Rhenium complexes of di-2-pyridyl ketone, 2-benzoylpyridine and 2-hydroxybenzophenone: A structural and theoretical study

Article abstract of DOI:10.1016/j.poly.2013.06.025

The reactions of di-2-pyridyl ketone (dpk), 2-benzoylpyridine (zpy) and 2-hydroxybenzophenone (Hbp) with [Re(CO)₅Cl] (A) and trans-[ReOX ₃(PPh₃)₂] (B, X = Cl, Br) were studied. The complexfac-[Re(CO)₃ (dpk·OCH₃)] was isolated from the reaction of A with dpk in methanol. The monoanionic tridentate chelate dpk·OCH₃ was formed by the nucleophilic attack of methanol at the carbonylic carbon atom of dpk. A similar attack of water on dpk was observed in the compound cis-[ReOBr₂(dpk·OH)]·2(dpkH ⁺Br), which was formed from dpk and [ReOBr₃(PPh ₃)₂] in acetone. The reaction of zpy with B in acetonitrile produced the complexes [Re^IIIX₃(zpy)(PPh ₃)], but in methanol as solvent the compounds [ReOX ₂(zpyH)(PPh₃)] were isolated, where zpyH coordinates bidentately as the monoanionic ligand [C₆H₅(HC-O)C ₅H₄N]. With A as starting material the complexfac-[Re(CO)₃(zpy)Cl] was isolated. The complexes cis-[ReOX₂(bp)(PPh₃)] were the products of the reaction of Hbp with B in acetonitrile; however, in methanol cis-[Re^IIIBr ₂ (bp)(PPh₃)₂] was isolated. All these complexes were characterized by conductance measurements, elemental analyses, UV-Vis, IR and NMR spectroscopy and by single crystal X-ray diffraction. DFT calculations regarding the electronic ground states show single states for all the complexes, except for the rhe-nium(III) complexes [Re^IIIX ₃(zpy)(PPh₃)] and [ReBr₂(bp)(PPh ₃)₂], in which the states are triplet. The DFT and experimental results are in agreement in all cases, especially the anisotropy of the Re-N bond length offac-[Re(CO)₃(dpk·OCH₃)] and exact O(1)-Re-O(3) angles for [ReOX₂(bp)(PPh₃)].

Full text of DOI:10.1016/j.poly.2013.06.025

Polyhedron 62 (2013) 89–103
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Rhenium complexes of di-2-pyridyl ketone, 2-benzoylpyridine
and 2-hydroxybenzophenone: A structural and theoretical study
a
b,
c
N.C. Yumata a, G. Habarurema a, J. Mukiza a, T.I.A. Gerber a, , E. Hosten , F. Taherkhani , M. Nahali
⇑
⇑
a Department of Chemistry, Nelson Mandela Metropolitan University, Port Elizabeth, South Africa
b Department of Physical Chemistry, Razi University, Kermanshah, Iran
c Department of Science, Babol Noshiravani University of Technology, Babol, Iran
a r t i c l e i n f o
a b s t r a c t
Article history:
The reactions of di-2-pyridyl ketone (dpk), 2-benzoylpyridine (zpy) and 2-hydroxybenzophenone (Hbp)
with [Re(CO)5Cl] (A) and trans-[ReOX3(PPh3)2] (B, X = Cl, Br) were studied. The complex fac-[Re(CO)3
(dpkꢀOCH3)] was isolated from the reaction of A with dpk in methanol. The monoanionic tridentate che-
late dpkꢀOCH3 was formed by the nucleophilic attack of methanol at the carbonylic carbon atom of dpk. A
similar attack of water on dpk was observed in the compound cis-[ReOBr2(dpkꢀOH)]ꢀ2(dpkH+Brꢁ), which
was formed from dpk and [ReOBr3(PPh3)2] in acetone. The reaction of zpy with B in acetonitrile produced
the complexes [ReIIIX3(zpy)(PPh3)], but in methanol as solvent the compounds [ReOX2(zpyH)(PPh3)] were
isolated, where zpyH coordinates bidentately as the monoanionic ligand [C6H5(HC-O)C5H4N]ꢁ. With A as
starting material the complex fac-[Re(CO)3(zpy)Cl] was isolated. The complexes cis-[ReOX2(bp)(PPh3)]
were the products of the reaction of Hbp with B in acetonitrile; however, in methanol cis-[ReIIIBr2
(bp)(PPh3)2] was isolated. All these complexes were characterized by conductance measurements,
elemental analyses, UV–Vis, IR and NMR spectroscopy and by single crystal X-ray diffraction. DFT calcu-
lations regarding the electronic ground states show single states for all the complexes, except for the rhe-
nium(III) complexes [ReIIIX3(zpy)(PPh3)] and [ReBr2(bp)(PPh3)2], in which the states are triplet. The DFT
and experimental results are in agreement in all cases, especially the anisotropy of the Re–N bond length
of fac-[Re(CO)3(dpkꢀOCH3)] and exact O(1)–Re–O(3) angles for [ReOX2(bp)(PPh3)].
Received 7 May 2013
Accepted 16 June 2013
Available online 29 June 2013
Keywords:
Di-2-pyridyl ketone
2-Benzoylpyridine
Reduction
fac-[Re(CO)3]+
DFT
TD-DFT
NBO
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
complex [ReOCl2{(C5H4N)2C(O)(OH)}] [1a] and [ReI(CO)3(dpkꢀOH)]
[1b], in which the chelate acts as a uninegative tridentate ligand.
The CO-bridged pyridyl derivatives di-2-pyridyl ketone (dpk)
and 2-benzoylpyridine (zpy) were shown to have interesting
coordination behavior. It was found that dpk and zpy can coordi-
nate to the metal ion in a variety of modes. Dpk can act as a biden-
tate, tridentate or bridging ligand [1], whereas with zpy, the ligand
can either bind monodentately (through the pyridyl nitrogen or
carbonylic oxygen atom), as a neutral bidentate or as a bridging
chelate to the metal center [2–4]. Elegant work by Machura et al.
has shown that dpk coordinates as a bidentate N,O-donor ligand
in the complex [ReIIICl3(dpk)PPh3)], which on standing in chloro-
form led to the N,N-chelation of dpk in the rhenium(III) compound
[ReCl3(dpk)(OPPh3)] [5a]. It was previously reported that dpk
undergoes nucleophilic attack by water or alcohols at the carbony-
lic carbon to give complexes containing dpkꢀH2O or dpkꢀOH
(Scheme 1) [1]. Examples of the latter are the oxorhenium(V)
Interest in the metal-promoted nucleophilic attack of water
stems from the fact that ketones do not normally hydrate to a sig-
nificant degree in the absence of strong electron-withdrawing
groups [5]. It was shown that the oxidation state of the metal
determines to a large degree the coordination mode of ligands with
a ketone group. Nucleophilic attack by water/alcohol on these li-
gands is promoted by electron-deficient high oxidation state oxo-
rhenium(V) centers, whereas the coordination through the
pyridyl nitrogen and neutral carbonyl oxygen is observed in rhe-
nium(I) and (III) complexes [5].
In this account the study of the reactions of di-2-pyridyl ketone
(dpk), 2-benzoylpyridine (zpy), and also 2-hydroxybenzophenone
(Hbp), with the [ReO]3+ and [Re(CO)3]+ moieties are reported. In a
previous reaction of [Re(CO)3(dpk)Cl] with an ethanol/water mix-
ture, only the derivative [Re(CO)3(dpkꢀOH)], and not [Re(CO)3
(dpkꢀOEt)], was isolated [6]. In this study we have reacted
[Re(CO)5Cl] with dpk in methanol to produce fac-[Re(CO)3
(dpkꢀOCH3)]. Our study was extended to also include the possible
nucleophilic attack on the carbonylic carbon atom of the related
compound 2-benzoylpyridine, which, when reacted with [ReOX3
⇑
Corresponding authors. Tel.: +27 425044285 (T.I.A. Gerber).
E-mail addresses: thomas.gerber@nmmu.ac.za (T.I.A. Gerber), f.taherkani@
razi.ac.ir (F. Taherkhani).
0277-5387/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.poly.2013.06.025

90
N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
dark blue crystals, suitable for X-ray diffraction studies, were
collected by filtration. Yield = 62%, m.p. 295 °C. Anal. Calc. for
33H27Br4N6O5Re: C, 36.2; H, 2.5; N, 7.7. Found: C, 36.4; H, 2.3;
N, 7.8%. IR (cmꢁ1):
(C@O) 1693s; (C@N) 1605m, 1587m;
(C@C) 1520s; (Re@O) 950s;
(Re–N) 470s, 465s. 1H NMR
O
RO
N
OH
N
C
ROH
v
v
N
N
v
v
m
(DMSO-d6, ppm): 8.71–7.67 (Ar H). Conductivity (acetone): 122.
di-(2-pyridyl)ketone (dpk)
Scheme 1. Nucleophilic attack of ROH at the carbonylic carbon atom.
dpk.ROH
2.2.3. [ReX3(zpy)(PPh3)] (X = Cl(3), Br(4))
A mixture of trans-[ReOX3(PPh3)2] (120 lmol) and 240 lmol
(440 mg) of zpy in 20 cm3 of acetonitrile was heated under reflux
for 3 h. The resultant blue solution was cooled to room tempera-
ture and the precipitate which formed was filtered, washed with
diethyl ether and dried under vacuum. Blue crystals were obtained
by the slow evaporation of the mother liquor.
(PPh3)2] (X = Cl, Br), produced the species [ReIIIX3(zpy)(PPh3)] in
acetonitrile but [ReOX2(zpyH)(PPh3)] in methanol. In the latter
reaction the coordinated zpy ligand has been reduced to the phe-
nyl-2-pyridylmethanolate anion [zpyHꢁ, {C6H5(HC-O)C5H4N}ꢁ)].
These results are similar to those reported by Machura et al., albeit
under different experimental conditions [7]. We have also studied
the coordination behavior of the related ligand 2-hydroxybenzo-
phenone, which on reaction with [ReOX3(PPh3)2] in methanol
and acetonitrile gave the products [ReIIIX2(bp)(PPh3)2] and
[ReVOX2(bp)(PPh3)] respectively, with no nucleophilic attack on
the carbonylic carbon of bpꢁ being observed.
(3): Yield = 65%, m.p. 265 °C. Anal. Calc. for C30H24Cl3NOPRe: C,
48.8; H, 3.3; N, 1.9. Found: C, 48.3; H, 3.3; N, 2.1%. IR (cmꢁ1):
v
(C@O) 1590 m;
v
(C@N) 1605 m, 1587 m;
v(C@C) 1520s; v(Re–N)
499m; (Re–O) 424m;
m
m
(Re–Cl) 324m. 1H NMR (DMSO-d6, ppm):
8.73 (d, 1H, H25); 8.62 (t, 1H, H23); 8.45 (d, 1H, H22); 8.09 (t, 1H,
H24); 8.59–7.79 (m, 4H, H12, H13, H14, H16); 7.62–7.59 (16H,
H15, PPh3). UV–Vis (CH2Cl2, kmax (e
, Mꢁ1 cmꢁ1)): 318 (19800);
428 (3960); 597(9320). Conductivity (acetone): 125.
2. Experimental
(4): Yield = 68%, m.p. 268 °C. Anal. Calc. C30H24Br3NOPRe: C,
41.3; H, 2.8; N, 1.6. Found: C, 41.3; H, 2.7; N, 1.8%. IR (cmꢁ1):
2.1. Materials and instrumentation
v
(C@O) 1589m;
v(C@N) 1605m, 1587m; v(C@C) 1520s; v(Re–N)
495m;
m
(Re–O) 427m. 1H NMR (DMSO-d6, ppm): 8.73 (d, 1H,
All materials were commercially available and used as received.
trans-[ReOX3(PPh3)2] (X = Cl, Br) was prepared by a literature
method [8], and [Re(CO)5Cl] and the ligands di-2-pyridyl ketone
(dpk), 2-benzoylpyridine (zpy) and 2-hydroxybenzophenone
(Hbp) were obtained from Aldrich.
H15); 8.62 (t, 1H, H13); 8.45 (d, 1H, H12); 8.09 (t, 1H, H14);
8.59–7.79 (m, 4H, H22, H23, H24, H26); 7.62–7.59 (16H, H25,
PPh3). UV–Vis (CH2Cl2, kmax (e
, Mꢁ1 cmꢁ1)): 321 (10940); 468
(2200); 611(4960). Conductivity (acetonitrile): 128.
Infrared (IR) spectra were recorded on a Digilab FTS3100 Excal-
ibur HE spectrophotometer and were run as KBr pellets. 1H NMR
spectra were recorded on a Bruker Avance 300 MHz spectrometer
as solutions in DMSO-d6 at 25 °C, using TMS as internal standard.
Electronic spectra were obtained with a Shimadzu UV-3100 spec-
trophotometer. Microanalyses were obtained on a Carlo Erba
EA1108 elemental analyser, and melting points were determined
on an Electrothermal IA-900 apparatus. Conductivity measure-
ments (in the unit ohmꢁ1 cm2 molꢁ1) were carried out with
10ꢁ3 M solutions at 298 K with a Phillips PW9509 conductometer.
2.2.4. [ReOX2(zpyH)(PPh3)] (X = Cl(5), Br(6))
To a suspension of 120
of methanol was added 240
l
mol of trans-[ReOX3(PPh3)2] in 20 cm3
l
mol of zpy. After the mixture was
heated under reflux for 4 h, it was cooled to room temperature
and a brown precipitate was collected by filtration.
(5): Yield = 73%, m.p. 259 °C. Anal. Calc. for C30H25Cl2NO2PRe: C,
50.1; H, 3.5; N, 1.9. Found: C, 50.0; H, 3.3; N, 1.8%. IR (cmꢁ1):
v
(Re@O) 948s; m(Re–N) 473s, 468s; m(Re–O) 428m; m(Re–Cl)
329m, 318m. 1H NMR (DMSO-d6, ppm): 9.21 (s, 1H, H1); 8.71 (d,
1H, H15); 8.62 (t, 1H, H13); 8.45 (d, 1H, H12); 8.09 (t, 1H, H14);
8.69–7.74 (m, 4H, H22, H23, H24, H26); 7.69–7.23 (16H, H25;
2.2. Syntheses of the complexes
PPh3). UV–Vis (CH2Cl2, kmax (e
, Mꢁ1 cmꢁ1)): 345 (7280). Conductiv-
ity (acetone): 112.
2.2.1. fac-[Re(CO)3(dpkꢀOCH3)] (1)
(6): Yield = 69%, m.p. 265 °C. Anal. Calc. for C30H25Br2NO2PRe: C,
A mixture of dpk (109 mg, 592 lmol) and [Re(CO)5Cl] (107 mg,
44.6; H, 3.1; N, 1.7. Found: C, 44.4; H, 2.9; N, 1.7%. IR (cmꢁ1):
296 l
mol) was heated at reflux in 20 cm3 of methanol for 2 h under
v
(Re@O) 944s; m(Re–N) 470s, 465s; m
(Re-Br) 306m, 298m. 1H
nitrogen. The resultant yellow solution was cooled to room temper-
ature and the precipitate which formed was filtered, washed with
diethyl ether and dried under vacuum. Orange crystals were ob-
tained by the slow evaporation of the mother liquor. Yield = 73%,
m.p. 278 °C. Anal. Calc. for C15H11N2O5Re: C, 37.1; H, 2.3; N, 5.8.
NMR (DMSO-d6, ppm): 9.21 (s, 1H, OH); 8.74 (d, 1H, H15); 8.64
(t, 1H, H13); 8.31 (d, 1H, H12); 8.19 (t, 1H, H14); 8.59–7.79 (m,
4H, H22, H23, H24, H26); 7.71–7.45 (15H, PPh3). UV–Vis (CH2Cl2,
kmax (e
, Mꢁ1 cmꢁ1)): 365 (7520). Conductivity (acetone): 118.
Found: C, 37.3; H, 2.1; N, 5.9%. IR (cmꢁ1):
m
(C@O)fac 2007vs,
1914vs, 1857vs; m(C@N) 1585m; m(C@C) 1540m, 1463m; m(Re–N)
2.2.5. fac-[Re(CO)3Cl(zpy)].toluene (7)
A mixture of zpy (107 mg, 545 mol) and [Re(CO)5Cl] (103 mg,
277
mol) was refluxed in 20 cm3 of toluene for 4 h under nitro-
484m, 430m. 1H NMR (DMSO-d6, ppm): 9.23 (d, 2H, H15, H25);
8.42 (t, 2H, H13, H23); 8.21 (d, 2H, H12, H22); 8.13 (t, 2H, H14,
l
l
H24); 3.48 (s, 3H, OCH3). UV–Vis (dichloromethane, kmax (e
, Mꢁ1
gen. The crystalline maroon precipitate separated upon cooling,
and was removed by filtration. Maroon crystals were obtained by
the slow evaporation of the mother liquor. Yield = 73%, m.p.
242 °C. Anal. Calc. for C15H9ClNO4ReꢀC7H8: C, 42.1; H, 2.6; N, 2.6.
cmꢁ1)): 318 (2260); 377 (540). Conductivity (MeOH): 95.
2.2.2. cis-[ReOBr2(dpkꢀOH)]ꢀ2(dpkH+Brꢁ) (2)
To a 102 mg (106
l
mol) suspension of trans-[ReOBr3(PPh3)2] in
Found: C, 42.0; H, 2.8; N, 2.4%. IR (cmꢁ1):
m
(C@O)fac 2021vs,
(C@C) 1550m; (Re–N) 460m;
m
(Re–Cl) 316m. 1H NMR (DMSO-d6, ppm): 8.72 (d, 1H, H15); 8.08
5 cm3 of acetone was added 381 mg (207
lmol) of dpk dissolved in
1916vs, 1857s;
m
(C@N) 1571m;
m
m
10 cm3 of acetone. The reaction mixture was heated under reflux
for 8 h, cooled to room temperature, and a blue precipitate was re-
moved by filtration and dried under vacuum. The mother liquor
was left to evaporate slowly at room temperature. After 2 days
(t, 1H, H13); 7.91–8.01(m, 3H, H12, H14, H24); 7.73 (t, 2H, H22,
H26); 7.65 (t, 2H, H23, H25). UV–Vis (dichloromethane, kmax
(e
, Mꢁ1 cmꢁ1)): 475 (6820). Conductivity (methanol): 85.

Table 1
Crystal and structure refinement data for complexes 1 to 10.
1
2
3
4
5
6
7
8
9
10
Formula weight
Crystal system
Space group
a (Å)
b (Å)
c (Å)
485.47
1093.4
738.03
monoclinic
P21/c
11.6050(2)
15.2606(2)
19.2831(2)
871.38
monoclinic
P21/c
11.6368(3)
15.3684(4)
19.3340(4)
719.59
monoclinic
P21/c
17.2854(5)
8.7393(3)
20.3956(7)
808.49
monoclinic
P21/c
17.6053(4)
8.8682(2)
20.5226(4)
534.95
1067.8
orthorhombic
P212121
12.6306(3)
18.1969(5)
18.8268(6)
732.58
orthorhombic
P212121
9.3659(1)
15.2231(2)
19.2618(3)
821.48
orthorhombic
P212121
9.3959(2)
15.3556(3)
19.5802(4)
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
7.820(5)
9.052(5)
12.477(5)
106.525(5)
95.753(5)
111.924(5)
764.0(7)
2
8.9727(3)
13.0202(4)
16.2048(5)
68.707(1)
81.943(1)
79.495(1)
1728.7(1)
2
7.875(5)
9.756(5)
12.185(5)
77.077(5)
83.389(5)
89.240(5)
906.3(8)
2
a
(°)
b (°)
(°)
127.001(1)
125.273(1)
118.534(2)
119.997(1)
c
Volume (Å3)
Z
2727.3(7)
4
1.797
2822.9(1)
4
2.05
2706.77(2)
4
1.766
2774.95(1)
4
1.935
4327.1(2)
4
1.639
2727.32(7)
4
1.772
2825.03(1)
4
1.931
Dcalc (g cmꢁ3
)
2.11
7.979
2.101
8.188
1.96
6.874
l
(mmꢁ1
)
4.833
8.633
4.775
7.345
4.767
4.71
7.218
F(000)
460
1044
1440
1656
1408
1552
510
2096
1432
1576
h range (°)
Index ranges
2.6–28.4
ꢁ10 6 h 6 10
ꢁ12 6 k 6 12
ꢁ16 6 ‘ 6 15
3765
2.5–28.3
ꢁ11 6 h 6 11
ꢁ17 6 k 6 17
ꢁ21 6 ‘ 6 21
7914
2.6–28.3
ꢁ15 6 h 6 13
ꢁ20 6 k 6 20
ꢁ20 6 ‘ 6 24
3792
1.9–28.3
ꢁ15 6 h 6 15
ꢁ20 6 k 6 18
ꢁ25 6 ‘ 6 25
5661
2.6–28.4
ꢁ20 6 h 6 23
ꢁ11 6 k 6 11
ꢁ27 6 ‘ 6 20
4579
2.5–32.3
ꢁ24 6 h 6 26
ꢁ13 6 k 6 13
ꢁ30 6 ‘ 6 30
5986
2.1–28.3
ꢁ10 6 h 6 10
ꢁ12 6 k 6 13
ꢁ16 6 ‘ 6 16
4478
2.2–28.3
ꢁ16 6 h 6 15
ꢁ24 6 k 6 24
ꢁ25 6 ‘ 6 25
9717
2.1–28.3
ꢁ7 6 h 6 12
ꢁ20 6 k 6 20
ꢁ25 6 ‘ 6 24
6441
2.1–28.3
ꢁ12 6 h 6 12
ꢁ20 6 k 6 19
ꢁ26 6 ‘ 6 25
6610
Observed data [I > 2.0r(I)]
Parameters
210
1.09
444
1.15
334
0.62
334
1.01
4579
0.96
334
0.95
251
1.07
506
1.02
343
0.79
343
1.04
Goodness of fit (GoF) on F2
Final R indices: R
0.0164
0.0407
0.03
1.11/ꢁ1.01
0.0167
0.0406
0.02
0.50/ꢁ0.77
0.0196
0.0336
0.0369
0.56/ꢁ0.38
0.0256
0.0616
0.038
0.0346
0.0531
0.061
1.20/ꢁ0.80
0.0405
0.0692
0.058
1.75/ꢁ1.02
0.0235
0.0601
0.029
1.70/ꢁ1.45
0.0214
0.0425
0.029
0.98/ꢁ0.38
0.0124
0.029
0.015
0.34/ꢁ0.32
0.0162
0.0336
0.02
0.66/ꢁ0.44
wR2
Rint
Peak/hole (e Åꢁ3
)
1.63/1.20
Chemical formula: 1: C15H11N2O5Re; 2: C11H9Br2N2O3Re,2(C11H9N2O),2(Br); 3: C30H24Cl3NOPRe; 4: C30H24Br3NOPRe; 5: C30H25Cl2NO2PRe; 6: C30H25Br2NO2PRe; 7: C15H9ClNO4Re, 0.5(C7H8); 8: C49H39Br2O2P2Re; 9: C31H24Cl2O3PRe;
10: C31H24Br2O3PRe.

92
N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
Table 2
Selected bond lengths [Å] and angles (°) for complexes 1 to 10.
1
Re–O(1)
Re–N(1)
Re–N(2)
O(1)–C(1)
2.095(2)
2.178(3)
2.176(3)
1.376(3)
Re–C(30)
Re–C(31)
Re–C(32)
O(2)–C(2)
1.911(4)
1.915(3)
1.430(3)
1.430(3)
O(1)–Re–C(31)
O(1)–Re–N(1)
O(1)–Re–N(2)
C(1)–O(2)–C(2)
O(1)–C(1)–O(2)
O(1)–C(1)–C(21)
169.5(1)
74.8(8)
74.6(8)
114.4(2)
114.4(2)
108.5(2)
N(1)–Re–C(30)
N(1)–Re–N(2)
N(2)–Re–C(32)
C(11)–C(1)–C(21)
O(1)–C(1)–C(11)
C(11)–C(1)–O(2)
171.7(1)
82.0(9)
172.3(1)
127.1(2)
107.4(2)
112.5(2)
2
Re–O(11)
Re–Br(11)
ReN(11)
O(11)–C(1)
1.966(1)
2.482(3)
2.154(2)
1.403(2)
Re–O(13)
Re–Br(12)
Re–N(12)
O(12)–C(1)
1.682(2)
2.488(3)
2.140(2)
1.368(3)
O(11)–Re–O(13)
O(11)–Re–Br(11)
O(11)–Re–Br(12)
O(11)–Re–N(11)
O(11)–Re–N(12)
O(11)–C(1)–C(111)
Br(11)–Re–N(12)
N(11)–C(111)–C(1)
Re–N(11)–C(111)
157.0(7)
92.4(5)
87.8(8)
74.2(7)
74.4(7)
105.4(2)
168.0(5)
110.7(2)
112.7(2)
N(11)–Re–N(12)
O(13)–Re–Br(11)
O(13)–Re–Br(12)
O(13)–Re–N(11)
O(13)–Re–N(12)
O(12)–C(1)–C(111)
Br(12)–Re–N(11)
N(12)–C(121)–C(1)
Re–N(12)–C(121)
84.9(7)
103.7(6)
102.6(6)
90.0(8)
87.8(8)
110.3(2)
166.6(5)
110.8(2)
113.2(1)
3
4
3
4
Re–X(1)
Re–X(2)
Re–X(3)
O(1)–C(2)
C(1)–O(1)
2.337(8)
2.341(8)
2.415(1)
1.285(3)
2.480(3)
2.481(4)
2.572(5)
Re–O(1)
Re–N(1)
Re–P(1)
N(1)–C(25)
C(11)–N(1)
2.001(2)
2.062(2)
2.446(1)
1.351(4)
2.016(2)
2.074(3)
2.446(2)
1.287(4)
1.382(4)
X(1)–Re–N(1)
X(1)–Re–X(2)
X(3)–Re–P(1)
O(1)–Re–X(2)
167.9(7)
95.1(3)
177.3(3)
172.0(6)
169.4(8)
94.4(1)
176.1(3)
171.3(7)
O(1)–Re–N(1)
P(1)–Re–X(1)
P(1)–Re–N(1)
P(1)–Re–O(1)
75.5(9)
92.2(3)
90.8(8)
93.4(7)
75.6(1)
92.8(2)
90.4(2)
92.1(8)
5
6
5
6
Re–X(1)
Re–O(1)
Re–P(1)
2.412(1)
1.919(3)
2.470(1)
1.347(6)
2.496(5)
1.920(3)
2.477(1)
1.351(6)
Re–X(2)
Re–O(2)
Re–N(1)
C(1)–O(1)
2.352(1)
1.700(3)
2.197(2)
1.422(5)
2.560(5)
1.686(3)
2.140(3)
1.417(4)
C(11)–N(1)
O(1)–Re–O(2)
O(2)–Re–X(1)
O(2)–Re–N(1)
Cl(2)–Re–N(1)
P(1)–Re–Cl(1)
Br(1)–Re–N(1)
162.6(1)
96.6(1)
89.6(1)
164.0(1)
176.4(5)
162.5(1)
105.3(9)
89.8(1)
O(1)–Re–N(1)
O(2)–Re–X(2)
O(2)–Re–P(1)
X(2)–Re–O(2)
C(21)–C(1)–O(1)
P(1)–Re–Br(2)
74.9(1)
105.6(1)
87.0(1)
103.4(5)
110.0(3)
74.7(1)
96.2(1)
88.4(1)
101.7(9)
106.6(3)
174.5(2)
164.0(1)
7
Re–Cl(1)
Re–O(1)
Re–N(1)
O(1)–C(1)
2.464(2)
2.170(3)
2.162(3)
1.246(4)
Re–C(2)
Re–C(3)
Re–C(4)
N(1)–C(11)
1.913(4)
1.899(4)
1.911(4)
1.360(4)
O(1)–Re–C(3)
N(1)–Re–C(4)
Cl(1)–Re–C(2)
N(1)–Re–O(1)
Re–N(1)–C(11)
171.31(1)
170.9(1)
176.2(1)
73.8(1)
Cl(1)–Re–N(1)
Cl(1)–Re–O(1)
C(11)–N(1)–C(15)
C(21)–C(1)–O(1)
Re–N(1)–C(15)
82.60(7)
80.69(7)
117.6(3)
119.3(3)
126.0(2)
116.4(2)
8
Re–Br(1)
Re–O(1)
Re–P(1)
C(12)–O(1)
2.523(3)
1.992(2)
2.463(6)
1.325(3)
Re–Br(2)
Re–O(2)
Re–P(2)
2.500(3)
2.020(2)
2.475(6)
1.283(3)
C(1)–O(2)
O(1)–Re–O(2)
O(1)–Re–Br(1)
O(1)–Re–Br(2)
O(1)–Re–P(1)
O(1)–Re–P(2)
Br(1)–Re–P(1)
Br(2)–Re–P(2)
P(1)–Re–P(2)
85.5(8)
88.4(5)
176.2(1)
90.6(6)
90.3(6)
93.4(2)
86.6(2)
179.2(3)
O(2)–Re–Br(1)
O(2)–Re–Br(2)
O(2)–Re–P(1)
O(2)–Re–P(2)
Br(2)–Re–Br(1)
Br(2)–Re–P(1)
Br(2)–Re–P(2)
O(2)–C(1)–C(21)
172.4(6)
86.7(5)
91.1(6)
88.9(6)
99.6(1)
86.8(2)
92.35(2)
122.0(3)

N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
93
9
10
9
10
Re–X(1)
Re–O(1)
Re–O(3)
C(1)–O(2)
2.340(5)
1.966(1)
1.689(1)
1.262(2)
2.543(3)
1.967(2)
1.675(2)
1.262(3)
Re–X(2)
Re–O(2)
Re–P(1)
2.395(6)
2.089(1)
2.472(5)
1.336(2)
2.482(2)
2.088(2)
2.470(6)
1.336(3)
C(11)–O(1)
O(1)–Re–O(3)
O(1)–Re–O(2)
O(1)–Re–X(1)
O(1)–Re–X(2)
O(1)–Re–P(1)
O(2)–Re–X(1)
O(2)–Re–X(2)
X(1)–Re–P(1)
166.0(6)
81.0(5)
92.9(4)
88.3(4)
175.1(2)
172.2(4)
85.9(4)
90.1(2)
166.1(8)
80.9(7)
87.4(5)
93.8(5)
84.2(5)
85.5(4)
172.7(4)
171.6(2)
O(3)–Re–O(2)
O(3)–Re–X(1)
O(3)–Re–X(2)
O(3)–Re–P(1)
O(2)–Re–P(1)
X(1)–Re–X(2)
X(2)–Re–P(1)
O(2)–C(1)–C(12)
87.5(6)
99.3(5)
84.3(4)
88.3(5)
94.0(4)
89.2(2)
172.8(2)
122.0(2)
87.3(7)
98.9(6)
98.6(6)
89.4(6)
93.8(5)
89.2(1)
90.7(2)
123.0(2)
Table 3
Natural charges of selected atoms for complexes 1 to 10.
Table 5
Hybrid bond orbitals and lone pairs for complex 1.
1
2
3
4
5
Label
Bond orbital
Occupancy
label/charge
2c1
2c2
2c3
2c4
2c5
2c6
0.5619(sd[2.13])Re + 0.8272(sp[0.56])C30
0.5767(sd[2.68])Re + 0.8169(sp[0.74])C31
0.8988(d)Re + 0.4384(p)C31
0.8874(sd[12.04])Re + 0.4610(sp[12.98])C31
0.5644(sd[2.16])Re + 0.8255(sp[0.56])C32
0.9627(d)Re + 0.2706(pd[0.76])C32
1.96
1.93
1.78
1.67
1.96
1.63
0.28
0.30
0.44
0.46
0.29
0.21
Re
O1
N1
N2
C30
C31
C32
0.05
ꢁ0.80
ꢁ0.49
ꢁ0.50
0.60
Re
1.21
ꢁ0.38
ꢁ0.36
ꢁ0.71
ꢁ0.50
ꢁ0.48
ꢁ0.48
Re
Cl1
Cl2
Cl3
P1
0.85
ꢁ0.37
ꢁ0.40
ꢁ0.40
1.11
Re
0.66
ꢁ0.31
ꢁ0.35
ꢁ0.36
1.11
Re
Cl2
Cl1
P1
O1
O2
N1
1.10
ꢁ0.39
ꢁ0.46
1.14
ꢁ0.69
ꢁ0.50
ꢁ0.47
Br11
Br12
O11
O13
N11
N12
Br1
Br2
Br3
P1
O1
N1
0.51
0.60
O1
N1
ꢁ0.58
ꢁ0.57
2c1⁄
2c2⁄
2c3⁄
2c4⁄
2c5⁄
2c6⁄
0.8272(sd[2.13])Re ꢁ 0.5619(sp[0.56])C30
0.8169(sd[2.68])Re ꢁ 0.5767(sp[0.74])C31
0.4384(d)Re ꢁ 0.8988(p)C31
ꢁ0.49
ꢁ0.49
6
7
8
9
10
0.4610(sd[12.04])Re ꢁ 0.8874(sp[12.98])C31
0.8255(sd[2.16])Re ꢁ 0.5644(sp[0.56])C32
0.2706(d)Re ꢁ 0.9627(pd[0.76])C32
label/charge
Re
Br1
Br2
P1
0.99
ꢁ0.34
ꢁ0.42
1.15
Re
C2
C3
C4
O1
N1
Cl1
0.00
0.53
0.59
Re
Br1
Br2
P1
P2
O1
O2
0.52
ꢁ0.41
ꢁ0.39
1.10
Re
Cl1
Cl2
P1
O1
O2
O3
1.14
ꢁ0.39
ꢁ0.42
1.14
ꢁ0.70
ꢁ0.60
ꢁ0.41
Re
Br1
Br2
P1
O1
O2
O3
1.03
ꢁ0.37
ꢁ0.34
1.15
ꢁ0.69
ꢁ0.60
ꢁ0.40
Label
Lone pair
Occupancy
0.62
O1
N1
N2
sp[0.91], p, sp[5.41]
sp[3.24]
sp[3.21]
1.93, 1.87,1.68
1.72
1.72
O1
O2
N1
ꢁ0.68
ꢁ0.50
ꢁ0.48
ꢁ0.54
ꢁ0.46
ꢁ0.56
1.11
ꢁ0.66
ꢁ0.60
2.2.7. cis-[ReOX2(bp)(PPh3)] (X = Cl(9), Br(10))
Hbp (240 mol) was added to a solution of trans-[ReOX3(PPh3)2]
(120
mol) in 20 cm3 of acetonitrile and the mixture was stirred at
reflux for 3 h. The color of the reaction mixture turned green and,
after cooling to room temperature, the solution was filtered and left
to evaporate slowly at room temperature. After two days green X-
ray quality crystals were collected by filtration.
l
2.2.6. cis-[ReBr2(bp)(PPh3)2] (8)
Hbp (408 mg, 206
mol) was dissolved in 10 cm3 of methanol,
and added to 0.100 g (103 mol) of trans-[ReOBr3(PPh3)2] in
l
l
l
10 cm3 of methanol. The resulting solution was heated under re-
flux for an hour and then cooled to room temperature. It was fil-
tered and left to evaporate slowly at room temperature. After
4 days green crystals, suitable for X-ray diffraction studies, were
collected by filtration. Yield = 68%, m.p. 267 °C. Anal. Calc. for
(9): Yield = 70%, 270 °C. Anal. Calc. for C31H24Cl2O3PRe: C, 50.8;
H, 3.3. Found: C, 50.6; H, 3.5%. IR (cmꢁ1):
v
(Re@O) 948s;
v(Re–O)
478s;
v
(Re–Cl) 306m. 1H NMR (DMSO-d6, ppm): 7.69 (d, 2H, H22,
C49H39Br2O2P2Re: C, 55.1; H, 3.7. Found: C, 55.2; H, 3.6%. IR
H26); 7.64–7.51 (m, 18H, H13, H23, H25, PPh3); 7.01–6.92 (m, 4H,
H14, H24, H15, H16, H24). Conductivity (DMF): 70.
(cmꢁ1):
v(C@O) 1630s; m(Re–O) 436m. Conductivity (DMF): 83.
(10): Yield = 72%, m.p. 275 °C. Anal. Calc. for C31H24Br2O3PRe: C,
45.3; H, 2.9. Found: C, 45.2; H, 3.6%. IR (cmꢁ1):
v
(Re@O) 947s;
v
(Re–O) 498m. 1H NMR (DMSO-d6, ppm): 7.75–6.80 (m, 24H). Con-
Table 4
ductivity (DMF): 75.
NLMO/NPA bond orders of selected (rhenium–X) bonds for complexes 1 to 10.
1
2
3
4
5
2.3. X-ray crystallography
X(label)/B.O.
O1
N1
N2
C30
C31
C32
6
0.17
0.15
0.15
0.89
1.15
0.94
Br11
Br12
O11
O13
N11
N12
7
0.55
0.54
0.67
1.49
0.51
0.23
Cl1
Cl2
Cl3
P1
O1
N1
8
0.57
0.52
0.48
0.41
0.37
0.32
Br1
Br2
Br3
P1
O1
N1
9
0.60
0.57
0.50
0.41
0.33
0.37
Cl2
Cl1
P1
O1
O2
N1
10
0.53
0.34
0.52
0.40
1.45
0.22
X-ray diffraction studies for all the complexes were performed
at 200(2) K using a Bruker Kappa Apex II diffractometer with
graphite-monochromated Mo Ka (k = 0.71073 Å) radiation. Further
details are given in Table 1. The structures were solved by direct
methods. Non-hydrogen atoms were refined with anisotropic dis-
placement parameters; hydrogen atoms bound to carbon were ide-
alized and fixed. Complex 1 was refined with an extinction
parameter. Complexes 2, 3, 5, 6, 8, 9 and 10 had one or more reflec-
tions omitted that were partially obscured by the beam stop. Com-
plex 7 has solvent toluene disordered at a special position. The
toluene ring was constrained to a regular hexagon with AFIX 66.
Complex 8 has been refined as an inversion twin. Numerical
X(label)/B.O.
Br1
Br2
P1
O1
O2
N1
0.57
0.34
0.54
0.42
1.46
0.21
C2
C3
C4
O1
N1
Cl1
1.03
0.98
0.92
0.14
0.16
0.23
Br1
Br2
P1
P2
O1
O2
0.50
0.53
0.40
0.39
0.35
0.23
Cl1
Cl2
P1
O1
O2
O3
0.53
0.49
0.45
0.29
0.20
1.60
Br1
Br2
P1
O1
O2
O3
0.55
0.57
0.36
0.31
0.19
1.57

94
N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
Table 6
Hybrid bond orbitals and lone pairs for complex 2.
Label
Bond orbital
Occupancy
2c1
2c2
2c3
2c4
2c5
3C1
0.5140(sd[1.49])Re + 0.8578(sp[6.33])Br11
1.94
1.84
1.89
1.97
1.93
1.84
0.29
0.30
0.29
0.22
1.62
0.23
0.4621(sp[1.07]d[3.93])Re + 0.8868(sp[6.41])Br12
0.4163(sp[2.33]d[13.02])Re + 0.9092(sp[2.68])O13
0.5526(d)Re + 0.8335(p)O13
0.5354(d)Re + 0.8446(p)O13
0.2864(sp[0.63]d[1.30])Re + 0.6969(sp[4.30])O11 + 0.6575(sp[2.79])N11
0.8868(sp[1.07]d[3.93])Re ꢁ 0.4621(sp[6.41])Br12
0.9092(sp[2.33]d[13.02])Re ꢁ 0.4163(sp[2.68])O13
0.8335(d)Re ꢁ 0.5526(p)O13
2c2⁄
2c3⁄
2c4⁄
2c5⁄
3C1a⁄
3C1b⁄
0.8446(d)Re ꢁ 0.5354(p)O13
0.0181(sp[0.63]d[1.30])Re ꢁ 0.6901(sp[4.30])O11 ꢁ 0.7235 (sp[2.79])N11
0.9579(sp[0.63]d[1.30])Re ꢁ 0.1953(sp[4.30])O11 + 0.2102(sp[2.79])N11
Label
Lone pair
Occupancy
Re
d
1.92
Br11
Br12
O13
sp[0.16], p, p
sp[0.17], p, p
sp[0.47]
1.99, 1.98, 1.88
1.99, 1.98, 1.87
1.96
absorption corrections were made with SADABS [9]. Structural refine-
ments were carried out by the full-matrix least-squares method on
F2 using the program SHELXL-97 [10].
[Re(CO)5Cl] with dpk in refluxing toluene [23b], and the fac-
[Re(CO)3(dpkꢀOH)] derivative was formed when [Re(CO)3(dpk)Cl]
was suspended in ethanol in the presence of water [6].
Complex 1 is stable in air and in solution for months and is a
non-electrolyte in methanol. It is soluble in a wide range of sol-
vents including DMF, DMSO, dichloromethane and alcohols. The
infrared spectrum is characterized by intense bands at 2007,
2.4. Theoretical approach and computational details
DFT was used as implemented in the Firefly quantum chemistry
package [11] to calculate the relaxed structures, natural bond orbi-
tal (NBO) charges, atom–atom net linear natural localized molecu-
lar orbital/natural population analysis (NLMO/NPA) bond orders
and hybrid natural bond orbitals of the rhenium complexes [12].
The pre-compiled NBO 5.0 code [12] was employed in Firefly to
do the post-processing analyses. The B3LYP hybrid DFT method
[13,14], which includes 20% exact exchange and involves three
semi-empirical parameters that were obtained by fits to experi-
mental thermochemical data was employed in this work. The 6-
31+g(d,p) and 6-31g(d,p) basis sets and LANL2DZ relativistic core
potential and double zeta basis set were used for ‘‘H, Cl, O, P, N’’,
‘‘C’’, and ‘‘Re, Br’’ sets respectively [15]. Yeguas et al. have used
the same level of theory and basis sets to investigate some rhe-
nium complexes [16]. DFT calculations and NBO analysis has been
employed widely to investigate the systems containing metallic
and non-metallic elements [17–21]. Tangoulis and co-workers
showed that the NLMO/NPA method used in this work gives bond
orders which are in better agreement with the chemical nature of
the bonds involving transition metals [22]. Calculated natural
charges, NLMO/NPA bond orders, hybrid bond orbitals and lone
pairs for complexes 1 to 10 are given in 3–11 respectively.
1914 and 1857 cmꢁ1, typical of
v
(C@O) of the fac-[Re(CO)3]+ unit
(C@O) stretching fre-
[24]. The absence of the strong ketonic
v
quency in the 1630–1780 cmꢁ1 region further supports the me-
tal-promoted nucleophilic attack of methanol on the ketonic
group. The coordination of the pyridyl nitrogens is shown by the
shift of
1585 cmꢁ1 in the complex. The two medium intensity bands at
484 and 430 cmꢁ1 are assigned to (Re–N). The 1H NMR spectrum
v
(C@N) from about 1606 cmꢁ1 in the free ligand to
v
shows sharp, well-resolved peaks. The corresponding proton sig-
nals of each pyridine ring of the dpk ligand in the complex are
identical, giving the expected doublet-triplet-doublet-triplet set
of signals, and implying that the corresponding protons of the
two rings of the dpk chelate are magnetically equivalent. The
two-proton signal the furthest downfield at 9.23 ppm is ascribed
to the magnetically equivalent protons H15 and H25, which reside
on the carbon atoms adjacent to the coordinating nitrogen atoms.
The UV–Vis spectrum in dichloromethane shows a ligand-to-metal
charge transfer band at 377 nm, and an intraligand (p ?
p⁄) tran-
sition of dpkꢀOCH3 at 318 nm.
An ORTEP perspective view of the asymmetric unit of 1 is
shown in Fig. 1, with selected bond lengths and angles listed in Ta-
ble 2. The X-ray results show that the rhenium(I) complex contains
the chemically robust fac-[Re(CO)3]+ core in a distorted octahedral
geometry. The metal is coordinated to three carbonyl donors in a
facial orientation, to the two pyridyl nitrogens N(1) and N(2) and
the deprotonated oxygen O(1) of dpk. The Re–CO bond distances
[average of 1.913(3) Å] fall in the range observed [1.900(2)–
1.928(2) Å] for similar complexes [25,26]. The Re–N(2) bond dis-
tance [2.184(3) Å] is slightly longer than the Re–N(1) bond
[2.178(3) Å], and these values are close to those in other Re(I)–
N(imine) bonds, which typically fall in the range 2.15–2.17 Å
[1b,27–29]. The distortion from octahedral ideality in the complex
is mainly the result of the trans angles, which fall in the range
169.5(1)–172.3(1)° (Table 2). These distortions are mainly the re-
sult of the constraints imposed by the tridentate coordination of
dpk, which has three bite angles [N(1)–Re–O(1) = 74.8(8)°, N(2)–
Re–O(1) = 74.6(8)° and N(1)–Re–N(2) = 82.0(9)°]. The angles
3. Results and discussion
3.1. fac-[Re(CO)3(dpkꢀOCH3)] (1)
The compound was prepared by the reaction of [Re(CO)5Cl]
with two equivalents of di-2-pyridyl ketone (dpk) in refluxing
methanol under nitrogen. The equation for the reaction is
½ReðCOÞ5Clꢂ þ dpk þ MeOH ! fac-½ReðCOÞ3ðdpk ꢀ OCH3Þꢂ þ HCl
þ 2CO
The nucleophilic attack of the solvent at the carbonylic carbon
atom to give dpkꢀOCH3 is not surprising; it was previously shown
in the coordination chemistry of dpk with copper complexes
[23a]. fac-[Re(CO)3(dpk)Cl] was isolated from the reaction of

N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
95
Table 7
Table 8
Hybrid bond orbitals and lone pairs for complexes 3 and 4.
Hybrid bond orbitals and lone pairs for complexes 5 and 6.
3
5
Label
Bond orbital
Occupancy
Label
Bond orbital (
a)
Occupancy
2c1
2c2
2c3
2c4
0.5191(sd[4.23])Re + 0.8547(sp[4.49])Cl2
0.5795(sd[3.34])Re + 0.8150(sp[2.84])P1
0.5581(d)Re + 0.8298(sp[9.63])O2
0.5650(d)Re + 0.8251(p)O2
0.8547(sd[4.23])Re ꢁ 0.5191(sp[4.49])Cl2
0.8150(sd[3.34])Re ꢁ 0.5795(sp[2.84])P1
0.8298(d)Re ꢁ 0.5581(sp[9.63])O2
0.8251(d)Re ꢁ 0.5650(p)O2
1.97
1.91
1.98
1.98
0.39
0.52
0.27
0.30
2c1
2c2
2c3
a
a
a
0.4915(sd[2.2])Re + 0.8709(sp[4.04])Cl1
0.4777(sd[2.39])Re + 0.8785(sp[4.11])Cl2
0.5564(sd[1.57])Re + 0.8309(sp[2.81])P1
0.8785(sd[2.39])Re ꢁ 0.4777(sp[4.11])Cl2
0.98
0.98
0.94
0.15
2c2⁄a
2c1⁄
2c2⁄
2c3⁄
2c4⁄
Label
Lone pair (
a)
Occupancy
Re
Cl1
Cl2
Cl3
O1
N1
P1
d, d, d
sp[0.43], sp[9.05], p
sp[0.32], p, p
sp[0.89], sp[2.57], p
sp[1.99], sp[2.73]
sp[3.07]
0.98, 0.97, 0.90
0.99, 0.99, 0.98
0.99, 0.98, 0.98
0.99, 0.99, 0.98
0.98, 0.85
Label
Lone pair
Occupancy
Re
d
1.91
Cl2
Cl1
O2
O1
N1
Re⁄
sp[0.22], p, p
sp[0.34], sp[8.86], p, sp[5.53]
sp[0.50], sp[2.73]
sp[1.02], p, sp[4.61]
sp[3.07], p
1.99, 1.98, 1.86
1.99, 1.98, 1.90, 1.56
1.96, 1.62
1.89, 1.76, 1.68
1.66, 1.30
0.82
0.72
sp[5.61]
Label
Bond orbital (b)
Occupancy
2c1b
2c2b
2c3b
2c4b
2c1⁄b
2c2⁄b
2c3⁄b
2c4⁄b
0.4811(sd[4.05])Re + 0.8767(sp[3.74])Cl1
0.5170(sd[3.61])Re + 0.8560(sp[4.34]])Cl3
0.4103([d])Re + 0.9120([p])O1
0.98
0.98
0.90
0.81
0.16
0.25
0.26
0.27
sd[0.79]
0.48
6
0.4562([d])Re + 0.8899([p])N1
Label
Bond orbital
Occupancy
0.8767(sd[4.05])Re ꢁ 0.4811(sp[3.74])Cl1
0.8560(sd[3.61])Re ꢁ 0.5170(sp[4.34])Cl3
0.9120([d])Re ꢁ 0.4103([p])O1
2c1
2c2
2c3
2c4
0.5451(sd[3.72])Re + 0.8384(sp[6.30])Br1
0.5966(sd[3.25])Re + 0.8026(sp[2.89])P1
0.5598(sd[98.19])Re + 0.8286(sp[10.65])O2
0.5649(d)Re + 0.8252(p)O2
0.8384(sd[3.72])Re ꢁ 0.5451(sp[6.30])Br1
0.8026(sd[3.25])Re ꢁ 0.5966(sp[2.89])P1
0.8286(d)Re ꢁ 0.5598(sp[10.65])O2
0.8252(d)Re ꢁ 0.5649(p)O2
1.97
1.92
1.98
1.98
0.39
0.56
0.26
0.30
0.8899([d])Re ꢁ 0.4562([p])N1
Label
Lone pair (b)
Occupancy
2c1⁄
2c2⁄
2c3⁄
2c4⁄
Cl1
Cl2
Cl3
P1
sp[0.29], p, p
0.99, 0.90, 0.89
0.99, 0.92, 0.90, 0.80
0.99, 0.94, 0.90
0.72
0.95, 0.85
0.83
sp[0.29], p, p, sp[3.84]
sp[0.89], sp[2.57], p
sp[5.61]
sp[1.45], sp[4.13]
sp[3]
Label
Lone pair
Occupancy
O1
N1
Re
d
1.92
Re⁄
sd[3.38], sd[1.93]
0.27, 0.22
Br1
Br2
O2
sp[0.16], p, p
1.99, 1.97, 1.87
1.99, 1.98, 1.92, 1.52
1.96, 1.63
1.89, 1.76, 1.69
1.66
sp[0.36], sp[5.65], p, sp[7.86]
sp[0.51], sp[2.99]
sp[1.01], p[1.76], sp[4.80]
sp[3.23]
4
O1
Label
Bond orbital (
a)
Occupancy
N1
2c1
2c2
2c3
a
a
a
0.5169(sd[2.21])Re + 0.8560(sp[5.57])Br1
0.5018(sd[2.35])Re + 0.8650(sp[5.63])Br2
0.5745(sd[1.60])Re + 0.8185 sp[2.81])P1
0.8650(sd[2.35])Re ꢁ 0.5018(sp[5.63])Br2
0.98
0.98
0.95
0.15
Re⁄
sd[0.88]
0.49
2c1⁄a
Label
Lone pair (
a)
Occupancy
Table 9
Re
d, d, d
sp[0.47], sp[5.11], p
sp[0.24], p, p
sp[6.16], sp[0.44], p
sp[3.04]
0.97, 0.90, 0.98
0.98, 0.99, 0.99
0.98, 0.98, 0.99
0.99, 0.98, 0.99
0.82
Hybrid bond orbitals and lone pairs for complex 7.
Br1
Br2
Br3
N1
Label
Bond orbital
Occupancy
2c1
2c2
0.5676(sd[2.38])Re + 0.8233(sp[0.6])C2
0.9056(d)Re + 0.4240(p)C2
1.96
1.80
1.71
1.97
1.97
0.37
0.44
0.45
0.31
0.35
2c3
2c4
2c5
0.9060(d)Re + 0.4232(p)C2
Label
Bond orbital (b)
Occupancy
0.5759(sd[2.83])Re + 0.8175(sp[0.56])C3
0.5757(sd[2.60])Re + 0.8177(sp[0.56])C4
0.8233(sd[2.38])Re ꢁ 0.5676(sp[0.6])C2
0.4240(d)Re ꢁ 0.9056(p)C2
2c1b
2c2b
2c3b
2c4b
2c1b⁄
2c2b⁄
2c3b⁄
2c4b⁄
0.4979(sd[2.77])Re + 0.8672(sp[5.09])Br1
0.4827(sd[2.97])Re + 0.8758(sp[5.14])Br2
0.5244(sd[1.81])Re + 0.8515(sp[5.92])Br3
0.6035(d)Re + 0.7974(p)N1
0.98
0.98
0.98
0.87
0.38
0.15
0.13
0.24
2c1⁄
2c2⁄
2c3⁄
2c4⁄
2c5⁄
0.4232(d)Re ꢁ 0.9060(p)C2
0.7974(d)Re ꢁ 0.6035(p)N1
0.8175(sd[2.83])Re ꢁ 0.5759(sp[0.56])C3
0.8177(sd[2.60])Re ꢁ 0.5757(sp[0.56])C4
0.8672(sd[2.77])Re ꢁ 0.4979(sp[5.09])Br1
0.8758(sd[2.97])Re ꢁ 0.4827(sp[5.14])Br2
0.8515(sd[1.81])Re ꢁ 0.5244(sp[5.92])Br3
Label
Lone pair
Occupancy
Re
O1
N1
Cl1
sd[6.24]
sp[1.69], sp[3.74]
sp[3.07]
1.35
1.95, 1.78
1.73
Label
Lone pair (b)
Occupancy
Br1
Br2
Br3
N1
sp[0.22], p, p
sp[0.22], p, p
sp[0.18], p, p
sp[2.98]
0.89, 0.89, 0.99
0.90, 0.92, 0.99
0.95, 0.90, 0.99
0.83
sp[0.28], p, p, sp[4.96]
1.99, 1.97, 1.96, 1.63
Re⁄
d, sd[7.38]
0.25, 0.23
electrons to bind to the carbon atoms and does not have any lone
pair electrons. However, the 2c3, 2c4, and 2c6 hybrid bond orbitals
show that the shared electrons are mainly localized on the rhe-
nium. The Re–O(1) and both Re–N bond orders are small and the
second order perturbation theory analysis of the Fock matrix
shows that the O and N lone pair electrons are delocalized on
Re–C anti bond orbitals. The Re–N(2) and Re–N(1) calculated bond
distances are 2.239 and 2.232 Å respectively. They are in good
agreement with the experimental results which show the former
around C(1) [O(1)–C(1)–O(2) = 114.4(2)°; O(1)–C(1)–C(11) =
107.4(2)°; O(1)–C(1)–C(21) = 108.5(2)°] are further evidence of
the rehybridization of C(1) from sp2 in free dpk to sp3 in the
complex.
The theoretical calculations show that the ground state of 1 is
singlet and that the electronic configuration of rhenium is
[core]6s(0.41)5d(6.55). The rhenium uses sd2.1 and sd2.7 hybrid

96
N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
Table 10
Table 11
Hybrid bond orbitals and lone pairs for complex 8.
Hybrid bond orbitals and lone pairs for complexes 9 and 10.
Label
Bond orbital (
a)
Occupancy
9
2c1
2c2
0.4988(sd[2.59])Re + 0.8667(sd[5.35])Br1
0.4921(sd[2.55])Re + 0.8705(sp[5.20])Br2
0.5604(sd[1.29])Re + 0.8282(sp[2.38])P1
0.8667(sd[2.59])Re ꢁ 0.4968(sp[5.35])Br1
0.8705(sd[2.55])Re ꢁ 0.4921(sp[5.20])Br2
0.8282(sd[1.29])Re ꢁ 0.5604(sp[2.38])P1
0.98
0.98
0.95
0.14
0.16
0.26
Label
Bond orbital
Occupancy
2c1
2c2
2c3
2c4
2c5
2c6
0.4907(sd[1.61])Re + 0.8713(sp[4.89])Cl1
0.3758(sp[1.72]d[1.99])Re + 0.9267(sp[5.61])Cl2
0.4138(sp[1.91]d[1.96])Re + 0.9104(sp[2.91])P1
0.4766(sd[3.47])Re + 0.8791(sp[2.79])O3
0.5596(d)Re + 0.8287(p)O3
1.94
1.76
1.68
1.96
1.98
1.94
0.26
0.28
0.28
0.28
0.26
0.25
2c3
2c1⁄
2c2⁄
2c3⁄
Label
Lone pair (
a
)
Occupancy
0.5595(d)Re + 0.8288(p)O3
2c1⁄
2c2⁄
2c3⁄
2c4⁄
2c5⁄
2c6⁄
0.8713(sd[1.61])Re ꢁ 0.4907(sp[4.89])Cl1
0.9267(sp[1.72]d[1.99])Re ꢁ 0.3758(sp[5.61])Cl2
0.9109(sp[1.91]d[1.96])Re ꢁ 0.4138(sp[2.91])P1
0.8791(sd[3.47])Re ꢁ 0.4766(sp[2.79])O3
0.8287(d)Re ꢁ 0.5596(p)O3
Re
Br1
Br2
P2
O1
O2
d, d, d
sp[0.23], p, p
sp[0.51], sp[4.66], p
sp[5.17]
sp[2.68], sp[6.40], sp[3.99]
sp[2.94], sp[2.07]
0.99, 0.97, 0.92
0.99, 0.99, 0.98
0.99, 0.99, 0.99
0.70
0.98, 0.89, 0.84
0.97, 0.87
0.8288(d)Re ꢁ 0.5259(p)O3
Label
Lone pair
Occupancy
Label
Bond orbital (b)
Occupancy
Re
Cl1
Cl2
O1
O2
O3
10
d
1.91
2c1
2c2
2c3
2c4
0.4731(sd[2.85])Re + 0.8818(sp[4.57])Br1
0.4611(sd[2.79])Re + 0.8873(sp[4.45])Br2
0.5399(sd[1.53])Re + 0.8417(sp[2.39])P2
0.3742(sp[2.18])Re + 0.9274(p)O1
0.8810(sd[2.85])Re ꢁ 0.4731(sp[4.57])Br1
0.8873(sd[2.79])Re ꢁ 0.4611(sp[4.45])Br2
0.8417(sd[1.53])Re ꢁ 0.5399(sp[2.39])P2
0.9274(sp[2.18])Re ꢁ 0.3742(p)O1
0.98
0.97
0.95
0.89
0.25
0.13
0.14
0.14
sp[0.22], p, p
sp[0.21], p, p
sp[1.64], sp[4.13], p
sp[1.99], sp[3.17]
sp[0.48]
1.99, 1.98, 1.87
1.99, 1.98, 1.88
1.89, 1.76, 1.61
1.93, 1.74
1.97
2c1⁄
2c2⁄
2c3⁄
2c4⁄
Label
Bond orbital
Occupancy
Label
Lone pair (b)
Occupancy
2c1
2c2
2c3
2c4
0.5489(sd[1.32])Re + 0.8359(sp[8.08])Br1
0.5236(sd[1.79])Re + 0.8519(sp[7.00])Br2
0.4799(sd[4.29])Re + 0.8773(sp[2.85])O3
0.5665(d)Re + 0.8241(p)O3
1.94
1.94
1.96
1.99
1.99
0.49
0.27
0.29
0.26
0.28
Re
Br1
Br2
P1
O1
O2
d
0.84
sp[0.22], p, p
sp[0.23], p, p
sp[4.46]
sp[1.64], sp[3.49]
sp[2.01], sp[3.09]
0.99, 0.97, 0.92
0.99, 0.93, 0.90
0.72
0.95, 0.85
0.95, 0.86
2c5
0.5815(d)Re + 0.8135(p)O3
2c1⁄
2c2⁄
2c3⁄
2c4⁄
2c5⁄
0.8359(sd[1.32])Re ꢁ 0.5489(sp[8.08])Br1
0.8519(sd[1.79])Re ꢁ 0.5236(sp[7.00])Br2
0.8773(sd[4.29])Re ꢁ 0.4799(sp[2.85])O3
0.8241(d)Re ꢁ 0.5665(p)O3
0.8135(d)Re ꢁ 0.5815(p)O3
Label
Lone pair
Occupancy
bond length to be slightly larger. As shown in Table 4, the Re–O(1)
bond order is small, which confirms the considerably large bond
distance seen experimentally. The natural charge of rhenium is
+0.05, which is consistent with the presence of less electronegative
ligands in this complex, compared to complexes 2 and 3.
Re
Br1
Br2
P1
O1
O2
O3
d
1.92
sp[0.19], p, p
sp[0.15], p, p
sp[6.55]
sp[1.61], sp[4.25], p
sp[1.92], sp[3.26]
sp[0.48]
1.99, 1.98, 1.89
1.99, 1.98, 1.88
1.36
1.89, 1.76, 1.69
1.93, 1.74
1.97
3.2. cis-[ReOBr2(dpkꢀOH)]ꢀ2(dpkH+Brꢁ) (2)
The complex adduct was isolated from the heating under reflux
of trans-[ReOBr3(PPh3)2] with a twofold molar excess of dpk in ace-
tone in air. The same adduct was reported previously (erroneously
as [ReOBr3(dpkꢀOH)]ꢀ2{dpkH+Brꢁ}), with recrystallization from
acetonitrile [5a]. Upon complex formation, dpk undergoes nucleo-
philic attack by water at the carbonylic carbon atom to form a gem-
diol form of dpkꢀOH, which is coordinated to the rhenium(V) as a
N,N,O-donor chelate.
complicated due to the presence of the two uncoordinated mole-
cules of dpkH+ in the compound. However, the aromatic region
integrates for 24 protons. The doublet the furthest downfield at
8.70 ppm integrates for two protons, and is ascribed to the mag-
netically equivalent protons H115 and H125 of the coordinated
dpkꢀOH ligand. The four-proton doublet centered at 8.38 ppm is as-
signed to the protons on the carbons adjacent to the nitrogens of
the two free dpkH+ molecules. There are triplets at 7.68 ppm
(one proton each on C113 and C124) and at 7.78 ppm (four protons
on uncoordinated dpkH+ molecules), and a twelve-proton multi-
plet in the range 7.95–8.13 ppm.
The asymmetric unit of 2 comprises of the oxorhenium(V) com-
plex cis-[ReOBr2(dpkꢀOH)] (Fig. 2), two bromide anions and two
dpkH+ molecules. The donor atoms surrounding the rhenium are
at the apices of a distorted octahedron, in which the equatorial
plane is occupied by the two cis bromine atoms Br(11) and
Br(12) and the two terminal pyridyl nitrogen atoms of the triden-
tate ligand N(11) and N(12), with the O(13) oxo ligand coordinated
trans to the deprotonated oxygen O(11) of dpkꢀOH, which acts as a
uninegative, tridentate N,O,N-donor ligand. Severe distortions
from an ideal rhenium-centered octahedral environment results
in a non-linear N(12)–Re–Br(11) axis of 168.0(5)°, with the other
trans angles Br(12)-Re–N(11) = 166.6(5)° and O(11)–Re–O(13) =
157.0(7)° also deviating from linearity (Table 2). The rhenium atom
lies 0.169 Å out of the mean equatorial plane towards O(13), with
The complex is stable in air and is soluble in a wide range of sol-
vents including DMF, DMSO, acetone and acetonitrile. A very in-
tense band in the solid state infrared spectrum at 950 cmꢁ1 is
attributable to the Re@O stretching frequency, which is close to
the observed region of 906–948 cmꢁ1 for neutral six-coordinate
oxorhenium(V) compounds with an alcoholate oxygen atom coor-
dinated trans to the oxo group [30]. The absorption bands at
1693 cmꢁ1 is due to
v(C@O) of the protonated dpk molecules in
the outer coordination sphere. The typical pyridinic C@N and
C@C stretching vibrations give rise to strong absorptions at 1605
and 1520 cmꢁ1 respectively. There is a very broad absorption band
at 3086 cmꢁ1, which can be assigned to the
v(OH) stretching
frequency, confirming the monoanionic gem-diol form of dpkꢀOH
in the coordination sphere. The two absorption bands at 470 and
465 cmꢁ1 are attributable to
v(Re–N) of the pyridine nitrogens. In
the 1H NMR of the complex the lack of paramagnetic broadening
confirms the diamagnetic character of 2. The spectrum is

N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
97
Fig. 1. ORTEP plot of fac-[Re(CO)3(dpkꢀOCH3)] (1) showing the atom labeling;
thermal ellipsoids are drawn at 50% probability.
Fig. 2. ORTEP plot of cis-[ReOBr2(dpkꢀOH)] showing the atom labeling; thermal
ellipsoids are drawn at 50% probability. Hydrogen atoms are omitted for clarity.
the angles O(13)–Re–Br(11) = 103.7(6)°, O(13)–Re–Br(12) = 102.6
(6)°, O(13)–Re–N(11) = 90.0(8)° and O(13)–Re–N(12) =87.8(8)°.
The three bite angles of the chelate are O(11)–Re–N
(11) = 74.2(7)°, O(11)–Re–N(12) = 74.4(7)° and N(11)–Re–N(12) =
84.9(7)°. As expected, the bite angle formed by the six-membered
metallocycle [N(11)–Re–N(12)] is larger than those of the five-
membered ones.
Bond lengths and angles show no unusual features, being with-
in the range expected from the comparison of other six-coordinate
mono-oxo complexes of rhenium(V). The Re@O(13) bond length of
1.682(2) Å is within the range observed for oxorhenium(V) com-
pounds [1,31]. The Re–O(11) bond length of 1.966(1) Å is substan-
tially shorter than the usual length for a Re–O single bond [2.04 Å]
complex are electronegative which results in a large natural charge
of +1.21 on the rhenium.
3.3. [ReX3(zpy)(PPh3)] (3 and 4)
The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with a twofold
molar excess of 2-benzoylpyridine (zpy) in acetonitrile, heated at
reflux in air, gave rhenium(III) complexes of the type [ReX3(-
zpy)(PPh3)] [X = Cl (3); Br (4)], which were formed by the reduction
of rhenium(V) to (III) according to the equation
½ReVOX3ðPPh3Þ ꢂ þ zpy ! ½ReIIIX3ðzpyÞðPPh3Þꢂ þ OPPh3
2
which illustrates the delocalization of the p-electron density from
the oxo bond to the trans Re–O bond [32,33]. The average Re–N
bond length of 2.147(2) Å is typical of the rhenium(V)-pyridyl
bonds [34,35], and they are slightly shorter than those in complex
1. On average, the two pyridyl rings make a dihedral angle of
83.26° with the mean equatorial planes, and 64.69° with each
other. The N–C–C angles at the ring junctions deviate significantly
It is well known that [ReOX3(PPh3)2] is reduced to
[ReX3(MeCN)(PPh3)2] in acetonitrile by PPh3 in the absence of li-
gands. The latter complex has been shown to be a useful precursor
for the preparation of Re(III) coordination compounds [22]. In fact,
complexes 3 and 4 were synthesized previously by the reactions of
[ReX3(MeCN)(PPh3)2] with equimolar amounts of zpy in dichloro-
methane [7a]. In both the synthetic reactions of 3 and 4 the colors
of the starting materials changed to dark blue after heating for
90 min, and when heating was stopped after 3 h, blue precipitates
were collected in good yields. The elemental analyses of the
complexes are in good agreement with their formulations. The
complexes are soluble in a variety of solvents including acetone,
acetonitrile, dichloromethane and DMF. They are insoluble in alco-
hols and benzene. They are both stable for months in the solid state
and for days in solution.
from
120°
[N(11)–C(111)–C(1) = 110.7(2)°;
N(12)–C(121)–
C(1) = 110.8(2)°], and the rhenium atom lies off the lone-pair direc-
tions of 120° [C(111)–N(11)–Re(1) = 112.7(2)°; C(121)–N(12)–
Re(1) = 113.2(1)°]. There is a remarkable difference between the
O(11)–C(1) bond length [1.403(2) Å] and the O(12)–C(1) length
of 1.368(3) Å, with C(1) being sp3 hybridized [O(11)–C(1)–
C(111) = 105.4(2)°] and [O(12)–C(1)–C(111) = 110.3(2)°].
The theoretical calculations show that the ground state of 2 is a
singlet and that the rhenium’s electronic configuration is [cor-
e]6s(0.38)5d(5.35). From data in Table 6 it is clear that the bromine
(2c1, 2c2) and oxygen donor atoms (2c3, 2c4) use p electrons for
their bond formation to rhenium. The three 2c3, 2c4, and 2c5 bond
orbitals and the large Re–O(13) bond order are in accordance with
the experimental IR data. N(11) shares sp2.79 electrons with O(11)
and the rhenium electrons to make a three-center bond orbital, but
the N(12) lone pair electrons are delocalized on the Re-Br(11) anti
bond orbital. The Re–N(11) and Re–N(12) calculated bond dis-
tances are 2.185 and 2.179 Å respectively. All ligands in the
The absence of the typical ReV@O stretching frequency in the
890–1020 cmꢁ1 region implies that rhenium(III) products have
formed. The neutral bidentate coordination of zpy through the ke-
tonic oxygen in the coordination sphere of the complexes is sup-
ported by the shift of the v
(C@O) at 1667 cmꢁ1 in the free ligand
to 1590 and 1589 cmꢁ1 in 3 and 4 respectively. The Re–N stretches
appear at 499 and 495 cmꢁ1, and the Re–O ones at 427 and
425 cmꢁ1, in 3 and 4 respectively. The 1H NMR spectra of the com-
plexes are identical, with the halides having no influence on the

98
N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
signals. As zpy consists of two different ring systems, the expected
splitting of doublet-triplet-doublet-triplet is observed for the pyr-
idine protons. A one-proton doublet the furthest downfield at
8.73 ppm is assigned to the proton on C25 in complex 3 and on
C15 in complex 4. A fifteen-proton multiplet in the range 7.62–
7.59 ppm illustrates the presence of the phosphine molecule. The
blue color of the complexes leads to intense absorption bands in
the visible region of their electronic spectra. Due to their high
extinction coefficients, the absorptions at 428 nm (3) and 468 nm
also observed in complex 4. The Re–X(3) bond distances, trans to
P(1), are significantly longer than the Re–X bond distances trans
to the nitrogen and oxygen donor atoms of zpy (Table 2). All these
data suggest that the zpy chelate acts as a bidentate ligand, with
the rhenium in the +III oxidation state.
It was shown previously that the reaction of 1-isoquinolinyl
phenyl ketone (qpk) with [ReCl3(MeCN)(PPh3)2] led to the isolation
of the species [ReCl3(qpk)(PPh3)], in which the coordination of qpk
occurs through the neutral ketonic oxygen atom [Re–O = 1.990
(3) Å] and the quinolinyl nitrogen [Re–N = 2.026(3) Å] [27].
The theoretical calculations show that the ground state of 3 and
4 are triplet and that the electronic configuration of rhenium is
[core]6s(0.38)5d(5.70) and [core]6s(0.45)5d(5.82) respectively.
The rhenium uses more d and less s electrons to form bonds with
the three halides, which mainly share their p electrons rather than
their s electrons. According to the data in Table 7 for the bond orbi-
(4) are probably due to d Re(III) ? p⁄(zpy) metal-to-ligand charge
p
transfer transitions. The spectra are dominated by an intense
absorption (around 300 nm) due to the
p ?
p⁄ transition of the
aromatic rings in zpy. The d–d transitions are also observed at
597 and 611 nm in 3 and 4 respectively.
Single crystals of X-ray quality were obtained by slow evapora-
tion from the acetonitrile mother liquor. The crystal structures
show that the rhenium ion lies at the center of a distorted octahe-
dron (Figs. 3 and 4). The basal planes are defined by the two halides
X(1) and X(2), the ketonic oxygen O(1) and the pyridyl nitrogen
N(1) of zpy. The phosphorus atom P and X(3) lie in trans axial posi-
tions. Distortion from an ideal octahedral environment results in a
non-linear N(1)–Re–X(1) axis of 167.9(7)° in 3 and 169.4(8)° in 4,
with the other trans angles X(2)–Re–O(1) = 172.0(6)° and
171.3(7)° and P(1)–Re–X(3) = 177.3(3)° and 176.1(3)° in 3 and 4
respectively. The bite angle [O(1)-Re–N(1) = 75.5(9)° in 3 and
75.6(1)° in 4] of zpy is practically identical in both complexes,
and it contributes significantly to the distortion in the complexes.
The large X(1)–Re–X(2) angle of 95.1(3)° and 94.4(1)° in 3 and 4
respectively may contribute to the smaller bite angle of zpy.
The halide ions are arranged in a facial fashion, typical of the
[ReX3(L-L)(PPh3)] compounds with bipy-like ligands [36]. The
back-bonding effect of the complexes [ReX3(L-L)(PPh3)] with two
tal 2c1a in complex 3 (sp[4.04])Cl1 and 4 (sp[5.57]Br1), the bro-
mines use a larger percentage of their p electrons than the
chlorines in forming bonds to the metal. In these Re–halide bond
orbitals the ligands have large polarization coefficients (ꢃ0.8).
The 2c3b bond orbital and the corresponding anti bond orbital in
3 prove the absence of a strong Re@O double bond. Although we
couldn’t find any local bond orbital between the rhenium and the
oxygen in 4, the second order perturbation theory analysis of Fock
matrix shows delocalization of the C-O bond orbital and the oxy-
gen lone pairs on Re-Br anti bond orbitals. Overall, the Re–O bond
order in these cases proves the lack of a strong double bond and is
in agreement with our experimental data. The calculated Re–N
bond distances of 2.091 and 2.093 Å in 3 and 4 are in good agree-
ment with experiment. The C–O bond orders in 3 and 4 are 0.93
and 1.04 respectively, almost twice the mean Re-ligand bond or-
der. The calculated C–O bond distances in 3 and 4 are 1.292 and
1.289 Å respectively. All donor atoms gain negative natural charges
except phosphorus, which is caused by forming more than three
bonds (with the carbon atoms and the transition metal). The natu-
ral charge of rhenium in 3 is more positive than in 4, which is con-
sistent with the presence of more electronegative ligands in the
former.
p-acceptor ligands coordinated to a p-donor rhenium(III) center
is maximized in the facial disposition, which ensures minimum
competition between the ligands for identical metal orbitals. The
O(1) @C(2) bond [1.286(3) Å average] is weakened and longer than
the C@O [1.213(2) Å] in the free ligand [37], but is within the ex-
pected range for similar complexes [38]. The Re–N distance of
2.062(2) Å in 3 is shorter than comparable distances for saturated
amine complexes, where metal-to-ligand
p-back-bonding is not
3.4. [ReOX2(zpyH)(PPh3)] (5 and 6)
possible [28]. Similarly, the interatomic distance between the rhe-
nium atom and the oxygen atom of zpy [2.001(2) Å in 3] is shorter
than an ideal single Re–O bond length of 2.04 Å [39]. The latter is
The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with 2-benzo-
ylpyridine (zpy) in methanol in the presence of air produced the
neutral oxorhenium(V) complexes of the type [ReOX2(zpyH)(PPh3)]
[X = Cl(5); Br(6)]. Both these complexes have been synthesized pre-
viously by the reaction of equimolar quantities of [ReOX3(PPh3)2]
and zpy in ethanol containing two drops of conc. hydrochloric acid
[7b]. During the reaction the 2-benzoylpyridine [C6H5(C@O)C5H4N]
molecule was reduced to the phenyl-2-pyridylmethanolate anion
[zpyHꢁ, {C6H5(HC-O)C5H4N}ꢁ)], which coordinates to the metal
center through the deprotonated alcoholate oxygen and the pyridyl
nitrogen atom. Examples of the reduction of ketones to alcohols in
methanol by rhenium complexes could not be found in the
literature. We suggest that the reduction of zpy is of the Meerw-
ein–Ponndorf–Verley type [30], with coordination of both the
methoxide and zpy before hydride transfer from the methoxy to
the carbonyl carbon of zpy. However, in a similar study the reaction
of qpk with [ReOBr3(PPh3)2] in acetone produced the complex
[ReOBr2(qpk.OH)(PPh3)], in which nucleophilic attack of water
has occurred to the carbonylic carbon atom of qpk. The coordina-
tion of qpkꢀOH is in a bidentate monoanionic gem-diol form [5b].
The infrared spectra of the complexes display the Re@O stretch-
ing frequency at 948 and 944 cmꢁ1 in 5 and 6 respectively, which is
at the lower end of the range that is normally expected (895–
1020 cmꢁ1
corresponding to the
)
for this vibration [40]. The characteristic bands
(C@N) and (C@C) of the ligand are observed
Fig. 3. ORTEP view of 3 showing the atom labeling scheme. Atomic ellipsoids are
drawn at the 40% probability level.
v
v

N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
99
Fig. 4. ORTEP plot of 4 showing 40% probability displacement ellipsoids and the atom-numbering. Hydrogen atoms are omitted for clarity.
Fig. 5. ORTEP drawing of complex 5.
Fig. 6. ORTEP plot of complex 6.
in the range 1610–1500 cmꢁ1. Two medium intensity bands at 329
and 318 cmꢁ1 for the Re–Cl stretches in 5 indicate the presence of
the two chlorides in non-equivalent cis positions. The lower value
is assigned to the chloride coordinated in the position trans to the
phosphine ligand. The metal-promoted transformation of the ke-
tone group in zpy is supported by the broad singlet at 9.21 ppm
in both the 1H NMR spectra of 5 and 6, attributed to the proton
on the bridging carbon atom of the chelate. There are eight well
separated signals for the nine aromatic protons of zpyH, with the
signal of the ninth obscured by the peaks due to PPh3. The elec-
tronic spectra in dichloromethane display ligand-to-metal charge
transfer absorption bands at 345 and 365 nm in
respectively.
5 and 6
Perspective views of the asymmetric units of 5 and 6 are given
in Figs. 5 and 6. The neutral complexes exhibit distorted octahedral
geometries about the central rhenium(V) ion. The basal planes are
defined by the phosphorus atom P(1), two halides cis to each other
and the neutral pyridyl nitrogen N(1) of zpyH. The oxo group O(2)
and the oxygen atom of zpyH O(1) are in trans axial positions.
Distortion from an ideal rhenium-centered octahedron mainly re-

100
N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
sults in a non-linear O(2)@Re–O(1) axis [162.6(1)° in 5 and
162.5(1)° in 6], accomplished by Cl(1)–Re–P(1) and Cl(2)–Re–
N(1) angles of 176.4(5)° and 164.01(1)° in 5 and Br(2)–Re–
P(1) = 176.7(3)° and Br(1)–Re–N(1) = 164.0(1)° in 6. The metal is
lifted out of the mean equatorial plane formed by X2PN by 0.240
and 0.241 Å in 5 and 6 respectively towards O(2), which is reflected
in the non-orthogonal angles O(2)–Re–X(1) = 96.6(1)° in 5 and
105.3(9)° in 6; O(2)–Re–X(2) = 105.6(1)° (5) and 96.2(1)° (6); and
O(2)–Re–P(1) = 87.0(1)° (5) and 86.8(1)° (6). The Re@O(2) axis is
inclined at 176.7° and 177.3° with respect to the equatorial planes
in 5 and 6 respectively.
lone pair electrons are delocalized on the rhenium lone pair star,
Re–O(2), Re-P(1), and Re–Cl (2) anti bond orbitals and on rhenium
lone pair star, Re–O(2), Re–P(1), and Re–Br(1) anti bond orbitals
respectively. In 5 the nitrogen lone pair electrons are delocalized
on the rhenium lone pair star, Re–O(2), and Re–Cl(2) anti bond
orbitals. Also, the N(1)–C(15) bond orbitals are delocalized on the
Re–Cl(2) anti bond orbitals. In 6 nitrogen behaves similarly and in-
stead of Re–Cl(2) anti bond orbital the electrons are delocalized on
Re–Br(1) anti bond orbital. The phosphorus uses sp2.8 hybrid orbi-
tals to form a bond with rhenium in both complexes, and due to
over-binding gains a positive natural charge. The Re@O bond orbi-
tals in both complexes are composed of almost pure d and p elec-
trons which are shared by the rhenium and oxygen respectively.
The rhenium natural charge in 5 is more positive than in 6, which
is in good agreement with expectation.
The Re@O(2) bond lengths of 1.700(3) and 1.686(3) Å are within
the expected range with a phenolate trans to the oxo group [41].
The Re–O(1) bond lengths [1.919(3) Å (5); 1.920(3) Å (6)] are
shorter than the usual length for a Re–O single bond [2.04 Å],
which reflects the delocalization of the
p-electron density from
the oxo bond to the trans Re–O bond [42]. The Re–Cl(1) and Re–
Br(2) bond distances are significantly longer than the Re–Cl(2)
and Re–Br(1) bonds, due to the larger trans effect of the P com-
pared to the pyridyl nitrogen N(1). The bite angle [O(1)–Re–N(2)]
of the chelate is practically identical in both complexes (Table 2).
The average C(1)–O(1) bond length [1.310(6) Å] is longer than that
for a ketonic double bond.
3.5. fac-[Re(CO)3(zpy)Cl].C7H8. (7)
The title compound was synthesized from the reaction of
[Re(CO)5Cl] with a twofold molar excess of zpy in toluene under
a nitrogen atmosphere.
½ReðCOÞ5Clꢂ þ zpy ! fac-½ReðCOÞ3ðzpyÞClꢂ þ 2CO
The theoretical calculations show that the ground state of 5 and
6 are singlet and that the electronic configurations of rhenium are
[core]6s(0.37)5d(5.48) and [core]6s(0.42)5d(5.53) respectively.
The halides cis to phosphorus form a bond orbital with the rhe-
nium, with the difference that the bromides share a larger portion
of p electrons compared to the chlorides. In both cases, the halides
trans to phosphorus behave differently to the halides in the cis
positions, in that they form weaker bonds to rhenium than the
cis ones. The second order perturbation theory analysis of the Fock
matrix shows that the lone pair electrons of the halides cis to N(1)
are delocalized on the Re–P(1) and Re–P(2) anti bond and Re lone
pair and Rydberg star orbitals. The calculated Re–Cl(2), Re–Cl(1),
Re–Br(1) and Re–Br(2) bond lengths are 2.386, 2.442, 2.589 and
2.654 Å respectively, which is consistent with the listed bond
orders in Table 4 and the experimental data. In 5 and 6 the O(1)
The complex is air-stable and soluble in DMF, DMSO and dichlo-
romethane. The infrared spectrum in the solid state displays three
strong absorption bands attributable to the carbonyl stretching fre-
quencies of the fac-[Re(CO)3]+ core: a sharp intense band at
2021 cmꢁ1 and two lower-energy bands at 1916 and 1857 cmꢁ1
.
This pattern corresponds to three CO units in a facial isomer
arrangement [43]. A band at 1595 cmꢁ1 is attributed to
v
(C@O)
of the ketone group and characteristic bands of C@C and C@N
are observed in the range 1580–1550 cmꢁ1. The 1H NMR of the
complex consists of sharp, well-resolved peaks. The most informa-
tive aspect of the spectrum is the aromatic region that comprises of
a single-proton doublet at 8.72 ppm (H15), a one-proton triplet at
8.08 (H13), a three-proton multiplet in the range 7.90–8.00 ppm,
and two-proton triplets at 7.73 ppm (H22, H26) and 7.65 ppm
(H23, H25). The UV–Vis spectrum in dichloromethane only shows
a ligand-to-metal charge transfer absorption band at 475 nm.
Fig. 7. ORTEP view of complex 7. The toluene molecule is omitted for clarity.
Fig. 8. ORTEP drawing of complex 8.

N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
101
The solvent-free complex 7 was synthesized previously by the
reaction of equimolar quantities of [Re(CO)5Cl] and zpy in toluene
[36]. It crystallized in the monoclinic crystal system from
dichloromethane.
Maroon crystals of 7, suitable for X-ray crystallography, were
obtained from the slow evaporation of the reaction mixture. A per-
spective view of the asymmetric unit is shown in (Fig. 7). It con-
tains two molecules of [Re(CO)3(zpy)Cl] and a toluene molecule
of crystallization, and the crystal packing is governed by van der
Waals contacts. No intermolecular hydrogen bonds exist and weak
intramolecular hydrogen bonds are observed. The X-ray results
show that the rhenium(I) complex contains the chemically robust
fac-[Re(CO)3]+ core in a distorted octahedral geometry. The rhe-
nium(I) is coordinated to three carbonyl donors in a facial orienta-
tion, to the pyridinyl nitrogen N(1), the ketonic oxygen O(2) and
the chloride Cl(1). The Re–CO bond distances [average of
1.907(4) Å] (Table 2) fall in the range observed [1.900(2)–
1.928(2) Å] for similar complexes [24,44]. The Re–N(1) bond length
[2.162(3) Å] is slightly shorter than those observed in complexes 1
and 5. The Re–O(1) bond length of 2.170(3) Å is remarkably longer
than the Re–O bond distance in complex 5 [1.920(3) Å], proving
that the oxygen O(1) is neutral. The C(1)–O(1) distance of
1.246(4) Å corresponds to that of a double bond, and the C(21)–
C(1)–O(1) bond angle [119.3(3)°] is close to that for a sp2-hybrid-
ized carbon atom. The ligand zpy therefore acts as a neutral biden-
tate N,O-donor ligand.
Fig. 9. ORTEP drawing of complex 9 showing the atom-numbering.
The distortion from octahedral ideality in the complex is mainly
the result of the trans angles, with C(4)–Re–N(1) = 170.9(1)°, C(3)–
Re–O(1) = 171.31(1)°, and C(2)–Re–Cl(1) = 176.2(1)°. These distor-
tions are the result of the constraints imposed by the bidentate li-
gand zpy, which forms a five-membered [N(1)–Re–O(1) = 73.8(1)°]
metalloring with the rhenium center. The steric repulsion between
the chloride and the equatorially coordinated nitrogen atom
[Cl(1)–Re–N(1) = 82.60(7)°] is larger than between the chloride
and the axial oxygen [Cl(1)–Re–O(1) = 80.69(7)°]. The average C–
Re–C bond angle of 89.3(2)° is close to orthogonality. The Re–
N(1)–C(11) angle of 116.4(2)° is close to expectation for a sp2
hybridized nitrogen. The dihedral angle between the pyridyl and
phenyl rings of zpy is 40.1°.
The theoretical calculations show that the ground state of 7 is
singlet and that the electronic configuration of rhenium is [cor-
e]6s(0.42)5d(6.58). The CO ligands form the strongest bonds to
the rhenium. The carbon atoms use spꢃ0.6 hybrid or pure p elec-
trons to bind to the rhenium. The rhenium uses pure d electrons
and the larger polarization coefficient (ꢃ0.91) belongs to the tran-
sition metal. The Re–Cl (1), Re–N(1) and Re–O(1) bonds are too
weak and the Cl(1), N(1) and O(1) lone pairs are almost delocalized
on Re–C(2), Re–C(4), and Re–C(3) anti bond orbitals respectively.
The calculated Re–O(1) bond distance is remarkably larger than
usual Re–O bonds which is consistent with its small bond order.
The carbon atoms that are bound to electronegative oxygen atoms
and share their electrons with the rhenium gain positive charges.
The natural charges of the other donor atoms are negative, and
thereby creating no charge on the rhenium.
Fig. 10. ORTEP plot of complex 10 showing the atom-numbering.
region that could be attributable to
v
(ReV@O). The single peaks in
(C@O) and
the IR spectrum at 1630 and 436 cmꢁ1 are assigned to
v
v
(Re–O) respectively, which illustrate the coordination behavior of
the bp chelate in the complex. The 1H NMR spectrum consists of
poorly-resolved broad peaks, showing paramagnetic shifts and line
broadening of the signals and could not be used constructively in
deducing the structure of the complex.
3.6. cis-[ReBr2(bp)(PPh3)2] (8)
The rhenium(III) compound 8 was prepared in good yield by the
reaction of trans-[ReOBr3(PPh3)2] with Hbp in a 1:2 M ratio in meth-
anol. The surprising aspect of this reaction is the reduction of the
oxorhenium(V) center to rhenium(III), especially in the presence
of air. The reduction of the metal normally occurs by abstraction
of the oxo group by PPh3 to form OPPh3. The complex has a low sol-
ubility in polar solvents such as acetone and acetonitrile and is sta-
ble for months in the solid state, and is a non-electrolyte in DMF. The
infrared spectrum exhibits no absorption in the 890–1020 cmꢁ1
The crystal structure of the complex (Fig. 8) reveals that the
rhenium atom is at the center of a distorted octahedron. The basal
plane is defined by the phenolate and ketonic oxygens O(1) and
O(2) and two bromine atoms Br(1) and Br(2). The two phosphorus
atoms are in trans axial positions. The P(1)–Re–P(2) axis [179.2(3)°]
is linear, with the other trans angles Br(1)–Re–O(2) = 172.4(6)° and
Br(2)–Re–O(1) = 171.7(6)° deviating from linearity (Table 2). The

102
N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
metal is shifted out of the mean O2Br2 equatorial plane formed by
0.169 Å towards P(2), with the angles P(2)–Re–Br(1) = 86.6(2)°,
P(2)–Re–O(1) = 90.3(6)°, P(2)–Re–O(2) = 88.9(6)° and P(2)–Re–
Br(2) = 92.4(2)°. The bite angle of the bp chelate is O(1)–Re–
O(2) = 85.5(8)°.
The Re–P lengths of 2.463(6) and 2.475(6) Å agree well with the
average of 2.470 Å found in other rhenium(III) complexes contain-
ing two trans triphenylphosphine ligands [45,46]. The Re–O(1)
bond length of 1.992(2) Å is typical of a single rhenium-phenolate
bonds and falls in the range found for this type of bond in similar
complexes [47]. The O(2)–C(1) bond is double [1.283(3) Å], and the
bonding in the molecule is complemented by a O(2)–Hꢀ ꢀ ꢀC(66)
hydrogen bond.
The theoretical calculations show that the ground state of 8 is
triplet and that the electronic configuration of rhenium is [cor-
e]6s(0.43)5d(6.00). The bromine ligands form slightly stronger
bonds to rhenium than the other donor atoms. The data in Table 4
show that the bond orders for Re–O(1) and Re–O(2) are 0.35 and
0.23 respectively. The C(11)–C(16) phenyl ring resonates with
bond c12–O(1); however, there is no such a resonance for O(2).
As a result, the bond orders for Re–O(1) and Re–O(2) are different.
In the Re–P(1) and Re–P(2) bonds the rhenium and phosphorus
atoms use sd1.29, sp2.38 and sd1.53, sp2.39 hybrid electrons respec-
tively, and the phosphorus atoms have a larger polarization coeffi-
cient (ꢃ0.81) in both bonds. The O(2), O(1), P(1) and P(2) lone pair
electrons are delocalized on Re–Br(1), Re–Br(2), Re–P(2) and Re–
P(1) anti bond orbitals respectively. The phosphorus atoms, due
to over-binding, gain positive charges with negative charges aggre-
gating on the other donor atoms. Overall, the rhenium natural
charge is not as positive as in the complexes with less than two
phosphorus atoms.
equatorial planes depart considerably from the ideal 90° [from
88.3(6)° to 98.9(5)° (9) and from 84.2° to 98.9(5)° (10)].
The Re@O(3) distances of 1.689(1) Å (in 9) and 1.675(2) Å (in
10) compare favorably with those reported previously [50–56].
As expected, the Re–O(1) bond lengths, trans to the oxo oxygen
O(3), are significantly shorter than the equatorial Re–O(2) bond
lengths [e.g. 1.966(1) versus 2.089(1) Å in 9; 1.967(2) versus
2.088(2) Å in 10]. The C(1)–O(2) bond length [1.262(2) Å in 9;
1.262(3) Å in 10] shows this to be a double bond, with the
C(11)–O(1) and C(16)–O(1) bonds single [1.336(2) Å in 9;
1.336(3) Å in 10]. The O(2)–C(11)–C(12) angle in 9 [122.0(2)°]
and O(2)–C(1)–C(11) bond angle in 10 [123.0(2)°] show that the
C(1) atom is sp2-hybridized, and that no nucleophilic attack has oc-
curred. The Re–X(2) bond distance in 9 is significantly longer than
the Re–X(1) bond length, due to the larger trans effect of the phos-
phorus atom compared to the ketonic oxygen O(2) (Table 2). The
latter is also observed in 10. The bite angle [O(1)–Re–O(2) of
81.0(7)° (9) and 80.9(7)° (10)] of the bp ligand is practically iden-
tical, and they are about 4.5° smaller than in complex 8.
The theoretical calculations show that the ground states of 9
and 10 are singlet and the rhenium electronic configurations are
[core]6s(0.37)5d(5.44) and [core]6s(0.41)5d(5.50) respectively.
The electronegative chlorine ligands have a larger polarization
coefficient factor in the Reꢁhalide bond orbitals than the compar-
ative bromines, and using fewer p electrons. The ReꢁO(3) bond or-
ders of 1.60 and 1.56 in 9 and 10 are in agreement with the sharp
strong bands in the IR spectra. Also, the calculated O(1)–Re–O(3)
angles of 166.1° and 166.0° for 9 and 10 are in exact agreement
with the experimental data. The calculations show that the Re–
Cl(2) bond distance in 9 is longer than the Re–Cl(1) bond length,
and the Re–Br(1) bond distance in 10 is longer than the Re–Br(2)
bond length. In the Re–P(1) bond orbital the rhenium and phos-
phorus atoms use sp1.91d1.96 and sp2.91 hybrid electrons respec-
tively, and the large polarization coefficient (ꢃ0.91) of the
phosphorus shows that electrons are effectively localized on this li-
gand. In 9, the O(1) and O(2) lone pair electrons are delocalized on
Re–O(3) and Re–Cl (1) anti bond orbitals respectively, and in 10 the
P(1), O(1) and O(2) lone pair electrons are delocalized on the Re-
Br(1), Re–O(3) and Re–Br(2) anti bond orbitals respectively. The
presence of more electronegative ligands in 9 compared to 10 en-
ables the rhenium to gain a larger positive charge.
3.7. cis-[ReOX2(bp)(PPh3)] (9 and 10)
The reactions of trans-[ReOX3(PPh3)2] (X = Cl, Br) with a twofold
molar excess of the ligand Hbp in acetonitrile under reflux gave the
green complexes [ReOX2(bp)(PPh3)] [X = Cl(9), Br(10)] as products.
None of these complexes could be isolated with an equimolar ratio
of reactants, even in the presence of triethylamine. Both complexes
are diamagnetic (formally d2) and have low solubilities in polar
solvents like DMSO, acetone and chloroform. In the infrared spec-
tra the asymmetric Re@O stretching frequencies [948 cmꢁ1 (9),
974 cmꢁ1 (10)] appear as sharp strong bands and fall in the region
of 945–965 cmꢁ1 that is normally observed for neutral six-coordi-
nate monooxorhenium(V) complexes with an anionic phenolate
oxygen atom coordinated trans to the Re@O moiety [40,48,49].
Deprotonation of the phenolic OH groups in each complex is sup-
ported by the absence of a band in the 3200–3500 cmꢁ1 region.
The 1H NMR spectrum of 9 consists of a two-proton doublet at
7.69 ppm, an eighteen-proton multiplet in the region 7.51–
4. Conclusion
The reaction of dpk with [Re(CO)5Cl] in methanol led to the
nucleophilic attack of methanol on the bridging ketonic group, to
produce the coordinated monoanionic tridentate ligand dpkꢀOCH3
in the complex fac-[Re(CO)3(dpkꢀOCH3)] (1). In the reaction of
dpk with trans-[ReOBr3(PPh3)2] in acetone, the ketonic group is at-
tacked by water to yield the coordinated monoanionic tridentate
ligand in the complex [ReOBr2(dpkꢀOH)].
7.64 ppm, and
a four-proton multiplet in the region 6.92–
7.01 ppm. The spectrum of 10 integrates for twenty-four protons
in the aromatic region, and the overlap of the signals of the chelate
with those of PPh3 makes assignments difficult.
The reaction of zpy with trans-[ReOX3(PPh3)2] in acetonitrile led
to the reduction of the metal to +III, with no nucleophilic attack on
the ketonic group in the complexes [ReOX2(zpy)(PPh3)]. However,
with methanol as solvent, no reduction of the metal occurred, but
again the zpy had undergone nucleophilic attack by water, and
not methanol as observed in complex 1, in the complexes
[ReOX2(zpyꢀOH)(PPh3)]. With [Re(CO)5Cl] in toluene under nitrogen,
no attack happened on zpy and the complex fac-[Re(CO)3Cl(zpy)]
was isolated.
With Hbp, the rhenium(III) complex cis-[ReBr2(bp)(PPh3)2] was
formed in the reaction of trans-[ReOBr3(PPh3)2] in methanol.
Changing the solvent to acetonitrile, the complexes [ReVOX2(-
bp)(PPh3)] were isolated. This is in contrast to what was observed
with zpy as ligand.
The structures of 9 (Fig. 9) and 10 (Fig. 10) consist of discrete,
monomeric and neutral oxorhenium complexes packed with no
intermolecular contacts shorter than the Van der Waals radii
sum. The coordination geometry around the rhenium is highly dis-
torted octahedral; the ketonic oxygen from the bidentate uninega-
tive ligand O(2) lie on the equatorial plane, along with the two cis
halides X(1) and X(2) and phosphorus P(1) atoms, with the pheno-
late O(2) trans to the O(1) oxo atom. In the two complexes the
O(1)–Re–O(3) axis is non-linear [166.0(6)° and 166.1(8)° in 9 and
10 respectively], and the rhenium atom is displaced from the mean
equatorial plane by 0.073(1) and 0.12(1) Å in 9 and 10 respectively
towards the oxo oxygen atom. The interligand angles in the

N.C. Yumata et al. / Polyhedron 62 (2013) 89–103
[13] A.D. Becke, J. Chem. Phys. 98 (1993) 5648.
103
From an atomistic point of view the CO groups and the oxo oxy-
gen ligands bind stronger to the rhenium rather than the other li-
gands. The phosphorus and carbon atoms bonded to the rhenium
are the only donor atoms to gain positive charges in all the com-
plexes, which are caused by the over-bonding to four atoms and
connecting to electronegative oxygen and the rhenium respec-
tively. The bigger bromine ligands use a larger portion of p elec-
trons than the smaller chlorine to bind to the rhenium. In the
complexes where there is not any significant local bond orbital be-
tween donor atoms and rhenium, the donor atoms’ lone pair elec-
trons are usually delocalized on the front anti bond orbitals.
[14] P.J. Stephens, F.J. Devlin, C.F. Chabalowski, M.J. Frisch, J. Phys. Chem. 98 (1994)
11623.
[15] K.L. Schuchardt, B.T. Didier, T. Elsethagen, L. Sun, V. Gurumoorthi, J. Chase, J. Li,
T.L. Windus, J. Chem. Inf. Model. 47 (2007) 1045.
[16] V. Yeguas, P. Campomanes, R. López, Dalton Trans. 39 (2010) 874.
[17] F. Taherkhani, F.R. Negreiros, G. Parsafar, A. Fortunelli, Chem. Phys. Lett. 498
(2010) 312.
[18] F.R. Negreiros, F. Taherkhani, G. Parsafar, A. Caro, A. Fortunelli, J. Chem. Phys.
137 (2012) 194302.
[19] M. Nahali, F. Gobal, R. Arab, Mol. Phys. 109 (2011) 1797.
[20] A. Arab, F. Gobal, N. Nahali, M. Nahali, J. Cluster Sci. 24 (2013) 273.
[21] C.H. Chang, A.J. Boone, J.B. Rodney, G.J. Nigel, Inorg. Chem. 43 (2004) 458.
[22] V. Tangoulis, C.P. Raptopoulou, S. Paschalidou, A.E. Tsohos, E.G. Balkalbassis, A.
Terzis, S.P. Perlepes, Inorg. Chem. 36 (1977) 5270.
[23] (a) P. Mayer, K.C. Potgieter, T.I.A. Gerber, Polyhedron 29 (2010) 1423;
(b) M. Bakir, J.A.M. McKenzie, J. Electroanal. Chem. 425 (1997) 621.
[24] L. Wei, S.R. Banerjee, M.K. Levadala, J. Babich, J. Zubieta, Inorg. Chim. Acta 357
(2004) 1499.
[25] L. Maria, C. Moura, A. Paulo, I.C. Santos, J. Organomet. Chem. 691 (2006) 4773.
[26] Z.R. Tshentu, T.I.A. Gerber, R. Walmsley, P. Mayer, Polyhedron 27 (2008) 406.
[27] T.I.A. Gerber, P. Mayer, Z.R. Tshentu, J. Coord. Chem. 58 (2004) 1271.
[28] A. Abrahams, T.I.A. Gerber, P. Mayer, J. Coord. Chem. 58 (2005) 1387.
[29] G. Bandoli, A. Dolmella, T.I.A. Gerber, D. Mpinda, J. Perils, J.G.H. du Preez, J.
Coord. Chem. 55 (2000) 823.
Acknowledgments
We would like to thank the Theoretical and High Performance
Computational Research Center of Razi University for providing
the DFT calculation facilities. TIAG is grateful to the Nelson Man-
dela Metropolitan University for financial support.
[30] U. Mazzi, E. Roncari, R. Rossi, V. Bertolasi, O. Traverso, L. Magon, Transition
Met. Chem. 5 (1980) 289.
Appendix A. Supplementary data
[31] F.A. Cotton, S.J. Lippard, Inorg. Chem. 4 (1965) 1621.
[32] T.I.A. Gerber, A. Abrahams, C. Imrie, P. Mayer, J. Coord. Chem. 57 (2004) 1339.
[33] P. Ghosh, A. Pramanik, N. Bag, A. Chakravorty, J. Chem. Soc., Dalton Trans.
(1992) 1883.
[34] E. Marchesi, A. Marchi, L. Marvelli, M. Peruzzini, M. Brugnati, V. Bertolasi,
Inorg. Chim. Acta 358 (2005) 352.
CCDC 935177, 935283, 936087, 935347, 935938, 935933,
936165, 935907, 935891, 935546 contains the supplementary
crystallographic data for compounds 1–10, respectively. These data
can be obtained free of charge via http://www.ccdc.cam.ac.uk/con-
ts/retrieving.html, or from the Cambridge Crystallographic Data
Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223-
336-033; or e-mail: deposit@ccdc.cam.ac.uk.
[35] B. Machura, R. Kruszynski, M. Jaworska, P. Lodowoski, Polyhedron 24 (2005)
701.
[36] M. Siervert, R. Dienelt, H. Bock, Acta Crystallogr., Sect. C 54 (1998) 674.
[37] B. Machura, R. Kruszynski, J. Organomet. Chem. 692 (2007) 4161.
[38] D. Orth, J. Barrerra, M. Sabat, W.D. Harman, Inorg. Chem. 33 (1994) 3026.
[39] S.R. Fletcher, A.C. Skapski, J. Chem. Soc., Dalton Trans. (1972) 1073.
[40] B. Machura, R. Kruszynski, J. Mrozin´ ski, J. Kusz, Polyhedron 27 (2008) 1739.
[41] A.L. Wilds, Org. React. (1944) 2.
[42] T.I.A. Gerber, D. Luzipo, P. Mayer, Inorg. Chim. Acta 357 (2004) 429.
[43] X. Chen, F.J. Femina, J.W. Babich, J. Zubieta, Inorg. Chim. Acta 308 (2002) 80.
and references therein.
[44] T.I.A. Gerber, H.J. Kemp, J.G.H. du Preez, G. Bandoli, A. Dolmella, Inorg. Chim.
Acta 202 (1992) 191.
[45] J. Granifo, Polyhedron 1061 (1999) 18.
[46] B. Machura, A. Switlicka, I. Nawrot, K. Michalik, Inorg. Chem. Commun. 13
(2010) 1317.
[47] C. Melian, C. Kremer, K. Suescun, A. Mombru, R. Mariezcurrena, E. Kremer,
Inorg. Chim. Acta 306 (2000) 70.
[48] I.D. Brown, C.J.L. Lock, C. Wan, Can. J. Chem. 52 (1974) 1704.
[49] B. Machura, M. Wolff, J. Mrozinski, R. Kruszynski, J. Kusz, Polyhedron 28 (2009)
2377.
[50] H. Pietzch, H. Spies, P. Leibnitz, G. Reck, Polyhedron 1849 (1995) 14.
[51] U. Witten, J. Strahle, U. Abram, Z. Anorg. Allg. Chem. 621 (1995) 1338.
[52] T.I.A. Gerber, D. Luzipo, P. Mayer, J. Coord. Chem. 56 (2003) 1549.
[53] T.I.A. Gerber, D. Luzipo, P. Mayer, J. Coord. Chem. 58 (2004) 1505.
[54] W.A. Herrmann, M.U. Rauch, G.R.J. Artus, Inorg. Chem. 1996 (1988) 35.
[55] H.J. Banbery, F. McQuillan, T.A. Hamor, C.J. Jones, J.A. McCleverty, J. Chem. Soc.,
Dalton Trans. (1989) 1405.
References
[1] (a) T.I.A. Gerber, H.J. Kemp, J.G.H. du Preez, G. Bandoli, J. Coord. Chem. 28
(1993) 329;
(b) M. Bakir, Acta Crystallogr., Sect. C 58 (2002) m74;
(c) C. Pejo, H. Pardo, A. Mombrú, M.F. Cerdá, J.S. Gancheff, R. Chiozzone, R.
González, Inorg. Chim. Acta 376 (2011) 105.
[2] J.G. Malecki, R. Kruszynki, Polyhedron 26 (2007) 2686.
[3] D.L. Reger, J.R. Gardinier, M.D. Smith, P.J. Pellechia, Inorg. Chem. 42 (2003) 482.
[4] Y. Fuchita, H. Ieta, Y. Tsunemune, J. Kinoshita-Nagaoka, H. Kawano, J. Chem.
Soc., Dalton Trans. (1998) 791.
[5] (a) B. Machura, J. Mrozin´ ski, R. Kruszynski, J. Kusz, Polyhedron 28 (2009)
2821;
´
(b) B. Machura, M. Wolff, A. Switlicka, R. Kruszynski, J. Kusz, Inorg. Chem.
Commun. 12 (2009) 789.
[6] M. Bakir, J.A.M. McKenzie, J. Chem. Soc., Dalton Trans. (1997) 3571.
[7] (a) B. Machura, J. Mrozin´ ski, J. Kusz, Inorg. Chem. Commun. 13 (2010) 231;
´
(b) B. Machura, J. Miłek, R. Kruszynski, J. Kusz, J. Mrozinski, Polyhedron 27
(2008) 1262.
[8] N.P. Johnson, C.J.L. Lock, G. Wilkinson, Inorg. Synth. 9 (1967) 145.
[9] G.M. Sheldrick, SADABS, University of Göttingen, Germany, 1996.
[10] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
[11] A.A. Granovsky, Firefly, version 8.0.0. <http://classic.chem.msu.su/gran/firefly/
index.html>.
[12] E.D. Glendening, J.K. Badenhoop, A.E. Reed, J.E. Carpenter, J.A. Bohmann, C.M.
Morales, F. Weinhold, NBO 5.0, Theoretical Chemistry Institute, University of
Wisconsin, Madison, 2001.
[56] A. Abrahams, G. Bandoli, S. Gatto, T.I.A. Gerber, J.G.H. du Preez, J. Coord. Chem.
42 (1997) 303.