Monomeric Alkyl and Hydride Derivatives of Zinc Supported by Poly

Organometallics 1995, 14, 274-288

274

Monomeric Alkyl and Hydride Derivatives of Zinc Supported by Poly(pyrazoly1)hydroborato Ligation: Synthetic, Structural, and Reactivity Studies Adrian Looney, Runyu Han, Ian B. Gorrell, Mark Cornebise, Keum Yoon, and Gerard Parkin* Department of Chemistry, Columbia University, New York, New York 10027

Arnold L. Rheingold Department of Chemistry, University of Delaware, Newark, Delaware 1971 6 Received September 1, 1994@

A series of monomeric four-coordinate monoalkyl zinc complexes [TpBUtlZnR ([TpButl= tris(3-tert-butylpyrazolyl)hydroborato;R = Me, Et) and [TpMe21ZnMe([TpMezl= tris(3,5dimethylpyrazoly1)hydroborato) has been prepared by metathesis of RzZn with T1[TpButland T1[TpMe2],respectively, while the three-coordinate zinc alkyl derivatives [BpBUtlZnR([BpButl = bis(3-tert-butylpyrazolyl)hydroborato;R = Me, Et, But) have been synthesized by the reactions of RzZn with T1[BpBUt].The monomeric zinc hydride derivative [TpBUtlZnHhas also been prepared by the reaction of ZnHz with T1[TpBUtl.The reactivities of [TpButlZnH and [TpBUt]ZnR toward a variety of substrates have been investigated, giving rise to a series of derivatives [TpBUtlZnX (X = OzCH, OZCMe, C2Ph, SH, OSiMe3, C1, Br, I). The Zn-C bonds of the three-coordinate complexes [BpBut]ZnR(R = Me, Et) are cleaved by HzO to give the and by MeCOzH to give [BpBUtlZn(q2-Od2Me). Mezcyclic hydroxo trimer { [BpBUt]Zngl-OH)}3 CO, MeCHO, and (CH20), insert into the B-H bond of [BpButlZnR,in preference to the Zn-R bond, to give the complexes {HB(OR')(3-Butpz)z}ZnR( R = Me, Et, P$). The molecular structures of [TpMezlZnMe,[TpMezlzZn,[TpButlZnH,[TpBUtlZn(yl-O~CMe), [TpButlZnNCS,[BpButllZnBut, and { [BpBut]Zngl-OH)}3have been determined by X-ray diffraction. [TpMezlZnMeis orthorhombic, Pcmn (No. 62), a = 7.831(2) b = 13.376(4) c = 18.877(4) V = 1977(1) Hi3, and 2 = 4. [TpMezlzZnis triclinic, Pi (No. 2), a = 8.806(1) b = 10.195(2) c = 10.800(2) a = 63.46(2)", ,!? = 85.11(2)", y = 79.63(1)", V = 853(1) and 2 = 1. [TpBUtlZnHis monoclinic, P n (No. 7), a = 8.262(1) b = 15.465(2 c = 9.696(2) ,!? = 100.76(2)", V = 1217(1) A3, and 2 = 2. [TpBut]Zn(yl-OzCMe)is orthorhombic, P2lcn (No. 331, a = 10.433(1) b = 15.832(2) c = 19.292(3) A, V = 3186(1)Hi3, and 2 = 4. [TpBUtlZnNCS is monoclinic, P21h (No. 14), a = 9.703(2) b = 17.001(4) c = 16.582(3) ,!? = 95.08(1)", V = 2725(1) Hi3, and 2 = 4. [BpBUt]ZnButis monoclinic, P21/n (No. 14), a = 14.912(7) b = 8.556(2) c = 18.482(5) ?! , = 112.86(3)", V = 2173(2) A3, and 2 = 4. {[BpButlZngl-OH)}~ is orthorhombic, Pc2ln (No. 33), a = 12.302(2) b = 20.057(6) c = 22.110(2) V = 5455(2) Hi3, and Z = 4.

A,

A,

A,

A

A,

A,

A,

A,

A,

A,

A,

Introduction Organozinc complexes are presently used extensively in both organic and organometallic syntheses.lJ In particular, organozinc reagents offer valuable alternatives to the corresponding magnesium and lithium reagents in terms of both their reactivity and selectivity. However, in contrast t o dialkylmagnesium reagents, in which the Mg centers are typically four-coordinate and tetrahedral (both in the solid state and as solvated derivatives in solution), dialkylzinc complexes exist as

A k3, A,

A,

A

A,

A,

A,

A,

A,

monomeric two-coordinate linear molecules. In view of the different structures of dialkylmagnesium and dialkylzinc complexes, it is of some interest to compare the reactivity of isostructural organomagnesium and organozinc complexes. Such studies would thereby allow a comparison of the intrinsic reactivity of Zn-C and Mg-C bonds. We have recently described the use of the sterically-demanding tris(3-tert-butylpyrazoly1)hydroborato ligand, [TpBUtl,3s4 to provide a well-defined coordination environment for a series of four-coordinate monomeric magnesium alkyl derivatives [ T P ~ ~ ~ I M ~ R . ~

~

Abstract published in Advance ACS Abstracts, November 1,1994. (1)(a) Boersma, J. In Comprehensive Organometallic Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon Press: Oxford, U.K., 1982;Vol. 2,pp 823-862. (b) Coates, G. E.; Green, M. L. H.; Wade, K. Organometallic Compounds. Volume I: The Main Group Elements, 3rd ed.; Methuen: London, 1967. (c) Elschenbroich, C.;Salzer, A. Organometallics: A Concise Introduction, 2nd ed.; VCH: New York, 1992. (2)(a) Miginiac, L. In The Chemistry of the Metal-Carbon Bond; Hartley, F. R., Patai, S., Eds.; Wiley: New York, 1985;Vol. 3,Chapter 2. (b) Furukawa, J.;Kawabata, N. Adu. Organomet. Chem. 1974,12, 83-134. (c) Erdik, E. Tetrahedron 1992,48,9577-9648. @

0276-7333/95/2314-0274$09.0OI0

(3)Trofimenko, S.;Calabrese, J. C.; Thompson, J. S. Inorg. Chem. 1987,26,1507-1514. (4)The nomenclature adopted here for tris(pyrazoly1)hydroborato ligands is based on that described by Trofimenko. Thus, the tris(pyrazoly1)hydroborato ligands are represented by the abbrevation Tp, with the 3-and 5-alkyl substituents listed, respectively, as superscripts. Similarly, the bis(pyrazoly1)hydroborato ligands are represented by the abbrevation Bp. See: Trofimenko, S. Chem. Rev. 1998,93,943-980. ( 5 ) (a)Han, R.; Looney, A.; Parkin, G. J.Am. Chem. SOC.1989,111, 1990,112, 7276-7278. (b) Han, R.;Parkin, G. J. Am. Chem. SOC. 3662-3663. (c) Han, R.;Parkin, G. Organometallics 1991,10,10101020. (d) Han, R.; Parkin, G. J.Am. Chem. SOC. 1992,114,748-757.

0 1995 American Chemical Society

Alkyl and Hydride Derivatives of Zinc

Organometallics, Vol. 14, No. 1,1995 275

Scheme 1

I

H

-[TIR] (R = Me, Et)

Me2Zn -(TIMe]

-

Here we report that the tris(3-tert-butylpyrazoly1)hydroborato ligand also permits the isolation of the correspondingmonomeric zinc alkyl and hydride derivatives [TpBUtlZnR and [TpBUtlZnH.Furthermore, we also describe the use of the bis(3-tert-butylpyrazoly1)hydroborato ligand, [BpBUtl,3 to stabilize monomeric threecoordinate zinc alkyls [BpBUtlZnR.Some of this work has been previously communicated.6

Results and Discussion Syntheses, Characterization, and Reactivity of the Four-CoordinateZinc Alkyl Complexes [TpBu'+ ZnR and [TpMealZnR.Our recent studies have demonstrated that the sterically demanding t i s (3-tertbutylpyrazoly1)hydroborato ligand, [TpButl,3provides a well-defined coordination environment for investigating the chemistry of four-coordinate alkyl complexes of beryllium and magne~ium.~~' The corresponding zinc alkyl derivatives [TpBUtlZnR (R = Me, Et) may also be readily prepared by metathesis of RzZn with Tl[TpButl (Scheme 1). The reaction is accompanied by the deposition of Tl due to decomposition of unstable [TlRl,thereby providing an effective driving force for the reaction.* In addition to the bulky tris(3-tert-butylpyrazoly1)hydroborat0 ligand, [TpButl,the less sterically demanding tris(3,5-dimethyl)pyrazolylhydroboratoligand, [TpM*l,may be used to prepare the methyl derivative [TpMezlZnMe (Scheme l),of which the magnesium analogue [TpMez]MgMe has been previously s y n t h e s i ~ e d . ~ , ~ The complexes [TpBUt]ZnRrepresent the first examples of zinc alkyl derivatives stabilized by an v3-tris(pyrazoly1)hydroboratoligand.6a Vahrenkamp has also utilized the tris(3,5-diphenylpyrazolyl)hydroboratoand tris(3-arylpyrazoly1)hydroborato (aryl = phenyl, tolyl, anisyl) ligands to synthesize the complexes [TpPh21ZnR and [TpATlZnR(R = Me, Et, But, Ph).l0 Furthermore, the cadmium analogues [TpBUtICdR1l and [TpMez1CdRl2 have also been recently prepared using a similar approach. (6) (a) Gorrell, I. B.; Looney, A.; Parkin, G. J . Chem. Soc., Chem. Commun. 1990, 220-222. (b) Gorrell, I. B.; Looney, A.; Parkin, G.; Rheingold, A. L. J . Am. Chem. SOC.1990, 112, 4068-4069. (c) Han, R.; Gorrell, I. B.; Looney, A. G.; Parkin, G. J. Chem. SOC.,Chem. Commun. 1991, 717-719. (7) Han, R.; Parkin, G. Inorg. Chem. lSS3,32, 4968-4970. (8)Gilman, H.; Jones, R. G. J . Am. Chem. Soc. 1946.68.517-520. (9) Han, R.; Parkin, G. J.Organomet. Chem. 1990,393,'C43-C46. (10) (a) Alsfasser, R.; Powell, A. K.; Vahrenkamp, H. Angew. Chem., Int. Ed. Engl. 1990, 29, 898-899. (b) Alsfasser, R.; Powell, A. K.; Trofimenko, S.;Vahrenkamp, H. Chem. Ber. 1993,126, 685-694. (11) Looney, A.; Saleh, A.; Zhang, Y.; Parkin, G. Inorg. Chem. 1994, 33, 1158-1164. (12) Reger, D. L.; Mason, S. S. Organometallics 1993, 12, 26002603.

Figure 1. Molecular structure of [TpMezIZnMe. Table 1. Selected Bond Lengths (A) and Angles (deg) for [TpMQIZnMe Zn-C(l) Zn-N(22) N(21)-N(22) B-N(21)

1.981(8) 2.056(4) 1.364(6) 1.545(7)

C(l)-Zn-N(12) N( 12)-Zn-N(22)

123.6(4) 90.5(2)

Zn-N(12) N(l1)-N(12) B-N(11) C(l)-Zn-N(22) N(22)-Zn-N(22')

2.048(6) 1.377(8) 1.540(12) 125.8(2) 89.9(2)

Table 2. Comparison of Bond Lengths and Angles for [TpWlMMe Complexes d(M-C)/A [TpM%]ZnMe [TpPh]ZnMe [TpBu']Znh4e [TpB"']MgMe

1.981(8) 1.950(4) 1.971(4) 2.1 18(11)

d@i-N)/k 2.053[10] 2.108[30] 2.109[10] 2.135[101

N-M-C/dep 125[2] 126[2] 125[2] 125[3]

ref

this work b c

d

The number in parentheses indicates the range of bond lengths and angles. Alsfasser, R.; Powell, A. K.; Trofimenko, S.; Vahrenkamp, H. Chem. Ber. 1993,126,685-694. Yoon, K.; Parkin, G. J . Am. Chem. SOC. 1991, 113, 8414-8418. dHan, R.; Parkin, G. Organometallics 1991, 10, 1010-1020.

The molecular structures of the methyl derivatives [TpBUt1ZnMeGaJ3 and [TpMe21ZnMe(Figure 1)have been determined by X-ray diffraction, confirming the v3coordination mode of the tris(pyrazoly1)hydroborato ligands. Selected bond lengths and angles for [TpMezlZnMe are presented in Table 1. The zinc centers are appropriately described as trigonally distorted tetrahedral, with average C-Zn-N and N-Zn-N bond angles of ca. 125 and go", respectively. The molecular structure of the derivative [TpPhlZnMehas also been determined by Vahrenkamp, and average bond lengths and angles for these compounds are compared in Table 2. Examination of Table 2 indicates the trend that the average Zn-N bond length increases very slightly as the steric bulk of the tris(pyrazoly1)hydroborato ligand increases.14 Thus, the average Zn-N bond length of 2.053[10] A in [TpMez]ZnMeincreases to 2.109[10] A in [TpBUtlZnMe.The Zn-C bond lengths for the complexes [1.971(4)AI [TpMezlZnMe[1.981(8)AI and [TpBUtlZnMe are close to, but slightly less than, the sum of the covalent radii of Zn and C (2.02 A),15 and are also in the range of known Zn-C bond lengths. For example, (13) Yoon, K.; Parkin, G. J . A m . Chem. SOC.1991,113,8414-8418. (14) The cone angles of tris(pyrazoly1)hydroborato ligand increases from [TpM@l (224")t o [TpButl(244"). See ref 3. (15) Pauling, L. TheNature ofThe ChemicalBond, 3rd ed.; Cornel1 University Press: Ithaca, NY,1960; p 256.

276 Organometallics, Vol. 14, No. 1, 1995

Looney et al.

Table 3. Terminal Zn-C Bond Lengths for RzZn Complexes RzZn

Scheme 2 ref

1.930(2) 1.950(2) 1.952(3) 1.937(2) 1.97[2] 1.946[5] 1.950[1] 1.969(8)

a a a b

1.982(2) 1.974(3) 1.980(4) 1.968[3] 1.983(7)

rPhCCH

d(zn-C)/A

Xp, -RX

[TpBU']Zn-C=C-Ph

[TpBu']Zn-X

C

d e

f g

h i i

\

Wut ,\

R'I

[TpBU']Zn-l

(R' = CH3, CH2Ph)

i

Almenningen, A.; Helgaker, T. U.;Haaland, A,; Samdal, S. Acta Chem. S c a d . 1982, A36, 159-156. Westerhausen, M.; Rademacher, B. J . Organomet. Chem. 1993,443,25-33. Gais, H.-J.; Biilow, G.; Raabe, G. J . Am. Chem. SOC. 1993, 115, 7215-7218. dMarkies, P. R.; Schat, G.; Akkerman, 0. S.; Bickelhaupt, F.; Smeets, W. J. J.; Spek, A. L. Organometallics 1990, 9, 2243-2247. eBrooker, S.; Bertel, N.; Stalke, D.; Noltemeyer, M.; Roesky, H. W.; Sheldrick, G. M.; Edelmann, F. T. Organometallics 1992, 11, 192-195.fEmst, R. D.; Freeman, J. W.; Swepston, P. N.; Wilson, D. R. J . Organomet. Chem. 1991, 402, 17-25. 8 Westerhausen, M.; Rademacher, B.; Poll, W. J. Organomet. Chem. 1991, 421, 175-188. Al-Juaid, S. S.;Eaborn, C.; Habtemariam, A.; Hitchcock, P. B.; Smith,J. D. J . Organomet. Chem. 1992,437,41-45. Aigbirhio, F. I.; Al-Juaid, S. S.; Eaborn, C.; Habtemariam, A.; Hitchcock, P. B.; Smith, J. D. J . Organomet. Chem. 1991, 405, 149-160. j Cited in ref i. a

dialkylzinc complexes typically exhibit Zn-C bond lengths in the range 1.9-2.0 A, as summarized in Table 3. The Zn-C bond lengths in the complexes [TpR*RIZnMe are also similar t o those in the zinc ethyl derivatives (EtZn)2(p-C20H28N4)(1.978[41 Alls and [(EtZn)2{2N(SiMes)CsH3N-6-Me}]z (1.95[21 Moreover, the four-coordinate dialkyl derivatives Me2Zn[(CH2NMe)& [1.987(6)Alla and Zn[(CH2)3NMe212 11.9846) A, X-ray; 1.991(6) A, electron diffraction1lg also have similar Zn-C bond lengths. It is also worth notin that the Zn-C bond length of [TpBut]ZnMe[1.971(4) 113 listed in Table 2 is longer than the value cited in the original report [1.890(10) It is possible that the shorter value, which is anomalous compared t o other Zn-CH3 bond lengths (videsupra), is an artifact due to compositional disorder with an impurity (possibly [TpBUtlZnOH), since it is well documented that trace impurities may artificially influence apparent bond lengths as determined by single crystal X-ray diffraction.20 The Zn-C bond length in [TpBUtlZnMe[1.971(4) AI may also be compared with the Mg-C bond length [2.118(11)AI in the isostructural magnesium derivative, [TpButlMgMe.SC As expected, the Zn-C bond length is slightly shorter than the Mg-C bond length,15 and similar results have been observed in comparisons of other structurally related Mg and Zn alkyl derivatives. For example, the Zn-C bond length [1.957(5)AI in the adduct (18-crown-G)ZnEtis also shorter than the Mg-C

1

(16) Spek, A. L.; Jastrzebski, J. T. B. H.; van Koten, G. Acta Crystallogr. 1987, C43, 2006-2007. (17) Engelhardt, L. M.; Jacobsen, G. E.; Patalinghug, W. C.; Skelton, B. W.; Raston, C. L.; White, A. H. J . Chem. Soc., Dalton Trans. 1991, 2859-2868. (18)Hursthouse, M. B.; Motevalli, M.; O'Brien, P.; Walsh, J. R.; Jones, A. C. Organometallics 1991,10, 3196-3200. (19)Dekker, J.; Boersma, J.; Femholt, L.; Haaland, A.; Spek, A. L. Organometallics 1987, 6, 1202-1206. (20)(a)Parkin, G. Acc. Chem. Res. 1992,25,455-460. (b) Parkin, G. Chem. Rev. 1993,93, 887-911.

[TpBU']Zn-X (X = CI, Br, I, CN, N3, NCS, OAC)

bond length [2.104(2) A] in the related complex, (18~rown-G)MgEt2.~l The alkyl derivatives [TpMe21ZnMe,[TpBU'lZnMe, and [TpBUtlZnEt are soluble in hydrocarbon solvents and are characterized in solution by well-defined lH and 13C NMR spectra (Table 4) which provide a useful spectroscopic handle for monitoring reactions. For example, in addition to resonances assignable to the tris(pyrazoly1)hydroborato ligand, the complex [TpBUtlZnMeis characterized by resonances attributable to the Zn-Me group at 6 0.54 ppm in the lH NMR spectrum and at 6 -2.8 [q, VC-H= 118 Hzl in the 13CNMR spectrum. The reactivity of the four-coordinate alkyl derivatives [TpButlZnRtoward a number of reagents has been examined and is summarized in Scheme 2. Halogens (X2) rapidly cleave the Zn-C bond t o eliminate RX and give the halide complex [TpButlZnX(X = C1, Br, I). Protic reagents (HX)also readily cleave the Zn-R bond in [TpButlZnRto eliminate RH, with the concomitant formation of the corresponding [TpButlZnXderivative. Thus, the reactions of [TpBut1ZnRwith hydrogen chloride, acetic acid, and phenylacetylene give [TpBut]ZnCl, [TpButlZn(+02CMe)and [TpBUtlZnCCPh, respectively. Moreover, HX (X = Br, I, CN, N3, NCS), generated in situ by the treatment of MesSiX with H20, also reacts with [TpBUtlZnRto give [TpBUtlZnX.Trofimenko has previously synthesized [TpButlZnX(X = N3, NCS) by the reactions between KTTpBUtl and ZnX2.3 In a similar way, the complexes [TpBUtlZnX (X = Cl, Br, I, CN, 02CMe) may also be synthesized by metathesis of ZnX2 with either KTTpButlor T1[TpButl(eq 1). Furthermore, Vahrenkamp and Klaui have also independently used related methods for the synthesis of [TpPhzlZnXand [TphlZnX derivatives .IO922

(M = K. TI)

The molecular structures of the derivatives [TpBUtlZnX

(X= C1, Br, 1),13[ T P ~ ~ ~ I Z [TpBUtlZn(yl-OzCMe), ~CN,~~ ~

(21)Pajerski, A. D.; BergStresser, G. L.; Parvez, M.; Richey, H. G., Jr. J. Am. Chem. SOC.1968,110,4844-4845. (22) Hartmann, F.; Kiaui, W.; Kremer-Aach, A.; Mootz, D.; Strerath, A.; Wunderlich, H. 2.Anorg. Allg. Chem. 1993, 619, 2071-2076. (23) Yoon, K; Parkin, G. Znorg. Chem. 1992,31, 1656-1662.


Organometallics, Vol. 14, No. 1, 1995 277

c2

Figure 2. Molecular structure of [TpBu']Zn(Vl-OZCMe). S

C

derivative [TpBU'lMgR.In this regard, the rates of the reactions of [TpBUtlZnRare significantly slower than those of the corresponding magnesium derivative^.^ For example, although both [TpBUtlZnEtand [TpBUtlMgEt react with PhCHzI to give [TpBUtlMI (M = Zn, Mg), the half-lives of samples prepared under similar conditions are ca. 2.3 x lo3 h and 0.23 h at 100 "C, respectively, a factor of 4 orders of magnitude difference in reactivity. A similar difference in reactivity is observed in the reactions of [TpBUtlZnMe and [TpBUtlMgMe toward COZ. Thus, whereas [TpButlMgMeundergoes insertion of COz , ~reaction ~ into the Mg-C bond at room t e m p e r a t ~ r eno is observed between [TpBUtlZnMe and COZa t 140 "C, even though the expected product, [TpBUtIZn(y1-02CMe), has been prepared independently (vide Finally, whereas benzene solutions of the magnesium alkyl derivatives [TpBu'lMgR (R = Me, Et, Pr', But) react immediately with 0 2 a t room temperature to give alkyl peroxo derivatives [TpButlMgOOR,5~32 solutions of the zinc derivative [TpBUtlZnEt are stable toward 0 2 at 100 "C! The reactivity of the less sterically demanding derivative [TpMezlZnMehas also been investigated. This complex is indeed more reactive than [TpButlZnMe toward a number of reagents, eg. Br2, Iz, MeOH, PhOH, ButOOH, MeI, BrCN, and HC1. However, in each case the major product of the reaction is the six-coordinate sandwich complex [TpMe212Zn,as a result of ligand redistribution (eq 2).33The facile formation of [TpMe21z-

H-%.

Z=.&z-,

xy

Figure 3. Molecular structure of [TpBUt]ZnNCS. and [TpBu'lZnNCS have been determined by X-ray diffraction, with the structures of [TpBUt]Zn(yl-OzCMe) and [TpBUtlZnNCS shown in Figures 2 and 3. Selected bond lengths and angles for [TpBUtlZn(y1-OzCMe) and [TpButlZnNCSare presented in Tables 5 and 6. The X-ray diffraction studies confirm that the acetate ligand in [TpButlZn(y1-02CMe)is bound to zinc in a unidentate mode, with substantially different Zn-0 separations of ca. 1.86 A and 2.95 The structure of [TpBUt1Zn(y1-OzCMe), which is similar to that proposed for [TpButlMg(y1-O~CMe),5 contrasts with that of the copper analogue [TpBut1Cu(y2-OzCMe) which has been proposed to exhibit bidentate coordination of the acetate ligand on the basis of the observed EPR spectrum.25,26 Such a change in coordination mode for copper and zinc derivatives is t o be anticipated on the basis of our recent structural studies on the nitrate derivatives [TpButlM(N03)(M = Co, Ni, Cu, Zn), for which the coordination mode of the nitrate ligand varies from unidentate for Zn to symmetric bidentate for Ni and It is of particular interest t o compare the reactivity of [TpBUtlZnR with that of the isostructural magnesium (24) The thioacetate derivative [TpPhlZn{ql-SC(0)Me}also exhibits = 2.92 unidentate coordination with d(Zn-S) = 2.20 A and d(Zm 0) A. See ref 10. (25) Tolman, W. B. Znorg. Chem. 1991,30 4877-4880. (26) Moreover, the related derivative [TpR'21Cu(q2-O~CC&I&l) has been structurally characterized by X-ray diffraction: Kitajima, N.; Fujisawa, IC;Mor-oka, Y. J.Am. Chem. SOC.1990,29, 357-358. (27) Han, R.; Parkin, G. J.Am. Chem. Soc. 1991,113,9707-9708. (28) Han, R.; Looney, A.; McNeill, K.; Parkin, G.; Rheingold, A. L.; Haggerty, B. 5. J . Znorg. Biochem. 1993,49, 105-121. (29) Looney, A.; Han, R.; McNeill, K.; Parkin, G. J.Am. Chem. SOC. 1993, 115, 4690-4697.

-

(XY = Br2.12, MeOH, PhOH, But 02H, Mel, BrCN, HCI)

Zn in the reactions of [TpMezlZnMeis analogous to that observed for (i)the magnesium derivatives [TpM*lMgR,5,9 and (ii)the zinc alkyls LoE$~Rsupported by the oxygen ~ [CpCo{P(0)(0Et)~}31.~~ Furthertripod ligand L O E= more, the bis complex [TpPh12Zn (and also [TpA~lzZn derivatives) has also been observed independently by Vahrenkamp and Klaui to be a product of the reactions of [TpPhlZnXderivatives.lobPz2Such observations again underscore the benefits associated with the bulky [TpButl ligand, the "tetrahedral e n f ~ r c e r "nature ~ of which effectively inhibits such reaction pathways. (30) It should be noted that the reaction between [TpBu']MgMe and COSis slow, but observable, at room temperature. However, at 80 "C the reaction takes place readily. See ref 5. (31) It is worth noting that dialkylzinc compounds also do not react readily with carbon dioxide. However, in the presence of N-methylimidazole as a catalyst, insertion of C02 into the Zn-C bond may occur. See ref la. (32) In addition, the trimethylsilylmethylderivative [TpBU'1MgCHzSiMes reacts with 02 to give the trimethylsiloxide derivative: Han, R.; Parkin, G. Polyhedron 1990,9, 2655-2657. (33)In the absence of any reagent, solutions of [TpMealZnMein benzene may be heated to 120 "C in a sealed tube for 12 h without significant decomposition. (34) honey, A.; Cornebise, M.; Miller, D.; Parkin, G. Znorg. Chem. 1992,31,989-992.

278 Organometallics, Vol. 14,No. 1, 1995

Looney et al. Table 4. N M R Datau

type

'H NMR

'H N M R

assgnt

&ppm

q3-HB{C3NzH2C(CH3)3}3 1.41 V~-HB{C~N~HZC(CH~)~}~ 1H 5.85 1H 7.36 q3-HB{C3N2H2C(CH3)3)s not obsd ZnCH3 0.54

q3-HB{C3N2H2C(CH3)3)3 1.41 v~-HB{C~N~HZC(CH~)~I~ 1H 5.84 1H 7.36 q3-HB{C3N2H2C(CH3)3}3 not obsd ZnCH2CH3 1.31 ZnCHzCH3 1.96

coupling/Hz S

type [TpBu']ZnMe I3C NMR

d, 3 J ~ =- 2.2 ~ d, 'JH-H= 2.2

assgnt q3-HB{C3NzHzC(CH3)3}3

coupling/Hz

a/PPm 30.7

q3-HB{C3NzH2C(CH3)3}3 32.0 V~-HB{C~NZHZC(CH~)~I~ 1 c 102.0

q, 'Jc-H= 126 spt (partial res), 3JC-H = 5 dct (partial res), z J ~ = - 4~

S

S

[TpBU']ZnEt I3CNMR

d, 3 H ~ =- 2.2 ~ d, 3 J ~ =- 2.2 ~

S

1.49

S

5.83 7.34 not obsd 5.36

d, 3 J ~ =- 2.2 ~ ~ d, 3 J ~ =- 2.2

135.2

1 c ZnCH3

164.4 -2.8

q3-HB{C3N2HzC(CH3)3}3

30.9

q3-HB{C3N2H2C(CH3)3}3 32.0 v~-HB{C~NZHZC(CH~)~}~ 1 c 102.0

q, 3JH-H = 8.0 t, 3JH-H 8.0

2.14 2.20 5.50 0.28 not obsd

1 c

1 c

[Tp'k-]ZnMe I3C NMR

S S S

q, 'Jc-H = 126 spt (partial res), 3JC-H = 5 dct (partial res), zJc-H = 4

135.4

1 c ZnCHzCH3

164.7 7.3

ZnCHzCH3

13.9

q3-HB{C3N2H(CWds 12.3 $-HB{ C~NZH(CH~)Z}~ 12.9 1 c 104.6 1 c 144.1 1 c 148.6 Zn-CH3 -16.7

[TpBU']ZnH 13CNMR

q, 'Jc-H = 125 Sspt (partial res), 3JC-H = 5

S

1 c

135.2

q, 'Jc-H = 126 spt (partial res), 3JC-H = 5 dct (partial res), z J ~=-4 ~ d, 'Jc-H= 176 d, zJ~-H =9 d, 'Jc-H = 185 d, 'Jc-H = 8

1 c ZnOzCH

165.6 166.7

S

d, 'Jc-H = 202 4, 'Jc-H= 126

spt (partial res) 3 J c - ~= 5 dct (partial res) 2 J ~= - 5~

1c 1 c ZnOzCCH3 ZnOzCCH3

136.1 165.2 23.1 177.0

d, 'Jc-H = 176 d, 2 J ~=-9~ d, 'Jc-H= 185 d, 'Jc-H = 7 S

q, 'Jc-H = 126 S



Table 4 (Continued) ~~

type

assgnt

d/ppm

coupling/Hz

~~

type

assgnt

‘H N M R

ZnCzC6H5 2 0-H 2 m-H, 1p-H

‘H NMR

5.83 7.31 not obsd

d, 3 J ~ =- 2.2 ~ d, 3 J ~ =- 2.2 ~

7.18 7.04 - 7.20

m m

d/PPm 30.9

q, IJC-H = 126 spt (partial res), 3Jc-H = 5

32.3

s

102.2

d, ~Jc-H = 175 d, z J ~ = - 9~ d, ‘Jc-H = 185 d, z J ~ = - 6~ s

1 c

135.4

1 c ZnCzPh 1 c 1 c ZnCzCd-Is 1 ipso-c 2 0-c

164.9 111.3 112.7 128.4 128.2

2 m-C

131.8

1 p-c

126.8

31.1 32.2 102.5 135.7

‘H NMR

s d, ‘Jc-H = 188 d, z J ~ = - 8~ d, IJc-H = 160 t, z J ~ = - 7~ d, IJc-H = 160 t, z J ~ = - 7~

q, I J c - ~= 126 spt (partial res), 3Jc-H = 5 dct (partial res), z J ~ = - 4~ d, IJc-H = 176 d, z J ~ = - 9~ d, IJC-H = 186 d, 2 J ~ = - 6~ s

31.0

q, ~ J c - H= 126 spt (partial res), 3Jc-H = 5 dct (partial res), z J ~ = - 4~

164.9 5.2

d, IJc-H = 176 d, Z J ~ - H =9 d, ‘Jc-H = 186 d, z J ~ = - 7~ s q, ~ J c - H= 117

31.1 31.8

q, ~ J c = - ~126 s

102.2

d, ‘Jc-H = 175 d, z J ~ = - 9~ d, ~Jc-H= 185 d, 2 J ~ =- 7~ s q, IJc-H = 122

102.0 135.6

135.7 162.9 -10.9 ‘H NMR

s

165.4

32.1

‘H NMR

coupling/Hz

31.0 31.7 102.1 135.6 162.7 12.5 2.3

q, ‘Jc-H= 126 spt (partial res), ~ J c - H= 5 s d, ‘ J c - ~= 175 d, z J ~ = - 9~ d, ‘Jc-H = 186 d, z J ~ = - 8~ s

q, ‘Jc-H = 125 t, ’Jc-H = 5 t, ‘Jc-H = 121 q (partial res), ’Jc-H = 4 q (partial res), ’Jc-H = 4


Looney et al.

Table 4 (Continued) assgnt

dlppm

coupling/Hz

type

assgnt

BlPPm

coupling/Hz


Organometallics, Vol.14,No.1, 1995 281

Table 4 (Continued) type

assgnt

6JPPm

coupling/Hz '

'H NMR

H ~ B { C ~ N ~ H ~ C ( C H ~ ) ~1.31 }Z HzB{C~NZHZC(CH~)~IZ 1H 5.28 1H 7.47 H2B{C3N2H2C(CH3)3}2 not obsd Zn(+02CCH3) 2.06

S

assgnt

type

[BpBUjZn(q2-02CCHs) I3C NMR

d, 33H-H = 2.2 d, 3 J ~ =- 2.2 ~

HZB{C~NZH~C(CH~)~}Z30.6 HzB{C~NZHZC(CH~)~IZ31.6 HZB{C~NZHZC(CW~IZ 1 c 102.3 1 c

S

136.8

1 c Zn(qz-02Cc'H3) Zn(q2-02CCH3) 'H NMR

a

q3-HB{C3Nfi(C&)z}3

1.63 2.29 V~-WC~N~H(CH~)Z 5.69 }~ T$HB{C~N~H(CH~)~)~ not obsd

[TpMe~]zZn 13CNMR

S S S

6/ppm

164.7 24.6 181.5

q3-HB{C3NzH(CH3)2}3

12.2 12.9 v~-HB{C~NZH(CH~)ZI~ 1 c 105.1 1 c 143.1 1 c 149.1

coupling/Hz 9. 'Jc-H = 126 5

d, 'Jc-H = 175 d, 'Jc-H = 9 d, 'Jc-H= 185 d, 'Jc-H = 6 s q, 'Jc-H = 130 s

9, 'Jc-H = 128

q, 'Jc-H = 129 d, 'Jc-H= 170

s s

In c a s . Abbreviations: s = singlet, d = doublet, t = triplet, q = quartet, spt = septet, dct = dectet, m = multiplet. ZHNMR for ZnOD: 6 2.23 (s).

Table 5. Selected Bond Lengths (A) and Angles (deg) for [TpBU'lZn(q1-02CMe) Zn-O(1) Zn-N(22) 0(1)-C(1) C(l)-C(2) N(21)-N(22) B-N(11) B-N(31) N(12)-Zn-O(l) N(32)-Zn-0(1) N(12)-Zn-N(32) Zn-O(1)-C( 1) O(l)-C(l)-C(2)

1.859(6) 2.075(5) 1.241(12) 1.480(15) 1.368(8) 1.548(10) 1.539(10) 122.1(3) 129.2(2) 97.0(3) 122.7(6) 116.6(9)

Zn-N(l2) Zn-N(32) 0(2)-C(1) N( 11)-N( 12) N(3 1)-N(32) B-N(21) N(22)-Zn-0(1) N(12)-Zn-N(22) N(22)-Zn-N(32) O(l)-C(1)-0(2) 0(2)-C(l)-C(2)

2.061(5) 2.108(6) 1.225(13) 1.364(9) 1.368(8) 1.522(10) 115.6(3) 92.1(2) 91.4(3) 122.0(9) 121.1(10)

Table 6. Selected Bond Lengths (A) and Angles (deg) for [TPlZnNCS Zn-N Zn-N(22) N-C N(ll)-N(12) N(3 1)-N(32) B-N(21) N-Zn-N( 12) N-Zn-N(32) N(12)-Zn-N(32) Zn-N-C

1.893(4) 2.027(3) 1.164(6) 1.374(5) 1.369(4) 1.548(6) 120.5(1) 121.7(1) 95.8(1) 171.4(4)

Zn-N( 12) Zn-N(32)

c-s

N(21)-N(22) B-N(11) B-N(31) N-Zn-N(22) N(12)-Zn-N(22) N(22)-Zn-N(32) N-C-S

2.041(3) 2.029(3) 1.586(5 ) 1.378(4) 1.541(6) 1.535(5) 123.1(1) 94.4(1) 94.3(1) 179.7(4)

Figure 4. Molecular structure of [TpMe212Zn. Table 7. Selected Bond Lengths (A) and Angles (deg) for [TpMez]2Zn Zn-N( 12) Zn-N(32) N(2 1)-N(22) B-N(l1) B-N(31)

2.187(3) 2.146(2) 1.373(2) 1.538(4) 1.546(4)

Zn-N(22) N(l1)-N(12) N(31)-N(32) B-N(21)

2.183(2) 1.372(2) 1.374(3) 1.539(3)

[TpMez12Znmay also be prepared directly by the reaction of NTpMez1with ZnCl2, and its molecular 87.2(1) N(12)-Zn-N(32) 85.9(1) N(12)-Zn-N(22) structure has been determined by X-ray diffraction N(22)-Zn-N(32) 86.1(1) N(12)-Zn-N(12') 180.0 N(22)-Zn-N(12') 92.8(1) N(32)-Zn-N(12') 94.1(1) (Figure 4). Selected bond lengths and angles are listed N(12)-Zn-N(22') 92.8(1) N(22)-Zn-N(22') 180.0 in Table 7. The structure of [TpMe212Znis closely related N(32)-Zn-N(22') 93.9( 1) N(22)-Zn-N(32') 93.9(1) to that of the magnesium analogue [ T P ~ ~ ~ IIn~ M ~ N(12)-Zn-N(32') . ~ 94.1(1) N(32)-Zn-N(32') 180.0 marked contrast, however, the related [TpPh12Zncomplex does not exhibit an analogous structure. Specifically, the potentially tridentate [Tpphlligand acts only which exist as two-coordinate monomeric species, zinc as a bidentate ligand in [ ~ ~ - T p ~ ~ lso z Zthat n , ~the ~ hydride is a polymeric material that is insoluble in most complex adopts only a four-coordinate pseudotetraheorganic solvents.36 By analogy with the use of the trisdral geometry, rather than the six-coordinateoctahedral (pyrazoly1)hydroboratoligand to support the monomeric geometry adopted by [TpMe212Zn. The Zn-N bond zinc alkyl derivatives described above, it was anticipated lengths in the four-coordinate complex [y2-TpPh12Zn are that the zinc hydride complex [TpBUtlZnH could also be also slightly shorter (2.013[61A) than in the octahedral synthesized. Indeed, [TpButlZnHis readily prepared by derivative (2.17[31A). It is also worth noting that the metathesis of ZnH2 with Tl[TpBUtl(eq 3). As with the four-coordinate structure of [q2-TpPh12Zncontrasts with reactions between ZnR2 and Tl[TpButl,the decomposition the structure of [TpPh12Fe,in which the Fe is octahe(35)Eichorn, D.M.;Armstrong,W. H. Znorg. Chem. 1990,29,3607drally c o ~ r d i n a t e d . ~ ~ 3612. Synthesis, Characterization, and Reactivity of (36)De Koning, A. J.; Boersma, J.; van der Kerk, G. J. M. J. Organomet. Chem. 1980,186,159-172. [TpBUtIZnH. In contrast to dialkylzinc derivatives

Looney et al.


Table 8. Selected Bond Lengths (A) and Angles (deg) for ITnBU'lZnH . L

Zn-N(12) Zn-N(32) N(21)-N(22) B-N(11) N(3 l)BN(12)-Zn-N(22) N(22)-Zn-N(32)

.

2.078(5) 2.079(5) 1.359(8) 1.549(9) 1.556(10)

Zn-N(22) N(l1)-N(12) N(31)-N(32) B-N(21)

90.2(2) 92.3(2)

2.089(6) 1.371(7) 1.348(9) 1.541(9)

N(12)-Zn-N(32)

91.7(2)

Figure 5. Molecular structure of [TpBUtlZnH. (The hydride

ligand was not located and is illustrated in an idealized position.) of putative [TlHI provides an effective driving force for the reaction.

Zinc hydride derivatives are rare and are typically v(Zi-D) o l i g o m e r i ~ . For ~ ~ .example, ~~ some zinc hydride deriva1 tives include [Hz1iN(Me)CH&HzNMe212,3~ [HznOB~~l4,3~ 2& 2000 1800 1600 1400 1200 l000cm" [HZnO(CH2)2NMe212,40and [RZnH(NC5H& (R = Et, Figure 6. IR spectra of (a) [TpBUtlZnH and (b) [TpBUtlZnD. Phh41 Of these derivatives, the only other structurally Scheme 3 characterized zinc hydride complex is dimeric [HZnN(Me)CH&H2NMe212.38 [TpBU1]Zn(q'-O~CH) The molecular structure of [TpBUtlZnHhas been (TpBuljZn-C=C-Ph determined by X-ray diffraction (Figure 51, which clearly identifies its monomeric nature. [TpBUtlZnH is the first structurally-characterized monomeric zinc hydride derivative of which we are aware, and the synthetic (TpBU1]Zn-OSiMe3 methodology has also been applied to the synthesis of the terminal beryllium and cadmium hydride derivatives, [TpBUtlBeH42p43 and [TpBUtlCdH.44 Selected bond lengths and angles for [TpBUtlZnHare presented in Table 8. The hydrogen atom bound to zinc in [TpButlZnH was not located by the X-ray diffraction study; however, the expected axial location of the hydride ligand is clearly suggested by the trigonal coordination of the tris(3-tert-butylpyrazolyl)hydroborato ligand illustrated in Figure 5. Furthermore, evidence for the presence of the hydride ligand is provided by NMR and 1

(37) (a) De Koning, A. J.; Boersma, J.; van der Kerk, G. J. M. J. Organomet. Chem. 1980,195,l-12. (b) Ashby, E. C.; Goel, A. B. Inorg. Chem. 1981,20, 1096-1101. (c) De Koning, A. J.; Boersma, J.; van der Kerk, G. J. M. Tetrahedron Lett. 1977, 2547-2548. (38) (a) Bell, N. A.; Coates, G. E. J. Chem. SOC.A 1968, 823-826. (b) Bell, N. A.; Moseley, P. T.; Shearer, H. M. M.; Spencer, C. B. J. Chem. SOC.,Chem. Commun. 1980,359-360. (c) Bell, N. A.; Moseley, P. T.; Shearer, H. M. M.; Spencer, C. B. Acta Crystallogr. 1980, B36, 2950-2954. (39) Neils, T. L.; Burlitch, J. M. Inorg. Chem. 1989,28,1607-1609. (40) Goeden, G. V.; Caulton, K. G. J. Am. Chem. SOC.1981, 103, 7354-7355. (41)De Koning, A. J.; Boersma, J.; van der Kerk, G. J. M. J. Organomet. Chem. 1978,155, C5-C7. (42) Han, R.; Parkin, G. Inorg. Chem. 1992,31, 983-988. (43) The first terminal beryllium hydride complex to be structurally characterized by X-ray diffraction was the dimer [(Me2NCH2CHme)BeHl2. (a) Bell, N. A.; Coates, G. E.; Schneider, M. L.; Shearer, H. M. M. J. Chem. Soc., Chem. Commun. 1983, 828-829. (b) Bell, N. A.; Coates, G. E.; Schneider, M. L.; Shearer, H. M. M. Acta Crystallogr. 1984, C40, 608-610. (44) (a) Reger, D. L.; Mason, S. S.; Rheingold, A. L. J. Am. Chem. SOC.1993, 115, 10406-10407. (b) Reger, D. L.; Mason, S. S.; Rheingold, A. L. J. Am. Chem. SOC.1994, 116, 2233.

I

I

I

I

IR studies. For example, the hydride resonance is observed at 6 5.36 ppm in the lH NMR spectrum, an assignment that has been confirmed by the 2H NMR spectrum of the isotopomer [TpBUtlZnD.Similarly, Y(Zn-H) is observed as a strong absorption at 1770 cm-l in the IR spectrum, which shifts t o 1270 cm-l (YH/VD = 1.39)upon deuterium substitution, as shown in Figure 6. The zinc-hydride functionality in [TpBUt]ZnH is reactive toward a number of substrates, as summarized in Scheme 3. Thus, protic reagents (HX = H2S, MesSiOH, MeCOzH, PhCSCH) react at the Zn-H bond to give [TpBUtlZnX and H2. The complex [TpBUtlZnOSiMe3 may also be prepared independently by the reaction of



[TpBUtl-ZnCl with KOSiMe3 (eq 4). The Zn-H bond also

undergoes metathesis with a variety of halide derivatives. For example, [TpBUtlZnHreacts with Me1 and PhCHzI to give [TpBUtlZnIand CH4 and RH (R = Me, PhCHz). The reactions between [TpBUtlZnHand RI, which occur at room temperature, were observed to be more facile than those of the corresponding alkyl derivatives [TpBUtlZnR.The source of the hydrogen in the RH products was confirmed as the Zn-H group by the reaction of [TpBUtlZnDwith RI. [TpBUtlZnHalso reacts with MeCOC1, Me3SiX (X = C1, I) and IZto give [TpBUtlZnX (X = C1, I). The Zn-H group in [TpBUtlZnHundergoes clean insertion of COZat 50 "C to give the ql-formato derivative, [TpBUtlZn(q1-02CH).It is noteworthy that, as described above, the methyl derivative [TpButlZnCH3 does not react with COPunder similar conditions. The formato derivative [TpBUt]Zn(q1-02CH) has been characterized by NMR and IR spectroscopy. The formato moiety of [TpBUt1Zn(q1-OzCH) is observed as a singlet at 6 8.91 ppm in the lH N M R spectrum and as a doublet = 202 Hz) in the 13C NMR at 166.7 ppm (~Jc-H spectrum. Although the molecular structure of [TpBUtlZn(ql-O~CH) has not been determined by X-ray diffraction, the complex is characterized as an ql- rather than q2-formatoderivative by analogy with the acetato complex [TpBUt1Zn(q1-0zCMe) (vide supra), and also on the basis of the stretching frequencies of the vaSym(CO2) (1655 cm-l) and vSym(C02) (1290 cm-l) absorptions in the IR spectrum. The absorptions associated with the formato group have been identified by the shifts observed for the isotopomers [TpBUtlZn(q1-0~13CH) and [TpBUt1Zn(q1-OzCD) (Figure 7). Most notably, the large difference between vSym(C0z) and ~a,3ym(C02) (Av = 365 cm-l) is very diagnostic of ql-c~ordination.~~ The insertion of C02 into the Zn-H bond of [TpBUtlZnH contrasts with the inertness of the alkyls [TpBut13ZnR toward CO2. However, the Zn-H moiety is inert (at 120 "C and 1 atm) toward insertion of ethylene to give the ethyl derivative [TpButlZnEt.Such an observation is presumably a reflection of kinetic factors since the ethyl derivative is stable under these conditions. Synthesis, Characterization, and Reactivity of the Three-Coordinate Zinc Alkyl Derivatives [BpBUtlZnR. The above studies have demonstrated the use of the tris(3-tert-butylpyrazolyl)hydroborato ligand to provide a well-defined environmentfor the study of four-coordinate alkyl and hydride derivatives of zinc. In order to investigate changes in reactivity of the Zn-C bond upon lowering the coordination number at the metal from four to three, we have utilized the cor(45) Monomeric carbxylato complexes with Av values greater than 200 cm-l invariably have unidentate coordination: Deacon, G. B.; Phillips, R. J. Coord. Chem. Rev. 1980, 33, 227-250.

I

2;OO

2000

1800

1600

li00

lib0

ldOOcm.'

Figure 7. IR spectra of (a) [TpButlZn(y1-02CH), (b) [TpBUtlZn(q1-0213CH), and ( c ) [TpBUtlZn(ql-O&D). responding bidentate bis(3-tert-butylpyrazolyl)hydroborat0 ligand, [BpButl. By analogy with the complexes [TpButlZnR,the threecoordinate zinc alkyl derivatives [BpBUtlZnR (R = Me, Et, But) are readily prepared by metathesis of RzZn with the thallium derivative T1[BpButl(eq 5). The molecular &-Bu'

,w

structure of the tert-butyl derivative [BpBUtlZnButhas been determined by an X-ray diffraction study (Figures 8 and 91, and selected bond lengths and angles are listed in Table 9. The zinc center may be described as distorted trigonal planar, with the bond angles N(12)Zn-N(22) = 94.3(2)",N(12)-Zn-C(1) = 132.2(3)",and N(22)-Zn-C(1) = 132.7(3)". The sum of the three bond angles at zinc is 359.2(8)", clearly indicating a high degree of coplanarity. Three coordination is quite rare for zinc compared to four-coordination, although in recent years the number of such complexes has begun to increase quite rapidly.46 Some specific examples of three-coordinate organozinc complexes include (i) {(Me3Si)~(Ph)P(NSiMe3)2}ZnPh,4~ (ii)[Zn(CHzCMe&I-, [Zn(CHzSiMe3)31-, and [ Z ~ ( C H Z S ~ M ~ & P (iii) ~ II(Me3-,~ Si)zCHlzZn[q1-(MeNCH2)31 and [Zn{CH(SiMe&)31-,49

Looney et al.

284 Organometallic's, Vol. 14, No. 1, 1995

82

B

Figure 8. Molecular structure of [BpBUtlZnBut.

Figure 10. Molecular structure of { [BpButlZn~-OH>}3. Scheme 4

h -RH

Figure 9. Molecular structure of [BpBUtlZnBut.

([BpeU']Zn(p-OH))~

Table 9. Selected Band Lengths (A) and Angles (des) for [BpBu']ZnBd

The three-coordinate alkyl derivatives [BpBUtlZnR are also well characterized by lH and 13CN M R spectroscopy in solution. For example, [BpBUtlZnMeexhibits reso2.040(5) 1.995(7) Zn-N( 12) Zn-C(l) C(l)-C(2) 1.486(15) Zn-N(22) 2.045(6) nances attributable to the Zn-Me group at 6 1.41 and C(l)-C(4) 1.501(11) cm-c(3) 1.495(13) 30.7 (9,VC-H= 126 Hz) in the lH and 13CNMR spectra, 1.377(8) 1.367(8) N(21)-N(22) N(ll)-N(12) respectively. 1.541(12) 1.547(10) B-N(21) B-N( 11) The reactivity of [BpBUtlZnR is summarized in Scheme C(l)-Zn-N(12) 132.2(3) C(l)-Zn-N(22) 132.7(3) 4. The Zn-C bonds are readily cleaved by the protic N(12)-Zn-N(22) 94.3(2) Zn-C(1)-C(2) 108.6(5) reagents HzO and MeCOzH to give the hydroxo ([BpBut13Zn-C( 1)-C(3) 114.7(5) Zn-C(1)-C(4) 109.7(6) Zn@-OH)}s and acetato [BpBUtlZn(yZ-OzCMe) derivaC(2)-C(l)-C(3) 107.2(9) C(2)-C(l)-C(4) 108.8(7) tives, respectively. The molecular structure of the C(3)-C(l)-C(4) 107.7(8) hydroxo derivative {[BpButlZn(D-OH))3 has been determined to be a cyclic trimer by X-ray diffraction (Figure lo),and selected bond lengths and angles are given in Table 10. The molecule exhibits approximate C3h symmetry, with each hydroxo group bridging two zinc centers. Although the X-ray structure determination did not reveal the location of the hydroxo hydrogen (46) Recent examples of non-organometallic three-coordinate zinc atoms, convincing evidence for their presence is procomplexesinclude [Zn{S(Cd-IMe4)}31-,46*[Zn(u-OCEta){N(SiMe3)~}12,~ vided by the 40-H) absorption at 3611 cm-l in the IR [Zn{y-S(C~HzBut~)}{S~C~H~B~t~)}l~,46c Z ~ { S ( C ~ H Z B U ~ ~ ) }Zn{L},~~~ [Znbc-TeSi{ S ~ ( C ~ H ~ B U ~ ~ ) [ZnOt-P(SiMe3)2}{P(SiMes)z)l2,48" }{L},~~~ spectrum. This assignment has been confirmed by (SiMe3)3}{TeSi(SiMe3)s}l~,4~~ Zn(SC~HzBu~s)z(OEtz),~g [ZndButzP)zthe observation of the shifts observed for the isotopomer (OH)@-OH)12,46h Zn[FeCp(C0)213-,461and [q2-R2N(Ph)P(NR)21ZnPh:46j

(a) Gruff, E. S.; Koch, S.A. J.Am. Chem. SOC. 1989,111,8762-8763. (b) Goel, S. C.; Chiang, M. Y.; Buhro, W. E. Inorg. Chem. 1990,29, 4646-4652. (c) Bochmann, M.; Bwembya, G.; Grinter,R.; Lu, J.;Webb, K J.; Williamson, D. J.; Hursthouse, M. B.; Mazid, M. Inorg. Chem. 1993,32, 532-537. (d) Bochmann, M.; Bwembya, G. C.; Grinter, R.; Powell, A. It;Webb, K. J.; Hursthouse, M. B.; Malik, K. M. A.; Mazid, M. A. Inorg. Chem. 1994,33, 2290-2296. (e) Goel, S. C.; Chiang, M. Y.;Buhro, W. E. J.Am. Chem. Soc. 1990,112,5636-5637. (0Bonasia, P. J.;Arnold, J. Inorg. Chem. 1992,31,2508-2514. (g) Power, P. P.; Shoner, S. C.Angew. Chem., Int. Ed. Engl. 1990,29,1403-1404. (h) Arif, A. M.; Cowley, A. H.; Jones, R. A.; Koschmieder, S. U. J.Chem. Soc., Chem. Commun. 1987,1319-1320. (i)Petersen, R. B.; Ragosta, J. M.; Whitwell, G. E., 11;Burlitch, J. M. Inorg. Chem. 1983,22,34073415. (j) Romanenko, V. D.; Shul'gin, V. F.; Skopenko, V. V.; Markovskii, L. N.Zh. Obshchei Khim. 1984, 54, 2791-2792; J. General Chem. (Engl. Transl.) 1985, 250fL2502. (47) Chemega, A. N.;Antipin, M. Y.; Struchkov, Y. T.; Romanenko, V. D. Koord. Chim. 1989,15,894-901. (48) Purdy, A. P.; George, C. F. Organometallics 1992, 11, 19551959.

(49) Westerhausen, M.; Rademacher, B.; Schwarz, W. 2.Anorg. Allg. Chem. 1993,619,675-689. (50)Olmstead, M. M.; Power, P. P.; Shoner, S.C. J.Am. Chem. Soc. 1991,113, 3379-3385. (51)Parvez, M.: BergStresser. G. L.; Richey. H. G., Jr. Acta Crystallogr. 1992, C48, 641-644.' (52) Some older examples of three-coordinate organozinc derivatives [M~~N(CHZ)~IZ~WC~(CO)~,~~~ and KMezinclude [MeZn@-NPh~)12,~28 PhSi)&Zn@-OH)lz:S2c(a) Bell, N. A.; Shearer, H. M. M.; Spencer, C. B. Acta Crystallogr. 1983, C39, 1182-1185. (b) Budzelaar, P. H. M.; AlbertsJansen, H. J.; Mollema, K.; Boersma, J.; van der Kerk, G. J. M.; Spek, A. L.; Duisenberg, A. J. M. J.Organomet. Chem. 1983,243, 137-148. (0) Al-Juaid, S. S.; Buttrus, N. H.; Eaborn, C.; Hitchcock, P. B.; Roberts, A. T. L.; Smith, J. D. S.; Sullivan, A. C. J. Chem. SOC., Chem. Commun. 1986,908-909. (53) In the solid state, zinc exhibits three-coordination in the dialkyl Zn[CHzSiMezOPriIz due to a n intermolecular Zn-0 interaction [2.252(4) A]. The C-Zn-C bond angle is 152.3(3)":Gais, H.-J.; Biilow, G.; Raabe, G. J.Am. Chem. SOC.1993,115, 7215-7218.



Table 10. Selected Bond Lengths (A) and Angles (deg) for UBdn’lZnbOH)h ~

Zn( 1)-O( 1) Zn(2)-0(1) Zn(3)-0(2) Zn(l)-N(12) Zn(2)-N(22) Zn(3)-N(32) B(1)-N(l1) B(2)-N(21) B(3)-N(31) N(ll)-N(12) N(31)-N(32) N(5 I)-N(52)

1.923(8) 1.968(9) 1.985(8) 2.048(9) 2.034(10) 2.033(11) 1.586(20) 1.494(23) 1.515(26) 1.365(14) 1.378(16) 1.362(16)

O(l)-Zn(l)-0(3) 0(3)-Zn(l)-N(12) 0(3)-Zn(l)-N(42) 0(1)-Zn(2)-0(2) 0(2)-Zn(2)-N(22) 0(2)-Zn(2)-N(52) 0(2)-Zn(3)-0(3) 0(3)-Zn(3)-N(32) 0(3)-Zn(3)-N(62) Zn(1)-O(1)-Zn(2) Zn(l)-0(3)-Zn(3)

103.6(4) 112.1(4) 105.5(4) 104.0(4) 119.2(4) 121.1(4) 102.0(4) 120.1(4) 124.1(4) 135.3(5) 137.5(4)

~~

~~~~

Zn(1)-O(3) Zn(2)-O(2) fi(3)-0(3 Zn(l)-N(42) Zn(2)-N(52) Zn(3)-N(62) B(l)-N(41) B(2)-N(51) B(3)-N(61) N(21)-N(22) N(41)-N(42) N(61)-N(62)

1.957(10) 1.888(9) 1.917(10) 2.054(11) 2.022(11) 2.035(11) 1.554(22) 1.554(22) 1.613(24) 1.376(17) 1.325(17) 1.374(16)

O(l)-Zn(l)-N(12) 0(1)-Zn(l)-N(42) N(12)-Zn(l)-N(42) 0(1)-Zn(2)-N(22) 0(1)-Zn(2)-N(52) N(22)-Zn(2)-N(52) 0(2)-Zn(3)-N(32) 0(2)-Zn(3)-N(62) N(32)-Zn(3)-N(62) Zn(2)-0(2)-Zn(3)

118.9(4) 122.1(4) 94.3(4) 108.5(4) 109.0(4) 94.4(4) 109.3(4) 107.3(4) 93.4(4) 137.2(5)

Table 11. Zn-0 Bond Lengths of [Zn@z-OH)Zn] Moieties d(Zn- 0)lA {[BPB”’lZn@-OH)h KMeShSi)3CZn@-OH)lz [{ (BuPz)~Z~IZ@-OH)I~+ [(LH)zZnz@-oH)l+

1.89(1)-2.02(1) 1.899(9) 1.91[1] 1.915(2) [{(Me3tacn)Zn}z@-OH)@-O~CMe)]~1.996(4) [(Me3tacn)Zn@-OH)]zZf 1.97[11 [ { ~ 4 - N ( C H z ~ ~ ) s } ~ @ - O H ) l ~ z + 2.01[4] ~Znz~ButzP~z~OH~@-OH~1z 2.33[2]*

ref this work C

d e

f f g h

LH2 = 4,7-bis(2-hydroxybenyl)-1-oxa-4,7-diazacyclononane.The t e d a n l Zn-0 bond length is 2.30(2) A. Al-Juaid, S. S.;Buttrus, N. H.; Eabom, C.; Hitchcock, P. B.; Roberts, A. T. L.; Smith, J. D. S.; Sullivan, A. C. J. Chem. Soc., Chem. Commun. 1986, 908-909. dAlsfasser, R.; Vahrenkamp, H. Chm. Ber. 1993,126,695-701. Flassbeck, C.; Wieghardt, K.; Bill, E.; Butzlaff, C.; Trautwein, A. X.;Nuber, B.; Weiss, J. Inorg. Chem. 1992, 31, 21-26. fchaudhuri, P.; Stockheim, C.; Wieghardt, K.; Deck, W.; Gregorzik, R.; Vahrenkamp, H.; Nuber, B.; Weiss, J. Znorg. Chem. 1992,31, 1451-1457. 8 Murthy, N. N.; Karlin, K. D. J. Chem. SOC., Chem. Commun. 1993, 1236-1238. hArif, A. M.; Cowley, A. H.; Jones, R. A.; Koschmieder, S. U. J. Chem. SOC., Chem. Commun. 1987, 13191320.

{[BpButlZn01-OD)}3 (2670 cm-l). The Zn-OH moiety is also characterized by a resonance a t 2.25 ppm in the lH NMR spectrum. The hydroxo bridge between each pair of zinc centers is slightly asymmetric. in the trimer { [BpBUtlZn@-OH)}3 Thus, the lengths of the Zn-0 bonds alternate in a short-long fashion around the ZnsOs ring, although the differences are small, i.e. the Zn(1)-O(l), Zn(2)-0(2) and Zn(3)-0(3) bonds average 1.91[21A, while Zn(1)0(3), Zn(2)-0(1), and Zn(3)-0(2) bonds average 1.97[21AI. Notably, all these bridging Zn-OH interactions are longer than that in the monomeric terminal zinc hydroxo complex [TpBUtaelZnOH[1.850(8) 81154p55 but comparable to the values reported for a number of complexes with hydroxo groups bridging two zinc centers, as summarized in Table 11. The data presented in Table 11indicate that Zn-0 bond lengths for hydroxo groups that brid e two zinc centers are typically of the order 1.89-2.01 A notable exception, however, is the

f.

(54) Alsfasser, R.; Trofimenko, S.; Looney, A,; Parkin, G.; Vahrenkamp, H. Znorg. Chem. 1991,30,4098-4100. (55)The reference value for a pure single covalent Zn-0 bond has been adopted to be 1.89 A: Haaland, A. Angew. Chem., Znt. E d . Engl. 1989,28,992-1000.

complex [Zn2(But2P)z(OH)01-OH)12,with Zn-0 bond lengths (both terminal and bridging) which, as pointed out previously, are abnormally long (2.30-2.33 A),46h It is plausible that the origin of the long Zn-0 bond lengths in [ Z ~ Z ( B U ~ ~ P ) ~ ( O H )may ~ - ObeHan )]~ artifact due to contamination, possibly with a chloride derivative.20 Indeed, such a suggestion is reasonable since [Znz(But2P)2(0H)01-OH)Izwas prepared in only low yield by the reaction of ZnClz with ButzPLi and required the presence of adventitious water. The above reactions with protic reagents are analogous to those of the four-coordinate complexes, [TpButllZnR. However, whereas the tris(3-tert-butylpyrazoly1)hydroborato complexes [TpBUtlZnR only show reactivity at the Zn-C bond, the bis(3-tert-butylpyrazoly1)hydroborato derivatives also exhibit reactivity at an additional site, namely the B-H bond. Thus, the bis(3tert-butylpyrazoly1)hydroborato complexes, [BpBUtlZnR (R = Me, Et), react with aldehydes and ketones, (CHzO),, MeCHO, and MezCO, to give the derivatives {HB(OR)(3-Butpz)z}ZnR( R = Me, Et, Pr9, as a result of insertion into the B-H bond. We have not yet determined whether the alkoxo substituents on boron are also coordinated to the zinc center, i.e. {72-HB(0R’)(3Butpz)2}ZnR us {73-HB(OR)(3-Butpz)2}ZnR. Other bis(pyrazoly1)hydroboratometal complexes have also demonstrated the capability of reducing ketones to alcohols.56 However, functionalized bis(pyrazoly1)hydroborato products were not isolated.

Conclusion In summary, the tris(pyrazoly1)hydroborato ligand system has allowed the isolation of monomeric fourcoordinate zinc alkyl and hydride derivatives [TpButlZnR while the (R = Me, Et), [TpMezlZnMe,and [TpBUtlZnH, bis(3-tert-butylpyrazolyl)hydroboratoligand system has allowed the isolation of monomeric three-coordinate zinc alkyl derivatives [BpBUtlZnR(R = Me, Et, But). The four-coordinate alkyl complexes are isostructural with the analogous magnesium derivatives, and comparison of the reactivity of the Zn-C and Mg-C bonds in these complexes provides good evidence for the intrinsic higher reactivity of the Mg-C us the Zn-C bond. Comparison of the alkyl and hydride derivatives [TpButllZnR and [TpBUtlZnHindicates that the Zn-H bond exhibits higher reactivity than the Zn-C bond, especially with regards to insertion of CO2. In contrast to the four-coordinate zinc alkyls [TpBUtlZnR,the threecoordinate derivatives [BpBUtlZnR exhibit two different sites of reactivity. Thus, the Zn-C bonds of [BpBUtlZnR are the sites of reactivity with protic reagents such as H2O and MeCOzH, while the B-H bonds are the preferred sites of reactivity for insertion with ketones and aldehydes.

Experimental Section General Considerations. All manipulations were performed using a combination of glovebox, high-vacuum, and Schlenk technique^.^' Solvents were purified and degassed by standard procedures. lH and 13C NMR spectra were measured on Varian VXR 200, 300, and 400 spectrometers. (56) Paolucci, G.; Cacchi, S.; Caglioti, L. J.Chem. Soc.,Perkin Trans. 1 1979, 1129-1131.


Looney et al.

IR spectra were recorded as KBr pellets or Nujol mulls between KBr disks on a Perkin-Elmer 1420 spectrophotometer and are reported in cm-1. Mass spectra were obtained on a Nermag R10-10 mass spectrometer using chemical ionization (NH3 or CH4) techniques. Elemental analyses were measured using a Perkin-Elmer 2400 CHN elemental analyzer. ZnH2,36 Me3SiOH,S8 T1[TpBUt],3 T1[TpMez1,&KITpMezl,SeTl[BpBUtl,3 and [TpBut]ZnNCS3 were prepared by the literature methods. N M R data are listed in Table 4. Synthesis of [TpMB9lZnMe. A solution of excess MezZn in decalin was added to a stirred suspension of Tl[TpMe2](1.00g, 1.99mmol) in THF (30mL), resulting in the formation of a black precipitate. The volatile components were removed in uacuo, and the residue was extracted into benzene (ca. 30 mL). The mixture was filtered, the benzene removed in uacuo, and the product recrystallized from THF at -78 "C, giving [TpM"2]ZnMe as a white solid (0.13g, 17%). Anal. Calcd for [TpMe21ZnMe: C, 50.9;H, 6.7;N, 22.3. Found: C, 50.9;H, 6.7;N, 22.0. IR data: 2506 ( Y B - H ) . Synthesis of [TpBUt]ZnMe. A solution of Tl[TpButl(0.5 g, 0.85 mmol) in THF (20mL) was added dropwise t o a solution of MezZn in pentane (0.83g, 0.87 mmol), resulting in the immediate formation of a black deposit of T1 metal. The mixture was stirred for 30 min at room temperature and filtered. The volatile components were removed from the filtrate under reduced pressure. The solid was extracted into pentane (20mL) and filtered. The filtrate was concentrated to ca. 10 mL and placed at -78 "C giving a crop of colorless which were isolated by filtration and crystals of [TpBUt]ZnMe, dried in uucuo (150mg, 38%). Anal. Calcd for [TpBU'lZnMe: C, 57.3;H, 8.0;N, 18.2. Found: C, 56.6;H, 7.1;N, 17.2. IR data: 2505 ( Y B - H ) . MS: mlz 461 (M+ 1). Synthesis of [TpBut]ZnEt.A solution of T1[TpBUtl(1.0 g, 1.7 mmol) in THF (30mL) was added dropwise to a solution of EtzZn (1.4g, 15% wlw in hexane, 1.7 mmol) in THF (10mL) resulting in the formation of a black deposit of T1 metal. The mixture was stirred for 30 min at room temperature and filtered. The filtrate was concentrated to ca. 10 mL and placed at 0 "C giving a crop of colorless crystals of [TpBUtlZnEt,which were isolated by filtration and dried in uacuo (400mg, 50%). Anal. Calcd for [TpBUt]ZnEt:C, 58.1;H, 8.3;N, 17.7.Found: C, 56.9;H, 8.2;N, 16.9. IR data: 2452 and 2480 (YB-H). MS: mlz 475 (M+ 1). Syntheses of [TpBut]ZnX (X = C1, Br, I, CN, NCS, 0 2 CMe). The complexes [TpBU'IZnX were prepared by reaction of WTpButlor T1[TpButlwith ZnXz by a method analogous to that used for [TpBUt]ZnN3and [TpButlZnNCS,3and a typical procedure is given for [TpBu']ZnC1. A solution of T1[TpBUtl(2.0 g, 3.42 mmol) in THF (40 mL) was added to a stirred suspension of ZnClz (0.56g, 4.10 mmol) in THF (20 mL), resulting in the immediate formation of a white precipitate. The mixture was stirred for 1 h and filtered. The solvent was removed from the filtrate in uucuo, giving [TpBUtlZnC1as a white solid (1.57g, 96%). Anal. Calcd for [TpBUt]ZnC1:C, 52.4;H, 7.1; N, 17.5. Found: C, 52.6;H, 7.0;N, 17.4. IR data: 2490 ( Y B - H ) . MS: mlz 480 (M+ 1). Anal. Calcd for [TpBUt]ZnBr:C, 47.9; H, 6.5; N, 16.0. Found: C, 47.9;H, 6.4;N, 15.1. IR data: 2527 ( Y B - H ) . MS: mlz 526 (M+ 1). Anal. Calcd for [TpBU']ZnI: C, 44.0; H, 6.0; N, 14.7. Found: C, 44.2;H, 6.2;N, 14.4. IR data: 2519 ( Y B - H ) . MS: mlz 572 (M+ 1). Anal. Calcd for [TpBut]ZnCN: C, 55.9;H, 7.3;N, 20.7. Found: C, 56.2;H, 8.2;N,20.6.IR data: 2520 (YB-H) and 2214 ( Y C - N ) . MS: mlz 471 (M+ + 1).

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(57) (a) McNally, J. P.; Leong, V. S.; Cooper, N. J. ACS Symp. Ser. 1987,No. 357,6-23. (b) Burger, B.J.; Bercaw, J. E. ACS Symp. Ser. 1987,NO.357,79-97. (58) George, P.D.;Sommer, L. H.; Whitmore, F. C. J.Am. Chem. SOC.1963,75, 1585-1588. (59) Trofimenko, S . J. Am. Chem. SOC.1967,89,6288-6294.

Anal. Calcd for [TpBut]Zn(+OzCMe): C, 54.6;H, 7.4;N, 16.6. Found: C, 54.6;H, 7.2;N, 16.2. IR data: 2480 ( Y B - H ) and 1610 (vaSymCOJ. MS: mlz 505 (M+ 1). Reaction of [TpB"']ZnEtwith Cl2 and Br2. A solution of [TpBUt]ZnEt(20mg, 0.04mmol) in de-benzene (0.7mL) was treated with XZ (X = C1, Br, I). 'H NMR spectroscopy demonstrated the formation of [TpBUt]ZnX and EtX after 1 day at room temperature. Reaction of [TpB"]ZnEtwith MesSiX/HaO(X = C1, Br, I, CN, Ns, NCS). A solution of [TpBut1ZnEt(20mg, 0.04"01) in de-benzene (0.7mL) was treated with a mixture of M e $ % / HzO (X = C1, Br, I, CN, N3, NCS). The reactions were monitored by lH NMR spectroscopy which demonstrated the formation of [TpBU'lZnXand CZH.5. Reaction of [TpBU7ZnMewith HCl. A solution of [TpBut]ZnMe (20mg, 0.04mmol) in de-benzene (0.7mL) was treated with HC1 (1 atm) at room temperature. The reaction was monitored by lH NMR spectroscopy which demonstrated the immediate formation of [TpBUt]ZnC1. Synthesisof [TpBu7ZnC8ph.A solution of [TpBu'lZnEt(20 mg, 0.04 mmol) in &-benzene (0.7mL) was treated with PhCCH (0.05 mmol) and heated at 70-80 "C for a period of days. The reaction was monitored by lH NMR spectroscopy and C&. which demonstrated the formation of [TpBUt1ZnCzPh Anal. Calcd for [TpBut]ZnCzPh: C, 63.5;H, 7.3;N, 15.3. Found: C, 63.1;H, 7.4;N, 15.9. IR data: 2503 (YB-H). MS: mlz 547 (M+ 1). Reaction of [TpButlZnEtwith RI (R = Me, PhCH2). A solution of [TpBUt]ZnEt(20mg, 0.04mmol) in &-benzene (0.7 mL) was treated with RI (R = Me, PhCHz; 0.05 mmol) and heated at 140 "C over a period of weeks. The reactions were monitored by 'H NMR spectroscopy which demonstrated the slow formation of [TpBu']ZnI. Reaction of [TpBut]ZnEtwith MeC0J-I. A solution of in de-benzene (0.7mL) was [TpBUt]ZnEt(20 mg, 0.04 "01) treated with MeCOzH (2.8pL, 0.05 mmol) and left at room temperature. The reaction was monitored by 'H NMR spectroscopy which demonstrated the formation of [TpBUt]Zn(yl0zCMe) and CZH6. Reactions of [TpM*lZnMe. A solution of [TpMezlZnMe(ca. 10 mg) in de-benzene (0.7mL) was treated with a variety of reagents (Brz, 12, MeOH, PhOH, BuQOH, MeI, BrCN, HC1) and monitored by lH N M R spectroscopy. In each case, [TpMqIzZn was observed to be a major product. Synthesis of [TpMeal~n. A solution of K[TpMe21(500mg, 1.49mmol) in THF (20mL) was added t o a stirred suspension of ZnClz (101 mg, 0.74m o l ) in THF (10mL). The mixture was stirred overnight and the solvent removed in uacuo. The residue was extracted into CHzClz (30 mL) and the extract was washed with water. The solvent was removed from the CHzClz layer in uacuo, and the solid obtained was recrystallized from toluene at -78 "C. Yield of [TpMe2]~Zn:173 mg (34%). Anal. Calcd for [TpMe212Zn:C, 54.6;H, 6.7;N, 25.5. Found: C, 54.7;H, 6.8;N,25.9. IR data: 2506 (YB-H). MS: mlz 659 (M+ 1). Synthesis of [TpButlZnH. THF (50 mL) was added dropwise to a mixture of T1[TpBUt] (1.0g, 1.7mmol) and ZnHz (180 mg, 2.7 mmol), resulting in the immediate formation of a black deposit of T1 metal. The mixture was stirred for 30 h at room temperature and filtered. The filtrate was concentrated to ca. 10 mL and placed at 0 "C giving colorless crystals. The crystals of [TpBUt]ZnHwere isolated by filtration and dried in uacuo (0.10g). Further crops of [TpBUtlZnHwere obtained from the mother liquor by a similar procedure. Total yield of [TpBU'lZnH: 0.32g (42%). Anal. Calcd for [TpBU'lZnH:C, 56.3; H, 7.9;N, 18.9. Found: C, 55.9;H, 7.9;N, 19.2. IR: 2500 (YB-H), 1770 (YZn-H). MS: mlz 447 (M+ + 1). [TpBUtlZnD was prepared analogously using ZnDz. Yield of [TpBUt]ZnD:40%. IR: 1270 ( Y Z ~ - D ) . MS: mlz 448 (M+ + 1). Reaction of [TpBUtlZnH with COB. A solution of [TpBU']]ZnH (45mg, 0.1 mmol) in benzene (1 mL) was treated with COz (1 atm) and heated at 50 "C for 4 days. The volatile components were removed under reduced pressure giving

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[TpBUtlZn(ql-OzCH) as a white solid (45 mg, 92%). Anal. Calcd for [TpBUtlZn(ql-OzCH):C, 53.7; H, 7.2; N, 17.1. Found: C, 53.1;H, 6.9; N, 16.4. IR: 2505 (YB-H), 1655 ( Y - C~O J , 1290 mlz 491 (M+ 1). [TpBut]Zn(q1-0~13CH) and (vsm ~ 0 ~ )MS: . [TpBUt]Zn(ql-OzCD) were prepared in a similar fashion using the appropriately labeled materials. IR data for [TpBUt]13c%),1270 (vSym 13C02). Zn(ql-0~~~CH 2505 ) : (YB-H), 1620 (Y" IR data for [TpBUtlZn(ql-OzCD): 2510 (YB-H), 2120 (YC-D), 1645 ( ~ a s y mC O ~ ) , 1280 ( ~ s y mC O ~ ) . Reaction of [TpBu'lZnH with C a . A solution of [TpBu']ZnH (20 mg, 0.04 "01) in &-benzene (1mL) was treated with C2H4 (1 atm) and heated at 120 "C for about 20 days. No reaction was observed, except for slight decomposition of [TpBut]ZnH. Reaction of [TpButlZnH with Has. A solution of [TpBUt]]ZnH (40 mg, 0.09 mmol) in benzene (1mL) was treated with HzS (1atm) and left at room temperature for 1h. The volatile components were removed under reduced pressure giving [TpBUtlZnSHas a white solid (40 mg, 93%). Anal. Calcd for [TpBUtlZnSH:C, 52.3; H, 7.4; N, 17.5. Found: C, 52.6; H, 7.3; N, 17.4. IR: 2500 ( Y B - H ) . MS: mlz 479 (M+ 1). Reaction of [TpButlZnHwith MesSiOH. A solution of [TpBUtlZnH (40 mg, 0.09 mmol) in benzene (1mL) was treated with Me3SiOH (10 pL), and heated at 70 "C for 3 days. The volatile components were removed under reduced pressure as a white solid (45 mg, 93%). Anal. giving [TpBUtlZnOSiMe3 Calcd for [TpBUt]ZnOSiMe3:C, 53.8; H, 8.1; N, 15.7. Found: C, 58.7; H, 7.3; N, 15.8. IR data: 2490 (YB-H). Reaction of [TpBUtlZnC1 with KOSiMes. KOSiMe3 (100 (250 mg, mg, 0.8 mmol) was added t o a solution of [TpButlZnC1 0.5 mmol) in benzene (20 mL). The mixture was shaken at room temperature for 15 min and filtered. The colorless crystals were isolated and demonstrated to be [TpBUtlZnOSiMe3 by 'H NMR spectroscopy. Reaction of [TpB"']ZnHwith MeCOa. A solution of [TpBUt]ZnH (20 mg, 0.04 mmol) in benzene (1mL) was treated with MeCOzH (0.05 mmol) and left at room temperature for 10 min. The reaction was monitored by 'H NMR spectroscopy which demonstrated the formation of [TpBUtlZn(ql-OzCMe) and Hz. Anal. Calcd for [TpBut1Zn(q1-OzCMe):C, 54.6; H, 7.4; N, 16.6. Found: C, 54.6; H, 7.2; N, 16.2. Reaction of [TpBU*lZnH with RX (R = Me, PhCHg). A solution of [TpBut]ZnH(20 mg, 0.04 mmol) in &-benzene (0.7 mL) was treated with RX (R = Me, PhCHz; 0.05 mmol) and left at room temperature. The reactions were monitored by 'H NMR spectroscopy which demonstrated the formation of [TpBUt]ZnIand RH (R = Me, PhCHz) over a period of days. The formation of [TpBUt]ZnIand RD (CHsD, PhCHZD) was observed for the reaction of [TpBUtlZnDwith RI. Reaction of [TpBUt]ZnH with MesSiX (X = C1, I). A solution of [TpBUt]znH (20 mg, 0.04 mmol) in &-benzene (1mL) was treated with Me3SiX (X = C1, I; 0.05 mmol) and heated at 70-80 "C for a period of days. The reactions were monitored by 'H NMR spectroscopy which demonstrated the formation of [TpBU'lZnX(X = C1, I). Reaction of [TpBUt]ZnH with MeCOCl. A solution of [TpBUt]ZnH (20 mg, 0.04 mmol) in benzene (1mL) was treated with MeCOCl(O.05 mmol) and left at room temperature for 1 day. The reaction was monitored by lH NMR spectroscopy which demonstrated the formation of [TpBUt]ZnC1 and MeCHO. Reaction of [TpBUt]ZnH with 12. A solution of [TpBUt]ZnH (20 mg, 0.04 mmol) in &-benzene (15 mL) was treated with IZ (10 mg, 0.04 mol). The reaction was monitored by 'H NMR spectroscopy which demonstrated the formation of [TpButlZnI immediately. Synthesis of [BpBUt]ZnMe.A solution of MezZn (2.5 g, 10% wlw in pentane, 2.6 mmol) was added dropwise to a solution ofTl[BpBut](0.5 g, 1.1mmol) in THF (15 mL), resulting in the formation of a black deposit of T1 metal. The mixture was stirred for 2 h at room temperature and filtered. The solvent was removed from the filtrate under reduced pressure, extracted into pentane (20 mL), and filtered. The filtrate was concentrated t o ca. 10 mL and placed at 0 "C giving a crop of

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colorless crystals. The crystals of [BpBUtlZnMewere isolated by filtration and dried in vacuo (200 mg, 54%). Anal. Calcd for [BpBUtlZnMe:C, 53.1 H, 8.0; N, 16.5. Found: C, 53.3;H, 7.6; N, 15.8. IR data: 2434 (VB-H). MS: mlz 339 (M+ 1). Synthesisof [BpBUtlZnEt. A solution of EtzZn (4.5 g, 15% wlw in hexane, 5.5 mmol) was added dropwise to a solution of T1[BpBUtl(2.0 g, 4.3 mmol) in THF (30 mL), resulting in the immediate formation of a black deposit of Tl metal. The mixture was stirred for 30 min at room temperature and filtered. The solvent was removed from the filtrate under reduced pressure, extracted into pentane (30 mL), and fdtered. The filtrate was concentrated to ca. 10 mL and placed at 0 "C giving a crop of colorless crystals of [BpBUt]ZnEt.The crystals were isolated by filtration and dried in vacuo (800 mg, 53%). Anal. Calcd for [BpBUtlZnEt:C, 54.4; H, 8.3; N, 15.8. Found: C, 54.7; H, 7.8; N, 15.6. IR data: 2440 (YB-H). MS: mlz 353 (M+ 1). Synthesis of [BpButlZnBut. A solution of ButzZn (8 mL, 0.2 M in pentane, 1.6 mmol) was added dropwise to a solution (0.5 g, 1.1mmol) in THF (30 mL), resulting in the of T1[BpBUtl formation of a black deposit of Tl metal. The mixture was stirred for 1h at room temperature and filtered. The solvent was removed from the filtrate under reduced pressure, extracted into pentane (20 mL), and filtered. The filtrate was concentrated to ca. 10 mL and placed at 0 "C giving a crop of colorless crystals of [BpBUt]ZnBut.The crystals were isolated by filtration and dried in uacuo (240 mg, 57%). Anal. Calcd for [BpBut]ZnBut:C, 56.6 H, 8.7; N, 14.9. Found: C, 56.6; H, 8.4; N, 15.1. IR data: 2446 (%-HI. MS: mlz 381 (M+ 1). Synthesis of { [BpBut]Zn(p-OH)}~. A solution of [BpBut]ZnEt (210 mg, 0.59 mmol) in THF (10 mL) was treated with HzO (11pL, 0.60 mmol). The mixture was stirred for 10 min at room temperature and filtered. The filtrate was removed under reduced pressure giving {[BpB"'lZngl-OH)}3 (250 mg, 44%). Anal. Calcd for {[BpBUt]Zngl-OH)}3:C, 49.2; H, 7.4; N, 16.4. Found: C, 50.1; H, 7.2; N, 15.9. IR data: 3611 (YO-H) and 2444 (--HI. The isotopomer {[BpBUtlZn~-OD)}~ was prepared by the corresponding reactions of [BpButlZnEtwith DzO. IR data for {[BpButlZngl-OD)}3:2670 (YO-D). Synthesis of (HB(OMe)(3-Butpz)a}ZnEt. A solution of [BpBUtlZnEt (100 mg, 0.3 mmol) in benzene (1mL) was treated with excess (CHzO), and left at room temperature for 2 days. The mixture was filtered, and the volatile compounds were removed under reduced pressure giving {HB(OMe)(3-Butpz)z}ZnEt (ca. 90 mg, 78%). Anal. Calcd for {HB(OMe)(3-Butpz)z}Z n E t C, 53.2; H, 8.1; N, 14.6. Found: C, 51.6; H, 7.8; N, 13.8. IR data: 2440 (vB-H). MS: mlz 383 (M+ 1). Synthesis of {HB(OEt)(3-Butpz)2}ZnEt.A solution of [BpBUtlZnEt (100 mg,0.3 mmol) in benzene (1mL) was treated and left at room temperature. with MeCHO (30 pL, 0.53 "01) The volatile compounds were removed under reduced pressure giving {HB(OEt)(3-Butpz)z}ZnEt (ca. 95 mg, 80%). Anal. Calcd for {HB(OEt)(3-Butpz)z}ZnEt: C, 54.4; H, 8.4; N, 14.1. Found: C, 53.6; H, 7.8; N, 14.2. IR data: 2440 (YB-H). MS: mlz 396 (M+ 1). Synthesis of (HB(OW)(3-Butpz)z}ZnEt.A solution of [BpBU']ZnEt(100 mg, 0.3 mmol) in benzene (1mL) was treated with MezCO (25 pL, 0.44 mmol) and left at room temperature for several days. The volatile compounds were removed under reduced pressure giving {HB(OPri)(3-Bu~z)~}ZnEt (ca. 100 mg, 81%). Anal. Calcd for {HB(OPr')(3-Butpz)~}ZnEtC, 55.4; H,8.6;N,13.6. Found C,55.5;H,8.5;N,14.1. IRdata: 2445 (YB-H). MS: mlz 411 (M+ 1). Synthesisof [BpBUt]Zn(q2-02CMe). A solution of [BpBU']]ZnEt (100 mg, 0.3 mmol) in &-benzene (0.7 mL) was treated with MeCOzH and left at room temperature for 1 day. The reaction was monitored by 'H NMR spectroscopy which demonstrated the formation of [BpButlZn(q2-O~CMe).The volatile compounds were removed under reduced pressure giving [BpBUt]Zn(v2-0&Me) (ca. 80 mg, 70%). IR data: 2448 (VB-H) and 1580 (YCOJ. MS: mlz 383 (M+ 1). X-ray Structure Determination of [TpM"BlZnMe.Crystal data, data collection, and refinement parameters for [TpM%I-

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Looney et al.

288 Organometallics, Vol. 14,No.1, 1995 Table 12. Crystal and Intensity Collection Data [TPrIZnMe formula fw lattice cell consts

[TpMe2]2Zn

[TpB"']zn(~~-oAcKCd-I,j) [Tpe"']ZnNCS

C ~ ~ H ~ ~ N I Z B ZC29H43N6BOzZn Z~ 583.90 659.8 orthorhombic triclinic

Ci6HzN6Ba 377.6 orthorhombic

7.831(2) 13.376(4) 18.877(4) 90.0 ufdeg 90.0 Bid% 90.0 ?J/deg VIA3 1977(1) 4 radiation (UA) Mo Ka (0.710 73) Pcmn (No. 62) space group @(calcd)/g~ m 1.27 - ~ p(Mo Ka)Icm-l 12.9 3-50 28 rangeldeg 1141 [F > 6o(F)] no. of data 128 no. of params goodness of fit 1.39 0.0454 R 0.0580 R W alA blA CIA

8.806(1) 10.195(2) 10.800(2) 63.46(2) 85.11(2) 79.63(1) 853(1) 1 M_o K a (0.710 73) P1 (No. 2) 1.28 7.6 3-55 3175 [F > 6o(F)1 231 1.37 0.0391 0.0543

10.433(1) 15.832(2) 19.292(3) 90.0 90.0 90.0 3 186(1)

4 Mo Ka (0.710 73) P2lcn (No. 33) 1.22 8.3 3-52 2081 [F > 6o(F)] 314 1.38 0.0456 0.0548

[TpBY']ZnH

[BpB"]ZnBu'

{ [BpBU'lZn@-OH)}3

monoclinic

monoclinic

monoclinic

orthorhombic

9.703(2) 17.001(4) 16.582(3) 90.0 95.08(1) 90.0 2725(1) 4 Mo K a (0.710 73) P21h (No. 14) 1.21 10.3 3-45 2483 [F > 6o(F)1 294 1.20 0.0386 0.0477

8.262(1) 15.465(2) 9.696(2) 90.0 100.76(2) 90.0 1217(1) 2 Mo Ka (0.710 73) Pn (No. 7) 1.22 10.6 3-45 2100 [F > 6o(F)] 266 1.55 0.0410 0.0589

14.912(7) 8.556(2) 18.482(5) 90.0 112.86(3) 90.0 2173(2) 4 Mo K a (0.710 73) F211n (No. 14) 1.17 11.7 3-52 1948 [F > 6u(F)1 225 1.21 0.054 0.0682

12.302(2) 20.057(6) 22.1 lO(2) 90.0 90.0 90.0

5455(2) 4 Mo K a (0.710 73) Pc21n (No. 33) 1.25 13.8 3-50 2946 [F > 5a(F)] 563 1.20 0.072 0.0637

P2lcn (No. 33), and inversion of configuration indicated the ZnMe are summarized in Table 12. A single crystal of correct absolute structure. The centrosymmetric alternative [TpMe2]ZnMewas mounted in a glass capillary and placed on a Nicolet R3m difiactometer. The unit cell was determined was ruled out since the contents of the asymmetric unit were by the automatic indexing of 25 centered reflections and not related by a mirror plane. confirmed by examination of the axial photographs. Intensity X-ray Structure Determination of [TpWJZnNCS.Crysdata were collected usin graphite monochromated Mo Ka tal data, data collection, and refinement parameters are X-radiation (A = 0.710 73 ). Check reflections were measured summarized in Table 12, and the general procedure is as every 100 reflections, and the data were scaled accordingly described for [TpMe21ZnMe.Systematic absences were consisand corrected for Lorentz, polarization, and absorption effects. tent uniquely with the space group P21/n (No. 14). The structure was solved using direct methods and standard X-ray Structure Determinationof [BpBUt]ZnBut. Crysdifference map techniques on a Data General NOVA 4 tal data, data collection, and refinement parameters are computer using SHEIXTL.60 Systematic absences were consummarized in Table 12, and the general procedure is as sistent with the space groups Pcmn (No. 62) or Pc21n (No. 33), described for [TpMea]ZnMe.Systematic absences were consisbut consideration of the E-value statistics suggested the choice tent uniquely with the space group P2lln (No. 14). Pcmn (No. 62). Hydrogens on carbon were included in X-ray Structure Determination of { [BflUtlZn(lr-OH)}s, calculated positions (&-H = 0.96 A; U d H ) = 1.2Uiao(C))X-ray Structure Determination of [TpM*12Zn.Crystal Crystal data, data collection, and refinement parameters are data collection, and refinement parameters are summarized summarized in Table 12, and the general procedure is as in Table 12, and the general procedure is as described for described for [TpMBzlZnMe.Systematic absences were consis[TpMez]ZnMe. Systematic absences were consistent with the tent with the space groups Pc2ln (No. 33) and Pcmn (No. 62). space groups P1 (No. 1)and P1 (No. 2), but the structur? was The structure was successfully solved in Pc2ln (No. 33), and successfully solved in the centrosymmetric alternative P1 (No. inversion of configuration indicated the correct absolute 2). structure. The centrosymmetric alternative was ruled out X-ray Structure Determinationof ["pBu'lZnH. Crystal since the contents of the asymmetric unit were not related by data, data collection, and refinement parameters are suma mirror plane. marized in Table 12, and the general procedure is as described for [TpMe2]ZnMe.Systematic absences were consistent with Acknowledgment. Acknowledgment is made to the the space groups Pn (No. 7) and P2/n (No. 13). Since the National Science Foundation (Grant CHE 93-00398)for molecule possesses neither a 2-fold axis nor inversion center, support of this research. M.C. acknowledges support the space group Pn (No. 7) was selected. Inversion of configuthrough the NSF REU Program at Columbia University. ration indicated the correct absolute structure. X-ray Structure Determination of [TpBUtlZn(ql-O~SupplementaryMaterial Available: Complete tables of CMe)C&e. Crystal data, data collection, and refinement atom coordinates, thermal parameters, bond distances and parameters are summarized in Table 12, and the general angles, and crystal data, data collection, and refinement procedure is as described for [TpMez]ZnMe, Systematic abparameters and ORTEP diagrams for [TpMe2]ZnMe,[TpMe2]2sences were consistent with the space groups P2lcn (No. 33) Zn, and [TpBU']ZnNCS(19 pages). Ordering information is and Pmcn (No. 62). The structure was successfully solved in given on any current masthead page. Tables for [TpBUt]ZnH," [TpButlZn(ql-O~CMe)," [BpBUt]ZnBut,Gb and {[Bpeut]Zn~-OH)}~6b (60)Sheldrick, G. M. SHELXTL, An Integrated System for Solving, were deposited with the original publications. Refining and Displaying Crystal Structures from Diffraction Data;

1

University of Gijttingen, Gijttingen, Federal Republic of Germany, 1981.

OM9406941

Monomeric Alkyl and Hydride Derivatives of Zinc Supported by Poly

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