N.; Terry, M. R.; Geffroy, G. L.; Haggerty, B. S.; Rheingold, A. L. J. Am. Chem. SOC.1992, 114, 6735-6749. (20)Birdwhstell, K. R.; Templeton, J. L. Organometallics 1986,4, 2062-2064. (21) Bruce, M. I. Chem. Rev. 1991,91, 197-257. (22) Connelly, N. G. Vanadium. In Comprehensiue Organometallic Chemistry; Wilkinson, G., Stone, F. G. A,, Abel, E. W., Eds.; Pergamon: Oxford, U.K., 1981; Vol. 3, Chapter 24, pp 648-649. (23)Vivanco, M.; Ruiz, J.; Floriani, C.; Chiesi-Villa, A,; Rizzoli, C. Organometallics 1993, 12, 1794-1801. (24)Manzer, L. E. Inorg. Synth. 1982,21, 135.
Organometallics, Vol. 14, No. 9, 1995 4299
Vanadium(II)Alkynide Complexes Preparation of V(C=CPh)2(TMEDA)2(2). Method 1. A mixture of LiCECPh (8.95 mmol) and VC13(THF)3(1.10 g, 2.94 mmol) in THF (70 mL)/TMEDA (10 mL) was treated as described above to give 1 in 4% yield (based on vanadium, 0.26 g) and the brown solid insoluble in hexane. Compound 2 (1.02 g, 71%) was extracted from the brown residue by THF (100 mL)/TMEDA (5mL). Data for 2: IR (Nujol) 2020 (s) cm-'; E1 MS m / e 485 (M+), 369 (M+ - TMEDA). Anal. Calcd for Cz8H42N4V C, 69.25; H, 8.72; N, 11.54. Found: C, 69.96; H, 8.63; N, 11.38. Method 2. Addition of LiC=CPh (7.01 mmol) in THF (30 mL) to VClZ(TMEDA)z (1.23 g, 3.47 mmol) in THF (40 mL)/ TMEDA (2 mL) at 0 "C, followed by workup similar to the above yielded 1(0.05 g, 2% based on vanadium) and 2 (1.34 g, 85%). Preparation of V(C=CtBu)2(TMEDA)2(3). Method 1. The same procedure as used for 1 was followed. Reaction of LiCECtBu (12.7 mmol) in THF (30 mL) with VC13(THF)3 (1.69 g, 4.52 mmol) in THF (40 mL)/TMEDA (5 mL) afforded 3 as brown purple crystals (1.13 g, 56%): IR (Nujol) 2035 (s) cm-'; E1 MS m l e 445 (M+), 363 (M+ - HCW'Bu), 329 (M+ TMEDA), 247 (M+ - TMEDA - HC=CtBu); UV-visible (A,,,, nm, THF) 530. Anal. Calcd for C Z ~ H ~ ~C,N64.69; ~ V H, 11.31; N, 12.57. Found: C, 63.76; H, 10.88; N, 12.36. Method 2. Analogous t o method 2 for the preparation of 2, LiC=CtBu (9.79 mmol) in THF (30 mL) and VClz(TMEDA12 (1.70 g, 4.80 mmol) in THF (50 mL)/TMEDA (4 mL) produced 3 (1.56 g, 73%). Attempt to Isolate the C=CtBu Analogue of 1. Method 1. A THF (30 mL) solution of LiC=CtBu (19.6 mmol) was added to VC13(THF)3 (1.45 g, 3.88 mmol) in THF (40 mL)/ TMEDA (6 mL) a t 0 "C. The solution was warmed to room temperature with stirring. Within a few minutes, the color of the solution changed from brown to greenish brown. After that, workup similar to 1 afforded 3 (0.19 g, 11%). Method 2. Addition of LiCzCtBu (12.7 mmol) in THF (30 mL) to VClz(TMEDA)z (1.02 g, 2.88 mmol) in THF (50 mL)/ TMEDA (5mL) followed by workup similar t o method 1above provided 3 (0.21 g, 16%). Reaction of VC13(THF)3with LiC=CPh in DME. LiC=CPh (15.5 mmol) in DME (40 mL) was added to a DME (30 mL) solution of VC13(THF)3a t 0 "C. As this solution was stirred at room temperature for 2 h, the color changed from brown to purple. The resulting solution was centrifuged to remove insoluble products. The purple solution was concentrated to afford Liz(DME)xV(C=CPh)4(4) as red purple crystals (1.10 g): IR (Nujol) 2000 (s), 1960 (w) cm-'. Reaction of 2 with LiCECPh. A THF (20 mL)rTMEDA (1 mL) solution of 2 (0.46 g, 0.95 mmol) was treated as described for 1 with LiClCPh (1.90 mmol) in THF (10 mL). Compound 1 (0.64 g, 83%) was obtained as purple crystals. Reaction of 1 with Me3SiCl and MeI. Me3SiCl (O.llm1, 0.87 mmol) in THF (5 mL) was added to a THF (20 mL) solution of 1 (0.33 g, 0.40 mmol) and TMEDA (1mL) a t room temperature. The initially purple solution immediately became brown and was stirred a t room temperature for l h. The solvent and PhC'CSiMe3 were removed under vacuum to leave a brown crystalline solid, which was recrystallized from THFrTMEDA, giving 2 as brown crystals (0.14 g, 73%). Similar reaction with Me1 afforded 2 in 66% yield. The GSMS spectra of the solutions showed P h c ~ C S i M e 3and PhCE CMe, respectively. Reaction of 1 and 2 with C02. A THF (20 mL) solution of 1 (0.23 g, 0.28 mmol) was stirred under COz (1atm) for 1h.
Addition of aqueous HC1 to the THF solution followed by extraction with ether gave PhCsCCOzH (0.11 g, 66%) as colorless crystals: IR (Nujol) 2660 ( 4 , 2 5 7 5 (SI, 2220 (sh), 2198 (s), 1670 (s) cm-'. The reaction of 2 (0.10 g, 0.21 mmol) and COz followed by a similar workup also gave PhC=CC02H (33 mg, 54%). Reaction of 3 with PhNCO. Compound 3 (0.34 g, 0.76 mmol) was treated as described above with 2 equiv of PhNCO (0.17ml,1.56 mmol) in THF (20 mL). t B u C 4 C ( 0 ) N H P h(0.19 g, 61%) was obtained as colorless crystals: IR (Nujol) 3240 (s), 3125 (s), 3060 (sh), 2280 (w), 2220 (s) cm-'. Anal. Calcd for C13H15NO: C, 77.58; H, 7.51; N, 6.96. Found: C, 77.20; H, 7.53; N, 7.20. Reaction of 2 and 3 with CO. A THF (20 mL) solution of 2 (0.13 g, 0.27 mmol) was stirred under CO (1 atm) a t room temperature for 3 days. A black pyrophoric precipitate was obtained (40 mg), which has an IR band at 1850 cm-I (Nujol) (cf. 1859 cm-' for [V(CO),& in THFlz1 Compound 3 (0.67 g, 1.51 mmol) also underwent a similar reaction with CO to give a black precipitate (61 mg).
Crystal Structure Determination of Complexes 1-3. Crystals of 1-3 suitable for X-ray analysis were mounted in glass capillaries and sealed under argon. Diffraction data were collected a t room temperature on a Rigaku AFC5R diffractometer employing graphite-monochromated Mo Ka radiation (I= 0.710 690 A) and using the w-28 scan technique. Refined cell dimensions and their standard deviations were obtained from least-squares refinements of 25 randomly selected centered reflections. Three standard reflections, monitored periodically for crystal decomposition or movement, showed only slight intensity variation (-1%)over the course of the data collections. The raw intensities were corrected for Lorentz and polarization effects. Empirical absorption corrections based on q j scans were applied. All calculations were performed with SHELX76. The structures of 1 and 2 were solved by the Patterson method, and the structure of 3 was solved by direct methods, locating in all three cases the vanadium position. The other atoms were found in subsequent Fourier maps, and the structures were refined by full-matrix least squares. Anisotropic refinement was applied t o all non-hydrogen atoms, including the disordered carbon a n d o r nitrogen atoms in 2 and 3. The hydrogen atoms on the two phenyl groups of 2 were located and refined isotropically, while the other hydrogens were put a t calculated positions. Additional information is available as supporting information.
Acknowledgment. We are very grateful to Prof. T. Yoshida at the University of Osaka Prefecture for open access to the diffractometer for the crystal structure analysis of 3. We also thank Prof. Roger E. Cramer for stimulating discussions and careful reading of the manuscript, who is at Nagoya University on sabbatical leave from University of Hawaii, U.S.A. Supporting Information Available: Tables giving atomic coordinates and isotropic thermal parameters, bond distances and angles, hydrogen coordinates, and anisotropic thermal parameters of 1-3 and text and figures giving details on the disordered structures of 2 and 3 (23 pages). Ordering information is given on any current masthead page. OM9502260
