Synthesis and characterization of carbonyl group-6-metal derivatives with ligand N,N-Bis(diphenylphosphino)naphthalen-1-amine (=N-(Diphenylphosphino)-N- naphthalen-1-yl-P,P-diphenylphosphinous Amide). molecular structure of cis-tetracarbonyl[N-(diphenylphosphino-κP)-N-naphthalen-1-yl-P,P-diphenylphosphinous amide-κP]molybdenum (cis-[Mo(CO)4{C

Article abstract of DOI:10.1002/hlca.201200315

The reaction of N,N-bis(diphenylphosphino)naphthalen-1-amine (1) with [M(CO)₆] (M=Cr, Mo, W; 1: 1 molar ratio) afforded cis-[M(CO) ₄(1)] 2 (M=Cr), 3 (M=Mo), and 4 (M=W). Compounds 2-4 were identified and characterized by elemental analysis and multinuclear NMR (¹H-, ¹³C-, and ³¹P-NMR) and IR spectroscopy. A crystal-structure determination of complex 3 was carried out. Copyright

Full text of DOI:10.1002/hlca.201200315

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Helvetica Chimica Acta – Vol. 96 (2013)
Synthesis and Characterization of Carbonyl Group-6-Metal Derivatives with
Ligand N,N-Bis(diphenylphosphino)naphthalen-1-amine (¼ N-
(Diphenylphosphino)-N-naphthalen-1-yl-P,P-diphenylphosphinous Amide).
Molecular Structure of cis-Tetracarbonyl[N-(diphenylphosphino-kP)-N-
naphthalen-1-yl-P,P-diphenylphosphinous amide-kP]molybdenum (cis-
[Mo(CO)4{C10H7-1-N(PPh2)2}])
by Harbi Tomah Al-Masri*a), Beshir M. Mohameda), Ziad Moussab), and Mohamed H. Alkordic)
a) Faculty of Applied Sciences, Department of Applied Chemistry, Taibah University, Madinah 1343,
K.S.A. (e-mail: harbialmasri@yahoo.com)
b) Faculty of Science, Department of Chemistry, Taibah University, Madinah 344, K.S.A.
c) King Abdullah University of Science and Technology, Jeddah, Thuwal 23955 – 6900, K.S.A.
The reaction of N,N-bis(diphenylphosphino)naphthalen-1-amine (1) with [M(CO)6] (M ¼ Cr, Mo,
W; 1:1 molar ratio) afforded cis-[M(CO)4(1)] 2 (M ¼ Cr), 3 (M ¼ Mo), and 4 (M ¼ W). Compounds 2 –
4 were identified and characterized by elemental analysis and multinuclear NMR (1H-, 13C-, and 31P-
NMR) and IR spectroscopy. A crystal-structure determination of complex 3 was carried out.
Introduction. – In an extension of our interest and the interest of others [1] on the
synthesis and solid-state structures of phosphorus(III) ligands containing direct PꢀN
bonds and their derivatives [2][3], as these are interesting in the field of medicinal [4 –
7] and catalytic chemistry [8 – 10], as well as herbicidal, neuroactive, and antimicrobial
agents [11 – 13], we herein report the synthesis and spectroscopic properties of group-6-
metal carbonyl complexes 2 – 4 and the crystal structure of 3.
Experimental. – General. All experiments were carried out under purified dry N2 by using standard
Schlenk and vacuum-line techniques. Solvents were dried and freshly distilled under N2 [14]. The
chemicals [M(CO)6] (M ¼ Cr, Mo, and W) were used as purchased. N,N-Bis(diphenylphosphino)naph-
thalen-1-amine (¼ N-(diphenylphosphino)-N-napthalen-1-yl-P,P-diphenylphosphinous amide; 1) was
prepared according to the method described previously [3]. M.p.: Gallenkamp apparatus; open
capillaries. IR spectra: Perkin-Elmer-2000 FT-IR spectrometer; range 4000 – 400 cmꢀ1; KBr disks; in
cmꢀ1. NMR Spectra: Bruker-Avance-DRX-400 spectrometer; at 400.17 (1H), 100.63 (13C), and
161.98 MHz (31P) and 258; SiMe4 for 1H and 85% H3PO4 for 31P as external standards; d in ppm.
Microanalyses: Flash-2000 elemental analyzer.
cis-[N,N-Bis(diphenylphosino-kP)naphthalen-1-amine]tertracarbonylchromium(0) (¼cis-Tetracar-
bonyl[N-(diphenylphosphino-kP)-N-naphthalen-1-yl-P,P-diphenylphosphinous amide-kP]chromium;
2). Ligand 1 (2.00 g, 3.91 mmol) was added to a soln. of [Cr(CO)6] (0.86 g, 3.91 mmol) in toluene
(80 ml), and the mixture was heated under reflux for 36 h. The soln. was filtered, the solvent evaporated,
and the dark yellow solid recrystallized from CH2Cl2/hexane 1:1 (v/v) at 258: 2 (70%). Yellow crystals.
M.p. 180 – 1838. IR (selected bands): 1888s (br.), 1918s, 2006s (CꢁO). 1H-NMR (CDCl3): 6.40 – 7.72 (m,
C10H7, 4 Ph). 13C-NMR (CDCl3): 124.80, 125.17, 125.61, 125.94, 127.09, 127.92, 128.61, 129.59, 130.46,
131.32, 132.56, 134.07, 135.44, 138.75 (C10H7 and 4 Ph); 221.24 (CꢁOeq); 228.17 (CꢁOax). 31P-NMR
(CDCl3): 117.41 (s, 2 P). Anal. calcd. for C38H27CrNO4P2: C 67.56, H 4.03, N 2.07; found: C 67.58, H 4.05,
N 2.04.
ꢀ 2013 Verlag Helvetica Chimica Acta AG, Zꢁrich

Helvetica Chimica Acta – Vol. 96 (2013)
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cis-[N,N-Bis(diphenylphosino-kP)naphthalen-1-amine]tertracarbonylmolybdenum(0) (¼cis-Tetra-
carbonyl[N-(diphenylphosphino-kP)-N-naphthalen-1-yl-P,P-diphenylphosphinous amide-kP]molybde-
num; 3). A mixture of ligand 1 (0.40 g, 0.76 mmol) and [Mo(CO)6] (0.20 g, 0.76 mmol) in benzene
(40 ml) was refluxed for 12 h (!dark brown soln.). The solvent was evaporated, the product extracted
into hexane (40 ml), and the extract cooled to 48: 3 (80%). Yellow crystals. M.p. 235 – 2388. IR (selected
bands): 1907s (br.), 1924s, 2023s (CꢁO). 1H-NMR (CDCl3): 6.42 – 7.68 (m, C10H7 and 4 Ph). 13C-NMR
(CDCl3): 124.69, 125.19, 125.51, 126.98, 127.21, 127.51, 128.23, 128.60, 130.17, 130.92, 131.37, 132.51, 133.92,
139.56 (C10H7, 4 Ph); 212.37 (CꢁOeq); 218.37 (CꢁOax).31P-NMR (CDCl3): 93.43 (s, 2 P). Anal. calc. for
C38H27MoNO4P2: C 63.43, H 3.78, N 1.95; found: C 63.40, H 3.73, N 1.93.
cis-[N,N-Bis(diphenylphosino-kP)naphthalen-1-amine]tetracarbonyltungsten(0) (¼cis-Tetracarbo-
nyl[N-(diphenylphosphino-kP)-N-naphthalen-1-yl-P,P-diphenylphosphinous amide-kP]tungsten; 4). As
described for 2, with [W(CO)6] (1.38 g, 3.91 mmol) instead of [Cr(CO)6]: 4 (60%). Light yellow solid.
M.p. 160 – 1638. IR (selected bands): 1889s (br.), 1910s, 2016s (CꢁO). 1H-NMR (CDCl3): 6.42 – 7.72 (m,
27 H, C10H7, 4 Ph). 13C-NMR (CDCl3): 124.52, 125.13, 125.98, 126.70, 127.12, 127.30, 128.10, 128.58,
130.16, 130.91, 131.34, 132.44, 133.91, 139.54 (C10H7, 4 Ph); 203.60 (CꢁOeq); 210.65 (CꢁOax).31P-NMR
(CDCl3): 70.19 (s, 2 P). Anal. calc. for C38H27NO4P2W: C 56.53, H 3.37, N 1.73; found: C 56.52, H 3.38, N
1.75.
Data Collection and Structure Determination of 3. Crystallographic data are given in Table 1. Data
were collected with a Bruker-AXS-Smart-Apex-CCD diffractometer; l(CuKa) ¼ 1.54178 ꢂ. All observed
reflections were used for the determination of the unit-cell parameters. Indexing was performed with
SMART [15]. Frames were integrated with the SAINT software package [16]. Absorption correction was
performed by the multi-scan method implemented in SADABS [17]. Crystal structures were solved by
using SHELXS-97 and refined by using SHELXL-97 contained in the SHELXTL and WinGX-1.70.01
program packages [18]. All non-H-atoms were refined with anisotropic displacement parameters. All H-
atoms bonded to C-atoms were placed in geometrically optimized positions and refined with an isotropic
displacement parameter relative to the attached atoms. CCDC-876277 conatins the supplementary
crystallographic data (excluding structure factors) for the structure of 3. These data can be obtained free
of charge via http://www.ccdc.cam.ac.uk/data_request/cif.
Table 1. Crystal Data and Structure Refinement of 3
Formula
Mr
Temp. [K]
Crystal system
Space group
a [ꢂ]
b [ꢂ]
c [ꢂ]
a [8]
b [8]
C38H27MoNO4P2
719.49
100
triclinic
P-1
11.1442(5)
16.7516(6)
17.5177(7)
89.392(2)
82.816(3)
89.927(3)
3244.4(2)
Z
4
1calcd [Mg mꢀ3
F(000)
]
1.473
1464
4.584
13393
8045
0.0304
829
0.0356
0.0890
0.524
ꢀ 0.698
Abs. coeff. [mmꢀ1
No. of refl. collected
No. of independant refl.
Rint
No. of parameters
R1 (I > 2s(I))
]
wR2 (all data)
g [8]
V [ꢂ3]
D1max [e · ꢂꢀ3
]
D1min [e · ꢂꢀ3
]
Results and Discussion. – Synthesis. The Scheme summarizes the synthesis of 2 – 4.
The reaction of ligand 1 with 1 equiv. of [M(CO)6] (M ¼ Cr, or Mo) under reflux in
toluene afforded cis-[Cr(CO)4(1)] (2) and cis-[W(CO)4(1)] (4), respectively. More-
over, reaction of ligand 1 with 1 equiv. of [Mo(CO)6] under reflux in benzene gave cis-
[Mo(CO)4(1)] (3). Compounds 2 – 4 are moderately stable to air and moisture.

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Helvetica Chimica Acta – Vol. 96 (2013)
Scheme. Preparation of 2 – 4
Compounds 2 – 4 were isolated from the reaction solution and fully characterized by
elemental analysis, IR and multinuclear NMR spectroscopy. Furthermore, the
molecular structure of 3 was elucidated by single crystal X-ray diffraction.
1H-, 13C-, and 31P-NMR Spectra. Due to the presence of naphthalenyl and phenyl
1
groups and coupling with 31P, the aromatic region in the H-, and 13C-NMR spectra of
2 – 4 was complex and difficult to fully interpret [19]. The 1H-NMR spectra of 2 – 4 had
the expected pattern characteristic for the organic ligand 1; the resonances corre-
sponding to the phenyl and naphthalenyl protons displayed overlapped m in the region
d(H) 6.40 – 7.72.
The 13C-NMR spectra of the carbonyl ligands of 2 – 4 showed two signals due to the
carbonyl ligands oriented trans and cis to the P-atoms. The d(C) of the carbonyl ligands
decreased in the order of Cr> Mo > W coordination, in parallel with the increasing
number of electrons in the central metal atom [20].
The 31P-NMR signals of 2 – 4 appeared as s signals at d(P) 117.41 (2), 93.43 (3), and
70.19 (4), indicating two equivalent P-atoms. The d(P) increased upon coordination of
ligand 1 (d(P) 63.46) with the metal center, the shift being ca. 54 ppm for 2, ca. 30 ppm
of 3 and ca. 7 ppm for 4, and the d(P) decreased in the order of Cr> Mo > W
coordination, in agreement with the observation that such a d(P) should decrease as
one descends in a given periodic group [21].
IR Spectra and Yields. The IR spectra of 2 – 4 showed bands in the range 1888 –
2023 cmꢀ1 due to the ˜n(CꢁO) stretching typical for cis-[M(CO)4L2] complexes [22].
The carbonyl frequencies of the complexes 2 – 4 were very near those of closely related
complexes with ligands in which the P-atom is bonded to C-atoms only. The absence of
any marked effect shows that the replacement of CH or CHR by NR does not greatly
change the ability of the P-atoms to accept electrons from the metal [23]. Complexes
2 – 4 were obtained in 60 – 80% yield.
Molecular Structure of 3. Crystals of 3 were obtained as described in the Exper.
¯
Part. Complex 3 crystallized in the triclinic space group P1. Selected interatomic
distances and angles are collected in Table 2, and the molecular structure is depicted in
the Figure.
The X-ray structure of 3 contains two crystallographically independent molecules,
3a and 3b (Fig.), in the asymmetric unit. These differ in the orientation of the
naphthalenyl group. The crystal structure of 3 shows a distorted octahedral environ-
ment around the Mo-atom surrounded by four terminal CO ligands and two P-centers.

Helvetica Chimica Acta – Vol. 96 (2013)
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Table 2. Selected Bond Lengths [ꢂ] and Bond Angles [8] of 3a and 3b
3a
3b
Mo1ꢀC(1)
2.039(5)
1.990(4)
2.001(5)
2.034(5)
2.5036(9)
2.4925(10)
1.723(3)
1.710(3)
1.817(4)
1.832(4)
1.822(4)
1.825(4)
1.459(4)
Mo2ꢀC(39)
2.048(5)
Mo(1)ꢀC(2)
Mo(2)ꢀC(40)
2.001(4)
2.016(5)
2.020(5)
2.4755(10)
2.4898(9)
1.715(3)
1.725(3)
1.830(4)
1.818(4)
1.814(4)
1.829(4)
1.446(4)
Mo(1)ꢀC(3)
Mo(2)ꢀC(41)
Mo(1)ꢀC(4)
Mo(2)ꢀC(42)
Mo(1)ꢀP(1)
Mo(2)ꢀP(3)
Mo(1)ꢀP(2)
Mo(2)ꢀP(4)
P(1)ꢀN(1)
P(3)ꢀN(2)
P(2)ꢀN(1)
P(4)ꢀN(2)
P(1)ꢀC(23)
P(3)ꢀC(43)
P(1)ꢀC(17)
P(3)ꢀC(49)
P(2)ꢀC(11)
P(4)ꢀC(65)
P(2)ꢀC(5)
P(4)ꢀC(71)
N(1)ꢀC(29)
N(2)ꢀC(55)
S angles at N(1)
P(1)ꢀMo(1)ꢀP(2)
P(1)ꢀMo(1)ꢀC(1)
P(1)ꢀMo(1)ꢀC(2)
P(1)ꢀMo(1)ꢀC(3)
P(1)ꢀMo(1)ꢀC(4)
P(2)ꢀMo(1)ꢀC(1)
P(2)ꢀMo(1)ꢀC(2)
P(2)ꢀMo(1)ꢀC(3)
P(2)ꢀMo(1)ꢀC(4)
P(1)ꢀN(1)ꢀP(2)
N(1)ꢀP(1)ꢀMo1
N(1)ꢀP(2)ꢀMo1
N(1)ꢀP(1)ꢀC(17)
N(1)ꢀP(1)ꢀC(23)
N(1)ꢀP(2)ꢀC(5)
N(1)ꢀP(2)ꢀC(11)
C(17)ꢀP(1)ꢀC(23)
C(5)ꢀP(2)ꢀC(11)
P(2)ꢀMo(1)ꢀP(1)ꢀN(1)
359.93
S angles at N(2)
P(3)ꢀMo(2)ꢀP(4)
P(3)ꢀMo(2)ꢀC(39)
P(3)ꢀMo(2)ꢀC(40)
P(3)ꢀMo(2)ꢀC(41)
P(3)ꢀMo(2)ꢀC(42)
P(4)ꢀMo(2)ꢀC(39)
P(4)ꢀMo(2)ꢀC(40)
P(4)ꢀMo(2)ꢀC(41)
P(4)ꢀMo(2)ꢀC(42)
P(2)ꢀN(2)ꢀP(4)
N(2)ꢀP(3)ꢀMo2
N(2)ꢀP(4)ꢀMo2
N(2)ꢀP(3)ꢀC(43)
N(2)ꢀP(3)ꢀC(49)
N(2)ꢀP(4)ꢀC(65)
N(2)ꢀP(4)ꢀC(71)
C(43)ꢀP(3)ꢀC(49)
C(65)ꢀP(4)ꢀC(71)
P(3)ꢀMo(2)ꢀP(4)ꢀN(2)
359.93
65.94(3)
91.96(10)
165.15(12)
98.63(10)
93.18(10)
92.77(12)
99.23(12)
164.46(11)
93.39(11)
104.73(16)
93.62(10)
94.32(11)
103.61(16)
106.24(16)
108.39(16)
107.06(16)
104.72(17)
101.62(18)
7.6(1)
66.14(3)
92.19(11)
98.82(12)
165.76(11)
87.55(11)
89.96(9)
164.87(12)
100.00(10)
91.41(10)
103.93(15)
94.70(11)
93.94(10)
107.76(16)
109.09(15)
107.42(16)
107.81(17)
100.38(17)
102.22(17)
7.4(1)
The ability of compound 1 to act as a bidentate P,P’-chelating ligand to the Mo-
atom results in the formation of a four-membered metallacycle, i.e., PꢀMoꢀPꢀN, that is
nearly planar with a torsion angle PꢀMoꢀPꢀN of 7.6(1)8 in 3a and 7.4(1)8 in 3b with a
smaller PꢀMoꢀP bite angle (65.94(3)8 (3a) and 66.14(3)8 (3b)) and larger PꢀNꢀP
bond angle (104.73(16)8 (3a) and 103.93(15)8 (3b)).
A comparison of the PꢀMoꢀP and PꢀNꢀP bond angles of 3a and 3b (Table 2) with
those of the four-membered ring of the similar cis-chelated tetracarbonylmolybde-
num(0) complexes 5 – 9, tetracarbonylchromium(0) complexes 10 – 12, and tetracarbo-
nyltungsten(0) complexes 13 and 14 (Table 3) showed that the PꢀMoꢀP bite angles in
3a and 3b are slightly larger than those in 5 – 9, 13, and 14 and smaller than those in 10 –
12. The PꢀNꢀP bond angles in 3a and 3b are larger than those in 5 – 8, 10 – 12, and 13
and smaller than those in 9 and 14. The PꢀMꢀP bite angles in cis-chelated
tetracarbonylchromium(0) complexes 10 – 12 are in average 67.988, being about 28

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Helvetica Chimica Acta – Vol. 96 (2013)
Figure. Molecular structure of the two independent molecules a) 3a and b) 3b. H-Atoms are omitted for
clarity.

Helvetica Chimica Acta – Vol. 96 (2013)
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Helvetica Chimica Acta – Vol. 96 (2013)
wider than the average value in the cis-chelated tetracarbonylmolybdenum(0)
complexes 3a and 3b (averaged 66.048).
The PꢀMoꢀP bite angles in 3a and 3b are relatively close to each other and
significantly lower than the ideal 908 in a regular square-planar geometry. Apparently,
the presence of the naphthalenyl and phenyl groups decreases the PꢀMoꢀP bite angle,
presumably as a result of steric reasons, as the relatively bulky naphthalenyl and phenyl
groups occupy much of the lateral space surrounding the PꢀMoꢀPꢀN ring, which leads
to distorted square-planar coordination geometry around the Mo-atom with the
phosphinoamine moieties coordinated in a mutual cis-fashion, in agreement with the
spectroscopic data. The PꢀNꢀP bond angles (104.73(16)8 (3a) and 103.93(15)8 (3b))
are significantly smaller than those in the free diphosphinoamine ligands [24][36] due
to the formation of a strained four-membered chelate ring.
The napthalenyl moietes in 3a and 3b are almost planar and virtually perpendicular
to the PꢀMoꢀPꢀN planes. A planar environment would be expected for the three-
coordinate N-atoms in 3a and 3b, and the sums of bond angles in 3a and 3b are indeed
close to 3608 (Table 2).
The PꢀMoꢀC(trans) angles of 3a (164.46(11)8 and 165.15(12)8) and 3b (164.87(12)8
and 165.76(11)8) differ significantly from 1808. The variations of the trans angles (0.69
(3a) and 0.898 (3b)) are smaller than those of 5 (162.39(13)8 vs. 165.83(15)8), 6
(162.74(7)8 vs. 164.62(7)8), and 9 (164.70(1) vs. 169.00(1)8).
The average PꢀN bond distances in 3a (1.717 ꢂ) and 3b (1.720 ꢂ) are essentially the
same and within the expected value range in comparison to the similar cis-chelated
tetracarbonyl complexes 5 – 14 (Table 3), but they are shorter than the sum of the
Pauling covalent radii (1.77 ꢂ), as expected due to PꢀN p-bonding. Consistent with
this, the N-atom is nearly planar as evidenced by the sum of angles about the N-atom
(359.938 (3a) and 359.938 (3b)). Also, the average PꢀN bond distances in 3a and 3b are
slightly shorter than those in the free diphosphinoamine ligands [24][36], which clearly
indicate an enhancement of p-bonding in the PꢀN unit.
The MoꢀP bond distances are 2.4925(10) and 2.5036(9) ꢂ in 3a and 2.4755(10) and
2.4898(9) ꢂ in 3b. The two MoꢀP bond distances in 3a or 3b are relatively different.
Apparently, the large steric constraints in the ligand prevent an appropriate orbital
overlap when the two MoꢀP bonds are equal and coplanar with the Mo(CO)4 moiety.
The average MoꢀP bond distances in 3a (2.498 ꢂ) and 3b (2.483 ꢂ) are within the
expected value range in comparison to similar cis-chelated tetracarbonylmolybde-
num(0) complexes 5 – 9 (averaged 2.488 ꢂ), slightly longer than those in tetracarbo-
nyltungsten(0) complexes 13 and 14 (averaged 2.463 ꢂ), and shorter than those in
tetracarbonylchromium(0) complexes 10 – 12 (averaged 2.356 ꢂ) due to the small
atomic radius of chromium.
The MoꢀC bond distances are 1.990(4) – 2.039(5) ꢂ for 3a and 2.001(4) – 2.048(5) ꢂ
for 3b. The shorter MoꢀC bond is trans to the longer MoꢀP bond, which is in agreement
with a trans effect of the donors (P < CꢁO).
It is interesting to note that the MoꢀP bond lengths in 15 and 16 (Table 3) are larger
than those in 3a and 3b, which can be explained by the increased steric crowding caused
by the two ligands in cis positions, while the MoꢀP bond lengths in 17 are shorter than
those in both 3a and 3b, probably due to relative trans influences of the phosphino and
carbonyl ligands.

Helvetica Chimica Acta – Vol. 96 (2013)
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The PꢀMoꢀP bite angles of 3a and 3b are much smaller than the PꢀMoꢀP of the
seven-membered ring in 18 (Table 3). We see that the PꢀMꢀP bite angle is dependent
only on the ligand and the type of transition metal. The aromatic rings in 3a and 3b, as
expected, have usual bond lengths and angles.
Conclusions. – We have shown the successful synthesis of group-6 transition metal
tetracarbonyl complexes 2 – 4 of ligand 1. All these new complexes were characterized
by elemental analysis, IR, and multinuclear NMR spectroscopy. The ligand showed a
clear tendency to coordinate in a cis-fashion to these transition metals, as indicated by
31P-NMR spectroscopy. For the complex cis-[Mo(CO)4(1)] (3), the molecular structure
was determined.
We would like to thank the Deanship of Scientific Research at the Taibah University for funding
(Res. No. 967/ 433).
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Received June 21, 2012