Formation of coordinated RZn(macrocycle)+ cations and organozincate anions from reactions of organozinc compounds and macrocycles

Article abstract of DOI:10.1021/om0102798

An RZnZ compound (R = alkyl) and a macrocycle react in benzene to form RZn(macrocycle)⁺ ions when the macrocycle is an effective coordinator for RZn⁺ and Z^- can exist as the anion or become attached to an organometallic acceptor to form an organometalate anion. R₂Zn and R₃Al form RZn(macrocycle)⁺R₄Al^- with 14N4 (1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane) 15N5 (1,4,7,10,13-pentamethyl-1,4,7,10,13-pentaazacyclopentadecane), 2,1,1-cryptand, or 2,2,1-cryptand but not with 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclo-octadecane, 2,2,2-cryptand, 15-crown-5, or 18-crown-6. RZnZ, R₂Zn, and 14N4 form RZn(14N4)⁺R₂ZnZ^- when Z is Cl, Br, I, or 3,5-di-tert-butylphenoxy but not when Z is tert-butoxy. Various combinations of RZnZ with Z = Cl, Br, I, 2,6-di-tert-butylphenoxy, or 3,5-di-tert-butylphenoxy and 14N4, 15N5, 2,1,1-cryptand, or 2,2,1-cryptand form RZn(macrocycle)⁺Z^- solids; solids do not form when Z is methoxy or tert-butoxy nor when the macrocycle is 12-crown-4, 15-crown-5, or 18-crown-6.

Full text of DOI:10.1021/om0102798

4018
Organometallics 2001, 20, 4018-4023
F or m a tion of Coor d in a ted RZn (m a cr ocycle)+ Ca tion s
a n d Or ga n ozin ca te An ion s fr om Rea ction s of Or ga n ozin c
Com p ou n d s a n d Ma cr ocycles
Ronaldo M. Fabicon and Herman G. Richey, J r.*
Department of Chemistry, The Pennsylvania State University,
University Park, Pennsylvania 16802
Received April 3, 2001
An RZnZ compound (R ) alkyl) and a macrocycle react in benzene to form RZn(macrocycle)+
ions when the macrocycle is an effective coordinator for RZn+ and Z- can exist as the anion
or become attached to an organometallic acceptor to form an organometalate anion. R2Zn
and R3Al form RZn(macrocycle)+R4Al- with 14N4 (1,4,8,11-tetramethyl-1,4,8,11-tetraazacy-
clotetradecane), 15N5 (1,4,7,10,13-pentamethyl-1,4,7,10,13-pentaazacyclopentadecane), 2,1,1-
cryptand, or 2,2,1-cryptand but not with 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclo-
octadecane, 2,2,2-cryptand, 15-crown-5, or 18-crown-6. RZnZ, R2Zn, and 14N4 form RZn-
(14N4)+R2ZnZ- when Z is Cl, Br, I, or 3,5-di-tert-butylphenoxy but not when Z is tert-butoxy.
Various combinations of RZnZ with Z ) Cl, Br, I, 2,6-di-tert-butylphenoxy, or 3,5-di-tert-
butylphenoxy and 14N4, 15N5, 2,1,1-cryptand, or 2,2,1-cryptand form RZn(macrocycle)+Z-
solids; solids do not form when Z is methoxy or tert-butoxy nor when the macrocycle is 12-
crown-4, 15-crown-5, or 18-crown-6.
In contrast to formation of RMg(macrocycle)+ and
Resu lts a n d Discu ssion
organomagnesate ions from a range of R2Mg compounds
and macrocycles (e.g., eq 1),1 similar reactions of R2Zn
The solvent was benzene (or benzene-d6), and, except
where noted, equimolar amounts of reactants were used.
NMR observations (at ca. 23 °C) were not dependent
on time (spectra taken soon after preparation of solu-
tions, typically 1 h, and 1-2 days later were essentially
identical) nor significantly on concentration in the range
(0.1-0.5 M) that was used.
2R2Mg + macrocycle f
RMg(macrocycle)+ + R3Mg- (1)
compounds have been found with only a few macrocycles
particularly effective at coordinating RZn+ and R groups
particularly effective at stabilizing R3Zn-.2 The objective
of this study was to determine if RZn(macrocycle)+ and
organometalate ions could be synthesized from (1)
reactions in which, besides R2Zn and a macrocycle, a
second organometallic compound is present that might
be a more effective acceptor of an anion than is R2Zn or
from (2) reactions of macrocycles and compounds RZnZ
from which Z, a group other than alkyl or aryl, might
be more easily transferred to an acceptor molecule to
form an anion. Because of the many similarities of
organozinc and organomagnesium compounds, it is
relevant that reactions4 of Grignard reagents (RMgX)
and 14N4 (14N4 ) 1,4,8,11-tetramethyl-1,4,8,11-tet-
raazacyclotetradecane) lead to RMg(14N4)+, XMg-
(14N4)+, RMgX2-, and X-, the composition depending
on X (Cl, Br, or I) and the RMgX/14N4 ratio.
R2Zn , R3Al, a n d a Ma cr ocycle.5 In these experi-
ments R3Al was added as a possibly more effective “R-”
acceptor than R2Zn. Solutions prepared from R2Zn and
R3Al (R ) Me, Et, or i-Bu) without a macrocycle show
1
only one set of H NMR absorptions for R. The species
in solution are R2Zn and R3Al, however, since (when
equimolar amounts are used) the absorptions lie exactly
midway between those of these compounds. As expected,
exchange of all R groups is sufficiently rapid relative to
the NMR time scale to lead to single sets of R absorp-
tions. A solution of a macrocycle and either R2Zn or R3-
Al exhibits only a single set of R absorptions. Depending
on the macrocycle, however, combining a macrocycle,
R2Zn, and R3Al in benzene results (Table 1) in one of
three behaviors: (1) formation of a second liquid phase
that contains principally RZn(macrocycle)+R4Al- (eq 2);
R2Zn + R3Al + macrocycle f
RZn(macrocycle)+ + R4Al- (2)
* To whom correspondence should be addressed. E-mail: hgr@
chem.psu.edu.
(1) Squiller, E. P.; Whittle, R. R.; Richey, H. G., J r. J . Am. Chem.
Soc. l985, 107, 432. Richey, H. G., J r.; Kushlan, D. M. J . Am. Chem.
Soc. l987, 109, 2510. Pajerski, A. D.; Parvez, M.; Richey, H. G., J r. J .
Am. Chem. Soc. l988, 110, 2660.
(2) Ref 3 and references therein.
(3) Tang, H.; Parvez, M.; Richey, H. G., J r. Organometallics 2000,
19, 4810.
a homogeneous solution of R2Zn and R3Al with R groups
not exchanging relative to the NMR time scale; (3) a
homogeneous solution of R2Zn and R3Al with R groups
(4) Pajerski, A. D.; Chubb, J . E.; Fabicon, R. M.; Richey, H. G., J r.
J . Org. Chem. 2000, 65, 2231.
(5) Some preliminary results were reported: Fabicon, R. M.; Pajer-
ski, A. D.; Richey, H. G., J r. J . Am. Chem. Soc. l991, 113, 639.
10.1021/om0102798 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 08/07/2001

Coordinated RZn(macrocycle)+ Cations
Organometallics, Vol. 20, No. 19, 2001 4019
Ta ble 1. Rea ction s in Ben zen e-d 6 of Tw o Or ga n om eta llic Rea cta n ts a n d a Ma cr ocyclea
reactant 1b
reactant 2
macrocyclec
ionic products
observationsd
Me2Zn
Et2Zn
i-Bu2Zn
Et2Zn
i-Bu2Zn
Et2Zn
Et2Zn
Et2Zn
Et2Zn
Et2Zn
Me3Al
Et3Al
i-Bu3Al
Et3Al
i-Bu3Al
Et3Al
Et3Al
Et3Al
Et3Al
Et3Al
Et3Al
Et2Zn
Et2Zn
Et2Zn
Et2Zn
Et2Zn
Bu2Zn
14N4
14N4
14N4
15N5
15N5
211C
221C
18N6
222C
18C6
15C5
14N4
14N4
14N4
14N4
14N4
14N4
MeZn(14N4)+Me4Al-
EtZn(14N4)+Et4Al-
i-BuZn(14N4)+i-Bu4Al-
EtZn(15N5)+Et4Al-
i-BuZn(15N5)+i-Bu4Al-
EtZn(211C)+Et4Al-
EtZn(221C)+Et4Al-
none
2 liquid phases
2 liquid phases
2 liquid phases
2 liquid phases
2 liquid phases
2 liquid phases
2 liquid phases
no Et exchange
no Et exchange
rapid Et exchange
rapid Et exchange
solution
solution
2 liquid phases
solution
no Et exchange
no Bu exchange
none
none
none
Et2Zn
EtZnCl
EtZnBr
EtZnI
EtZnOAr
EtZnO-t-Bu
BuZnO-t-Bu
EtZn(14N4)+Et2ZnCl-
EtZn(14N4)+Et2ZnBr-
EtZn(14N4)+Et2ZnI-
EtZn(14N4)+Et2ZnOAr-
none
none
a
b
The temperature is ca. 23 °C. Equimolar amounts of the macrocycle and of each organometallic reactant were used. Ar ) 3,5-di-
tert-butylphenyl. c 14N4 ) 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane, 15N5 ) 1,4,7,10,13-pentamethyl-1,4,7,10,13-pentaaza-
cyclopentadecane, 211C ) 2,1,1-cryptand, 221C ) 2,2,1-cryptand, 18N6 ) 1,4,7,10,13,16-hexamethyl-1,4,7,10,13,16-hexaazacyclooctadecane,
222C ) 2,2,2-cryptand, 18C6 ) 18-crown-6, 15C5 ) 15-crown-5. dHomogeneous solutions except where noted. When two liquid phases
are indicated, the ionic products are in the denser phase. Rapid exchange indicates that only one set of 1H NMR absorptions is observed
for R.
exchanging rapidly (as in the solutions without a
macrocycle).
relative to the NMR time scale) that reduce the sym-
metry.
13C NMR spectra of solutions prepared using 14N4
and 15N5 (1,4,7,10,13-pentamethyl-1,4,7,10,13-penta-
azacyclopentadecane) show the number of absorptions
expected (4 for 14N4, 2 for 15N5) if the Zn atom is
bonded identically to all N atoms. The spectrum of the
Et2Zn-Et3Al-211C solution, however, has seven ab-
sorptions of approximately equal intensity for the
cryptand, in contrast to the five found for free 211C and
expected if identical parts of the cryptand remain
identical in EtZn(211C)+. This observation indicates
that the Zn atom is bonded not symmetrically as in 1
but less symmetrically, most probably as in 2, a struc-
ture having seven environments for 211C carbons (the
symmetries of 1 and 2 are unchanged if the Zn atom
also is bonded to both oxygen atoms of the two-oxygen
bridge).9
(1) When two phases form, NMR spectra of prepara-
tions that use equimolar amounts of reactants show
most solute to be in the denser phase.6 Formation of
two phases, the denser containing the ionic species, has
been noted often when RMg(macrocycle)+ cations and
organometalate anions form in benzene.7 Several fea-
tures of NMR spectra indicate that a dense phase
contains principally RZn(macrocycle)+R4Al-. (1) 1H
NMR spectra have two sets of R absorptions with 1:4
intensities, and 13C NMR spectra also have two sets of
R absorptions. (2) The R-H absorption of the smaller set
is significantly upfield from that of R2Zn or R3Al alone.
In fact, most8 1H NMR absorptions assigned to the
cations in EtZn(14N4)+Et4Al- and EtZn(211C)+Et4Al-
are the same (within ca. 0.2 ppm) as those found for
these cations with a different anion.3 (3) The larger sets
1
of H and 13C absorptions of R show significant effects
due to coupling to 27Al. The 13C absorptions of the R-C’s
are six equally spaced lines (J ) 71-80 Hz), as expected
1
for interaction with the 5/2 spin of 27Al. The H NMR
absorptions of both the R- and â-H’s show significant
broadening and some fine structure due to coupling with
27Al. The 27Al NMR spectrum of the lower phase from a
Et2Zn-Et3Al-211C preparation has a single broad
absorption (half-height width 35 Hz) with some fine
1
structure (J ) 5.8 Hz) evident; H decoupling gives a
(2) Solutions containing R2Zn and R3Al but with R
groups not exchanging rapidly between these com-
pounds are indicated by H NMR spectra having two
sets of R absorptions, in 2:3 ratio when equimolar
amounts of reactants are used. Transient bridge-bond-
ing of the R-carbon of an R group to both a Zn atom
and Al atom must be responsible for the usually rapid
exchange of R groups between R2Zn and R3Al. Routine11
coordination to heteroatoms of the macrocycles must
singlet (half-height width 4 Hz). The excellent resolution
of the 27Al couplings indicates the Al atom to be in a
symmetrical environment, consistent with a R4Al- ion
that has no interactions (not formed and broken rapidly
1
(6) When the macrocycle is in excess, the upper phase has macro-
cycle absorptions.
(7) Organometallic ions in aromatic solvents often lead to such two-
phase behavior. Atwood, J . L. In Inclusion Compounds; Atwood, J . L.,
Davies, J . E. D., Macnicol, D., Eds.; Academic: London, 1984; Vol. 1,
Chapter 9.
(9) The zinc atom of an organozinc compound tends to bond to N
atoms rather than O atoms and to form four or five bonds rather than
a larger number.3,10
(10) Boersma, J . In Comprehensive Organometallic Chemistry;
Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon: Oxford,
l982; Chapter 4.
(8) The only absorption of RMg(14N4)+ or RZn(14N4)+ ions whose
position varies significantly with the anion is due to four H’s (NCHHCH2-
CHHN) that lie above one face of the 14N4, projecting into the solution
at a location providing the least hindered approach to the center of
positive charge.

4020 Organometallics, Vol. 20, No. 19, 2001
Fabicon and Richey
sufficiently lower the concentrations of free Et2Zn and
Et3Al (or the concentration of at least one of these) that
exchange becomes slow relative to the 1H NMR time
scale. As expected if some routine coordination is taking
place, the ethyl absorptions of both organometallics are
shifted somewhat upfield (e0.3 ppm) and the macrocycle
absorptions are shifted downfield (e0.3 ppm). Exchange
of free and coordinated macrocycles remains rapid
relative to the 1H NMR time scale, however, since 18N6
and 222C exhibit only the number of absorptions seen
for the free macrocycles (although the absorptions are
somewhat broad).
(3) 1H NMR spectra of some solutions have the single
sets of R absorptions seen in the absence of a macrocycle
(although the absorptions are somewhat broad at ambi-
ent temperature).12
The macrocycles leading to RZn(macrocycle)+R4Al-
are those particularly effective at coordinating with
RZn+.13 Macrocycles unable to effect this transformation
but able to coordinate significantly to R2Zn and R3Al
(or to at least one of these) lead to the solutions in which
R does not exchange rapidly. The macrocycles not
apparently even slowing the exchange have only oxygen
heteroatoms. As generally found for organozinc10 and
organoaluminum14 compounds, O atom donors are less
able than N atom donors to coordinate to R2Zn and R3Al
and, hence, less effectively slow R exchange.
RZn X, RZn OAr , or RZn OR ′ w ith R2Zn a n d 14N4.
Reactions of EtZnCl, EtZnBr, or EtZnOAr (Ar ) 3,5-di-
tert-butylphenyl) with Et2Zn and 14N4 furnish solutions
(Table 1) that contain essentially only EtZn(14N4)+ and
Et2ZnX- or Et2ZnOAr- (eq 3, Z ) X or OAr). A similar
RZnZ + R2Zn + 14N4 f RZn(14N4)+ + R2ZnZ- (3)
reaction of EtZnI leads to separation of a small, dense
liquid phase containing the corresponding (eq 3, Z ) I)
ions; 1H NMR spectra indicate most solute to be in this
lower phase. The structural assignments are based on
1
features of the NMR spectra. H NMR spectra of the
solutions and of the lower phase of the EtZnI reaction
(Figure 1) show two sets of ethyl absorptions with 2:1
intensities. The absorptions of the smaller ethyl set and
of 14N4 are close to those observed3 for EtZn(14N4)+
with a different anion. Characteristic of RZn(14N4)+
(and RMg(14N4)+) ions are (1) a triplet-appearing 14N4
absorption8 (δ 2.94 in Figure 1) that is at lowest field
and (2) R- and â-hydrogen absorptions of R upfield from
the corresponding absorptions of R2Zn (and R2Mg).3,4,15
F igu r e 1. 1H NMR (upper spectrum, 300 MHz) and 13C
(lower spectrum, 75 MHz) spectra of the lower liquid phase
containing EtZn(14N4)+Et2ZnI- that resulted from com-
bining equimolar amounts of Et2Zn, EtZnI, and 14N4 in
benzene-d6. Absorptions of Et2ZnI- are labeled A; all other
absorptions are of EtZn(14N4)+.
A
13C NMR spectrum (Figure 1) also has two sets of
ethyl absorptions.
Similar reactions of RZnO-t-Bu, R2Zn, and 14N4 do
not form ions. The H NMR absorptions of the solutions
are similar to those of the reactants. Solutions of
RZnOAr and RZnO-t-Bu were prepared (eq 4) from
reactions of R2Zn with the appropriate alcohol or phenol.
(11) “Routine” is used here to refer to coordination of one or two
heteroatoms of the macrocycle to the metal atom, coordination similar
to that by acyclic ethers and amines. Such coordinate bonds generally
form and break rapidly relative to the NMR time scale.
(12) A rotaxane of composition Et2Zn(18C6) is a component of
benzene solutions of Et2Zn and 18C6 [Chubb, J . E.; Richey, H. G., J r.
Organometallics 1998, 17, 3204]. The ethyl groups of the rotaxane must
participate in the exchange.
1
(13) 211C and 14N4 are known to coordinate to RZn+ more strongly
than do the all-oxygen crown ethers such as 15C5;3 221C and 15N5
should more resemble 211C and 14N4 than 18N6, 222C, or the all-
oxygen crown ethers.
R2Zn + R′OH f RZnOR′ + RH
(4)
RZnOR′ compounds exist in solution as oligomers10 from
which monomeric RZnOR′ perhaps can be abstracted
only with difficulty. RZnO-t-Bu therefore was generated
in situ by adding excess R2Zn to a solution containing
(14) Mole, T.; J effery, E. A. Organoaluminum Compounds; Else-
vier: Amsterdam, l972; Chapter 4.
(15) Pajerski, A. D. Ph.D. Dissertation, The Pennsylvania State
University, l990.

Coordinated RZn(macrocycle)+ Cations
Organometallics, Vol. 20, No. 19, 2001 4021
Ta ble 2. Rea ction s in Ben zen e-d 6 of a n
Or ga n ozin c Rea cta n t a n d a Ma cr ocyclea
reactantb
macrocyclec
result
BuZnX (X ) Cl, Br, or I)d
HexZnX (X ) Cl or Br)d
EtZnOAr
14N4
14N4
14N4
15N5
211C
221C
221C
221C
221C
18C6
18C6
18C6
15C5
15C5
15C5
12C4
precipitate
precipitate
precipitate
precipitate
precipitate
precipitate
precipitate
solution
solution
solution
solution
solution
BuZnX (X ) Cl, Br, or I)
EtZnOAr′
2-EtBuZnBrd
EtZnOAr′
EtZnO-t-Bu
EtZnOMe
BuZnX (X ) Cl, Br, or I)
BuZnOAr′
RZnO-t-Bu (R ) Et or Bu)
BuZnX (X ) Cl, Br, or I)
RZnOAr′ (R ) Et or Bu)
BuZnO-t-Bu
More absorptions are expected for a structure such
as 3; rapid Zn-N bond breaking and forming that in
solution could lead to averaged absorptions character-
istic of the symmetry of 4 is unlikely in a solid.
Moreover, the 14N4 absorptions are similar to those
observed for the liquid phase containing EtZn-
(14N4)+Et2ZnI-. (4) Solids result from those prepara-
tions (see Conclusions) in which coordinating ability of
the macrocycle for RZn+ and stability of the anion
formed are greatest.18
solution
solution
solution
solution
RZnOAr′ (R ) Et or Bu)
a
The temperature is ca. 23 °C. Except where noted, equimolar
b
amounts of macrocycle and organozinc reactant were used. Hex
) hexyl, 2-EtBu ) 2-ethylbutyl, Ar ) 3,5-di-tert-butylphenyl,
Ar′ ) 2,6-di-tert-butylphenyl. c 14N4 ) 1,4,8,11-tetramethyl-1,4,-
8,11-tetraazacyclotetradecane, 15N5 ) 1,4,7,10,13-pentamethyl-
1,4,7,10,13-pentaazacyclopentadecane, 211C ) 2,1,1-cryptand,
221C ) 2,2,1-cryptand, 18C6 ) 18-crown-6, 15C5 ) 15-crown-5,
1
The H NMR spectra of the solutions show only one
1
set of R (and of macrocycle) absorptions. The H NMR
absorptions of the solutions resulting from akylzinc-
alkoxy or alkylzincaryloxy compounds were close (<0.1
ppm) to those of either reactant alone. The butyl and
crown ether absorptions of the solutions of BuZnX with
15C5 or 18C6 were shifted more from those of the
reactants: the crown ether absorption somewhat upfield
(∼0.1 ppm), the CH2Zn absorption only slightly (<0.1
ppm) shifted, and the CH2CH2Zn and CH2CH2CH2Zn
absorptions generally downfield (∼0.2-0.3 ppm). The
small differences in positions of absorptions from those
exhibited by the reactants are likely due to some routine
coordination of a Zn atom to O or N atoms of a
macrocycle.
d
12C4 ) 12-crown-4. Organozinc/macrocycle ratios of both 1:1 and
2:1 were used.
both t-BuOH and 14N4 so that the 14N4 might have a
chance to react before oligomer formed. The potential
coordination of RZn+ by 14N4, however, is insufficient
to transfer t-BuO- to R2Zn from whatever form of RZnO-
t-Bu the 14N4 encounters.
R Zn X, R Zn OR′, or R Zn OAr a n d a Ma cr ocycle.
Combining one of these RZnZ compounds and a mac-
rocycle (without R2Zn) in benzene (Table 2)16 either
forms a solution containing the reactants or results in
rapid formation of a precipitate that probably is
RZn(macrocycle)+Z- (eq 5). The alkoxy and aryloxy
Con clu sion s
RZnZ + macrocycle f RZn(macrocycle)+ Z-V (5)
In disproportionation of an R2Zn compound to RZn-
(macrocycle)+ and R3Zn-, R2Zn serves as both an “R-”
acceptor and, in concert with the macrocycle, an “R-”
donor. Only rarely is the sum of donor and acceptor
abilities sufficient for disproportionation to be signifi-
cant. The better acceptor R3Al permits more R2Zn-
macrocycle combinations to become donors, forming
RZn(macrocycle)+R4Al-, although not with macrocycles
that are poor coordinators for RZn+. Providing a leaving
group more effective than “R-” also favors ion formation.
RZnX and RZnOAr (but not RZnOR′) compounds and
14N4 can transfer groups to R2Zn to form RZn(14N4)+
and R2ZnX- or R2ZnOAr-. In the absence of R2Zn,
combinations of RZnX or RZnOAr and 14N4, 15N5,
211C, or 221C (though not 18C6 or 15C5, weaker
coordinators13 for RZn+) form solids that must have
RZn(macrocycle)+ and X- or OAr- ions. Zinc counter-
reactants were prepared from reactions (eq 4) of the
appropriate alcohol or phenol17 (EtZnOMe and EtZnO-
t-Bu were generated by adding excess Et2Zn to a
solution containing the alcohol and also the macrocycle).
The precipitates have 1:1 compositions since 1H NMR
spectra of the supernatant liquids have only weak
absorptions in 1:1 (RZnZ/macrocycle) preparations but
significant RZnZ absorptions in 2:1 preparations. The
solids are not significantly soluble in benzene, diethyl
ether, or THF. Several observations indicate that the
solids are RZn(macrocycle)+Z-. (1) Their compositions
are one RZnZ per macrocycle. (2) Precipitate formation
suggests ions since most organozinc compounds are
soluble in nonpolar solvents and usually remain so on
addition of coordinating ethers or amines. (3) A solid
phase 13C NMR spectrum of the solid obtained from
EtZnBr and 14N4 has just four 14N4 absorptions, the
number expected for an ion having the symmetry of 4.
parts of the XMg(14N4)+ (X ) Cl or Br) and RMgX2
-
(X ) Cl, Br, or I) ions observed with RMgX and 14N4
were not observed. RZnOR′ compounds did not interact
significantly with any macrocycle. Solids result there-
fore when stabilities of RZn(macrocycle)+ 13 and the
accompanying anion19 are greatest.
(16) In preliminary experiments, solids formed from combinations
of EtZnCl with 211C or 221C and of EtZnI with 211C, and solutions
resulted from combining various ratios of EtZnBr or EtZnI and 12C4
(12-crown-4), 15C5, or 18C6 (although precipitates formed from some
combinations of EtZnCl and 12C4 or 15C5).
(17) Crystalline EtZnOAr′ [Parvez, M.; BergStresser, G. L.; Richey,
H. G., J r. Acta Crystallogr., Sect. C l992, 48, 641] was used to prepare
the solutions for NMR analysis.
(18) Other factors, of course, influence formation of ionic solids from
RZnZ compounds. For example, strong packing forces in a solid favor
and strong aggregation of RZnZ in a solution could disfavor solid
formation.

4022 Organometallics, Vol. 20, No. 19, 2001
Fabicon and Richey
adding a solution of the dialkylzinc compound to a suspension
of the phenol.
Exp er im en ta l Section
Butylzinc tert-butoxide: 1H NMR (200 MHz) δ 0.47 (t, CH2-
Zn), 0.98 (t, CH3CH2), 1.36 (s, CH3CO), 1.45 (m, CH3CH2), 1.64
(m, CH2CH2Zn).
Procedures involving organometallic compounds were per-
formed under a nitrogen atmosphere using Schlenk tech-
niques, a glovebox, and a vacuum line. Solutions for NMR
analysis were prepared in the glovebox and transferred into
NMR tubes to which an extension of routine glass tubing had
been added to facilitate sealing with a flame. An NMR tube
was capped temporarily with a septum, removed from the
glovebox, immersed in liquid nitrogen, and sealed at the
Butylzinc 2,6-di-tert-butylphenoxide: 1H NMR (300 MHz)
δ 0.52 (t, CH2Zn), 0.99 (t, CH3CH2), 1.46 (m, CH3CH2), 1.59
(s, (CH3)3C), 1.68 (m, CH2CH2Zn), 6.88 (t, p-H), 7.29 (d, m-H).
Eth ylzin c 3,5-d i-ter t-bu tylp h en oxid e: 1H NMR (200
MHz) δ 0.51 (q, CH2), 1.10 (t, CH3CH2), 1.42 (s, (CH3)3C), 6.88
(s, p-H), 7.02 (s, o-H).
1
extension. NMR spectra were recorded at ca. 23 °C. H NMR
absorption positions are relative to internal C6D5H (δ 7.15);
notations used are as follows: s, singlet; d, doublet; t, triplet;
q, quartet; m, a more complex multiplet; c, complex overlap-
ping absorptions; br, broad. 13C NMR absorptions of solutions
are relative to internal C6D6 (δ 128.0) and of solids to external
hexamethylbenzene (δ 17.36). 27Al spectra were taken at 78
MHz. Benzene and benzene-d6 were distilled from CaH2 and
stored over molecular sieves (4 Å) under a nitrogen atmo-
sphere. Diethyl ether and THF were distilled from sodium
benzophenone ketyl immediately prior to use.
Dia lk ylzin c Com p ou n d s. The preparation procedure has
been described.20 The purification method and 1H NMR
spectrum are given for compounds for which these were not
reported.
Tr ia lk yla lu m in u m Com p ou n d s. The solvent was distilled
at atmospheric pressure from commercial hexane solutions and
the organoaluminum compounds then were distilled.
Trimethylaluminum (48-52 °C, 20 Torr): 1H NMR (300
MHz) δ -0.37 (s, CH3).
Triethylaluminum (60-63 °C, 5 Torr): 1H NMR (300 MHz)
δ 0.30 (q, CH2), 1.02 (t, CH3).
Triisobutylaluminum (93-96 °C, 1 Torr): 1H NMR (300
MHz) δ 0.25 (d, CH2), 0.99 (d, CH3), 1.92 (looks like a septet,
CH).
Ma cr ocycles. 15N5 and 18N6 were synthesized as already
described.20 The other macrocycles were commercial samples.
P r ep a r a tion of NMR Solu tion s. Preparations were done
in small vials containing a magnetic stirring bar. With an
alkylzinc halide, alkoxide, or aryloxide used as a solution, the
macrocycle was added to the organozinc solution and the
preparation was stirred. Ethylzinc halides, ethylzinc 2,6-di-
tert-butylphenoxide, and all dialkylzinc and trialkylaluminum
compounds were handled as pure solids or liquids: in a
preparation using only one organozinc compound, it was added
to the vial, benzene-d6 and then the macrocycle were added,
and the preparation was stirred; in a preparation using a
dialkylzinc compound and another organozinc compound or a
trialkylaluminum compound, the dialkylzinc compound was
added to the vial, benzene-d6 and then the macrocycle were
added, the preparation was stirred, and finally the other
organometallic compound was added and stirring was contin-
ued. Preparations were usually done on a 0.5 mL scale. When
a second liquid phase formed, each phase was transferred to
an NMR tube; because the volume of the denser phase usually
was small, it was necessary to do such preparations on a larger
scale. When traces of solid remained, either the preparation
was filtered through a pipet fitted with glass wool into the
NMR tube or, after transfer and sealing, the NMR tube was
centrifuged to collect the solid at the unobserved (by the
spectrometer) end. For the representative NMR spectra below,
equimolar amounts of reactants were used; the concentration
of each reactant (if no reaction and no phase separation
occurred) was in the range 0.1-0.5 M.
Dihexylzinc (64-69 °C, 0.1 Torr): (200 MHz) δ 0.29 (t, CH2-
Zn), 0.93 (t, CH3), 1.28-1.52 (c, (CH2)3CH3), 1.56 (m, CH2CH2-
Zn).
Di(2-ethylbutyl)zinc (81-84 °C, 0.1 Torr): (300 MHz) δ 0.31
(d, CH2Zn), 1.17 (t, CH3), 1.52-1.88 (c, (CH2)2CH).
Alk ylzin c Ha lid es. The preparation of a butylzinc chloride
solution, following a literature procedure,21 is typical. ZnCl2
(76 mg, 0.56 mmol) from a sample heated at 110 °C at reduced
pressure for 24 h, Bu2Zn (100 mg, 0.56 mmol), and benzene
(1.5 mL) were sealed in a glass tube containing a magnetic
stirring bar. The tube was heated at 70-75 °C and the contents
were stirred until all solid dissolved.
Ethylzinc chloride: 1H NMR (200 MHz) δ 0.65 (q, CH3), 1.36
(t, CH2).
Ethylzinc bromide: 1H NMR (200 MHz) δ 0.65 (q, CH3), 1.26
(CH2).
Ethylzinc iodide: 1H NMR (200 MHz) δ 0.25 (q, CH3), 1.15
(t, CH2).
1
Butylzinc chloride: H NMR (200 MHz) δ 0.69 (t, CH2Zn),
0.99 (t, CH3), 1.36 (m, CH2CH3), 1.54 (m, CH2CH2Zn).
1
Butylzinc bromide: H NMR (200 MHz) δ 0.58 (t, CH2Zn),
0.98 (t, CH3), 1.35 (m, CH2CH3), 1.52 (m, CH2CH2Zn).
Butylzinc iodide: 1H NMR (200 MHz) δ 0.35 (t, CH2Zn), 0.96
(t, CH3), 1.33 (m, CH2CH3), 1.52 (m, CH2CH2Zn).
Hexylzinc chloride: 1H NMR (200 MHz) δ 0.68 (t, CH2Zn),
0.93 (t, CH3), 1.28-1.39 (c, (CH2)3CH3), 1.68 (m, CH2CH2Zn).
Hexylzinc bromide: 1H NMR (200 MHz) δ 0.60 (t, CH2Zn),
0.95 (t, CH3), 1.30-1.43 (c, (CH2)3CH3), 1.72 (m, CH2CH2Zn).
2-Ethylbutylzinc chloride: 1H NMR (300 MHz) δ 0.70 (d,
CH2Zn), 1.32 (t, CH3), 1.56-1.94 (c, (CH2)2CH).
Me2Zn-Me3Al-14N4: 1H NMR (lower phase, 300 MHz) δ
-1.37 (s, CH3Zn), -0.18 (m, CH3Al), 1.59 (br s, CH3Zn) 2.17
(t, CHHCH2CHH), 0.9-1.9 (other 14N4 H's); 13C NMR (lower
layer, 75 MHz) δ -15.5 (CZn), -3.2 (sextet, J ) 79.9 Hz, CAl),
44.8 (CH3N), 21.5 (NCCCN), 56.1 and 60.1 (NCCN and
NCCCN).
Et2Zn-Et3Al-14N4: 1H NMR (lower phase, 300 MHz) δ
-0.47 (q, CH2Zn), 0.11 (br, CH2Al), 1.00 (t, CH3CH2Zn), 1.57
(br, CH3CH2Al), 1.62 (br s, CH3N), 1.99 (t, CHHCH2CHH),
0.9-1.8 (other 14N4 H's); 13C NMR (lower phase, 75 MHz) δ
-0.5 (CZn), 2.8 (sextet, J ) 72.5 Hz, CAl), 13.1 (br, CCAl),
14.4 (CCZn), 44.3 (CH3N), 21.3 (NCCCN), 56.3 and 60.3
(NCCN and NCCCN).
2-Ethylbutylzinc bromide: 1H NMR (300 MHz) δ 0.60 (d,
CH2Zn), 1.29 (t, CH3), 1.48-1.54 (c, (CH2)2CH).
Alk ylzin c Alk oxid es a n d Ar yloxid es. Solutions of alkox-
ides were prepared by dropwise addition of 1 equiv of the
alcohol dissolved in benzene-d6 to a stirred benzene-d6 solution
of the dialkylzinc compound. In the preparations of ethylzinc
methoxide and tert-butoxide, the solution of dialkylzinc com-
pound already contained a macrocycle. The preparation and
1H NMR spectrum of ethylzinc 2,6-di-tert-butylphenoxide have
been described.17 The other aryloxides were prepared by
i-Bu2Zn-i-Bu3Al-14N4: 1H NMR (lower phase, 300 MHz)
δ -0.12 (d, CH2Zn), 0.28 (br, CH2Al), 0.98 (d, (CH3)2CHCH2-
Zn), 1.42 (d, (CH3)2CHCH2Al), 1.51 (m, CHCH2Al), 1.64 (m,
CHCH2Zn), 1.27 (m, CH2CHHCH2), 1.60 (br s, CH3N), 1.64 (m,
CH2CHHCH2), 2.88 (t, J ) 12.1 Hz, CHHCH2CHH), 1.7-2.1
(other 14N4 H’s).
(19) The tendency to exist as anions rather than to be bonded to
zinc should be greater for halo (X) and aryloxy (OAr) than for alkoxy
(OR).
(20) Fabicon, R. M.; Parvez, M.; Richey, H. G., J r. Organometallics
l999, 18, 5163.
Et2Zn-Et3Al-15N5: 1H NMR (lower phase, 300 MHz) δ
-0.24 (q, CH2Zn), 0.12 (br, CH2Al), 0.99 (t, CH3CH2Zn), 1.55
(21) Boersma, J .; Noltes, J . G. Tetrahedron Lett. l966, 1521.

Coordinated RZn(macrocycle)+ Cations
Organometallics, Vol. 20, No. 19, 2001 4023
(br, CH3CH2Al), 1.76 (s, CH3N), 1.89 (s, CH2N); 13C NMR
(lower phase, 75 MHz) δ -0.9 (CZn), 2.8 (sextet, J ) 75.7 Hz,
CAl), 11.8 (CCZn), 13.3 (br, CCAl), 43.2 (br, CH3N), 56.0 (br,
CH2N).
EtZnCl-Et2Zn-14N4: 1H NMR (300 MHz) δ -0.24 (q, CH2-
Zn+), 0.64 (q, CH2Zn-), 1.20 (t, CH3CH2Zn+), 1.77 (t, CH3-
CH2Zn-), 1.79 (s, CH3N); 3.24 (t, CHHCH2CHH), 1.2-2.2
(other 14N4 H’s).
EtZnBr-Et2Zn-14N4: 1H NMR (300 MHz) δ -0.27 (q, CH2-
Zn+), 0.67 (q, CH2Zn-), 1.19 (t, CH3CH2Zn+), 1.73 (t, CH3-
CH2Zn-), 1.77 (s, CH3N), 3.18 (t, CHHCH2CHH), 1.2-2.3
(other 14N4 H’s).
EtZnI-Et2Zn-14N4: 1H NMR (lower phase, 300 MHz) δ
-0.32 (q, CH2Zn+), 0.65 (q, CH2Zn-), 1.14 (t, CH3CH2Zn+), 1.66
(t, CH3CH2Zn-), 1.77 (s, CH3N), 2.94 (t, CHHCH2CHH), 1.1-
2.3 (other 14N4 H’s).
Ethylzinc 3,5-di-tert-butylphenoxide-Et2Zn-14N4: 1H NMR
(lower phase, 300 MHz) δ -0.40 (q, CH2Zn+), 0.51 (br,
CH2Zn-), 1.06 (t, CH3CH2Zn+), 1.37 (s, (CH3)3C), 1.69 (br t,
CH3CH2Zn-), 1.99 (s, CH3N), 7.04 (s, p-H), 7.27 (s, o-H), 0.9-
2.4 (other 14N4 H’s).
i-Bu2Zn-i-Bu3Al-15N5: 1H NMR (lower phase, 300 MHz)
δ -0.09 (d, CH2Zn), 0.21 (br, CH2Al), 0.93 (d, (CH3)2CHCH2-
Zn), 1.36 (d, (CH3)2CHCH2Al), 1.46 (m, CHCH2Al), 1.60 (m,
CHCH2Zn), 1.87 (br s, CH3N), 2.09 (br s, CH2N); 13C NMR
(lower phase, 75 MHz) δ 4.1 (CZn), 3.2 (sextet, J ) 73.3 Hz,
CAl), 11.0 (br, CCAl), 14.8 (CCZn), 18.8 (CCCAl), 21.0 (CCC-
Zn), 42.6 (br, CH3N), 54.8 (br, CH2N).
Et2Zn-Et3Al-2,1,1-cryptand: 1H NMR (lower phase, 300
MHz) δ -0.35 (q, CH2Zn), 0.09 (br, CH2Al), 1.03 (t, CH3CH2-
Zn), 1.53 (br, CH3CH2Al), 1.7-3.5 (211C H's); 13C NMR (lower
phase, 75 MHz) δ 2.7 (sextet, J ) 72.5 Hz, CAl), 3.3 (CZn),
13.2 (br, CCAl), 14.5 (CCZn), 55.6, 57.0, 57.3, 64.7, 65.6, 66.2,
and 67.4 (211C C’s).
Et2Zn-Et3Al-2,2,1-cryptand: 1H NMR (lower phase, 300
MHz) δ -0.32 (q, CH2Zn), 0.08 (br, CH2Al), 1.04 (t, CH3CH2-
Zn), 1.55 (br, CH3CH2Al), 1.7-3.6 (221C H’s).
Ack n ow led gm en t. We are indebted to the National
Science Foundation for supporting this research. We
thank Alan Benesi for help with various NMR experi-
ments, Gretchen BergStresser for some preliminary
experiments, and an anonymous referee for particularly
helpful suggestions.
Et2Zn-Et3Al-18N6: 1H NMR (300 MHz) δ 0.20 (q, CH2-
Zn), 0.22 (br, CH2Al), 1.21 (t, CH3CH2Al), 1.40 (t, CH3CH2Zn),
2.09 (br s, CH3N), 2.22 (br s, CH2N).
Et2Zn-Et3Al-2,2,2-cryptand: 1H NMR (300 MHz) δ 0.16
(q, CH2Zn), 0.19 (br, CH2Al), 1.20 (t, CH3CH2Al), 1.39 (t, CH3-
CH2Zn), 2.42 (br s, CH2N), 3.40 (br t, OCH2CH2N), 3.52 (br s,
OCH2CH2O).
OM0102798