Synthesis and structures of five crystalline organometallic (Li/Y, Mg/Mg) or coordination (Mg, CrII, Y/Y) complexes

Article abstract of DOI:10.1002/zaac.201100266

Abstract. Yttrium(III) chloride was the ultimate precursor of the crystalline compounds [Y{η⁵-C₅H ₄(CH(SiMe₃)₂)}₂(μ-Cl) ₂Li(THF)₂] (1), [Y{(OC(Bu^t)) ₂CH}₂{μ-OC(Bu^t)C(H)C(Bu^t)O}] ₂ (2), [{Mg(CH₂SiMe₃)(μ-CH ₂SiMe₃)(THF)}₂] (3) and [Mg(CH ₂SiMe₃){(N(C₆H₃Prⁱ ₂-2,6)C(Me))₂CH}(THF)] (4). Thus, the precursors were: YCl₃ + 2 Li[η⁵-C₅H₄{CH(SiMe ₃)₂}] for 1, [Y{N(SiMe₃)₂} ₃] + 3 [Bu^tC(O)]₂CH₂ for 2, and YCl₃ + 3 Mg(CH₂SiMe₃)Cl for 3; whereas 4 was obtained from 3 + 2 H[{N(C₆H₃Prⁱ ₂-2,6)C(Me)}₂CH]. The β-diketiminatochromium(II) compound 7 was prepared from CrCl₂ + 2 Li[{N(C₆H ₄Et-2)C(Me)}₂CH] (6); the latter became available from the corresponding equally new β-diketimine 5 and LiBuⁿ. Each of the compounds 1-7 was well characterised, including for 1-4 and 7 by single-crystal X-ray diffraction. Copyright

Full text of DOI:10.1002/zaac.201100266

ARTICLE
DOI: 10.1002/zaac.201100266
Synthesis and Structures of Five Crystalline Organometallic (Li/Y, Mg/Mg)
or Coordination (Mg, CrII, Y/Y) Complexes
Xue-Hong Wei,[a,b] Martyn P. Coles,[a] Peter B. Hitchcock,[a] and Michael F. Lappert*[a]
In Memory of Professor Kurt Dehnicke
Keywords: Chromium; Lithium/yttrium; Cyclopentadienyl; Magnesium; β-Diketiminates; Yttrium β-diketonate
Abstract. Yttrium(III) chloride was the ultimate precursor of the crystal-
line compounds [Y{η5-C5H4(CH(SiMe3)2)}2(μ-Cl)2Li(THF)2] (1),
[Y{(OC(But))2CH}2{μ-OC(But)C(H)C(But)O}]2 (2), [{Mg(CH2SiMe3)-
(μ-CH2SiMe3)(THF)}2] (3) and [Mg(CH2SiMe3){(N(C6H3Pri2-2,6)-
C(Me))2CH}(THF)] (4). Thus, the precursors were: YCl3 + 2 Li[η5-C5H4-
{CH(SiMe3)2}] for 1, [Y{N(SiMe3)2}3] + 3 [ButC(O)]2CH2 for 2, and
YCl3 + 3 Mg(CH2SiMe3)Cl for 3; whereas 4 was obtained from 3 + 2
H[{N(C6H3Pri2-2,6)C(Me)}2CH]. The β-diketiminatochromium(II) com-
pound 7 was prepared from CrCl2 + 2 Li[{N(C6H4Et-2)C(Me)}2CH] (6);
the latter became available from the corresponding equally new β-diket-
imine 5 and LiBun. Each of the compounds 1–7 was well characterised,
including for 1–4 and 7 by single-crystal X-ray diffraction.
chromium-based catalysts for CHO/CO2 copolymerisation, in-
cluding (salen)chromium(III) acetate [H2salen = N,NЈ-bis(3,5-
But2-salicylidene)-1,2-cyclohexene diamine].[4] Binuclear ana-
logues have been much studied because of the nature of the
Cr–Cr multiple bond.
Introduction
Our initial aim was directed to the synthesis of new types
of compounds as potential catalysts or procatalysts for the co-
polymerisation of an oxirane, specifically cyclohexene oxide
(CHO) and carbon dioxide. This was a continuation of an ear-
lier study on the preparation of various bimetallic (Li/Ca, Li/
Zn and Li/Li) diamides and their catalytic screening by BASF
colleagues at Ludwigshafen.[1] The selection then of binuclear
metal catalysts having a labile leaving group(s) was based on
Results and Discussion
Complex 1 was obtained by the general method described
the seminal study on dimeric β-diketiminatozinc complexes by earlier for the group 3 and 4f metal (M) compounds of formula
Coates et al.[2] [M{η5-C5H3(SiMe3)2-1,3}2(μ-Cl)2Li(L)2] [M = Sc, Y, La, or a
The rationale for the present initial choice of yttrium as the 4f metal and L = tetrahydrofuran (THF) or diethyl ether].[5]
metal was that a YX3 substrate, being a strong Lewis acid, was Thus, from yttrium(III) chloride and two equivalents of [bis-
expected to be readily responsive to nucleophilic attack by (trimethylsilyl)methyl]cyclopentadienyllithium[6] in tetra-
CHO or CO2. A strongly bound spectator ligand, such as the hydrofuran and successive removal of volatiles, extraction of
cyclopentadienyl in 1 or the terminal β-diketonate in 2, was a the residue into hexane/thf, and crystallisation furnished
further pre-requisite as were the readily displaceable bridging colourless crystals of the heterobimetallic bis(cyclopentadi-
ligands in 1 or 2. The formation of 3 from YCl3 and enyl)yttrium-μ-dichlorolithium complex 1 in good yield, i in
Mg(CH2SiMe3)Cl was unexpected; its conversion into the β- Scheme 1. From [Y{N(SiMe3)2}3], available from YCl3,[7] and
diketiminatomagnesium alkyl 4 provided another compound of three equivalents of bis(pivaloyl)methane in hexane, the prod-
possible catalytic interest. Finally, we chose to prepare the uct in almost quantitative yield was the crystalline, colourless
chromium(II) β-diketiminate 7, not only because mononuclear binuclear yttrium β-diketonate [Y{(OC(But))2CH}2{μ-OC(-
CrII compounds are rare,[3] but especially because of the im- But)C(H)C(But)O}]2 (2), ii in Scheme 1.
portant work of Darensbourg and co-workers on single site
Each of 1 and 2 was characterised by C, H, N microanalysis,
multinuclear NMR solution spectra and finally by single-crys-
tal X-ray diffraction.
* Prof. Dr. M. F. Lappert
Fax: +44-1273-876687
The molecular structure of the crystalline compound 1 is
shown in Figure 1. Selected geometrical parameters are listed
in Table 1. The yttrium atom is in a distorted tetrahedral
M1Cl1Cl2M2 environment, M1 and M2 being the centroids of
the cyclopentadienyl rings C1 to C5 and C13 to C17, respec-
tively. Of the six angles at the yttrium atom the four M–Y–Cl
E-Mail: m.f.lappert@sussex.ac.uk
[a] Department of Chemistry and Biochemistry
University of Sussex
Brighton BN1 9QJ, UK
[b] The School of Chemistry and Chemical Engineering
Shanxi University
Taiyuan 030006, P. R. China
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/zaac.201100266 or from the author. range from 105.5 to 110.8o, and the Cl1–Y–Cl2 and M1–Y–
Z. Anorg. Allg. Chem. 2011, 637, 1807–1813
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ARTICLE
Scheme 1. Reagents and conditions: i, 2 Li[η5-C5H4{CH(SiMe3)2}], THF, 0 °C; ii, 3 [ButC(O)]2CH2, C6H14, –78 °CǞ20 °C; iii, 3
Mg(CH2SiMe3)Cl, Et2O, –30 °CǞ20 °C; iv, H[{N(C6H3Pri2-2,6)C(Me)}2CH], THF, 0 °C.
M2 are significantly narrower and wider, respectively. Of the Table 1. Selected bond lengths /Å and angles /° for 1 (M1 and M2 are
the centroids of the C1 to C5 and C13 to C17 rings, respectively.
Y–M, Y–Cl and Li–Cl bond pairs, the Y–Cl distances are al-
most 0.3 Å longer than the Y–M or the Y–Cl distances. The
four-coordinate, distorted tetrahedral lithium atom has its dis- Y–Cl1
Y–M1
2.365(3)
2.634(1)
2.366(6)
1.904(6)
1.907(3)
1.855(3)
1.523(4)
Y–M2
Y–Cl2
2.367(3)
2.631(1)
2.352(6)
1.923(6)
1.908(3)
1.890(3)
1.517(4)
Li–Cl1
Li–Cl2
Li–O2
C18–Si3
C18–Si4
C13–C18
tances to Cl1 or Cl2 ca. 0.45 Å longer than those to O1 or O2,
Li–O1
whereas the six angles centered at the lithium atom range from
C6–Si1
the Cl1–Li–Cl2 at ca. 98° to the Cl2–Li–O1 at ca. 118°. The
C6–Si2
C1–C6
YCl1LiCl2 core is rhomboidal, with the endocyclic angle at
the yttrium atom substantially narrower than that at lithium.
M1–Y–M2
M1–Y–Cl1
M1–Y–Cl2
Y–Cl1–Li
Cl1–Li–Cl2
Cl1–Li–O1
Cl1–Li–O2
131.0(1)
105.5(1)
109.0(1)
87.91(15)
98.4(2)
Cl1–Y–Cl2
M2–Y–Cl1
M2–Y–Cl2
Y–Cl2–Li
O1–Li–O2
Cl2–Li–O1
Cl2–Li–O2
85.42(1)
110.8(1)
105.6(1)
88.25(16)
107.3(3)
118.2(3)
106.8(3)
111.2(3)
115.2(3)
Y 2.362(1) Å out of C1C2C3C4C5 plane
Y –2.363(1) Å out of C13C14C15C16C17 plane
C6 –0206(5) Å out of C1C2C3C4C5 plane
C18 0.156(5) Å out of C13C14C15C16C17 plane
Dihedral angles /°:
C1C2C3C4C5 / C13C14C15C16C17: 49.6(1)
Cl1–Y–Cl2 / M1–Y–M2: 86.64
Cl1–Li–Cl2 / O1–Li–O2: 84.14
Figure 1. Molecular structure of and atom numbering scheme for
Y{η5-C5H4(CH(SiMe3)2)}2(μ-Cl)2Li(THF)2] (1).
The structure of
a
related neodymium compound
[NdCpЈЈ2(μ-Cl)2Li(THF)2] [CpЈЈ = η-C5H3(SiMe3)2-1,3] is
long known;[5] it has a rhomboidal NdClLiCl core. Some key
geometrical parameters are shown in A.[5c]
The molecular structure of the crystalline dinuclear com-
pound 2 is shown in Figure 2. Selected bond lengths and
angles are listed in Table 2 and Table 3, respectively. Each six- ‘YOCCCO’ rings (O1,O2- and O3,O4-centred to Y1; O9,O10-
coordinate yttrium atom is the junction of two terminal and O11,O12-centred to Y2) and of the O5C23C24C25O6 and
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Five Crystalline Organometallic or Coordination Complexes
O7C34C35C36O8 bridges. The eight terminal Y–O distances Table 3. Selected bond angles /° for 2.
of 2.28 Ϯ 0.02 Å are only slightly shorter than the two Y–O
O1–Y1–O2
O1–Y1–O3
75.63(10) O6–Y2–O8
76.00(10) O6–Y2–O9
137.53(10) O6–Y2–O10
145.94(10) O6–Y2–O11
89.88(10) O6–Y2–O12
78.69(10) O8–Y2–O9
123.71(11) O8–Y2–O10
77.88(10) O8–Y2–O11
152.92(10) O8–Y2–O12
72.50(10) O9–Y2–O10
119.06(11) O9–Y2–O11
120.38(10) O9–Y2–O12
75.73(10) O10–Y2–O11
82.33(10) O10–Y2–O12
105.77(10) O11–Y2–O12
104.40(10)
88.10(10)
153.23(10)
119.75(10)
84.11(10)
145.13(10)
79.18(10)
121.23(10)
76.24(10)
75.85(10)
76.46(10)
138.16(10)
77.60(10)
122.06(10)
72.20(10)
131.8(3)
133.1(3)
124.6(4)
125.0(4)
123.5(4)
137.7(3)
137.8(3)
123.8(4)
bridges of 2.35 Ϯ 0.01 Å. In [Y{OC(But)C(H)C(But)O}3], the
Y–O bond lengths range from 2.128(19) to 2.298(12) Å, i.e., O1–Y1–O4
O1–Y1–O5
2.21 Ϯ 0.09 Å, and the O,OЈ-β-diketonato bite angles are
O1–Y1–O7
77.8(7) and 87.2(4)°.[8] The corresponding angles for the ter-
O2–Y1–O3
minal ligands of 2 are 74.1 Ϯ 1.5°. One of the ligands at each
O2–Y1–O4
yttrium atom [(O3C12C13C14O2) and (O9C45C46C47O10)]
is more closely π-delocalised than the other [(O1to O4) and
(O11 to O12)], as particularly evident by comparing the C–C
distances (e.g., C12–C13 ≈ C13–C14 but C1–C2 Ͼ C2–C3).
The two bond lengths in each bridging ligand are also unequal,
i.e., C23–C24 Ͼ C24–C25 and C35–C36 Ͼ C34–C35.
O2–Y1–O5
O2–Y1–O7
O3–Y1–O4
O3–Y1–O5
O3–Y1–O7
O4–Y1–O5
O4–Y1–O7
O5–Y1–O7
Y1–O1–C1
Y1–O2–C3
C1–C2–C3
C2–C1–O1
C2–C3–O2
Y1–O3–C12
Y1–O4–C14
C12–C13–
C14
131.4(3)
134.0(3)
125.3(4)
124.4(4)
123.6(4)
138.0(3)
137.4(3)
123.4(4)
Y2–O9–C45
Y2–O10–C47
C45–C46–C47
C46–C45–O9
C46–C47–O10
Y2–O11–C56
Y2–O12–C58
C56–C57–C58
C13–C12–O3 123.4(4)
C13–C14–O4 123.8(4)
C57–C56–O11
C57–C58–O12
Y2–O8–C36
122.5(4)
123.6(4)
129.1(3)
125.1(4)
Y1–O5–C23
C23–C24–
C25
130.7(3)
125.7(4)
C34–C35–C36
C24–C23–O5 121.4(4)
C24–C25–O6 123.8(4)
C35–C34–O7
C35–C36–O8
C34–O7–Y1
123.5(4)
123.0(4)
128.6(2)
C25–O6–Y2
127.6(2)
Dihedral angles /°:
O1–Y1–O2 / O3–Y1–O4: 89.35
O1–Y1–O2 / O6–Y1–O7: 85.36
O3–Y1–O4 / O6–Y1–O7 60.27
O7–Y2–O8 / O9–Y2–O10: 85.92 O7–Y2–O8 / O11–Y2–O12:
51.80
O1–Y1–O2 / O5–Y1–O6: 85.34
O3–Y1–O4 / O5–Y1–O6: 53.70
O5–Y1–O6 / O6–Y1–O7: 66.04
Figure 2. Molecular structure of and atom numbering scheme for
[Y{(OC(But))2CH}2{μ-OC(But)C(H)C(But)O}]2 (2).
O7–Y2–O8 / O6–Y2–O7: 66.25
O9–Y2–O10 / O11–Y2–O12:
87.77
Table 2. Selected bond lengths /Å for 2.
O9–Y2–O10 / O6–Y2–O7: 83.04 O11–Y2–O12 / O6–Y2–O7:
61.94
Y1–O1
Y1–O2
Y1–O3
Y1–O4
Y1–O5
Y1–O7
O1–C1
O2–C3
C1–C2
C2–C3
O3–C12
O4–C14
C12–C13
C13–C14
O5–C23
O6–C25
C23–C24
C24–C25
2.278(3)
2.255(3)
2.297(3)
2.263(3)
2.289(2)
2.350(3)
1.263(5)
1.268(5)
1.410(7)
1.388(7)
1.264(5)
1.277(5)
1.396(6)
1.391(6)
1.260(5)
1.329(5)
1.427(6)
1.361(6)
Y2–O6
Y2–O8
Y2–O9
2.353(2)
2.298(3)
2.268(3)
2.242(3)
2.313(3)
2.256(3)
1.318(5)
1.257(5)
1.373(6)
1.415(6)
1.260(5)
1.273(5)
1.405(6)
1.401(6)
1.272(6)
1.282(5)
1.412(6)
1.376(6)
Y2–O10
Y2–O11
Y2–O12
O7–C34
O8–C36
C34–C35
C35–C36
O9–C45
O10–C47
C45–C46
C46–C47
O11–C56
O12–C58
C56–C57
C57–C58
verting MgCl2 into [MgCl][YCl4]; alternatively that process
may have been driven by the precipitation of MgCl2.
The β-diketiminatomagnesium alkyl 4 was obtained from
[{Mg(CH2SiMe3)(μ-CH2SiMe3)(THF)}2] (3) and two equiva-
lents of the β-diketimine H[{N(C6H3Pri2-2,6)C(Me)}2CH]
(Scheme 1). Each of the colourless, crystalline compounds 3
and [Mg(CH2SiMe3){(N(C6H3Pri2-2,6)C(Me))2CH}](THF)]
(4) was isolated in good yield, and characterised by C,H,N
microanalysis, C6D6 solution 1H and 13C{1H} NMR spectra at
ambient temperature, and single-crystal X-ray diffraction.
The molecular structure of the crystalline dialkylmagnesium
compound 3 is illustrated in Figure 3, and selected geometrical
parameters are listed in Table 4. Its core is the Mg1C1Mg2C5
Complex 3 was prepared by a serendipitous route. Thus, it rhombus, with Mg1–C1 ≈ Mg2–C5 at 2.353 Ϯ 0.02 and Mg1–
was isolated from yttrium chloride with three equivalents of C5 ≈ Mg2–C1 at 2.224 Ϯ 0.009 Å (cf., the exocyclic Mg–C
the Grignard reagent Mg(CH2SiMe3)Cl in diethyl ether and distances at 2.125
Ϯ 0.05 Å), and the 2.114(7) Å in
crystallisation from hexane/ THF. Evidently the YCl3 took no [{Mg(CHR2)(μ-Br)(OEt2)}2].[9] The endocyclic angles at the
direct part in this reaction other than possibly facilitating the magnesium atoms are wider by ca. 23° than those at the carbon
Schlenk redistribution 2 Mg(R)Cl ↔ MgR2 + MgCl2 by con- atoms. Each magnesium atom is the centre of a distorted tetra-
Z. Anorg. Allg. Chem. 2011, 1807–1813
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X.-H. Wei, M. P. Coles, P. B. Hitchcock, M. F. Lappert
ARTICLE
hedron. The six O–Mg–C or C–Mg–C angles at M1 (M2)
range from 98.2° (99.0°) to 126° (126.5°). By contrast to 3,
the crystalline [MgBut(μ-But)]2 has a folded Mg1C1Mg2C2
ring and planar MgC3 wings; its terminal Mg–C bonds are ca.
0.15 Å shorter than the bridging Mg–C distances of 2.30 Å.[10]
Figure 4. Molecular structure of and atom numbering scheme for
[Mg(CH2SiMe3){(N(C6H3Pri2-2,6)C(Me))2CH}](THF)] (4).
Figure 3. Molecular structure of and atom numbering scheme for
[{Mg(CH2SiMe3)(μ-CH2SiMe3)(THF)}2] (3).
Table 5. Selected bond lengths /Å and angles /° for 4.
Mg–N1
Mg–C30
C30–Si
N2–C3
N2–C18
C2–C3
2.0764(13)
2.1300(17)
1.8332(17)
1.327(2)
1.444(2)
1.409(2)
Mg–N2
Mg–O1
N1–C1
N1–C6
C1–C2
2.0830(14)
2.0785(12)
1.332(2)
1.444(2)
1.405(2)
Table 4. Selected bond lengths /Å and angles /° for 3.
Mg1–C1
Mg1–C5
Mg1–C9
Mg1–O1
C1–Si1
2.355(6)
2.215(7)
2.120(7)
2.055(4)
1.842(6)
1.829(7)
Mg2–C1
Mg2–C5
Mg2–C13
Mg2–O2
C5–Si2
2.232(7)
2.351(6)
2.129(7)
2.051(4)
1.854(6)
1.828(7)
N1–Mg–N2
N2–Mg–C30
N2–Mg–O1
Mg–N1–C1
Mg–N1–C6
Mg–C30–Si
92.85(5)
N1–Mg–C30
N1–Mg–O1
C30–Mg–O1
Mg–N2–C3
Mg–N2–C18
131.53(6)
100.58(5)
109.70(6)
119.47(10)
121.51(10)
C9–Si3
C13–Si4
116.80(6)
100.36(5)
119.37(10)
123.79(10)
128.38(9)
C1–Mg1–C5
C1–Mg1–C9
C5–Mg1–C9
C1–Mg1–O1
C5–Mg1–O1
C9–Mg1–O1
Mg1–C1–Mg2
Mg1–C1–Si1
Mg1–C9–Si3
101.7(2)
114.9(3)
126.0(3)
98.2(2)
105.2(2)
107.2(3)
78.3(2)
C1–Mg2–C5
C1–Mg2–C13
C5–Mg2–C13
C1–Mg2–O2
C5–Mg2–O2
C13–Mg2–O2
Mg1–C5–Mg2
Mg2–C5–Si2
Mg2–C13–Si4
101.3(2)
126.5(3)
115.7(3)
103.7(2)
99.0(2)
106.8(3)
78.7(2)
173.1(4)
121.3(4)
C2 0.126 Å out of N1C1C2C3N2 plane
Mg 0.596 Å out of N1C1C2C3N2 plane
C6 0.420 Å out of N1C1C2C3N2 plane
C18 0.317 Å out of N1C1C2C3N2 plane
173.6(4)
122.2(4)
Dihedral angles /°:
O1–Mg1–C9 / C1–Mg1–C5: 88.39
O2–Mg2–C13 / C1–Mg2–C5: 89.45
The molecular structure of the crystalline compound 4 is
depicted in Figure 4. Its selected geometrical parameters,
found in Table 5, are very similar to those of the corresponding
methyl compound, reported by Bailey et al.;[11] the Mg–C bond
length of 2.107(4) Å of the latter is slightly shorter than the
Mg–C30 bond length of 4 (which is of almost identical length
to those of the Mg–C bonds of 3).
Complex 7 was prepared by the route shown in Scheme 2.
Its precursors were the new lithium β-diketiminate 6 and the β-
diketimine 5, obtained by minor variations of procedures well
established for N,NЈ-diaryl analogues (e.g., see ref. [2]). Thus,
addition of chromium(II) chloride to two equivalents of 6 in
Scheme 2. Synthesis of the β-diketiminatochromium(II) compound 7.
Complex 7 was characterised by C, H, N microanalysis, and
tetrahydrofuran and successive removal of volatiles, extraction its X-ray crystal structure. Its paramagnetism, with μeff = 4.85
with hexane and storage of the concentrated hexane solution BM at ambient temperature, measured by the Evans method in
at –25 °C afforded deep purple crystals of 7 in good yield.
C6D6, is consistent with 7 having four unpaired electrons.
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Five Crystalline Organometallic or Coordination Complexes
The molecular structure of the crystalline chromium(II) β- Table 6. Selected bond lengths /Å and angles /° for 7.
diketiminate 7 is shown in Figure 5. Selected bond lengths and
Cr–N1
Cr–N2
2.060(3)
2.055(3)
1.337(4)
1.323(4)
1.406(5)
1.396(5)
1.437(4)
1.432(4)
Cr–N3
2.049(3)
2.061(3)
1.327(4)
1.339(4)
1.396(5)
1.396(5)
1.433(4)
1.438(4)
angles are assembled in Table 6. The chromium atom is the
Cr–N4
centre of a distorted tetrahedron. Each of the two ‘CrNCCCN’ N1–C1
N3–C22
N4–C24
C22–C23
C23–C24
N3–C27
N4–C35
N2–C3
rings is of shallow boat form and is almost completely π-delo-
C1–C2
calised, as evident by the near identical pairs of endocyclic
C2–C3
Cr–N, N–C and C–C bond lengths. By contrast, the corre-
N1–C6
sponding bond angles differ for each pair, most obviously for
those at the two nitrogen atoms which vary by almost 5° for
N1/N2 or ca. 4° for N3/N4. The angle between the two
N1CrN2 and N3CrN4 planes is 57.33°. In crystalline
[Cr{(N(C6H3Pri2-2,6)C(Me))2CH}2] each of the planar
N2–C14
N1–Cr–N2
N1–Cr–N3
N1–Cr–N4
N1–C1–C2
88.10(11)
104.48(11)
133.30(11)
124.1(3)
122.2(3)
127.4(3)
119.7(2)
120.9(2)
117.3(3)
124.5(2)
115.9(2)
119.6(3)
N3–Cr–N4
N3–Cr–N2
N2–Cr–N4
88.12(11)
150.20(11)
102.90(11)
121.1(3)
123.5(3)
127.8(3)
126.1(2)
114.1(2)
119.3(3)
122.4(2)
117.3(2)
118.2(3)
N3–C22–C23
N4–C24–C23
C22–C23–C24
Cr–N3–C22
Cr–N3–C27
C22–N3–C27
Cr–N4–C24
Cr–N4–C35
C24–N4–C35
‘CrNCCCN’ rings has N–C bonds which differ by ca. 0.02 Å, N2–C3–C2
and the dihedral angle between the two rings is 80.3°.[12]
C1–C2–C3
Cr–N1–C1
Cr–N1–C6
C1–N1–C6
Cr–N2–C3
Cr–N2–C14
C3–N2–C14
Cr 0.711 Å out of N1C1C2C3N2 plane
Cr 0.570 Å out of N3C22C23C24N4 plane
C2 0.100 Å out of N1C1C2C3N2 plane
C23 0.119 Å out of N3C22C23C24N4 plane
Dihedral angles /°:
N1–Cr–N2 / N3–Cr–N4: 57.33
potassium alloy (C6H14). The C6D6 for NMR spectroscopy was stored
over molecular sieves (A4). The NMR spectra were obtained from
solutions in C6D6 at 293 K, using a Bruker WM-300 instrument (1H,
300.1; 13C, 75.5; and 7Li, 116.6 MHz) and referenced internally to
residual solvent resonances (1H, 13C), or externally (7Li using aq.
LiNO3). Elemental analyses were obtained at The Metropolitan Uni-
versity, London. Melting points were measured in sealed capillaries
and are uncorrected. The magnetic moment of 7 was determined by
Evans’ method.[14] Electron impact mass spectra were taken from solid
samples using a Kratos MS 80 RF instrument. The compounds
[Y{N(SiMe3)2}3],[7] H[{N(C6H3Pri2-2,6)C(Me)}2CH][13] were ob-
tained by published procedures; CrCl2, YCl3, {ButC(O)}2CH2 and the
ethereal solution of Mg(CH2SiMe3)Cl were commercial samples (Ald-
rich) which were rigorously dried before use.
Figure 5. Molecular structure of and atom numbering scheme for
[Cr{(N(C6H4Et-2)C(Me))2CH}2] (7).
Conclusions
Five new crystalline complexes, the binuclear Y/Li (1), Y/
Y (2), Mg/Mg (3) and the mononuclear magnesium (4) and
chromium(II) (7) complexes have been prepared in good yield.
Each has been characterised by microanalysis and multinuclear
1H NMR ambient temperature solution spectra and X-ray mo-
lecular structures. The isolation of both 2 and 3 [from YCl3 +
3 Mg(CH2SiMe3)Cl] was unexpected. These compounds 1–4
and 7 formed part of a screening programme aimed at identi-
fying new catalysts or cocatalysts for CHO/CO2 copolymeris-
ation. In the event, tests (at BASF, Ludwigshafen) have re-
Preparation of [Y{η5-C5H4(CH(SiMe3)2)}2(μ-Cl)2Li(THF)2]
(1)
Yttrium(III) chloride (0.36 g, 1.84 mmol) was added in small portions
to a solution of Li[η5-C5H4{CH(SiMe3)2}][6] (0.85 g, 3.68 mmol) in
vealed that none has proved to be a viable catalyst, even in the tetrahydrofuran (30 cm3) at 0 °C. The resulting mixture was warmed
to ca. 25 °C and set aside for 18 h with stirring. Volatiles were removed
in vacuo and the residue was extracted into hexane/THF (3:1, 40 cm3).
The filtered extract was concentrated in vacuo to ca. 10 cm3 and after-
wards stored at –25 °C for 3 days, yielding colourless crystals of 1
(1.02 g, 73%) (Anal. C32H62Cl2LiO2Si4Y: C, 50.7; H, 8.25. Found: C,
49.9; H, 7.98%). m.p. 84 °C (decomp.). 1H NMR (C6D6): δ = 0.23 (s,
36 H, CH3), 1.40 (quint, 8 H, THF), 2.19 [s, 2 H, CH(SiMe3)2], 3.57
presence of five equivalents of dimethylzinc and 25 bar CO2
at 80 °C.
Experimental Section
Syntheses were carried out under an atmosphere of argon or in a vac-
uum, using Schlenk apparatus and vacuum line techniques. The sol- (t, 8 H, THF), 6.09 (t, 4 H, C5H4), 6.38 ppm (t, 4 H, C5H4); 13C{1H}
vents used were reagent grade or better and were freshly distilled under
dry nitrogen gas and freeze/thaw degassed prior to use. The drying
NMR (C6D6): δ = 1.56 (CH3), 19.75 [CH(SiMe3)2], 25.66 (THF),
67.74 (THF); 111.35, 111.75, 130.83 ppm (C5H4); 7Li{1H} NMR
agents employed were sodium benzophenone (Et2O, THF) or sodium- (C6D6): δ = –2.44 ppm.
Z. Anorg. Allg. Chem. 2011, 1807–1813
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1811

X.-H. Wei, M. P. Coles, P. B. Hitchcock, M. F. Lappert
ARTICLE
Preparation of [Y{(OC(But))2CH}2{μ-OC(But)C(H)C(But)
O}]2 (2)
4 (3.00 g, 82%), m.p. 160–162 °C (Anal. C37H60MgN2OSi: C, 73.9;
H, 10.06; N, 4.66. Found: C, 73.7; H, 9.80; N, 4.37%). 1H NMR
(C6D6): δ = –1.64 ppm (s, 2 H, CH2), –0.06 (s, 9 H, SiCH3), 1.12 [d,
12 H, CH(CH3)2], 1.15 [d, 12 H, CH(CH3)2], 1.35 (m, 4 H, THF),
1.65 (s, 6 H, CH3), 3.34 (hept, 4 H, CHMe2), 3.74 (t, 4 H, THF), 4.79
[s, 1 H, CH(CMe)2], 7.10 ppm (m, 6 H, C6H3); 13C{1H} NMR (C6D6):
δ = –4.40 (CH2), 4.06 (SiCH3), 24.28 (CH3), 24.53 (THF), 25.19
(CHCH3), 25.38 (CHCH3), 28.21 (CHMe2), 70.16 (THF), 94.83
[CH(CMe)2]; 123.94, 125.31, 142.23, 146.08 (C6H3); 168.14 ppm
(CN). EI-MS: m/z (%, assignment): 528 {12, [M – THF]+}, 513 (90,
[M – THF – CH3]+), 443 (100, [Mg{N(C6H3Pri2-2,6)C(Me)}2CH]+),
73 (52, [SiMe3]+).
Yttrium(III) bis(trimethylsilyl)amide (1.05 g, 1.84 mmol) was added in
small portions to a solution of the β-diketone [ButC(O)]2CH2 (1.02 g,
5.54 mmol) in hexane (30 cm3) at –78 °C, afterwards stirred at ca.
25 °C for 6 h. Volatiles were removed in vacuo and the residue was
extracted with hexane (40 cm3). The filtered extract was concentrated
in vacuo to ca. 10 cm3, afterwards set aside at –25 °C for ca. 12 h,
whereafter colourless crystals of
2
(1.74 g, 96%) (Anal.
C66H114O12Y2: C, 62.1; H, 9.00. Found: C, 61.7; H, 8.86%), m.p. 121–
123 °C were obtained. 1H NMR (C6D6): δ = 1.13 (s, 108 H, CH3),
5.93 ppm (s, 6 H, CH); 13C{1H} NMR (C6D6): δ = 28.20 (CH3), 41.07
(CMe3), 93.55 (CH), 203.03 ppm (CO). EI-MS: m/z (%, assignment):
638, (72, [M/2]+), 582, (93, [M/2
[{ButC(O)}2CH]+, 57, (52, [But]+).
- -
But]+, 456, (96, [M/2
Preparation of H[{N(C6H4Et-2)C(Me)}2CH] (5)
Compound 5 (67%) (Anal. C21H26N2: C, 82.3; H, 8.55; N, 9.14.
Found: C, 82.3; H, 8.39; N, 8.97%) was prepared by using a similar
procedure as for its N,NЈ-diaryl analogue.[2] 1H NMR (CDCl3): δ =
1.03 (t, 6 H, CH2CH3), 1.81 (s, 6 H, CH3), 2.50 (q, 4 H, CH2CH3),
4.80 (s, 1 H, CH), 6.81 (d, 2 H, C6H4), 6.94 (m, 2 H, C6H4), 7.06 (d,
2 H, C6H4), 7.10 (m, 2 H, C6H4), 12.44 ppm (NH); 13C{1H} NMR
(CDCl3): δ = 14.70 (CH2CH3), 21.09 (CH3), 25.04 (CH2CH3), 96.58
(CH); 123.69, 124.14, 126.25, 128.78, 137.08, 144.25 (C6H4);
160.04 ppm (CN).
Preparation of [{Mg(CH2SiMe3)(μ-CH2SiMe3)(THF)}2] (3)
Trimethylsilylmethylmagnesium chloride (40 cm3 of a 1.0 m solution
in Et2O, 40.00 mmol) was added slowly to a suspension of YCl3
(2.60 g, 13.33 mmol) in diethyl ether (50 cm3) at –30 °C. The mixture
was set aside at ca. 25 °C for 18 h, and afterwards filtered. Volatiles
were removed in vacuo and the residue was extracted with hexane/
THF (4:1, 50 cm3). The filtered extract was concentrated in vacuo to
ca. 25 cm3. After ca. 18 h at –25 °C, colourless crystals of 3 (3.10g,
86%) (Anal. C24H60Mg2O2Si4: C, 53.2; H, 11.16. Found: C, 52.9; H,
11.02%) were obtained. 1H NMR (C6D6): δ = –1.28 ppm (s, 4 H,
CH2), 0.35 (s, 18 H, CH3), 1.15 (quint, 4 H, THF), 3.58 ppm (t, 4 H,
THF); 13C{1H} NMR (C6D6): δ = –4.19 (CH2), 4.35 (CH3), 24.93
(THF), 69.44 ppm (THF).
Preparation of Li[{N(C6H4Et-2)C(Me)}2CH] (6)
Compound 6 (94%) (Anal. C21H25LiN2: C, 80.7; H, 8.07; N, 8.97.
Found C, 82.1; H, 8.49; N, 9.02%) was prepared by using a similar
procedure as for its N,NЈ-diaryl analogue.[15] 1H NMR (C6D6): δ =
1.16 (t, 6 H, CH2CH3), 1.81 (s, 6 H, CH3), 2.58 (q, 4 H, CH2CH3),
4.86 (s, 1 H, CH), 6.78 (d, 2 H, C6H4), 6.96 (m, 2 H, C6H4), 7.08 (d,
2 H, C6H4), 7.16 ppm (m, 2 H, C6H4); 13C{1H} NMR (C6D6): δ =
15.13 (CH2CH3), 22.15 (CH3), 25.04 (CH2CH3), 93.26 (CH); 121.23,
123.26, 125.25, 127.69, 135.37, 141.85 (C6H4); 162.66 ppm (CN);
7Li{1H} NMR (C6D6): δ = –2.16 ppm.
Preparation of [Mg(CH2SiMe3){N(C6H3Pri2-2,6)
C(Me)}2CH](THF)] (4)
The trimethylsilylmethylmagnesium compound 3 (1.65 g, 3.05 mmol)
was added in small portions to a solution of H[{N(C6H3Pri2-2,6)
C(Me)}2CH] (2.55 g, 6.10 mmol) in tetrahydrofuran (30 cm3) at 0 °C.
The mixture was set aside at ca. 25 °C for 18 h, whereafter volatiles
were removed in vacuo. The residue was extracted with hexane
Preparation of [Cr{(N(C6H4Et-2)C(Me))2CH}2] (7)
(50 cm3). The filtered extract was concentrated in vacuo to ca. 20 cm3 Chromium(II) chloride (0.34 g, 2.76 mmol) was added in small por-
and after storage for ca. 18 h at –25 °C yielded colourless crystals of tions to a solution of Li[{N(C6H4Et-2)C(Me)}2CH] (6) (1.73 g,
Table 7. Crystal structure and refinement data for 1–4 and 7.
Compound
1
2
3
4
7
Formula
M
C32H62Cl2LiO2Si4Y
757.93
C66H114O12Y
1277.39
C24H60Mg2O2Si4 C37H60MgN2OSi
C42H50CrN4
662.86
541.70
601.27
Crystal system
Space group
a /Å
b /Å
c /Å
α /deg
β /deg
Monoclinic
P21/c (No. 14)
11.3004(1)
30.5737(3)
12.4318(1)
90
102.155(1)
90
4198.83(6)
4
1.66
6004, 0.064
5241
0.037, 0.089
0.046, 0.094
Monoclinic
P21/n (No. 14) P ı (No. 2)
Triclinic
¯
Monoclinic
P21/c (No. 14)
18.4094(2)
12.9481(2)
16.1549(2)
90
105.568(1)
90
3709.51(8)
4
0.11
6496, 0.038
5515
0.042, 0.102
0.052, 0.107
Monoclinic
P21/c (No. 14)
11.4735(2)
11.6059(2)
27.9258(2)
90
96.133(1)
90
3697.32(11)
4
0.34
6444, 0.078
4403
0.061, 0.138
0.102, 0.157
12.1945(1)
27.6101(3)
21.8150(2)
90
105.110(1)
90
7091.0(1)
4
1.68
12350, 0.078
8922
0.059, 0.116
0.095, 0.129
10.0757(1)
10.6141(1)
38.2877(4)
89.677(1)
90.028(1)
63.437(1)
3662.36(6)
4
0.21
9355, 0.054
8111
0.080, 0.192
0.090, 0.196
γ /deg
V /Å3
Z
Absorption coeff. /mm–1
Unique reflections, Rint
Reflections with I Ͼ 2σ(I)
Final R indices [I Ͼ 2σ(I)], R1, wR2
R indices (all data), R1, wR2
1812
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© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2011, 1807–1813

Five Crystalline Organometallic or Coordination Complexes
5.54 mmol) in tetrahydrofuran (30 cm3) at –30 °C. The resulting deep
purple solution was set aside for 18 h at ca. 25 °C. Volatiles were
removed in vacuo and the residue was extracted with hexane (50 cm3).
The filtered extract was concentrated in vacuo to ca. 10 cm3 and after-
wards stored at –25 °C. After two days, deep purple crystals of 7
(1.44 g, 78%), m.p. 160 °C (decomp.), μeff = 4.85 BM (Anal.
C42H50CrN4: C, 76.1; H, 7.60; N, 8.45. Found C, 76.2; H, 7.34; N,
8.26%) were collected.
References
[1] P. B. Hitchcock, M. F. Lappert, X.-H. Wei, Dalton Trans. 2006,
1181.
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[3] A. R. Sadique, M. J. Heeg, C. H. Winter, J. Am. Chem. Soc. 2003,
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X-ray Crystallographic Studies for Compounds 1–4 and 7
Diffraction data were collected with a Nonius Kappa CCD dif-
fractometer, using monochromated Mo-Kα radiation, λ = 0.71073 Å at
173(2) K. Crystals were coated in oil and then directly mounted on
the diffractometer under a stream of cold nitrogen gas. The structures
were refined on all F2 using SHELXL-97;[16] for 3, the hydrogen
atoms of CH2 groups bonded to magnesium were refined and other
hydrogen atoms were in riding mode. Absorption corrections were ap-
plied using MULTISCAN. Drawings used ORTEP-3 for Windows
(30% ellipsoids for non-carbon atoms). In 3, there is one dimer in a
general position and two dimers on crystallographic inversion centres.
Further details are in Table 7.
[7] M. Westerhausen, M. Hartmann, A. Pfitzner, W. Schwarz, Z.
Anorg. Allg. Chem. 1995, 621, 837.
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[9] C. F. Caro, D. Phil. Thesis, University of Sussex, 1998; cf. C. F.
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[10] K. B. Starowieyski, J. Lewinski, R. Wozniak, J. Lipkowski, A.
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[11] P. J. Bailey, C. M. E. Dick, S. Fabre, S. Parson, J. Chem. Soc.,
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[12] L. A. MacAdams, W.-K. Kim, C. M. Liable-Sands, I. A. Guzei,
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[13] J. Feldman, S. J. McLain, A. Parthasarathy, W. J. Marshall, C. J.
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[15] M. Stender, R. J. Wright, B. E. Eichler, J. Prust, M. M. Olmstead,
H. W. Roesky, P. P. Power, J. Chem. Soc., Dalton Trans. 2000,
3465.
Supporting Information (see footnote on the first page of this article):
ORTEP figures for compounds 1–4 and 7.
Acknowledgments
[16] G. M. Sheldrick, SHELXL-97, University of Göttingen,
Göttingen, Germany, 1997.
We thank BASF (Ludwigshafen) and Drs. H. Görtz and G. Luinstra
for the award of a postdoctoral fellowship to X.-H. Wei. and A. V.
Protchenko for valuable discussions
Received: June 15, 2011
Z. Anorg. Allg. Chem. 2011, 1807–1813
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1813