Synthesis and characterization of magnesium and aluminum bis(phosphoranyl)methanediide complexes

Article abstract of DOI:10.1021/om900985f

The reaction of [CH₂(PPh₂=NSiMe₃)(PPh ₂=E)] (E = S (1), NSiMe₃ (2)) with Mg(Buⁿ) ₂ in refiuxing toluene afforded the magnesium bis(phosphoranyl) methanediide complexes [{(PPh₂=NSiMe₃)(PPh ₂=E)}CMgl₂ (E = S (3), NSiMe₃ (4)), respectively. The X-ray structures and DFT calculations of 3 and 4 show that they are bimetallic methanediide complexes of magnesium containing a strong Mg-C_{methaiiediide} electrostatic bonding. Treatment of 4 with water in toluene gave 2 and the magnesium hydroxide complex [HC(PPh₂= NSiMe₃)₂Mg(μ-OH)]₂ (5), confirmed by X-ray crystallography. The reaction of 1 with AlMe₃ in refiuxing toluene afforded the aluminum bis(phosphoranyl)methanediide complex [{(PPh ₂=NSiMe₃)(PPh₂=S)}CAlMe]₂ (6). The X-ray structure of 6 shows that a methanediide carbon is bonded to one aluminum atom. DFT calculations of 6 demonstrate that Al-C_msthanediide ls highly polar with weak covalent bonding, consistent with the topological analysis of electron densities of 6.

Full text of DOI:10.1021/om900985f

Organometallics 2010, 29, 939–944 939
DOI: 10.1021/om900985f
Synthesis and Characterization of Magnesium and Aluminum
Bis(phosphoranyl)methanediide Complexes
†
Jiayi Guo, Jia-Shin Lee, Ming-Choo Foo, Kai-Chung Lau, Hong-Wei Xi,
†
†
‡
§
§
Kok Hwa Lim, and Cheuk-Wai So*
,†
†
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences,
Nanyang Technological University, 637371 Singapore, Department of Biology and Chemistry,
‡
§
City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong, and Division of Chemical and
Biomolecular Engineering, School of Chemical and Biomedical Engineering, Nanyang Technological
University, 637459 Singapore
Received November 12, 2009
n
The reaction of [CH (PPh dNSiMe )(PPh dE)] (E = S (1), NSiMe (2)) with Mg(Bu ) in refluxing
2
2
3
2
3
2
toluene afforded the magnesium bis(phosphoranyl)methanediide complexes [{(PPh dNSiMe )-
3
2
(PPh dE)}CMg] (E = S (3), NSiMe (4)), respectively. The X-ray structures and DFT calculations
2 2 3
of 3 and 4 show that they are bimetallic methanediide complexes of magnesium containing a strong
Mg-Cmethanediide electrostatic bonding. Treatment of 4 with water in toluene gave 2 and the magnesium
hydroxide complex [HC(PPh dNSiMe ) Mg(μ-OH)] (5), confirmed by X-ray crystallography. The
2
3 2
2
reaction of 1 with AlMe in refluxing toluene afforded the aluminum bis(phosphoranyl)methanediide
3
complex[{(PPh dNSiMe )(PPh dS)}CAlMe] (6). The X-raystructure of 6 shows that a methanediide
2
3
2
2
carbon is bonded to one aluminum atom. DFT calculations of 6 demonstrate that Al-Cmethanediide is
highly polar with weak covalent bonding, consistent with the topological analysis of electron densities of 6.
Introduction
the salt elimination of [Li C(PPh dE) ] (E = NSiMe , S)
2 2 2 3
with metal halide or by the double deprotonation of [CH2-
PPh dE) ] (E = NSiMe , S) with metal alkyl or amide. For
example, the reaction of [CH (PPh dNSiMe ) ] with [Y-
The chemistry of metal bis(phosphoranyl)methanediide
1
(
2
2
3
complexes has attracted attention over the past few decades.
2
2
2
3 2
3
4
Main-group, transition-metal, and lanthanide-metal bis-
phosphoranyl)methanediide complexes were obtained by
(
CH SiMe ) (THF) ] afforded the yttrium-alkyl-alkylidene
2
3 3
2
(
5
complex [(PPh dNSiMe ) CdY(CH SiMe )(THF)]. Treat-
2
3 2
2
3
ment of [Li C(PPh dS) ] withPdCl (PPh ) gave the palladium
3 2
2
2
2
2
6
*To whom correspondence should be addressed. E-mail: CWSo@
carbene complex [(Ph P)PddC(PPh dS) ]. Recently, we have
3 2 2
ntu.edu.sg.
synthesized the (iminophosphoranyl)(thiophosphoranyl)methane
CH (PPh dNSiMe )(PPh dS)] and the lithium salt of the
geminal dianion [Li {C(PPh dS)(PPh dNSiMe )}]. They
(1) For recent reviews, see: (a) Panda, T. K.; Roesky, P. W. Chem.
[
Soc. Rev. 2009, 38, 2782. (b) Cantat, T.; M ꢀe zailles, N.; Auffrant, A.; Le
Floch, P. Dalton Trans. 2008, 1957. (c) Jones, N. D.; Cavell, R. G.
J. Organomet. Chem. 2005, 690, 5485. (d) Cavell, R. G.; Kamalesh Babu,
R. P.; Aparna, K. J. Organomet. Chem. 2001, 617-618, 158.
2
2
3
2
2
2
2
3
7
contain hard nitrogen and soft sulfur coordination sites. It
is anticipated that the coordination chemistry of [C(PPh d
(2) (a) Leung, W.-P.; Wang, Z.-X.; Li, H.-W.; Mak, T. C. W. Angew.
2
2-
2-
Chem., Int. Ed. 2001, 40, 2501. (b) Leung, W.-P.; Wang, Z.-X.; Li, H.-W.;
Yang, Q.-C.; Mak, T. C. W. J. Am. Chem. Soc. 2001, 123, 8123. (c) Hull, K.
L.; Noll, B. C.; Henderson, K. W. Organometallics 2006, 25, 4072.
NSiMe )(PPh dS)] is different from that of [C(PPh dE) ]
3 2 2 2
(E = NSiMe , S).
3
In this paper, we report the synthesis and characterization
of magnesium and aluminum bis(phosphoranyl)methanediide
(
2
d) Cantat, T.; Ricard, L.; Le Floch, P.; M ꢀe zailles, N. Organometallics
006, 25, 4965. (e) Orzechowski, L.; Jansen, G.; Harder, S. Angew. Chem.,
Int. Ed. 2009, 48, 3825. (f) Orzechowski, L.; Jansen, G.; Harder, S. J. Am.
Chem. Soc. 2006, 128, 14676. (g) Orzechowski, L.; Harder, S. Organome-
tallics 2007, 26, 5501. (h) Kasani, A.; McDonald, R.; Ferguson, M.; Cavell,
R. G. Organometallics 1999, 18, 4241.
complexes derived from [CH (PPh dNSiMe )(PPh dS)] or
2
2
3
2
[
CH (PPh dNSiMe ) ].
2 2 3 2
(
3) (a) Kamalesh Babu, R. P.; McDonald, R.; Decker, S. A.;
Klobukowski, M.; Cavell, R. G. Organometallics 1999, 18, 4226.
b) Kamalesh Babu, R. P.; McDonald, R.; Cavell, R. G. Organometallics
000, 19, 3462. (c) Cavell, R. G.; Kamalesh Babu, R. P.; Kasani, A.;
McDonald, R. J. Am. Chem. Soc. 1999, 121, 5805. (d) Kasani, A.; Kamalesh
Babu, R. P.; McDonald, R.; Cavell, R. G. Angew. Chem., Int. Ed. 2001, 40,
Results and Discussion
(
2
Synthesis and Characterization of Magnesium Bis(phos-
phoranyl)methanediide Complexes. The reaction of [CH (PPh d
NSiMe )(PPh dE)] (E = S (1), NSiMe (2)) with Mg(Bu ) in
3 2 3 2
2
2
n
4
1
400. (e) Kasani, A.; McDonald, R.; Cavell, R. G. Chem. Commun. 1999,
993. (f) Jones, N. D.; Lin, G.; Gossage, R. A.; McDonald, R.; Cavell, R. G.
Organometallics 2003, 22, 2832. (g) Kamalesh Babu, R. P.; McDonald, R.;
Cavell, R. G. Chem. Commun. 2000, 481.
(5) Liddle, S. T.; McMaster, J.; Green, J. C.; Arnold, P. L. Chem.
Commun. 2008, 1747.
(6) Cantat, T.; M ꢀe zailles, N.; Ricard, L.; Jean, Y.; Le Floch, P.
(4) (a) Kasani, A.; Ferguson, M.; Cavell, R. G. J. Am. Chem. Soc.
2
000, 122, 726. (b) Cantat, T.; Arliguie, T.; No €e l, A.; Thu ꢀe ry, P.; Ephritikhine,
M.; Le Floch, P.; M ꢀe zailles, N. J. Am. Chem. Soc. 2009, 131, 963. (c) Mills,
D. P.; Cooper, O. J.; McMaster, J.; Lewis, W.; Liddle, S. T. Dalton Trans.
Angew. Chem., Int. Ed. 2004, 43, 6382.
(7) Chen, J.-H.; Guo, J.; Li, Y.; So, C.-W. Organometallics 2009, 28,
4617.
2009, 4547.
r 2010 American Chemical Society
Published on Web 01/21/2010
pubs.acs.org/Organometallics

9
40 Organometallics, Vol. 29, No. 4, 2010
Guo et al.
Figure 1. Molecular structure of 3 with thermal ellipsoids at the
0% probability level.
5
Figure 2. Molecular structure of 4 with thermal ellipsoids at the
5
0% probability level.
Scheme 1. Synthesis of 3 and 4
(
deg) are given in Table 1. The magnesium centers in
compounds 3 and 4 adopt a distorted-tetrahedral geometry,
being bound to the methanediide carbon atoms and co-
ordinated to two imino nitrogen atoms or two sulfur atoms
of the ligand. With the Mg(1)C(1)Mg(2)C(2) ring as the
base, compounds 3 and 4 show an “open-box”-like struc-
ture framework. The structures of 3 and 4 are similar to that
2
f
of [(PPh dNSiMe ) CCa] . The Mg-C bonds (3, average
2
3 2
˚ ˚
2
2.241 A; 4, average 2.235 A) are significantly shorter than
that of the magnesium methanide complexes [HC(PPh d
NSiMe ) Mg(μ-Cl)] (2.460(8) A) and [HC(PPh dNSiMe ) -
2
˚
3
2
2
2
3 2
9
refluxing toluene afforded the magnesium bis(phosphoranyl)-
methanediide complexes [{(PPh dNSiMe )(PPh dE)}CMg]
˚
MgI(THF)] (2.573(6) A). The Mg-N bonds (3, average 2.035
˚ ˚
A; 4, average 2.046 A) are shorter than those of [HC(PPh d
2
2
3
2
2
(E = S (3), NSiMe (4)), respectively (Scheme 1). The inter-
3
˚
NSiMe ) Mg(μ-Cl)] (average 2.134 A) and [HC(PPh dNSi-
2
3 2
2
9
mediate [H CdMg] can be synthesized by the R-elimination
˚
Me ) MgI(THF)] (average 2.110 A), but they are slightly
3 2
2
of methane from Me Mg or by the disproportionation of
[
CM] (M = Ca, Ba) have been synthesized by the reaction of
2
longer than the Mg-Namide σ bonds in the magnesium amide
complexes [(Et O)Mg(Cl){N(SiMe ) }] (1.970(3) A) and
] (1.963(6), 1.969(6) A). The Mg-S
8
CH (MgBr) ]. The heavier congeners [(PPh dNSiMe ) -
˚
2
2
2
3 2
2
3 2 2
10
˚
2
[Mg{N(SiMePh
bond lengths in 3 (2.433(1), 2.429(1) A) are within the range
of terminal Mg-S σ bond lengths (2.33-2.66 A), while they
are slightly shorter than bridging Mg-S bond lengths (2.46-
2 2 2
) }
t
CH (PPh dNSiMe ) ] with [{(C H -4-Bu )CH } Ca(THF) ]
[
and [(PhCH ) Ba], respectively.
˚
2
2
3 2
6
4
2 2
4
2
f,g
˚
2
2
Compounds 3 and 4 were isolated as highly moisture-
sensitive colorless crystalline solids which are soluble in Et O
and toluene. They have been characterized by NMR spectro-
11
˚
2
2.61 A). The P-C bonds are shortened and the P-N bonds
are lengthened in compounds 3 and 4 compared with those of 1
and 2.
1
scopy and X-ray crystallography. The H NMR spectrum of 3
displays resonances for the SiMe and phenyl protons. The
3
In order to understand the binding situation in 3 and 4,
compound 4 was investigated by means of quantum-chemi-
cal calculations. The molecule was fully optimized with the
13
1
C{ H} NMR spectrum of 3shows one doublet of doublets for
the carbenic carbon at δ 34.35 ppm (JP-C = 32.6, 33.5 Hz),
which is shifted upfield compared with that of [(PPh dNSi-
1
2
2
DFT-variant B3LYP as implemented in the Gaussian 03
2
f,g
1
program using the 6-31G(d) basis set. The calculated
3
14
Me ) CM] (M = Ca 44.9 ppm; M=Ba, 53.9 ppm). The
3
2
1
2
31
P{ H} NMR displays two doublets at δ 19.9 and 29.9 ppm
2
(
J
0
= 52.0, 26.0 Hz) due to two nonequivalent phosphorus
1
P-P
(9) Wei, P.; Stephan, D. W. Organometallics 2003, 22, 601.
(10) Bartlett, R. A.; Olmstead, M. M.; Power, P. P. Inorg. Chem.
13
nuclei. The C{ H} NMR spectrum of 4 displays one triplet at
6.87 ppm (J = 83.3 Hz) for the carbenic carbon, which is
1
994, 33, 4800.
11) Teng, W.; Englich, U.; Ruhlandt-Senge, K. Inorg. Chem. 2000,
3
comparable with that of 3. The P{ H} NMR spectrum of 4
P-C
(
31
1
3
9, 3875.
displays one signal at δ 18.6 ppm.
The molecular structures of 3 and 4 are shown in Figures
(12) (a) Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. B 1988, 37, 785.
(
1
(
b) Miehlich, B.; Savin, A.; Stoll, H.; Preuss, H. Chem. Phys. Lett. 1989,
57, 200. (c) Vosko, S. H.; Wilk, L.; Nusair, M. Can. J. Phys. 1980, 58, 1200.
d) Becke, A. D. J. Chem. Phys. 1993, 98, 5648.
13) Frisch, M. J. et al.; Gaussian 03, Revision D.01; Gaussian, Inc.,
˚
and 2, respectively. Selected bond distances (A) and angles
1
(
Wallingford, CT, 2004 (see the Supporting Information for a full citation).
(14) (a) Hehre, W. J.; Ditchfield, R.; Pople, J. A. J. Chem. Phys. 1972,
56, 2257. (b) Francl, M. M.; Petro, W. J.; Hehre, W. J.; Binkley, J. S.; Gordon,
M. S.; DeFrees, D. J.; Pople, J. A. J. Chem. Phys. 1982, 77, 3654.
(c) Rassolov, V. A.; Ratner, M. A.; Pople, J. A.; Redfern, P. C.; Curtiss,
L. A. J. Comput. Chem. 2001, 22, 976.
(
8) (a) Ziegler, K. Brit. Pat. GB 778619, 1957. (b) van de Heisteeg, B. J.
J.; Schat, G.; Akkerman, O. S.; Bickelhaupt, F. J. J. Organomet. Chem.
986, 308, 1. (c) Hogenbirk, M.; Schat, G.; Akkerman, O. S.; Bickelhaupt, F.;
1
Schottek, J.; Albrecht, M.; Fr €o hlich, R.; Kehr, G.; Erker, G.; Kooijman, H.;
Spek, A. L. Eur. J. Inorg. Chem. 2004, 1175.

Article
Organometallics, Vol. 29, No. 4, 2010 941
˚
Table 1. Selected Bond Distances (A) and Angles (deg) for Compounds 3-6
Compound 3
Mg(1)-C(1)
Mg(1)-N(1)
Mg(2)-C(1)
Mg(2)-S(1)
C(1)-P(1)
P(1)-N(1)
C(2)-P(3)
P(3)-N(2)
2.277(3)
2.036(3)
2.219(3)
2.433(1)
1.724(3)
1.611(3)
1.720(3)
1.619(3)
Mg(1)-C(2)
Mg(1)-N(2)
Mg(2)-C(2)
Mg(2)-S(2)
C(1)-P(2)
P(2)-S(1)
2.257(3)
2.033(3)
2.212(3)
2.429(1)
1.706(3)
2.045(1)
1.702(3)
2.038(1)
C(2)-P(4)
P(4)-S(2)
C(1)-Mg(1)-C(2)
C(2)-Mg(1)-N(2)
C(1)-Mg(2)-S(1)
Mg(1)-C(1)-Mg(2)
P(1)-C(1)-P(2)
100.4(1)
C(1)-Mg(1)-N(1)
C(1)-Mg(2)-C(2)
C(2)-Mg(2)-S(2)
Mg(1)-C(2)-Mg(2)
P(3)-C(2)-P(4)
75.2(1)
103.6(1)
81.4(8)
78.3(9)
130.4(2)
75.7(1)
81.7(8)
77.7(1)
129.0(2)
Compound 4
Mg(1)-C(1)
Mg(1)-N(1)
Mg(2)-C(1)
Mg(2)-N(2)
C(1)-P(1)
P(1)-N(1)
C(2)-P(3)
P(3)-N(3)
2.219(2)
Mg(1)-C(2)
Mg(1)-N(3)
Mg(2)-C(2)
Mg(2)-N(4)
C(1)-P(2)
P(2)-N(2)
C(2)-P(4)
P(4)-N(4)
2.229(2)
2.051(2)
2.242(2)
2.043(2)
1.706(2)
1.611(2)
1.705(2)
1.614(2)
2.046(2)
2.250(2)
2.045(2)
1.701(2)
1.624(2)
1.707(2)
1.618(2)
C(1)-Mg(1)-C(2)
C(2)-Mg(1)-N(3)
C(1)-Mg(2)-N(2)
Mg(1)-C(1)-Mg(2)
P(3)-C(2)-P(4)
100.6(8)
C(1)-Mg(1)-N(1)
C(1)-Mg(2)-C(2)
C(2)-Mg(2)-N(4)
Mg(1)-C(2)-Mg(2)
P(1)-C(1)-P(2)
76.2(8)
99.3(8)
75.7(8)
79.9(7)
131.5(1)
76.4(8)
76.0(8)
80.0(8)
132.3(1)
Compound 5
Mg(1)-N(1)
Mg(1)-O(1)
C(1)-P(1)
2.084(3)
Mg(1)-N(2)
Mg(1)-O(1A)
C(1)-P(2)
2.112(3)
1.951(2)
1.706(3)
1.598(3)
1.961(2)
1.731(3)
1.599(3)
P(1)-N(1)
P(2)-N(2)
N(1)-Mg(1)-N(2)
N(2)-Mg(1)-O(1)
Mg(1)-N(1)-P(1)
P(1)-C(1)-P(2)
101.3(1)
120.8(1)
105.6(1)
127.7(2)
103.8(1)
N(1)-Mg(1)-O(1)
Mg(1)-O(1)-Mg(1A)
N(1)-P(1)-C(1)
118.0(1)
98.6(1)
113.6(1)
110.8(1)
C(1)-P(2)-N(2)
P(2)-N(2)-Mg(1)
Compound 6
Al(1)-C(2)
Al(1)-N(1)
P(1)-C(2)
P(1)-N(1)
1.976(1)
1.915(1)
1.710(1)
1.634(1)
Al(1)-C(1)
Al(1)-S(1)
P(2A)-C(2)
P(2)-S(1)
1.949(1)
2.316(5)
1.686(1)
2.044(5)
C(2)-Al(1)-N(1)
C(2)-Al(1)-S(1)
P(1)-C(2)-P(2A)
C(2)-P(1)-N(1)
81.5(5)
111.3(4)
129.7(8)
98.8(6)
C(2)-Al(1)-C(1)
N(1)-Al(1)-S(1)
Al(1)-C(2)-P(1)
P(1)-N(1)-Al(1)
125.2(6)
99.6(4)
87.7(6)
92.0(5)
2
f
˚
structural parameters (Mg(1)-C(1)=2.251 A, Mg(1)-C
-1.665; P, þ1.706; C, -1.778). Therefore, it is suggested
that compounds 3 and 4 are bimetallic methanediide com-
plexes containing a strong Mg-C electrostatic bonding.
The reaction of 4 with water in toluene for 3 h gave 2, the
magnesium hydroxide complex [HC(PPh dNSiMe ) Mg-
˚
˚
(
2)=2.251 A, Mg(1)-N(1)=2.074 A, Mg(1)-N(3)=2.074
˚
˚
˚
A, C(1)-P(1) = 1.732 A, P(1)-N(1) = 1.647 A; Mg(1)-
C(1)-Mg(2)= 78.0°, C(1)-Mg(1)-C(2)= 103.1°) are in
good agreement with the crystallographic data. The cal-
culated charges of compound 4 by natural population
2
3 2
1
3
1
(μ-OH)]2 (5), and unreacted 4, confirmed by P{ H}
NMR spectroscopy (Scheme 2). When the reaction pro-
ceeded overnight, compound 2 and a trace amount of 5 were
afforded. An attempt to isolate pure compound 5 by recrys-
tallization failed. A mixture of compounds 2 and 5 was
1
5
analysis (NPA) show that the bonding between the
ligand and magnesium centers is highly ionic (Table 2).
The charge distributions on the ligand backbone are
consistent with the resonance structure A (Figure 3),
which is an extreme case. A similar calculation result is
found in [(PPh dNSiMe ) CCa] (NPA charges: N,
31
1
isolated as colorless crystalline solids in toluene. The P{ H}
NMR spectrum of the mixture shows one singlet for 5 at
2
3 2
2
1
δ 24.5 ppm. The resonances for 5 in the H NMR spectrum
of the mixture cannot be identified, due to the trace amount
of 5. Other examples of magnesium hydroxide complexes,
(
15) (a) Reed, A. E.; Weinstock, R. B.; Weinhold, F. J. Chem. Phys.
985, 83, 735. (b) Reed, A. E.; Curtis, L. A.; Weinhold, F. Chem. Rev. 1988,
1
88, 899.

9
42 Organometallics, Vol. 29, No. 4, 2010
Guo et al.
Scheme 2. Synthesis of 5
Table 2. Calculated Charges of Compounds 4 and 6A by Natural
Population Analysis (NPA)
atom
NPA charge
Compound 4
C(1)
Mg(1)
P(1)
-1.905
1.705
1.924
N(1)
Si(1)
-1.722
1.977
Compound 6A
Al(1)
C(2)
N(1)
P(1)
P(2)
S(1)
1.37
-1.712
-1.39
1.38
1.01
-0.52
Figure 4. Molecular structure of 5 with thermal ellipsoids at the
5
0% probability level.
2
f,g
cyclohexyl isocyanate at room temperature. However, there
was no reaction between compound 4 with adamantyl isocya-
0
nate, azobenzene, or N,N -di-tert-butylcarbodiimide in toluene at
room temperature.
Figure 3. Charge distributions on the ligand backbone A or B.
Synthesis and Characterization of Aluminum Bis(phos-
phoranyl)methanediide Complex. The reaction of 1 with a
stoichiometric amount of AlMe in refluxing toluene af-
Ar,Me
[
{Tp
}Mg(μ-OH)] (Tp = tris(pyrazolyl)hydroborate,
t 16
2
Ar = 4-Bu C H ), [{HC(CMeNAr) }Mg(μ-OH)(THF)]
2
Ar = 2,6-Pr C H ), and [Mg (OMes)(μ-OMes) (OH)-
2 6 3 2 2
6
4
2
3
i
17
(
forded the aluminum bis(phosphoranyl)methanediide com-
plex [{(PPh dNSiMe )(PPh dS)}CAlMe] (6) (Scheme 3).
(THF) ] 2THF (Mes=2,4,6-Me C H ), have been reported
and structurally characterized.
2
2
3
3
6
2
2
3
2
2
18
Cavell and his co-workers have reported that the reaction of
CH (PPh dNSiMe ) ] with 2 equiv of AlMe gave the
Compound 5 has been characterized by X-ray crystallo-
˚
graphy (Figure 4). Selected bond distances (A) and angles
deg) are given in Table 1. Compound 5 is a dimeric complex
with two hydroxide groups μ -bonded to the magnesium
centers. The ligand backbone adopts a twist-boat conforma-
tion with the Mg(1) atom displaced from the P(2)-N(2)-
[
2
2
3 2
3
bimetallic methanediide complex [(AlMe ) {μ -C(Ph PdNSi-
2
2
2
2
4
0
0
2h
Me ) -κ C,C ,N,N }] (7) (Scheme 4). A similar bimetallic
(
3
2
t
2
methanediide complex of aluminum, [(AlMe ) {C(PPh dNBu )-
2 2 2
(8-C H N)}], has been reported and structurally characterized.
The reaction of [CH (PPh dO) ] with excess AlMe afforded
19
9 6
2
2
2
3
˚
20
N(1)-P(1) least-squares plane by 1.171 A. The Mg(1) atom is
coordinated with two nitrogen atoms of the ligand and two
[
{AlMe}{C(PPh dO) } {AlMe } ] (8). To the best of our
2 2 2 2 2
knowledge, compound 6 is the first example of a methanediide
carbon bonded to one aluminum center.
Compound 6 was isolated as a highly air- and moisture-
oxygen atoms of the hydroxide. The Mg(1) atom displays a
˚
tetrahedral geometry. The Mg(1)-C(1) bond (2.889 A) is
significantly longer than that of [HC(PPh dNSiMe ) Mg-
˚
2
3 2
sensitive colorless crystalline solid which is soluble in Et O
2
and toluene. It has been characterized by NMR spectroscopy
1
and X-ray crystallography. The H NMR spectrum of 6
9
(
μ-Cl)] (2.460(8) A), showing that the negative charge is
2
delocalized throughout the ligand. The Mg-O bond lengths
Ar,Me
˚
1.951(2), 1.961(2) A) are comparable to those of [{Tp
(
}-
displays resonances for the SiMe and phenyl protons. It is
3
1
6
˚
13
1
noteworthy that the C{ H} NMR signal for the carbenic
Mg(μ-OH)] (1.955(5), 1.951(6) A).
2
13
1
carbon in 6 is not observed. Similarly, there is no C{ H}
Harder and co-workers have reported that [(PPh dNSiMe ) -
2
3 2
2
h
31
1
CM]2 (M = Ca, Ba) underwent [2 þ 2] cycloaddition with
NMR resonance for the carbenic carbon in 7. The P{ H}
NMR spectrum of 6 displays two doublets at δ 22.8 and 25.9
(16) Ghosh, P.; Parkin, G. Inorg. Chem. 1996, 35, 1429.
(
17) S ꢀa nchez-Barba, L. F.; Hughes, D. L.; Humphrey, S. M.;
Bochmann, M. Organometallics 2006, 25, 1012.
18) Teng, W.; Guino-o, M.; Hitzbleck, J.; Englich, U.; Ruhlandt-
Senge, K. Inorg. Chem. 2006, 45, 9531.
(19) Wang, Z.-X.; Li, Y.-X. Organometallics 2003, 22, 4900.
(20) Robinson, G. H.; Lee, B.; Pennington, W. T.; Sangokoya, S. A.
J. Am. Chem. Soc. 1988, 110, 6260.
(

Article
Organometallics, Vol. 29, No. 4, 2010 943
Scheme 3. Synthesis of 6
Scheme 4. Aluminum Bis(phosphoranyl)methanediide Com-
plexes 7 and 8
Figure 5. Molecular structure of 6 with thermal ellipsoids at the
5
0% probability level.
agreement with the crystallographic data. Each “{(PH d
2
NH)(PH dS)}CAl” moiety in compound 6A is almost located
2
2
ppm ( J
0
= 13.0 Hz) due to two nonequivalent phos-
P-P
at the same plane, which is slightly different from the X-ray
2
7
2
5
phorus nuclei. The Al NMR spectrum shows one broad
signal at δ 54.6 ppm.
The molecular structure of 6 is shown in Figure 5. Selected
bond distances (A) and angles (deg) are given in Table 1. It
is symmetric and is comprised of two “{(PPh dNSiMe )-
structure of 6. The natural bond orbital (NBO) analysis (Table
S1; see the Supporting Information) shows that the aluminum
3
atom adopts a sp d hybridization. The Al(1)-C(2) σ bond is
˚
2.25 0.03
1.66
formed by sp
d
hybrids on the aluminum atom and sp
2
3
hybrids on the carbon atom. The Al(1)-C(2) π bond is formed
0.06 3.00 1.19
(PPh =S)}CAlMe” moieties bonded together in a head-to-
2
by s
orbital on the carbon atom. The electron density of the Al-
1)-C(2) σ and π bonds are mostly contributed by the C(2)
p
d
hybrids on the aluminum atom and the p
head manner. The aluminum atom Al(1) is bonded to the
methanediide carbon atom C(2), one nitrogen, and one
sulfur atom of each ligand. Therefore, the geometry around
the aluminum atom is tetrahedral. The Al(1)-C(2) bond
(
atom (85.7% electron density of the σ bond and 98.2% electron
density of the π bond). Therefore, the NBO bond order by the
natural resonance theory (NRT) analysis shows that the
2
h
˚
˚
26
(1.976(1) A) is shorter than that of 7 (2.121(3), 2.117(3) A).
Similar to the case for 7, the Al(1)-C(2) bond in 6 is longer
than the terminal Al-C
Al(1)-C(2) bond is highly polar (16.2% covalent character,
83.8% ionic character). Moreover, the Natural Hybrid Orbitals
˚
bond (1.949(1) A). The Al-
methyl
˚
(
1)-N(1) bond (1.915(1) A) is shorter than those of 7
(NHOs) on the aluminum and carbon atoms for forming the
2h
˚
(
1.926(3), 1.933(3) A), but it is longer than the Al-N
amide
Al(1)-C(2) σ bond deviate at angles of 9.0 and 19.7° from the
bond axis, respectively. The hybrids on the aluminum and
carbon atoms for forming the Al(1)-C(2) π bond deviate at
angles of 60.3 and 32.2° from the bond axis, respectively. These
result in weak covalent bonding between the Al(1) and C(2)
i
σ bond in the aluminum amide complexes [(2,6-Pr C H )N-
2
6
3
21
˚
SiMe )AlMe ] (average 1.821 A) and [(Me Si)N{CH CH -
3 2 2 3 2 2
Me Si)N} AlCl] (average 1.807 A). The Al(1)-S(1) bond
2.316(5) A) in 6 is longer than the Al-S σ bond in
(
(
(
22
˚
3
2
˚
t
23
˚
(Bu ) Al(SCH CH NEt )] (2.272(4) A). Similar to the case
2 2 2 2
27
[
atoms. The Wiberg bond index (WBI) indicates that the
Al(1)-C(2) bond (WBI order 0.474) has weak covalent bind-
ing. The calculated charges of compound 6A by natural popula-
for compounds 3 and 4, the P-C bonds are shortened and the
P-N/P-S bonds are lengthened in 6 compared with those of 1.
In order to understand the binding situation in 6, the
1
5
tion analysis (NPA) also show that the bonding between the
ligand and aluminum center is highly ionic (Table 2). The WBI
bond orders of the P-C (1.117, 1.121), P-N (0.985), and P-S
bonds (1.078) in 6A show that the charge distributions on the
ligand backbone are consistent with the resonance structure B
with little or no π-electron delocalization (Figure 3). Thus, it is
suggested that compound 6 is an aluminum methanedi-
ide complex. Weak metal-Cmethanediide bonding is also found
simple derivative [{(PH dNH)(PH dS)}CAlH] (6A) (Figure
2
2
2
S1; see the Supporting Information) is applied as a model for the
theoretical calculation of compound 6. The molecule was
first fully optimized by the density functional theory (DFT)
1
2
24
B3LYP functional with 6-311þG(d,p) basis set using the
13
Gaussian 03 program. The calculated structural parameters
˚
˚
(
2
(
Al(1)-C(2) = 2.000 A, Al(1)-N(1) = 1.920 A, Al(1)-S(1) =
˚
˚
˚
.348 A, P(1)-C(2) = 1.705 A, P(2A)-C(2) = 1.689 A, P-
˚
2A)-S(1A)=2.064 A;C(2)-Al(1)-N(1) = 79.4°) are in good
(
25) Glendening, E. D.; Badenhoop, J. K.; Reed, A. E.; Carpenter, J. E.;
Bohmann, J. A.; Morales, C. M.; Weinhold, F. Natural Bond Orbital
Analysis Program; Theoretical Chemistry Institute, University of Wisconsin,
Madison, WI, 2001.
(26) (a) Glendening, E. D.; Weinhold, F. J. Comput. Chem. 1998, 19,
593. (b) Glendening, E. D.; Weinhold, F. J. Comput. Chem. 1998, 19, 610.
(c) Glendening, E. D.; Badenhoop, J. K.; Weinhold, F. J. Comput. Chem.
1998, 19, 628.
(27) Wiberg, K. B. Tetrahedron 1968, 24, 1083.
(28) Cantat, T.; Demange, M.; M ꢀe zailles, N.; Ricard, L.; Jean, Y.; Le
Floch, P. Organometallics 2005, 24, 4838.
(
21) Waezsada, S. D.; Liu, F.-Q.; Murphy, E. F.; Roesky, H. W.;
Teichert, M.; U ꢀs on, I.; Schmidt, H.-G.; Albers, T.; Parisini, E.;
Noltemeyer, M. Organometallics 1997, 16, 1260.
(
22) Emig, N.; Nguyen, H.; Krautscheid, H.; R ꢀe au, R.; Cazaux, J.-B.;
Bertrand, G. Organometallics 1998, 17, 3599.
23) McMahon, C. N.; Francis, J. A.; Bott, S. G.; Barron, A. R.
J. Chem. Soc., Dalton Trans. 1999, 67.
24) (a) Krishnan, R.; Binkley, J. S.; Seeger, R.; Pople, J. A. J. Chem.
Phys. 1980, 72, 650. (b) McLean, A. D.; Chandler, G. S. J. Chem. Phys.
980, 72, 5639.
(
(
(29) Cantat, T.; Ricard, L.; M ꢀe zailles, N.; Le Floch, P. Organome-
tallics 2006, 25, 6030.
1

9
44 Organometallics, Vol. 29, No. 4, 2010
Guo et al.
1
3
1
Table 3. Theoretical Topological Features at the BCP of 6,
a
Ph). C{ H} NMR (100.4 MHz): δ 3.52 (SiMe
3
), 34.35 (dd,
[
H C-Al(CH )-SH], and [H CdAl(CH )]
PCP, JP-C = 32.6, 33.5 Hz), 129.68-130.70 (m), 131.92-133.12
3
3
2
3
(
m), 137.12, 138.24, 138.68, 138.80, 139.41-140.13 (m), 140.60,
2
bond
F
r F
G
H
|V|
31
1
1
41.37 ppm (Ph). P{ H} NMR (161.7 MHz): δ 19.9 (d,
2
2
J
P-P
0
= 52.0 Hz), 29.9 ppm (d, JP-P = 26.0 Hz).
0
n
Compound 6
[
2 3 2 2 2
(PPh dNSiMe ) CMg] (4). Mg(Bu ) (2.20 mL, 1.0 M in
heptane, 2.20 mmol) was added to a solution of 2(1.18 g, 2.11 mmol)
in toluene (20 mL) at room temperature. The reaction mixture was
refluxed at 140 °C for 15 h. The resulting yellow solution was filtered
and concentrated in vacuo to yield colorless crystals of 4. Yield: 0.55
Al(1)-C(2)
Al(1)-C(1)
Al(1)-S(1)
Al(1)-N(1)
C(2)-P(1)
C(2)-P(2A)
P(1)-N(1)
P(2)-S(2)
0.47
0.55
0.33
0.44
1.22
1.25
1.21
0.95
7.08
7.58
3.09
8.86
0.72
2.17
12.64
-5.45
0.59
0.67
0.30
0.64
1.28
1.39
1.87
0.24
-0.10
-0.14
-0.08
-0.02
-1.23
-1.24
-0.99
-0.62
0.69
0.80
0.38
0.66
2.51
2.64
2.86
0.85
g (44.9%). Mp: 329 °C dec. Anal. Found: C, 63.83; H, 6.31; N, 4.55.
1
: C, 64.12; H, 6.60; N, 4.83. H NMR
Calcd for C62
H
76Mg
2
N
4
P
4
Si
4
(
7
399.5 MHz): δ 0.30 (s, 36 H, SiMe
3
), 6.92-6.96 (m, 8H, Ph),
.01-7.04 (m, 4H, Ph), 7.12-7.26 (m, 12H, Ph), 7.51-7.56 (m, 8H,
13
1
Ph), 7.66-7.71 ppm (m, 8H, Ph). C{ H} NMR (100.4 MHz): δ
.09 (SiMe ), 36.87 (t, PCP, JP-C = 83.3 Hz), 129.68, 129.91,
30.22, 131.88, 131.93, 132.71, 132.76, 132.81, 138.41, 138.56,
[
H
3
C-Al(CH
3
)-SH]
4
1
3
Al-C
0.55
7.66
0.67
-0.14
0.81
31
1
1
39.37, 139.50, 140.33, 140.46, 141.37, 141.50 ppm (Ph). P{ H}
NMR (161.7 MHz): δ 18.6 ppm.
HC(PPh dNSiMe Mg(μ-OH)]
[
H
2
CdAl(CH
3
)]
Al-C
AldC
0.55
0.66
7.37
11.98
0.66
1.01
-0.14
-0.17
0.80
1.17
[
2
3
)
2
2 2
(5). H O (24.0 mL, 0.03%
weight in toluene, 0.40 mmol) was added to 4 (0.23 g, 0.20 mmol)
at room temperature and the mixture stirred overnight. The
insoluble precipitate was filtered off, and the colorless filtrate
was concentrated to yield 2 and a trace amount of colorless
a
-3
2
-5
-3
˚
˚
˚
Units: F, e A ; r F, e A ; H, G, |V|, hartree A
.
in the metal bis(thiophosphoranyl)methanediide complexes
6
(PPh dS) CdPd(PPh )], [(PPh dS) CdRu(PPh ) ], and
28
31
1
[
[
crystals of 5. P{ H} NMR (161.7 MHz) for 5: δ 24.5 ppm. The
2
2
3
2
2
3 2
2
9
1 13
(PPh dS) CdZrCp ].
2
resonances for 5 in the H and C NMR spectra of the mixture
cannot be identified, due to trace amounts of 5.
2
2
The topological analysis of the electron densities of com-
pound 6 according to Bader’s quantum theory of atoms in
2 3 2 2 3
[(PPh dNSiMe )(PPh dS)CAlMe] (6). AlMe (0.72 mL, 2.0
3
molecules (QTAIM) was performed (Table 3). The Lapla-
0
M in toluene, 1.44 mmol) was added to a solution of 1 (0.53 g, 1.05
mmol) in toluene (20 mL) at room temperature. The reaction mixture
was refluxed at 140 °C for 15 h. Volatiles were removed under reduced
2
cian of electron density r F and the total energy density H at
the (3,-1) bond critical point (BCP) show that the Al(1)-
C(2) bond in 6 is polar and covalent. The bond nature of the
Al(1)-C(2) bond in 6 is very similar to that of Al-C bonds in
pressure, and the residue was extracted with Et O. After filtration and
2
concentration of the filtrate, 6 was obtained as colorless crystals.
Yield: 0.12 g (21.0%). Mp: 266 °C. Anal. Found: C, 63.82; H, 5.67; N,
1
2.35. Calcd for C H N Al P S Si : C, 64.07; H, 5.94; N, 2.58. H
[
H C-Al(CH )-SH] and [H CdAl-CH ].
3
3
2
3
58
64
2
2 4 2 2
NMR (395.9 MHz): δ 0.057 (s, 18H, SiMe ), 0.17 (s, 6H, AlMe),
3
Experimental Section
6.65-6.70 (m, 8H, Ph), 6.78-6.79 (m, 4H, Ph), 7.15-7.17 (m, 8H,
Ph), 7.40-7.43 (m, 12H, Ph), 7.88-7.94 (m, 4H, Ph), 8.19-8.22 ppm
1
3
1
(m, 4H, Ph). C{ H} NMR (100.5 MHz): 2.87 (SiMe ), 2.90
General Procedures. All manipulations were carried out under
3
an inert atmosphere of dinitrogen gas using standard Schlenk
techniques. Solvents were dried over and distilled over Na/K
alloy prior to use. 1 and 2 were prepared as described in the
(AlMe), 129.39, 130.22, 130.74, 130.80, 131.19, 131.29, 131.62,
131.73, 132.83, 133.54, 133.66, 137.24, 137.47, 138.09, 138.34,
31
1
138.71, 139.54 ppm (Ph). P{ H} NMR (160.3 MHz): δ 22.8,
7,32
1
13
31
27
2
25.9 ppm (d, J
54.6 ppm.
27
1
literature.
recorded on a JEOL ECA 400 spectrometer. The NMR spectra
were recorded in C . The chemical shifts δ are relative to
The H, C, P, and Al NMR spectra were
P-P
= 13.0 Hz). Al{ H} NMR (104.1 MHz) δ
0
6
D
6
X-ray Data Collection and Structural Refinement. Intensity
data for compounds 3-6 were collected using a Bruker APEX II
diffractometer. The crystals of 3-5 were measured at 173(2) K,
and that of 6 was measured at 103(2) K. The structures were
solved by direct phase determination (SHELXS-97) and refined
1
13
31
SiMe for H and C, 85% H PO for P, and 0.5 M AlCl3/
4
3
4
27
MeOH for Al. Elemental analyses were performed by the
Division of Chemistry and Biological Chemistry, Nanyang
Technological University. Melting points were measured in
2
31
sealed glass tubes and were not corrected.
for all data by full-matrix least-squares methods on F . All
non-hydrogen atoms were subjected to anisotropic refinement.
The hydrogen atoms were generated geometrically and allowed
to ride in their respective parent atoms; they were assigned
appropriate isotopic thermal parameters and included in the
structure-factor calculations. A summary of X-ray data is given
in Table S2 (see the Supporting Information).
n
(3). Mg(Bu )
[
.0 M in heptane, 1.20 mmol) was added to a solution of 1 (0.50
(PPh
2
dNSiMe
3
)(PPh
2
dS)CMg]
2
2
(1.20 mL,
1
g, 0.99 mmol) in toluene (20 mL) at room temperature. The
reaction mixture was refluxed at 140 °C for 15 h. The resulting
yellow solution was filtered and concentrated in vacuo to yield
colorless crystals of 3. Yield: 0.34 g (65.4%). Mp: 234.3 °C.
Anal. Found: C, 63.47; H, 5.34; N, 2.28. Calcd for C H -
5
6
58
1
Acknowledgment. This work was supported by the
Academic Research Fund Tier 1 (No. RG 47/08, C.-W.
S.; No. RG 28/07, K.H.L.) and by a Strategic Research
Grant from the City University of Hong Kong (Project
No. 7002285, K.-C.L.).
N
2
Mg
MHz): δ -0.15 (s, 18 H, SiMe
.97-7.14 (m, 13H, Ph), 7.18-7.43 (m, 5H, Ph), 7.57-7.74
m, 8H, Ph), 7.92-7.98 (m, 2H, Ph), 8.13-8.19 ppm (m, 4H,
2
P
4
2
S Si
2
: C, 63.99; H, 5.57; N, 2.67. H NMR (399.5
3
), 6.68-6.95 (m, 8H, Ph),
6
(
(
30) Bader, R. F. W. Atoms in Molecules-A Quantum Theory; Oxford
University Press: New York, 1990.
31) Sheldrick, G. M. SHELXL-97; Universit €a t G €o ttingen, G €o ttingen,
Germany, 1997.
32) Appel, R.; Ruppert, I. Z. Anorg. Allg. Chem. 1974, 406, 131.
Supporting Information Available: Figures and tables giving
selected calculation results of 4 and 6A and CIF files giving
X-ray data for 3-6. This material is available free of charge via
the Internet at http://pubs.acs.org.
(
(