Heterodinuclear complexes of 4,5-diazafluorene derivatives displaying η5,κ2-[N,N] and η5, κ1-N coordination modes

Article abstract of DOI:10.1039/c4dt01165a

The syntheses and structures for a series of heterodinuclear complexes of 4,5-diazafluorenyl (L^-) and 3,6-dimesityl-4,5-diazafluorenyl (L _Mes^-) ligands are reported herein. In all these heterodinuclear complexes, the Ru^II centre is sandwiched between a pentamethylcyclopentadienyl (Cp*) ligand and the C₅ ring of L^- or L_Mes^- in a double η⁵ fashion, while the other metal (Fe^II, Co^II, Pt ^II, or Cu^I) is bound to the N-donors.

Full text of DOI:10.1039/c4dt01165a

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Heterodinuclear complexes of 4,5-diazafluorene
derivatives displaying η5,κ2-[N,N] and η5,κ1-N
coordination modes†
Cite this: Dalton Trans., 2014, 43,
8951
Rhys Batcup, Vincent T. Annibale and Datong Song*
The syntheses and structures for a series of heterodinuclear complexes of 4,5-diazafluorenyl (L−) and 3,6-
dimesityl-4,5-diazafluorenyl (LMes−) ligands are reported herein. In all these heterodinuclear complexes,
the RuII centre is sandwiched between a pentamethylcyclopentadienyl (Cp*) ligand and the C5 ring of L−
or LMes− in a double η5 fashion, while the other metal (FeII, CoII, PtII, or CuI) is bound to the N-donors.
Received 21st April 2014,
Accepted 24th April 2014
DOI: 10.1039/c4dt01165a
www.rsc.org/dalton
Introduction
The potential application of heteromultimetallic complexes as
catalysts in modern organic syntheses has recently become a
topic of interest.1,2 The interest lies with the potential of
these heteromultimetallic complexes to display metal–metal
cooperativity that is unattainable from their monometallic or
homomultimetallic derivatives.2,3 In spite of all the excite-
ment, the synthesis of heteromultimetallic complexes is a chal-
lenging process. Even the controlled synthesis of
heterodinuclear complexes, the simple members of the family,
require much synthetic effort. A wide range of binucleating
ligands have been explored,4 accompanied by a variety of strat-
egies to control the regioselectivity.5–9
Recently our group has explored the use of 4,5-diazafluore-
nyl derivatives as ambidentate,10 binucleating,11–13 and actor
ligands.14–17 The 4,5-diazafluorenyl (L−) ligand has two distinct
coordination sites: a Cp moiety and an N,N-chelate and there-
fore, can potentially accommodate two metal centres in an
η5,κ2-[N,N] coordination mode (Scheme 1). Among the reported
mononuclear complexes of L−, most metal centres selectively
coordinate to the N,N-chelate leaving the Cp moiety
vacant.11,15–20 The exception was found in the mononuclear
complex formed between L− and the [RuCp*]+ unit, where the
L− ligand binds with the Ru centre via its Cp moiety in an η5-
fashion to form an organoruthenium sandwich complex
[Ru(η5-Cp*)(η5-L)] (1), leaving the N,N-chelate site vacant. Inter-
estingly, through a different reaction sequence, the L− ligand
can also form a tetraruthenamacrocycle, [RuCp*L]4, in which
Scheme 1 Anionic 4,5-diazafluorenide derivatives and proposed η5,κ2-
[N,N] coordination modes.
each L− ligand binds one Ru centre through the N,N-chelate
site and bridges to an adjacent Ru centre via the 9-position
carbon in an η1(σ)-fashion.10 In a few dinuclear complexes, the
Cp moiety of the L− ligand displays two coordination modes.
For example, the η1(σ) binding mode has been observed in a
PdII head-to-tail dimer, where the overall coordination mode
of L− is η1(σ),κ1-N.11 In a PtII–CuI heterodinuclear complex,
the Cp moiety of L− coordinates to the CuI centre in an η1(π)-
fashion; the overall coordination mode of L− is η1(π),κ2-[N,N].13
Although the proposed η5,κ2-[N,N] coordination mode in
Scheme 1 was implied in a patent, where a Zr–Pd heterodi-
nuclear complex of L− was claimed to have interesting catalytic
activity towards olefin polymerization,21 such a coordination
mode has not been reported to date with concrete experi-
mental evidence.
More recently, our group has installed the bulky mesityl
groups ortho to the N-donors, to form 3,6-dimesityl-4,5-diaza-
fluorene (HLMes). The goal is to control the regioselectivity of
the binucleating ligand by limiting the access of bulky metal
fragments to the N-donors. We have shown that the [RuCp*]+
fragment is too bulky to coordinate to the N,N-chelate site of
HLMes and 3,6-dimesityl-4,5-diazafluorenide (LMes−).10 Instead,
the [RuCp*]+ fragment selectively coordinates to either the C5
Davenport Chemical Research Laboratories, Department of Chemistry, University of
Toronto, 80 St. George Street, Toronto, Ontario, Canada M5S 3H6.
E-mail: dsong@chem.utoronto.ca; Fax: +1 416 978 7013; Tel: +1 416 978 7014
†CCDC 991907–991913. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c4dt01165a
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ring of LMes in an η5-fashion giving the sandwich complex 3.70–3.80 (THF O–CH2): 6H, equivalent to 1.5 THF per mole-
[Ru(η5-Cp*)(η5-LMes)] (2) or the C6 ring of a mesityl group in an cule of 4.
−
η6-fashion depending on the reaction sequence.10
Synthesis of [PtPh2LMes][K(DME)2] (5), method 1. Complex 4
The N-donors of the sandwich complexes 1 and 2 are (45.1 mg, 59.8 μmol) and KOtBu (7.2 mg, 64.2 μmol) were dis-
dangling making them ideal metalloligands for the synthesis solved in 2 mL of THF. After standing at RT for 3 h a purple
of heterodinuclear complexes where the ligand may display solution resulted and the solvent was removed under vacuum.
the η5,κ2-[N,N] coordination mode (Scheme 1). In related The pink residue was dissolved in a DME–THF mixture (2 : 1
works, the [Cp*Ru]+ and [Cp*Fe]+ fragments have been used to by volume). The solvent was removed under reduced pressure
construct metalloligand for the syntheses of multinuclear com- to yield purple crystals of 5 (49.1 mg, 50.5 μmol, 85% crystal-
plexes, where the [Cp*Ru]+ or [Cp*Fe]+ fragment coordinates to line yield).
the π-system of ligand backbone while other donor atoms bind
Synthesis of [PtPh2LMes][K(DME)2] (5), method 2. LMesH
with other metal centres.22–29 Herein we report the syntheses (50 mg, 123.6 μmol) and KOtBu (13.9 mg, 123.6 μmol) were dis-
−
of RuII–M heterodinuclear complexes using L− and LMes as solved in 3 mL of THF and stirred for 3 hours at RT. The result-
binucleating ligands, where M can be metals spanning groups ing red solution of KLMes was added to 1 unit equiv. of
8 to 11.
[PtPh2(μ-SMe2)]n (50.8 mg, 123.6 μmol). The mixture was
stirred overnight at RT to yield a purple solution. The solvent
was then removed under vacuum and the resulting purple
residue was dissolved in a DME–THF mixture (5 : 1 by volume).
The solution was filtered and hexanes vapour was diffused
into the filtrate, resulting in the formation of X-ray diffraction
quality needle-shaped purple crystals of 5 (84.6 mg, 87.0 μmol,
Experimental section
General considerations
Unless otherwise noted, all reactions and manipulations were 70% crystalline yield). 1H NMR (DMSO-d6, 400 MHz, 25 °C):
3
3
performed in an MBraun glovebox under a dinitrogen atmos- δ 7.91 (d, J = 8.0 Hz, 1H, daf), 7.84 (d, J = 8.0 Hz, 1H, daf),
phere. All solvents were dried and degassed using standard 7.01–6.93 (m, 4H, daf, Mes, Pt–Ph), 6.90 (s, 1H, Mes), 6.84 (s,
procedures and stored in the glovebox over 3 Å molecular 1H, Mes), 6.68 (dd, J = 8.0 Hz, 4J = 2.0 Hz, 2H, Pt–Ph), 6.59 (d,
3
sieves. Unless otherwise stated, all reagents were purchased 3J = 8.0 Hz, 1H, daf), 6.50 (s, 1H, Mes), 6.47–6.38 (m, 3H, Pt–
3
from commercial sources and used without further purifi- Ph), 6.36–6.30 (m, 1H, Pt–Ph), 6.24 (t, J = 8.0 Hz, 2H, Pt–Ph),
cation.
[PtPh2(μ-SMe2)]n (n
CoCl2(THF)1.5
Compounds
L
MesH,10
[RuCp*(μ3-Cl)]4,30 6.12 (s, 1H, daf), 3.43 (s, 8H, DME), 3.24 (s, 12H, DME), 2.33
33
=
2
or 3),31,32 FeCl2(THF)1.5
,
and (s, 3H, Mes), 2.29 (s, 3H, Mes), 2.23 (s, 3H, Mes), 2.22 (s, 3H,
33
,
1,10 2,10 and [PtLPh2][Na(DME)3] (3),13 were Mes), 2.04 (s, 3H, Mes), 0.57 (s, 3H, Mes). 13C NMR (DMSO-d6,
all synthesized according to literature procedures. The H, 13C 100 MHz, 25 °C): δ 148.78, 147.18, 145.03, 142.70, 140.62,
{1H}, 195Pt{1H} NMR spectra were recorded on a Varian 140.50, 139.27, 138.04, 137.91, 136.30, 135.25, 135.05, 134.75,
400 MHz, Varian 500 MHz, or an Agilent DD2 600 spectro- 134.73, 134.66, 129.40, 127.77, 127.72, 127.50, 127.22, 127.03,
meter. Chemical shifts were referenced relative to the solvents’ 126.38, 125.15, 125.11, 124.97, 124.07, 124.02, 123.97, 120.15,
residual signals. Elemental analyses were performed on a PE 119.75, 117.41, 117.24, 79.28, 71.05, 58.03, 21.67, 21.19, 21.01,
2400 C/H/N/S analyser at the ANALEST facility of our Chem- 20.80, 20.46, 19.05. 195Pt NMR (DMSO-d6, 600 MHz, 25 °C):
istry Department. In the NMR data section, “daf” stands for δ −3722.9. Anal. Calcd for C49H57N2O4PtK: C, 60.54; H, 5.91;
1
diazafluorenyl.
Synthesis of PtPh2(LMesH) (4). In the glovebox LMes
(51 mg, 126.1 μmol) and 1 unit equiv. of [PtPh2(μ-SMe2)]n 25 °C): δ 7.35 (d, J = 8.8 Hz, 2H, daf), 6.98 (s, 4H, Mes), 6.74
(51.9 mg, 126.1 μmol) were dissolved in 6 mL of THF. After (d, J = 8.8 Hz, 2H, daf), 4.82 (s, 1H, daf), 2.39 (s, 12H, Mes),
N, 2.88. Found: C, 59.97; H, 5.84; N, 2.86.
H
1H NMR data for RuCp*LMes (2). 1H NMR (C6D6, 400 MHz,
3
3
standing at RT for 2 h, the resulting orange solution was con- 2.24 (s, 6H, Mes), 1.50 (s, 15H, Cp*).
centrated to ∼5 mL under vacuum. The subsequent vapour
Synthesis of RuCp*LPtPh2 (6), method 1. To 1 unit equiv. of
diffusion of hexanes overnight gave yellow block-shaped X-ray [PtPh2(μ-SMe2)]n (22.4 mg, 54 μmol) was added 1 (19.2 mg,
diffraction quality crystals of 4 (72 mg, 95.5 μmol, 76% crystal- 47.6 μmol) in 2 mL of THF. The resulting brown solution was
line yield). 1H NMR (CDCl3, 500 MHz, 25 °C): δ 8.03 (d, 3J = 8.0 allowed to stand overnight at RT. The resulting suspension was
Hz, 2H, daf), 7.13 (d, 3J = 8.0 Hz, 2H, daf), 6.79 (m with Pt-sat- filtered and the precipitate was washed thoroughly with THF.
3
ellites, JPt–H = 76 Hz, 4H, Pt–Ph), 6.44 (s, 4H, Mes), 6.22 (m, The filtrate and THF washes were combined and concentrated
6H, Pt–Ph), 4.20 (s, 2H, daf), 3.70–3.80 (m, THF) 2.14 (s, 6H, to dryness under vacuum. The resulting orange/brown residue
Mes), 2.05 (s, 12H, Mes), 1.80–1.90 (m, THF). 13C NMR (CDCl3, was washed with hexanes and dried under vacuum to yield 6
126 MHz, 25 °C): δ 162.86, 161.79, 138.02, 137.26, 135.79, (21.4 mg, 28.4 μmol, 60% yield).
135.01, 134.51, 133.94, 133.93, 128.61, 128.47, 125.29, 119.72,
Synthesis of RuCp*LPtPh2 (6), method 2. To a solution of 3
68.13 (THF) 34.84, 25.77 (THF), 21.12, 20.90. Anal. Calcd for (50 mg, 61.7 μmol) in 3 mL of THF was added a suspension of
C41H38N2Pt·1.5(C4H8O): C, 65.48; H, 5.86; N, 3.25. Found: C, [RuCp*(μ3-Cl)]4 (16.8 mg, 15.4 μmol) in 8 mL of THF. The
65.30; H, 5.70; N, 3.38. The amount of THF in the EA sample resulting brown suspension was allowed to stand overnight at
was determined by the integration of the multiplet at RT. A yellow/beige precipitate was removed by filtration and
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the solvent of the filtrate was removed under vacuum to yield 3.06 ppm (Cp* methyl, which is the largest peak and refer-
compound 6 (46.0 mg, 61.1 μmol, 99% yield). X-ray diffraction enced to 15H).
quality crystals of 6 were obtained by diffusing pentane into a
Synthesis of RuCp*LMesCoCl2 (9). Compound 2 (83.1 mg,
toluene solution of 6 at −33 °C. 1H NMR (C6D6, 600 MHz, 129.9 μmol) and CoCl2(THF)1.5 (31 mg, 130.2 μmol) were sus-
3
4
25 °C): δ 8.22 (dd, J = 4.2 Hz, J = 1.2 Hz, 2H, daf), 8.14 (m pended in 3 mL of THF and allowed to stand overnight at RT.
3
with Pt satellites, JPt–H = 77 Hz, 4H, Pt–Ph), 7.38 (m, 4H, Pt– The resulting dark brown solution was filtered to remove blue
Ph), 7.21 (m, 2H, Pt–Ph), 7.13 (m, toluene), 7.07 (dd, 3J = 8.4 solids. The filtrate was concentrated to dryness under vacuum
4
3
Hz, J = 1.2 Hz, 2H, daf), 7.02 (m, toluene), 5.99 (dd, J = 8.4 to yield a dark brown residue. The X-ray diffraction quality
Hz, 3J = 4.2 Hz, 2H, daf), 4.72 (s, 1H, daf), 2.11 (s, toluene), crystals of 9 were obtained by diffusion of pentane into a DME
1.20 (s, 15H, Cp*). Anal. Calcd for C33H32N2PtRu·0.27(C7H8): solution of 9 (56 mg, 72.8 μmol, 56% crystalline yield). 1H
C, 53.88; H, 4.44; N, 3.60. Found: C, 53.86; H, 4.64; N, 3.60. NMR (CDCl3, 600 MHz, 25 °C): δ 50.30 (s), 49.75 (s), 22.87 (s),
The amount of toluene in the EA sample was determined by 6.12 (s), 3.10–3.70 (br, m), 1.00–1.70 (br, m), −0.71 (s), −0.99
the integration of the singlet at 2.11 ppm (toluene methyl): (s), −2.05 (s), −2.91 (s), −3.05 to −3.56 (br, m), −9.40 (s),
0.82H, equivalent to 0.27 toluene per molecule of 6. Com- −13.47 (s). Anal. Calcd for C39H42N2Cl2CoRu: C, 60.86; H, 5.50;
pound 6 is not soluble enough in C6D6 to give an informative N, 3.64. Found: C, 60.68; H, 5.63; N, 3.63.
13C NMR spectrum.
Synthesis of RuCp*LMesCuCl (10). Compound 2 (76.2 mg,
Synthesis of RuCp*LMesPtPh2 (7), method 1. Compound 2 119.1 μmol) and CuCl (13 mg, 131.3 μmol) were suspended in
(50 mg, 78.14 μmol) and 1 unit equiv. of [PtPh2(μ-SMe2)]n 5 mL of THF and allowed to stand overnight at RT. The result-
(32.1 mg, 78.14 μmol) were dissolved in 10 mL of THF. The ing red solution was filtered to remove excess CuCl. The filtrate
resulting red solution was allowed to stand overnight at RT. was concentrated to dryness under vacuum to yield a red
The volatiles were then removed under vacuum and the red residue. The X-ray diffraction quality crystals of 10·0.5DME
residue was dissolve in 10 mL of toluene. Pentane was diffused were obtained by vapour diffusion of hexanes into a DME solu-
1
into the resulting solution to afford X-ray diffraction quality tion of 10 (55.0 mg, 70.2 μmol, 59% crystalline yield). H NMR
red crystals of 7 (20.2 mg, 20.4 μmol, 26% crystalline yield).
(C6D6, 400 MHz, 25 °C): δ 7.34 (d, 3J = 8.8 Hz, 2H, daf),
3
Synthesis of RuCp*LMesPtPh2 (7), method 2. Compound 5 6.94–6.76 (br, 4H, Mes), 6.60 (d, J = 8.8 Hz, 2H, daf), 4.82 (s,
(35 mg, 36 μmol) and [RuCp*(μ3-Cl)]4 (9.8 mg, 9 μmol) were 1H, daf), 2.35–2.75 (br, 6H, Mes), 1.95–2.35 (br, 6H, Mes), 2.12
suspended in 5 mL of THF and allowed to stand overnight at (s, 6H, Mes), 1.49 (s, 15H, Cp*). Anal. Calcd for
RT to yield a red solution. Volatiles were removed under C39H42N2ClCuRu: C, 63.40; H, 5.73; N, 3.79. Found: C, 63.19;
vacuum and the residue was extracted with toluene and fil- H, 5.82; N, 3.88. Due to the solution behaviour (i.e., slow
tered to remove KCl. The solvent was removed under vacuum rotation of the mesityl groups with respect to the NMR time
1
to yield 7 as a red residue (32.5 mg, 32.8 μmol, 91% yield). H scale) of 10, the 13C NMR spectrum was not informative.
3
NMR (C6D6, 400 MHz, 25 °C): δ 7.41 (m with Pt satellite, JPt–H
3
X-ray diffraction analysis
= 76 Hz, 4H, Pt–Ph), 7.17 (d, J = 8.8 Hz, 2H, daf), 6.68 (s, 2H,
Mes), 6.60–6.67 (m, 4H, Pt–Ph), 6.59–6.52 (m, 2H, Pt–Ph), 6.40
(s, 2H, Mes), 6.31 (d, 3J = 8.8 Hz, 2H, daf), 4.75 (s, 1H, daf),
2.40 (s, 6H, Mes), 2.14 (s, 6H, Mes), 2.10 (s, 6H, Mes), 1.72 (s,
15H, Cp*). 13C NMR (C6D6, 100 MHz, 25 °C): δ 162.74, 138.05,
138.03, 137.05, 136.22, 135.96, 135.74, 133.00, 129.31, 128.73,
125.63, 124.84, 120.26, 113.40, 85.38, 84.22, 57.67, 21.56,
21.18, 20.44, 11.30. Anal. Calcd for C51H52N2PtRu: C, 61.93; H,
5.30; N, 2.83. Found: C, 62.41; H, 5.43; N, 2.89.
Synthesis of RuCp*LMesFeCl2 (8). Compound 2 (48 mg,
75.0 μmol) and FeCl2(THF)1.5 (17.6 mg, 74.9 μmol) were sus-
pended in 3 mL of THF and allowed to stand overnight at RT.
Volatiles were removed under vacuum to yield a red residue.
The X-ray diffraction quality crystals of 8 were obtained by
diffusing hexanes into a toluene solution of 8 (22.6 mg,
29.5 μmol, 39% crystalline yield). 1H NMR (CDCl3, 400 MHz,
25 °C): δ 54.55 (s), 7.13–7.32 (m, toluene), 8.74 (s), 4.52 (s),
3.98 (s), 3.36 (s), 3.06 (br, s), 2.36 (s, toluene), 1.00–1.80 (br),
0.17 (s), 0.07 (s), −1.00 to −2.25 (br), −2.55 to −4.25 (br),
−12.07 (s). Anal. Calcd for C39H42N2Cl2FeRu·1.3(C7H8): C,
The X-ray diffraction data were collected on a Bruker Kappa
Apex II diffractometer, and processed with the Bruker Apex 2
software package.34 Data were collected with graphite mono-
chromated Mo Kα radiation (λ = 0.71073 Å), at 150 K controlled
by an Oxford Cryostream 700 series low temperature system.
The structures were solved by the direct methods or Patterson
and refined using SHELX-2013.35 Non-hydrogen atoms were
refined anisotropically, and hydrogen atoms were calculated
using the riding model. The disordered Cp* in 7 has been
modelled successfully over two orientations. The diffuse elec-
tron density from solvents in the lattices of 4 and 8 were
removed with SQUEEZE function of PLATON36 and the contri-
butions of these solvents were excluded from the formula. The
selected crystallographic data are summarized in Table 1.
Results and discussion
Syntheses and structures of 4 and 5
65.19; H, 5.97; N, 3.16. Found: C, 65.33; H, 5.89; N, 3.39. The The air-stable compound 4 can be synthesized by reacting
amount of toluene in the EA sample was determined by the MesH with 1 unit equiv. of [PtPh2(μ-SMe2)]n (Scheme 2). Com-
L
integration (4H) of the singlet at 2.36 ppm (toluene methyl, 1.3 pound 4 is poorly soluble in toluene and hexanes, but soluble
toluene per molecule of 8) relative to the broad singlet at in THF, CH2Cl2, and CHCl3. The molecular structure of 4 is
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Table 1 Selected crystallographic data
4
5
6
7
8
9
10·0.5DME
Formula
F.W.
T (K)
Space group
a (Å)
b (Å)
c (Å)
C
41H38N2Pt
C49H57N2O4PtK C33H32N2PtRu C51H52N2PtRu C39H42N2RuFeCl2 C39H42N2RuCoCl2 C41H47N2ORuCuCl
753.82
150(2)
P21/c
10.4945(4)
19.6731(7)
19.6007(6)
90
94.307(1)
90
4035.3(2)
4
972.15
200(2)
P21
12.0476(6)
15.8026(7)
12.8251(7)
90
114.284(2)
90
2225.6(2)
2
752.76
150(2)
P1
989.10
298(2)
P21/c
15.6887(4)
15.7554(4)
17.7728(5)
90
106.065(1)
90
766.56
150(2)
P21/c
12.4483(4)
18.2682(4)
21.5571(7)
90
121.838(1)
90
769.64
296(2)
Pca21
18.1283(7)
17.5351(5)
23.7893(9)
90
90
90
7562.2(5)
8
783.87
150(2)
P21/c
24.8011(9)
17.2929(7)
17.4643(8)
90
95.421(1)
90
ˉ
12.0472(7)
14.738(1)
15.936(1)
97.095(3)
91.064(3)
101.555(3)
2748.2(3)
4
α (Å)
β (Å)
γ (Å)
V (Å3)
Z
4221.6(2)
4
4164.7(2)
4
7456.6(5)
8
Dc (g cm−3
)
1.241
3.503
1.451
3.291
1.819
5.659
1.556
3.705
1.223
0.864
1.352
1.007
1.396
1.080
μ (mm−1
)
No. reflns. collcd. 36 824
No. indept. reflns. 9277
19 867
8410
1.110
48 190
12579
1.011
R1 = 0.0364
wR2 = 0.0640
R1 = 0.0595
wR2 = 0.0708
39 083
9686
1.262
R1 = 0.0805
wR2 = 0.1056
R1 = 0.1300
wR2 = 0.1186
35 075
8182
1.064
R1 = 0.0604
wR2 = 0.1856
R1 = 0.0697
wR2 = 0.1921
38 703
16893
0.985
R1 = 0.0573
wR2 = 0.1026
R1 = 0.1242
wR2 = 0.1218
72608
17101
1.018
R1 = 0.0543
wR2 = 0.1281
R1 = 0.0928
wR2 = 0.1478
GOF on F2
R [I > 2σ(I)]
1.061
R1 = 0.0229
R1 = 0.0503
wR2 = 0.0639 wR2 = 0.1132
R1 = 0.0289 R1 = 0.0637
wR2 = 0.0658 wR2 = 0.1182
R (all data)
Scheme 2 Synthetic routes to 4 and 5.
shown in Fig. 1. The Pt centre adopts the typical square planar
coordination geometry. As shown in Fig. 1B, the molecular
structure of 4 is highly distorted because of the steric conges-
tion. The diazafluorenyl moiety of LMesH is off planar: the two
pyridine moieties are bent downward compared to the middle
C5 ring. To minimize the repulsions between the phenyl
groups on the Pt centre and the mesityl groups on the LMesH
ligand, the Pt centre and the two phenyl groups are tilted
above the C5 ring with the dihedral angle between the C5 ring
and the Pt coordination plane of ∼19°, while the two mesityl
Fig. 1 (A) Crystal structure of 4. (B) The side view of 4. Non-hydrogen
atoms are shown as 50% probability ellipsoids, and H atoms (except for
those on the C5 ring in A) are omitted for clarity. Selected distances [Å]
and angles [°]: Pt1–N1 2.190(2), Pt1–N2 2.189(2), Pt1–C30 1.997(3),
Pt1–C36 1.992(3), N1–Pt1–N2 80.64(9), N1–Pt1–C36 96.03(9),
groups are pointing toward the opposite side of the C5 ring. C36–Pt1–C30 86.3(1), N2–Pt1–C30 96.3(1).
The tilting of the Pt-coordination plane makes the Pt–N bonds
(2.190(2) and 2.189(2) Å) in 4 weaker and longer than those in
an analogous PtII complex PtPh2(LH) (1.991(3) and 1.996(3)
Å).13 Furthermore, the dihedral angles between the pyridine
Compound 5 can be synthesized via the deprotonation of 4
moieties and the corresponding mesityl groups are ∼69° and with KOtBu in the presence of DME (Scheme 2). Alternatively, 5
−
∼67°, respectively, providing more space above the C5 plane to can be prepared by reacting LMes with 1 unit equiv. of
accommodate the PtPh2 moiety.
[PtPh2(μ-SMe2)]n in the presence of DME (Scheme 2). The
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Scheme 3 Synthetic routes to 6 and 7.
Fig. 2 Crystal structure of 5. All hydrogen atoms except for that on the
C5 ring are omitted for clarity. Ellipsoids are drawn at 50% probability
level. Selected distances [Å] and angles [°]: Pt1–N1 2.20(1), Pt1–N2 2.23(1),
Pt1–C30 1.99(1), Pt1–C36 2.02(1), N1–Pt1–N2 81.6(4), N1–Pt1–C30
96.4(4), C30–Pt1–C36 84.9(5), C36–Pt1–N2 97.1(4).
solid-state structure of 5 has been confirmed with X-ray crystal-
lography (Fig. 2). The structure of the [PtLMesPh2]− moiety in 5
resembles the structure of 4. The dihedral angle between the
−
Pt coordination plane and the plane of the C5 ring of LMes is
∼8°, i.e., much less distorted than 4. In contrast to 3 where the
Na+ cation is quarantined from the [PtPh2L]− anion by three
DME molecules,13 the [K(DME)2]+ unit in 5 is attached to the
phenyl ligands on the Pt centre through K–arene interactions.
Compound 5 is insoluble in benzene and toluene. Coordi-
nating solvents such as DMSO solvate the potassium cation,
releasing free DME molecules. In a DMSO-d6 solution, the
DMSO-solvated potassium cation associates with the complex
anion in a highly unsymmetrical way: six mesityl methyl
groups resonate as six singlets, four protons on the mesityl
rings display four singlets, and the protons at 1,2,7,8-positions
of diazafluorenyl ligand give four doublets. The proton at the
9-position of diazafluorenyl ligand appears as a singlet at
6.12 ppm. The 195Pt NMR shows only one peak at
−3722.9 ppm. Such a solution behaviour does not seem to
affect further coordination chemistry of compound 5.
Fig. 3 Crystal structure of 6. All hydrogen atoms and the second mole-
cule from the asymmetric unit have been omitted for clarity. Ellipsoids
are drawn at 50% probability level. Selected distances [Å] and angles [°]:
Pt1–N1 2.155(4), Pt1–N2 2.172(5), Pt1–C22 1.989(5), Pt1–C28 1.996(5),
Ru1–C6 2.156(5), Ru1–C7 2.151(5), Ru1–C8 2.154(5), Ru1–C9 2.154(5),
Ru1–C10 2.165(5), Ru1–C14 2.243(5), Ru1–C15 2.194(5), Ru1–C16 2.226
(5), Ru1–C20 2.215(5), Ru1–C21 2.234(5), Ru1–Pt1 4.1347(6), N1–Pt1–
N2 83.5(2), N1–Pt1–C22 89.8(2), C22–Pt1–C28 95.7(2), N2–Pt1–C28
91.1(2).
The solid-state structures of 6 and 7 have been established
by X-ray crystallography (Fig. 3 and 4). In both compounds,
each PtII centre adopts a typical square-planar geometry and is
chelated by the N,N-donor set, while the [RuCp*]+ fragment is
bound to the Cp moiety of the chelate ligand in an η5-fashion
with the average Ru–C distance of 2.222(6) Å in 6 and 2.231(8) Å
in 7. The shorter average Ru–C distances for the Cp* ligand
(2.156(5) Å in 6 and 2.159(6) Å in 7) indicate that the Ru–Cp*
interactions are stronger than Ru–L and Ru–LMes interactions.
The intramolecular Pt–Ru distances are 4.1347(6) and 4.2571(7) Å
in 6 and 7, respectively.
Syntheses and structures of 6 and 7
Compounds 6 and 7 can be prepared by reacting 0.25 equiv. of
[Cp*Ru(μ3-Cl)]4 with 3 and 5, respectively (Scheme 3). Alterna-
tively, 6 and 7 can be synthesized by reacting 1 unit equiv. of
[PtPh2(μ-SMe2)]n with 1 and 2, respectively (Scheme 3). In the
1H NMR spectra of 6 and 7 (each recorded in C6D6), the proton
at the 9-position resonates at 4.72 and 4.75 ppm, respectively.
Comparing these to the chemical shifts of the corresponding
protons in the parent compounds 1 (4.81 ppm) and 2
(4.82 ppm), the coordination of the [PtPh2] unit to the N,N-
chelate site causes upfield shifts. Presumably the π back-
Syntheses and structures of 8 and 9
donation from the electron-rich PtII centre dominates the Pt– Compounds 8 and 9 can be synthesized by reacting 2 with
ligand interactions.
FeCl2(THF)1.5 and CoCl2(THF)1.5, respectively (Scheme 4). Both
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Fig. 5 Crystal structure of 8. All hydrogen atoms have been omitted for
clarity. Ellipsoids are drawn at 50% probability level. Selected bond
lengths (Å) and angles (°): Fe1–N1 2.188(4), Fe1–N2 2.190(4), Fe1–Cl2
2.229(2), Fe1–Cl1 2.242(1), Ru1–C34 2.137(5), Ru1–C30 2.137(5), Ru1–
C32 2.159(6), Ru1–C31 2.160(6), Ru1–C33 2.161(5), Ru1–C11 2.161(4),
Ru1–C4 2.213(4), Ru1–C7 2.230(4), Ru1–C5 2.262(4), Ru1–C6 2.275(4),
N1–Fe1–N2 84.2(1), N1–Fe1–Cl2 108.0(1), N2–Fe1–Cl2 108.7(1), N1–
Fe1–Cl1 108.1(1), N2–Fe1–Cl1 109.2(1), Cl2–Fe1–Cl1 129.33(7).
Fig. 4 Crystal structure of 7. All hydrogen atoms are omitted for clarity.
Only one orientation of the disordered Cp* is shown. Ellipsoids are
drawn at 50% probability level. Selected distances [Å] and angles [°]:
Pt1–N1 2.194(6), Pt1–N2 2.244(6), Pt1–C30 2.009(8), Pt1–C36 1.988(8),
Ru1–C4 2.246(7), Ru1–C5 2.233(8), Ru1–C6 2.235(8), Ru1–C7 2.249(8),
Ru1–C11 2.192(8), Ru1–C42 2.171(6), Ru1–C43 2.162(6), Ru1–C44 2.149(6),
Ru1–C45 2.150(6), Ru1–C46 2.163(6), Ru1–Pt1 4.2568(7), N1–Pt1–
N2 81.3(2), N1–Pt1–C30 95.9(3), C30–Pt1–C36 85.1(3), N2–Pt1–C36
97.5(3).
Scheme 4 Synthetic route to 8 and 9.
complexes 8 and 9 are soluble in THF, DME, CDCl3, slightly
soluble in toluene, and insoluble in benzene. Both compounds
are paramagnetic, and gave paramagnetically shifted and
broadened signals in the 1H NMR spectra. The crystal struc-
tures of 8 and 9 are shown in Fig. 5 and 6, respectively. The
structures of 8 and 9 are similar. Each Ru centre is sandwiched
Fig. 6 Crystal structure of 9. All hydrogen atoms and the second mole-
cule from the asymmetric unit have been omitted for clarity. Ellipsoids
are drawn at 50% probability level. Selected bond lengths (Å) and angles (°):
Co1–N2 2.092(7), Co1–N1 2.130(7), Co1–Cl1 2.204(3), Co1–Cl2 2.214(3),
Ru1–C30 2.14(1), Ru1–C34 2.146(9), Ru1–C11 2.163(9), Ru1–C33
2.16(1), Ru1–C31 2.16(1), Ru1–C32 2.17(1), Ru1–C7 2.232(8), Ru1–C4 2.25(1),
Ru1–C6 2.285(7), Ru1–C5 2.292(9), Ru2–C69 2.141(9), Ru2–C70 2.15(1),
Ru2–C73 2.157(9), Ru2–C50 2.169(8), Ru2–C71 2.17(1), Ru2–C72
2.18(1), Ru2–C46 2.232(9), Ru2–C43 2.243(8), Ru2–C45 2.267(8), Ru2–
C44 2.269(8), N2–Co1–N1 86.1(3), N2–Co1–Cl1 115.1(2), N1–Co1–Cl1
110.2(2), N2–Co1–Cl2 105.6(2), N1–Co1–Cl2 109.6(2), Cl1–Co1–Cl2
123.8(1).
−
between the Cp* ligand and the C5 ring of the LMes ligand.
Each Fe/Co centre adopts a distorted tetrahedral geometry
with two nitrogen donor atoms from the chelating ligand and
two chlorides occupying the four coordination sites. The N1–
Fe1–N2 and N1–Co1–N2 angles are 84.3(1)° and 86.3(2)°,
respectively, while the Cl1–Fe1–Cl2 and Cl1–Co1–Cl2 angles
are much wider (129.33(7)° and 123.9(1)°, respectively). With
respect to the Fe/Co metal centre, the two mesityl groups in
compound 8 open more widely (the avg. Fe–Cipso distance ≈
3.75 Å) than those in compound 9 (the avg. Co–Cipso distance
≈ 3.61 Å). Unlike in 6 and 7, where the Cp* ligand and the C5
ring of the chelating ligand are nearly parallel (i.e., the di-
hedral angle between the two rings is ∼1°), the dihedral angles
between the Cp* ligand and the C5 ring of the chelating ligand
in 8 and 9 are both ∼8°, presumably due to the repulsion
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Scheme 5 Synthetic route to 10.
between the Cp* methyl groups and the chloride ligand on the
Fe/Co metal centre, along with the repulsion between the mesityl
methyl groups and the Cp* methyl groups. The intramolecular
Ru–Fe distance is 4.4269(7) Å and Ru–Co distance is 4.359(1) Å.
Synthesis and structure of 10
As shown in Scheme 5, the reaction between CuCl and 2 in
THF yields compound 10. Compound 10 is soluble in THF,
DME, toluene, and benzene. The crystal structure of 10, shown
in Fig. 7, reveals a Ru–Cu heterodinuclear structure. The Ru
−
centre is again sandwiched between the C5 ring of LMes and
the Cp* ligand in a double η5 fashion, while the two-coordi-
−
nate Cu centre is bound to one of the N-donors of LMes and a
terminal chloride ligand. Two enantiomers were seen in the
asymmetric unit of the crystal structure (10A and 10B). The
coordination geometry of the CuI centre is slightly off linear
with N–Cu–Cl angles of 171.0(1)° in 10A and 169.7(1)° in 10B.
The dihedral angle between the Cp* ligand and the C5 ring of
−
LMes is ∼6°, likely due to the repulsion between the Cp*
methyl groups and the mesityl methyl groups. The intramole-
cular Ru–Cu distances are 4.4402(6) Å and 4.5477(6) in 10A
and 10B, respectively.
Fig. 7 (A) Crystal structure of 10A. (B) Crystal structure of 10B.
All hydrogen atoms have been omitted for clarity. (A) and (B) are enantio-
mers in the asymmetric unit. Ellipsoids are drawn at 50% probability
level. Selected bond lengths (Å) and angles (°): Cu1–N1 1.890(3), Cu1–
Cl1 2.093(1), Cu2–N3 1.885(3), Cu2–Cl2 2.095(1), Ru1–C34 2.144(5),
Ru1–C30 2.147(4), Ru1–C31 2.153(4), Ru1–C33 2.158(5), Ru1–C32 2.160(4),
Ru1–C11 2.181(4), Ru1–C7 2.220(4), Ru1–C4 2.226(4), Ru1–C5 2.262(4),
Ru1–C6 2.266(4), Ru2–C72 2.155(4), Ru2–C73 2.157(4), Ru2–C71 2.166(5),
Ru2–C69 2.168(4), Ru2–C50 2.174(4), Ru2–C70 2.178(5), Ru2–C46
2.223(4), Ru2–C43 2.231(4), Ru2–C44 2.267(4), Ru2–C45 2.287(4),
N1–Cu1–Cl1 171.0(1), N3–Cu2–Cl2 169.6(1).
In the 1H NMR spectrum of 10 in C6D6 at 25 °C, the proton
in the 9-position of the diazafluorenyl ligand appears as a
singlet at 4.75 ppm. The protons of the pyridine moieties reso-
nate as only two doublets at 7.29 and 6.59 ppm, hinting that
in solution the average structure is more symmetrical than the
solid-state structure. The unsymmetrical solid-state structure
could be the result of the solid-state packing effect. The aro-
matic protons of the mesityl groups resonate as a broad peak
at 6.76–6.94 ppm, the four ortho-methyl groups of the mesityl
substituents resonate as two broad peaks at 1.95–2.35 and
2.35–2.75 ppm, while the para-methyl groups display one
singlet at 2.12 ppm, which overlaps with one of the broad
peaks from the ortho-methyl. The broad signals from the
mesityl groups are likely due to slow rotation with respect to
the NMR time scale at 25 °C.
compounds 6–10, the intramolecular intermetallic distances
are all within 4.6 Å. The C5 rings of L− and LMes bond to the
−
Ru(II) centre less strongly compared to Cp*. To the best of our
knowledge complexes 6–10 are the first examples where 4,5-
diazafluorenyl derivatives display the η5,κ2-[N,N] or η5,κ1-N
coordination mode. The reactivity of these complexes and the
syntheses of dinuclear complexes with other metal combi-
nations are being studied in our laboratory.
Conclusion
We have synthesized five RuII–M (M = FeII, CoII, PtII, CuII)
heterodinuclear complexes 6–10 using L− and LMes−. In all cases,
the RuII centre is sandwiched between the Cp* ligand and the
Acknowledgements
Cp moiety of diazafluorenyl ligand in a double η5-fashion, This research was supported by grants to D. S. from the
while the second metal is bound to one or both N-donors. For Natural Sciences and Engineering Research Council (NSERC) of
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Canada. V. T. A. gratefully acknowledges the NSERC for a post- 17 E. Stepowska, H. Jiang and D. Song, Chem. Commun., 2010,
graduate scholarship (PGS D2), and the Government of 46, 556–558.
Ontario for an Ontario Graduate Scholarship (OGS). The 18 H. Jiang, E. Stepowska and D. Song, Eur. J. Inorg. Chem.,
authors also wish to acknowledge the Canadian Foundation 2009, 2083–2089.
for Innovation Project No. 19119, and the Ontario Research 19 G. Nocton, C. H. Booth, L. Maron and R. A. Andersen,
Fund for funding the CSICOMP NMR lab at the University of
Toronto enabling the purchase of several new spectrometers.
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