Reversible Insertion of Methyl Isothiocyanate into Copper(I) Aryloxides

Article abstract of DOI:10.1021/ic9516424

MeNCS undergoes insertion into the copper(I)-aryloxide bond to form [N-methylimino(aryloxy)methanethiolato]copper(I) complexes. This insertion occurs in the absence of ancillary ligands unlike the analogous insertion of PhNCS. The reaction with 4-methylph

Full text of DOI:10.1021/ic9516424

Inorg. Chem. 1996, 35, 5427-5434
Reversible Insertion of Methyl Isothiocyanate into Copper(I) Aryloxides
Christina Wycliff, Ashoka G. Samuelson,* and Munirathinam Nethaji
5427
Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India
ReceiVed December 22, 1995X
MeNCS undergoes insertion into the copper(I)-aryloxide bond to form [N-methylimino(aryloxy)methanethiolato]-
copper(I) complexes. This insertion occurs in the absence of ancillary ligands unlike the analogous insertion of
PhNCS. The reaction with 4-methylphenoxide results in the formation of hexakis[[N-methylimino(4-methylphe-
noxy)methanethiolato]copper(I)] (1), which has been characterized by X-ray crystallography. Crystal data for 1:
hexagonal R3h, a ) 12.365(3) Å, c ) 36.734(16) Å, γ ) 120°, Z ) 3, V ) 4863(3) Å3, R ) 0.0306. Reactions
of 2,6-dimethyl- and 4-chlorophenoxides also result in analogous copper(I) complexes 2 and 3. Addition of
stochiometric amounts of PPh3 to the oligomeric complexes typically results in the extrusion of MeNCS. The
ease of extrusion is dependent on the substituents on the aryloxide, and this deinsertion is accelerated by water.
However, the extrusion reaction is slow enough in the case of the N-methylimino(2,6-dimethylphenoxy)-
methanethiolate complex and the isolation of an intermediate monomeric product bis(triphenylphosphine)[N-
methylimino(2,6-dimethylphenoxy)methanethiolato]copper(I) (4) is possible. Crystal data for 4: triclinic P1h, a
) 10.088(2) Å, b ) 11.302(1) Å, c ) 17.990(2) Å, R ) 94.06(1)°, â ) 95.22(2)°, γ ) 103.94(1)°, Z ) 2, V )
1974.4(7) Å3, R ) 0.0361. In the presence of of PPh3, the insertion reaction becomes reversible. This allows the
exchange of the heterocumulene MeNCS or the aryloxy group in these molecules with another heterocumulene
or a phenol, respectively, when catalytic amounts of PPh3 are added. Oligomers with exchanged heterocumulmes
and phenols could be characterized by independent synthesis.
Introduction
received less attention.11,12 The juxtaposition of a hard donor
with a soft metal ion leads to interesting reactivity patterns.13
Some of them are quite predictable on the basis of HSAB
The reactivity of early1-4 and middle5-7 transition metal
aryloxides and alkoxides has been extremely well studied.
However late transition metal aryloxides and alkoxides8-10 have
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X Abstract published in AdVance ACS Abstracts, August 1, 1996.
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S0020-1669(95)01642-9 CCC: $12.00 © 1996 American Chemical Society

5428 Inorganic Chemistry, Vol. 35, No. 19, 1996
Wycliff et al.
principles.14-16 Studies on the insertion reactions of Ir[(PR3)2-
(CO)(OR)] with CO show that the hard alkoxide ligand can be
readily replaced by the softer carbon monoxide.17 In this
connection, the reactions of metal alkoxides with heterocumu-
lenes are particularly illustrative of how reactions are based on
HSAB preferences.18-23 The iridium alkoxide hydride complex
Cp*Ir(PPh3)(OEt)(H) reacts with heterocumulenes (XdCdY,
X/Y ) O, S, NR) to give products having Ir-S or Ir-N bonds
like Cp*Ir[XC(Y)OEt](H)(PPh3), (where X ) S or NR)13 rather
than complexes with Ir-O bonds. Similarly the reactions of
copper(I) aryloxide with CS2 and PhNCS result in complexes
with Cu(I)-S and Cu(I)-N bonds.24 Both examples demon-
strate the affinity that late transition metal ions have toward
softer donor ligands. Not only do the metals maximize the soft-
soft interactions, the ligands around the metal also maximize
soft-soft and hard-hard interactions. A very good illustration
of the selectivity of the ligands toward hard and soft centers is
provided by the reaction of four-coordinate complexes of the
type [Mo(NR)2(OR)2] with PhNCO and PhNCS.25 PhNCO
undergoes insertion across the “hard” alkoxides to form two
N,O chelating carbamate ligands whereas PhNCS inserts across
one of the “softer” imido ligands to form a complex with a
chelating N,N-thioureato ligand. Further, PhNCS can be
displaced by PhNCO in the N,N-thioureato complex in order
to increase hard-hard interactions. Thus most reactions known
to date suggest the predictability of such insertion reactions on
the basis of HSAB principles. It would be interesting to probe
the limitations of this predictability.
late transition metal alkoxides insert into PhNCS or CS2, the
metal-sulfur (soft-soft) interaction would be stronger than the
corresponding metal-oxygen interaction formed from a CO2
insertion. So, the validity of extending the reactions of these
heterocumulenes to the reactions of CO2 has been challenged.39
The latter contention gains weightage from the fact that the
insertion of soft heterocumulenes is irreversible while several
insertion reactions of CO2 are reversible.40-43 One can then
ask, would it be possible to make heterocumulene reactions
reversible by electronic perturbations?
In this paper we report our recent findings on the insertion
reactions of copper(I) aryloxides with MeNCS that has relevance
to the two aspects mentioned above. MeNCS reacts with
copper(I) aryloxides to give [N-methylimino(aryloxy)methaneth-
iolato]copper(I) complexes, very similar to those isolated in the
corresponding reactions with PhNCS.24 The reactivity of Cu-
(I)-OAr with MeNCS is not altogether predictable from simple
HSAB principles as in the reactions of copper(I) aryloxides with
PhNCS or CS2. There appears to be a tendency for copper(I)
to balance the number of hard and soft donors in its coordination
sphere rather than maximize the number of soft donors. Recent
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Copper(I) Aryloxides
Inorganic Chemistry, Vol. 35, No. 19, 1996 5429
observations made by others44 and us45 suggest that this might
be a general phenomenon. Second, just as the reactions of CO2
with copper(I) alkoxides are reversible,40 the reactions with
MeNCS are also reversible in the presence of phosphines. A
comparison of the reactions of PhNCS and MeNCS is made,
throwing light on the electronic factors that govern the insertion
reactions.
Scheme 1
Results and Discussion
Insertion Reactions. MeNCS reacts with copper(I) arylox-
ides at room temperature to give [N-methylimino(aryloxy)-
methanethiolato]copper(I) complexes. From the IR and NMR
spectroscopic data of these complexes, it is clear that MeNCS
has been inserted across the Cu(I)-OAr bond. An [N-meth-
ylimino(aryloxy)methanethiolato]copper(I) complex is formed
just as in the case of PhNCS, where an [N-phenylimino-
(aryloxy)methanethiolato]copper(I) complex is formed. The
insertion reaction occurs in the absence of ancillary ligands.
This contrasts with the reactions of PhNCS which proceed only
in the presence of ligands such as P(OMe)3 and CH3CN. These
ligands facilitate the reaction by breaking down the polymeric
structure of the copper(I) aryloxides.24 A possible reason for
this difference could be the smaller size of MeNCS which allows
it to penetrate the polymeric structure of copper(I) aryloxide.
A second reason could be the better coordinating ability of the
MeNCS which would also make it possible for the MeNCS to
break down the polymeric aryloxide. In the case of the more
bulky and poorly coordinating PhNCS, an ancillary ligand is
necessary.
However, MeNCS does not react with all copper(I) arylox-
ides. Thus the reaction of MeNCS with copper(I) 2,6-di-tert-
butyl-4-methylphenoxide does not give characterizable copper-
containing complexes with or without added ancillary ligands.
The corresponding reaction with PhNCS,24a on the other hand,
gives a dimeric complex bis{[µ-{N-phenylimino(2,6-di-tert-
butyl-4-methylphenoxy)methanethiolato}](trimethyl phosphite)-
copper(I)} (6) with the weak ancillary ligand P(OMe)3 attached
to the metal. It is likely that the steric bulk of the [CuL1]2
complex (where L1 is N-methylimino(2,6-di-tert-butyl-4-me-
thylphenoxy)methanethiolate) prevents it from oligomerizing
and forming a tetramer or a hexamer as in the case of [CuL2]
(where L2 is N-phenylimino[2,6-di-tert-butyl-4-methyphenoxy]-
methanethiolate) (see Scheme 1). The difference in reactivity
is the result of the sensitivity of MeNCS clusters toward
phosphine ligands. Unlike [CuL2]2 which is stable in the
presence of P(OMe)3, the [CuL1]2 dimer is unstable, due to a
deinsertion reaction (Vide infra). The isolation of the organic
product MeNHC(O)O-(2,6-t-Bu2-4-Me-C6H2) (7) from the reac-
tion mixture suggests that the insertion of the phenoxide into
the MeNCS is feasible. The available results do not allow us
to distinguish between an insertion reaction occurring in the
coordination sphere of the copper followed by a demetalation
and an insertion reaction occurring outside the coordination
sphere of copper(I). Either way, the difference in the heterocu-
mulene part has made a significant impact on the outcome of
the insertion reaction.
chlorophenoxy)methanethiolato]copper(I), is obtained when [Cu-
(CH3CN)4]ClO4 is used as the source of Cu(I). The ancillary
ligand CH3CN promotes the insertion reaction. Such an increase
in the nucleophilic reactions of copper(I) phenoxides has been
observed before in reactions with CS2.46 Similarly, the insertion
reaction of PhNCS with the 4-chlorophenoxide is more facile
as shown by the marginally higher yield (7%) of the inserted
product 5, [N-phenylimino(4-chlorophenoxy)methanethiolato]-
copper(I), obtained when [Cu(CH3CN)4]ClO4 is used than when
CuCl is used (3%). However, isolated yields need not neces-
sarily reflect the stability of the products formed or the ease of
insertion if crystallisation forces influence product formation.
In the case of the [N-methylimino(4-methylphenoxy)meth-
anethiolato]copper(I) complex 1 it was possible to obtain single
crystals suitable for X-ray diffraction. Complex 1 is hexameric
like the corresponding hexakis{[µ-N-phenylimino(4-methylphe-
noxy)methanethiolato]copper(I) complex 8.24b The coordination
geometry and the connectivity of the ligand remain the same.
The six copper atoms are in an octahedral arrangement, and
the six N-methylimino(4-methylphenoxy)methanethiolate ligands
(L3) link the copper atoms through sulfur and nitrogen atoms.
Each copper atom is coordinated to two sulfur atoms and one
nitrogen atom, each belonging to three different ligands. In
comparison with the hexamer 8, there is considerably less
distortion and a nearly perfect octahedral core of copper atoms
is present due to the reduced steric constraints, resulting in the
beautiful paddle wheel geometry shown in Figure 1.
The nuclearity of clusters is known to be controlled by the
steric requirements of the ligands.47-49 In the case of [N-
phenylimino(aryloxy)methanethiolato]copper(I) oligomers, it is
primarily determined by the steric bulk of the substituents on
the aryloxide.24a Thus the [N-phenylimino(2,6-dimethylphe-
noxy)methanethiolato]copper(I) forms a tetramer (9) rather than
a hexamer because of steric interactions between the phenyl
group of the PhNCS and the methyl groups on OAr. Since the
ligand N-methylimino(2,6-dimethylphenoxy)methanethiolate (L4)
has reduced steric requirements, the possibilty of forming a
hexamer or a higher nuclearity oligomer with [N-methylimino-
The reaction of 4-chlorophenol is an example of how insertion
reactions of electron-deficient phenoxides are difficult. The
reaction of copper(I) 4-chlorophenoxide and MeNCS gives no
inserted product when CuCl is used as the source of Cu(I),
whereas a 3% yield of the complex 3, [N-methylimino(4-
(44) Francesco, T.; Refosco,.; Bandoli, G.; Pilloni, G.; Corain, B. J. Chem.
Soc., Dalton Trans. 1994, 2471.
(45) Vijayashree, N.; Samuelson, A. G.; Nethaji, M. Curr. Sci. 1993, 65,
(46) Narasimhamurthy, N.; Samuelson, A. G. Tetrahedron Lett. 1988, 29,
57.
827.

5430 Inorganic Chemistry, Vol. 35, No. 19, 1996
Wycliff et al.
Reversible Insertion. The major difference between the
clusters generated from PhNCS and MeNCS is the reactivity
pattern that the clusters 1 and 2 exhibit on treatment with PPh3.
The [N-phenylimino(phenoxy)methanethiolato]copper(I) clusters
8 and 9 break down to give monomers [Cu(SC(OAr)dNPh)-
(PPh3)2] (10, 11) or dimers [Cu-µ-(SC(OAr)dNPh)(PPh3)]2 (12,
13) with 1 and 2 equiv of PPh3, respectively. On the other
hand, on the basis of the NMR spectra, it is clear that the
MeNCS clusters undergo a series of reactions with PPh3 which
finally results in the extrusion of MeNCS from the cluster.
Addition of 2 equiv of PPh3 to the [N-methylimino(aryloxy)-
methanethiolato]copper(I) complexes 1 and 2 resulted in the
formation of a new peak in the NMR spectrum at 3.26 ppm,
which corresponds to the peak position of free MeNCS. While
the deinsertion of the MeNCS apppeared to be instantaneous
in the case of the hexamer 1, it was much slower in the case of
2.
Figure 1. ORTEP view of [CuSC(OC6H4-4-Me)dNMe]6 (1).
In order to understand the steps involved in the extrusion
reaction, NMR experiments were carried out with 2 and added
PPh3. Immediate disappearance of the peaks corresponding to
2 and formation of three new peaks in the MeNCS region (3.02,
3.12, and 3.26 ppm) were observed. The intensity of the peak
at 3.26 ppm (free MeNCS) increased with time. The intensities
of the other two peaks were dependent on the amount of PPh3
added. Adding 1 equiv of PPh3 led to a 2.8:1 ratio of the peaks
at 3.02 and 3.12 ppm, whereas addition of 2 and 3 equiv resulted
in 1:3 and 1:2.8 ratios, respectively. Assuming that equilibria
of phosphine-coordinated adducts exist (see Scheme 2), it is
possible to explain the formation of the three peaks and their
intensity variations with added PPh3. The peak at 3.02 ppm
corresponds to the dimer II, and the one at 3.12 ppm, to the
monomer III. The 31P NMR spectra of the monomeric and
dimeric [N-phenylimino(aryloxy)methanethiolato]copper(I) com-
plexes (10-13) are helpful in assigning the peaks and in
understanding the equilibria in these systems as well. If the
reaction mixture was allowed to stand for about 10 days, the
formation of PPh3S was detected (1H NMR, 31P NMR, and TLC)
in the reaction mixture. The removal of PPh3 as PPh3S results
in a shift of the equilibrium, and the formation of 2 could be
(2,6-dimethylphenoxy)methanethiolato]copper(I) must be con-
sidered. It was not possible to obtain single crystals of 2 suitable
1
for X-ray diffraction studies. The H NMR spectrum of this
complex has two resonances for the methyls on the aryloxy
group of the ligand, similar to the tetrameric complex 9 obtained
in the reaction with PhNCS. Since it is not possible to form a
mononuclear structure with this ligand and satisfy the coordina-
tion requirements of copper, this complex must be at least
tetranuclear like the corresponding tetrakis{[µ-N-phenylimino-
(2,6-dimethylphenoxy)methanethiolato]copper(I)} complex 9.
Since all the hexameric structures isolated in this study have
an orange color in the solid state, and the tetramers have a white
color, one can infer that complex 2 is in fact a tetramer.
However, in solution, the UV-visible spectral data available
for the complexes are extremely similar indicating extensive
dissociation and do not permit definitive conclusions. Modeling
studies using the Insight program50 show that a hypothetical
hexamer formed with the ligand L4 is not sterically congested.
This result is quite different from that obtained in the case of
the tetrameric complex 9, where there is a phenyl instead of a
methyl on the nitrogen.24a In the case of 9 a hexamer could
not be constructed without steric congestion.
1
inferred from the H NMR spectrum. This indicates that the
(47) (a) Fiaschi, P.; Floriani, C.; Pasquali, M.; Chiesi-Villa, A.; Guastini,
C. Inorg. Chem. 1986, 25, 462. (b) Gibson, V. C.; Kee, T. P. J. Org.
Met. Chem. 1993, 444, 91. (c) Chisholm, M. H.; Folting-Streib, K.;
Tiedtke, D. B.; Lemoigno, F.; Eisenstein, O. Angew. Chem., Int. Ed.
Engl. 1995, 34, 110. (d) Edema, J. J. H.; Gambarotta, S.; Fre’van
Bolhuis; Smeets, W. J. J.; Spek, A. L. Inorg. Chem. 1989, 28, 1407.
(e) Evans, W. J.; Olofson, J. M.; Ziller, J. W. Inorg. Chem. 1989, 28,
4308. (f) Collins, S.; Koene, B. E.; Ramachandran, R.; Taylor, N. J.
Organometallics 1991, 10, 2092. (g) Minhas, R.; Duchateau, R.;
Gambarotta, S.; Bensimon, C. Inorg. Chem. 1992, 31, 4933. (h) Blake,
A. J.; Grant, C. M.; Parsons, S.; Winpenny, R. E. P. J. Chem. Soc.,
Dalton Trans. 1995, 1765.
(48) (a) Block, E.; Gernon, M.; Kang, H.; Liu, S.; Zubieta, J. J. Chem.
Soc., Chem. Commun. 1988, 1031. (b) Tang, K.; Aslam, M.; Block,
E.; Nicholson, T.; Zubieta, J. Inorg. Chem. 1987, 26, 1488. (c) Yang,
Q.; Tang, K.; Liao, H.; Han, Y.; Chen, Z.; Tang, Y. J. Chem. Soc.,
Chem. Commun. 1987, 1076. (d) Koch, S. A.; Fikar, R.; Millar, M.;
O’Sullivan, T. Inorg. Chem. 1984, 23, 121. (e) Blower, P. J.; Dilworth,
J. R. Coord. Chem. ReV. 1987, 76, 121. (f) Koo, B.-K.; Block, E.;
Kang, H.; Liu, S.; Zubieta, J. Polyhedron 1988, 7, 1397. (g) Bochmann,
M.; Powell, A. K.; Song, X. J. Chem. Soc., Dalton Trans. 1995, 1645.
(49) (a) Block, E.; Gernon, M.; Kang, H.; Ofori-Okai, G.; Zubieta, J. Inorg.
Chem. 1991, 30, 1736. (b) Castro, R.; Garcia-Vazquez, J. A.; Romero,
J.; Sousa, A.; Pritchard, R.; McAuliffe, C. A. J. Chem. Soc., Dalton
Trans. 1994, 1115. (c) Block, E.; Ofori-Okai, G.; Kang, H.; Zubieta,
J. Inorg. Chim. Acta 1991, 188, 7. (d) Block, E.; Ofori-Okai, G.; Chen,
Q.; Zubieta, J. Inorg. Chem. Acta 1991, 189, 137. (e) Block, E.;
Gernon, M.; Kang, H.; Zubieta, J. Angew. Chem., Int. Ed. Engl. 1988,
27, 1342. (f) Castro, R.; Garcia-Vazquez, J. A.; Romero, J.; Sousa,
A.; Castinerias, A.; Hiller, W.; Strahle, J. Inorg. Chim. Acta 1993,
211, 47.
insertion and extrusion are in fact reversible.
One expects the thiophilic nature of the copper(I) center to
yield a stable η1-S-bonded L4Cu(PPh3)3 complex, IV (where
L4 is NMedC(OAr)S); however this species deinserts and gives
ArO-Cu(PPh3)3 (VI). The formation of the latter complex can
be explained by the tendency of copper(I) to balance the number
of hard and soft donors in its coordination sphere, a fact that
has been documented in the case of phosphine complexes of
Cu(I).44,45 The aryloxide complex is hydrolytically unstable and
leads to the formation of the phenol (as seen from the NMR
spectra). As a consequence, the deinsertion reaction is faster
in the presence of trace amounts of water in NMR solvents.
The deinsertion reaction is a manifestation of the electronic
requirements of the insertion reaction. The greater electrophi-
licity of the PhNCS drives the reaction to completion and makes
the deinsertion reaction difficult. However, the MeNCS cluster
readily deinserts since MeNCS is a weaker electrophile. The
deinsertion reactions of the [N-methylimino(aryloxy)methanethi-
olato]copper(I) oligomers with PPh3 help us understand why it
is not possible to make the monomeric complex (PPh3)2Cu-
1
[SC(OC6H4-4-Me)dNMe]. Although the H NMR spectra of
the reaction mixtures indicate the initial formation of products
with coordinated phosphine, these are unstable and cannot be
isolated due to the ready extrusion of MeNCS.
(50) Modeling results obtained using software programs from Biosym
Technologies of San Diego, CA, and graphical displays using InsightII.
The steric protection afforded by the o-methyl groups in 4

Copper(I) Aryloxides
Inorganic Chemistry, Vol. 35, No. 19, 1996 5431
Scheme 2
slows down the deinsertion reaction. In the reaction of MeNCS
with copper(I) 2,6-dimethylphenoxide in the presence of PPh3,
the reaction mixture, after removal of the solvent, can be
extracted with petroleum ether to give the monomeric complex
4, in 62% yield. The structure of 4 was obtained from a single-
crystal X-ray crystallographic study. The tetracoordinate copper
atom has two PPh3 ligands and a chelating N-methylimino-
(aryloxy)methanethiolate ligand as shown in Figure 2. The 1H
NMR spectrum of the monomer 4 has two peaks in the MeNCS
region (3.02 and 3.12 ppm), and their nonintegral ratios show
that the monomer is in equilibrium with the dimer. This
equilibrium can be shifted by the addition of PPh3. Solutions
of the monomer undergo deinsertion with time although in the
solid state 4 appears to be indefinitely stable.
Exchange Reactions. The reversible extrusion of MeNCS
from the coordination sphere of the [N-methylimino(aryloxy)-
methanethiolato]copper(I) complexes suggests that these clusters
might exchange MeNCS for a more electrophilic heterocumu-
lene. Addition of PhNCS to [N-methylimino(aryloxy)methaneth-
iolato]copper(I) clusters 1 and 2 resulted in no reaction even
after long reaction times. On the other hand, the addition of
PhNCS to the monomeric complex 4 resulted in a rapid
exchange reaction leading to the formation of the corresponding
PhNCS-inserted monomer 10 (see Scheme 3). The addition of
1 equiv of phosphine to a mixture of 1 and PhNCS promotes
an exchange reaction, resulting in the formation of the monomer
10 and the hexamer 8 as inferred from the 1H NMR spectrum.
The hexamer 1 and the tetramer 2 also exchange with PhNCS
to give the corresponding PhNCS-inserted hexamer 8 and
tetramer 9 with catalytic amounts of phosphine illustrating
reversible insertion of heterocumulenes into Cu(I)-OAr
bonds.
Treatment of the monomer 4 with CS2 results in an exchange
reaction giving the CS2-inserted monomer 15 [Cu{SC(OC6H3-
2,6-Me2)dS}(PPh3)2]. The hexamer 1 can also undergo ex-
change with CS2 in the presence of 2 equiv of PPh3 to give a
monomeric complex. The structure of the monomeric inserted
product 14 [Cu{SC(OC6H4-4-Me)dS}(PPh3)2] has been deter-
mined by single-crystal X-ray crystallography24c and is similar
to that of 4.
Scheme 3
Figure 2. ORTEP view of [Cu{SC(OC6H3-2,6-Me2)dNMe}(PPh3)2]
(4).

5432 Inorganic Chemistry, Vol. 35, No. 19, 1996
Wycliff et al.
Although clusters having the N-phenylimino(aryloxy)-
methanethiolate ligand (8 and 9) do not extrude PhNCS readily,
exchange reactions with CS2 could be carried out on these
clusters also. In the presence of PPh3 (2 equiv) PhNCS clusters
formed the corresponding CS2-inserted monomeric complexes
(14 and 15). However these exchange reactions are not
complete and a mixture of products is obtained. Such exchanges
of the inserted heterocumulene have been observed before.51,52
Since metal alkoxides and aryloxides are known to undergo
alcohol/phenol exchange reactions,53-61 the intermediacy of a
CuIOAr(PPh3)3 complex VI or a CuI(OAr)(SCNR)(PPh3)2
complex V as suggested in Scheme 3 would enable one to
exchange the phenol. The exchange of the phenol can be
represented by eqs 1 and 2.
clearly bring out the electronic requirements for the insertion
reaction besides the requirement for maximizing soft-soft
interactions.
Conclusions
Insertion reactions of MeNCS with copper(I) aryloxides are
similar yet different from the analogous reactions of PhNCS.
The insertion of MeNCS, which is a weaker electrophile, is less
facile. The addition of PPh3 to the oligomeric complexes
typically results in the extrusion of MeNCS contrary to the
oligomers formed by the insertion of PhNCS which merely
breakdown to complexes of lower nuclearity. The extrusion is
dependent on the substituents present on the phenol and is
accelerated and made irreversible by the presence of water. Thus,
unlike the reactions with PhNCS, the insertion reaction is
hampered by the presence of PPh3 due to its reversible nature.
In the case of copper(I) 2,6-dimethylphenoxide, however, a
monomeric insertion product containing two PPh3 ligands is
obtained in high yield due to the steric protection afforded by
the methyl groups. The reversible nature of this insertion
permits exchange of the heterocumulene MeNCS or the aryloxy
group of these molecules either by another heterocumulene or
a phenol, respectively. Catalytic amounts of PPh3 are sufficient
to bring about the exchange reactions, which are driven to
completion when the entering phenol is more nucleophilic and
the incoming heterocumulene is more electrophilic. The revers-
ible nature of the insertion reaction and the exchange reactions
bring out the electronic requirements of the insertion reaction
in addition to the need to maximize soft-soft interactions.
Ar′OH
[CuSC(OAr)dNR]n + mP h [PmCuOAr] + RNCS
8
R ) Ph
[PmCuSC(OAr′)dNPh] (1)
[CuSC(OAr)dNR]n + mP h
[PmCuOAr] + RNCS
Ar′OH
8 mixed clusters (2)
R ) Me
The addition of 4-methylphenol to the cluster 2 where 2,6-
dimethylphenol is present resulted in the formation of mixed
clusters having L3 [SC(OC6H4-4-Me)dNMe] and L4 [SC-
(OC6H3-2,6-Me2]. When an electron-deficient phenol is present
in the cluster, it can be exchanged completely with an electron-
rich phenol. Thus it was possible to replace the p-chlorophenol
in the cluster 5, [CuSC(OC6H4-4-Cl)NPh]n, with 2,6-dimeth-
ylphenol to give the monomer 11 [(PPh3)2CuSC(OC6H3-2,6-
Me2)NPh] in the presence of 2 equiv of PPh3. The p-chlo-
rophenol in this cluster exchanged with 2,6-dimethylphenol in
the presence of 1 equiv of PPh3 to form the monomer 11 and
the tetramer 9. Even 4-methylphenol in the hexamer 1 can be
replaced with 3,5-dimethylpyrazole which is more nucleophilic
than 4-methylphenol. However the products formed with 3,5-
dimethylpyrazole were unstable. These exchange reactions
Experimental Section
General Methods. Dichloromethane, petroleum ether (bp 60-80
°C) and acetonitrile were purified and dried by conventional methods.
They were distilled under nitrogen and deoxygenated before use. CuCl
and [Cu(CH3CN)4]ClO4 (Caution! Perchlorate salts of metal complexes
with organic ligands are potentially explosiVe. Only small amounts
should be prepared, and they should be handled with great caution)
were freshly prepared before use. Phenols, MeNCS, PhNCS, and CS2
were purified by distillation. A 60% suspension of NaH in mineral
oil was washed with petroleum ether (bp 60-80 °C) and used. 1H
NMR spectra were recorded with a Bruker ACF 200 MHz spectrometer,
and 31P{1H} NMR spectra, on a Bruker AMX 400 MHz spectrometer
operating at 162 MHz and a Bruker ACF 200 MHz spectrometer
operating at 81.1 MHz. IR spectra were recorded on a Bio-Rad FTS-7
spectrophotometer. Elemental analyses were done with a Carlo Erba
Model 1106 elemental analyzer.
Preparation of Copper(I) Aryloxides. Copper(I) aryloxides were
prepared by the reported procedure.24 To a stirred suspension of NaH
(0.12 g, 3 mmol) in about 40 mL of CH2Cl2 or CH3CN was added the
phenol (3 mmol) under an atmosphere of dry, oxygen-free N2. When
the evolution of H2 ceased, CuCl (0.297 g, 3 mmol) was added. A
yellow precipitate of copper(I) aryloxide was formed which was used
immediately for further reactions.
Preparation of [Cu{µ-SC(dNMe)(OC6H4Me-4)}]6 (1). To cop-
per(I) 4-methylphenoxide prepared as above in CH2Cl2 was added
MeNCS (0.2 mL, 3 mmol) and the solution stirred for 8 h. The mixture
was filtered and concentrated to about 10 mL. Layering with petroleum
ether (bp 60-80 °C) yielded yellow-orange crystals. Yield: 37%. Anal.
Calcd for 1: C, 44.3; H, 4.11; N, 5.75. Found: C, 44.28; H, 4.18; N,
5.69. 1H NMR (CDCl3, 298 K): δ 7.15 (d, J ) 8.4 Hz, 2H, -OC6H4-
), δ 6.89 (d, J ) 8.37 Hz, 2H, -OC6H4-), δ 3.14 (S, 3H, MeNCS), δ
2.35 (S, 3H, Me). IR (neat) (in cm-1): 2917 (m), 2864 (w), 161 (s),
1601 (m), 1503 (s) (νCdN), 1260 (w), 1217 (s), 1157 (s), 1114 (s), 1017
(m), 895 (w), 818 (m), 467 (w).
(51) (a) Mandal, S. K.; Ho, D. M; Orchin, M. Organometallics 1993, 12,
1714. (b) Chisholm, M. H.; Extine, M. J. Am. Chem. Soc. 1975, 97,
5625.
(52) (a) Chisholm, M. H.; Extine, M. J. Am. Chem. Soc. 1977, 99, 782.
(b) Chisholm, M. H.; Extine, M. J. Am. Chem. Soc. 1977, 99, 792.
(c) Chisholm, M. H.; Extine, M. J. J. Chem. Soc., Chem. Commun.
1975, 438.
(53) (a) Parkin, I. P.; Folting, K. J. Chem. Soc., Dalton Trans. 1992, 2343.
(b) Chisholm, M. H.; Folting, K.; Haubrich, S. T.; Martin, J. D. Inorg.
Chim. Acta 1993, 213, 17. (c) Chisholm, M. H.; Folting, K.; Huffmann,
J. C.; Putilina, E. F.; Streib, W. E.; Tatz, R. J. Inorg. Chem. 1993, 32,
3771.
(54) Crans, D. C.; Felty, R. A.; Chen, H.; Eckert, H.; Das, N. Inorg. Chem.
1994, 33, 2427.
(55) (a) Simpson, R. D.; Bergman, R. G. Organometallics 1993, 12, 781.
(b) Simpson, R. D.; Bergman, R. G. Organometallics 1992, 11, 3980.
(56) (a) Blum, O.; Milstein, D. J. Am. Chem. Soc. 1995, 117, 4582. (b)
Fernandez, M. J.; Esteruelas, M. A.; Covarrubias, M.; Oro, L. A.;
Apreda, M.-C.; Foces-Foces, C.; Cano, F. H. Organometallics 1989,
8, 1158.
(57) (a) Purdy, A. P.; George, C. F.; Brewer, G. A. Inorg. Chem. 1992,
31, 2633. (b) Goel, S. C.; Kramer, K. S.; Gibbons, P. C.; Buhro, W.
E. Inorg. Chem. 1989, 28, 3619.
(58) (a) Koelle, U.; Wang, M. H.; Raabe, G. Organometallics 1991, 10,
2573. (b) Koelle, U.; Kang, B.-S.; Thewalt, U. Organometallics 1992,
11, 2893.
(59) (a) Menge, W. M. P. B.; Verkade, J. G. Inorg. Chem. 1991, 30, 4628.
(b) Naiini, A. A.; Menge, W. M. P. B.; Verkade, J. G. Inorg. Chem.
1991, 30, 5009. (c) Choquette, D. M.; Buschmann, W. E.; Olmstead,
M. M.; Planalp, R. P. Inorg. Chem. 1993, 32, 1062.
(60) Arney, D. J.; Wexler, D. A.; Wigley, D. E. Organometallics 1990, 9,
1282.
Preparation of [Cu{µ-SC(dNMe)(OC6H3(Me)2-2,6)}]n (2). To the
copper(I) aryloxide of 2,6-dimethylphenol prepared in CH3CN was
added MeNCS (0.2 mL, 3 mmol) and the solution stirred for 8 h. A
dirty white precipitate was formed, which was filtered out and washed
(61) Kapteijn, G. M.; Grove, D. M.; van Koten, G.; Smeets, W. J. J.; Spek,
A. L. Inorg. Chim. Acta 1993, 207, 131.

Copper(I) Aryloxides
Inorganic Chemistry, Vol. 35, No. 19, 1996 5433
Table 1. Exchange Reactions Studied and the Products Formed
heterocumulene
part
starting
compd
phosphine
added/present
phenol part
p-cresol
exchange with
PhNCS
products formed
MeNCS
hexamer
1 PPh3
[CuSC(OAr)dNPh(PPh3)2] + [CuSC(OAr)dNPh]6
(monomer + hexamer)
[CuSC(OAr)dNPh(PPh3)2] (monomer)
[CuSC(OAr)dS(PPh3)2] (monomer)
[CuSC(OAr0dS(PPh3)2] (monomer)
CuSC(OAr)dNPh]6 (hexamer)
2,6-dimethylphenol
p-cresol
2,6-dimethylphenol
p-cresol
2,6-dimethylphenol
p-cresol
p-chlorophenol
MeNCS
MeNCS
MeNCS
MeNCS
MeNCS
MeNCS
PhNCS
monomer
hexamer
monomer
hexamer
oligomer
hexamer
oligomer
2 PPh3
2 PPh3
2 PPh3
catal PPh3
catal PPh3
1 PPh3
PhNCS
CS2
CS2
PhNCS
PhNCS
[CuSC(OAr)dNPh]4 (tetramer)
3,5-dimethylpyrazole [CuSC(pyr)dNMe(PPh3)2] (monomer)
2,6-dimethylphenol
1 PPh3
[CuSC(OAr′)dNPh(PPh3)2 (monomer) +
[CuSC(OAr′)dNPh]4 (tetramer)
[CuSC(OAr)dS(PPh3)2 (monomer) + unreacted
starting material
[CuSC(OAr)dS(PPh3)2] (monomer) + unreacted
starting material
2,6-dimethylphenol
p-cresol
PhNCS
PhNCS
MeNCS
tetramer
hexamer
oligomer
1 PPh3
CS2
1 PPh3
CS2
2,6-dimethylphenol
catal PPh3
p-cresol
mixed clusters containing both 2,6-dimethylphenol
and p-cresol
Table 2. Crystallographic Data for 1 and 4
with acetonitrile. The amorphous white solid that was thus obtained
was only partially soluble in the usual organic solvents. The soluble
part does not form crystals, and only amorphous powders are obtained.
Redissolving this powder leaves an insoluble residue suggesting
polymerization of the CuL unit. The solublity behavior of this complex
is reminscent of other copper(I) complexes which have bridging ligands
and polymerize slowly. Yield: 65%. Anal. Calcd for 2: C, 46.60;
H, 4.66; N, 5.44. Found: C, 44.47; H, 4.45; N, 4.91. 1H NMR (CDCl3,
298 K): δ 7.07 (S, 3H, OC6H3-), δ 3.11 (s, 3H, MeNCS), δ 2.26 (S,
3H, Me), δ 2.16(S, 3H, Me). IR (neat) (in cm-1) 1592 (m) (νCdN),
1576 (s), 1474 (w), 1394 (w), 1267 (w), 1193 (m), 1149 (s), 1118 (s),
769 (w).
Preparation of [Cu{µ-SC(dNMe)(-C6H4Cl-4)}]n (3). Copper(I)
4-chlorophenoxide was prepared by adding Cu(CH3CN)4ClO4 (0.981
g, 3 mmol) to sodium 4-chlorophenoxide (3 mmol). To this deep
yellow suspension was added MeNCS (0.2 mL, 3 mmol), and the
mixture was stirred. Filtration yielded an orange solution. Orange
crystals were obtained on layering with petroleum ether (bp 60-80 °C).
Yield: 3%. A reaction carried out using CuCl instead of Cu(CH3-
CN)4ClO4 does not yield the inserted product. Anal. Calcd for 3 (with
0.2 CH2Cl2): C, 35.01; H, 2.63; N, 4.98. Found: C, 34.98; H, 2.67;
N, 4.63. 1H NMR (CDCl3, 298 K): δ 7.32 (d, J ) 8 Hz, 2H,
-OC6H4-) δ 6.95 (d, J ) 8 Hz, 2H, -OC6H4-), δ 5.3 (S, 0.4 H,
CH2Cl2), δ 3.15 (S, 3H, MeNCS). IR (Nujol) (in cm-1) 1595 (s) (νCdN),
1570 (s), 1475 (s), 1375 (w) 1210 (s), 1155 (s), 1105 (s), 1075 (s),
1010 (m), 890 (w), 820 (m).
Synthesis of [Cu{SC(dNMe)(OC6H3(Me)2-2,6)}(PPh3)2] (4). To
copper(I) 2,6-dimethyl phenoxide was added 3 equiv of PPh3 (2.36 g,
9 mmol), and the mixture was stirred for 0.5 h. MeNCS (0.2 mL, 3
mmol) was added and the stirring continued for 8 h. The resulting
solution was filtered, and the filtrate was pumped dry. The residue
was washed with petroleum ether (bp 60-80 °C) to obtain 4. Yield:
62%. Anal. Calcd for 4: C, 70.63; H, 537; N, 1.79. Found: C, 70.64;
H, 5.47; N, 1.39. 1H NMR (CDCl3, 298 K): δ 7.35-6.97 (m, 23H,
PPh3, -OC6H3-), δ 3.12 (s, 2.1 H, MeNCS), δ 3.02 (s, 0.9 H, MeNCS),
δ 2.18 (s, 6H, Me). IR (Nujol) (in cm-1): 1584 (w) (νCdN), 1560 (s),
1476 (s) 1434 (s), 1393 (m), 1309 (w), 1265 (w), 1202 (m), 1148 (m),
1093 (s), 1028 (m), 997 (w), 767 (m), 745 (s), 696 (s), 527 (m), 513
(s), 488 (m), 443 (w), 416 (w).
Synthesis of [Cu{µ-SC(dNPh)(OC6H4Cl-4)}]n (5). PhNCS (0.36
mL, 3 mmol) was added to the suspension of copper(I) 4-chlorophe-
noxide (3 mmol). The resulting suspension was stirred for 8 h and
then filtered. The filtrate was concentrated, and layering with petroleum
ether (bp 60-80 °C) yielded yellow orange crystals. Yield: 3%. The
yield was greater (7%) when Cu(CH3CN)4ClO4 was used to prepare
the copper(I) phenoxide. Anal. Calcd for 5: C, 47.58; H, 2.76; N,
4.29. Found: C, 47.53; H, 3.02; N, 3.88. 1H NMR (CDCl3, 298 K):
δ 7.45-6.49 (m, PhNCS, -OC6H4). IR (neat) (in cm-1): 1565 (s)
(νCdN), 1550 (m), 1479 (s), 1206 (s), 1120 (m), 1085 (m), 1066 (m),
1011 (w).
1
4
chem formula
fw
space group
a, Å
C54H60N6O6S6Cu6
C46H42NOSP2Cu
782.397
P1h
1462.74
R3h
12.365(3)
10.088(2)
11.302(1)
17.990(2)
94.06(1)
95.22(2)
103.94(1)
1974.4(7)
2
b, Å
c, Å
36.734(16)
R, deg
â, deg
γ, deg
V, Å3
Z
120
4863(3)
3
1.4981
21.722
20
F
calcd, g cm-3
1.316
7.186
20
0.7107
0.0361
0.0361
µ, cm-1
T, °C
λ, Å (Mo KR)
0.7107
0.0306
0.0358
final Ra
b
final Rw
a R(Fo) ) (∑||Fo| - |Fc||)/(∑|Fo|). b Rw(Fo) ) [∑w(|Fo| - |Fc|)2/
2
2
(∑w|Fo| )]1/2; w ) [σ2(Fo) + gFo ]-1
.
Reaction of Copper(I) 4-Methylphenoxide with MeNCS in the
Presence of PPh3. To the copper(I) phenoxide (3 mmol) of 4-meth-
ylphenol was added 2 equiv (6 mmol; 1.572 g) or 3 equiv (2.358 g; 9
mmol) of PPh3 followed by the addition of MeNCS (2 mL; 3 mmol).
The mixture was stirred for 8 h. TLC revealed the formation of a
mixture of products which could not be separated. IR and NMR spectra
reveal the presence of free MeNCS in addition to several products
containing MeNCS.
Exchange Reactions. (a) Exchange with PhNCS. In an NMR
tube, 1 equiv of the starting compound was mixed with the required
amount of PPh3 (1 equiv, 2 equiv, or catalytic) and 1 equiv of PhNCS.
CDCl3 was added, and the spectrum was recorded immediately. The
formation of the products with time was followed by recording the 1H
NMR spectra of the samples.
(b) Exchange with CS2. A 1 equiv amount of the starting compound
was mixed with the required amount of PPh3 (1 or 2 equiv) and 0.2
mL of CS2 in an NMR tube. The spectrum was recorded immediately
after adding CDCl3 to the sample. Product formation was followed
1
by recording the H NMR spectra of the samples periodically over a
few days.
(c) Exchange with 2,6-Dimethylphenol. A 1 equiv amount of the
starting compound was mixed with 1 equiv of PPh3 and 1 equiv of
2,6-dimethylphenol. CDCl3 was added to this, and an NMR spectrum
was recorded. The formation of the products was confirmed by
comparison of the NMR spectrum with that of authentic samples. The
progress of the reaction was monitored by recording the 1H NMR
spectra periodically.
(d) Exchange with 3,5-Dimethylpyrazole. A 1 equiv amount of
the hexamer 1 was mixed with 1 equiv of PPh3 and 1 equiv of 3,5-
dimethylpyrazole in an NMR tube. An NMR spectrum was recorded
as soon as the solvent (CDCl3) was added. The progress of the reaction
Synthesis of Complexes 6-15. Complexes 6-15 were prepared
by the method described earlier.24

5434 Inorganic Chemistry, Vol. 35, No. 19, 1996
Wycliff et al.
Table 3. Selected Bond Distances (Å) and Angles (deg) with Their
Estimated Standard Deviations in Parentheses for
[Cu{µ-SC(dNMe)(OC6H4-4-Me)}]6 (1)
Table 4. Selected Bond Distances (Å) and Angles (deg) with Their
Estimated Standard Deviations in Parentheses for
[Cu{SC(dNMe)(OC6H3-2,6-(Me)2}(PPh3)2] (4)
Cu1-S2
Cu1-S2′
Cu1-N4′
Cu1-Cu1′
Cu1-Cu1′′
S2-C3
2.239(1)
2.2432(9)
2.005(3)
3.1583(8)
2.8719(9)
1.742(3)
1.272(4)
1.363(4)
1.467(6)
1.402(4)
Cu1-S2-C3
Cu1-S2-Cu1′
S2-Cu1-S2′
N4-Cu1-S2
N4-Cu1-S2′
S2-C3-O6
S2-C3-N4
N4-C3-O6
C3-N4-C5
C3-O6-C7
103.2(1)
89.6(1)
Cu1-N1
Cu1-S1
Cu1-P1
Cu1-P2
Cu1-C1
N1-C1
N1-C10
S1-C1
2.14(2)
P1-C111
P1-C121
P1-C131
P2-C211
P2-C221
P2-C231
C1-O1
1.828(4)
1.817(3)
1.836(3)
1.824(4)
1.842(4)
1.828(3)
1.383(4)
1.388(5)
2.460(1)
2.265(1)
2.268(1)
2.602(3)
1.280(7)
1.46(2)
115.5(1)
119.8(2)
117.9(2)
118.6(2)
123.6(3)
117.9(3)
119.2(3)
120.1(3)
C3-N4
C3-O6
1.716(4)
O1-C11
N4-C5
P1-Cu1-P2
S1-Cu1-P2
S1-Cu1-P1
N1-Cu1-P2
N1-Cu1-P1
N1-Cu1-S1
Cu1-N1-C10
Cu1-N1-C1
C1-N1-C10
Cu1-S1-C1
126.91(6)
120.54(6)
108.78(5)
104.4(1)
111.0(1)
68.8(1)
144.3(4)
95.9(5)
119.8(5)
74.7(2)
Cu1-P1-C131
Cu1-P1-C121
Cu1-P1-C111
N1-C1-S1
Cu1-C1-S1
Cu1-C1-N1
S1-C1-O1
N1-C1-O1
Cu1-C1-O1
C1-O1-C11
116.1(1)
113.1(1)
116.6(1)
120.60(5)
65.8(1)
O6-C7
was monitored by TLC and the appearance/disappearance of peaks
characteristic of the reactants and products.
A summary of the various exchange reactions studied is given in
Table 1.
54.9(4)
122.3(3)
117.1(5)
171.6(3)
120.6(3)
Deinsertion Reactions. A 1 equiv amount of the oligomer was
mixed with the required amount (1, 2, or 3 equiv) of PPh3 in an NMR
tube. CDCl3 was added, and the spectrum was recorded immediately.
The progress of the reaction was followed by recording the NMR
spectra periodically. The formation of various products was identified
by the appearance of characteristic peaks in the NMR spectrum.
Experimental Details of Crystallography. An orange crystal of
1 suitable for the diffraction study was obtained by crystallization of 1
from a mixture of dichloromethane and petroleum ether (bp 60-80
°C) (1:1). Intensity data were collected on an Enraf-Nonius CAD4
diffractometer using graphite-monochromated Mo KR radiation. Data
collection parameters are summarized in Table 2. Three intensity
control reflections, measured once in every 3600 s of exposure time,
showed no significant decay. Data was corrected for Lorentz, polariza-
tion, and absorption (DIFABS;62 transmission coefficient, 0.933-1.046)
also. The filtrate obtained in the reaction between copper(I) 2,6-
dimethylphenoxide and MeNCS in the presence of 3 equiv of PPh3
was pumped dry. Crystals of 4 were obtained from the petroleum ether
(bp 60-80 °C) extract of this residue. A pale yellow crystal of 4 was
sealed in a Lindemann capillary along with the mother liquor as it was
unstable outside the mother liquor. Data collection procedures were
similar to that of 1.
and subsequent Fourier syntheses using the SHELX system63 of
programs. The hydrogen atoms were located from the difference
Fourier map. Non-hydrogen atoms were refined anisotropically, and
the hydrogen atoms, isotropically. The refinement converged at R )
0.0306 and 0.0361 for 1 and 4, respectively. Details of the crystal-
lographic analyses are summarized in Tables 2-4 and in the Supporting
Information.
Acknowledgment. The financial support of the CSIR, India,
through a grant to A.G.S. and to C.W. through a Senior Research
Fellowship is gratefully acknowledged.
Supporting Information Available: For complexes 1 and 4, tables
listing positional and U parameters for all atoms, anisotropic thermal
parameters, and complete bond lengths and bond angles (12 pages).
Ordering information is given on any current masthead page.
IC9516424
(63) (a) Sheldrick, G. M. SHELXS-86 Program for Crystal Structure
Determination, University of Go¨ttingen, Republic of Germany, 1986.
(b) Sheldrick, G. M. SHELX-76 Program for Crystal Structure
Refinement, University of Cambridge, U.K., 1976.
The structures of 1 and 4 were solved by the heavy atom method
(62) Walker, N.; Stuart, D. Acta Crystallogr. A 1983, 39, 158.