Preparation and reactivity towards hydrazines of bis(cyanamide) and bis(cyanoguanidine) complexes of the iron triad

Article abstract of DOI:10.1039/c4dt00394b

Bis(diethylcyanamide) [Fe(NCNEt₂)₂L ₄](BPh₄)₂1a and bis(cyanoguanidine) [Fe{NCN(H)C(NH₂)NH}₂L₄](BPh₄) ₂1b [L = P(OEt)₃] complexes were prepared by allowing iron(ii) chloride to react first with an excess of P(OEt)₃ and then of the appropriate cyanamide, followed by addition of an excess of NaBPh ₄. Instead, bis(complexes) of ruthenium and osmium [M(NCNEt ₂)₂L₄](BPh₄)₂2a, 3a and [M{NCN(H)C(NH₂)NH}₂L₄](BPh₄) ₂2b, 3b (M = Ru 2, Os 3) were prepared by reacting hydrides MH ₂L₄ first with either triflic acid HOTf or methyltriflate MeOTf and then with an excess of the appropriate cyanamide. Hydride- diethylcyanamide [MH(NCNEt₂)L₄]BPh₄4a, 5a and hydride-cyanoguanidine complexes [MH{NCN(H)C(NH₂)NH}L ₄](BPh₄)₂4b, 5b (M = Ru 4, Os 5) were also obtained by reacting MH₂L₄ first with one equivalent of HOTf or MeOTf and then with the appropriate cyanamide. Treatment of bis(cyanamide) and bis(cyanoguanidine) complexes 1-3 with hydrazines RNHNH ₂ afforded hydrazinecarboximidamide derivatives [M{η²- N(H)C(NEt₂)N(R)NH₂}L₄](BPh₄) ₂6a-12a and [M{η²-N(H)C[NC(NH₂) ₂]N(R)NH₂}L₄](BPh₄) ₂6b-12b (M = Fe 6-8, Ru 9, 10, Os 11, 12; R = H 6, 9, 11, Me 7, 10, 12, Ph 8). A reaction path involving nucleophilic attack by hydrazine on the cyanamide carbon atom is proposed. All the complexes were characterised by spectroscopy and X-ray crystal structure determination of [Os{η²- NHC[NC(NH₂)₂]N(CH₃)NH₂}{P(OEt) ₃}₄](BPh₄)₂12b.

Full text of DOI:10.1039/c4dt00394b

Dalton
Transactions
View Article Online
View Journal | View Issue
PAPER
Preparation and reactivity towards hydrazines of
bis(cyanamide) and bis(cyanoguanidine)
complexes of the iron triad†
Cite this: Dalton Trans., 2014, 43,
7314
Gabriele Albertin,*a Stefano Antoniutti,a Alfonso Caiaa and Jesús Castrob
Bis(diethylcyanamide) [Fe(NuCNEt2)2L4](BPh4)2 1a and bis(cyanoguanidine) [Fe{NuCN(H)C(NH2)v
NH}2L4](BPh4)2 1b [L = P(OEt)3] complexes were prepared by allowing iron(II) chloride to react first with an
excess of P(OEt)3 and then of the appropriate cyanamide, followed by addition of an excess of NaBPh4.
Instead, bis(complexes) of ruthenium and osmium [M(NuCNEt2)2L4](BPh4)2 2a, 3a and [M{NuCN(H)C-
(NH2)vNH}2L4](BPh4)2 2b, 3b (M = Ru 2, Os 3) were prepared by reacting hydrides MH2L4 first with either
triflic acid HOTf or methyltriflate MeOTf and then with an excess of the appropriate cyanamide. Hydride-
diethylcyanamide [MH(NuCNEt2)L4]BPh4 4a, 5a and hydride-cyanoguanidine complexes [MH{NuCN(H)-
C(NH2)vNH}L4](BPh4)2 4b, 5b (M = Ru 4, Os 5) were also obtained by reacting MH2L4 first with one equi-
valent of HOTf or MeOTf and then with the appropriate cyanamide. Treatment of bis(cyanamide) and bis-
(cyanoguanidine) complexes 1–3 with hydrazines RNHNH2 afforded hydrazinecarboximidamide deriva-
tives [M{η2-N(H)vC(NEt2)N(R)NH2}L4](BPh4)2 6a–12a and [M{η2-N(H)vC[NvC(NH2)2]N(R)NH2}L4](BPh4)2
6b–12b (M = Fe 6–8, Ru 9, 10, Os 11, 12; R = H 6, 9, 11, Me 7, 10, 12, Ph 8). A reaction path involving
nucleophilic attack by hydrazine on the cyanamide carbon atom is proposed. All the complexes were
characterised by spectroscopy and X-ray crystal structure determination of [Os{η2-NHvC[NvC(NH2)2]-
N(CH3)NH2}{P(OEt)3}4](BPh4)2 12b.
Received 6th February 2014,
Accepted 4th March 2014
DOI: 10.1039/c4dt00394b
www.rsc.org/dalton
vated CN triple bond of cyanoguanidine, reported for Cu, Ni
and Pt,13 and amination of Pt-bonded cyanoguanidine.6f
Introduction
The chemistry of transition metal complexes containing either
We are interested in the chemistry of azo complexes of the
cyanamides NuCNR2 (R = H, alkyl, aryl) or the related cyano- iron triad and have reported the synthesis of not only diazene
guanidine NuCN(H)C(NH2)vNH as ligands1–8 has been far and hydrazine derivatives,14 but also amidrazone complexes
less developed than that of organonitriles RCN,9,10 in spite of obtained by nucleophilic attack of hydrazine on the coordinate
the synthetic and biological interest of these amino-functiona- nitrile.15 Recently, extension to cyanamide ligands allowed us
lised nitrile species. They are in fact used as precursors in the to prepare diethylcyanamide and cyanoguanidine complexes of
synthesis11 of polymers, fertilisers, pesticides and pharmaceu- Ru and Os stabilised by half-sandwich p-cymene fragments.16
ticals, and have biological importance9b,12 as substrates of Now, as a continuation of the above studies, we report the
both Mo and V nitrogenases and cyanamide hydrate and as a preparation of the first bis(diethylcyanamide) and bis(cyano-
histamine H2-receptor antagonist.
guanidine) complexes of the iron triad and their reactivity with
Relatively few papers on the synthesis and reactivity of cya- hydrazines, affording new triaza derivatives.
namide and cyanoguanidine complexes of transition metals
have recently been reported,1–8 mainly involving molyb-
denum,7 platinum6 and copper5 as metal centres. There are
Experimental
interesting studies on nucleophilic addition to the metal-acti-
General comments
All reactions were carried out in an inert atmosphere (argon)
aDipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia,
by means of standard Schlenk techniques or in an inert-atmos-
phere glove box. Once isolated, the complexes were found to
be relatively stable in air. All solvents were dried over appropri-
ate drying agents, degassed on a vacuum line, and distilled
into vacuum-tight storage flasks. RuCl3·3H2O and OsO4 were
Dorsoduro 2137, 30123 Venezia, Italy. E-mail: albertin@unive.it
bDepartamento de Química Inorgánica, Universidade de Vigo, Facultade de Química,
Edificio de Ciencias Experimentais, 36310 Vigo (Galicia), Spain
†CCDC 985290. For crystallographic data in CIF or other electronic format see
DOI: 10.1039/c4dt00394b
7314 | Dalton Trans., 2014, 43, 7314–7323
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
Pressure Chemical Co. (USA) products, and used as received. from CH2Cl2 and ethanol; yield ≥80%. (1H NMR (CD2Cl2,
Triethylphosphite P(OEt)3 was an Aldrich product, purified by 25 °C) δ: 7.40–6.94 (m, 40H, Ph), 4.24 (br, 8H, NH + NH2), 4.09,
distillation under nitrogen. Hydrazine NH2NH2 was prepared 3.98 (m, 24H, CH2), 1.32, 1.26 (t, 36H, CH3); (−70 °C) 5.14,
by decomposition of hydrazine cyanurate (Fluka) by following 3.53 (br, 4H, NH), 3.34 (br, 4H, NH2). 31P{1H} NMR (CD2Cl2,
the reported method.17 Other reagents were purchased from 25 °C) δ: A2B2, δA 129.7, δB 121.8, JAB = 59.5. IR (KBr)/cm−1
:
commercial sources in the highest available purity and used as 3440, 3350 (s) νNH; 2247 (s) νCuN; 1631 (s) δNH . ΛM/S cm2
2
received. Infrared spectra were recorded on a Perkin-Elmer mol−1
=
122. Found: C, 59.95; H, 7.04; N, 7.25.
Spectrum-One FT-IR spectrophotometer. NMR spectra were C76H108B2FeN8O12P4 (1527.08) requires C, 59.78; H, 7.13; N,
obtained on an AVANCE 300 Bruker spectrometer (1H, 7.34%.)
300 MHz; 31P, 121.52 MHz; 13C, 75.48 MHz) at temperatures
1
[Ru(NuCNEt2)2{P(OEt)3}4](BPh4)2 2a and [Ru{NuCN(H)-
C(NH2)vNH}2{P(OEt)3}4](BPh4)2 2b
between +20 and −80 °C, unless otherwise noted. H and 13C
{1H} spectra are referenced to internal tetramethylsilane; 31P
{1H} chemical shifts are reported with respect to 85% H3PO4; In a 25 cm3 three-necked round-bottomed flask were placed
downfield shifts are considered positive; J values are given in 0.20 g (0.26 mmol) of RuH2[P(OEt)3]4 and 7 cm3 of toluene. An
Hz. COSY, HMQC and HMBC NMR experiments were per- equimolar amount of triflic acid HOSO2CF3 (HOTf)
formed with standard programs. The iNMR software package18 (0.26 mmol, 23 µL) was added to the solution cooled to
was used to process NMR data. The conductivity of 10−3 mol −196 °C and the reaction mixture brought to room tempera-
dm−3 solutions of the complexes in CH3NO2 at 25 °C was ture and stirred for 1 h. Another equimolar amount of HOTf
measured on a Radiometer CDM 83. Elemental analyses were (0.26 mmol, 23 µL) was further added to the solution cooled to
determined in the Microanalytical Laboratory of the Diparti- −196 °C and the reaction mixture, brought to room tempera-
mento di Scienze del Farmaco, University of Padova (Italy).
ture, stirred for 1 h. An excess of the appropriate cyanamide
NuCNEt2 (0.78 mmol, 90 µL) or NuCNH2 (1.6 mmol, 67 mg)
in ethanol (5 cm3) was added and the resulting solution stirred
Synthesis of complexes
Hydrides RuH2[P(OEt)3]4 and OsH2[P(OEt)3]4 were prepared for 2 h. The solvent was removed under reduced pressure
following the known method.19,20
giving an oil, which was triturated with ethanol (3 cm3) con-
taining an excess of NaBPh4 (0.78 mmol, 0.27 g). A white solid
slowly separated out by cooling the resulting solution to
[Fe(NuCNEt2)2{P(OEt)3}4](BPh4)2 1a
An excess of P(OEt)3 (12.5 mmol, 2.1 cm3) was added to a solu- −25 °C, which was filtered and crystallised from CH2Cl2 and
tion of anhydrous FeCl2 (2.5 mmol, 0.32 g) in 25 cm3 of ethanol; yield ≥65%. (2a: 1H NMR [(CD3)2CO, 25 °C] δ:
ethanol and the reaction mixture refluxed for 90 min. An 7.33–6.70 (m, 40 H, Ph), 4.32, 4.25 (m, 24 H, CH2 phos), 3.37
excess of diethylcyanamide NuCNEt2 (12.5 mmol, 1.45 cm3) (q, 8 H, CH2 NEt), 1.40, 1.38 (t, 36 H, CH3 phos), 1.35 (t, 12 H,
was added to the solution, brought to room temperature and CH3 NEt). 31P{1H} NMR [(CD3)2CO, 25 °C] δ: A2B2, δA 130.0, δB
the mixture stirred for 3 h. The addition of an excess of 120.5, JAB = 60.8. IR (KBr)/cm−1: 2264 (m) νCuN. ΛM/S cm2
NaBPh4 (6.2 mmol, 2.12 g) in ethanol (5 cm3) to the resulting mol−1
=
125. Found: C, 61.31; H, 7.68; N, 3.39.
solution caused the separation of a yellow solid, which was fil- C82H120B2N4O12P4Ru (1600.44) requires C, 61.54; H, 7.56; N,
1
tered and crystallised from dichloromethane CH2Cl2 and 3.50%. 2b: H NMR (CD2Cl2, 25 °C) δ: 7.38–6.86 (m, 40 H, Ph),
ethanol; yield ≥75%. (1H NMR (CD2Cl2, 25 °C) δ: 7.73–6.90 (m, 4.16 (br, 8 H, NH + NH2), 4.03, 3.98 (m, 24 H, CH2), 1.29, 1.26
40H, Ph), 4.16 (s), 4.03 (m) (24H, CH2 phos), 3.88 (q, 8H, CH2 (t, 36 H, CH3); (−30 °C) 4.46 (br, 4 H, NH), 3.65 (br, 4 H, NH2);
NEt), 1.38, 1.30 (t, 36H, CH3 phos), 1.21 (t, 12H, CH3 NEt); 31P (−70 °C) 5.10, 3.56 (br, 4 H, NH), 3.25 (br, 4 H, NH2). 13C{1H}
{1H} NMR (CD2Cl2, 25 °C) δ: A2B2 spin syst, δA 155.4, δB 142.3, NMR (CD2Cl2, 25 °C) δ: 165–122.5 (m, Ph), 162.22 (s, CNH2),
JAB = 142.8. IR (KBr)/cm−1: 2264 (m) νCuN. ΛM/S cm2 mol−1
=
121.9 (t, CuN), 63.10 (m, CH2), 16.41 (m, CH3). 31P{1H} NMR
115. Found: C, 63.48; H, 7.86; N, 3.51. C82H120B2FeN4O12P4 (CD2Cl2, 25 °C) δ: A2B2, δA 131.1, δB 121.7, JAB = 60.8. IR (KBr)/
(1555.21) requires C, 63.33; H, 7.78; N, 3.60%.)
cm−1: 3435, 3356 (s), 3233 (w) νNH; 2246 (s) νCuN; 1630 (s) δNH
.
2
ΛM/S cm2 mol−1 = 119. Found: C, 57.85; H, 6.82; N, 7.26.
[Fe{NuCN(H)C(NH2)vNH}2{P(OEt)3}4](BPh4)2 1b
C76H108B2N8O12P4Ru (1572.30) requires C, 58.06; H, 6.92;
An excess of P(OEt)3 (12.5 mmol, 2.1 cm3) was added to a solu- N, 7.13%.)
tion of anhydrous FeCl2 (2.5 mmol, 0.32 g) in ethanol (15 cm3)
[Os(NuCNEt2)2{P(OEt)3}4](BPh4)2 3a and [Os{NuCN(H)-
C(NH2)vNH}2{P(OEt)3}4](BPh4)2 3b
and the reaction mixture was refluxed for 90 min. An excess of
cyanamide NuCNH2 (12.5 mmol, 0.53 g) in ethanol (5 cm3)
was added to the solution brought to room temperature and An equimolar amount of CH3OSO2CF3 (0.23 mmol, 26 µL) was
the mixture stirred for 3 h. Alternatively, an excess of cyanogua- added to a solution of OsH2[P(OEt)3]4 (0.23 mmol, 0.20 g) in
nidine NuCN(H)C(NH2)vNH (6.0 mmol, 0.50 g) in ethanol toluene (7 cm3) cooled to −196 °C. The reaction mixture was
(5 cm3) was added to the solution brought to room tempera- left to reach the room temperature, stirred for 1 h, and then
ture and the mixture stirred for 3 h. The addition of an excess cooled again to −196 °C. An equimolar amount of HOTf
of NaBPh4 (6.2 mmol, 2.12 g) in ethanol (5 cm3) caused the (0.23 mmol, 20 µL) was added and the reaction mixture
separation of a yellow solid, which was filtered and crystallised brought to room temperature and stirred for 1 h. An excess of
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7314–7323 | 7315

View Article Online
Paper
Dalton Transactions
the appropriate cyanamide NuCNEt2 (0.70 mmol, 81 µL) or [OsH(NuCNEt2){P(OEt)3}4]BPh4 5a and [OsH{NuCN(H)-
NuCNH2 (1.4 mmol, 59 mg) in ethanol (5 cm3) was added and C(NH2)vNH}{P(OEt)3}4]BPh4 5b
the resulting solution stirred for 3 h. The solvent was removed
An equimolar amount of CH3OSO2CF3 (0.23 mmol, 26 µL) was
under reduced pressure giving an oil, which was triturated
added to a solution of OsH2[P(OEt)3]4 (0.23 mmol, 0.20 g) in
with ethanol (3 cm3) containing an excess of NaBPh4
toluene (7 cm3) and cooled to −196 °C. The reaction mixture
(0.70 mmol, 0.24 g). A white solid slowly separated out from
was left to reach the room temperature, stirred for 1 h and
the resulting solution cooled to −25 °C, which was filtered and
then an excess of the appropriate cyanamide NuCNEt2
crystallised from CH2Cl2 and ethanol; yield ≥85%. (3a: 1H
(0.46 mmol, 50 µL) or NuCNH2 (0.92 mmol, 39 mg in 3 cm3 of
NMR (CD2Cl2, 25 °C) δ: 7.32–6.86 (m, 40 H, Ph), 4.10, 4.02 (m,
ethanol) was added. The solution was stirred for 2 h and then
24 H, CH2 phos), 3.09 (q, 8 H, CH2 NEt), 1.34, 1.31 (t, 36 H,
the solvent removed under reduced pressure giving an oil,
CH3 phos), 1.20 (t, 12 H, CH3 NEt). 13C{1H} NMR (CD2Cl2,
which was triturated with ethanol (2 cm3) containing an excess
25 °C) δ: 165–122 (m, Ph), 119.0 (t, CuN), 63.48, 63.29 (t, CH2
of NaBPh4 (0.52 mmol, 0.18 g). A white solid slowly separated
phos), 46.43 (s, CH2 NEt), 16.45, 16.26 (t, CH3 phos), 113.64 (s,
out by cooling the resulting solution to −25 °C, which was fil-
CH3 NEt). 31P{1H} NMR (CD2Cl2, 25 °C) δ: A2B2, δA 82.5, δB
75.7, JAB = 44.0. IR (KBr)/cm−1: 2275 (m) νCuN. ΛM/S cm2 mol−1
= 120. Found: C, 58.11; H, 7.28; N, 3.24. C82H120B2N4O12OsP4
(1689.60) requires C, 58.29; H, 7.16; N, 3.32%. 3b: 1H NMR
[(CD3)2CO, 25 °C] δ: 7.34–6.78 (m, 40 H, Ph), 4.27, 4.17 (m,
24 H, CH2), 4.20 (br, 8 H, NH+NH2), 1.37, 1.34 (t, 36 H, CH3);
(CD2Cl2, −30 °C) 4.49 (br, 4 H, NH), 3.66 (br, 4 H, NH2);
(CD2Cl2, −70 °C) 4.96, 3.52 (br, 4 H, NH), 3.19 (br, 4 H, NH2).
1
tered and crystallised from ethanol; yield ≥73%. (5a: H NMR
[(CD3)2CO, 25 °C] δ: 7.34–6.78 (m, 20 H, Ph), 4.10 (m), 3.97
(qnt) (24 H, CH2 phos), 3.21 (q, 4 H, CH2 NEt), 1.31, 1.30, 1.28
(t, 36 H, CH3 phos), 1.25 (t, 6 H, CH3 NEt), −8.92 to −9.48 (m,
1 H, OsH). 31P{1H} NMR [(CD3)2CO, 25 °C] δ: AB2C, δA 107.7, δB
106.2, δC 97.0, JAB = 31.7, JAC = 29.3, JBC = 43.2. IR (KBr)/cm−1
:
2275 (s) νCuN; 1945 (m) νOsH. ΛM/S cm2 mol−1 = 56. Found: C,
49.82; H, 7.08; N, 2.31. C53H91BN2O12OsP4 (1273.23) requires
31P{1H} NMR (CD2Cl2, −70 °C) δ: A2B2, δA 88.5, δB 79.8, JAB
=
;
1
C, 50.00; H, 7.20; N, 2.20%. 5b: H NMR [(CD3)2CO, 25 °C] δ:
43.5. IR (KBr)/cm−1: 3447, 3351, 3239 (s) νNH; 2256 (s) νCuN
7.34–6.77 (m, 20 H, Ph), 4.23 (br, 4 H, NH + NH2), 4.21 (m),
3.96 (qnt) (24 H, CH2) 1.28, 1.27, 1.23 (t, 36 H, CH3), −8.92 to
−9.47 (m, 1 H, RuH); (CD2Cl2, −70 °C) 5.36 (br, 2 H, NH), 2.89
(br, 2 H, NH2). 31P{1H} NMR [(CD3)2CO, 25 °C] δ: AB2C, δA
109.0, δB 107.3, δC 98.4, JAB = 30.4, JAC = 29.5, JBC = 41.9. IR
1633 (s) δNH . ΛM/S cm2 mol−1 = 117. Found: C, 55.17; H, 6.42;
2
N, 6.63. C76H108B2N8O12OsP4 (1661.46) requires C, 54.94;
H, 6.55; N, 6.74%.)
[RuH(NuCNEt2){P(OEt)3}4]BPh4 4a and [RuH{NuCN(H)-
C(NH2)vNH}{P(OEt)3}4]BPh4 4b
(KBr)/cm−1: 3423, 3390 (s) νNH; 2253 (s) νCuN; 1950 (m) νOsH
;
1640 (s) δNH . ΛM/S cm2 mol−1 = 53. Found: C, 47.76; H, 6.72;
2
An equimolar amount of HOTf (0.26 mmol, 23 µL) was added
to a solution of RuH2[P(OEt)3]4 (0.26 mmol, 0.20 g) in toluene
(7 cm3) cooled to −196 °C and the reaction mixture brought to
room temperature and stirred for 1 h. An excess of the appro-
priate cyanamide NuCNEt2 (0.52 mmol, 60 µL) or NuCNH2
(1.04 mmol, 44 mg in 3 cm3 of ethanol) was added and the
N, 4.53. C50H85BN4O12OsP4 (1259.17) requires C, 47.69; H,
6.80; N, 4.45%.)
[Fe{η2-NHvC(NEt2)N(R)NH2}{P(OEt)3}4](BPh4)2 6a–8a
(R = H 6, Me 7, Ph 8)
resulting solution stirred for 2 h. The solvent was removed An excess of the appropriate hydrazine RNHNH2 (0.36 mmol)
under reduced pressure giving an oil, which was triturated was added to a solution of bis(cyanamide) complex 1a
with ethanol (2 cm3) containing an excess of NaBPh4 (0.13 mmol, 0.20 g) in CH2Cl2 (5 cm3) cooled to −196 °C. The
(0.52 mmol, 0.18 g). A white solid slowly separated out by reaction mixture was left to reach the room temperature and
cooling the resulting solution to −25 °C, which was filtered stirred for 4 h. The solvent was removed under reduced
and crystallised from ethanol; yield ≥75%. (4a: 1H NMR pressure to give an oil, which was triturated with ethanol
[(CD3)2CO, 25 °C] δ: 7.34–6.78 (m, 20 H, Ph), 4.25 (m, 24 H, (2 cm3) containing an excess of NaBPh4 (0.42 mmol, 0.14 g). A
CH2 phos), 3.56 (q, 4 H, CH2 NEt), 1.38, 1.32 (t, 36 H, CH3 white solid slowly separated out by cooling the resulting solu-
phos), 1.32 (t, 6 H, CH3 NEt), −7.9 to −8.6 (m, 1 H, RuH). 31P tion to −25 °C, which was filtered and crystallised from
1
{1H} NMR [(CD3)2CO, 25 °C] δ: ABC2, δA 151.9, δB 149.5, δC CH2Cl2 and ethanol; yield ≥78%. (6a: H NMR (CD2Cl2, 25 °C)
140.4, JAB = 63.4, JAC = 46.1, JBC = 42.5. IR (KBr)/cm−1 2257 (s): δ: 7.34–6.91 (m, 40 H, Ph), 5.38 (t br, 2 H, NH2), 4.05 (m, 24 H,
νCuN. ΛM/S cm2 mol−1 = 53. Found: C, 53.54; H, 7.62; N, 2.45. CH2 phos), 3.06 (qnt, 1 H, vNH), 2.87 (q, 4 H, CH2 NEt), 1.35,
C53H91BN2O12P4Ru (1184.07) requires C, 53.76; H, 7.75; N, 1.33 (t, 36 H, CH3 phos), 1.01 (t, 6 H, CH3 NEt). 31P{1H} NMR
1
2.37%. 4b: H NMR (CD2Cl2, 25 °C) δ: 7.36–6.87 (m, 20 H, Ph), (CD2Cl2, 25 °C) δ: ABC2, δA 164.1, δB 162.5, δC 142.0, JAB
=
4.15 (m, 4 H, NH+NH2), 3.99 (m), 3.88 (qnt) (24 H, CH2) 1.29, 116.4, JAC = 147.6, JBC = 120.3. IR (KBr)/cm−1: 3434, 3378 (s)
1.26, 1.19 (t, 36 H, CH3), −8.0 to −8.4 (m, 1 H, RuH). 31P{1H} νNH; 1619, 1603 (s) νCvN, δNH . ΛM/S cm2 mol−1 = 128. Found:
2
NMR (CD2Cl2, 25 °C) δ: ABC2, δA 150.35, δB 147.15, δC 143.5, C, 61.87; H, 7.60; N, 3.72. C77H114B2FeN4O12P4 (1489.11)
JAB = 61.1, JAC = 43.9, JBC = 40.6. IR (KBr)/cm−1: 3429, 3378, requires C, 62.11; H, 7.72; N, 3.76%. 7a: 1H NMR (CD2Cl2,
3334 (s) νNH; 2253 (s) νCuN; 1631 (s) δNH . ΛM/S cm2 mol−1
=
25 °C) δ: 7.34–6.89 (m, 40 H, Ph), 5.62 (t, 2 H, NH2), 4.06 (m,
2
59. Found: C, 51.18; H, 7.19; N, 4.67. C50H85BN4O12P4Ru 24 H, CH2 phos), 3.86 (s br, 1 H, vNH), 3.05 (q, 4 H, CH2
(1170.01) requires C, 51.33; H, 7.32; N, 4.79%.)
NEt), 2.89 (s, 3 H, CH3N), 1.34, 1.33 (t, 36 H, CH3 phos), 1.16
7316 | Dalton Trans., 2014, 43, 7314–7323
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
(t, 6 H, CH3 NEt). 31P{1H} NMR (CD2Cl2, 25 °C) δ: ABC2, δA Ph), 5.70 (q br, 2 H, NH2), 4.33 (br, 1 H, NH), 4.05 (m, 24 H,
163.2, δB 162.1, δC 141.7, JAB = 112.8, JAC = 147.6, JBC = 119.7. IR CH2 phos), 3.04 (q, 4 H, CH2 NEt), 2.87 (s, 3 H, CH3N), 1.34,
(KBr)/cm−1: 3310, 3299 (w) νNH; 1616 (s) νCvN, δNH . ΛM/S cm2 1.33, 1.31 (t, 36 H, CH3 phos), 1.15 (t, 6 H, CH3 NEt). 31P{1H}
2
mol−1
=
124. Found: C, 62.54; H, 7.67; N, 3.78. NMR (CD2Cl2, 25 °C) δ: ABC2, δA 134.3, δB 133.1, δC 118.7, JAB =
C78H116B2FeN4O12P4 (1503.14) requires C, 62.33; H, 7.78; N, 72.4, JAC = 63.5, JBC = 57.3. IR (KBr)/cm−1: 3429 (m), 3395, 3295
3.73%. 8a: H NMR (CD2Cl2, 25 °C) δ: 7.32–6.87 (m, 45 H, Ph), (w) νNH; 1613 (s) νCvN, δNH . ΛM/S cm2 mol−1 = 121. Found: C,
1
2
5.04 (br, 2 H, NH2), 4.76 (br, 1 H, NH), 4.15, 4.03 (m, 24 H, 60.34; H, 7.60; N, 3.50. C78H116B2N4O12P4Ru (1548.36) requires
CH2 phos), 3.07 (br, 4 H, CH2 NEt), 1.31 (m, 36 H, CH3 phos), C, 60.50; H, 7.55; N, 3.62%.)
1.20 (br, 6 H, CH3 NEt). 31P{1H} NMR (CD2Cl2, 25 °C) δ: ABC2,
[Ru{η2-NHvC[NvC(NH2)2]N(Me)NH2}{P(OEt)3}4](BPh4)2 10b
δA 148.7, δB 143.4, δC 134.0, JAB = 140.0, JAC = 126.5, JBC = 142.0.
IR (KBr)/cm−1: 3429, 3387 (m) νNH. ΛM/S cm2 mol−1 = 122.
This compound was prepared exactly like the related 10a start-
Found: C, 63.46; H, 7.58; N, 3.45. C83H118B2FeN4O12P4
ing from bis(cyanoguanidine) complex 2b and using methyl-
(1565.21) requires C, 63.69; H, 7.60; N, 3.58%.)
hydrazine as a reagent; yield ≥65%. (1H NMR (CD2Cl2, 25 °C)
[Fe{η2-NHvC[NvC(NH2)2]NHNH2}{P(OEt)3}4](BPh4)2 6b and
δ: 7.35–6.90 (m, 40 H, Ph), 5.62 (q, 2 H, NH2N), 4.02 (m, 24 H,
[Fe{η2-NHvC[NvC(NH2)2]N(Me)NH2}{P(OEt)3}4](BPh4)2 7b
CH2), 3.78 (br, 4 H, NH2C), 3.05 (s, 3 H, CH3N), 1.32, 1.30 (t,
36 H, CH3 phos). 13C{1H} NMR (CD2Cl2, 25 °C) δ: 165–122 (m,
The complexes were prepared like the related 6a, 7a by reacting
Ph), 164.04 (s, CvNH), 63.35, 60.0 (m, CH2), 40.58 (s, CH3N),
bis(cyanoguanidine) complex 1b with the appropriate hydra-
16.34 (m, CH3 phos). 31P{1H} NMR (CD2Cl2, 25 °C) δ: ABC2, δA
zine RNHNH2 for 5 h; yield ≥60%. (6b: 1H NMR (CD2Cl2,
135.6, δB 133.2, δC 119.2, JAB = 70.6, JAC = 63.3, JBC = 57.1. IR
25 °C) δ: 7.35–6.92 (m, 40 H, Ph), 5.32 (t, 2 H, NH2N), 4.00 (m,
(KBr)/cm−1: 3445, 3357 (s) νNH; 1635, 1617 (s) νCvN, δNH . ΛM/S
2
24 H, CH2), 3.84 (br, 4 H, NH2C), 2.23 (br, 1 H, NH), 1.31 (t br,
cm2 mol−1
= 125. Found: C, 58.58; H, 7.35; N, 5.37.
36 H, CH3). 31P{1H} NMR (CD2Cl2, 25 °C) δ: ABC2, δA 162.0, δB
159.4, δC 143.3, JAB = 114.3, JAC = 121.3, JBC = 134.9. IR (KBr)/
C75H110B2N6O12P4Ru (1534.30) requires C, 58.71; H, 7.23; N,
5.48%.)
cm−1: 3434, 3400, 3366 (s), 3320 (w) νNH; 1626 (s) νCvN, δNH
.
2
ΛM/S cm2 mol−1 = 120. Found: C, 60.12; H, 7.51; N, 5.58.
[Os{η2-NHvC(NEt2)NHNH2}{P(OEt)3}4](BPh4)2 11a and [Os{η2-
NHvC(NEt2)N(Me)NH2}{P(OEt)3}4](BPh4)2 12a
C74H108B2FeN6O12P4 (1475.04) requires C, 60.26; H, 7.38; N,
1
5.70%. 7b: H NMR (CD2Cl2, 25 °C) δ: 7.36–6.91 (m, 40 H, Ph),
5.47 (t, 2 H, NH2N), 4.03 (m, 24 H, CH2), 3.87 (br, 4 H, NH2C), An excess of the appropriate hydrazine RNHNH2 (0.36 mmol)
3.42 (br, 1 H, NH), 3.01 (s, 3 H, CH3N), 1.30 (t, 36 H, CH3 was added to a solution of bis(cyanamide) complex 3a
phos). 31P{1H} NMR (CD2Cl2, 25 °C) δ: ABC2, δA 164.5, δB 162.7, (0.12 mmol, 0.20 g) in 1,2-dichloroethane (7 cm3) and the reac-
δC 142.7, JAB = 114.0, JAC = 146.5, JBC = 115.6. IR (KBr)/cm−1
:
.
tion mixture refluxed for 1 h. The solvent was removed under
reduced pressure to give an oil, which was triturated with
3412, 3378, 3345 (s), 3340 (w) νNH; 1627, 1614 (s) νCvN, δNH
2
ΛM/S cm2 mol−1 = 128. Found: C, 60.35; H, 7.37; N, 5.61. ethanol (2 cm3) containing an excess of NaBPh4 (0.36 mmol,
C75H110B2FeN6O12P4 (1489.07) requires C, 60.49; H, 7.45; N, 0.12 g). By cooling the resulting solution to −25 °C, a white
5.64%.)
solid slowly separated out which was filtered and crystallised
from CH2Cl2 and ethanol; yield ≥70%. (11a: H NMR (CD2Cl2,
25 °C) δ: 7.32–6.89 (m, 40 H, Ph), 5.84 (m br, 2 H, NH2), 5.58
(m br, 1 H, NH), 4.03 (m, 24 H, CH2 phos), 3.85 (m, 1 H, NH),
1
[Ru{η2-NHvC(NEt2)NHNH2}{P(OEt)3}4](BPh4)2 9a and [Ru{η2-
NHvC(NEt2)N(Me)NH2}{P(OEt)3}4](BPh4)2 10a
An excess of the appropriate hydrazine RNHNH2 (0.30 mmol) 2.79 (q, 4 H, CH2 NEt), 1.33, 1.32, 1.30 (t, 36 H, CH3 phos),
was added to a solution of bis(cyanamide) complex 2a 0.98 (t, 6 H, CH3 NEt). 13C{1H} NMR (CD2Cl2, 25 °C) δ: 165–122
(0.12 mmol, 0.20 g) in 1,2-dichloroethane (7 cm3) and the reac- (m, Ph), 159.37 (s, CvNH), 63.46 (m, CH2 phos), 46.44 (s, CH2
tion mixture refluxed for 30 min. The solvent was removed NEt), 16.45, 16.31, 16.26 (t, CH3 phos), 13.65 (s, CH3 NEt). 31P
under reduced pressure to give an oil, which was triturated {1H} NMR (CD2Cl2, 25 °C) δ: ABC2, δA 86.6, δB 83.3, δC 83.0, JAB
with ethanol (2 cm3) containing an excess of NaBPh4 = 40.1, JAC = 42.0, JBC = 38.9. IR (KBr)/cm−1: 3435 (m), 3306,
(0.36 mmol, 0.12 g). By cooling the resulting solution to 3260 (w) νNH; 1628, 1605 (s) νCvN, δNH . ΛM/S cm2 mol−1 = 122.
2
−25 °C, a white solid slowly separated out which was filtered Found: C, 56.76; H, 7.17; N, 3.36. C77H114B2N4O12OsP4
1
and crystallised from CH2Cl2 and ethanol; yield ≥65%. (9a: H (1623.50) requires C, 56.96; H, 7.08; N, 3.45%. 12a: 1H NMR
NMR (CD2Cl2, 25 °C) δ: 7.33–6.87 (m, 40 H, Ph), 6.14 (br, 1 H, (CD2Cl2, 25 °C) δ: 7.33–6.88 (m, 40 H, Ph), 6.20 (br, 2 H, NH2),
NH), 5.54 (q br, 2 H, NH2), 4.04 (m, 24 H, CH2 phos), 3.45 (m, 5.08 (br, 1 H, NH), 4.03 (m, 24 H, CH2 phos), 3.05 (m, 4 H,
1 H, NH), 2.92 (q, 4 H, CH2 NEt), 1.34, 1.33, 1.31 (t, 36 H, CH3 CH2 NEt), 2.78 (s, 3 H, CH3N), 1.33, 1.31, 1.29 (t, 36 H, CH3
phos), 1.05 (t, 6 H, CH3 NEt). 31P{1H} NMR (CD2Cl2, 25 °C) δ: phos), 1.14 (t, 6 H, CH3 NEt). 31P{1H} NMR (CD2Cl2, 25 °C) δ:
ABC2, δA 135.1, δB 133.7, δC 119.3, JAB = 72.7, JAC = 63.4, JBC
=
,
ABC2, δA 85.9, δB 82.6, δC 82.4, JAB = 41.8, JAC = 41.1, JBC = 41.0.
57.6. IR (KBr)/cm−1: 3429, 3311 (m) νNH; 1617, 1598 (s) νCvN
IR (KBr)/cm−1: 3434 (m), 3283 (w) νNH; 1614 (s) νCvN, δNH . ΛM/
2
δNH . ΛM/S cm2 mol−1 = 116. Found: C, 60.43; H, 7.37; N, 3.58. S cm2 mol−1 = 118. Found: C, 57.00; H, 7.22; N, 3.49.
2
C77H114B2N4O12P4Ru (1534.34) requires C, 60.28; H, 7.49; N, C78H116B2N4O12OsP4 (1637.52) requires C, 57.21; H, 7.14; N,
3.65%. 10a: 1H NMR (CD2Cl2, 25 °C) δ: 7.34–6.86 (m, 40 H, 3.42%.)
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7314–7323 | 7317

View Article Online
Paper
Dalton Transactions
[Os{η2-NHvC[NvC(NH2)2]N(Me)NH2}{P(OEt)3}4](BPh4)2 12b
Table 1 Crystal data and structure refinement
This compound was prepared exactly like the related 11a start-
ing from bis(cyanoguanidine) complex 3b and using methyl-
hydrazine as a reagent; yield ≥65%. (1H NMR (CD2Cl2, 25 °C)
δ: 7.36–6.91 (m, 40 H, Ph), 6.17 (q, 2 H, NH2N), 4.39 (s, 1 H,
NH), 4.04 (m, 24 H, CH2), 3.78 (s br, 4 H, NH2C), 3.03 (s, 3 H,
CH3N), 1.30, 1.29 (t, 36 H, CH3 phos). 31P{1H} NMR (CD2Cl2,
25 °C) δ: ABC2, δA 87.1, δB 83.6, δC 82.4, JAB = 40.7, JAC = 40.0,
JBC = 44.1. IR (KBr)/cm−1: 3440, 3402, 3355 (s) νNH; 1628, 1620
Identification code
Empirical formula
Formula weight
Temperature
Wavelength
Crystal system
Space group
12b
C75H110B2N6O12P4Os
1623.39
293(2) K
0.71073 Å
Orthorhombic
P212121
a = 17.0333(13) Å
b = 20.4889(16) Å
c = 24.4972(19) Å
α = 90°
Unit cell dimensions
(s) νCvN, δNH . ΛM/S cm2 mol−1 = 123. Found: C, 55.33; H, 6.75;
2
β = 90°
N, 5.07. C75H110B2N6O12OsP4 (1623.46) requires C, 55.49; H,
6.83; N, 5.18%.)
γ = 90°
Volume
Z
Density (calculated)
Absorption coefficient
F(000)
Crystal size
Θ Range for data collection
Index ranges
8549.4(11) Å3
4
1.261 Mg m−3
X-ray crystallography
1.623 mm−1
Crystallographic data were collected on a Bruker Smart 1000
CCD diffractometer at CACTI (Universidade de Vigo) using
graphite monochromated Mo-Kα radiation (λ = 0.71073 Å), and
were corrected for Lorentz and polarisation effects. The soft-
ware SMART21 was used for collecting frames of data, indexing
reflections, and the determination of lattice parameters,
SAINT22 for integration of intensity of reflections and scaling,
and SADABS23 for empirical absorption correction.
The crystallographic treatment was performed with the
Oscail program.24 The structure was solved by direct methods
and refined by full-matrix least-squares based on F2.25 Non-
hydrogen atoms were refined with anisotropic displacement
parameters. Hydrogen atoms were included in idealised posi-
tions and refined with isotropic displacement parameters.
Unfortunately, the quality of the best crystal obtained is
limited, and values of 9.6% for R(int) and 14.6% for R(σ) were
obtained. However, there is no doubt about the correct assign-
ment of the atoms. Details of crystal data and structural refine-
ment are given in Table 1, selected bond lengths and angles
are shown in Table 2. CCDC 985290 contains the supplemen-
tary crystallographic data for this paper.
3376
0.36 × 0.15 × 0.14 mm
1.30 to 28.04°
−22 ≤ h ≤ 21
−27 ≤ k ≤ 27
−31 ≤ l ≤ 18
57 250
20361, [R(int) = 0.0964]
9855
0.994
Semi-empirical from equivalents
0.7456 and 0.6536
Full-matrix least-squares on F2
20 361/0/914
0.954
Reflections collected
Independent reflections
Reflections observed (>2σ)
Data completeness
Absorption correction
Max. and min. transmission
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I > 2σ(I)]
R indices (all data)
Absolute structure parameter
Largest diff. peak and hole
R1 = 0.0509, R2 = 0.0870
R1 = 0.1590, wR2 = 0.1185
−0.016(7)
1.288 and −1.396 (e Å−3
)
Table 2 Selected bond lengths [Å] and angles [°] for 12b
Os–N(3)
Os–P(1)
Os–P(2)
N(1)–N(2)
N(2)–C(2)
C(1)–N(4)
C(4)–N(5)
2.113(5)
2.249(2)
2.327(2)
1.428(7)
1.436(8)
1.346(8)
1.357(12)
Os–N(1)
Os–P(3)
Os–P(4)
N(2)–C(1)
C(1)–N(3)
N(4)–C(4)
C(4)–N(6)
2.162(5)
2.2710(18)
2.337(2)
1.371(9)
1.300(8)
1.291(11)
1.364(12)
Results and discussion
Preparation of bis(cyanamide) complexes of Fe
N(3)–Os–N(1)
N(1)–Os–P(3)
N(3)–Os–P(2)
P(1)–Os–P(2)
N(3)–Os–P(4)
P(1)–Os–P(4)
N(1)–Os–P(1)
P(2)–Os–P(4)
C(1)–N(2)–N(1)
N(1)–N(2)–C(2)
N(3)–C(1)–N(2)
C(1)–N(3)–Os
N(4)–C(4)–N(5)
N(5)–C(4)–N(6)
75.7(2)
N(3)–Os–P(1)
P(1)–Os–P(3)
N(1)–Os–P(2)
P(3)–Os–P(2)
N(1)–Os–P(4)
P(3)–Os–P(4)
N(3)–Os–P(3)
N(2)–N(1)–Os
C(1)–N(2)–C(2)
N(3)–C(1)–N(4)
N(4)–C(1)–N(2)
C(4)–N(4)–C(1)
N(4)–C(4)–N(6)
94.07(16)
98.90(8)
87.72(16)
95.02(7)
87.64(16)
92.77(8)
166.99(16)
112.0(4)
124.7(6)
126.9(7)
114.6(7)
123.0(9)
118.4(11)
91.28(14)
85.57(15)
91.68(8)
85.84(15)
91.53(8)
169.81(15)
171.02(7)
116.2(5)
119.0(6)
118.5(6)
117.5(5)
123.9(9)
117.6(11)
Iron(II) bis(diethylcyanamide) complex [Fe(NuCNEt2)2L4]-
(BPh4)2 1a [L = P(OEt)3] was prepared by reacting anhydrous
iron(II) chloride first with an excess of phosphite and then
with an excess of cyanamide, as shown in Scheme 1.
The reaction of iron(II) chloride with phosphites was
reported26 to give a mixture of complexes, in which [FeClL5]+
and FeCl2L4 were predominant. The substitution of Cl− and/or
L by NuCNEt2 in these intermediates afforded the bis(diethyl-
cyanamide) cation 1a, which was isolated as the BPh4 salt and
characterised.
Cyanamide NuCNH2 also reacted with phosphite-contain-
ing iron(II) complexes, but yielded the bis(cyanoguanidine)
derivative [Fe{NuCN(H)C(NH2)vNH}2L4](BPh4)2 1b (Scheme 2).
The formation of this complex is not very surprising, owing
to the known ease of dimerizing of NuCNH2, affording
cyanoguanidine, which acts as a ligand in the complex.
Dimerisation16 may be promoted by the coordination of one
cyanamide [Fe]–NuCNH2 followed by nucleophilic attack on
its CuN carbon atom of a second cyanamide affording, after
tautomerisation, a N-bonded imine-cyanoguanidine complex
[Fe]–N(H)vC(NH2)N(H)CuN. The linkage isomerisation of
7318 | Dalton Trans., 2014, 43, 7314–7323
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
with HOTf, yielding the cation [Ru(κ2-O2SOCF3)L4]+ [B]. Substi-
tution of the κ2-O2SOCF3 ligand with the appropriate
NuCNR1R2 in [B] afforded bis(diethylcyanamide) 2a and bis-
(cyanoguanidine) 2b derivatives.
A slight modification of this method was necessary to
prepare osmium cyanamide complexes, involving treatment of
OsH2L4 first with methyl triflate, then with triflic acid and
lastly with an excess of the appropriate cyanamide, affording
bis(diethylcyanamide) [Os(NuCNEt2)2L4](BPh4)2 3a and bis-
(cyanoguanidine) [Os{NuCN(H)C(NH2)vNH}2L4](BPh4)2 3b
derivatives (Scheme 3). Methyl triflate MeOTf reacted with
OsH2L4, with the evolution of methane and formation15a,28 of
OsH(κ1-OTf)L4 [A], which further reacted with HOTf, yielding
the cation [Os(κ2-O2SOCF3)L4]+ [B]. Methyl triflate was used
instead of triflic acid in the case of osmium, due to the stabi-
lity of the η2-H2 intermediate [OsH(η2-H2)L4]+,27,28 which pre-
vents formation of the key-intermediate [Os(κ2-O2SOCF3)L4]+,
yielding the final derivatives 3a and 3b.
Scheme 1 L = P(OEt)3.
Scheme 2 L = P(OEt)3.
this ligand gave the N-nitrile-bonded derivative. The same
As observed for iron, the reaction with cyanamide NuCNH2
complex 1b was in fact prepared by reacting iron(II) chloride of triflate intermediates of both Ru and Os afforded cyanogua-
first with phosphite and then with an excess of cyanoguani- nidine derivatives 2b and 3b through dimerisation of the
dine, as shown in Scheme 2.
NuCNH2 species. The same bis(cynoguanidine) complexes
were also obtained with NuCN(H)C(NH2)vNH as a reagent.
Bis(cyanamide) and bis(cyanoguanidine) complexes of tran-
sition metals are very rare and have only been described for
nickel and copper triads.1,6f The use of tetrakis(phosphite)
fragments [M{P(OEt)3}4]2+ allowed the synthesis of the first
examples of bis(cyanamide) derivatives of the iron triad.
Dihydride complexes MH2L4 were used to prepare bis-
(cyanamide) complexes 2 and 3, and prompted us also to
prepare mono-cyanamide [MH(NuCNEt2)L4]BPh4 4a, 5a and
mono-cyanoguanidine derivatives [MH{NuCN(H)C(NH2)v
NH}2L4]BPh4 4b, 5b by reacting hydride-triflate species MH-
(κ1-OTf)L4 [A] with an excess of the appropriate cyanamide, as
shown in Scheme 4. The reaction proceeded quickly, with sub-
stitution of the triflate ligand and formation of cyanamide
cations 4 and 5, which were isolated as BPh4 salts in good
yields.
Preparation of bis(cyanamide) complexes of Ru and Os
The easy synthesis of iron complexes 1a and 1b prompted us
to extend the study to ruthenium and osmium, but a different
route had to be followed for them, involving dihydrides MH2L4
as precursors.
Sequential treatment of RuH2L4 first with one equivalent of
triflic acid, then with another, and lastly with an excess of the
appropriate cyanamide, afforded bis(diethylcyanamide) [Ru-
(NuCNEt2)2L4](BPh4)2 2a and bis(cyanoguanidine) [Ru{NuCN
(H)C(NH2)vNH}2L4](BPh4)2 2b derivatives, which were isolated
in good yields and characterised (Scheme 3). The reaction of
RuH2L4 with HOTf proceeded15c,27 with the evolution of H2
and formation of RuH(κ1-OTf)L4 [A], which further reacted
Characterisation of cyanamide derivatives
Good analytical data were obtained for both mono-
[MH(NuCNR1R2)L4]BPh4 4,
5 and bis(cyanamide)/(cyano-
Scheme 3 M = Ru 2, Os 3; X = H for Ru, Me for Os; L = P(OEt)3.
Scheme 4 M = Ru 4, Os 5; L = P(OEt)3.
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7314–7323 | 7319

View Article Online
Paper
Dalton Transactions
guanidine) complexes [M(NuCNR1R2)2L4](BPh4)2 1–3, which nitrogenous ligands, showing the signals of ethyl substituents
were all isolated as white or yellow solids stable in air and in for NuCNEt2 compounds 4a and 5a, whereas three broad
solution of polar organic solvents, in which they behave as 1 : 1 signals at 5.36–2.89 ppm, attributable to the NH and NH2 of
(4, 5) or 2 : 1 (1–3) electrolytes.29 Infrared and NMR data cyanoguanidine, were observed in the low-temperature spec-
support the proposed formulations for the complexes, which trum (−70 °C) of 5b. A low-frequency multiplet between −7.90
were also indirectly confirmed by X-ray crystal structure and −9.48 ppm, due to hydride resonance, was also observed
determinations of complex 12b (see below).
in the spectra of complexes 4 and 5. In the temperature range
The IR spectra of bis(diethylcyanamide) complexes +20 to −80 °C, the 31P NMR spectra of complexes were either
[M(NuCNEt2)2L4](BPh4)2 1a–3a showed one medium-intensity ABC2 or AB2C multiplets, indicating that the hydride and
band at 2275–2264 cm−1, attributed to the νCN of the cyan- cyanamide or cyanoguanidine ligands were in a mutually cis
amide ligands. The presence of only one band indicates that position, as in geometry II (Scheme 4).
the two NuCNEt2 ligands are in a mutually trans position.
However, this hypothesis contrasted with 31P NMR spectra
Reactivity with hydrazine
Bis(diethylcyanamide) [M(NuCNEt2)2L4]2+ 1a–3a and bis-
(cyanoguanidine) complexes [M{NuCN(H)C(NH2)vNH}2L4]2+
1b–3b reacted with hydrazines RNHNH2 to give white solids,
characterised as the hydrazinecarboximidamide complexes
[M{η2-N(H)vC(NEt2)N(R)NH2}L4](BPh4)2 6a–12a and [M{η2-
N(H)vC[NvC(NH2)2]N(R)NH2}L4](BPh4)2 6b–12b (Schemes 5
and 6).
which, in the temperature range +20 to −80 °C, were sym-
metric A2B2 multiplets, indicating the presence of two-by-two
magnetically equivalent phosphine ligands. On this basis,
cis geometry I can be proposed for bis(diethylcyanamide) com-
plexes 1a, 2a and 3a. The expected two absorptions in the IR
spectra for the νCN of the cis-cyanamide may have such close
values that the instrument detected only one signal, with a
slightly broad band.
The IR spectra of bis(cyanoguanidine) complexes
[M{NuCN(H)C(NH2)vNH}2L4](BPh4)2 1b–3b showed either
three or four bands of medium to weak intensity in the region
3447–3233 cm−1, attributed to the νNH of the cyanoguanidine
ligands. One medium-intensity band also appeared at
2256–2246 cm−1 and was attributed to the νCN of the same
ligands. The presence of only one band indicated that the cyano-
guanidine ligands were present in the amine form. A strong
absorption at 1633–1630 cm−1 was also seen in the IR spectra,
The formation of azametallocycle30 compounds 6–12 may
be explained (Scheme 7) through substitution of one cyana-
mide by RNHNH2 giving the [M(NuCNR1R2)(RNHNH2)L4]2+
intermediate [C], in which one end of the hydrazine can attack
due to the δNH of the nitrogenous ligand. Also in this case, the
2
IR instrument probably did not resolve the νCN absorptions,
showing only one slightly broad band at 2256–2246 cm−1 for
the two cis-cyanamide ligands. At room temperature, the 1H
NMR spectra of cyanoguanidine complexes 1b, 2b and 3b
Scheme 5 M = Fe 6–8, Ru 9, 10, Os 11, 12; R = H 6, 9, 11, Me 7, 10, 12,
Ph 8; L = P(OEt)3.
−
showed the characteristic signals of phosphites and BPh4
anions, and a broad signal between 4.16 and 4.24 ppm attribu-
table to either NH2 or NH protons of the cyanoguanidine.
However, lowering the sample temperatures changed the pro-
files of the spectra and, at −70 °C, three broad signals
appeared between 5.14 and 3.19 ppm, with an intensity ratio
of about 1 : 1 : 2, which were attributed to the NH and NH2
protons of the cyanoguanidine ligands. In the 13C NMR spec-
trum of 2b, a singlet at 162.2 ppm was attributed to the amine
–C(NH2)vNH carbon resonance and a triplet at 121.9 ppm to
the nitrile one, fitting the proposed formulation for the com-
plexes. In the temperature range +20 to −80 °C, the 31P NMR
spectra of complexes 1b, 2b and 3b were A2B2 multiplets, indi-
cating the mutually cis position of the two cyanoguanidine
ligands (geometry I, Scheme 2).
Scheme 6 M = Fe 6, 7, Ru 9, 10, Os 11, 12; R = H 6, 9, 11, Me 7, 10, 12;
L = P(OEt)3.
The IR spectra of hydride–diethylcyanamide complexes
[MH(NuCNEt2)L4]BPh4 4a, 5a showed the νCN band at
2275–2264 cm−1, whereas those of hydride-cyanoguanidine
derivatives [MH{NuCN(H)C(NH2)vNH}L4]BPh4 4b, 5b showed
νNH absorptions between 3429 and 3334 cm−1 and νCN at
2253 cm−1. The 1H NMR spectra confirmed the presence of the Scheme 7 L = P(OEt)3.
7320 | Dalton Trans., 2014, 43, 7314–7323
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
the carbon atom of the coordinate cyanamide giving the five- angle of 75.7(2)°. The overall geometry may be described as a
membered azametallocycle. Direct nucleophilic attack at slightly distorted octahedron. Another source of distortion in
the CN group of one cyanamide or cyanoguanidine, the octahedron, apart from the bite angle, is the slight bend of
yielding η1-hydrazinecarboximidamide [D] in Scheme 7, the mutually trans phosphorus atoms toward the N,N′-biden-
should be ruled out insofar as the bifunctional nucleophile tate ligand, no doubt due to the steric requirements of phos-
RNHNH2 cannot attack the
encumbered end.
C
atom by more sterically phites. Botheffects give trans anglesfrom 166.99(16) to171.02(7)°,
more than 10° deviated from regularity on average. The
Nucleophilic attack on coordinate dialkyl cyanamide or cyano- four phosphites are in two groups, those mutually trans, with
guanidine has been reported with amine, imine or alcohol Os–P bond lengths of 2.337(2) and 2.327(2) Å, and those trans
groups,6f,g,13,31 but none with hydrazine. The coordination of to the nitrogen atoms, with slightly shorter Os–P bond
two NuCNR1R2 groups to the tetrakis(phosphite) fragment lengths, 2.249(2) and 2.2710(18) Å.15a The octahedron may be
[M{P(OEt)3}4]2+ allowed an easy reaction with hydrazine, yield- described as having the nitrogen atoms in a very regular equa-
ing chelate triazametallocycle complexes 6–12. However, torial plane, the dihedral angle between the RuPP and RuNN
crucial for the formation of the hydrazinecarboximidamide planes being only 2.6(2)°. The Os–N bond lengths of 2.113(5)
group through nucleophilic attack of RNHNH2 on the nitrile and 2.162(5) Å are only slightly shorter than those found
carbon atom of NuCNR1R2 was the presence of a labile in other tetraphosphite–osmium complexes with OsP4N2
ligand such as cyanamide itself, the easy substitution of which cores.14b,15a The 1-methyl-hydrazinecarboximidamide moiety
yielded the chelate azametallocycle.
in the nitrogenated ligand is essentially planar, with rms devi-
The reaction of hydrazines on coordinate nitriles giving ation of only 0.0258 Å, so that both N(2) and C(1) are sp2 hybri-
amidrazones was reported by us15 and, long ago, by Shaw dised. The sums of the angles around these atoms are in fact
et al.,32 who found the facile oxidation of such species. In our 359.9 and 360.1° respectively. The N-(diaminomethylene)
case, the chelation of the azo ligand prevents its oxidation in group is out-of-plane and twisted, forming a dihedral angle of
the complexes.
46.9(4)° with the first plane. The N(4)–C(4) bond distance of
The related hydrazido-cyanamide complexes [MH(Nu 1.291(11) Å clearly corresponds to a double bond. All the other
CNR1R2)L4]BPh4 4, 5 did not react with hydrazine under all C–C and C–N bond lengths in the carboximidamide, between
conditions, probably because of the absence of a labile ligand, 1.300(8) and 1.371(9) Å, are shorter than values expected
which prevented the formation of the chelate hydrazinecarboxi- for single bonds, and are indicative of some kind of
midamide group.
delocalisation.
The new azametallocycle complexes 6–12 were isolated as
The IR spectra of N,N-diethyl-1-hydrazinecarboximidamide
white (Ru, Os) or pale-yellow (Fe) solids, very stable in air and complexes [M{η2-NHvC(NEt2)N(R)NH2}L4](BPh4)2 6a–12a
in solution of polar organic solvents, in which they behave as show the νNH of the NH and NH2 groups as medium or weak
2 : 1 electrolytes.29 Their formulation is supported by analytical bands between 3435 and 3260 cm−1, whereas δNH and/or νCvN
2
and spectroscopic (IR and NMR) data and by X-ray crystal appear as strong absorptions at 1627–1598 cm−1. As well as the
−
structure determination of complex [Os{η2-NHvC[NvC- signals of phosphites and BPh4 anion, the 1H NMR spectra
(NH2)2]N(CH3)NH2}{P(OEt)3}4](BPh4)2 12b, the ORTEP of show a quartet and a triplet of ethyl substituents NEt2 and two
which is shown in Fig. 1.
broad signals between 6.14 and 3.06 ppm, of intensity ratio
The asymmetric unit in 12b contains two tetraphenylborate 2 : 1, attributed to the amine NH2 and imine vNH protons of
anions and a bivalent cationic osmium complex. The osmium the azametallocycle ligand. The spectra also display the
atom in the cationic complex is coordinated by four triethyl- signals of the substituent R of the hydrazine nitrogen atom,
phosphite ligands and a N,N′-bidentate N-(diaminomethylene)- matching the presence of the azo ligand. The 31C NMR spectra
1-methyl-hydrazinecarboximidamide ligand with a chelating of 11a show the expected signals of the ligands; in particular,
a singlet at 159.37 ppm was attributed to the imine HNvC
carbon resonance of the carboximidamide ligand, whereas
the 31P spectra are ABC2 multiplets, matching the proposed
formulation.
The IR spectra of N-carbamimidoyl-1-hydrazinecarboximi-
damide derivatives [M{η2-NHvC[NvC(NH2)2]NRNH2}L4]-
(BPh4)2 6b, 7b, 10b, 12b showed several bands in the
3445–3320 cm−1 region, attributed to the νNH of the NH and
NH2 groups of the azometallacycle ligand. The δNH is observed
2
as a strong absorption at 1635–1617 cm−1. However, the pres-
1
ence of this ligand was confirmed by H NMR spectra, which
showed three broad signals between 6.17 and 3.42 ppm, of
intensity ratio 2 : 4 : 1, attributed to the NH2, [NvC(NH2)2] and
Fig. 1 ORTEP33 view of the cation of 12b, drawn at 30% probability
vNH groups. The spectra also show the signals of the substi-
level. Ethoxy groups on all the phosphites were not drawn for clarity.
tuent to the N(R) nitrogen atoms, either as singlets at
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7314–7323 | 7321

View Article Online
Paper
Dalton Transactions
3.03–3.05 ppm for R = Me (7b, 10b, 12b) or as a hump at
2.23 ppm for R = H (6b). In the 13C NMR spectrum of 10b, the
resonance of the imine NvC carbon atoms appears at
164.04 ppm and that of the methyl substituent N(CH3) at
40.58 ppm, fitting the proposed formulation. In the tempera-
ture range +20 to −80 °C, the 31P NMR spectra of complexes
6b, 7b, 10b, 12b appear as ABC2 multiplets, indicating
that a geometry like that found in the solid state occurs in
solution.
Silva, C. M. P. Ferreira, E. M. P. R. P. Branco, J. J. R. Fraústo
da Silva, A. J. L. Pombeiro, R. A. Michelin, U. Belluco,
R. Bertani, M. Mozzon, G. Bombieri, F. Benetollo and
V. Yu. Kukushkin, Inorg. Chim. Acta, 1997, 265, 267;
(c) C. M. P. Ferreira, M. F. C. Guedes da Silva,
J. J. R. Fraústo da Silva, A. J. L. Pombeiro, V. Yu. Kukushkin
and R. A. Michelin, Inorg. Chem., 2001, 40, 1134;
(d) C. M. P. Ferreira, M. F. C. Guedes da Silva, T. Duarte,
J. J. R. Fraústo da Silva, A. J. L. Pombeiro, R. A. Michelin
and V. Yu. Kukushkin, Inorg. Chim. Acta, 2002, 334, 395;
(e) C. M. P. Ferreira, M. F. C. Guedes da Silva,
R. A. Michelin, V. Yu. Kukushkin, J. J. R. Fraústo da Silva
and A. J. L. Pombeiro, Dalton Trans., 2003, 3751;
(f) A. G. Tskhovrebov, N. A. Bokach, M. Haukka and
V. Y. Kukushkin, Inorg. Chem., 2009, 48, 8678;
(g) M. N. Kopylovich, J. Lasri, M. F. C. Guedes da Silva and
A. J. L. Pombeiro, Eur. J. Inorg. Chem., 2011, 377.
7 (a) S. M. P. R. M. Cunha, M. F. C. Guedes da Silva and
A. J. L. Pombeiro, J. Chem. Soc., Dalton Trans., 2002, 1971;
(b) L. M. D. R. S. Martins, E. C. B. A. Alegria, D. L. Hughes,
J. J. R. Fraústo da Silva and A. J. L. Pombeiro, Dalton Trans.,
2003, 3743; (c) S. M. P. R. M. Cunha, M. F. C. Guedes da
Silva and A. J. L. Pombeiro, Inorg. Chem., 2003, 42, 2157;
(d) Y.-L. Tsai, F. H. Stephens, K. Meyer, A. Mendiratta,
M. D. Gheorghiu and C. C. Cummins, Organometallics,
2003, 22, 2902.
Conclusions
This paper reports the preparation of the first bis(dialkylcyana-
mide) [M(NuCNEt2)2L4](BPh4)2 and bis(cyanoguanidine)
[M{NuCN(H)C(NH2)vNH}2L4](BPh4)2 complexes of the iron
triad. Among the properties shown by these complexes, is the
reaction with hydrazine, which proceeds with nucleophilic
attack on the cyanamide carbon atom, affording chelate
η2-hydrazinecarboximidamide derivatives [M{η2-N(H)vC(NEt2)-
N(R)NH2}L4](BPh4)2.
Acknowledgements
Thanks are due to Mrs Daniela Baldan for technical
assistance.
8 (a) A. Schäfer, E. Herdtweck and G. D. Frey, Inorg. Chim.
Acta, 2006, 359, 4885; (b) J. Xiang, W.-L. Man, S.-M. Yiu,
S.-M. Peng and T.-C. Lau, Chem.–Eur. J., 2011, 17, 13044;
(c) C. Harb, P. Kravtsov, M. Choudhuri, E. R. Sirianni,
G. P. A. Yap, A. B. P. Lever and R. J. Crutchley, Inorg. Chem.,
2013, 52, 1621.
Notes and references
1 N. A. Bokach and V. Yu. Kukushkin, Coord. Chem. Rev.,
2013, 257, 2293.
2 H. Bock, Angew. Chem., Int. Ed. Engl., 1962, 1, 550.
3 E. O. Fischer, W. Kleine, U. Schubert and D. Neugebauer,
J. Organomet. Chem., 1978, 149, C40.
9 (a) R. A. Michelin, M. Mozzon and R. Bertani, Coord. Chem.
Rev., 1996, 147, 299; (b) V. Yu. Kukushkin and
A. J. L. Pombeiro, Chem. Rev., 2002, 102, 1771.
4 M. H. Chisholm, J. C. Huffman and N. S. Marchant, J. Am. 10 A. J. L. Pombeiro and V. Yu. Kukushkin, in Comprehensive
Chem. Soc., 1983, 105, 6162.
Coordination Chemistry, ed. J. A. McCleverty and T. J. Meyer,
5 (a) M. S. Begley, P. Hubberstey and P. H. Walton, J. Chem.
Elsevier Science, New York, 2nd edn, 2004, vol. I.
Soc., Dalton Trans., 1995, 957; (b) A. S. Batsanov, 11 (a) P. Ray, Chem. Rev., 1961, 61, 313; (b) V. H. Michaud,
P. Hubberstey, C. E. Russel and P. H. Walton, J. Chem. Soc.,
Dalton Trans., 1997, 2667; (c) A. S. Batsanov, M. S. Begley,
W. W. George, P. Hubberstey, M. Munakata, C. E. Russel
and P. H. Walton, J. Chem. Soc., Dalton Trans., 1999, 4251;
(d) J. K. Bera, M. Nethaji and A. G. Samuelson, Inorg.
Chem., 1999, 38, 1725; (e) S.-M. Kuang, D. G. Cuttell,
D. R. McMillin, P. E. Fanwick and R. A. Walton, Inorg.
W. Goll, B. Hammer, J. von Seyerl, W. Sturm, S. Weiss and
R. Youngman, Chem. Ztg., 1988, 112, 287; (c) R. K. Ray,
M. K. Bandyopadhyay and G. B. Kauffman, Polyhedron,
1989, 8, 757; (d) B. Dey, S. R. Choudhury, S. Das, A. D. Jana,
L.-P. Lu, M.-L. Zhu, A. Dutta and S. Mukhopadhyay, Polyhe-
dron, 2008, 27, 2899; (e) C. R. McColl, Aust. J. Exp. Agric.,
1986, 26, 505.
Chem., 2002, 41, 3313; (f) L.-L. Zheng, J.-D. Leng, W.-T. Liu, 12 (a) R. W. Miller and R. R. Eady, Biochim. Biophys. Acta,
W.-X. Zhang, J.-X. Lu and M.-L. Tong, Eur. J. Inorg. Chem.,
2008, 4616; (g) H. Hadadzadeh, A. R. Rezvani and
H. Esfandiari, Polyhedron, 2008, 27, 1809; (h) L.-C. Kang,
X. Chen, X.-S. Wang, Y.-Z. Li, Y. Song, J.-L. Zuo and
X.-Z. You, Dalton Trans., 2011, 40, 5200.
1988, 952, 290; (b) U. H. Maier-Greiner, B. M. Obermaier-
Skrobranek, L. M. Estermaier, W. Kammerloher, C. Freund,
C. Wülfing, U. I. Burkert, D. H. Matern, M. Breuer
and M. Euliz, Proc. Natl. Acad. Sci. U. S. A., 1991, 88,
4260.
6 (a) M. F. C. Guedes da Silva, E. M. P. R. P. Branco, Y. Wang, 13 (a) M. M. Bishop, A. H. W. Lee, L. F. Lindoy and P. Turner,
J. J. R. Fraústo da Silva, A. J. L. Pombeiro, R. Bertani,
R. A. Michelin, M. Mozzon, F. Benetollo and G. Bombieri,
J. Organomet. Chem., 1995, 490, 89; (b) M. F. C. Guedes da
Polyhedron, 2003, 22, 735; (b) M. M. Bishop, S. J. Coles,
L. F. Lindoy and A. Parkin, Inorg. Chim. Acta, 2006, 359,
3565; (c) M. M. Bishop, L. F. Lindoy, M. McPartlin,
7322 | Dalton Trans., 2014, 43, 7314–7323
This journal is © The Royal Society of Chemistry 2014

View Article Online
Dalton Transactions
Paper
A. Parkin, O. T. Thorn-Seshold and P. Turner, Polyhedron, 19 (a) D. H. Gerlach, W. G. Peet and E. L. Muetterties, J. Am.
2007, 26, 415.
Chem. Soc., 1972, 94, 4545; (b) D. H. Gerlach and
W. G. Peet, Inorg. Synth., 1974, 15, 38.
14 (a) G. Albertin, S. Antoniutti, A. Bacchi, E. Bordignon,
G. Pelizzi and P. Ugo, Inorg. Chem., 1996, 35, 6245; 20 G. Albertin, S. Antoniutti and E. Bordignon, J. Chem. Soc.,
(b) G. Albertin, S. Antoniutti, A. Bacchi, D. Barbera, Dalton Trans., 1989, 2353.
E. Bordignon, G. Pelizzi and P. Ugo, Inorg. Chem., 1998, 37, 21 SMART Version 5.054, Instrument control and data collection
5602; (c) G. Albertin, S. Antoniutti, E. Bordignon and
F. Menegazzo, J. Chem. Soc., Dalton Trans., 2000, 1181;
software, Bruker Analytical X-ray Systems Inc., Madison,
Wisconsin, USA, 1997.
(d) G. Albertin, S. Antoniutti, E. Bordignon and B. Carrera, 22 SAINT Version 6.01, Data Integration software package,
Inorg. Chem., 2000, 39, 4646; (e) G. Albertin, S. Antoniutti,
A. Bacchi, M. Boato and G. Pelizzi, J. Chem. Soc., Dalton
Bruker Analytical X-ray Systems Inc., Madison, Wisconsin,
USA, 1997.
Trans., 2002, 3313; (f) G. Albertin, S. Antoniutti and 23 G. M. Sheldrick, SADABS. An empirical absorption correction
M. T. Giorgi, Eur. J. Inorg. Chem., 2003, 2855;
(g) G. Albertin, S. Antoniutti, A. Bacchi, C. D’Este and
program for area detector data, University of Göttingen,
Germany, 1996.
G. Pelizzi, Inorg. Chem., 2004, 43, 1336; (h) G. Albertin, 24 P. McArdle, J. Appl. Crystallogr., 1995, 28, 65.
S. Antoniutti, M. Bortoluzzi, J. Castro-Fojo and S. Garcia- 25 G. M. Sheldrick, Acta Crystallogr., Sect. A: Fundam. Crystal-
Fontán, Inorg. Chem., 2004, 43, 4511; (i) G. Albertin,
logr., 2008, 64, 112.
S. Antoniutti, A. Bacchi, F. De Marchi and G. Pelizzi, Inorg. 26 (a) S. D. Ittel, A. D. English, C. A. Tolman and J. P. Jesson,
Chem., 2005, 44, 8947; ( j) G. Albertin, S. Antoniutti,
M. Bedin, J. Castro and S. Garcia-Fontán, Inorg. Chem.,
Inorg. Chim. Acta, 1979, 33, 101; (b) G. Albertin,
P. Agnoletto and S. Antoniutti, Polyhedron, 2002, 21, 1755.
2006, 45, 3816; (k) G. Albertin, S. Antoniutti, A. Bacchi, 27 P. Amendola, S. Antoniutti, G. Albertin and E. Bordignon,
A. Celebrin, G. Pelizzi and G. Zanardo, Dalton Trans., 2007, Inorg. Chem., 1990, 29, 318.
661; (l) G. Albertin, S. Antoniutti and J. Castro, J. Organo- 28 G. Albertin, S. Antoniutti, D. Baldan and E. Bordignon,
met. Chem., 2012, 697, 6; (m) G. Albertin, S. Antoniutti, Inorg. Chem., 1995, 34, 6205.
L. Bonaldo, A. Botter and J. Castro, Inorg. Chem., 2013, 52, 29 W. J. Geary, Coord. Chem. Rev., 1971, 7, 81.
2870.
30 K. M. Watson and D. G. Neilson, in The Chemistry of
15 (a) G. Albertin, S. Antoniutti, A. Bacchi, E. Bordignon,
P. M. Dolcetti and G. Pelizzi, J. Chem. Soc., Dalton Trans.,
Amidines and Imidates, ed. S. Patai, Wiley, London, 1975,
p. 491.
1997, 4435; (b) G. Albertin, S. Antoniutti, E. Bordignon and 31 (a) A. M. Bianucci, F. Demartin, M. Manassero,
S. Pattaro, J. Chem. Soc., Dalton Trans., 1997, 4445;
(c) G. Albertin, S. Antoniutti, A. Bacchi, M. Bergamo,
E. Bordignon and G. Pelizzi, Inorg. Chem., 1998, 37,
479.
N. Masciocchi, M. L. Ganadu, L. Naldini and A. Panzanelli,
Inorg. Chim. Acta, 1991, 182, 197; (b) A. J. Blake,
P. Hubberstey, U. Suksangpanya and C. L. Wilson, J. Chem.
Soc., Dalton Trans., 2000, 3873; (c) P. A. M. Williams,
E. G. Ferrer, N. Baeza, O. E. Piro, E. E. Castellano and
E. J. Baran, Z. Anorg. Allg. Chem., 2005, 631, 1502.
16 G. Albertin, S. Antoniutti and J. Castro, Eur. J. Inorg. Chem.,
2009, 5352.
17 E. Nachbaur and G. Leiseder, Monatsh. Chem., 1971, 102, 32 R. Mason, K. M. Thomas, A. R. Galbraith, B. L. Shaw and
1718.
C. M. Elson, J. Chem. Soc., Chem. Commun., 1973, 297.
33 L. J. Farrugia, J. Appl. Crystallogr., 1997, 30, 565.
18 G. Balacco, http://www.inmr.net/
This journal is © The Royal Society of Chemistry 2014
Dalton Trans., 2014, 43, 7314–7323 | 7323