Copper(I) complexes derived from mono- and diphosphino-boranes: Cu→b interactions supported by arene coordination

Article abstract of DOI:10.1021/ic901896z

The monophosphino-boranes o-iPr₂P(C₆H ₄)BR₂ (1: R = Ph and 3: R = Cy) and diphosphino-boranes [o-R₂P(C₆H₄)]₂BPh (5: R = Ph and 6: R = iPr) readily react with CuCl to a

Full text of DOI:10.1021/ic901896z

Inorg. Chem. 2010, 49, 3983–3990 3983
DOI: 10.1021/ic901896z
Copper(I) Complexes derived from Mono- and Diphosphino-Boranes: CufB
Interactions Supported by Arene Coordination
M. Sircoglou,† S. Bontemps,† M. Mercy,‡ K. Miqueu,§ S. Ladeira, N. Saffon, L. Maron,*,‡
G. Bouhadir,*,† and D. Bourissou*,†
†
ꢀ
Universite de Toulouse, UPS, LHFA, 118 route de Narbonne, F-31062 Toulouse, France, and CNRS, LHFA
‡
ꢀ
UMR 5069, F-31062 Toulouse, France, Universite de Toulouse, INSA, UPS, LPCNO, 135 avenue de Rangueil,
F-31077 Toulouse, France, and CNRS, LPCNO UMR 5215, F-31077 Toulouse, France, §Institut
ꢀ
ꢀ
Pluridisciplinaire de Recherche sur l’Environnement et les Materiaux UMR-CNRS 5254, Universite de Pau et
^
ꢀ
ꢀ
ꢀ
des Pays de l’Adour, Technopole Helioparc, 2 avenue du President Angot, F-64053 Pau, France, and Universite
ꢀ ꢀ
ꢀ
de Toulouse, UPS, Structure Federative Toulousaine en Chimie Moleculaire, FR2599, 118 Route de Narbonne,
F-31062 Toulouse, France
Received October 5, 2009
The monophosphino-boranes o-iPr2P(C6H4)BR2 (1: R = Ph and 3: R = Cy) and diphosphino-boranes [o-R2P(C6H4)]2BPh
(5: R = Ph and 6: R = iPr) readily react with CuCl to afford the corresponding complexes {[o-iPr2P(C6H4)BPh2]Cu(μ-Cl)}2
2, {[o-iPr2P(C6H4)BCy2]Cu(μ-Cl)}2 4, {[o-Ph2P(C6H4)]2BPh}CuCl 7, and {[o-iPr2P(C6H4)]2BPh}CuCl 8. The presence
of CufB interactions supported by arene coordination within complexes 2, 7, and 8 has been unambiguously evidenced
by NMR spectroscopy and X-ray diffraction studies. The unique η2-BC coordination mode adopted by complexes 7 and 8
has been thoroughly analyzed by density-functional theory (DFT) calculations.
Introduction
to engage in MfB interactions (M = Rh, Pd, Pt) via
the unprecedented η3-BCipsoCortho coordination of a BPh
Over the past few years, the ability of Lewis acids to act as
σ-acceptor, Z-type1 ligands has attracted growing interest.2-4
In particular, the coordination of ambiphilic ligands combin-
ing phosphine and borane moieties has allowed significant
advances in MfB interactions.5-9 Indeed, we have shown
that such MfB interactions (M = Rh, Ni, Pd, Pt, Cu, Ag,
Au) are readily accessible by coordination of tri-, di-, and
even monophosphino-boranes (complexes of type A-C).7 In
the mean time, Emslie et al. demonstrated that a rigid
phosphino-thioether-borane ligand (PSB) is also prone
(6) Transition metalfborane interactions were first structurally authen-
ticated within metal boratranes derived from hydrido tris(imazolyl)borate
ligands: (a) Hill, A. F.; Owen, G. R.; White, A. J. P.; Williams, D. J. Angew.
Chem., Int. Ed. 1999, 38, 2759–2761. (b) Foreman, M. R. St.-J.; Hill, A. F.;
White, A. J. P.; Williams, D. J. Organometallics 2004, 23, 913–916. (c) Crossley,
I. R.; Hill, A. F. Organometallics 2004, 23, 5656–5658. (d) Mihalcik, D. J.;
White, J. L.; Tanski, J. M.; Zakharov, L. N.; Yap, G. P. A.; Incarvito, C. D.;
Rheingold, A. L.; Rabinovitch, D. Dalton Trans. 2004, 1626–1634. (e) Crossley,
I. R.; Hill, A. F.; Willis, A. C. Organometallics 2005, 24, 1062–1064. (f) Crossley,
I. R.; Hill, A. F.; Humphrey, E. R.; Willis, A. C. Organometallics 2005, 24, 4083–
4086. (g) Crossley, I. R.; Foreman, M. R. St.-J.; Hill, A. F.; White, A. J. P.;
Williams, D. J. Chem. Commun. 2005, 221–223. (h) Crossley, I. R.; Hill, A. F.;
Willis, A. C. Organometallics 2006, 25, 289–299. (i) Landry, V. K.; Melnick, J.
G.; Buccella, D.; Pang, K.; Ulichny, J. C.; Parkin, G. Inorg. Chem. 2006, 45,
2588–2597. (j) Senda, S.; Ohki, Y.; Hirayama, T.; Toda, D.; Chen, J.-L.;
Matsumoto, T.; Kawaguchi, H.; Tatsumi, K. Inorg. Chem. 2006, 45, 9914–
9925. (k) Pang, K.; Quan, S. M.; Parkin, G. Chem. Commun. 2006, 5015–5017.
(l) Figueroa, J. S.; Melnick, J. G.; Parkin, G. Inorg. Chem. 2006, 45, 7056–7058.
(m) Blagg, R. J.; Charmant, J. P. H.; Connelly, N. G.; Haddow, M. F.; Orpen, A. G.
Chem. Commun. 2006, 2350–2352. (n) Hill, A. F. Organometallics 2006, 25,
4741–4743. (o) Parkin, G. Organometallics 2006, 25, 4744–4747. (p) Crossley, I.
R.; Hill, A. F.; Willis, A. C. Organometallics 2007, 26, 3891–3895. (q) Crossley,
I. R.; Hill, A. F. Dalton Trans. 2008, 201–203. (r) Crossley, I. R.; Hill, A. F.;
Willis, A. C. Organometallics 2008, 27, 312–315. (s) Crossley, I. R.; Foreman,
M. R. St.-J.; Hill, A. F.; Owen, G. R.; White, A. J. P.; Williams, D. J.; Willis, A. C.
Organometallics 2008, 27, 381–386. (t) Pang, K.; Tanski, J. M.; Parkin, G. Chem.
Commun. 2008, 1008–1010. (u) Tsoureas, N.; Haddow, M. F.; Hamilton, A.;
Owen, G. R. Chem. Commun. 2009, 2538–3540. (v) Tsoureas, N.; Bevis, T.;
Butts, C. P.; Hamilton, A.; Owen, G. R. Organometallics 2009, 28, 5222–5232.
*To whom correspondence should be addressed. E-mail: dbouriss@
chimie.ups-tlse.fr.
(1) (a) King, R. B. Adv. Chem. Ser. 1967, 62, 203–220. (b) Green, M. L. H.
J. Organomet. Chem. 1995, 500, 127–148.
(2) For a recent review on boron complexes, see: Braunschweig, H.;
Kollann, C.; Rais, D. Angew. Chem., Int. Ed. 2006, 45, 5254–5274.
(3) For alane and gallane complexes, see: (a) Burlitch, J. M.; Leonowicz,
M. E.; Petersen, R. B.; Hughes, R. E. Inorg. Chem. 1979, 18, 1097–1105.
(b) Golden, J. T.; Peterson, T. H.; Holland, P. L.; Bergman, R. G.; Andersen, R. A.
J. Am. Chem. Soc. 1998, 120, 223–224. (c) Braunschweig, H.; Gruss, K.;
Radacki, K. Angew. Chem., Int. Ed. 2007, 46, 7782–7784. (d) Braunschweig, H.;
Gruss, K.; Radacki, K. Inorg. Chem. 2008, 47, 8595–8697. (e) Sircoglou, M.;
Mercy, M.; Saffon, N.; Coppel, Y.; Bouhadir, G.; Maron, L.; Bourissou, D.
Angew. Chem., Int. Ed. 2009, 48, 3454–3457.
(4) For dative MfBe interactions, see: Braunschweig, H.; Gruss, K.;
Radacki, K. Angew. Chem., Int. Ed. 2009, 48, 4239–4241.
(5) For recent reviews, see: (a) Fontaine, F.-G.; Boudreau, J.; Thibault,
M.-H. Eur. J. Inorg. Chem. 2008, 5439–5454. (c) Kuzu, I.; Krummenacher, I.;
Meyer, J.; Armbruster, F.; Breher, F. Dalton Trans. 2008, 5836–5865.
r
2009 American Chemical Society
Published on Web 11/05/2009
pubs.acs.org/IC

3984 Inorganic Chemistry, Vol. 49, No. 9, 2010
Sircoglou et al.
Scheme 1. Synthesis and Coordination to Copper(I) of the Mono-
phosphino-Borane 1
Results and Discussion
Starting from (o-bromophenyl)diisopropylphosphine, the
monophosphino-borane (MPB) 1 was obtained in 94% yield
by bromine-lithium exchange followed by electrophilic
trapping with chlorodiphenylborane (Scheme 1). The 31P-
{1H} and 11B{1H} NMR chemical shifts for 1 (24.8 and
5 ppm, respectively) are similar to those observed in the solid
state for the related triphosphino-borane [o-iPr2P(C6H4)]3B
(TPB) (δ31P: 28.5 ppm and δ11B: 13.0 ppm),14 suggesting the
presence of an intramolecular PfB interaction. Density-
functional theory (DFT) calculations performed on the real
molecule at the [B3PW91/SDDþpol(P),6-31G**(B,C,H)]
level of theory confirmed this hypothesis.15 Indeed, the
experimental 31P and 11B NMR chemical shifts are in good
agreement with those computed using the Gauge Including
Atomic Orbitals (GIAO) method for the closed form of 1
(31.0 and 10.7 ppm, respectively), but differ significantly
from those of the related open form (without PfB) that was
found 1.5 kcal/mol higher in energy (δ31P: 16.5 ppm and
δ11B: 61.8 ppm). The copper complex 2 was prepared by
adding the monophosphino-borane 1 to a suspension of
CuCl in dichloromethane (DCM) at -78 °C. Upon warming
to room temperature (RT), the reaction mixture rapidly
became homogeneous and turned pale yellow. After precipi-
tation with diethylether, complex 2 wasisolatedin 85%yield.
The 11B{1H} NMR resonance observed at 58 ppm is close to
that exhibitedby the (TPB)CuCl complex of type A (54 ppm),
suggesting the presence of a weak CufB interaction in 2.7f
To get more insight into the precise structure of 2, single
crystals suitable for X-ray diffraction (XRD) analysis were
prepared from a saturated dichloromethane solution at RT
(mp 138-140 °C). Complex 2 adopts a centrosymmetric
chloro-bridged dimeric structure in the solid state (Figure
2). The copper center is surrounded by the phosphorus atom,
two chlorine atoms, and a BPh moiety organized in a
tetrahedral environment. The CuB distance in 2 [2.555(2)
A] is appreciably shorter than the sum of van der Waals radii
(3.80 A),16 and very similar to that of the (TPB)CuCl
complex of type A [2.508(2) A].7f The Cipso and one of the
Cortho atoms of a phenyl substituent at boron are also close to
the copper center. The corresponding CCu distances
[2.339(2) and 2.596(2) A, respectively] are in the same range
as those reported for η2-CC arylborate copper complexes
(CCu distances of 2.32-2.68 A were found in the polymeric
[PhnB(CH2SR)4-nCu] complex).17 This data indicates
η3-BCC coordination of the BPh moiety in 2. This contrasts
with the η1-B coordination induced by the metallaboratrane
Figure 1. Structure of complexes A-E featuring η1-B, η3-BCipsoCortho
and η1-Cipso coordinated arylborane fragments.
,
fragment (complexes of type D).8 The coordination of
arylboranes to transition metals was at that time limited to
weak η1-Cipso coordination, as observed by Power et al. in the
homoleptic complexes E featuring two borylamide ligands
(Figure 1).10,11
To shed more light on the different coordination behaviors
of the B(aryl) fragment in complexes A-C (η1-B), D (η3-
BCC), and E (η1-C), we recently became interested in copper
complexes derived from mono- and diphosphino-boranes.
To date, CufB interaction has only been authenticatedwhen
enforced in a metallaboratrane cage structure (complex of
type A).7f,12,13 Here, the related complexes of type B and C
are shown to display CufB interactions that are supported
by arene coordination. The original η2-BC coordination
mode evidenced in complexes of type B has been thoroughly
investigated, both experimentally and theoretically.
(7) (a) Bontemps, S.; Gornitzka, H.; Bouhadir, G.; Miqueu, K.;
Bourissou, D. Angew. Chem., Int. Ed. 2006, 45, 1611–1614. (b) Bontemps,
S.; Bouhadir, G.; Miqueu, K.; Bourissou, D. J. Am. Chem. Soc. 2006, 128,
12056–12057. (c) Sircoglou, M.; Bontemps, S.; Mercy, M.; Saffon, N.; Takahashi,
M.; Bouhadir, G.; Maron, L.; Bourissou, D. Angew. Chem., Int. Ed. 2007, 46,
8583–8586. (d) Bontemps, S.; Sircoglou, M.; Bouhadir, G.; Puschmann, H.;
Howard, J. A. K.; Dyer, P. W.; Miqueu, K.; Bourissou, D. Chem.;Eur. J. 2008,
14, 731–740. (e) Bontemps, S.; Bouhadir, G.; Gu, W.; Mercy, M.; Chen, C.-H.;
Foxman, B. M.; Maron, L.; Ozerov, O. V.; Bourissou, D. Angew. Chem., Int. Ed.
2008, 47, 1481–1484. (f) Sircoglou, M.; Bontemps, S.; Bouhadir, G.; Saffon, N.;
Miqueu, K.; Gu, W.; Mercy, M.; Chen, C.-H.; Foxman, B. M.; Maron, L.; Ozerov,
O. V.; Bourissou, D. J. Am. Chem. Soc. 2008, 130, 16729–16738.
(8) (a) Oakley, S. R.; Parker, K. D.; Emslie, D. J. H.; Vargas-Baca, I.;
Robertson, C. M.; Harrington, L. E.; Britten, J. F. Organometallics 2006, 25,
5835–5838. (b) Emslie, D. J. H.; Harrington, L. E.; Jenkins, H. A.; Robertson, C.
M.; Britten, J. F. Organometallics 2008, 27, 5317–5325.
(9) Wolczanski reported borane adducts with [Ta(OSitBu3)3] and dis-
cussed the contribution of TafB interactions on the basis of spectroscopic
data: Bonanno, J. B.; Henry, T. P.; Wolczanski, P. T.; Pierpont, A. W.;
Cundari, T. R. Inorg. Chem. 2007, 46, 1222–1232.
(10) Chen, H.; Bartlett, R. A.; Olmstead, M. M.; Power, P. P.; Shoner, S.
C. J. Am. Chem. Soc. 1990, 112, 1048–1055.
(11) In complexes E, relatively short MB distances (2.50-2.85 A) are
imposed geometrically, but the orientation of the vacant 2p orbital at boron
precludes direct MfB interaction.
(14) Bontemps, S.; Bouhadir, G.; Dyer, P. W.; Miqueu, K.; Bourissou, D.
Inorg. Chem. 2007, 46, 5149–5151.
(15) See Supporting Information for details.
(12) For
a tetranuclear copper(I) complex featuring two bridging
N-heterocyclic boryl ligands, see: Kajiwara, T.; Terabayashi, T.; Yamashita,
M.; Nozaki, K. Angew. Chem., Int. Ed. 2008, 47, 6606–6610.
(16) Batsanov, S. S. Inorg. Mater. 2001, 37, 871–885.
(13) The contribution of a weak CufB interaction has been pointed out
in a copper(I) complex featuring an R-boroalkyl ligand: Laitar, D. S.; Tsui,
E. Y.; Sadighi, J. P. Organometallics 2006, 25, 2405–2408.
(17) (a) Ohrenberg, C.; Riordan, C. G.; Liable-Sands, L.; Rheignold, A.
L. Coord. Chem. Rev. 1998, 174, 301–311. (b) Ohrenberg, C.; Liable-Sands, L.;
Rheignold, A. L.; Riordan, C. G. Inorg. Chem. 2001, 40, 4276–4283.

Article
Inorganic Chemistry, Vol. 49, No. 9, 2010 3985
Figure 3. Molecular structure of 4 with hydrogen atoms and solvent
molecules omitted. Selected bond distances (A) and angles (deg): P1-Cu1
2.173(2), Cu1-Cl1 2.379(2), Cu1-Cl1A 2.237(2), P1-Cu1-Cl1 116.39(4),
P1-Cu1-Cl1A 145.06(5), Cl1-Cu1-Cl1A 96.87(4).
Figure 2. Molecular structure of 2 with hydrogen atoms and solvent
molecules omitted. Selected bond distances (A) and angles (deg): P1-
Cu1 2.215(1), Cu1-Cl1 2.339(1), Cu1-Cl1A 2.353(1), Cu1-B1 2.555(2),
Cu1-C13 2.339(2), Cu1-C14 2.596(2), P1-Cu1-Cl1 113.90(2), P1-
Cu1-Cl1A 123.33(2) Cl1-Cu1-Cl1A 94.14(2).
observed at 82.5 ppm is diagnostic for tricoordinate dialkyl-
arylboranes,20 suggesting the absence of significant CufB
interaction in 4. This was unambiguously confirmed by X-ray
crystallography, single crystals being obtained from a satu-
rated dichloromethane solution at -40 °C (mp 124-126 °C).
Accordingly, complex 4 also adopts a centrosymmetric
chloro-bridged dimeric structure in the solid state (Figure
3), but the copper center is essentially tricoordinate and its
geometry tends to trigonal planar (the sum of P1Cu1Cl1,
P1Cu1Cl1A, and Cl1Cu1Cl1A bond angles equals 358.3° in 4
vs 331.4° in 2). The empty 2p(B) orbitalpoints inthe direction
of the metal (the CuP and CipsoB vectors are almost parallel,
with a torsion angle of only 8.0°), but the BCu distance
(3.05 A) significantly exceeds that of complex 2, indicating
negligible, if any, CufB interaction in 4.21,22 This argues
in favor of cooperative coordination of the boron atom and
π-system of the phenyl ring toward copper in complex 2.
Upon coordination to CuCl, the monophosphino-borane
1 and triphosphino-borane TPB lead to η3-BCC and η1-B
complexes, respectively. To gain more insight into the precise
influence of geometric constraints and stereoelectronic effects
in these contrasting coordination behaviors, we then inves-
tigated the coordination of related diphosphino-borane
(DPB) ligands. Because of the presence of two donating
phosphine buttresses at boron, the copper center was ex-
pected to be less coordinatively and electronically unsatu-
rated than in the monophosphino-borane complex 2. Note
that the AuCl complexes of type B derived from the DPB
ligands 5 and 6 (featuring phenyl and isopropyl substituents
at phosphorus, respectively) have been recently shown to
adopt η1-B coordination, leading to unprecedented square-
planar geometry for tetracoordinate Au(I) complexes.7c The
participation of the phenyl ring at boron to the coordination
is more likely with copper, that tends to form complexes of
higher coordination numbers than gold.23 By allowing 5 and
Scheme 2. Synthesis of the Copper(I) Monophosphino-Borane
Complex 4
structure in the (TPB)CuCl complex of type A,7f but parallels
what hadbeenobservedby Emslie etal. uponcoordination of
the rigid PSB ligand to rhodium, nickel, and palladium.8
Notably, the geometry of the BPh fragment is almost un-
changed upon coordination to copper: (i) the corresponding
BCipso and CipsoCortho bond lengths are identical to those of
the other phenyl substituent at boron, (ii) the Cipso and Cortho
atoms are in perfectly planar environments, and (iii) the
P
boron atom is only slightly pyramidalized [ (C-B-C) =
358.4°].18 In addition, only three (respectively four) signals
1
are observed for the BPh2 fragment in the H (respectively
13C) NMR spectra of 2. This indicates that the two phenyl
substituents at boron rapidly exchange at the NMR time
scale,19 something that may occur either by decoordination/
recoordination or by slippage of copper.
The phenyl substituents at boron were then replaced by
cyclohexyl groups so as to ascertain the influence of the
CipsoCortho-coordination on the CufB interaction. The tar-
geted complex 4 was prepared by reacting the previously
reported monophosphino-borane o-iPr2P(C6H4)BCy2 37b
with CuCl (Scheme 2). The 11B{1H} NMR resonance signal
(18) MfB interactions with only slight boron pyramidalization have
been observed in the [o-iPr2P(C6H4)BFlu] AuCl complex7b and in the
3
heterobimetallic rhodium-iron complex derived from the PSB ligand.8a
Perfectly planar environments have even been found in unsymmetrically
bridged boryl complexes: (a) Curtis, D.; Lesley, M. J. G.; Norman, N. C.;
Orpen, A. G.; Starbuck, J. J. Chem. Soc., Dalton Trans. 1999, 1687–1694. (b)
Westcott, S. A.; Marder, T. B.; Baker, R. T.; Harlow, R. L.; Calabrese, J. C.; Lam,
K. C.; Lin, Z. Polyhedron 2004, 23, 2665–2677.
(21) For comparison, a weak AufB interaction was found in the related
gold complex (3) AuCl.7b This corroborates the strengthening of MfB
interactions when going down group 11, as previously evidenced in TPB
complexes of type A.7f
(19) The very poor solubility of complex 2 prevents the study of this
fluxional behavior at low temperature.
(22) The (μ-Cl)2 bridge prevents M-ClfB interaction, as observed
previously in mononuclear Pd and Rh complexes derived from the phos-
phino-borane 3. See ref 7b and (a) Bontemps, S.; Bouhadir, G.; Apperley, D.
C.; Dyer, P. W.; Miqueu, K.; Bourissou, D. Chem. Asian. J. 2009, 4, 428–435.
(23) Carvajal, M. A.; Novoa, J. J.; Alvarez, S. J. Am. Chem. Soc. 2004,
126, 1465–1477.
(20) For example, 11B NMR chemical shifts of 77.6 ppm and 80.9 ppm
have been reported for PhBMe2 and PhBBN, respectively: (a) Wrackmeyer,
€
B.; Noth, H. Chem. Ber. 1976, 109, 1075–1088. (b) Kramer, G. W.; Brown, H.
C. J. Organomet. Chem. 1974, 73, 1–15.

3986 Inorganic Chemistry, Vol. 49, No. 9, 2010
Sircoglou et al.
the BPh fragment. The metrical data for complex 7 will be
discussed first (Figure 4). The CuB distance [2.396(5) A]
is shorter than in the MPB complex 2 [2.555(2) A] and even
than in the TPB complex of type A [2.508(2) A],7f suggesting a
rather strong interaction.25 The CuCipso distance [2.364(4) A] is
very similar to that of 2 [2.339(2) A]. This is the only
short contact observed between the copper center and the
phenyl ring at boron, the other carbon atoms standing at
>2.9 A. Thus, the BPh fragment in complex 7 adopts a
η2-BC coordination mode rather than η3-BCC, as observed
in complex 2. We assume that the higher donating character of
the second phosphino buttress in complex 7 compared with the
chloride-bridge in complex 2 plays an important role in this
feature. The participation of the BPh fragment in the coordina-
tion also induces in complex 7 a noticeable pyramidalization of
the copper environment (sum of P1Cu1P2, P1Cu1Cl1 and
P2Cu1Cl1 bond angles = 331.4°), but no elongation of the
BCipso bond [1.566(3) A compared to 1.585(3) and 1.571(3) A
for the BCipso bonds of the o-phenylene linkers]. Note also that
two phenyl rings at the phosphorus atoms are almost
parallel (the mean planes of the two rings are tilted by only
9°) and close enough (the distance between the two cen-
troids is 3.63 A) to suggest some π-π interaction. The
solid-state structure of 8 is composed of four crystallo-
graphically independent molecules. One of them, referred
to as 8a, resembles 7 (Figure 5). The CuB and CuCipso
distances in 8a (2.379(5) and 2.414(4) A, respectively) are
very similar to those of 7, indicating here also symmetric
η2-BC coordination of the BPh fragment. The three
other molecules present in the unit cell are almost iden-
tical (largest deviation in BCu, BCipso, CuCipso bond
lengths of less than 0.1 A)15 and will be described here as
an average form, referred to as 8b. The CuB distance in 8b
(2.49 A) exceeds that of 8a by about 5%, while the CuCipso
distance (2.66 A) is elongated by 10%. Accordingly, the
η2-BC coordination is slightly weaker and dissymmetrized
in 8b compared to 8a, suggesting some flexibility in the
coordination of the BPh fragment to the metal center.
At this stage, it is interesting to note that, with copper(I),
η2-coordination of arenes is well-known,26 but only a very
few η1-complexes have been reported to date.27,28 In addi-
tion, η2-BC coordination has only been authenticated in an
iron complex featuring the methyleneborane Flu=BTmp
(Flu: 9-fluorenylidene, Tmp: 20,20,60,60-tetramethylpiperidino),29
and in a mixed cluster of palladium and rhenium capped by
Figure 4. Molecular structure of 7 with hydrogen atoms and solvent
molecules omitted.
Scheme 3. Synthesis of the Copper(I) Diphosphino-Borane Com-
plexes 7 and 8
6 to react with CuCl in DCM, the desired complexes 7 and 8
were obtained as yellow solids in 43 and 94% yield, respec-
tively (Scheme 3). The 31P{1H} NMR spectra of 7 and 8
exhibit singlets at 3.4 and 21.5 ppm, respectively, indicating
symmetric coordination of the two phosphorus atoms to the
copper center. The 11B{1H} NMR chemical shifts for com-
plexes 7 (56 ppm) and 8 (55 ppm) are very similar to those of 2
(58 ppm) and (TPB)CuCl (54 ppm),7f supporting the pre-
sence of weak CufB interactions. Notably, the 13C NMR
resonance signals associated with the Cipso atom of the BPh
fragment (δ = 132.7 ppm for 7 and 140.3 ppm for 8) appear
at significantly lower frequencies than those of the free
ligands (∼148 ppm)7a,c and related η1-B gold complexes of
type B (∼151 ppm).7c The 13C NMR signals of aryl rings are
typically shifted to lower frequency upon coordination, shifts
of 5 to 10 ppm being classically observed with copper.24 The
spectroscopic data thus suggest the participation of both B
and Cipso atoms upon coordination of the DPB ligands 5 and
6 to CuCl.
(25) The sum of covalent radii equals 2.16 A according to (a) Cordero, B.;
ꢀ
ꢀ
Gomez, V.; Pletro-Prats, A. E.; Reves, M.; Echeverrıa, J.; Cremades, E.;
´
ꢀ
Barragan, F.; Alvarez, S. Dalton Trans. 2008, 2832–2838.
(26) Hubig, S. M.; Lindeman, S. V.; Kochi, J. K. Coord. Chem. Rev. 2000,
200-202, 831–873.
(27) For η1-arene complexes of copper(I) supported by polydentate
nitrogen-containing ligands, see refs 22 and (a) Mascal, M.; Hansen, J.;
Blake, A. J.; Li, W.-S. Chem. Commun. 1998, 355–356. (b) Osako, T.; Ueno, Y.;
Tachi, Y.; Itoh, S. Inorg. Chem. 2003, 42, 8087–8097.
Single crystals of 7 (mp 259 °C) and 8 (mp 200-201 °C)
were grown from saturated DCM solutions at RT, and XRD
analyses were carried out. Both complexes adopt monomeric
structures in the solid state, with the copper center being
ligated by the two phosphorus atoms, the chlorine atom, and
(28) For a weak, unsupported η1-benzene complex of copper(I), see (a) Fox,
B. J.; Sun, Q. Y.; DiPasquale, A. G.; Fox, A. R.; Rheingold, A. L.; Figueroa, J. S.
Inorg. Chem. 2008, 47, 9010–9020.
(29) η2-coordination of
a π-BC bond has been reported in the
[(Flu=BPh)Fe(CO)4] complex: Channareddy, S.; Linti, G.; Noth, H.
Angew. Chem., Int. Ed. Engl. 1988, 27, 1331–1332. The corresponding
[(Flu=BPh)Fe(CO)3] complex features an η4-coordinated borabutadiene moiety:
Channareddy, S.; Linti, G.; Noth, H. Angew. Chem., Int. Ed. Engl. 1990, 29,
199–201. A strongly delocalized bonding interaction involving B, Cipso (Cp), and
Fe has also been authenticated in ferrocenylboranes: Scheibitz, M.; Bolte, M.;
Bats, J. W.; Lerner, H.-W.; Nowik, I.; Herber, R. H.; Krapp, A.; Lein, M.;
Holthausen, M. C.; Wagner, M. Chem.;Eur. J. 2005, 11, 584–603.
(24) (a) Osako, T.; Tachi, Y.; Taki, M.; Fukuzumi, S.; Itoh, S. Inorg.
Chem. 2001, 40, 6604–6609. (b) Osako, T.; Tachi, Y.; Doe, M.; Shiro, M.;
Ohkubo, S.; Fukuzumi, S.; Itoh, S. Chem.;Eur. J. 2004, 10, 237–246. (c)
Osako, T.; Terada, S.; Tosha, T.; Nagatomo, S.; Furutachi, H.; Fujinami, S.;
Kitagawa, T.; Suzuki, M.; Itoh, S. Dalton Trans. 2005, 3514–3521.

Article
Inorganic Chemistry, Vol. 49, No. 9, 2010 3987
Figure 5. (a) Molecular structure of 8 with hydrogen atoms and solvent molecules omitted (only one of the four independent molecules of the unit cell,
namely, 8a, is shown for clarity). (b) Superposed side views of 8a (pink) and 8b (blue), the mean form of the three other molecules present in the unit cell
(isopropyl substituents at phosphorus omitted for clarity).
Figure 6. Molecular orbital plots associated with the three-center CuBCipso interaction within 7*. For 8a*, see Supporting Information, Figure S1.15
two phenylboroles Ph-B(C4H4).30 Thus, the complexes 7
Table 1. Experimental and Theoretical Data for Complexes 7 and 8a
and 8 derived from diphosphino-boranes provide the first
complex
PCu
CuB
CuCipso
CuCl
ΔG298
examples of η2-BC coordination involving a triarylborane,
and bridge thereby the gap between the η1-B and η3-BCC
coordination modes described previously.7,8
7
X-ray 2.241(2) 2.396(5) 2.364(4) 2.230(2)
2.244(2)
To further probe the η2-BC coordination mode adopted by
7 and 8a, DFT calculations were carried out on the real
complexes. Calculations were performed at the B3PW91/
SDD(Cu,P,Cl),6-31G**(other atoms) level of theory, that
has already proved appropriate for transition metal com-
plexes derived from ambiphilic ligands.3e,7,31 The optimized
geometries for 7*/8a* fit closely with those determined
experimentally for 7/8a (Table 1), and nicely reproduce the
symmetric η2-BC coordination (with computed CuB/CuCipso
distances of 2.43/2.46 A for 7*, and 2.41/2.50 A for 8a*).
Analysis of the molecular orbitals of 7* and 8a* indicated
the presence of three-center CuBCipso interactions. For both
structures, the lowest unoccupied molecular orbital (LUMO)
corresponds to the antibonding combination of a d orbital at
Cu and a π(BCipso) orbital, whose bonding counterpart is
associated with a low-lying filled orbital, HOMO-20 for 7*
7*
DFT
2.296
2.293
2.434
2.459
2.261
8a
X-ray 2.266(2) 2.379(5) 2.414(4) 2.254(2)
2.274(2)
DFT
8a*
8bb
8b*
8c*
8d*
2.312
2.304
2.411
2.489
2.386
2.574
2.689
2.504
2.655
2.741
2.890
3.203
2.275
2.267
2.287
2.279
2.283
0
X-ray 2.250
2.264
DFT
DFT
DFT
2.284
2.286
2.292
2.290
2.270
2.271
þ3.0
-2.1
-3.0
a Bond lengths in A, bond angles in deg, ΔG298 in kcal/mol. b Average
value of the three very similar independent molecules present in the unit
cell.
and HOMO-12 for 8a* (Figure 6). To shed more light on the
bonding situation, Natural Bond Orbital (NBO) analyses
were carried out. At the second-order perturbation level,
several donor-acceptor interactions involving B, Cipso, and
Cu were found (Table 2). In particular, CufB donation
arises from both s and d orbitals. The corresponding delo-
calization energy (12-13 kcal/mol) falls in the same range
(30) Braunstein, P.; Herberich, G. E.; Neuschuetz, M.; Schmidt, M. U.;
Englert, U.; Lecante, P.; Mosset, A. Organometallics 1998, 17, 2177–2182.
(31) (a) Sircoglou, M.; Bouhadir, G.; Saffon, N.; Miqueu, K.; Bourissou,
D. Organometallics 2008, 27, 1675–1678. (b) Bontemps, S.; Bouhadir, G.;
Apperley, D. C.; Dyer, P. W.; Miqueu, K.; Bourissou, D. Chem. Asian J. 2009, 4,
428–435.

3988 Inorganic Chemistry, Vol. 49, No. 9, 2010
Sircoglou et al.
Table 2. Donor-Acceptor Interactions toward B and Cu Found by Second-Order Pertubative NBO Analysis of 7*;a Molekel Plotsb for the Corresponding (a) Donor NBO
and (b) Acceptor NBOc
a Delocalization energies in kcal/mol. b Cutoff: 0.05. c For 8a*, see Supporting Information, Table S3.15
Table 3. Atomic Charges, As Derived from Natural Population Analyses (NPA),
potential energy surface to evaluate how flexible is the
Computed for Complex 7*, the Free Ligand 5*, and the Related Boron-Free
participation of the BPh fragment. In addition to 8a*, three
energy minima differing essentially in the positioning of the
BPh moiety were located. Structure 8b*, related to 8b,
displayed dissymmetric η2-BC coordination. On going from
8a* to 8b*, the CuB distance slightly shortens (from 2.411 to
2.386 A), while the CuCipso distance increases by about 10%
(from 2.504 to 2.741 A). The two other minima, 8c* and 8d*,
correspond to further backward displacements of the BPh
fragment. The corresponding CuB distances are elongated by
7% in 8c* and 11.5% in 8d*, while the CuCipso distances
reach 2.890 A in 8c* and 3.202 A in 8d* (corresponding to
elongations of 15.5% and 28%, relative to 8a*). Structures
8c* and 8d* are thus better described as weak η1-B coordina-
tion rather than η2-BC coordination. This is consistent with
the presence of the four independent molecules within the
unit cell of 8 and further supports some flexible character for
the coordination of the BPh fragment to copper.
Complex [(Ph3P)2CuCl]a
c
q Cu
q Β
q Pb
q Cipso
q Cl
complex 7*
ligand 5*
(Ph3P)2CuCl
0.77
0.63
0.64
0.87
1.00
0.99
0.95
-0.45 (-0.26)
-0.42 (-0.26)
-0.76
-0.78
a For 8a*, 6* and [(iPr2PhP)2CuCl], see Supporting Information,
Table S4.15 b Mean value. c The value in parentheses is associated with
the BPh fragment.
than that computed for the η1-B complex of type A (7.9 kcal/
mol).7f But here, the boron is also stabilized by the adjacent π
system via a π(CipsoCortho)f2p(B) interaction, with a delo-
calization energy of 26-28 kcal/mol. In addition, a σ(BCipso
)
and a π(CipsoCortho) orbitals were found to engage into
donation toward Cu. The corresponding delocalization
energy amounts to 9-11 kcal/mol.
The atomic charges, as derived from natural population
analyses (Table 3), confirm the transfer of density from
copper to boron. It was estimated by (i) the difference ΔqB
between the charge at boron in the complexes and that in the
related free ligands and (ii) the difference ΔqCu between the
charge at the copper in the complexes and that in the related
boron-free copper complexes (R2PPh)2CuCl. The donor-
acceptor CufB interaction resulted in negative values of Δq
B (-0.22 for 7* and -0.25 for 8a*) and positive values of Δq
Cu (þ0.14 for 7* and þ0.15 for 8a*). These values are similar
in magnitude to those computed for the η1-B complex of type
A (Δq B = -0.24 and Δq Cu = þ0.07).7f
Conclusion
In summary, a series of copper(I) complexes derived from
mono- and diphosphino-boranes have been prepared and
fully characterized. Compared with the previously reported
TPB complex of type A, the presence of only two or even one
phosphino buttresses imparts higher flexibility and favors
thereby the participation of the aryl substituent at boron to
the coordination. Accordingly, complex 2 derived from the
monophosphino-borane ligand 1 adopts η3-BCC coordina-
tion, drawing some parallel with that reported earlier by
Emslie upon coordination of the PSB ligand to Rh, Ni, and
Pd. In addition, the related complexes 7 and 8 derived
from the diphosphino-borane ligands 5 and 6 adopt a unique
Lastly, the presence of structures 8a and 8b in the crystal-
lographic cell of complex 8 prompted us to scrutinize the

Article
Inorganic Chemistry, Vol. 49, No. 9, 2010 3989
η2-BC coordination mode that has been thoroughly investi-
gated computationally. These results substantiate further the
versatile coordination properties of arylborane fragments,
and illustrate the ability of arene rings to support MfB
interactions.
42.1 Hz, C12), 131.1 (s, C8), 131.0 (d, 2J(C,P) = 19.1 Hz,
C11), 130.2 (d, 4J(C,P) = 2.2 Hz, C9), 128.7 (s, C3,5), 127.8 (d,
3J(C,P) = 6.0 Hz, C10), 25.1 (s, CHiPr), 24.9 (s, CHiPr), 19.5 (d,
2J(C,P) = 2.9 Hz, CH3iPr), 18.9 (d, 2J(C,P) = 5.3 Hz, CH3iPr).
{[o-iPr2P(C6H4)BCy2]Cu(μ-Cl)}2 Complex 4. To a suspen-
sion of CuCl (67 mg, 0.68 mmol) in CH2Cl2 (5 mL) was added a
solution of (o-diisopropylphosphinophenyl)dicyclohexyl bor-
ane 3 (250 mg, 0.68 mmol) in CH2Cl2 (5 mL) at -50 °C. The
suspension was warmed to RT, and the solvent was removed
under vacuum. The residue was washed with 3 ꢀ 4 mL of
pentane. X-ray quality colorless crystals were grown from a
saturated dichloromethane solution at -40 °C (121 mg, 38%);
mp 124-126 °C. 31P{1H} NMR (202.5 MHz, CDCl3, 293 K):
δ = 26.8; 11B{1H} NMR (160.5 MHz, CDCl3, 293 K): δ = 82.5;
1H NMR (500.3 MHz, CDCl3, 293 K): δ = 7.43 (m, 2H, HAr),
Experimental Section
Materials and Methods. All reactions and manipulations were
carried out under an atmosphere of dry argon using standard
Schlenk techniques. Dry, oxygen-free solvents were employed.
Diethyl ether and toluene were dried over sodium, CH2Cl2 and
pentane were dried over CaH2 and distilled prior to use. 1H, 13C,
11B, and 31P NMR spectra were recorded on Bruker Avance 300,
400, and 500 spectrometers. Chemical shifts are expressed with a
positive sign, in parts per million, calibrated to residual 1H
(7.24 ppm) and 13C (77.16 ppm) solvent signals, external BF3.
OEt2 (0 ppm) and 85% H3PO4 (0 ppm), respectively. The N
values corresponding to 1/2 [J(AX)þJ(A0X)] are provided for
the second-order AA0X systems observed in 13C NMR.32 For
the atom numbering used in the NMR assignment, see the
Supporting Information. Mass spectra were recorded on a
Waters LCT spectrometer. Diphenylchloroborane,33 o-iPr2P-
(C6H4)Br,34 3,7b 5,7c and 67a were synthesized as previously
described.
3
3
7.30 (t, 1H, J(H,H) = 8.1 Hz, HAr), 6.98 (d, 1H, J(H,H) =
8.1 Hz, HAr), 2.38 (sept-d, 2H, J(H,H) = 7.1 Hz, J(H,P) =
3
2
3
9.5 Hz, CHiPr), 2.18 (d, 2H, J(H,H) = 12.3 Hz, HCy), 1.97
(pseudo-t, 2H, 3J(H,H) = 12.1 Hz, HCy), 1.85 (d, 2H, 3J(H,H) =
13.0 Hz, HCy), 1.80 (d, 2H, 3J(H,H) = 12.8 Hz, HCy), 1.68 (d, 2H,
3J(H,H) = 12.6 Hz, HCy), 1.63 (d, 2H, 3J(H,H) = 12.8 Hz, HCy),
1.37 (m, 2H, HCy), 1.31 (dd, 6H, 3J(H,H) = 7.1 Hz, 3J(H,P) =
3
17.1 Hz, CH3iPr), 1.23 (m, 6H, HCy), 1.14 (dd, 6H, J(H,H) =
7.1 Hz, 3J(H,P) = 15.8 Hz, CH3iPr), 1.00 (m, 2H, HCy); 13C NMR
(125.8 MHz, CDCl3, 293 K): δ = 157.5 (d, 2J(C,P) = 29.9 Hz,
C1), 131.1 (d, J(C,P) = 1.4 Hz, CAr), 129.3 (d, J(C,P) = 2.2 Hz,
CAr), 126.8 (d, 1J(C,P) = 40.5 Hz, C2), 126.6 (d, J(C,P) =
18.1 Hz, CAr), 126.0 (d, J(C,P) = 6.3 Hz, CAr), 39.5 (s, CHCy),
30.3 (s, CCy), 28.0 (s, CCy), 27.9 (s, CCy), 27.5 (s, CCy), 26.8
(s, CCy), 25.9 (d, 1J(C,P) = 24.9 Hz, CHiPr), 20.0 (d, 2J(C,P) =
6.3 Hz, CH3iPr), 19.9 (d, 2J(C,P) = 2.8 Hz, CH3iPr).
o-iPr2P(C6H4)BPh2 Ligand 1. To a solution of o-iPr2-
(C6H4)Br (188 mg, 6.88 mmol) in ether (1 mL) was added a
solution of n-BuLi (1.6 M in hexanes, 0.43 mL, 6.88 mmol) at
-40 °C. Following the apparition of a white precipitate, the
suspension was further stirred for 20 min at the same tempera-
ture. The supernatant was then removed by filtration. The
residue was dissolved in toluene (1.5 mL), and a solution of
diphenylchloroborane (125 mg, 6.25 mmol) in toluene (1 mL)
was added slowly at -78 °C. After warming to RT, the lithium
chloride salts were removed by filtration. Ligand 1 (209 mg,
94%) was obtained as a white solid by evaporation of the sol-
vent. X-ray quality crystals were grown from a saturated CH2-
Cl2/pentane solution at -30 °C. 31P{1H} NMR (202.5 MHz,
CDCl3, 298 K): δ = 24.8 ; 11B{1H} NMR (160.5 MHz, CDCl3,
298 K): δ = 5.0 ; 1H NMR (400.1 MHz, CDCl3, 298 K): δ =
7.41 (m, 4H, H2,6), 7.38 (m, 2H, Harom), 7.30 (m, 2H, Harom),
7.23 (m, 4H, H3,5), 7.14 (m, 2H, H4), 2.67 (m, 2H, CHiPr), 1.31 (d,
6H, 3J(H,H) = 7.1 Hz, CH3iPr), 1.10 (d, 6H, 3J(H,H) = 7.3 Hz,
CH3iPr) ; HRMS (ESIþ) calcd for [MHþ,CH3CN] C26H32BNP:
400.2365, found: 400.2351.
{[o-Ph2P(C6H4)]2BPh}CuCl Complex 7. To a suspension of
CuCl (65 mg, 0.65 mmol) in CH2Cl2 (1 mL) was added a solution
of 5 (400 mg, 0.65 mmol) in CH2Cl2 (10 mL) at -78 °C. After
subsequent stirring for 15 min at -78 °C, the suspension was
warmed to RT. The suspension turned bright yellow. After
filtration, the solution was concentrated and addition of ether
(25 mL) allowed a yellow solid to precipitate. Evaporation of the
solvent from the residue afforded complex 7 as a bright yellow
powder (200 mg, 65%). X-ray quality crystals were grown from
a saturated dichloromethane solution at RT; mp 259 °C. 31P-
{1H} NMR (202.5 MHz, CDCl3, 298 K): δ = 3.44 ; 11B{1H}
1
NMR (160.5 MHz, CDCl3, 298 K): δ = 56 ; H NMR (500.3
MHz, CDCl3, 298 K): δ = 7.89 (d, 2H, 3J(H,H) = 7.7 Hz, H11),
7.83 (m, 4H, PPh2), 7.60 (t, 1H, 3J(H,H) = 7.5 Hz, H4), 7.57 (m,
2H, H9), 7.48 (m, 2H, H8), 7.43 (m, 10H, HAr), 7.21 (t, 2H, 3J(H,
H) = 7.5 Hz, H3,5), 7.10 (t, 2H, 3J(H,H) = 7.8 Hz, PPh2), 6.90 (t,
{[o-iPr2P(C6H4)BPh2]Cu(μ-Cl)}2 Complex 2. To a suspen-
sion of CuCl (57 mg, 0.58 mmol) in CH2Cl2 (3 mL) was added a
solution of 1 (209 mg, 0.58 mmol) in CH2Cl2 (6 mL) at -78 °C.
After subsequent stirring for 15 min at -78 °C, the suspension
was warmed to RT, and thus turned limpid pale yellow. Addi-
tion of 10 mL of ether allowed the apparition of a precipitate.
After elimination of the supernatant by filtration, the resulting
solid was dried under vacuum to afford 2 as a pale yellow
powder (225 mg, 85%). X-ray quality crystals were grown from
a saturated dichloromethane solution at RT; mp 138-140 °C.
11B{1H} NMR (128.2 MHz): δ = 53. Solution NMR: 31P{1H}
NMR (202.5 MHz, CDCl3, 298 K): δ = 28.3 ; 11B{1H} NMR
3
4H, J(H,H) = 7.8 Hz, PPh2), 6.80 (m, 4H, PPh2); 13C NMR
(125.8 MHz, CDCl3, 298 K): δ = 155.3 (AA0X, N = 22.5 Hz,
C7), 139.6 (s br, C2,6), 135.3 (AA0X, N = 19.8 Hz, C12), 134.8
(AA0X, N = 7,1 Hz, PPh2), 134.5 (s br, C4), 133.5 (s, C8), 133.4
(AA0X, N = 16.0 Hz, Cipso PPh2), 132.9 (AA0X, N = 20.1 Hz,
Cipso PPh2), 132.7 (m br, C1), 131.8 (AA0X, N = 6.2 Hz, PPh2),
130.4 (AA0X, N = 11.7 Hz, C11), 130.3 (s, PPh2), 130.2, (s, C9),
128.8 (s br, PPh2), 128.5 (AA0X, N = 5.1 Hz, PPh2), 128.3
(AA0X, N = 4.4 Hz, PPh2), 128.1 (AA0X, N = 2.7 Hz, C10),
128.0 (s, C3,5).
1
(160.5 MHz, CDCl3, 298 K): δ = 58 ; H NMR (500.3 MHz,
{[o-iPr2P(C6H4)]2BPh}CuCl Complex 8. To a suspension of
CuCl (42 mg, 0.42 mmol) in CH2Cl2 (1 mL) was added a solution
of ligand 6 (200 mg, 0.42 mmol) in CH2Cl2 (2 mL) at -78 °C.
After stirring for 15 min, the suspension was warmed to RT. The
suspension turned limpid bright yellow. Evaporation of the
solvent afforded complex 8 as a bright yellow solid (226 mg,
94%). X-ray quality crystals were grown from a satu-
rated dichloromethane/ether solution at RT; mp 200-201 °C.
31P{1H} NMR (202.5 MHz, CDCl3, 298 K): δ = 21.52 ; 11B{1H}
NMR (160.5 MHz, CDCl3, 298 K): δ = 55 ; 1H NMR
3
CDCl3, 298 K): δ = 7.88 (d br, 4H, J(H,H) = 7.5 Hz, H2,6),
7.60 (m, 3H, H9,4), 7.55 (m, 1H, H8), 7.53 (m, 1H, H11), 7.49 (m,
5H, H3,5,10), 2.25 (m, 2H, CHiPr), 1.04 (m, 12 H, CH3iPr) ;
13C NMR (125.8 MHz, CDCl3, 298 K): δ = 156.2 (m br, C7),
138.4 (s, C2,6), 137.2 (s br, C1), 133.1 (s, C4), 131.7 (d, 1J(C,P) =
(32) (a) Nuclear Magnetic Resonance Spectroscopy; Bovey F. A., Ed.;
Academic Press: New York, 1969. (b) Abraham, R. J.; Bernstein, H. J. Can. J.
Chem. 1961, 39, 216–230.
(33) Thomas, J. C.; Peters, J. C. Inorg. Chem. 2003, 42, 5055–5073.
3
(500.3 MHz, CDCl3, 298 K): δ = 7.57 (d br, 4H, J(H,H) =
€
(34) Tamm, M.; Dreβel, B.; Baum, K.; Lugger, T.; Pape, T. J. Organomet.
Chem. 2003, 677, 1–9.
8.0 Hz, H8,11), 7.46 (t br, 2H, 3J(H,H) = 8.0 Hz, H9), 7.43

3990 Inorganic Chemistry, Vol. 49, No. 9, 2010
Sircoglou et al.
(m, 1H, H4), 7.41 (t, 2H, 3J(H,H) = 8.0 Hz, H10), 7.30 (d, 2H,
3J(H,H) = 7.0 Hz, H2,6), 7.25 (m, 2H, H3,5), 2.59 (m, 2H, CHiPr),
2.35 (m, 2H, CHiPr), 1.44 (m, 6H, CH3iPr), 1.31(m, 6H, CH3iPr),
1.14 (m, 6H, CH3iPr), 1.02 (m, 6H, CH3iPr); 13C NMR (125.8
MHz, CDCl3, 298 K): δ = 157.0 (m br, C7), 140.3 (s br, C1),
136.8 (s, C2,6), 134.5 (AA0X, N = 16.6 Hz, C12), 132.2 (s, C4),
131.0 (AA0X, N = 10.9 Hz, C11), 130.6 (s, C8), 129.8 (s, C10),
127.8 (s, C3,5), 127.2 (AA0X, N = 2.5 Hz, C9), 25.3 (AA0X, N =
10.7 Hz, CHiPr), 24.7 (AA0X, N = 7.3 Hz, CHiPr), 19.6 (m,
CH3iPr), 19.4 (s, CH3iPr), 17.6 (s, CH3iPr) ; HRMS (ESIþ) calcd
for [M-Cl]þ C30H41BP2Cu: 537.2073, found: 537.2091.
XRD Studies. Data were collected using an oil-coated shock-
cooled crystal on Bruker-SMART APEX II (2), Bruker-
SMART APEX II (4, 7) and Bruker X8 Kappa APEXII
(8) diffractometers (λ = 0.71073 A) at 180 (2), 193 (4, 7), or
100 K (8). Semiempirical absorption corrections were emplo-
yed for 2, 4, and 8.35 The structures were solved by direct
methods (SHELXS-97),36 and refined using the least-squares
method on F2.37 Crystallographic data (excluding structure
factors) have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no.
CCDC-749019 (2), 749020 (4), 749021 (7) and 749022 (8).
These data can be obtained free of charge via www.ccdc.cam.
uk/conts/retrieving.html (or from the CCDC, 12 Union Road,
Cambridge CB2 1EZ, U.K.; fax: (þ44) 1223-336-033; or
deposit@ccdc.cam.ac.uk).
the DFT level of theory using the hybrid functional B3PW91.42,43
Geometry optimizations were carried out without any symmetry
restrictions, and the nature of the minima was verified with
analytical frequency calculations. All these computations have
been performed with the Gaussian 0344 suite of programs. The
electronic structure was studied using NBO analysis,45 sec-
ond-order perturbation theory being particularly adapted to
the description of metalfLewis acid interactions. Molecular
orbitals and NBOs were drawn with Molekel 4.3. 31P and 11B
NMR chemical shifts were evaluated by employing the direct
implementation of the GIAO method46 at the B3PW91/
SDDþpol(P),6-31G**(B,C,H)//B3PW91/6-31G**(P,B,C,H) le-
vel of theory, using as reference the corresponding PMe3 (δ31P =
-63.5 ppm) and BF3-Et2O (δ11B = 0 ppm) shielding constants
calculated at the same level of theory.
Acknowledgment. The Centre National de la Recherche
ꢀ
Scientifique (CNRS), Universite Paul Sabatier (UPS), and
Agence Nationale de la Recherche Scientifique (ANR-06-
BLAN-0034) are warmly acknowledged for financial support
of this work. We are also grateful to Dr. Antonio L. Llamas-Saiz
(Unidade de Raios X, Universidade de Santiago de Compostela,
Spain) for the XRD analysis of 8. L.M. thanks the Institut
Universitaire de France.
Supporting Information Available: Computational results
including the Cartesian coordinates for the optimized structures
(PDF); X-ray crystallographic data for complexes 2/4/7/8
(CIF). This material is available free of charge via the Internet
at http://pubs.acs.org.
Computational Methods. Copper, Phosphorus, and Chlorine
were treated with a Stuttgart-Dresden pseudopotential in combi-
nation with their adapted basis set.38,39 The basis set has been
augmented by a set of polarization function (d for P and Cl).40
Boron, Carbon and Hydrogen atoms have been described with a
6-31G(d,p) double-ζ basis set.41 Calculations were carried out at
(44) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Zakrzewski, V. G.; Montgomery, J. A.; Stratman,
R. E.; Burant, J. C.; Dapprich, S.; Millam, J. M.; Daniels, A. D.; Kudin, K.
N.; Strain, M. C.; Farkas, O.; Tomasi, J.; Barone, V.; Cossi, M.; Cammi, R.;
Mennucci, B.; Pomelli, C.; Adamo, C.; Clifford, S.; Ochterski, J.; Petersson,
G. A.; Ayala, P. Y.; Cui, Q.; Morokuma, K.; Malick, D. K.; Rabuck, A. D.;
Raghavachari, K.; Foresman, J. B.; Cioslowswi, J.; Ortiz, J. V.; Baboul, A.
G.; Stefanov, B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.;
Gomperts, R.; Martin, R.; Fox, D. J.; Keith, T.; AlLaham, M. A.; Peng, C.
Y.; Nanayakkara, A., Gonzalez, C.; Challacombe, M.; Gill, P. M. W.;
Jonhson, B.; Chen, W.; Wong, M. W. J.; Andres, L.; Head-Gordon, M.;
Replogle, E. S.; Pople, J. A. Gaussian 03, C.02 ed.; Gaussian, Inc.: Pittsburgh,
PA, 2006.
(35) SADABS, Program for data correction, version 2.10; Bruker-AXS:
Madison, WI, 2003.
(36) Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467–473.
(37) SHELXL-97, Program for Crystal Structure Refinement; Sheldrick,
€
€
G. M.; University of Gottingen: Gottingen, Germany, 1997.
(38) Dolg, M.; Weding, U.; Stoll, H.; Preuss, H. J. Chem. Phys. 1987, 86,
866–872.
(39) Bergner, A.; Dolg, M.; Kuechle, W.; Stoll, H.; Preuss, H. Mol. Phys.
1993, 80, 1431–1441.
€
€
(40) Ehlers, A. W.; Bohme, M.; Dapprich, S.; Gobbi, A.; Hollwarth, A.;
€
Jonas, V.; Kohler, K. F.; Stegmann, R.; Veldkamp, A.; Frenking, G. Chem.
Phys. Lett. 1993, 208, 111–114.
(45) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88, 899–
926.
(46) (a) London, F. J. Phys. Radium 1937, 8, 3974–3976. (b) Ditchfield, R.
Mol. Phys. 1974, 27, 789–807. (c) Wolinski, K.; Hilton, J. F.; Pulay, P. J. Am.
Chem. Soc. 1990, 112, 8251–8260.
(41) Hariharan, P. C.; Pople, J. A. Theor. Chim. Acta 1973, 28, 213–222.
(42) Becke, A. D. J. Chem. Phys. 1993, 98, 5648–5652.
(43) Burke, K.; Perdew, J. P.; Yang, W. Electronic Density Functional
Theory: Recent Progress and New Directions; Dobson, J. F., Vignale, G., Das,
M. P., Eds.; Plenum Press: New York, 1998.