2716
Journal of the American Chemical Society
(1 1) (a) S. W. Kirtiey, M. A. Andrews, R. Bau, G. W. Grynkewich, T. j. Marks, D. L. Tipton, and 8. R. Whittiesey, J. Am. Chem. Soc., 99, 7154 (1977); (b) T. J. Marks and W. J. Kennelly, ibid., 97, 1439 (1975). (12) (a) The computer programs which were used in performing the necessary Caicuiations, with their accession names in the World List of Crystallographic Computer Programs (3rd ed), are as follows: data reduction and absorptlon corrections, DATALIB; data averaging and sort, DATASORT, Fourier summation, FORDAP; least-squares refinement, OR XLFSB; error analysis ; drawings, OR TEPII;least-squares of distances and angles, OR F F E ~structural planes, MPLANE by M. E. Plppy and F. R. Ahmed. For the direct method calcuiations, MULTAN was used: J. P. Declercq, 0.Germain, P. Maln, and M. M. Wooifson, Acta Crystallogr., Sect. A, 29, 231 (1973). (b) All leastsquares refinements were based on the minimization of Z W ,Fo2 ~ S2Fc212 with the Individual weights w = l/a2(Fo2).(c) See paragraph at end of paper regarding supplementary material. (13) R. A. Schunn, C. J. Fritchie, Jr., and C. T. Prewitt, Inorg. Chem., 5, 892 (1966). (14) T. J. Marks and J. R. Kolb, J. Am. Chem. SOC.,97, 3397 (1975). (15) (a) B. E. Smith, B. D. James, and J. A. Dilts, J. Inorg. NucI. Chem., 38, 1973 (1976); (b) D. A. Coe, J. W. Nibler, T. H. Cook, D. Drew, and G. L. Morgan, J. Chem. Phys., 63, 4842 (1975); (c) D. A. Coe and J. W . Nibler, Spectrochim. Acta, Part A, 29, 1789 (1973). (18) J. L. Atwood, quoted in ref loa. (17) C. H. Saidarriaga-Moiina, A. Clearfield, and i. Bernai, horg. Chem., 13, 2880 (1974). (18) V. I. Kuiishov, N. G. Bokii, and Yu T. Struchkov, J. Struct. Chem., 13, 1029 (1972). (19) (a) J. L. Petersen and L. F. Dahi, J. Am. Chem. SOC.,97, 6422 (1975); (b) J. L. Petersen, D. L. Lichtenberger, R. F. Fenske, and L. F. Dahi, ibid., 97, 6433 (1975); (c) J. C. Green, M. L. H. Green, and C. K. Prout, J. Chem. Soc., Chem. Commun., 431 (1972); (d) M. L. H. Green, Pure AppI. Chem., 30, 373 (1972). (20) (a)The sum of the van der Waals radii for two hydrogen atoms is ca.2.2-2.6 A.20b For examples of short (less than 2.0 A) intramolecular H-H contacts in transition metal poiyhydrides see R. D. Wilson, F. F. Koetzle, D. W. Hart, A. Kvick, D. L. Tipton, and R. Bau, J. Am. Chem. Soc., 99, 1775 (1977). (b) F. A. Cotton and G. Wiikinson, "Advanced inorganic Chemistry", 3rd ed, interscience New York, N.Y., 1972, p 120. (21) E. R. Bernstein, W. C. Hamilton, T . A. Keiderling, W. J. Kennelly, S. J. LaPlaca, S. J. Lippard, T. J. Marks, and J. J. Mayerle, unpublishedresults at Brookhaven National Laboratory. See ref 3a for more details. (22) E. R. Bernstein, W. C. Hamilton, T. A. Keideriing, S. J. Laplaca, S. J. Lippard, and J. J. Mayerle. Inorg. Chem., 11, 3009 (1972). (23) A. Almenningen, G. Gundersen, and A. Haaland, Acta Chem. Scand., 22, 328 (1 968). (24) L. S . Barteii and E. L. Carroll, J. Chem. Phys., 42, 1135 (1965). (25) The E-h distance in BpHs determined by x-ray diffractionz5is 1.25 (2) A:
-
/
100:9
/ April 26, 1978
H. W. Smithand W. N. Lipscomb, J. Chem. Phys., 43, 1060(1965). (28) (a) It should be remembered that bonding effects distort the hydrogen 1s electron cloud from spherical symmetry and that B-H bond distances determined by x-ray diffraction are ca. 0.05-0. l A shorter than those derived from electron or neutron d i f f r a c t i ~ n . (b) ~ ~D.~S. ~ Jones ~ ~ - ~and W. N. Lipscomb, J. Chem. Phys., 51,3133 (1969). (c)T. A. Halgren, R. J. Anderson, D. S. Jones, and W. N. Lipscomb, Chem. Phys. Len., 8,547 (1971). (d) B. A. Frenz and J. A. ibers in "Transition Metal Hydrides", Vol. 1, E. L. Muetterties, Ed., Marcel Dekker, New York, N.Y., 1971, pp 35-37. (e) W. C. Hamilton and J. A. Ibers, "Hydrogen Bonding in Solids", W. A. Benjamin, New York, N.Y., 1968, Chapter 2. (27) D. S. Marynick and W. N. Lipscomb, Inorg. Chem., 11, 820 (1972). (28) (a) E. R. Peterson, Diss. Abstr., 25, 5588 (1965). The value determined by NMR second moment measurements is 1.255 A.28b (b) P. T. Ford and R. E. Richards, Discuss. faraday SOC., I 9 230 (1965). (29) (a) W. N. Lipscomb in "Boron Hydride Chemistry", E. L. Muetterties, Ed., Academic Press, New York, N.Y., 1976, Chapter 2; (b) K. Wade, "Electron Deficient Compounds', Nelson, London, 1971; (c) W. N. Lipscomb, "Boron Hydrides", W. A. Benjamin, New York, N.Y., 1963. (30) (a) W. J. Lehmann, J. F. Ditter, and i. Shapiro, J. Chem. Phys., 29, 1248 (1958); (b) R. C. Taylor and A. R. Emery, Spectrochim. Acta, 10, 419 (1958). (31) (a) G. Binsch in "Dynamic Nuclear Magnetic Resonance Spectroscopy", L. M. Jackman and F. A. Cotton, Ed., Academic Press, New York, N.Y., where T~ is the mean preexchange 1975, Chapter 3. (b) 1 / =~n6J2, ~ lifetime at coalescence and and 6, is the frequency separation between exchanging sites (32) 1/T = ( k r / h ) e - i @ / R r . (33) (a) W. G. Kiemperer in ref 31a, Chapter 2, and references cited therein: (b) W. G. Klemperer, J. Am. Chem. SOC.,94, 8360 (1972): (c) Inorg. Chem., 11, 2668 (1972); (d) J. Chem. Phys., 56, 5478 (1972). (34) (a) Both of these numbers include the identity operation. (b) For the C1 structure, the nuclear permutations which are theoretically differentiable for a single tetrahydroborate group are: (H,lHb2)(Ht2)(Hbl), (Ht2Hb2)(Ht 1)(Hbl)< (Ht2Hb1)(Htl)(Hb2), (Ht 1Hb 1)(Ht2)(b2), (Ht 1Ht2Hbl )(Hb2), (HtlHb1Ht2)(Hb2), (HtlHb2Hbl )(Ht2). (Htl Hb 1H$)(Ht2), (Ht 1Ht2Hb2)(Hb1), (Ht 1H$Ht2)(Hb 1), (HtZHt,1H$)(Htl), (Ht2Hb2Hb1)(Htl), (Ht1Ht2Hb 1Hb2). (HtHb2Hb 1Ht2), (Ht1Ht2Hb2Hb1), ( l i t 1Hb 1Hb2Ht2), (Ht 1H$)(Ht2Hb 1), (HtlHb1)(Ht2Hb2), (Ht1Hb2h2Hb I), (Ht1Hb 1Ht2Hb2). (Htl Ht2)(Hb2)(Hb1), (Ht1Ht2)(Hb2Hbl),(Ht!)(Ht2)(Hb2Hbl), and (Htl)(Ht2)(Hbz)(Hbl). (35) Solid state NMR studies are in progress. (36) i. Chuang, T. J. Marks, W. J. Kenneliy, and J. R. Koib, J. Am. Chem. SOC., 99, 7539 (1977). (37) V. Plat0 and K. Hedberg, Inorg. Chem., 10, 590 (1971). (38) A monodentate coordination geometry has recently been reported: J. L. Atwood, R. D. Rogers, C. Kutal, and P. A. Grutsch, J. Chem. SOC.,Chem. Commun., 593 (1977).
Reduction of Carbon Monoxide Promoted by Alkyl and Hydride Derivatives of Permethylzirconocene Juan M. Manriquez, Donald R. McAlister, Robert D. Sanner, and John E. Bercaw*' Contribution No. 5679 from the A . A . Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91 125. Received October 6 , I977
Abstract: Bis(pentamethylcyclopentadienyl)dihydridozirconium(IV), (q5-C5Me5)2ZrH2 (2) is prepared by the reaction of H2 with ((q5-C5Me5)2ZrN2]2Nz (1). 2 forms unstable adducts with PF3 and CO at -80 'C. The carbonyl adduct (q5-C5Me5)2ZrHz(CO) yields ((05-C5Me5)2ZrH)2(OCH=CHO) and/or (q5-C5Me5)2ZrH(OCH3), depending on reaction
*
conditions. Carbonylation of (q5-C5Me5)2Zr(CH3)2, obtained from (q5-C5Me&ZrC12 and methyllithium, yields successively (q5-C Me5 2Zr CHj)(CH$O) and (q5-C5Me5)2tr(O(CH3)C=C(CH3)O). The zirconacyclopentane complex (q5-C5Me5)2 r(CH2(CH2)2 H2) (10) is prepared from 1 and ethylene. Carbonylation of 10 affords (q5-C5Me5)2Zr(H)(OC=CH(CH2)2dH2). Treatment of 2 with isobutylene yields (q5-CsMe5)2Zr(H)(CH2CHMe2) (13), which undergoes a (15). The results of I3C and deuterium labeling studies reaction with CO to form (q5-C5Me5)2Zr(H)(OCH=CHCHMe2) indicate that the conversion of 13 to 15 is mediated by (q5-C5Me5)2Zr(H)(Me2CHCH*CO).The observed patterns for these reactions of alkyl and hydride derivatives of zirconium with CO are attributed to carbenoid character of the carbonyl carbon resulting from an unusual "side-on" coordination of acyl and formyl groups.
Introduction The development of homogeneous catalysts for selective conversion of C O and Hz to alkanes or alcohols is a problem of growing interest. Homogeneous systems thus far reported to catalyze the reduction of C O by H2 include the Rh-based ethylene glycol synthesis,2 methanation promoted by Os3(C0)12 or I r 4 ( C 0 ) 1 2 , ~and most recently the catalytic 0002-7863/78/ 1500-2716$01.00/0
production of methane, ethane, propane, and isobutane by I r 4 ( c o ) , 2 in molten NaC1.2A1C13.4 We recently reported that H2 stoichiometrically reduces ligated C O in certain carbonyl compounds of z i r c o n i ~ m : ~
-
(.r15-C5Me5)2Zr(C0)2
+ 2H2
110 oc
+
(.rl5-C~Mes)2Zr(H)(oCH3) C O
0 1978 American Chemical Society
(1)
Bercaw et al.
/ Reduction of CO Promoted by Derivatives of Permethylzirconocene
2717
Table I. Proton Nuclear Magnetic Resonance Data
Compd
Solvent
NMR, 6
Benzened6
S
2.02 7.46 1.77
dq
0.55 ( ' J ~ 3 l p = 108 Hz,
S
S
Toluened8 -50 OC
3 J ~ =~21.5 9 ~ Hz) 1.84 S 1.07 1.07 ('J~13c= 25.1 Hz) d S 1.94 S 6.55 s 5.73 IO-line AA'XX' pattern (IJH13C = 177, 'JI3Cl3C = 99, 'J~13c= 7.5, 3J" = 9 HZ) S 1.94 S 6.83 IO-line AA'XX' pattern ( I J H l 3 C = 180.3, IJl3CI3C = 100, 'JHIIC = 7, 3J" = 10 HZ)" S 1.78 S -0.62 1.65 S
s
ToIuene-d8 -64 'C {(q5-C5Me5)2ZrH]2(OCHCHO)(5)
Toluene-d8
((q5-C5Me5)2ZrIJ2(OCHCHO)( 6 )
Benzene-d6
Benzene-& Benzene-d6
s
Benzened6 Benzene-d6
s
2.32 1.86 1.91 1.82
rn
0.50
S
rn
Benzene-d6
S
S
rn rn
(q5-C5Me5)2Zr(I)(OC=CHCH2CH2CH2) (12)
Benzene-d6
S
rn rn Benzene-d6
(q5-CsMe5)2Zr(H)(CH2CHMe2) (13a)
S S
d d
(q5-C5Me5)2Zr(D)(CH2CDMe2) (13b)
Benzene-d6
(v5-C5Me5)2Zr(H)(Me2CHCH2CO) (14a)
Toluened6 -50 OC
S
s S S
d d
(qs-C5Me5)2Zr(H)(Me2CHCH213CO) (14c)
Toluene-d6 -40 "C Toluened6 -40 "C
(q5-C5Me5)2Zr(H)(OCH=CHCHMe2) (15a)
Benzene-d6
(q5-C5Me5)2Zr(D)(Me2CDCHlCO) (14b)
S S
d d dd s S
OCH=CHCH(CH3)2 OCH=C H CH(C H3)2
(q5-C5Me5)2Zr(H)(OCD=CHCDMe2) (15b)
Benzene-ds
($-CsMe5)2Zr(H)(O13CH=CHMe2)
Toluened6
(1%)
(C H=C HCH (CH3)2 OCD=CHCD(CH3)2 (CD-CHCD(CH3)z [CdcH3)d ZrH OCH=C HC H(C H 3) 2 OCH=C HC H (CH3 ) 2 OCH=CHCH(CH&
See note 34.
-0.05
S S
d
dd d S
S S
S
dd
rn d-
1.95 1.97 6.07 4.42 2.0-2.5 1.94 4.55 2.0-2.5 1.93 6.43 -0.04 (3JH_H= 7 HZ 1.00 ( 3 J H - H = 6.5 HZ) -0.04 1 .oo
1.82 3.66
Journal of the American Chemical Society
2718
+ 4H2
25 OC --j
2(q5-C5Me5)2Zr(H)(OCH3)
+ N2
While not (yet) catalytic, this system provides an opportunity to examine certain features of the reduction mechanism, in particular the presumed migratory insertion of C O into a transition metal hydride bond. We have therefore extended our investigations of these reactions and have examined the reactivity of hydride and alkyl derivatives of the types (q5C~Mes)zZrH2,(q5-C5Me5)2Zr(H)(R), and (q5-C5Me5)2ZrR2 toward CO. Herein we report the results of those studies.
Results 1. Reactions of (q5-CsMes)zZrHzwith CO. By virtue of the lability of its ligated N Z { (q5-C5Me5)2ZrN2]2N~6%7 (1) serves as a convenient starting material for a variety of derivatives of bis(pentamethylcyclopentadieny1)zirconium. Treatment of 1withHz at 0 OC intoluene or hexane a f f o r d s ( ~ ~ - C 5 M e 5 ) ~ ZrH2 ( 2 ) in quantitative yield:
-
((V5-C5Me5)2ZrN2)2N2 + 2H2
/H
\
100:9
/ April 26, I978
CO
H
4
Whereas residual C O may be removed at -78 " C without significant decomposition -of 4, the C O ligand is somewhat labile. 1 3 C 0 labeling studies indicate 0.21 mol of I3CO exchanged per mol of 4 after 30 min at -78 OC @(CO) = 0.5 atm): (q5-CsMe5)2ZrH2(12CO) 1 3 C 0 @ (q5-C5Me5)2ZrHz(l3C0)
+
+ I2C0
(5)
When solutions of 4 are allowed to warm above -50 OC, ((q5-C5Me5)2ZrH)2(0CH=CHO) ( 5 ) is obtained in nearly quantitative yield. The structure of this rather unexpected H
H
2(v5-C5Me5)2ZrH2
+ 3N2
5
(3)
Unlike polymeric ((q5-C5H5)2ZrH2),,8,9 pale yellow 2 is very soluble in hydrocarbons. Its molecular weight, analytical data (see Experimental Section), N M R spectrum (Table I), and IR spectrum (v(Zr-H) 1555 cm-'; v(Zr-D) 1100 cm-l) are entirely in accord with a monomeric, pseudotetrahedral structure analogous to (q5-C5Me5)2ZrC12. The low-field chemical shift observed for the hydride hydrogen atoms of 2 (6 7.46) is in direct contrast to the characteristic high-field resonances for group 5-8 transition metal hydrides, but intermediate to the hydride resonances for (q5-C5Me5)2TiH2(6 0.28) and (q5-C5Mes)2HfX2 (6 15.6). (q5-CsMe5)2ZrH2(2) is formally a 16-electron complex and thus adds certain donor molecules. Thus 2 absorbs PF3 at -80 " C in toluene to yield the unstable, 18-electron complex (v5C5Me5)2ZrHz(PF3) (3). On the basis of its IH N M R spectrum at -50 OC (Table I), the structure of 3 appears to be analogous to (q5-C5H5)2TaH3Io with PF3 occupying the central equatorial position mutually cis to both hydride ligands:
/H
(+C5Me5)zZr-PF3
\
" .J
H
Interestingly P(OCH3)3, P(CsH5)3, and P(CH3)3 do not appear to form adducts analogous to 3; the IH N M R spectra of solutions of 2 containing 2-10 molar equiv of these ligands give no indication of additional species a t 25 OC. 2 does, however, absorb C O (0.97 mol/mol 2) in toluene at -78 " C to generate the carbonyl hydride (v5-C~Me5)2ZrH2(CO)(4). Although 4 is not sufficiently stable for its isolation (see below), it has been characterized in solution at low temperatures. Thus 4 reacts with excess HC1 at -78 O C to yield (q5-CsMe5)zZrC12, H2, and C O in accord with the equation (175-C5Me5)2ZrH2(CO) 2HC1- (q5-CsMe5)2ZrC12
+
( +C5Me&Zr-
(2)
/
+ 2H2 + C O
compound is supported by analytical data (see Experimental Section), by its infrared spectrum (v(Zr-H) 1580 cm-l, v(Zr-D) 1130 cm-'; v(C-0) 1205 cm-', v(13C-O) 1180 cm-I), and most characteristically by ' H and 13CN M R data prepared from 2 for ((q5-C5Me5)2ZrH)2(013CH=13CHO), and I3CO: an AA'XX' pattern" for the H and 13Catoms of the (-0I3CH=l3CHO-) bridge (Table I). Furthermore, 5 reacts smoothly with methyl iodide to afford methane and ((q5-C5Me5)2ZrI)2(0CH=CHO) (6). The IR spectrum (v(C-0) 1195 cm-I, v(13C-O) 1175 cm-l) and 'H and I3C N M R data for 6 (Table I) indicate a structure analogous to that for 5. The preliminary results of an x-ray structure determination for 6 are fully in accord with that suggested above, although some difficulties in final refinement have been encountered.12 {(v5-C5Me5)zZrH)2(OCH=CHO) (5) is also obtained when (q5-CsMe&ZrH2(CO) (4) is warmed under an atmosphere of H2. When 4 is allowed to warm in the presence of both H2 and (v5-C5Me5)2ZrH2 (2), however, both (q5C5Me5)2Zr(H)(OCH3) (16) and 5 are formed; 2 is quantitatively r e ~ o v e r e dThe . ~ relative yields of 5 and 16 depend on the amount of 2 which is added. Thus with a 1.29 molar ratio of 2:4,16 and 5 are obtained in a 12:l molar ratio; whereas with 2:4 = 0.22, 16 and 5 are formed in a 0.74:l molar ratio. In addition we find that slow diffusion of C O into an N2-blanketed solution of (q5-C5Me5)2ZrH2 (2) at 25 " C (conditions for which there is continuously a high ratio of 2:4) affords only (q5-C5Me5)2Zr(H)(OCH3)(no detectable 5 ) and a transient dark red color characteristic of {(q5-CsMe5)2ZrN2)2N2 and/or {(q5-C~Me5)2Zr(CO)J2N2.6,7 After several hours at 25 'C the final solution contains a 1:l mixture of (q5-C5Me5)2Zr(H)(OCH3) and (q5-C5Me5)2Zr(C0)2: 2(q5-C5Me5)2ZrH2
+ 3CO diffusion (v5-C5Me5)2Zr(H)(OCH3) + (v5-CsMe5)2Zr(C0)2
(4)
The IH N M R spectrum for 4 (Table I) is consistent with a - ~ structure analogous to 3, and the doublet with 2 J ~ 3 =~ 25 Hz observed for the hydride resonance for 4-(l3CO) is only consistent with a two-bond coupling, thus indicating a carbon-bonded carbonyl, Le.,
(6)
2. Reactions, of (q5-CsMes)zZr(CH3)2and (q5-C5Me5)2Zr(CHz(CH2)zCHz)with CO. In order to provide a basis for understanding the apparent migratory insertion of C O into a Zr-H bond for (q5-C5Me5)2ZrH2(CO), we have investigated the reactivity of zirconium alkyls toward CO. The preparation of (v5-C5Me5)2Zr(CH3)2(7) follows that previously described for the parent compound (q5-C5H~)2Zr(CH3)2:l3
Bercaw et al.
/ Reduction of CO Promoted by Derivatives of Permethylzirconocene
(q5-C5Me5)2ZrC12 2CH3Li
+
-
(05-C5Me5)2Zr(CH3)2
+ 2LiCI
1
(7)
The latter has been reported to add CO reversibly affording (v5-C5H5)2Zr(CH3)(CH3CO),which was structurally characterized by x-ray diffraction methods.I4 Similarly 7 reacts with CO (1 atm) in benzene solution according to the equation (V5-C5Me5)2Zr(CH3)2
+ CO + (sS-C5Me5)2Zr(CH3)(CH3CO)
(8)
Isolation of (q5-C5Me5)2Zr(CH3)(CH3CO)(8) has not been possible owing to its lability and high solubility; however, the similarity of its 'H N M R spectrum (Table I) and infrared spectrum (v(C-0) 1537 cm-' ( T H F solution)) to those for (q5-C~H5)2Zr(CH3)(CH3CO)( [T$CSH~] singlet, 6 5.35 (10 H ) , C H 3 C 0 singlet 6 2.41 (3 H ) , ZrCH3 singlet, 6 0.45 (3 H); u(C-0) 1545 cm-' (Nujol mull)) leaves little doubt that the two acyl methyl compounds a r e isostructural. 8 reacts further with CO a t 70 OC in benzene over a eriod of several hours to afford only (q5-C5Me5)2 r(O(CH3)C=C(CH,)O) (9).This structure is supported by IH N M R
2--e-
9
(Table I), analytical, mass spectral, and infrared data (see Experimental Section), and by the fact that 9 may be prepared independently by reaction of ((q5-C5Me5)2ZrN2)2N2 with biacetyl (eq l o ) . In contrast to the quantitative conversion of 0
+
{($-C5Mej)2ZrN212N2
-
2719
0
II I1
-
+
(~S-C5Mej)2SIICH2(CH,),CHz~ 2H2
(qjC5MeJ2ZrH2 + C&
(v5-C5Me5)2Zr(CH2(CH2)*CH2) absorbs CO (1 .O mol/ mol 10) rapidly a t 25 O C to yield a white crystalline product (11) together with a small amount (-5%) of (v5-C5Me~)2Zr(CO)2. 11 may also be obtained by prolonged photolysis (A >480 nm)of toluene solutions of (v5-CsMe5)2Zr(C0)2under ethylene. On the basis of its physical properties and its chemical reactivity, 11 appears to have the structure shown. Thus the
'
H
+ 3N2
2(1"C5Me,),~r(O(CH,)C~(CH,)b)
W
11
'H N M R spectrum of 11 (benzene-ds) exhibits a singlet at 6 1.97 (30 H ) attributable to the methyl groups of the [$C5(CH3)5] rings, a singlet a t 6 6.07 (1 H ) due to the Zr-H moiety, a multiplet at 6 4.42 (1 H ) due to the vinylic hydrogen, and a broad multiplet in the region 6 2.0-2.5 (6 H ) attributable to the methylene hydrogens of the cyclopentene ring. The IH N M R spectrum of 11 prepared from 10 and I3CO shows no large splitting of any of these resonances, indicating that no hydrogen atoms are bonded directly to the I3C atom in 11. Its infrared spectrum exhibits characteristic bands a t 1628 (u(C=C)), 1275 (v(C-0)), and 1538 cm-' (v(Zr-H)), the first two bands shifting to 1595 and 1250 cm-I for 11 prepared from 10 and 1 3 C 0 . Furthermore, 11 reacts smooth1 with methyl iodide to yield (q5-C5Me5)2Zr(I)(& 2CH2) (12) with the evolution of CH4 (0.94 mol/mol 11) according to eq 15.As expected, infrared and 'H N M R spectra
-
-
($C5Me5XZr(H)(OC= CH(CH,),(CH,)
2CHJC--OCH3
+
CHJ
m +
(~5-C5Me5kZ~I)(OC=CH(CH2)2CH2)CH, (15)
(10)
8 to 9, (v5-C5H5)2Zr(CH3)(CH$O) undergoes a complicated series of reactions with C O a t 70 OC (benzene) leading to several products. ((q5-C5Me5)2ZrN2)2N2absorbs ethylene (4.2 mol/mol 1) a t 25 OC in toluene solution with evolution of N2 to afford (q5-CsMe5)2Zr(CH2(CH2)26H2)(10) in nearly quantitative yield (eq 11). 10 is also obtained from (v5-C5Me5)2ZrH2 and
(Table I) for 12 are nearly identical with those for 11 with the notable absence of the I R band a t 1538 cm-' and the N M R resonance at 6 6.07 attributed to the Zr-H moiety of 11. Treatment of 11 with HCI in diethyl ether affords cyclopentanone in moderate yields (55% GLC).
-
(g,i-CjMej),Zr(H)(OC=CH(CH,)2CH,)
+ WCI 0
I(.rl.-C5Med2ZrN2~,N1 + 4C,H,
-
rn
2(qj~jMe5)LZr(CHXCHz),CH1)+ 3N,
(14)
----t
(q5.C,Me,)J2ZrC1,
(11)
+
H2 +
A u
(16)
3. Reaction of (v5-C5Me&Zr(H)(CH2CHMe2)with CO. Benzene solutions of (q5-CsMe5)2ZrH2 (2) react with excess isobutylene over a period of several minutes a t room temper( V ~ - C ~ M ~ ~3C2H4 )~Z~H~ ature to afford (q5-C5Me5)2Zr(H)(CH2CHMe2) (13a) in nearly quantitative yield ( N M R ) . I (oi.C,Me-,)?Zr(CHi(CHi),CHL) C2H, (12) (q5-C5Me5)2ZrH2 CH2=CMe2 'H N M R (Table I) and infrared data (see Experimental (v5-C5Me5)2Zr(H)(CH2CHMe2) (17) Section) are most consistent with a structure containing the zirconacyclopentane moiety. Furthermore, 10 reacts with 2 The contrast between the reactivity of (v5-C5Me5)2ZrH2 with isobutylene and that with ethylene (eq 12) may be attributed to steric factors. The stability of 13 is indeed remarkable: benzene solutions are stable for hours a t 50 "C, even in the presence of excess i ~ o b u t y l e n e .When '~ treated with ethylene 10 a t 25O, however, 13 is smoothly converted to 10 with release equiv of HCl according to eq 13 and with excess H2 (eq 14) to of isobutane (eq 18). yield predominantly butane. (03CgMe~)1Zr(H)(CHLCHMe2) %,HI I (a5C,Me,),Zr(CH,(CH,),CH,) + 2HC1
ethylene a t 25 OC according to the equation
+
-
+
-+
+
(oj-C5Me5)?ZrC1,
+
C4Ro
(13)
Journal of the American Chemical Society
2720
/
100:9
/ April 26, 1978
(q5-C5Me5)2Zr(D)(CH2CDMe2) (13b) may be prepared according to the equations
+
((75-C5Me5)2ZrN2)2N2 2D2 2(q5-CsMe5)2ZrD2
+
+ 3N2
(19)
with C O positioned within the five-membered ring must be highly unfavorable. Subsequent migratory insertion of C O into Zr-alkyl or (20) Zr-H bonds occurs with remarkable facility in all cases. The This sequence must be carried out below 5 "C to avoid deuteresults of the study of the reaction of (q5-C5Me5)2Zr(H)rium exchange with methyl hydrogens of the pentamethylcy(CH2CHMe2) with 1 3 C 0 establish that alkyl migration is clopentadienyl groups for (v5-C5Me5)2ZrD2.l6 The addition favored over hydride migration for this system. Indeed, initial of isobutylene appears to be entirely regiospecific, since 'H quantitative conversion of ($-CsMe5)2ZrH2 to (q5-C5Me&N M R spectra for 13b (Table I) indicate no scrambling (
