Synthesis of monomeric and polymeric alkali and alkaline earth metal complexes using a phosphinoselenoic amide ligand in metal coordination sphere

Article abstract of DOI:10.1007/s12039-014-0711-z

We report the monomeric complexes of magnesium and calcium of composition [M(THF)_n{η ²-Ph₂P(Se)N(CMe₃)}₂] [M = Mg (3), n = 1 and M = Ca (4), n = 2)] and polymeric complexes of potassium and barium of composition [K(THF)₂{Ph₂P(Se)N(CMe₃)}]_n (2) and [K(THF)Ba{Ph₂P(Se)N(CMe₃)}₃]_n(5) respectively. The potassium complex 2 was readily prepared by the reaction of potassium bis(trimethylsilyl)amide with phosphinoselenoic amide ligand (1) at ambient temperature. The calcium complex 4 was prepared by two synthetic routes: in the first method, commonly known as salt metathesis reaction, the potassium complex 2 was made to react with alkaline earth metal diiodide at room temperature to afford the corresponding calcium complex. The metal bis(trimethylsilyl)amides were made to react with protic ligand 1in the second method to eliminate the volatile bis(trimethyl)silyl amine. The magnesium complex 3and barium complex 5 were prepared only through the first method. Solid-state structures of all the new complexes were established by single crystal X-ray diffraction analysis. The smaller ionic radii of Mg²⁺ (0.72 ?) and Ca²⁺ (0.99 ?) ions form the monomeric complex, whereas the larger ions K⁺ (1.38 ?) and Ba²⁺ (1.35 ?) were found to form one-dimensional polymeric complexes with monoanionic ligand 1. Compound 2 serves an example of magnesium complex with a Mg-Se direct bond.

Full text of DOI:10.1007/s12039-014-0711-z

c
J. Chem. Sci. Vol. 126, No. 5, September 2014, pp. 1463–1475. ꢀ Indian Academy of Sciences.
Synthesis of monomeric and polymeric alkali and alkaline earth
metal complexes using a phosphinoselenoic amide ligand in metal
coordination sphere
JAYEETA BHATTACHARJEE, RAVI K KOTTALANKA, HARINATH ADIMULAM
and TARUN K PANDA∗
Department of Chemistry, Indian Institute of Technology Hyderabad, Ordnance Factory Estate,
Yeddumailaram 502 205, Telangana, India
e-mail: tpanda@iith.ac.in
MS received 17 March 2014; revised 24 April 2014; accepted 14 May 2014
Abstract. We report the monomeric complexes of magnesium and calcium of composition [M(THF)n{η2-
Ph2P(Se)N(CMe3)}2] [M = Mg (3), n = 1 and M = Ca (4), n = 2)] and polymeric complexes of potassium and
barium of composition [K(THF)2{Ph2P(Se)N(CMe3)}]n (2) and [K(THF)Ba{Ph2P(Se)N(CMe3)}3]n(5) respec-
tively. The potassium complex 2 was readily prepared by the reaction of potassium bis(trimethylsilyl)amide
with phosphinoselenoic amide ligand (1) at ambient temperature. The calcium complex 4 was prepared by
two synthetic routes: in the first method, commonly known as salt metathesis reaction, the potassium com-
plex 2 was made to react with alkaline earth metal diiodide at room temperature to afford the corresponding
calcium complex. The metal bis(trimethylsilyl)amides were made to react with protic ligand 1 in the second
method to eliminate the volatile bis(trimethyl)silyl amine. The magnesium complex 3 and barium complex 5
were prepared only through the first method. Solid-state structures of all the new complexes were established
by single crystal X-ray diffraction analysis. The smaller ionic radii of Mg2+ (0.72 Å) and Ca2+ (0.99 Å) ions
form the monomeric complex, whereas the larger ions K+ (1.38 Å) and Ba2+ (1.35Å) were found to form one-
dimensional polymeric complexes with monoanionic ligand 1. Compound 2 serves an example of magnesium
complex with a Mg–Se direct bond.
Keywords. Magnesium; calcium; barium; potassium; phosphorus; selenium.
1. Introduction
the catalytic potential of these elements still requires
substantial advances in understanding their basic coor-
dination and organometallic chemistry. To stabilise
these extremely oxophilic and electropositive metals,
a wide variety of nitrogen-based ancillary ligands,
such as tris(pyrazolyl)borates,1 aminotroponiminates,11
β-diketiminates,12 –14 iminopyrroles15–17 and 1,4-diaza-
1,3-butadiene18 ,19 have been introduced to prepare
well-defined alkaline earth metal complexes, reveal-
ing that the catalytic activity and selectivity of the
alkaline earth metal complexes can be controlled via
the well-defined nitrogen-based ligand architecture.
Another important application of alkaline earth metal
chalcogenolates is in high temperature superconductors
and ferroelectrics. In particular, alkaline earth metal
oxide compounds are used as suitable precursors.20
Much less attention has been paid to the alkaline earth
metal thiolates and selenates, although many heav-
ier chalcogenates are known as potential dopants for
chalcogen-based semiconductors.21 Chelating ligands
with selenium as the donor atom to stabilise heavier
alkaline earth metal complexes are rare. Over the
To date, the chemistry of alkaline earth metals is less
developed when compared to magnesium chemistry,
and the former are often termed ‘sleeping beauties’.1,2
Among the alkaline earth metals (Mg, Ca, Sr and Ba),
magnesium is exceptional; it was studied extensively by
Grignard, who established that the organomagnesium
reagent plays a significant role in synthetic inorganic
and organic chemistry.3,4 In recent years, the chem-
istry of heavier alkaline earth metals has been well
established and complexes of the alkaline earth metals
are employed in various catalytic applications such as
ring-opening polymerisation of various cyclic esters,5,6
polymerisation of styrene and dienes,7–9 and hydroami-
nation and hydrophosphination reactions of alkenes and
alkynes.10 Exploration of the structure and reactivity of
alkaline earth metal species is one of the most important
steps towards the design and development of efficient
homogeneous catalysts. However, full realisation of
∗For correspondence
1463

1464
Jayeeta Bhattacharjee et al.
vacuum (10−4torr) line, or in an argon-filled M. Braun
glove box. THF was pre-dried over a sodium wire and
distilled under nitrogen from sodium and benzophe-
noneketyl prior to use. Hydrocarbon solvents (toluene
and n-pentane) were distilled under nitrogen from
LiAlH4 and stored in the glove box. 1H NMR (400
MHz), 13C{1H} (100 MHz) and 31P{1H} NMR (161.9
MHz) spectra were recorded on a BRUKER AVANCE
III-400 spectrometer. BRUKER ALPHA FT-IR was
used for FT-IR measurement. Elemental analyses were
performed on a BRUKER EURO EA at the Indian
Institute of Technology Hyderabad. [KN(SiMe3)2],38
[Ca{N(SiMe3)2}2(THF)2]39,40 and N-tert-butyl-1,1-
diphenylphosphinamine [Ph2PNHCMe3]41 were pre-
pared according to published procedures. MI2 (M =
Mg, Ca, Ba), were purchased from Sigma Aldrich and
used without further purification.
last few years very few alkaline earth selenium-based
complexes have been reported and structurally char-
acterised. Among these are [Mg(SeMes”)2(THF)2]
(Mes” = 2,4,6-tBu3C6H2),22 [M(SeMes)2(THF)4] (M =
Ca, Sr, Ba),23–25 [Ca{CH(Py)(Se)PPh2}2(THF2]2 (Py =
pyridine)26 and [(TMEDA)2Ca(SeSi(SiMe3)3)].27 Full
structural characterisation of strontium selenides is
even more scarce.23,28 A complex with a barium–
selenium bond is limited as structurally authentica-
ted examples are mostly restricted to various sul-
phur derivatives: [{(H2O)2Ba(tmtH2)2}n] (tmt = 2,4,
6-trimarcaptotriazine, S3C3N3),29 [([18]crown-6)Ba
(hmpa)SMes*][SMes*](Mes* = 2,4,6-tBu3C6H2),30
[Ba(hmpa)3{Na-PhNNNNC(S)}2],31 [Ba-(hmpa)3(C
(=S)NOPh2]32 and [Ba(SCMe3)2,33 [Ba(tmeda)2(SeSi
(SiMe3)3)2],27 with only a few more examples being
reported. Ruhlandt-Senge and colleagues reported
barium selenoates like [Ba(THF)4(SeMes*)2], [([27]
crown-6)Ba(hmpa)2(SMes*)2], [Ba(Py)3(THF)(SeTrip)
2}2] (Trip = 2,4,6 iPr3C6H2), and [Ba([18]crown-
6)(SeTrip)2];34 however the vast potential of this field of
chemistry is yet to be developed. Recently, we reported
heavier alkaline earth metal selenium containing com-
plexes [M(THF)2{ Ph2P(Se)N(CHPh2)}2] (M = Ca, Sr,
Ba) to enrich the field of heavier group 2 metal seleno
complexes.35 In that work we showed that phosphinose-
lenoic amide ligands are capable of stabilising heavier
alkaline earth metals through the formation of a sele-
nium metal bond. In continuation of our focus on alka-
line earth metal selenide complexes, we now explore
the ligand’s role in the nuclearity of metal complexes.
Other research groups also reported various main group
2.2 Synthesis of [Ph2P(Se)N(CMe3)](1)
N-tert-butyl-1,1-diphenylphosphinamine (1.50 g, 5.82
mol) and elemental selenium (900 mg, 12.0 mol) were
heated to 60◦C in THF (10 mL) for 12 hours. Excess
selenium metal was filtered through a G4 frit to collect
the yellow colour filtrate. After evaporation of solvent
from filtrate in vacuo, a light yellow solid residue was
obtained. Compound 1 was re-crystallised from THF at
room temperature.
Yield: 1.85 g, 94%.
1H NMR (400 MHz, CDCl3): δ 8.02–8.08 (m, 4H,
ArH), 7.40–7.45 (m, 6H, ArH), 1.36 (s, 9H, CH3),
2.22 (br, 1H, NH) ppm. 13C{1H} NMR (100 MHz,
CDCl3): δ 136.3 (P attached ArC), 135.4 (P attached
ArC),131.8 (P attached o-ArC), 131.7 (P attached o-
ArC), 131.4 (P attached p-ArC), 128.3 (P attached m-
ArC), 128.1 (P attached m-ArC), 54.7 (CMe3), 31.5
(CH3) ppm. 31P{1H} NMR (161.9 MHz, CDCl3): δ
46.33 ppm. FT-IR (selected data): ν = 3216 (N–H),
1433 (P–C), 993 (P–N), 535 (P=Se) cm−1. Elemental
analysis: C16H20NPSe (336.26); Calculated: C 57.15 H
5.99 N 4.17, Found: C 56.89 H 5.39 N 3.81.
t
chemistry with phosphonic diamides BuP(O)(NHR)2
and phosphonic triamides (C5H9NH)3PO.36,37
In this context, detailed synthetic and struc-
tural features of the phosphinoselenoic amide ligand
[Ph2P(Se)N(CMe3)] (1), the corresponding monomeric
magnesium and calcium complexes of molecular
composition [M(THF)n{Ph2P(Se)N(CMe3)}2] [M =
Mg (3), n = 1 and M = Ca (4), n = 2)] and poly-
meric potassium and barium complexes [K(THF)2
{Ph2P(Se)N(CMe3)}]n (2) and [K(THF)Ba{Ph2P(Se)
N(CMe3)}3]n (5) respectively are presented.
2.3 Synthesis of [K(THF)2{Ph2 P(Se)N(CMe3)}]n (2)
2. Experimental
In a 10 mL sample vial, ligand 1 (100 mg, 0.296 mmol)
and [K{N(SiMe3)2}] (59.144 mg, 0.296 mmol) were
mixed together with 5 mL of THF. After 6 hours of
2.1 General information
All manipulations of air-sensitive materials were per- stirring, a small amount of THF (2 ml) and n-pentane
◦
formed with the rigorous exclusion of oxygen and (2 mL) were added to it and kept at −40 C. After
moisture in flame-dried Schlenk-type glassware either 24 hours, colourless crystals of compound 2 were
on a dual manifold Schlenk line, interfaced to a high obtained.

Alkali metal and alkaline earth metal complexes
1465
Yield: 140 mg, 90%.
Yield: 115.0 mg, 90%).
1H NMR (400 MHz, C6D6): δ 8.08–8.13(m, 4H, ArH), Route 2: In a 25 mL pre-dried Schlenk flask, compound
6.90–7.09 (m, 6H, ArH), 1.29 (s, 9H, CH3) ppm, 2 (320 mg, 0.68 mmol) was mixed with CaI2 (100 mg,
3.46 (m, THF), 1.31 (m, THF) ppm. 13C{1H} NMR 0.34 mmol) in 10 mL THF solvent at ambient tempera-
(100 MHz, C6D6): δ 133.8 (P attached ArC), 133.7 ture and stirring continued for 12 hours. The white pre-
(P attached ArC), 132.2 (P attached o-ArC), 131.2 cipitate of KI was filtered off and filtrate was evapo-
(P attached o-ArC), 130.1 (P attached p-ArC), 124.1 rated in vacuo. The resulting white residue was further
(P attached m-ArC), 123.4 (P attached m-ArC), 77.1 purified by washing with pentane and crystals suitable
(THF), 60.4 (CMe3), 14.2 (CH3), 25.6 (THF) ppm. for X-ray analysis were grown from THF/pentane (1: 2
31P{1H} NMR (161.9 MHz, C6D6): δ 46.3 ppm. FT-IR ratio) mixture at −40 ◦C.
(selected data): ν = 1433 (P–C), 992 (P–N), 576(P=Se)
cm−1. Elemental analysis: C24H32KNO2PSe (515.54);
Calculated: C 55.91 H 6.26 N 2.72, Found: C 55.36 H
5.92 N 2.43.
Yield: 270 mg, 92%.
1H NMR (400 MHz, C6D6): δ 8.12–8.17 (m, 8H, ArH),
7.09–7.16 (m, 12H, ArH), 3.76 (m, THF), 1.49 (s,
18H, CH3), 1.37 (m, THF) ppm. 13C{ H} NMR (100
1
2.4 Synthesis of [Mg(THF)n {η2-Ph2P(Se)N(CMe3)}
2] (3)
MHz, C6D6): δ 142.5 (P-ArC), 141.8 (P-ArC), 132.7
(P attached o-ArC), 132.6 (P attached o-ArC), 129.7
(P attached p-ArC), 127.5 (P attached m-ArC), 127.4
(P attached m-ArC), 68.7 (THF), 55.0 (CMe3), 35.9
(CH3), 25.6 (THF) ppm. 31P{1H} NMR (161.9 MHz,
C6D6): δ 37.1 ppm. FT-IR (selected data): ν = 1433
(P–C), 995 (P–N), 581 (P=Se) cm−1. Elemental analy-
sis: C44H62CaN2O4P2Se2 (942.90); Calculated: C 56.05
H 6.63 N 2.97, Found: C 55.77 H 6.32 N 2.58.
In a 25 mL pre-dried Schlenk flask, compound 2
(186 mg, 0.36 mmol) was mixed with MgI2 (50 mg,
0.18 mmol) in 10 mL THF solvent at ambient temper-
ature and stirred for 12 hours. The white precipitate
of KI was filtered and the filtrate was evaporated in
vacuo. The resulting white residue was further purified
by washing with pentane (3 mL) and crystals suitable
for X-ray analysis were grown from THF/pentane (1: 2
ratio) mixture at −40◦C.
2.6 Synthesis of [K(THF)Ba{Ph2P(Se)N(CMe3)}3]n
(5)
Yield: 118 mg, 85%.
In a 25 mL pre-dried Schlenk flask, potassium complex
2 (264 mg, 0.52 mmol) was mixed with BaI2 (100 mg,
0.26 mmol) in 10 mL THF solvent at ambient tempera-
ture and stirring continued for 12 hours. The white pre-
cipitate of KI was filtered and filtrate was evaporated
in vacuo. The resulting white compound was further
purified by washing with pentane and crystals suitable
for X-ray analysis were grown from THF/pentane (1:2
ratio) mixture at −40◦C.
1H NMR (400 MHz, C6D6): δ 8.17–8.23 (m, 8H,
ArH), 6.98–7.15 (m, 12H, ArH), 1.20 (s, 18H, CH3)
ppm. 13C{1H} NMR (100 MHz, C6D6): δ 132.4 (P-
ArC), 132.3 (P-ArC), 131.3 (P attached o-ArC), 130.8
(P attached o-ArC), 128.3 (P attached p-ArC), 128
(P attached m-ArC), 127.8 (P attached m-ArC), 55.0
(CMe3), 31.4 (CH3), ppm. 31P{ 1H} NMR (161.9
MHz, C6D6): δ 59.5 ppm. FT-IR (selected data): ν =
1436 (P–C), 930 (P–N), 570 (P=Se) cm−1. Elemental
analysis: C40H54MgN2O2P2Se2 (839.02); Calculated: C
57.26 H 6.49 N 3.34, Found: C 56.83 H 5.97 N 3.01.
Yield: 285 mg, 90%.
1H NMR (400 MHz, C6D6): δ 8.27–8.33 (m, 12H,
ArH), 7.08–7.15 (m, 18H, ArH), 1.27 (s, 27H, CH3)
ppm, 3.67 (m, THF), 1.51 (m, THF) ppm. 13C{1H}
NMR (100 MHz, C6D6): δ 132.3 (P attached ArC),
132.2 (P attached o-ArC), 132.1 (P attached o-ArC),
2.5 Synthesis of [(THF)n Ca{η2-Ph2P(Se)N(CMe3)}
2] (4)
Route 1: In a 10 mL sample vial, two equivalents 128.3 (P attached p-ArC), 128 (P attached m-ArC),
(100 mg, 0.296 mmol) of ligand 1 and one equivalent 127.8 (P attached m-ArC), 68.7 (THF), 58.9 (CMe3),
of [Ca{N(SiMe3)2}2(THF)2] were mixed together with 31.5(CH3), 25.6 (THF) ppm. 31P{1H} NMR(161.9
5 mL of THF. After 6 hours of stirring, another 2 mL MHz, C6D6): δ 46.3 ppm. FT-IR (selected data): ν =
of THF and n-pentane (2 mL) were added to it and 1433 (P–C), 996 (P–N), 576 (P=Se) cm−1. Elemental
kept at −40 ◦C. After 24 hours, colourless crystals were analysis: C56H73BaKN3O2P3Se3 (1326.39); Calculated:
obtained.
C 50.71 H 5.55 N 3.17, Found: C 50.23 H 5.11 N 2.74.

1466
Jayeeta Bhattacharjee et al.
2.7 Single-crystal x-ray structure determinations
(1.54184 Å) (for 2, 3, 4 and 5) radiation. Crystal data
and structure refinement parameters are summarised in
table 1. The structures were solved by direct meth-
ods (SIR92)42 and refined on F2 by full-matrix least-
squares methods; using SHELXL-97.43 Non-hydrogen
atoms were anisotropically refined. Hydrogen atoms
were included in the refinement on calculated posi-
Single crystals of compound 1 were grown from THF
at room temperature and complexes 2–5 were grown
from a solution of THF/pentane mixture (1:2) under
inert atmosphere at a temperature of −40◦C. In each
case a crystal of suitable dimensions was mounted on
a CryoLoop (Hampton Research Corp.) with a layer
of light mineral oil and placed in a nitrogen stream at
150(2) K. All measurements were made on an Agilent
Supernova X-calibur Eos CCD detector with graphite-
tions riding on their carrier atoms. The function min-
ꢀ
imised was [ w(Fo2 − Fc2)2] (w = 1 / [σ2 (Fo2)+
(aP)2+ bP]), where P = (Max(Fo2,0) + 2Fc2) / 3
with σ2(Fo2) from counting statistics. The function R1
monochromatic MoKα (0.71073 Å) (for 1) and Cu Kα and wR2 were (ꢀꢁFo| − |Fcꢁ) / ꢀ|Fo| and [ꢀw(Fo2 −
Table 1. Structural parameters for complexes 1-5.
Crystal Parameters
1
2
3
4
5
CCDC No.
Formula weight
T(K)
991038
336.26
150(2)
0.71073
Orthorhombic
P 21 21 21
9.5205(3)
9.5544(3)
17.5037(6)
90
991040
515.54
150(2)
1.54184
Monoclinic
P 21/c
11.2088(5)
24.0100(11)
10.8149(5)
90
11
90
2573.9(2)
4
1.330
991042
839.02
150(2)
1.54184
Monoclinic
P 21/c
10.5224(4)
10.0241(3)
39.048(2)
90
93
90
4110.2(3)
4
1.356
991041
942.90
150(2)
1.54184
Triclinic
P-1
9.0371(8)
10.3328(8)
13.0838(8)
88.7
991039
1326.39
150(2)
1.54184
Triclinic
P-1
11.1136(6)
11.6984(7)
24.9355(14)
87
82
67
2969.8(3)
2
1.483
λ(Å)
Crystal system
Space group
a (Å)
b (Å)
c (◦Å)
α(◦)
γ ( )
β(◦)
90
90
75
69
V(Å3)
1592.18(9)
4
1.403
2.446
688
1104.36(15)
1
1.418
4.131
490
Z
Dcalc g cm−3
μ(mm−1
F(000)
)
4.155
1068
3.402
1736
9.007
1336
Theta range for
data collection
Limiting indices
–
2.43 to 25.77 deg. 3.68 to 70.91 deg. 4.21 to 70.74 deg. 4.59 to 70.91 deg. 4.09 to 70.59 deg.
−11 <= h <= 6 −13 <= h <= 13 −12 <= h <= 12, −11 <= h <= 10, −13 <= h <= 13,
−11 <= k <= 10 −29 <= k <= 29 −12 <= k <= 11, −12 <= k <= 11, −8 <= k <= 14,
−20 <= l <= 12 −8 <= l <= 13 −47 <= l <= 35 −15 <= l <= 14 −30 <= l <= 30
Reflections collected / 3347 / 2379
10691 / 4852
16320 / 7738
7548 / 4145
22614 / 11197
unique
Completeness
to theta
[R(int)= 0.0206] [R(int) = 0.0377] [R(int) = 0.0369] [R(int) = 0.0339] [R(int)=0.0570]
87.7 % (25.77)
97.6 % (70.91)
97.9 %
97.5 %
98.2 %
Absorption correction Å
Multi-Scan
Multi-Scan
1.00000 and
0.61950
Multi-Scan
1.00000 and
0.65234
Multi-Scan
1.00000 and
0.12772
Max. and min.
1.000 and 0.705 1.00000 and
transmission
0.65812
Refinement method Full-matrix least- Full-matrix least- Full-matrix least- Full-matrix least- Full-matrix least-
squares on F∧2
2379 / 0 / 176
squares on F∧2
4852 / 0 / 273
squares on F∧2
7738 / 0 / 448
squares on F∧2
4145 / 0 / 253
squares on F∧2
11197 / 0 / 581
Data / restraints /
parameters
Goodness-of-fit on F2 1.080
1.061
1.057
1.067
1.031
Final R indices
[I>2sigma(I)]
R indices (all data)
R1 = 0.0296,
R1 = 0.0566,
wR2 = 0.1559
R1 = 0.0712,
wR2 = 0.1762
R1 = 0.0404,
wR2 = 0.1019
R1 = 0.0515,
wR2 = 0.1071
R1 = 0.0449,
wR2 = 0.1249
R1 = 0.0494,
wR2 =0.1296
R1 = 0.0663,
wR2 = 0.1766
R1 = 0.0726,
wR2 = 0.1881
wR2 = 0.0797
R1 = 0.0298,
wR2 = 0.0801
0.645(10)
Absolute structure
parameter
Largest diff. peak
and hole
0.336 and
0.966 and
0.483 and
1.151 and
2.988 and
−0.570 e.Å−3
−1.174 e.Å−3
−0.920 e.Å−3
−0.710 e.Å−3
−2.197 e.Å−3

Alkali metal and alkaline earth metal complexes
1467
Fc2)2/ꢀ(wFo4)]1/2 respectively. The ORTEP-3 program 901 cm−1.42 In the 1H NMR spectra, resonance sig-
was used to draw the molecule. Crystallographic data nal at 1.36 ppm corresponds to the nine methyl pro-
(excluding structure factors) for the structures reported tons of the t-butyl group and signal at 2.22 ppm rep-
in this paper have been deposited with the Cambridge resents the amine N–H proton of ligand 1. Both the
Crystallographic Data Centre as a supplementary pub- values are slightly downfield shifted with respect to
lication, Nos. CCDC 991038 (1), 991040 (2), 991042 the free phosphine amine [Ph2PNHC(CH3)3]. In the
(3), 991041 (4), 991039 (5). Copies of the data can be
13C{1H} NMR spectrum of compound 1, signals at
obtained free of charge on application to CCDC, 12 54.7 and 31.5 ppm can be best assigned to tertiary car-
Union Road, Cambridge CB2 1EZ, UK (fax: + (44) bon atom and methyl carbon atom, respectively. Pro-
1223-336-033; email: deposit@ccdc.cam.ac.uk).
ton decoupled 31P{1H} NMR spectra is more informa-
tive as compound 1 shows a signal at 46.3 ppm which
is slightly downfield shifted from the phosphine amine
[Ph2PNHC(CH3)3] (28.6 ppm) due to addition of the
selenium atom to the phosphorus atom.
3. Results and Discussion
The bulky phosphinoselenoic amine [Ph2P(Se)NHC
(CH3)3] (1) was prepared in a similar fashion
as [Ph2P(Se)NH-2,6-Me2C6H4]. [Ph2P(Se)NHCHPh2]
and [Ph2P(Se)NHCPh3] were synthesised in quanti-
tative yield by the treatment of [Ph2PNHC(CH3)3]
with elemental selenium in 1:2 molar ratio at ambi-
ent temperature in THF solvent (scheme 1).35,42 Com-
pound 1 was characterised using standard analyti-
cal/spectroscopic techniques and its solid-state struc-
ture was established by single crystal X-ray diffraction
analysis.
FT-IR spectrum of compound 1 shows strong absorp-
tion bands at 535 cm−1 and 993 cm−1 which can be
assigned to the characteristic P=Se and P–N bond
stretching frequencies respectively and these values
are comparable with reported values 568 cm−1 and
In the solid-state structure, compound 1 crystallises
in the orthorhombic P 212121 space group, having four
molecules in the unit cell. The solid-state structure
of compound 1 is shown in figure 1. The details of
the structural parameters are given in table 1. The
P=Se bond distance is found to be 2.1187(8) Å, which
is in good agreement with values we reported pre-
viously: 2.1019(8) Å for [Ph2P(Se)NH(2,6-Me2C6H4)],
2.1086(12) Å for [Ph2P(Se)NHCHPh2] and 2.1166(8) Å
for [Ph2P(Se)NHCPh3]. P1–N1 distance [1.655(3) Å]
and C1–N1 distance [1.494(4) Å] are also similar to
those of phosphinoselenoic amides [Ph2P(Se)NHR],
which we previously reported: P1–N1 1.656(3) Å, C1–
N1 1.441(4) Å for R = 2,6-Me2C6H4, P1–N1 1.642(4)
Å, C1–N1 1.459(6) Å for R = CHPh2, and P1–N1
1.664(2) Å, C1–N1 1.496(4) Å for R = CPh3).35,44
Scheme 1. Synthesis of alkali and alkaline earth metal complexes of phosphinoselenoic amide ligand (1).

1468
Jayeeta Bhattacharjee et al.
[Ph2P(Se)NCHPh2]− (K-Se 3.3090(10) Å).35 The K1–
N1 bond distance is 3.047(3) Å which is slightly elon-
gated compared to the previously reported value of K–N
2.725(3) Å).35 The P1–K1 distance is 3.3806(13) Å and
this is slightly shorter than the corresponding distances
3.5579(12) Å in [{(THF)2KPh2P(Se)N(CHPh2)}2],35
3.5354(14) Å in [{(THF)2KPh2P(S)N(CHPh2)}2]45 and
3.5148(10) Å in [{(Ph2CHNP(BH3)Ph2)K(THF)2} 2],46
which we reported. The P1–K1 distance is within
the sum of the covalent radii (3.45 Å) of potassium
and phosphorous atoms, indicating a covalent inter-
action between them.47 The potassium atom also has
a weak interaction with one of the methyl carbon
atoms of the tertiary butyl group [the K1· · · C2 dis-
tance is 3.210(5) Å]. The one-dimensional polymeric
network for complex 2 is formed by the extended
coordination of the selenium atom with the potassium
atom of the neighbouring molecule. The K–Se dis-
tance of 3.2859(11) Å is within the range of the val-
ues mentioned above. Two additional THF molecules
are chelated to the potassium atom, with K1–O1 and
K1–O2 bond distances of 2.606(5) Å and 2.654(3) Å
respectively. Therefore, the geometry of each potassium
centre in the polymeric unit is best described as dis-
torted octahedral. It is noteworthy that the polymeric
structure for complex 2 was observed, due to the bulky
t−butyl group on the amido nitrogen, as in contrast
only dimeric polymetallacyclic structure for the potas-
sium salt [(THF)2K{Ph2P(Se)N(CHPh2)}]2 potassium
structure was found by using diphenylmethyl (CHPh2)
group on the same nitrogen atom, keeping other groups
identical in our previous report.35 Thus, the presence
of the more bulky t-butyl group at nitrogen plays an
important role in determining the nuclearity of com-
plex 2. In the solution state, complex 2 shows only one
set of signals similar to the free ligand 1 in the 1H,
13C{1H} and 31P{1H} NMR spectra, which indicates
the dynamic behaviour of complex 2 in the solution
state. 31P{1H} NMR spectra of complex 2 shows sin-
gle peak at 46.33 ppm which is very similar to ligand 1
(46.30 ppm), indicating that there is no influence of the
potassium atom on the phosphorous centre of ligand 1
upon complex formation.
Figure 1. ORTEP diagram of 1 with thermal displacement
parameters drawn at the 30% probability level; hydrogen
atoms were omitted for clarity. Selected bond lengths [Å]
and bond angles [◦]. P1-N1 1.655(3), P1-Se1 2.1187(8),
P1-C5 1.815(3), P1-C11 1.816(3), N1-C1 1.494(4), C1-
C2 1.533(5), C1-C3 1.526(5), C1-C4 1.529(5), N1-P1-Se1
119.41(10), Se1-P1-C5 112.48(10), Se1-P1-C11 110.70(10),
N1-P1-C11 102.22(13), C5-P1-C11 105.15(14), P1-N1-C1
127.6(2), N1-C1-C4 109.9(3), N1-C1-C3 106.1(3), C2-C1-
C3 109.9(3), C2-C1-C4 110.4(3), N1-C1-C2 110.4(3), C3-
C1-C4 110.1(3).
3.1 Potassium complex
The potassium complex of composition [K(THF)2
{Ph2P(Se)N(CMe3)} ]n (2) can be readily prepared
by the reaction of compound 1 and potassium
bis(trimethylsilyl)amide in THF through the elimina-
tion of volatile bis(trimethylsilyl)amine (scheme 1).
Compound 2 was re-crystallised from a mixture of
THF/pentane. Air and moisture sensitive compound 2
crystallises in the monoclinic P 21/c space group, with
four molecules in the unit cell. The details of the struc-
tural and refinement parameters are given in table 1.
The asymmetric unit as well as the polymeric form of
compound 2 in the solid state is shown in figure 2.
In the asymmetric unit, the central potassium atom is
3.2 Alkaline earth metal complexes
surrounded by one monoanionic ligand 1 coordinat- The magnesium, calcium and barium complexes 3,4
ing through the selenium and amido nitrogen atoms and 5 respectively, were prepared in good yield and
to form a four-membered metallacycle K1–Se1–P1– high purity using two synthetic routes. In the first
N1 with angles N1–K1–Se1 of 61.33(6) Å and N1– method, complexes 3–5 were prepared by the reac-
P1–Se1 of 119.10(13) Å. The K1–Se1 bond distance is tion of respective alkaline earth metal diiodides MI2
3.3125(10) Å which is in good agreement with the value (where M = Mg, Ca and Ba) with potassium salt of
we previously reported for the potassium salt of ligand phosphinoselenoic amide [K(THF)2{Ph2P(Se)N(CMe3)}]n

Alkali metal and alkaline earth metal complexes
1469
Figure 2. ORTEP diagram of 2 with thermal displacement parameters drawn
at the 30% probability level; hydrogen atoms were omitted for clarity. Selected
bond lengths [Å] and bond angles [◦]. K1-N1 3.047(3), K1-Se1 3.3125(10),
K1-O1 2.606(5), K1-O2 2.654(3), K1-C2 3.210(5), P1-N1 1.576(3), P1-
Se1 2.1792(11),P1-C5 1.842(4), P1-C11 1.825(4), N1-C1 1.476(5), C1-
C2 1.534(6), C1-C3 1.528(6), C1-C4 1.542(6), P1-N1-K1 87.97(14), C1-
N1-K1 106.2(2), P1-Se1-K1 72.70(3), N1-K1-Se1 61.33(6), Se1-K1-O1
105.06(18), O1-K1-O2 93.6(2), N1-K1-O2 88.29(10), O1-K1-N1 126.8(2),
Se1-K1-O2 149.61(8), N1-P1-C5 114.69(18), C5-P1-C11 100.89(17), C11-
P1-Se1 108.10(13), N1-P1-Se1 119.10(13), C11-P1-N1 103.72(18), C5-P1-
Se1 108.42(13), P1-N1-C1 126.3(3), C2-C1-N1 109.8(3), N1-C1-C3 107.0(3),
C2-C1-C3 108.5(4), C2-C1-C4 108.3(4 ), C3-C1-C4 108.4(4).
(2), which was prepared according to the procedure Ph2P(Se)N(CMe3)}2] (4) (scheme 1). The first route
in the literature involving ligand 1 and potassium was followed for the three metal complexes 3–5,
bis(trimethylsilyl)amide.48 The second method invol- while the second was followed only for complex 4.
ved treating the phosphinoselenoic amide (1) directly The novel alkaline earth metal complexes 3–5 were
with calcium bis(trimethylsilyl)amide [Ca{N(SiMe3)2} characterised using analytical/spectroscopic techniques
2{THF}n] in THF at ambient temperature to afford the and the molecular structures of complexes 3–5 were
calcium complex of molecular formula [(THF)2Ca{η2- determined by single crystal X-ray diffraction analyses.

1470
Jayeeta Bhattacharjee et al.
axial position. Two four-membered metallacycles N1–
The strong absorption at 570 cm−1 (for 3), 581 cm−1
(for 4) and 576 cm−1 (for 5) in FT-IR spectra indicates
the evidence of P=Se bond in each complex and the
values are very similar to that of the neutral ligand 1
(535 cm−1) due to the slight elongation of P=Se bond
bound to the metal centre. In 1H NMR spectra, the
amino proton of ligand 1, which was present at 2.22
ppm, is absent. Two multiplet signals for each com-
plex at 3.76 and 1.37 ppm (for 4), 3.67 and 1.51 ppm
(for 5) can be assigned to the solvated THF molecules
coordinated to the metal centre. One set of signals for
the phenyl protons are also observed, which is in the
same range as that of ligand 1, indicating no signifi-
cant effect of metal atoms on the phenyl groups due
to complex formation. In 31P {1H} NMR spectra, in
complexes 3–5, all the phosphorus atoms present in the
phosphinoselenoic amide ligand (1) moieties are chem-
ically equivalent and show only one signal at 59.5 ppm
(for 3), 37.1 ppm (for 4) and 46.3 ppm (for 5). For
compound 3 this value is shifted to downfield and for
compound 4, shifted up field in comparison to potas-
sium salt 2 (46.3 ppm) and neutral ligand 1 (46.3 ppm).
Unlike the magnesium and calcium complexes (3 and
4), the barium complex 5 shows 31P{1H} NMR signal
at 46.3 ppm which is the same as that of potassium salt
2 as well as neutral ligand 1 (46.3 ppm). This observa-
tion is quite different from our previous studies where
we noticed a high downfield shift for the resonance of
phosphorus atoms (71.9 ppm for Ca, 71.8 ppm for Sr
and 71.9 for Ba) bound to heavier alkaline earth metals
compared to the free phosphinoselenoicamido ligand
[Ph2P(Se)NCHPh2]−(58.0ppm).35
P1–Se1–Mg1 and N2–P2–Se2–Mg1 are formed and a
dihedral angle of 40.6◦ is observed between the two
mean planes, having N1, P1, Se1 and Mg1, and N2, P2,
Se2 and Mg1 atoms respectively.
The most interesting thing is that the magnesium–
selenium bond distances [Mg1-Se1 2.6964(12) Å and
Mg1–Se2 2.7056(12) Å] are slightly elongated in com-
parison to previously reported value of 2.536(3) Å for
the compound [Mg(SeMes*)2(THF)2] (where Mes* =
2,4,6-t-Bu3C6H2).27 This is mainly due to the steric
bulk on the backbone of the phosphineamido ligand
moiety. The magnesium–nitrogen distances [Mg1–N1
2.169(3) Å and Mg1–N2 2.145(3) Å] were observed
for compound 3; these are slightly longer when
compared to the Mg–N bond reported in the liter-
ature. For example, the Mg–N bond distance was
reported as 1.970(3) Å for [{(LiPr)2Mg(THF)2}·(THF)],
2.094(3) Å for [{(LiPr)2Mg}·(THF)] (where LiPr = [(2,
6-iPr2C6H3)NC(Me)]2) and 2.051(2) Å for [(LMes
)
2
Mg(THF)3] and 2.070(2) Å for [(LMes)2Mg] (where
LMes = [(2,4,6 Me3C6H2)NC(Me)]2).50 Recently, we
also synthesised magnesium complex of the type [Mg
{C2H4(NPh2P(Se))2}{THF)3] in which we observed
Mg–N distances of 2.066(3) Å and 2.083(3) Å, which
is well in agreement with the reported values, but
slightly shorter than the observed values 2.169(3) Å
and 2.145(3) Å for complex 3. The P–Se bond dis-
tances [2.1567(9) Å and 2.1581(9) Å] and P–N bond
distances [1.606(3) Å and 1.602(3) Å] are within the
range for alkaline earth metal complexes that we
previously reported: P–Se distance 2.1449(18) Å for
Ca, 2.1477(12) Å for Sr and 2.152(2) Å for Ba, and
P–N distance 1.631(6) Å for Ca, 1.610(3) Å for Sr and
1.609(7) Å for Ba.35
In the solid state, the magnesium complex 3 crys-
tallises in the monoclinicP 21/c space group, with
four molecules in the unit cell. The details of the
structural parameters for compound 3 are given in
table 1. The molecular structure of compound 3 is
shown in figure 3. In magnesium complex 3, the coor-
dination polyhedron is formed by two monoanionic
[Ph2P(Se)N(CMe3)]− ligands, and one THF molecule.
Each [Ph2P(Se)N(CMe3)]− ligand coordinates to the
In contrast to the magnesium complex 3 the
homoleptic calcium complex 4 crystallises in the tri-
clinic space group P −1, with one molecule in the
unit cell. The details of the structural parameters are
given in table 1. The solid state structure of complex
4 is shown in figure 4. In accordance with alka-
magnesium atom through the chelation of one sele- line earth metal complexes, we previously reported
nium atom and one amido nitrogen atom. The P– [M{Ph2P(Se)NCHPh2}2(THF)2] (where M = Ca and
Mg distance of 2.9963(14) Å and 2.9987(14) Å is Sr), in the calcium complex 4, the coordination polyhe-
slightly greater than the average Mg–P coordination dron is formed by two [Ph2P(Se)N(CMe3)]− ligands,
bond (2.667 Å) and thus a weak interaction between
them was observed.49 Thus the [Ph2P(Se)N(CMe3)]−
group can be considered a bi-dentate ligand. The
geometry around the central magnesium atom can be
best described as a distorted square pyramidal, hav-
ing two amido nitrogen and two selenium atoms of
two [Ph2P(Se)N(CMe3)]− moieties in the basal plane
and the oxygen atom from the THF molecule at the
and two THF molecules which are trans to each other.
Therefore, the calcium atom adopts a distorted octahe-
dral geometry. The structural differences between the
magnesium and calcium complexes can be explained
by the larger ionic radius of Ca2+ (0.99 Å) compared
to that of Mg2+ (0.72 Å).51 The Ca–Se bond distance
of 2.9619(3) Å observed in complex 4 is quite long,
compared to the magnesium analogue [(2.6964(12) Å

Alkali metal and alkaline earth metal complexes
1471
Figure 3. ORTEP diagram of 4 with thermal displacement parameters drawn
at the 30% probability level; hydrogen atoms were omitted for clarity.
Selected bond lengths [Å] and bond angles [◦]. Mg1-N2 2.145(3), Mg1-
Se2 2.7056(12), Mg1-O1 2.067(3), Mg1-N1 2.169(3), Mg1-Se1 2.6964(12),
P1-Se1 2.1567(9), P1-N1 1.606(3), N1-C1 1.496(4), P1-C5 1.828(4), P1-
C11 1.827(4), P2-N2 1.602(3), P2-Se2 2.1581(9), P2-C21 1.825(4), P2-C27
1.834(4), N2-C17 1.497(4), Mg1-Se2-P2 75.19(3), Mg1-N2-P2 105.39(14),
N2-Mg1-Se2 74.99(8), N2-Mg1-O1 95.95(11), O1-Mg1-Se1 107.81(8), Se2-
Mg1-N1 100.90(8), Se1-Mg1-N1 75.40(8), Mg1-Se1-P1 75.34(3), Mg1-N1-P1
104.11(14), Mg1-N1-C1 129.4(2), N1-P1-Se1 105.03(10), P1-N1-C1 129.4(2),
Se1-P1-C11 105.55(12), N1-P1-C5 116.52(16), C5-P1-C11 103.97(17), Se1-
P1-C5 109.51(12), N1-P1-C11 115.73(16), C21-P2-C27 105.86(17), N2-P2-
C21 115.08(16), Se2-P2-C27 110.60(11), N2-P2-Se2 104.18(10), N2-P2-C27
114.30(15), Se2-P2-C21 106.61(12).
Figure 4. ORTEP diagram of 4 with thermal displacement parameters drawn
at the 30% probability level; hydrogen atoms were omitted for clarity. Selected
bond lengths [Å] and bond angles [◦]. Ca1-N1 2.451(3), Ca1-Se1 2.9619(3),
Ca1-O1 2.465(2), Ca1-O1i 2.465(2), Ca1-Se1i 2.9619(3), Ca1-N1i 2.451(3),
P1-N1 1.591(3), P1-Se1 2.1706(8), N1-C1 1.495(4), P1-C5 1.835(3), P1-
C11 1.835(3). Ca1-N1-C1 126.33(19), P1-N1-Ca1 105.15(13), P1-Se1-Ca1
76.91(2), N1-Ca1-Se1 68.73(6), N1-Ca1-O1 92.66(8), O1-Ca1-Se1i92.66(8),
Se1i-Ca1-N1i68.73(6), N1i-Ca1-O1i 92.66(8), C11-P1-C5 104.56(15), C11-
P1-N1 112.89(14), N1-P1-Se1 109.19(10), C5-P1-N1 115.73(16), C11-P1-Se1
107.43(10), P1-N1-C1 126.9(2).

1472
Jayeeta Bhattacharjee et al.
Figure 5. ORTEP diagram of 5 with thermal displacement parameters drawn at
the 30% probability level; hydrogen atoms were omitted for clarity. Selected bond
lengths [Å] and bond angles [◦]. Ba1-Se2 3.3203(7), Ba1-Se3 3.3518(7),Ba1-N2
2.790(5),Ba1-N3 2.789(5),Ba1-Se1 3.3274(7), Ba1-N1 2.774(5), O1-K1 2.731(6),
K1-Se3 3.4175(15), K1-Se2 3.3627(15),P1-N1 1.603(5), P1-Se1 2.1681(16), N1-C1
1.491(8), P1-C11 1.825(6), P1-C5 1.826(6), P2-Se2 2.1681(15), P2-C27 1.835(6),
P2-C21 1.852(6), P2-N2 1.577(5), N2-C17 1.488(7), P3-Se3 2.1692(15), P3-N3
1.593(5), N3-C33 1.490(8), P3-C37 1.829(6), P3-C43 1.838(6), N3-C33 1.490(8).
K1-Se3-Ba1 96.20(3), K1-Se2-Ba1 97.86(3), Se2-Ba1-Se3 82.865(18), P2-Se2-
Ba1 79.80(4), P2-N2-Ba1 109.3(2), N2-Ba1-Se2 59.95(10), Se3-Ba1-N3 59.78(10)
, N3-Ba1-Se1 95.75(10), N1-Ba1-Se1 59.68(11), N1-Ba1-N2 106.15(15), Ba1-
Se1-P1 80.57(4), Ba1-N1-P1 110.7(2),Ba1-N1-C1 119.3(4),Ba1-N3-P3 109.9(2) ,
Ba1-N3-C33 122.5(3), O1-K1-Se3 101.11(13), O1-K1-Se2 168.59(14), Se2-K1-Se3
81.26(3),N1-P1-Se1 108.26(19), P1-N1-C1 126.5(4), Se1-P1-C5 105.8(2), N1-P1-
C11 114.1(3), C5-P1-C11 103.6(3), N1-P1-C5 115.8(3).

Alkali metal and alkaline earth metal complexes
1473
and 2.7056(12) Å] due to the larger ionic radius of group.35 The K−C distances vary between 3.333(6) Å
the Ca2+ ion. The observed Ca–Se bond distance and 3.336(6) Å, which are comparable with the
[2.9619(3) Å] is within the range of Ca–Se distances K−C bond lengths found in [(LMes)22−Mg(η6:η6-
[2.9889(8) Å] of the structurally characterised com- K(THF)2)][K(THF)6]· (THF)2 where LMes = [(2,4,6-
plex [Ca{Ph2P(Se)NCHPh2}2(THF)2] reported by us.35 Me3C6H2)NC(Me)]2 (3.127 Å and 3.259 Å)50 and
In the literature, we find 2.945(1) Å reported for [{(THF)2K(μ-N(Ph)iPr)2}2Ca] (3.156(2)−3.259(2) Å)
[(THF)2Ca{(PyCH)(Se)PPh2}2],26 2.93 Å to 3.00 Å with the slipped η6-coordination.54 –60 The average
reported for [(THF)4Ca(SeMesꢂ)2] and 2.958(2) Å distance of K· · · phenyl ring is about 3.127 Å and
to 3.001(2) Å reported for [(THF)2Ca(Se2PPh2)2].16,23 Ba· · · K separation is about 5.039 Å which allows the
The Ca–N distance [2.451(3) Å is slightly longer potassium ion to interact with the selenium atom [K1–
compared to the calcium–nitrogen covalent bond repor- Se1# 3.3259(15) Å] of the neighbouring unit to grow
ted in the literature [2.361(2) Å and 2.335(2) Å] the one dimesional polymer. Thus we observed that
reported for [Ca(Dipp2DAD)(THF)4] (Dipp2DAD = larger ion radii (K+ and Ba2+) form polymeric com-
N,Nꢂ-bis(2,6-diisopropylphenyl)-1,4-diaza-1,3-buta-
plexes with ligand 1. The P–Se bond [2.1681(16) Å,
diene.19 The P–Ca distance [3.2516(8) Å] is too long to 2.1681(15) Å and 2.1692(15) Å] is slightly longer
consider any interaction between them.
[2.1187(8) Å for ligand 1] upon coordination of the
selenium and barium atoms. A weak interaction
between barium and phosphorus [Ba1–P1 3.6617(15),
Ba1–P2 3.6299(15) and Ba1–P3 3.6520(14)] was also
observed. The Ba–N distances [2.774(5) Å, 2.790(5) Å
and 2.789(5) Å] are similar to the values [2.777(6) Å
and 2.778(6) Å] for [Ba(Ph2P(Se)NCHPh2)2(THF)2],
2.733(6) Å for [Ba(Ph2P(BH3)NCHPh2)2(THF)2] repor-
ted by us35 and 2.720(4) Å and 2.706(4) Å for [Ba
((Dip)2DAD)(μ-I)(THF)2]2 reported in the literature.18
Unlike the magnesium and calcium complexes 3 and
4, barium metal forms an ‘ate’ complex of molecular
formula [K(THF)Ba{Ph2P(Se)N(CMe3)}3]n (5). This
is mainly due to the larger ionic radius of the Ba2+
ion and t−butyl group on the nitrogen atom of ligand
1 allows the third anionic ligand to coordinate to the
barium centre. Complex 5 crystallises in the triclinic
space group P−1, with two molecules in the unit cell.
The details of the structural parameters are given in
table 1. The solid state structure of complex 5 is shown
in figure 5. In the asymmetric unit of complex 5, the
central Ba2+ion is surrounded by three anionic ligand
1 moieties, which coordinate with Ba2+ ion through
the amide nitrogen and selenium atoms. There is
one potassium ion (K1) in complex 5, which is η3–
attachment by two flanking phenyl rings from each of
the phosphinoselenoic amide ligand moiety and one
THF molecule also coordinated to potassium. In addi-
tion, two selenium atoms of the two anionic ligands
are coordinated to the potassium ion in the bridging
fashion. The geometry of the barium in complex 5
is therefore best described as distorted octahedral
geometry. The Ba–Se bond distances [3.3274(7) Å,
3.3203(7) Å and 3.3518(7) Å] in complex 5 are within
the range of the Ba–Se distances [3.366(1) Å and
3.324(1) Å] for the complex [{BaI(4,5-(P(Se)Ph2)2tz)}
2(thf)7] reported by Raymundo Cea-Olivares et al.52
3.2787(11) Å for [Ba(THF)4(SeMes*)2] (Mes* =
2,4,6-t-Bu3C6H2) and 3.2973(3) Å for [{Ba(Py)3
(THF)(SeTrip)2}2] (Trip = 2,4,6-iPr3C6H2) reported
by Ruhlandt-Senge et al.,34 3.3553(10) Å and
3.3314(10) Å for [Ba{Ph2P(Se)NCHPh2}2(THF)2],
and 3.3842(8) Å for [{η2-N(PPh2Se)2} 2Ba(THF)3]
previously reported by us.34,53 The K–Se dis-
4. Conclusion
We have demonstrated the monomeric and polymeric
alkali metal and alkaline earth metal complexes with
phosphinoselenoic amide ligand 1, and in each com-
plex direct metal selenium is observed. In the solid
state, due to differences in the ionic radii of the metal
centres, the magnesium complex adopts a square pyra-
midal geometry, whereas the calcium complex adopts
a distorted octahedral geometry with the phosphi-
noselenoic amide ligand. Since the barium atom is
the largest in terms of ionic radii amongst Mg, Ca
and Ba, a polymeric ate-complex of molecular for-
mula [K(THF)Ba{Ph2P(Se)N(CMe3)}3]n is obtained.
The unique feature of ligand 1, with three poten-
tial donor atoms, nitrogen, phosphorus and selenium,
makes a clear distinction in molecular structure among
the alkali and alkaline earth metal complexes. Further
reactivity studies on these complexes are underway in
our laboratory.
Supplementary Information (SI)
tances 3.3627(15) Å and 3.4175(15) Å are also The H and 13C{1H} NMR spectra of compounds 1-
within the range [3.3090(10) Å] for the complex 5 are given in supplementary information available at
[{(THF)2KPh2P(Se)N(CHPh2){2] reported by our www.ias.ac.in/chemsci.
1

1474
Jayeeta Bhattacharjee et al.
25. Englich U and Ruhlandt-Senge K 2001 Z. Anorg. Allg.
Acknowledgements
Chem. 627 851
26. Kling C, Ott H, Schwab G and Stalke D 2008 Organo-
metallics 27 5038
This work was supported by the Council of Scien-
tific and Industrial Research (CSIR) under project
no. 01(2530)/11/EMR-11 and start-up grant from IIT
Hyderabad. J.B., R.K.K. thank the University Grants
Commission, India, and H. A thanks to CSIR India, for
their PhD fellowships.
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