J . Am. Chem. SOC.1993,115,8493-8494
Cationic do Metal Alkyls Incorporating Tetraaza-Macrocycle Ancillary Ligands. Synthesis and Reactivity of (Mestaa)M(R)+ and (Me@en)M(R)+ (M = Zr, Hf) Complexes
8493
3-Li2(OEtz)2
-
Roger Uhrhammer, David G. Black, Thomas G. Gardner, Jeffrey D. Olsen, and Richard F. Jordan'
2 RLi
Department of Chemistry University of Iowa Iowa City, Iowa 52242
/R
(Me8taa)M 'R
-- -
Me4taenHz + ZrR4
-2 RH
4-Hz
- RH - NMezPh
-
R
7b
1; X = CI, CHzPh
=
u,
Me8taaz'
N'
'N
-N = n N N , Me4taen2'
4; N
Our initial studies have focused on Mestaa2- (3)4 and Me4taen2- (4)5 as representative N4-macrocycles. Neutral Zr and Hf (Mestaa)M(R)z complexes (5b,c; 6b,c) were prepared via anion metathesis (eq 1).2~6 Analogous (Medtaen)Zr(R)~ complexes (7b,d) were prepared by direct alkane elimination (eq 2). (Mestaa)Zr(CHzPh)z (Sd, 87%) was prepared by a reaction analogous to eq 2. Cis orientations of the halide/alkyl ligands and "saddle" conformations of the Mestaaz- ligands are assumed (1) Jordan, R. F. Adu. Organomet. Chem. 1991, 32, 325. (2) (a) Yang, C. H.; Ladd, J. A.; Goedken, V. L. J . Coord. Chem. 1988, 18, 317. (b) Floriani, C.; Ciurli, S.;Chiesi-Villa, A.; Guastini, C. Angew. Chem., Inr. Ed. Engl. 1987, 26, 70. (c) DeAngelis, S.; Solari, E.; Gallo, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli, C. Inorg. Chem. 1992, 32, 2520. (d) Review; Cotton, F. A.; Czuchajowska, J. Polyhedron 1990, 21, 2553. (3) (a) Brand, H.; Arnold, J. J . Am. Chem. SOC.1992, 114, 2266. (b) Arnold, J.; Hoffman, C. G. J . Am. Chem. SOC.1990, 112, 8620. (c) Kim, H.-J.; Whang, D.; Kim, K.; Do, Y. Inorg. Chem. 1993,32,360. (d) Shibata, K.; Aida, T.; Inoue, S.Chem. Leu. 1992, 1173. (e) Schavarien, C. J.; Orpen, A. G. Inorg. Chem. 1991, 30, 4968. (4) (a) Goedken, V. L.; Pluth, J. J.; Peng, S.-M.;Bursten, B. J. Am. Chem. SOC.1976, 98, 8014. (b) Goedken, V. L.; Weiss, M. C. Inorg. Synth. 1980, 20, 115. (c) Cutler, A. R.; Alleyne, C. S.; Dolphin, D. Inorg. Chem. 1985, 24, 2276. (d) Place, D. A.; Ferrara, G. P.; Harland, J. J.; Dabrowiak, J. C. Heterocycl. Chem. 1980, 17, 439. ( 5 ) (a) Truex, T. J.; Holm, R. H. J . Am. Chem. SOC.1972,94,4529. (b) Kim, J.-H.; Everett, G. W., Jr. Inorg. Chem. 1979, 28, 3145. (6) Full experimental details and characterization data for 5-16are given in the supplementary material. For SC, solid ether-free MeLi is required to avoid ligand-induced migration of a Zr-Me to an electrophilic imine carbon of the macrocycle (see ref 2b); this results in the low yield (15%).
-
(2)
R
for 5 and 6 on the basis of structural data for 1.2 For Me4taen2complexes 7b,d, distinct 'H NMR resonances for the endo- and exo-Hs of the -CH2CH2- linkers indicate cis structures, which is confirmed by X-ray crystallography for 7d.l Protonolysiss of 5b with [HNMezPh] [B(C6F5)4] ( ~ 3 in ) ~C2D2C14 yields 1 equiv of SiMe4 and free NMe2Ph, and [(Mestaa)ZrCH1SiMe31[B(CsF5)4] (9b,80%NMR, eq 3) in situ. The
5b 5d
3; NN
7
(Me&en)Zr\
7b R CHzSiMe,, 76% 74 R-CHzPh, 07%
+ HNMe2Ph*
\R
(Me4taa)MXz
--
5b M = Zr,R CHzSiMe3,66% 5C ' R CH3, 15% 6b M Hf R CHzSiMe3,60% 6C " R-CH3, 76%
(N4)M'
2
,ci (Me8taa)M 'Cl
5a,M Zr, 95% 6a, M Hf, 71%
Received April 26, 1993 Electrophilic do Cp2M(R)+ complexes have been exploited in stoichiometric and catalytic reactions, including olefin polymerizations.' A key feature of these compounds is the Cp2M framework that (i) forces the vacant coordination sites to be cis to the reactive M-R bond, thus promoting insertion and a-bond metathesis reactivity, and (ii) can be extensivelymodified, allowing tuning of steric, chirality, and electronic properties. A current challenge is to design new classes of cationic early metal alkyl complexes that incorporate these features but are based on ancillary ligands which are more easily modified than Cp ligands and which give rise to improved/complementary reactivity. Goedken and Floriani have prepared a series of cis-(Me4taa)MX2complexes (1) (M = Ti, X = C1; M = Zr, X = C1, CHzPh),z and Arnold has pioneered the chemistry of related porphyrin complexes,including ci~-(oEP)ZrR2.~ These authors have noted the analogy between Cp2M and (N4-macrocyc1e)Mcompounds. Here we describe the synthesis and chemistry of a series of reactive cationic do (N4-macrocycle)M(R)+ complexes (2).
-
Liz(OEtz)p[Me&aa]+ MC14(THF),
6c
0
+ (NdM-R
(3)
M = Zr, N4 = Mestaa, R = CHzSiMe3 R = CH2Ph 9d ' lob N4 = Me4taen, R = CH2SiMe3 R = CH3 1 1 M ~ = Hf, N4 = Me8-,
Sb
counterion = [B(C,F,),T
NMR spectrum of 9b contains a ZrCH2 resonance at 6 53.0, which is downfield from the corresponding resonance of 5b (6 43.8). The cationic Hf methyl complex [(Mestaa)HfCH3][B(C6F5)4] ( l l c ) was generated in situ (87% NMR) in a similar manner from 6c (6 Hf-CH3 46.6,vs 33.3 for 6c). Reaction of 7b with 8 in benzene yields a red oil which can be separated and vacuum dried, yielding [ (Me4taen)ZrCH2SiMe3][ B(CaF5)4] (lob) as a golden brown solid (56%, 6 ZrCH2 64.1,vs 50.4 for 7b). The extent of anion or solvent (CD2C12 or C2DzC14) coordination to these base-free cations is unknown at present; however, such interactions must be weak as 9b,lob,and l l c all exhibit effective C b symmetry on the NMR time scale (23 OC).lO Cationic benzyl complexes are generated in situ by analogous protonolysis reactions. Reaction of 5d with 8 yields 1 equiv of toluene and free NMe2Ph and [(Mestaa)Zr(q2-CH2Ph)][B(CbFs)d] (9d,>80% NMR). A high-field ortho phenyl *H (7) Details of the X-ray structural analyses of 7d and 13 will be presented in a full report. (8) (a) Hlatky, G. G.; Turner, H. W.; Eckman, R. R. J . Am. Chem. Soc. 1989, 1 1 1 , 2728. (b) Hlatky, G. G.; Eckman, R. R.; Turner, H. W. Organometallics 1992,II. 1413. (c) Bochmann, M.; Wilson, L. M. J . Chem. SOC.,Chem. Commun. 1986, 1610. (d) Bochmann, M.; Lancaster, S . J. Organometallics 1993, 12, 633. (e) Lin, Z.; Le Marechal, J.; Sabat, M.; Marks, T. J. J. Am. Chem. SOC.1987,109,4127. (f') Yang, X.; Stern, C. L.; Marks, T. J. Organometallics 1991, 10, 840. (9) Turner, H. W.; Hlatky, G. G. Eur. Pat. Appl. 0 277 004, 1988. (10) A cis-(Na-macrocycle)M(X)(Y) complex has C, symmetry (see 1). Rapid site exchange of the X and Y ligands, e.g., by Y- dissociation to yield a configurationally labile (N,-macrocycle)M(X)+ species, results in effective C , symmetry. Rapid rotation of the macrocycle about Zr must also be considered, as (Me~taa)Zr(CH2SiMe3)Clexhibits effective C, symmetry (by NMR) in C2D2C140rC6Ds solution (23 "C). Low-temperature NMRstudies are in progress.
0002-7863/93/ 1515-8493$04.00/0 0 1993 American Chemical Society
Communications to the Editor
8494 J. Am. Chem. SOC.,Vol. 115, No. 18, 1993 NMR resonance (6 5.49), and a large J c ~ ( c H 2 value ) (137 Hz) indicate that 9d contains a distorted q2-benzyl ligand." +rSiMe, (WZr
+
L
-
+rSiMe, (N4)Zr
L'
(4)
-
12a N, = Me8taa, L = PMePh 12b L THF 12c L L CH3CN 13 N, I Me4taen, L = THF counterion = [BPhJ
Base-free (N4-macrocycle)M(R)+cations form isolable Lewisbase adducts (eq 4). The reaction of 5b with [HNBu3] [BPh,] and 1 equiv of PMezPh (C2H4C12, 23 "C) yields [(Mestaa)Zr(CHzSiMe3)(PMezPh)] [BPh4] (12a, 77% isolated). The lack of J(31P-CHzSi) coupling in the 'Hand 13C NMR spectra (CDzC12, 23 "C) of 12a and the effective CZ,symmetry implied by these spectra indicate that PMezPh exchange is rapid on the NMR time scale. Analogous labile T H F and CH3CN adducts 12b,c were generated in clean NMR scale reactions. Similarly, the reaction of 7b with [ H N B u ~[BPh,] ] in the presence of T H F yields the labileTHF adduct [(Me4taen)Zr(CHzSiMe3)(THF)] [BPhd] (13, 60% isolated). The analogous B(CaF5)4- salt is formed by addition of T H F to preformed lob. Key NMRdata for 13 include IH resonances for coordinated T H F (6 3.9 1,1.99) and a low-field Zr-CH2Si 13C resonance (6 56.2). The cis structure of 13 was confirmed by X-ray ~rystallography.~ The reactions of representative (N4-macrocycle)M(R)+ species with unsaturated hydrocarbons have been explored for comparison to reactions of CpZZr(R)+ species. Cationic Hf methyl complex l l c reacts with excess 2-butyne (CHZCl2, 23 OC, 12 h) to yield the double insertion product [ (Megtaa)HfCMe=CMeCMe=CMe2][B(C6F5)4] (14) as a golden brown solid (eq 5 , 72% isolated). A similar reaction was reported for CpzZr(CHs)+ species.12 The IHNMRspectrumof 14 (CD2Cl2, 23 "C) includes five Me resonances and establishes that 14 has effective Cb symmetry. The 13CNMR spectrum contains four alkenyl carbon resonances (6 214.0 (Hf-C), 147.1, 141.6, 139.1). There is no evidence for coordination of the pendant olefin to Hf or rearrangement of 14 to a pentadienyl species, as observed for analogous CpzZr(CMe=CMeCMe=CMez)+ species.I2 Cation l l c inserts l-(MesSi)-l-propyne (
