Structural and spectroscopic comparisons of tris(2- (diphenylphosphino)ethyl)aminecopper(I) tetraphenylborate, [(NP3)Cu](BPh4), with gold(I) and silver(I) [(NP3)M]X (X = BPh4, NO3, PF6) complexes

Article abstract of DOI:10.1016/S0022-2860(98)00477-3

The ligand tris(2-(diphenylphosphino)ethyl)amine (NP₃) reacts with CuCl in CH₂Cl₂ to produce the monomeric complex [(NP₃)Cu](BPh₄), (1). Unlike the Au(I) and Ag(I) derivatives, this material is weakly 4-coordinate with a trigonal CuP₃ coordination and somewhat long Cu-N bonding to the tertiary N atom. Compound 1 crystallizes in the monoclinic space group P2₁/n (No. 14) with cell constants: a = 21.068(8) A, b = 18.546(2) A, c = 31.523(6) A, β = 107.02(2)°and Z = 8. Refinement of 12572 reflections and 1075 parameters yields R = 0.0927 and Rw = 0.1980. This structure completes the Cu, Ag, Au triad of NP₃ complexes. The 3-coordinate mononuclear and binuclear Au(I) NP₃ complexes, [(NP₃)Au]X (X = BPh₄, PF₆, NO₃) and [(NP₃)₂Au₂]X₂ (X = BPh₄, PF₆), all show a brilliant luminescence under UV radiation. This emission has been studied in detail and is attributed to a metal-centered P(z) → (d(x2-y2), d(xy)) transition. The Cu(I) complex is not luminescent in the visible spectral region.

Full text of DOI:10.1016/S0022-2860(98)00477-3

MOLSTR 10370
Journal of Molecular Structure 470 (1998) 151–160
Structural and spectroscopic comparisons of
tris(2-(diphenylphosphino)ethyl)aminecopper(I) tetraphenylborate,
[(NP3)Cu](BPh4), with gold(I) and silver(I) [(NP3)M]X
(X = BPh4, NO3, PF6) complexes
John P. Fackler, Jr.1,*, Jennifer M. Forward, Tiffany Grant, Richard J. Staples
Department of Chemistry and Laboratory of Molecular Structure and Bonding, Texas A & M University, College Station, TX 77842-3012, USA
Received 25 November 1997; accepted 6 January 1998
Abstract
The ligand tris(2-(diphenylphosphino)ethyl)amine (NP3) reacts with CuCl in CH2Cl2 to produce the monomeric complex
[(NP3)Cu](BPh4), (1). Unlike the Au(I) and Ag(I) derivatives, this material is weakly 4-coordinate with a trigonal CuP3
coordination and somewhat long Cu–N bonding to the tertiary N atom. Compound 1 crystallizes in the monoclinic space
˚
˚
˚
group P21/n (No. 14) with cell constants: a = 21.068(8) A, b = 18.546(2) A, c = 31.523(6) A, b = 107.02(2)Њ and Z = 8.
Refinement of 12572 reflections and 1075 parameters yields R = 0.0927 and Rw = 0.1980. This structure completes the Cu, Ag,
Au triad of NP3 complexes. The 3-coordinate mononuclear and binuclear Au(I) NP3 complexes, [(NP3)Au]X (X = BPh4, PF6,
NO3) and [(NP3)2Au2]X2 (X = BPh4, PF6), all show a brilliant luminescence under UV radiation. This emission has been
x2 − y2
studied in detail and is attributed to a metal-centered pz → (d
, dxy) transition. The Cu(I) complex is not luminescent in the
visible spectral region. ᭧ 1998 Elsevier Science B.V. All rights reserved.
Keywords: tris(2-(diphenylphosphino)ethyl)amine; monomeric complex; luminescence
1. Introduction
umbrella-like fashion. However, two arrangements
are found. The most common arrangement is a tri-
gonal pyramidal geometry with one axial M–N and
three equatorial M–P bonds, I. For many of the d8
metal complexes found with this geometry, an addi-
tional axial ligand is coordinated to the metal center to
satisfy the 16–18 electron rule, for example,
[(NP3)Co(CS)]+ [2], [(NP3)Ni(Cl)]+ [3], and
[(NP3)Pd(CH3)]+ [4]. In some complexes [5], the
M–N distance can be elongated with the metal mov-
ing out of the plane of the three phosphorus atoms,
away from the nitrogen, giving a trigonally elongated
geometry, II. The arrangement adopted depends on
The potentially tetra dentate ligand tris(2-
(diphenylphosphino)ethyl)amine (NP3), which can
coordinate to metal atoms using all four of its Group
15 atoms, has been shown to coordinate to a range of
transition metal ions [1]. In mononuclear complexes
the ligand generally wraps around the metal in an
* Corresponding author. Tel: 001 409 845 2835; Fax: 001 409 845
2373; e-mail: fackler@chemvx.tamu.edu
1 Dedicated to a friend and colleague, Abraham Clearfield, on the
occasion of his 70th birthday.
0022-2860/98/$ - see front matter ᭧ 1998 Elsevier Science B.V. All rights reserved.
PII S0022-2860(98)00477-3

152
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
the electronic properties of the metal and the nature of
the axial ligand.
strong interaction between the metal and the ligand
nitrogen atom. However, the [(NP3)AgONO2] com-
plex shows a significantly longer Ag…N coordina-
˚
tion, 2.924(4) A, than found in the [(NP3)Ag]PF6
˚
complex, 2.662(3) A. The axial coordination of the
…
˚
nitrate, although weak, Ag O, 2.55(1) A, presum-
…
ably is the cause for this difference in the Ag
N
coordination. Also it is to be noted that the Ag–P
distances are significantly longer, 2.477(3)–
˚
2.524(3) A, than the Au–P distances, 2.361(2)–
˚
2.369(2) A, for the isomorphous [(NP3)Au]NO3 com-
Several complexes containing d10 metals and the
NP3 ligand have been structurally characterized and
examples of both the trigonal pyramidal geometry and
a trigonally elongated geometry have been observed.
The (NP3)Ni(0) complex adopts the trigonal pyrami-
dal geometry where there is no coligand coordinated
to the nickel center [6,7]. The N–Ni–P angles are very
close to 90Њ with the nickel atom situated in the plane
of the three phosphorus atoms. The Ni–N distance is
plex. This observation of shorter M–P distances for
Au(I) compared with Ag(I) is consistent with the
smaller covalent radius of Au(I) compared with
Ag(I) [9]. The gold(I) complexes of the NP3 ligand
show a luminescence in the solid state at room tem-
perature. Several examples of three-coordinate,
gold(I) complexes that show emission have been
reported [10–12], including phosphine complexes
soluble in water [13].
Since the emission [14] from three coordinate
gold(I) and platinum(0) phosphine [15,16]2 com-
plexes is apparently associated with a transition
which is orbitally and spin forbidden in trigonal coor-
dinated d10 complexes (wherein the excitation energy
is in the near UV), it seemed appropriate to ask if
Cu(I) complexes of this NP3 ligand would (i) have a
trigonal planar CuP3 coordination and (ii) also be
˚
2.178(7) A which is relatively long but is within the
˚
usually observed Ni–N distances (2.06–2.18 A) and
is indicative of weak M–N bonding. The pyramidal
coordination of the nitrogen, with its apex directed
toward the Ni atom, suggests that the nitrogen elec-
tron lone pair can interact with the d2z and pz orbitals
of the metal. It is the mixing of the pz orbital with the
d2z orbital that produces a rehybridized orbital, with
the two electrons in it, which is in the trans axial
position. As the difference in energy between the d-
orbital and empty p-atomic orbitals increases, for
example on going from nickel to palladium, the extent
of this d–p mixing decreases. This has the effect of
increasing the repulsion between the NP3 nitrogen
atom and the metal center elongating the M–N
bond. Such is the case for the palladium analog,
(NP3)Pd(0), which has no co-ligand in the axial posi-
1
luminescent. The energy separation between the S0
and the 1D level in the Cu(I) ion is 26264 cm−1, com-
parable with the 29620 cm−1 separation [17] in the
gaseous Au(I) ion [18], and much smaller than the
46046 cm−1 separation for Ag(I). No luminescence
is observed for the [(NP3)Ag]X complexes [9]. This
paper reports the results of our observations on
[(NP3)Cu]PF6.
˚
tion [5]. The Pd–N bond is 2.69(2) A and the structure
of the complex shows the trigonally elongated geome-
try with the palladium lying out of the plane of the
phosphorus atoms by 0.42 A away from the nitrogen
2. Experimental
˚
The reactions were carried out under an atmosphere
of dry nitrogen using standard Schlenk line techni-
ques. The complexes [(NP3)2Au2]X2 (X = BPh4,
center.
For the Cu, Ag, Au triad, the X-ray structures for
the Ag(I) and Au(I) d10 NP3 [(NP3)M]X (M = Au, Ag;
X = PF6, NO3, BPh4) complexes have been described
[8]. Each of these complexes show a trigonally elon-
gated geometry where the coordination of the metal
center is approximately trigonal planar and there is no
2 Unfortunately the authors do not comment on luminescence as
they describe the structure for the first homoleptic complex of Pt(0)
formed with secondary phosphines which is rigorously trigonal in
its PtP3 geometry.

153
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
PF6) and [(NP3)Au]X (X = BPh4, NO3, PF6) and
[(NP3)Ag](PF6) were all synthesized using a pre-
viously published procedure [9]. The purity was
checked by 31P{1H} NMR and the unit cell dimen-
sions were compared with previously reported data.
The ligand, NP3, was prepared according to the litera-
ture [19]. 31P{1H} NMR spectra were recorded on a
Varian XL-400 spectrometer. Emission and excitation
spectra were measured on an SLM/AMINCO 8100
spectrofluorometer, using a Xe lamp. The data were
corrected for instrumental response. Lifetime
measurements were made using about 0.8 ns exci-
tation pulses from the 355 nm third harmonic of a
Quantal YG481 Nd–YAG laser.
MM2 calculations were performed using a CAChe
molecular modeling system [20,21]. The initial struc-
tures were obtained from the crystal structure of the
[(NP3)Au]+ ion, followed by substitution of either Ag
or Cu for the Au atom. The opposite configuration at
the nitrogen center was minimized by initially substi-
tuting a hydrogen for the electron pair and then final
minimization with the electron pair.
Synthesis of [(NP3)Cu](BPh4) (1). NP3 (0.05 g,
7.66 × 10−5 mol) was added to a solution of Cu(I)Cl
(0.0076 g, 7.66 × 10−5 mol) in CH3CN/CH2Cl2
(5 mL/5 mL). The reaction was stirred for 30 min
and then one equivalent of NaBPh4 was added
(0.026 g, 7.66 × 10−5 mol). After stirring the reaction
for an additional 30 min the solvent was removed
under reduced pressure to reveal a white solid. This
solid was extracted with CH2Cl2 (3 × 5 mL) and then
diethyl ether was added to precipitate a white crystal-
line solid (yield = 67%). Single crystals were grown
from the layering of a CH2Cl2 solution of the product
with benzene and hexane.
Initial crystal evaluation and data collection was
performed on an Enraf–Nonius FAST area detector
system using the program MADNES [23] in conjunc-
tion with a 4-circle k-axis goniometer equipped with
graphite monochromated Mo radiation (lKa
=
˚
0.71073 A). The crystal was optically centered in
the X-ray beam. Since the low temperature stream is
co-linear with the phi axis when x is 0, a x angle of 45Њ
was used in order to position the goniometer head out
of the cold stream, thereby avoiding complications
resulting from differential, time-dependent cooling
of the goniometer head. Initial crystal evaluation typi-
cally consists of a 30 to 60Њ rotation about q, with an
exposure time of 30–60 s. The image obtained upon
exposure was similar to that observed for a standard
rotational photograph and revealed that the crystal
was suitable for further investigation.
Reflections used for the unit cell determination
were obtained by scanning images measured at inter-
vals of 0.2Њ in a 10Њ range about q. The exposure time
was 10 s per image. Upon completion of the scans, q
was rotated 10Њ and another 10Њ scan was made at
intervals of 0.2Њ. A total of six 10Њ regions were
scanned in the range 0 Ͻ q Ͻ 100Њ. To enhance spec-
tral resolution, the crystal–detector distance had been
moved to 60 cm and the detector swing angle (v) was
set to 0. A total of 250 reflections were obtained. Fifty
of these reflections were used by the auto-indexing
routine, ENDEX, found in the MADNES software,
resulting in a preliminary primitive monoclinic unit
cell. Refined cell dimensions (Table 1) were obtained
by least-squares fitting of 250 reflections in the range
10 Ͻ 2v Ͻ 24Њ. Cell dimensions and Laue symmetry
were confirmed by axial images measured using a 30Њ
rotation about q, with an exposure time of 30 s. Data
collection was performed by measuring a series of
images at intervals of 0.3Њ about q. The detector
was set at a distance of 60 mm and a swing angle of
20Њ. Images were collected by scanning through four
separate regions of space. One sweep of 110Њ about q
was made with k = 33Њ (x = 25Њ). F was then rotated
90Њ and a second 110Њ sweep was made. Finally, two
75Њ sweeps of q were made with k = −170Њ (x = 98Њ);
the second sweep was made with F rotated 90Њ from
the first. This collection procedure allows for slightly
more than a hemisphere of data to be collected. Based
on the relative diffraction intensity, an exposure time
of 20 s was selected. Exposure times may be varied
3. X-ray data collection and refinement of the
structure
Crystallographic data were collected using an Enraf–
Nonius FAST area detector system. Specific procedures
used were adapted in part from those described by
Scheidt and Turowska-Tyrk [22]. A colorless crystal
of dimensions 0.4 × 0.4 × 0.5 mm was selected and
mounted on a quartz fiber with silicone grease. The
crystal was cooled to −60(2)ЊC using an Enraf–Nonius
low temperature controller, model FR558-S.

154
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
reflections (Rmerge = 7.64%) yielded 12572 unique
reflections of which 9565 were considered observed
with I Ͼ 2j(I). No absorption correction was
applied. The position of the metal atom was
located using the direct methods program,
SHELXS-86. The remaining non-hydrogen atoms
were located in an alternating series of least-
squares cycles and difference Fourier maps. One
CH2Cl2 was found to be disordered near the inver-
sion center. All non-hydrogen atoms were modelled
anisotropically and the hydrogens placed in idea-
lized positions for all atoms except for the disor-
dered solvent. Final least squares refinement of
1075 parameters resulted in residuals R (based on
F) and Rw (based on F2 for all data)3 of 0.0927 and
0.24, respectively. The quality-of-fit was 1.15 based
on F2 for all data. A final difference Fourier revealed
Table 1
Crystallographic data for [(NP3)Cu]BPh4), (1)
[(NP3)Cu](BPh4)(1)
Chemical formula
Molecular weight
Crystal size (mm)
Crystal system
Space group
C67.5H64BCl2.5CuN3P
1145.1
0.4 × O.4 × O.5
Monoclinic
P21/n (No. 14)
21.068(8)
18.546(2)
31.523(6)
107.02(2)
11777(5)
˚
a (A)
˚
b (A)
˚
c (A)
b, deg
3
˚
V (A )
Z
8
m (mm−1
)
0.608
1.292
298
Dc (g cm−3
Temp. (K)
)
˚
Radiation (l, A)
Graphite-monochromated Mo Ka
(0.71073)
0.0927, 0.1980
R,a Rwb
that the highest remaining peak of electron density
−1
˚
was 0.98 e A [3].
aR = ∑kFol-lFck/∑lFol.
bRw = {l∑w(lFol-lFcl)]/∑wlFol]}.
4. Structural results
between 3 and 40 s, depending on the intensity of the
diffraction pattern. Throughout the data collection,
the actual positions of reflections were compared
with those predicted based on the orientation matrix.
Reflections that occur outside the predicted ‘shoebox’
region were flagged. Raw data images that were
obtained were immediately evaluated using an off-
line version of MADNES. The method used for eva-
luation involved the use of a best fit ellipsoid that
gives the lowest j(I)/I to determine the boundaries
for strong reflections. The shapes and boundaries of
weak reflections are then based on those of strong
reflections in the same area of the detector [24–26].
The data were corrected for Lorentz and polarization
effects by the MADNES program. Reflection profiles
were fitted and values of F2 and and j(F2) for each
reflection were obtained by the program PROCOR,
which uses a fitting algorithm developed by Kabsch
[27,28]. Intensity data were examined for systematic
absences by an in-house program that provides a con-
cise listing of reflection classes to facilitate space
group assignment. The reflection data file was also
The structure of [(NP3)Cu](BPh4), 1, is shown in
Fig. 1. Details of the crystal structure determination
are given in Table 1. The atomic coordinates for
[(NP3)Cu](BPh4) are given in Table 2 and selected
bond distances and angles are given in Table 3. The
complex crystallizes in the monoclinic space group
P21/n with two well-separated cations and two anions
in the asymmetric unit. The bond distances and angles
within each of the two related molecules are similar.
There is little to remark on the molecular structure
of [(NP3)Cu](BPh4), except to note that the apical N
atom clearly coordinates to the copper(I). This does
not happen with Au(I) and with Ag(I) the interaction
˚
is also very weak, with an Ag–N distance of 2.662 A
in the [(NP3)Ag]PF6, for example. The Cu–N
˚
distances in the Cu(I) complex are 2.275(7) A and
˚
2.301(7) A for the two different molecules observed
crystallographically. The coordination around the
nitrogen center shows that the nitrogen lies closer
to the copper than its neighboring carbon atoms.
reformatted by the program for use with
a
SHELXL-93 structure refinement software package
[29].
A total of 31350 data were obtained in the range
3.0 Ͻ 2v Ͻ 44.84Њ. Averaging of equivalent
3 R factors based on F2 are statistically about twice as large as
those based on F and an R-index based on all data is inevitably
larger than one based only on data with F greater than a given
threshold.

155
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
Fig. 1. Molecular structure of the cation [(NP3)Cu]+ of 1.
The C–N–C bond angles are in the range 110.2Њ–
111.6Њ, indicating that the geometry of the nitrogen
is approximately tetrahedral with the lone pair orbital
facing towards the metal center.
The coordination of the copper center with the three
phosphorus atoms is essentially trigonal planar
with the P–Au–P angles in the range 116Њ–122Њ.
The Cu–P bond lengths are all similar (2.24–
2.27 A) and approximately form an equilateral
triangle around the gold(I) center. The copper atom
˚
˚
˚
lies slightly out of this plane by 0.144 A and 0.159 A
for the two different molecules, in a direction away
from the nitrogen. The observed Cu–P distances are
˚
about 0.2 A shorter than those found with the Ag(I)
Fig. 2. Excitation and emission spectra for [(NP3)Au](PF6).

156
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
Table 2
Table 2 continued
Atomic coordinates (×104) and equivalent isotropic displacement
parameters (A × 103) for [(NP3)Cu](BPh4),(1)
2
˚
x
y
z
U(eq)
C(43)
C(44)
C(45)
C(46)
C(47)
C(48)
C(49)
C(50)
C(51)
C(52)
C(53)
C(54)
C(55)
C(56)
C(57)
C(58)
C(59)
C(60)
C(61)
C(62)
C(63)
C(64)
C(65)
C(66)
C(67)
C(68)
C(69)
C(70)
C(71)
C(72)
C(73)
C(74)
C(75)
C(76)
C(77)
C(78)
C(79)
C(80)
C(81)
C(82)
C(83)
C(84)
B(1)
876(4)
747(5)
355(6)
77(6)
195(6)
5696(5)
6091(6)
5817(8)
5144(8)
4761(8)
5025(6)
5618(5)
4972(6)
4648(7)
4958(8)
5590(8)
5918(7)
7020(5)
6623(6)
6101(6)
5994(7)
6389(7)
6903(6)
8524(5)
8773(7)
9439(8)
9862(8)
9620(10)
8955(8)
8846(5)
9255(6)
9989(7)
10295(7)
9882(7)
9164(7)
7882(5)
7698(6)
7634(8)
7744(7)
7951(6)
8016(5)
5703(6)
6095(5)
7697(6)
7008(6)
7415(6)
7287(5)
2980(6)
3050(6)
3677(5)
4204(5)
4769(6)
4836(6)
4339(6)
3764(5)
2328(5)
1751(6)
1175(7)
1997(3)
2333(4)
2576(4)
2483(4)
2149(5)
1906(4)
1995(3)
1842(4)
2066(4)
2446(5)
2606(4)
2382(4)
1075(3)
1444(4)
1387(5)
974(5)
38(2)
57(3)
69(4)
67(4)
83(4)
67(3)
41(3)
57(3)
70(4)
82(4)
79(4)
66(3)
40(2)
54(3)
62(3)
63(3)
61(3)
54(3)
44(3)
80(4)
91(5)
94(5)
104(5)
79(4)
40(2)
54(3)
68(3)
67(4)
69(4)
58(3)
42(3)
55(3)
77(4)
63(3)
54(3)
40(2)
45(3)
43(3)
47(3)
47(3)
45(3)
44(3)
40(3)
35(3)
34(2)
39(2)
46(3)
49(3)
53(3)
42(2)
38(2)
58(3)
67(3)
x
y
z
U(eq)
Cu(1)
Cu(2)
P(1)
P(2)
P(3)
P(4)
P(5)
P(6)
N(1)
N(2)
C(1)
C(2)
C(3)
C(4)
C(5)
C(6)
C(7)
6406(1)
1368(1)
5570(1)
6491(1)
7043(1)
1443(1)
2069(1)
479(1)
6995(1)
7258(1)
7691(1)
5823(1)
7343(1)
6080(1)
7646(2)
7908(1)
6594(4)
6879(4)
8636(5)
8945(6)
9631(6)
10018(6)
9722(7)
9028(6)
7701(5)
7541(6)
7517(7)
7665(6)
7843(6)
7854(5)
5549(5)
6011(6)
5838(7)
5198(7)
4735(8)
4908(7)
5284(5)
5271(6)
4887(7)
4509(6)
4525(6)
4919(6)
6739(5)
6482(6)
6034(7)
5826(7)
6089(7)
6539(7)
8227(5)
8676(6)
9351(7)
9576(8)
9137(8)
8465(6)
7224(5)
7050(5)
5406(5)
5827(5)
7332(5)
6650(5)
1628(1)
1517(1)
1715(1)
1846(1)
1206(1)
1716(1)
1148(1)
1553(1)
990(2)
31(1)
35(1)
34(1)
34(1)
35(1)
36(1)
39(1)
37(1)
32(2)
39(2)
42(3)
46(3)
56(3)
62(3)
65(3)
49(3)
38(2)
56(3)
66(3)
63(3)
57(3)
44(3)
36(2)
59(3)
74(4)
62(3)
86(5)
73(4)
43(3)
64(3)
77(4)
75(4)
72(4)
60(3)
38(2)
55(3)
71(4)
71(4)
72(4)
60(3)
44(3)
58(3)
82(4)
79(4)
84(4)
60(3)
44(3)
40(3)
42(3)
33(2)
41(2)
40(2)
587(6)
2217(5)
2413(5)
2997(6)
3390(6)
3216(6)
2625(5)
2701(4)
3064(5)
3520(5)
3593(6)
3263(6)
2814(5)
2486(5)
2694(6)
2989(7)
3076(7)
2883(8)
2581(7)
355(5)
5671(3)
711(3)
935(2)
5451(5)
5889(5)
5784(5)
5244(6)
4806(6)
4894(5)
5345(5)
4714(5)
4584(6)
5078(7)
5704(6)
5841(5)
5984(5)
5945(6)
5582(7)
5239(5)
5290(7)
5665(6)
7236(5)
7510(6)
8087(6)
8394(6)
8124(6)
7556(5)
7704(5)
8134(5)
8660(6)
8736(6)
8305(6)
7793(6)
7428(5)
7384(6)
7679(8)
8025(7)
8096(6)
7790(5)
4877(4)
5077(4)
6114(5)
5500(4)
6402(5)
5983(5)
1516(3)
1319(3)
1147(4)
1176(4)
1368(4)
1532(3)
2237(3)
2258(4)
2666(4)
3040(4)
3026(4)
2623(3)
2199(3)
2531(4)
2819(4)
2767(4)
2451(4)
2166(4)
2069(3)
2527(4)
2719(4)
2460(5)
2006(5)
1814(4)
1151(3)
1543(4)
1518(5)
1120(6)
738(5)
626(4)
666(4)
1257(4)
1681(4)
1791(5)
1461(7)
1039(7)
925(4)
1373(3)
1399(3)
1280(4)
1137(4)
1104(4)
1223(4)
2047(3)
2040(4)
2431(5)
2833(4)
2844(3)
2459(3)
1159(3)
871(3)
597(3)
500(3)
1129(3)
728(3)
778(4)
779(4)
603(3)
320(3)
147(3)
C(8)
C(9)
C(10)
C(11)
C(12)
C(13)
C(14)
C(15)
C(16)
C(17)
C(18)
C(19)
C(20)
C(21)
C(22)
C(23)
C(24)
C(25)
C(26)
C(27)
C(28)
C(29)
C(30)
C(31)
C(32)
C(33)
C(34)
C(35)
C(36)
C(37)
C(38)
C(39)
C(40)
C(41)
C(42)
912(6)
838(7)
221(8)
−337(7)
−271(6)
195(5)
−435(5)
−598(6)
−139(6)
494(6)
661(5)
1187(5)
585(5)
1477(5)
1074(5)
−161(4)
82(4)
749(4)
1247(3)
901(4)
5789(5)
1168(5)
6145(4)
5780(5)
6060(5)
6734(5)
7124(5)
6832(5)
5698(4)
5263(5)
5205(6)
B(2)
956(5)
C(101)
C(102)
C(103)
C(104)
C(105)
C(106)
C(107)
C(108)
C(109)
1362(6)
1723(5)
1672(4)
1314(3)
903(3)
1308(3)
1051(3)
662(3)
269(3)
540(3)
707(3)
407(3)
384(4)
88(4)
626(3)

157
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
˚
NP3 complexes, and about 0.1 A shorter than those
found in the Au(I) complexes.
Table 2 continued
x
y
z
U(eq)
MM2 calculations performed on the CAChe mole-
cular modeling system showed that the nitrogen lone
pair of electrons bonding to the Cu(I) is energetically
more favorable by more than 100 kcal mol−1 when
directed towards the P3 plane, than when the lone
pair is directed away from the P3 plane. These calcu-
lations also place the metal atom out of the P3 plane
away from the nitrogen atom.
C(110)
C(111)
C(112)
C(113)
C(114)
C(115)
C(116)
C(117)
C(118)
C(119)
C(120)
C(121)
C(122)
C(123)
C(124)
C(125)
C(126)
C(127)
C(128)
C(129)
C(130)
C(131)
C(132)
C(133)
C(134)
C(135)
C(136)
C(137)
C(138)
5588(6)
6016(5)
6068(5)
6237(4)
6637(5)
7008(5)
6988(5)
6591(6)
6225(5)
5061(4)
5045(5)
4467(5)
3873(5)
3862(5)
4440(4)
1360(4)
1407(5)
1569(5)
1660(6)
1636(5)
1480(5)
1326(4)
845(4)
1163(7)
1711(6)
2293(5)
2705(5)
3157(6)
2918(6)
2225(6)
1757(7)
1986(6)
3269(5)
3716(5)
4030(6)
3898(6)
3449(6)
3137(5)
2384(5)
1664(6)
1088(7)
1187(7)
1869(6)
2460(6)
3836(5)
4205(5)
4830(5)
5116(5)
4769(6)
4136(5)
3017(5)
2395(5)
2965(6)
3599(6)
3616(5)
2994(5)
3252(5)
3208(6)
2871(6)
2621(6)
2687(6)
2369(6)
6168(2)
11646(2)
11029(2)
6683(3)
11651(8)
6470(10)
10600(4)
9491
−188(4)
−191(4)
107(3)
1265(3)
1590(3)
2006(4)
2116(4)
1831(4)
1404(3)
823(3)
1174(3)
1210(4)
893(3)
549(4)
514(3)
497(3)
664(4)
434(4)
31(4)
69(3)
55(3)
42(2)
37(2)
47(3)
53(3)
59(3)
67(3)
51(3)
35(2)
42(2)
56(3)
53(3)
52(3)
44(3)
38(2)
52(3)
63(3)
68(3)
61(3)
45(3)
31(2)
37(2)
36(2)
41(2)
46(3)
39(2)
34(2)
40(2)
55(3)
51(3)
41(2)
36(2)
43(3)
55(3)
53(3)
54(3)
50(3)
50(3)
106(1)
97(1)
103(1)
112(1)
84(4)
103(5)
92
5. Spectroscopic results
These luminescence spectra have been investigated
in more detail and the emissions obtained are summar-
ized in Table 4, where it can be seen that only the
Au(I) derivatives emit in the visible region. Fig. 2
shows the excitation and emission spectra measured
for [(NP3)Au](PF6) in the solid state at 298 K. The
lifetimes for the Au(I) NP3 complexes vary from 1–
9 ms. The reason for the observation of two different
components to the lifetimes is not fully understood but
it may be related to the presence of the low energy p
and p* orbitals associated with the phenyl rings of the
NP3 ligand. The 3-coordinate Au(I) phosphine com-
plex studied by McCleskey and Gray [10] and
McCleskey et al. [30] [(dcpe)3Au2]+ (dcpe = 1,2-
(dicyclohexylphosphino)ethane), contains two well-
separated gold(I) centers, coordinated to three phos-
phorus atoms in a trigonal planar geometry. It shows
emission in both the solid state (501 nm) and in acet-
onitrile solution (508 nm), with a lifetime for the
excited state in solution of 21.1 ms.
−143(4)
88(3)
561(3)
228(3)
35(3)
976(4)
1609(4)
2094(5)
1951(4)
368(4)
159(3)
483(3)
677(3)
751(3)
657(3)
744(3)
838(3)
851(3)
1298(3)
1649(3)
2092(4)
2185(4)
1858(3)
1414(3)
653(3)
4595(1)
1227(1)
354(1)
3700(2)
706(4)
4181(5)
−33(3)
65
−11(4)
C(140) −980(5)
C(141) −629(5)
C(142)
C(143)
C(144)
C(145)
C(146)
C(147)
C(148)
C(139) −674(5)
Cl(4)
Cl(3)
Cl(2)
39(4)
1627(4)
1427(5)
1817(5)
2420(5)
2654(5)
2255(5)
The Au(I) complexes of NP3 show no luminescence
in CH2Cl2 solution, as would be expected if the coor-
dination remained trigonal. In addition the 31P{1H}
NMR results in CH2Cl2 solution suggest that the
phosphorus atom coordination is fluxional on a time-
scale that is faster than 10−6 seconds. In our earlier
paper on NP3 complexes [9], we reported that the
monomeric gold(I) complex shows a singlet at
7270(2)
3869(2)
3541(2)
7001(2)
3317(6)
7601(7)
−749(4)
190
Cl(1)
C(202)
C(201)
Cl(5)
Cl(5B)
C(203)
130
50
26.12 ppm
and
the
binuclear
complex
52
10560
−54(3)
[(NP3)2Au2](BPh4)2 gives two singlets at 25.88 and
27.57 ppm, respectively, in a 2:1 ratio. These spectra
were carried out in a CD3CN/CH3CN solution. How-
ever, when the 31P{1H} NMR of the binuclear com-
plex was carried out in a CH2Cl2 solution a single
U(eq) is defined as 1/3 the trace of the orthoganlized Uij tensor.

158
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
Table 3
˚
Selected interatomic distances (A) and angles (Њ) for [(NP3)Cu](BPh4), (1)
Cu(1)–N(1)
Cu(2)–N(2)
Cu(1)–P(1)
Cu(1)–P(2)
Cu(1)–P(3)
Cu(2)–P(4)
Cu(2)–P(5)
Cu(2)–P(6)
N(1)–C(38)
N(1)–C(40)
N(1)–C(42)
N(2)–C(80)
N(2)–C(82)
N(2)–C(84)
2.275(7)
2.301(7)
2.264(3)
2.271(3)
2.243(3)
2.265(3)
2.250(3)
2.258(3)
1.469(11)
1.493(11)
1.482(11)
1.488(12)
1.491(12)
1.478(11)
0.144
P(1)–Cu(1)–P(2)
P(1)–Cu(1)–P(3)
P(2)–Cu(1)–P(3)
P(4)–Cu(2)–P(5)
P(4)–Cu(2)–P(6)
P(5)–Cu(2)–P(6)
P(1)–Cu(1)–N(1)
P(2)–Cu(1)–N(1)
P(3)–Cu(1)–N(1)
P(4)–Cu(2)–N(2)
P(5)–Cu(2)–N(2)
P(6)–Cu(2)–N(2)
C(38)–N(1)–C(40)
C(38)–N(1)–C(42)
C(40)–N(1)–C(42)
C(80)–N(2)–C(82)
C(80)–N(2)–C(84)
C(82)–N(2)–C(84)
120.26(10)
121.96(10)
116.56(10)
116.70(11)
119.49(10)
122.33(11)
86.6(2)
85.8(2)
86.5(2)
86.5(2)
85.4(2)
86.0(2)
110.4(7)
111.1(7)
110.2(7)
110.7(8)
110.4(7)
111.6(8)
…
Cu(1) P3 plane
…
Cu(2) P3 plane
0.159
peak at 32.49 ppm was obtained and the same peak
was found for [(NP3)2Au2](PF6)2 in CH2Cl2. Cooling
this solution does not significantly broaden this peak
indicating that the non-equivalent phosphorus atoms
are exchanging rapidly in solution. (Exchange may be
less rapid in acetonitrile.) Further evidence of this
rapid exchange comes from the fact that dissolving
the binuclear species in THF causes the complex to
be transformed into the mononuclear species. It is
well known that gold(I) complexes frequently prefer
linear two-coordination, both in the solid state and in
solution, and that the three-coordinate species are fre-
quently fluxional. For example, the [(Ph3P)3Au]+
complex is fluxional in solution, dissociating to
[(Ph3P)2Au]+ and the free ligand. Thus, this obser-
vation of this fluxional behavior in the 31P{1H}
NMR for the NP3 complexes is not surprising.
The impact of different solvents on the luminescence
of 3-coordinate Au(I) complexes depends on the ease
with which equilibria involving 2-coordinate and 3-
coordinate complexes are shifted by the solvent.
Acidic solvents like CH2Cl2 may solvate the non-
coordinating phosphine ligands formed upon Au–P
bond rupture, stabilizing 2-coordinate species in
these solvents while 3-coordinate species form in
THF or CH3CN. Related solvent effects have been
reported in water [13].
The Cu(I) complex reported in this paper does not
show any visible luminescence, even at 77 K, that can
be assigned to metal-centered transitions similar to the
ones observed for the 3-coordinate Au(I) complexes.
There is a weak emission for the [(NP3)Cu](BPh4)
complex at low temperatures, but this is assigned to
intraligand p,p* transitions, associated with the
phenyl rings of the anion [31].
Table 4
6. Discussion
Emission maxima and lifetimes of P3Au complexes in the solid state
at 298 K
The structures of the monomeric complexes,
[(NP3)M](PF6) (M = Au, Ag), both show a trigonally
elongated geometry with long M–N distances (Au–
N = 2.68 A, Ag–N = 2.66 A) and the metals lie out of
the plane of the phosphorus atoms, away from the
lmax (nm)
Solid state, 298 K
Lifetime (ms)
˚
˚
[NP3)Au](BPh4)
[NP3)Au](PF6)
[(NP3)Au]NO3)
465
494
529
1.9, 8.3
1.3, 6.3
0.4, 2.4
0.7, 7.9
1.3, 5.4
˚
˚
nitrogen (0.41 A for Au, 0.53 A for Ag). The Ag(I)
nitrate salt, [(NP3)Ag](NO3), also has a trigonally
elongated structure but the NO3− anion is weakly
[(NP3)2Au2](BPh4)2 470
[(NP3)2Au2](PF6)2 485

159
J.P. Fackler Jr. et al./Journal of Molecular Structure 470 (1998) 151–160
coordinated to the silver center in the axial position.
In solution, the 31P{1H} NMR results indicate that
the phosphorus groups are fluxional. The observation
of this fluxional behavior may explain the absence of
emission in solution, where the three-coordinate P3Au
unit does not exist in solution long enough for
emission from the triplet excited state to occur.
˚
The Ag–O distance is 2.55 A and the Ag atom lies
˚
0.745 A out of the plane of the phosphorus atoms. In
comparison with the Au and Ag complexes, the Cu
complex shows more of a trigonal pyramidal geome-
˚
try. The Cu lies only 0.15 A out of the P3 plane. In
addition, the Cu–N distances are significantly shorter,
The failure of the [(NP3)Cu]BPh4 complex to show
a visible luminescence, as found for the [(NP3)Au]+,
is probably attributable to the fact that the Cu(I) is not
3-coordinate, although this seemed like a reasonable
possibility from the Au(I) and Ag(I) work. The
luminescence found in 3-coordinate phosphine com-
plexes of Au(I) is quenched when the Au(I) becomes
4-coordinate. The fact that the NP3 ligand product is
four coordinates in Cu(I) and only three coordinate
with Au(I) and Ag(I) must be attributed to the smaller
size of Cu(I) and its increased tendency for full sp3
orbital hybridization, compared especially with Au(I),
where relativistic effects impact on the orbital mixing.
˚
˚
2.275(7) A and 2.301(7) A for the two molecules in
˚
the asymmetric unit compared with 2.683(6) A for
˚
Au–N and 2.662(3) A for Ag–N. However, these
Cu–N distances are long when compared with pre-
viously characterized nitrogen-containing Cu com-
plexes. The Cu–N bond distances are usually in the
˚
range 2.04–2.11 A. This copper–nitrogen interaction,
while apparently weak, appears to be stronger than the
M–N interactions in the Au(I) and Ag(I) analogs. The
M–N bond distance trend is Cu Ͼ AgϳAu.
Of the three monomeric complexes, [(NP3)M]+
(M = Au, Ag, Cu), only the gold complexes show a
strong luminescence at 77 K. In addition, the gold
binuclear species, [(NP3)2Au2](BPh4)2 also shows
strong emissions at low temperatures. In this latter
complex, two of the phosphorus atoms of each ligand
chelate to one gold atom while the third phosphorus
atom bridges to the other gold atom. Thus, each gold
is three-coordinate and approximately trigonal planar,
with no interaction between the gold and nitrogen
centers. The large Stokes’ shifts between the excita-
tion and emission energies, shown in Table 4, for the
gold complexes, imply that the emission is phos-
phorescence and the long lifetimes measured
(Ͼ2 ms) confirm this assignment. The values of the
emission maxima are all in the range 465–529 nm,
indicating that the origin of the emission is likely
to be the same for all the complexes measured.
This emission has been assigned as an essentially
…
With Ag(I), the data are not clear as to why the Ag
N
˚
distance is long, 2.662 A. Consequently the question
of the possible existence of visible luminescence in 3-
coordinate Cu(I) complexes with phosphine ligands
remains open.
Supplementary material available for complex 1,
including tables of crystallographic data, atomic coor-
dinates, thermal parameters and bond distances and
angles (18 pages) is available. Ordering information
is given on any current masthead page. Tables of
structure factors (76 pages) are available from John
P. Fackler, Jr upon request.
Acknowledgements
Luminescence lifetime measurements were
obtained at the Center for Fast Kinetics Research,
which is jointly supported by the Biotechnology
Branch of Research Sources of the NIH (Grant
RR00886) and by The University of Texas at Austin.
This work was supported by the National Science
Foundation (Grant CHE 9300107) and the Welch
Foundation.
metal-centered
triplet
to singlet transition
x2 − y2
a2Љ(pz) → eЈ(d
, dxy). This assignment is the same
as that made for related P3Au trigonal planar systems
and the platinum(0) complexes [32]. The [(NP3)Au]+
complexes show shifts in the emission energies,
depending on the anion used. However, none of the
anions interact directly with the gold(I) centers and
there is no obvious correlation between the anion used
and the emission energy. The small differences in
emission energy maxima are thought to be due to
conformation differences in the molecules and
packing effects.
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