Organometallics 1982, 1, 251-259 spectively, of Figure 5. The principal effect of the hydrogen is stabilization of the 3al orbital and withdrawal of charge from the aluminum. The charge withdrawal has two effects. First, it stabilizes the 3s A1 orbitals by increasing the positive charge on Al, thus allowing them to participate more fully in bonding. Secondly, it greatly (10) As suggested by a reviewer, a thermodynamic measure of the degree of XC double bonding in thew compounds as well as AICHzand BCHzmight be obtained by consideringisodesmicreactions of the form HXCHz + XH, XCHz + XH,+, (1) XHz + XH, XH + XH,,, X = B, Al; n = 0,1,2 (2) In the table below we give heeta of reaction for these two reactions with the same basis set employed throughout our study.
-
-
kcal,mol AE,, reaction 1 n X=AI X=B 0 1
2
-66.0 +76.5 -177.3
+29.7
+77.8 -87.3
reaction 2 X=Al
X=B
-142.5 0.0 -253.8
-48.1 0.0
-165.1
It is clear from the energiea for the second reaction that bonding to either Al or B is very sensitive to the value of n. This variability makes it difficult to evaluate changes in the XC bonding from reaction 1. Although the trends are interesting and worthy of future study, the differencea in spin multiplicity and coordination number make a detailed analysis at the minimal basis set level impractical.
251
reduces the electron-electron repulsion between the 2al and the 3al orbitals. Both effects will tend to reduce the A1-C bond length. A shorter bond length also increases the AI 3p,-C 2p, overlap leading to additional stabilization of the lbl orbital. We note, however, that the relative Mulliken population of the l b l orbital on the A1 is only 28% (11% in AICH2) and thus remains highly polarized.
Note Added in Proof. We have implicitly assumed the BC double bonded species, B=CH2 and HB=CH2, to be the expected and normally occurring reference compounds. However, BC double bonds have not, in fact, been observed (Onak, Thomas "Organoborane Chemistry"; Academic Press: New York, 1975; p 4). This fact undoubtedly derives from the relative stability of isomers with BC single bonds and therefore does not invalidate the BC double bonds we have calculated. It may actually enhance the value of our computational results because they elucidate the nature of a bond which has proved difficult to isolate experimentally. Acknowledgment. We wish to thank the NIH (Grant GM 26462) for financial support. Registry No. AlCH2, 76392-50-2; BCH2, 79435-75-9; HAICH2, 79435-76-0; HBCHZ, 56125-75-8.
.'
The Molybdenum-Molybdenum Triple Bond. 11 1,I-and 1,2-Disubstituted Dimolybdenum Compounds of Formula M O ~ X , ( C H ~ S I M(MWl). ~ ~ ) ~ Observation of Rotation about the Triple Bond M. H. Chisholm,' K. Folting, J. C. Huffman, and I. P. Rothwell Department of Chemistry and Molecular Structure Center, Indiana Universiv, Bioomington, Indiana 4 7405 Received August 3, 198 1
The preparation and characterization of a series of compounds of general formula Mo2X2R4(M=M), where X = Br, Me, 0-i-Pr, 0-t-Bu, and NMe2and R = CH8iMe3,are reported. The pattern of substitution may be 1,l-, X2RMmMo&, or 1,2-,WM-MohX, depending upon the nature of X and the preparative route. The 1,l-and 1,2-M%X2R4compounds do not isomerize, demonstrating the existence of a high kinetic barrier to R and X group transfer between molybdenum atoms. Alkyl group transfer may occur during the substitutionreaction: l,2-MQr2R4and LiNMez (2 equiv) yield 1,1-Mq(NMeJzR4,whereas 1,2-M%Br2R4 and HNMe2yield l,2-Mo2(NMe 2R4. The formation of one isomer of Mo2(NMeJ2R4must occur by kinetic control. Variable-temperature H NMR spectra for 1,l- and ~ , ~ - M O ~ ( Ncompounds M ~ ~ ) ~ provide R~ the first observation of rotation about the M m M o bond. The energy barriers to rotation are reconcilable with steric restraints. By contrast, the barriers to rotations about Mo-N bonds in the 1,l- and 1,2Mq(NMeJ2R4compounds are AG' (kcal mol-') = 11.5 f 0.5 and 15.0 f 0.5, respectively, and the difference is correlated with electronic factors. The structure of 1,2-M0~(0-t-Bu)~R~, determined by a single-crystal X-ray diffraction study, revealed a staggered ethane-like (C,) anti-Mo20C4central skeleton with Mo-Mo = 2.209 (2) A, Mo-0 = 1.865 (8)A, and M o - C = 2.13 (1)and 2.14 (1) and internal angles Mo-Mo-0 = 110.7 (3)O and Mo-Mo-C = 100.1 (5)' (averaged). Crystal data at -163 "C were a = 10.025 (3) A, b = 18.473 (9) A, c = 9.975 (5) A, j3 = 102.03 (3)O, 2 = 2, and ddd = 1.263 g cm-' with space group R1/n. These new observations are discussed in the light of previous work.
zi'
x
Introduction the first paper of this series, the preparation and of M ~ ~ ( N (MM~~ ~M)was ) ~ redetailed ported.2 This compound has since been the parent of an (1) Chisholm, M. 1981,20,2215.
H.; Huffman, J. C.; Rothwell, I. P. Znorg. Chem.
0276-7333/82/2301-0251$01.25/0
extensive family of others and affords an easy entry into the rich chemistry associated with the M e M o bond in M ~ ~ ~ + - c o n t a i n~ionm g p o u n d s . ~Two ? ~ views of the Mo2(2) Chisholm, M. H.; Cotton, F. A,; Frenz, B. A,; Reichert, W. W.; Shive, L. W.; Stulta, B. R. J. Am. Chem. SOC.1976,98,4469. (3) Chisholm, M. H.; Cotton, F. A. Acc. Chem. Res. 1978, 11, 356. (4) Chisholm, M. H. Symp. Faraday SOC.1980, No. 14,194. 0 1982 American Chemical Society
Chisholm et al.
252 Organometallics, Vol. 1, No. 2, 1982 Scheme I 1,2 - Ma2BrZR4
we2
bLiNMe2
-Jt-
1 ,2-Mo2(NMe2),R4
1
excess CO2
1,l
k
t
1 , 2 - Mo2Me2R4 (50%) -
6
I \
.
1,
1.1 -Mc2(NMe2),R, excess C o p
NR
2MeLI
' - M C ~ ( O - ~ - B U( )3~0 R % ~)
+
1,2 - M o Z ( O - t - B u ) ~ R (70%) ~
excess '-"OH
- Mo21NMe~)(OZCNMe2)R4
1.1 - M O Z ( O - ~ - B U ) ~ R ~
l , l - M o , X , R , = MoX~REMOR,;1,2-Mo,X,R4 = MoXR,=MOXR,
(NMez)e molecule are shown from which it can be seen that there are six proximal and six distal methyl groups.
a
2C( 131
nlC C
(NMe2)6,since bridging dialkylamido ligands are known, e.g., as in Cr2(02CNEt2)4(w-NEt2)2.g Further work led to the isolation and characterization of 1,2-M2%(NR'2)4compounds, where R = alkyl, R' = Me or Et, and M = Mo and W.l0 These compounds exist in solution as mixtures of anti and gauche rotamers and show activation barriers to anti + gauche isomerization in the range 21-25 kcal mol-', depending on the nature of R and R'.ll The mechanism of this isomerization either could involve a direct rotation about the M=M bond or could be achieved by an indirect route in which NR2 groups were scrambled across the M s M o bond. Being afflicted with this uncertainty, we resolved to synthesize related molecules for which these two processes would be distinguishable. Since the cogging effect of the interlocking NC2 units in M&(NMeJ4 compounds could be responsible for hindering rotation about the M o r M o bond, we set out to prepare related Mo2X2(CH2SiMe3), compounds which would be less sterically encumbered and would have methylene protons placed as stereochemical probes adjacent to the central Mo=Mo bond. For an ethane-like molecule, these methylene protons would have to be diastereotopic, but a fluxional process involving passage through an intermediate or transition state of the type shown below would cause the methylene protons to be equivalent.
LW
/I
A
-
W
On the 'H NMR time scale, these interconvert slowly at low temperature ( 16 kcal mol anti gauche, 2 1 i 1 anti* gauche, 24 i 1 14.0 ? 1 15.6 ? 1 not observed, < 8
Bondsa
M- .N 11.5 ? 0.5 11.2 k 0.5 13.6 k 0.5 14.0 ? 0.5 (11-14) (11-14) 10.3 k 0.5 15.0 k 0.5
ref b C
b d e
f
this work this work this work
a Estimates from coalescence temperature by using the Gutowsky-Holm equation: Pople, J. A.; Schneider, W. G.; Burnstein, H. J. “High Resolution NMR Spectroscopy”; McGraw-Hill: New York, 1959; p 223. Chisholm, M. H.; Cotton, F. A.; Frenz, B. A.; Reichert, W. W.; Shive, L. W.; Stults, B. R. J . Am. Chem SOC.1976, 96, 4469. Chisholm, M. H.; Cotton, F. A.; Extine, M. W.; Stults, B. R. Zbid. 1976, 96, 4477. Akiyama, M.; Chisholm, M. H.; Cotton, F. A.; Extine, M. W.; Murillo, C. A. Inorg. Chem. 1977, 16, 2407. Chisholm, M. H.; Cotton, F. A.; Extine, M. W. ; Millar, M. ; Stults, B. R. Ibid. 1976, 15, 2244. f Chisholm, M. H.; Extine, M. W. J. Am. Chem. SOC.1976,98,6393.
However, neither of these mechanisms could account for t h e alkyl migration observed in t h e reaction between l,l’-Mo2(NMe2)(02CNMe2)R4 and t-BuOH, which leads t o a mixture 1,l-and 1 , 2 - M 0 ~ ( 0 - t - B u ) ~ R ~ M e M o and Mo-N Roational Barriers. Rotational barriers, calculated from t h e variable-temperature dependence of the ‘H NMR spectra, are given in Table I1 for t h e 1,l-and ~ , ~ - M O ~ ( N compounds. M ~ ~ ) ~ R For ~ a nonlinear molecule having a cylindrical triple bond (a2 7r4), there should be no electronic or quantum mechanical barrier to rotation. It is of significance, therefore, t h a t of the Mo2X2R4compounds studied, only when X = NMe2, have we observed a barrier to rotation in the range which is observable by NMR spectroscopy (AG*> 8 kcal mol-’) and it is reasonable t o assign t h e origin of the barrier t o steric factors. T h e NC2 units which are aligned along the axis introduce cogging between t h e two ends of t h e molecule. This is more pronounced for gauche 1,2-Mo2-
+
(17)The compound (Me8SiCHJzMo(CH~iMezCHz)Mo(PMe3)3 (ME M) has been isolated from the reaction between Moz(OAc)d, Me&3iCHzMgC1,and PMe6 Andersen, R. A.; Jones, R. A.; Wilkinson, G. J. Chem. SOC., Dalton Tram. 1978,446.
(NMe2)2R4than for the 1,l isomer, since t h e two NC2 blades cannot allow a facile gauche-gauche’ (enantiomerization) rotation without a twisting or simultaneous rotation about Mo-N bonds. It is quite likely t h a t this causes the slighlty higher activation t o rotation about the Mo=Mo bond in t h e 1,2 isomer. Proximal distal methyl exchange is quite significantly slower for t h e ~ , ~ - M O ~ ( N isomer. M ~ ~ )One ~ Rmight ~ initially be tempted t o believe t h a t this also correlates with t h e greater contact of t h e NC2 units in t h e gauche-1,2M O ~ ( N M ~ molecule. ~ ) ~ R ~ However, this idea falls into trouble when one recognizes t h a t in Mo2(NMe&, a molecule which has all six NC2 blades meshed, the energy of activation is only 11 kcal mol-’-as is found for t h e 1 , l M O ~ ( N M ~ ~ isomer. ) ~ R , Consequently, we believe t h a t electronic factors must be responsible for t h e higher activation energy for the 1,2 isomer. As a result of forming three a bonds and the Mo=Mo bond, each molybdenum atom achieves only a 1 2 valence shell of electrons in X3Mo=MoX, compounds. This number falls short of satisfying the EAN rule and A donation from X is possible when X = NR2 or OR, b u t not R. This ligand t o metal A donation is favored when the NC2 units are aligned along
*
256 Organometallics. Vol. 1, No. 2, 1982
Chisholm et al. Table 111. Fraetional Coordinates for the l,Z-Mo,(C.f.Bu),(CH,SiMe,), Molecule“ lOBh,
atom
105
Mo(1)
5311(1) 6903(9) 8049 (12) 7875116) 8iioji4j 9327(15) 3525(11) 3730 (3) 4094(12) 5145(12) 2121(13) 5477 (13) 7070(3) 8584(14) 7A53(14) 6768(15)
O(2)
c(3) C(4) c(5j C(6) c(7)
Si(8)
Figure 3. An ORTEP view of 1,2-Mol(O-t-Bu)2(CH1iMe~), m o l d e showing the atom numbering acheme used in the tables.
C(9) C(10) C(11) C(12) Si(13) C(14) c(15) C(16)
104~ 359.8(5) 860(5) 1098 (6) 871(81 i925(7j 833(11) 1012 (6) 1998 (2) 2394(6) 2196(6) 2418(6) -409 (7) -386(2) -791(8) 572(8) -939(8)
1042
A’
S95(1) 790(8) 228(13) -1257(16) 278iifij 1204(18) 691(11) 884 ( 3 ) -708(12) 2364(11) 1199(13) 2520 (14) 391(3) 3331(15) 4540(14) 5355(14)
15 30 25 43 37 53 19 19 24 22 27 34 22 35 35 39
the Mo-Mo axis (defined as the z axis): the d, and dyC lOBb, atomic orbitals are used in forming the Mo-Mo r bonds, at” 103~ 109 10~2 A2 while one set of in-plane atomic orbitals (pz, py) or ( d e , 106 108 -178 53 d,) is avaiable for receiving ligand r electrons. In this way H(l) 863 103 -161 53 in 1,1-Mo,(NMe2)2R4,one molybdenum atom attains a 16 H(2) 782 36 -132 53 208 120 47 W4) H(3) 823 valence shell of electrons, but in the 1,2 isomer, a 14 vaH(5j 885 209 -10 47 lence shell is all that is possible. Thus, ligand to metal r 728 212 -24 47 .~ bonding is expected to be more important in each Mo-N 930 32 128 63 bond in the 1,2 isomer than in the 1.1isomer. This in tum 1011 97 86 63 yields a higher M r N rotational barrier for the 1,2 isomer. 938 104 63 208 Within this line of reasoning, it should be noted that the 299 92 29 -20 85 305 M d bond distances in 1,2-M%(0-t-Bu).Jt4 (see below) 29 136 218 490 34 -89 are shorter than in the related compounds Mo2335 230 -145 34 Mo(0-t(0CH2CMe3)6.’6 M O ~ ( O S ~ M ~ ~ ) ~ and (HN M~~)~~~ 421 290 -60 34 B~)~(py)~(C0),, which have decreasing degrees of oxy494 200 317 32 gen-to-molybdenum r bonding. 597 199 221 32 S o l i d - s t a t e S t r u c t u r e of l,2-Mo2(O-t-Bu),525 271 247 32 (CHzSiMe3),. An ORTEP view of the molecule giving the 224 293 129 37 139 231 45 37 atom numbering scheme is shown in Figure 3 and a view 192 223 202 37 of the molecule looking down the M r M o axis, which 412 -34 44 294 clearly e m p h a s i i the dispition of alkyl ligands,is shown 542 44 212 -88 in Figure 4. Final atomic coordinates and thermal pa840 -128 45 309 rameters are given in Table 111 and IV, respectively. 874 45 256 -53 Hi25i -7fi 405 AS 937 .. ... .. Complete listings of bond distances and angles are given 825 58 524 45 in Table V and VI, respectively. RI.7 759 380 45 In the solid state, 1,2-Mq(O-t-Bu)& exists in the anti 67 1 489 45 76 rotameric form and has a crystallographically imposed -75 602 569 50 center of inversion. The Mo-Mo distance is 2.209 (2) A, -142 657 505 50 which is longer than in Mo,(CHfiiMe& (2.169 (?) but -93 756 607 50 shorter than that in M%(0CHzCMeJ6(2.222 (2) A)?8 The The isotropic thermal parameter listed for those atoms M o 4 distanee, 1.865 (8)A, is slighlty shorter than those in Moz(0CH2CMe3)k8and Moz(0SiMe3)6(HNMe2)z’S refined anisotropically are the isotropic equivalent. Numbers in parenthew in this and all following tables refer to which, together with the obtuse Ma-0-C angle, 158.4 the error in the least significant digits, Estimated stand(7)O, is indicative of strong oxygen-to-molybdenum r ard deviations greater than 29 are not statistically bonding. The internal angles for the Mo20,C4 unit are significant but are left “unrounded”, since the tablesare all produced automatically by the X-TEL interactive similar to those in other ethane-like Mo,“+-containing programs. compounds. The Mo-Mo-0 angle (110.7 (3)”) and the Mo-Mo-C angles (100.0 (3)O and 100.2 (4)O) probably consistent with the view that the origin of the barrier is reflect the packing of the tert-butyl and trimetbylsilyl steric and not electronic. bond, groups which are proximal and distal to the M-Mo 1.1- and 1,2-MozXzR, compounds do not isomerize respectively. readily which implies a high barrier to alkyl group miConcluding Remarks. Rotation about the M e M o gration across the M e M o bond. Bridged MozXzR4 bond has been observed and rotational barriers appear very compounds must be relatively high-energy species, problow ( 2.33o(F) was 2715. a above. The structure was solved by a combination of direct methods (c) Small scale reactions were carried out in sealed NMR tubes and Fourier techniques. All nonhydrogen atoms were located and to monitor with time the reaction beheen LiO-t-Bu and 1,2refined by full-matrix least-squares using anisotropic thermal Mo2Br2R4.These showed the initial, relatively fast, formation parameters. The final R was 0.083 for 2620 reflections having of l,2-Mo2Br(O-t-Bu)R4,followed by formation of the 70:30 F > 3a(F). The hydrogen atoms were included as fixed atoms mixture of 1,2- and l , l - M 0 ~ ( 0 - t - B u ) ~ R ~ positions, each having an isotropic B equivalent to Reaction of ~ , ~ - M O ~ ( N M ~ ~ )with ~ (t-BuOH. C H ~ S A~ M ~ ~in)calculated ~ that of the parent C atom plus 1. An isotropic extinction palarge excess of t-BuOH in benzene (azeotrope) was added to a rameter was included in the refinement: the final value was 1.878 solution of ~ , ~ - M o , ( N M ~(ca. ~ ) ~0.4 R ,g) in hexane (10 mL). The X 10 exp(-6). No absorption correction was performed. solution was stirred for 1 2 h, and then the solvent was stripped The maximum peak height in the final Difference map was 2.1 to give a red solid which was identified by 'H NMR spectroscopy e/A3. The peaks could not be interpreted in terms of a solvent as l,l-M0~(0-t-Bu)~R, contaminated with ca. 5% of 1,2-MoZ(Omolecule or disorder. We are unable to account for the rather t-Bu),R, which presumably arose from the ca. 5% impurity of high value of R. Attempts at changing the weighting scheme by the ~ . ~ - M o ~ ( N isomer M ~ ~ in ) ~the R sample ~ of l,l-Mo2(NMeJ2R1. changing the uncertainty factor did not improve the refinement. The red solid sublimed at 80 "C (lo4 torr) with little decompoWe did note that R was fairly independent of sin 8 and dependent sition and no apparent isomerization. of the magnitude of F: R increased with decreasing values of F. Neither the lJ-,nor the l,2-Mq(O-t-Bu),R4 compounds reacted The overall R for 3190 reflections was 0.093. with COz nor was isomerization observed in the presence of excess LiO-t-Bu or t-BuOH. Acknowledgment. We thank t h e donors of t h e PeReaction of l,l'-MoZ(NMez)(02CNMe2)(CH2SiMe3), with troleum Research Fund, administered by t h e American t-BuOH. Addition of an excesa of t-BuOH in benzene (azeotrope) to a hexane solution of 1,1'-Mo2(NMeZ)(02CNMe2)R4 yielded a Chemical Society, the National Science Foundation, and red solution within 0.5 h. Stripping the solvent yielded red solids t h e Wrubel Computing Center at Indiana University for which, by 'H NMR spectroscopy, were determined to be an ca. support of this work. M.H.C. is also grateful for a Camille 4:l mixture of 1,2- and l , l - M 0 ~ ( 0 - t - B u ) ~respectively. R~, 'H NMR Data. 'H NMR data for the compounds 1,2M o , X ~ ( C H ~ S ~recorded M ~ ~ ) ~in toluene-de at 220 MHz and 16 (21)Huffman, J. C.;Lewis, L. N.; Caulton, K. G . Inorg. Chem. 1980, " C . ( a ) X = Br: 1.49 4.76 (d), 0.73 (d, J = 11.1Hz); 6(SiMe3) 19, 2755.
Organometallics 1982,1, 259-263 and Henry Dreyfus Teacher-Scholar Grant.
259
75059-95-9; 1,2-Mo2Br(O-t-Bu)(CH2SiMe3),, 79172-47-7; 1,2-
M O ~ M ~ B ~ ( C H ~79172-75-1; S ~ M ~ ~M ) ~O,~ ( C H , S ~ M 34439-17-3. ~~)~,
Registry No. 1,2-M02B~(CHfiiMe~)~, 75059-90-4; 1,2-Mo2Me275059-94-8; (CH~S~M~~ Supplementary )~, Material Available: A listing of observed (CHpsiMe~)~, 75059-91-5; ~ , ~ - M O ~ ( N M ~ ~ ) ~ ~ , ~ - M O ~ ( N M ~ ~ ) ~ (76599-13-8; C H ~ S ~ Ml,1'-Mo2~ ~ ) ~ , and calculated structure factors (20 pages). Ordering information (NMe2)(O&NMe2)(CHzSiMes),, 76716-47-7; 1,2-M0~(0-t.B~)~- is given on any current masthead page. The complete structural (CHfiiMe3),, 75069-93-7; 1,2-M%(O-i-Pr)2(CH2SiMes)4, 75059-92-6; report, MSC Report 8024, is available in microfiche form only, from the Indiana University Library. M O ~ B ~ ( C H ~ S79172-46-6; ~ M ~ ~ ) ~l,l-M0~(0-t-Bu)~(CH~SiMe~),, ,
Unsaturated (.lr-Allyl)nlckel Halide Complexes. Reactions To Produce Dienes Louis S. Hegedus' and Sudarsanan Varaprath Department of Chemistty, Colorado State University, Fort Coiiins, Coiorado 80523 Received August 18, 1981
The (a-ally1)nickel halide complexes of l-bromohexa-2,5-diene (l),l-bromopenta-2,4-diene (2), 1bromohexadP-diene(31, and 2-(bromomethyl)-l,&butadiene (4) were prepared from either nickel carbonyl or bis(cyc1ooctadiene)nickel and were characterized. The nonconjugated (a-l-(2-propenyl)allyl)nickelhalide complex 1 reacted cleanly with iodobenzene, 8-bromostyrene, cinnamyl bromide, iodocyclohexane, iodohexane, o-brolpobenzamide,and o-bromoaniline to replace the halogen with the 1,4-hexadienylgroup. The complexes from 1-bromopenta-2,Cdiene (2)and l-bromohexa-2,4-diene(3) were considerably less useful, reacting only with the very reactive substrates iodobenzene, cinnamyl bromide, and j3-bromostyrene. The complex from 2-(bromomethyl)-l,&butadiene (4) was used to synthesize myrcene, 8-farnesene,and tagetol. (a-Ally1)nickelhalide complexes are easily prepared from the reaction of allylic halides with either nickel carbonyl or bis(cyc1ooctadiene)nickel in a nonpolar solvent such as benzene. The complexes are usually deep red crystalline, air-sensitive solids that can be stored in the absence of air for at least several years. In polar solvents such as DMF, they are generally reactive toward a wide range of organic halides, reacting to replace the halide in the substrate with the allyl group originally on nickel.' Under more severe conditions, some (a-ally1)nickelhalide complexes react with ketones or aldehydes to produce homoallylic alcohols.2 In relation to ongoing studies directed toward the synthesis of heterocycles by palladium-catalyzed cyclizations of amino olefins,= a number of diene-containing substrates were required. Although a number of new methods for the introduction of pentadienyl and hexadienyl groups into organic substrates have been recently reported,'+' none offered viable approaches to the desired substrates. Thus, (1) For reviewe concerning the preparation and reactions of (r-ally1)nickel halides see: (a) M.F. Semmelhack and P. Helquist, Org. Synth. 62, 115 (1972); (b) M. F. Semmelhack, Org. React., 19,115 (1972); (c) R. Baker, Chem. Reo., 73,787 (1973); (d) L. S. Hegedus,J. Organomet. Chem. Libr., 1, 329 (1976). (2) (a) E. J. Corey and M. F. Semmelhack,J.Am. Chem. SOC.,89,2755 (1967); (b) L. S. Hegedue, S. D. Wagner, E. L. Waterman, and K. Siirala-Hansen, J. Org. Chem., 40, 593 (1975). (3) D. E. Korte, L. S. Hegedue, and R. K. Wirth, J. Org. Chem., 42, 1329 (1977). (4) L. S. Hegedue, G. F. Allen, J. J. Bozell, and E. L.Waterman, J. Am. Chem. SOC.,100, 5800 (1978). (5) L. S. Hegedue, G. F. Allen, and D. J. Oleen,J.Am. Chem. Soc., 102, 3583 (1980). (6) L. S. Hegedus,P. M. Winton,and S. Varaprath, J.Org. Chem., 46, 2215 (1981). (7) For the Lewis acid catalyzed reactions of dienyleilanes with electrophilea see: A. Hosomi, M. Saito, and H. Sakurai,Tetrahedron Lett., 21,-3783 (1980). (8)For an approach to the isoprene synthon see: S. R. Wilson, L. R. Phillips, and K. J. Natalie, Jr., 2.Am.-Chem. Soc., 101, 3340 (1979). (9) C. A. Henrick, Tetrahedron, 33, 1845 (1977).
we synthesized four new (a-ally1)nickelhalide complexes containing an additional double bond and studied their reactions with organic halides and carbonyl compounds. Results and Discussion Preparation of (wAlly1)nickel Halide Complexes Complex 1 was,prepared in 76% isolated yield on a 10-g
-1
-
2
4 scale by the reaction of a mixture of l-bromo-2,5-hexadiene and 3-bromo-1,bhexadienewith nickel carbonyl in benzene at 70 "C. This stable red crystalline solid was a typical (a-ally1)nickel halide complex in both its physical and chemical characteristics. In that regard, complex 1 is similar to other nonconjugated,unsaturated (a-ally1)nickel halide complexes such as those containing vgeranyl ligands.lD 3
0276-7333/82/2301-0259$01.25/00 1982 American Chemical Society
