Reactivity of a tin(II) (iminophosphinoyl)(thiophosphinoyl)methanediide complex toward isocyanates and rhodium(I) chloride

Article abstract of DOI:10.1021/om300062n

The reaction of the tin(II) (iminophosphinoyl)(thiophosphinoyl)methanediide [(PPh₂=NSiMe₃)(PPh₂=S)CSn:]₂ (1) with AdNCO (Ad = adamantyl), ArNCO (Ar = 2,6-Prⁱ₂C ₆H₃), and [RhCl(cod)]₂ in THF afforded [(PPh₂=NSiMe₃)(PPh₂=S)C{C(O)N(Ad)}Sn:] (2), [(PPh₂=NSiMe₃)(PPh₂=S)C{C(O)N(Ar)}Sn ⁺:] (3), and [(PPh₂=NSiMe₃)(PPh ₂=S)C{Rh(cod)}(SnCl)] (4), respectively. Compounds 2-4 have been characterized by NMR spectroscopy and X-ray crystallography.

Full text of DOI:10.1021/om300062n

Article
pubs.acs.org/Organometallics
Reactivity of a Tin(II)
(Iminophosphinoyl)(thiophosphinoyl)methanediide Complex toward
Isocyanates and Rhodium(I) Chloride
Jia-Yi Guo, Yongxin Li, Rakesh Ganguly, and Cheuk-Wai So*
Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University,
637371 Singapore
S
* Supporting Information
ABSTRACT: The reaction of the tin(II) (iminophosphinoyl)(thiophosphinoyl)methanediide [(PPh2NSiMe3)(PPh2
S)CSn:]2 (1) with AdNCO (Ad = adamantyl), ArNCO (Ar = 2,6-Pri2C6H3), and [RhCl(cod)]2 in THF afforded [(PPh2
NSiMe3)(PPh2S)C{C(O)N(Ad)}Sn:] (2), [(PPh2NSiMe3)(PPh2S)C¯{C(O)N(Ar)}Sn+:] (3), and [(PPh2NSiMe3)-
(PPh2S)C{Rh(cod)}(SnCl)] (4), respectively. Compounds 2−4 have been characterized by NMR spectroscopy and X-ray
crystallography.
table silenes (>SiC<),1 germenes (>GeC<),2 and
the π bond). In valence bond terms, the C−Sn bond in 1 can
3
be between the resonance forms A and B (Scheme 1).
Sstannenes (>SnC<) have attracted much attention in
the past 30 years and have been the focus of several reviews.4
Scheme 1. Resonance Forms A and B
They have been synthesized successfully by incorporating
sterically hindered substituents at both carbon and heavier
group 14 elements. They are reactive and can undergo 1,2-
addition and [2 +n] cycloaddition.5 In contrast, stable heavier
group 14 vinylidene analogues (:MC<) are scarcely known.
Because they lack bulky substituents at the low-coordinate
metal(II) centers, the MC bonds are highly reactive and
undergo oligomerization more readily. Until now, only two
examples of heavier group 14 vinylidene analogues have been
reported.6,8 Leung et al. reported the first example of the
bisgermavinylidene [(Me3SiNPPh2)2CGe→GeC-
(PPh2NSiMe3)2], which contains a weak Ge−Ge inter-
action.6 The existence of the monomeric germavinylidene
intermediate “(Me3SiNPPh2)2CGe:” in solution has been
demonstrated by trapping reactions of the bisgermavinylidene
with various transition-metal complexes and organic and
inorganic substrates.7 We reported the synthesis of the tin(II)
(iminophosphinoyl)(thiophosphinoyl)methanediide [(PPh2
NSiMe3)(PPh2S)CSn:]2 (1), which can be considered as a
stannavinylidene derivative.8 The X-ray structure of 1 implies
that the Sn−C bond has some double-bond character. Natural
bond orbital (NBO) analysis suggests the existence of a >C
Sn: skeleton in which the electron densities of the σ and π
bonds are mostly occupied by the Cmethanediide atom (85.3%
electron density of the σ bond and 96.9% electron density of
Recently, the [2 + 2] cycloadditions of main-group and
transition-metal bis(phosphinoyl)methanediide complexes with
AdNCO have been reported to show multiple-bond character
in the Cmethanediide−M bonds (M = Ca, Ba, Ge, Zr, Hf).9
Moreover, the 1,2-addition of [(Me3SiNPPh2)2CGe→
GeC(PPh2NSiMe3)2] with [RhCl(cod)]2 (cod = 1,5-
cyclooctadiene) demonstrates the existence of a Cmethanediide
−
Ge double bond and the nucleophilic character of the
Cmethanediide atom.7b In this context, it is highly desirable to
explore the reactivity of 1 toward isocyanates and [RhCl(cod)]2
to understand the bonding nature of the Cmethanediide−Sn bond
and the electronic properties of the Cmethanediide atom,
respectively.
Received: January 26, 2012
Published: May 8, 2012
© 2012 American Chemical Society
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Scheme 2. Synthesis of 2−4
due to coupling to 117/119Sn at δ 22.29 (2JP−P′ = 17.3 Hz, 2JSn−P
RESULTS AND DISCUSSION
■
2
= 86.7, 121.4 Hz) and 41.23 ppm (2JP−P′ = 13.0 Hz, JSn−P
=
The reaction of compound 1 with 2 equiv of AdNCO (Ad =
adamantyl) in THF afforded [(PPh2NSiMe3)(PPh2S)
47.7, 73.7 Hz). The 119Sn{1H} NMR spectrum of 2 consists of
a broad signal at δ −255.15 ppm, which shows an upfield shift
in comparison with that of 1 (δ 132.1 ppm). The 31P{1H}
NMR spectrum of 3 shows two doublets with satellites due to
C{C(O)N(Ad)}Sn:] (2, Scheme 2). It is noteworthy that the
lone pair electrons at the tin(II) atom do not undergo [1 + 2]
cycloaddition. Recently, the [2 + 2] cycloadditions of main-
group and transition-metal bis(phosphinoyl)methanediide
complexes with AdNCO have been reported by several
research groups.9 For example, the germanium(II),7d zirco-
nium, and hafnium bis(phosphinoyl)methanediide complexes
underwent a [2 + 2] cycloaddition with the CN bond of
AdNCO,9a whereas the calcium and barium bis(phosphinoyl)-
methanediide complexes underwent a [2 + 2] cycloaddition
with the CO bond of AdNCO.9b,c The results suggest that
the reaction of 1 with AdNCO probably proceeds via a [2 + 2]
cycloaddition of the >CSn: bond or an insertion reaction of
the C−−Sn+ bond with the NC bond of AdNCO. Moreover,
the reaction of 1 with 2 equiv of ArNCO (Ar = 2,6-Pri2C6H3)
in THF afforded [(PPh2NSiMe3)(PPh2S)C¯{C(O)N-
(Ar)}Sn+:] (3). It is proposed that the reaction proceeds via
a [2 + 2] cycloaddition or an insertion reaction to form an
intermediate which contains a four-membered CSnNC ring.
Due to the steric hindrance of the Ar group, the Cmethanide−Sn
bond in the intermediate is cleaved in order to release the ring
strain. The thiophosphinoyl substituent is then coordinated
with the tin atom to form 3. The results imply that the
Cmethanide−Sn bond in the intermediate is polar. However, the
reactions of 1 with 2 equiv of PhNNPh, PhCCPh, ButN
CNBut, Me3SiCHN2, ButCN or 1,4-naphthoquinone under
various conditions did not afford any cycloaddition product.
The 31P NMR spectra of the reaction mixtures show a mixture
of [CH2(PPh2NSiMe3)(PPh2S)] and unreacted 1 only.
The results indicate that compound 1 is decomposed during
the reactions.
2
coupling to 117/119Sn at δ 27.79 (2JP−P′ = 8.7 Hz, JSn−P = 69.4,
2
86.7 Hz) and 37.44 ppm (2JP−P′ = 8.7 Hz, JSn−P = 73.7, 134.4
Hz). The 119Sn{1H} NMR spectrum of 3 consists of a broad
signal at δ −129.25 ppm, which shows a downfield shift
compared with that of 2. The 13C NMR signal for the Cmethanide
atom and the 119Sn NMR signal indicate the presence of
zwitterionic C−···Sn+ character in compound 3.
The molecular structure of compound 2 is shown in Figure 1.
Compound 2 has an open book structure with the C(2)−Sn(1)
bond lying on the spine. The dihedral angle between the
C(2)P(2)N(2)Sn(1) and C(2)C(1)N(1)Sn(1) planes is 76.2°.
The iminophosphinoyl substituent is coordinated with the
Sn(1) atom, which adopts a distorted-trigonal-pyramidal
geometry (sum of bond angles 224.4°). This indicates that
the Sn(1) atom possesses a high-s-character lone pair. The
C(2)−Sn(1) bond (2.373(4) Å) is significantly longer than the
CSn: bond (2.199(4) Å) in 1.8 It is similar to that in
[HC(PPh2NSiMe3)(PPh2S)SnN(SiMe3)2] (2.384(4) Å).8
The results suggest that the C−Sn bond in 2 has no multiple-
bond character. Moreover, the C(1)−N(1) (1.372(13) Å) and
C(1)−O(1) bonds (1.233(4) Å) in 2 are single and double
bonds, respectively.
The molecular structure of compound 3 is shown in Figure 2.
Compound 3 has a propeller structure, in which the N and S
donors adopt a tripodal rearrangement. Both the iminophos-
phinoyl and thiophosphinoyl substituents are coordinated with
the Sn(1) atom, which adopts a distorted-trigonal-pyramidal
geometry (sum of bond angles 282.2°). This indicates that the
Sn(1) atom possesses a high-s-character lone pair. The
C(25)···Sn(1) distance (3.211(1) Å) is significantly longer
than the C−Sn bond in base-stabilized stannylenes such as
[{C5H4N-2-C(SiMe3)2}Sn{N(SiMe3)2}] (2.356(8) Å)10 and
[{2,6-(CH2NMe2)2C6H3}SnCl] (2.158(8) Å),11 but it is
shorter than the sum of van der Waals radii (ca. 3.87 Å).
The results suggest that there is a weak interaction between the
Cmethanide and Sn(1) atoms. The Sn(1)−S(1) bond (2.6418(4)
Å) is longer than the terminal Sn−S σ bond in [:Sn(SAr′)2]
(Ar′ = C6H2-2,4,6-But3) (2.435(1) Å),12 but it is comparable
with that of the aryltin(II) dithiocarboxylate [:Sn(Ar′)-
{S2CAr′}] (average 2.659 Å).13 The Sn(1)−N(1)
Compounds 2 and 3 were isolated as colorless crystalline
solids, which are stable at room temperature in solution and the
solid state under an inert atmosphere. They are soluble in Et2O,
toluene, and THF. They have been characterized by NMR
1
spectroscopy and X-ray crystallography. The H NMR spectra
of 2 and 3 show a set of signals due to the ligand backbone.
The 13C{1H} NMR spectrum of 2 shows one doublet of
doublets for the Cmethanide atom at δ 56.70 ppm (JP−C = 56.6 Hz,
JP′−C = 70.0 Hz), which shows a downfield shift compared with
that of 3 (δ 40.64 ppm (JP−C = 56.6 Hz, JP′−C = 74.3 Hz)). The
31P{1H} NMR spectrum of 2 shows two doublets with satellites
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Figure 1. Molecular structure of 2 with thermal ellipsoids at the 50%
probability level. The disordered phenyl substituent at the P(2) atom,
the NSiMe3 substituent, the NAd substituent, and the Sn(1A) atom
are omitted for clarity. Selected bond lengths (Å) and angles (deg):
Sn(1)−N(1) = 2.146(8), Sn(1)−N(2) = 2.235(8), Sn(1)−C(2) =
2.373(4), C(1)−C(2) = 1.550(5), C(1)−O(1) = 1.233(4), C(1)−
N(1) = 1.372(13), C(2)−P(1) = 1.783(4), C(2)−P(2) = 1.785(4),
P(2)−N(2) = 1.628(11), P(1)−S(1) = 1.9599(15); C(2)−Sn(1)−
N(1) = 64.1(3), C(2)−Sn(1)−N(2) = 71.5(3), N(1)−Sn(1)−N(2) =
88.8(4), Sn(1)−N(2)−P(2) = 94.4(4), N(2)−P(2)−C(2) = 104.2(3),
P(2)−C(2)−Sn(1) = 85.89(16), Sn(1)−C(2)−C(1) = 85.1(2),
C(2)−C(1)−N(1) = 110.8(4), C(1)−N(1)−Sn(1) = 99.0(5),
P(1)−C(2)−P(2) = 123.7(2).
Figure 2. Molecular structure of 3 with thermal ellipsoids at the 50%
probability level. Selected bond lengths (Å) and angles (deg): Sn(1)−
S(1) = 2.6418(4), Sn(1)−N(2) = 2.1913(12), Sn(1)−N(1) =
2.1477(12), N(1)−C(26) = 1.3649(18), C(26)−O(1) = 1.2279(17),
C(25)−C(26) = 1.524(2), C(25)−P(1) = 1.7244(15), C(25)−P(2) =
1.7367(15), P(1)−S(1) = 2.0545(5), P(2)−N(2) = 1.6329(12);
S(1)−Sn(1)−N(1) = 96.50(4), S(1)−Sn(1)−N(2) = 94.02(4),
N(1)−Sn(1)−N(2) = 91.69(5), Sn(1)−N(1)−C(26) = 123.58(10),
N(1)−C(26)−C(25) = 114.36(12), C(26)−C(25)−P(1) =
112.77(10), C(26)−C(25)−P(2) = 113.31(10), P(1)−C(25)−P(2)
= 119.22(8), C(25)−P(1)−S(1) = 113.78(5), P(1)−S(1)−Sn(1) =
95.755(18), C(25)−P(2)−N(2) = 114.10(7), P(2)−N(2)−Sn(1) =
112.14(7).
(2.1477(12) Å) and Sn(1)−N(2) (2.1913(12) Å) bonds in 3
are comparable to those in 2. Moreover, the C(26)−N(1)
(1.3649(18) Å) and C(26)−O(1) bonds (1.2279(17) Å) are
single and double bonds, respectively.
nonequivalent phosphorus nuclei. The 119Sn{1H} NMR
spectrum shows a multiplet at δ 110.74 ppm. The results
indicate that compound 4 retains its solid-state structure in
solution.
The reaction of compound 1 with 1 equiv of [RhCl(cod)]2 in
THF afforded [(PPh2NSiMe3)(PPh2S)C{Rh(cod)}-
(SnCl)] (4), in which RhCl(cod) underwent a 1,2-addition
with the >CSn: bond in 1. The addition also illustrates the
nucleophilic character of the Cmethanediide atom in 1. The tin(II)
atom in 1 did not act as a Lewis base or undergo an insertion
reaction toward RhCl(cod).14 The results are comparable with
the 1,2-addition of [RhCl(cod)]2 with the bisgermavinylidene
to form [(PPh2NSiMe3)2C{Rh(cod)}(GeCl)].7b Compound
4 is a heterobimetallic methanediide complex. Other examples
of heterobimetallic methanediide complexes such as [(PPh2
NSiMe3)2C(M){Rh(cod)}] (M = Li, Pd(allyl)) and
[{(C6H4N-2)(PPri2NSiMe3)C}2(Sn)(Pb)] have been re-
ported.15
The molecular structure of compound 4 is shown in Figure 3.
The C(1) atom is bonded to the Rh(1) and Sn(1) atoms.
Moreover, it is spirocyclic, with the thiophosphinoyl substituent
coordinated to the Rh(1) atom and the iminophosphinoyl
substituent coordinated to the Sn(1) atom. This indicates that
the C(1) atom is chiral. However, compound 4 is racemic, and
the R and S enantiomers are present in the unit cell. This is
because compound 4 was prepared from optically inactive
reactants. The C(1)−Sn(1) bond (2.3617(16) Å) is com-
parable with that in 2. The results indicate that the C−Sn bond
in compound 4 does not have any multiple-bond character. The
Sn(1) atom adopts a distorted-trigonal-pyramidal geometry
(sum of bond angles 265.38°), which indicates that the Sn(1)
atom possesses a high-s-character lone pair. The Sn(1)···Rh(1)
distance (2.8155(2) Å) is significantly longer than the Sn−Rh
bonds in the rhodium−stannylene complex cis-[Rh{Sn-
(NBut)2SiMe2}2(PPh3)2Cl] (2.571(2), 2.577(2) Å) and
[Rh(η-C6H5Me)(η-C8H14){SnCl(NR2)2}] (R = SiMe3,
2.554(1) Å).14a,b However, it is shorter than the sum of van
der Waals radii (ca. 4.0 Å). The results show that there is a
weak interaction between the Sn(1) and Rh(1) atoms. The
Rh(1)−C(1) bond (2.1715(16) Å) is comparable with the
Rh−Cmethanediide bonds in [(PPh2NSiMe3)2C{Rh(cod)}-
Compound 4 was isolated as a red crystalline solid, which is
stable at room temperature in solution and the solid state under
an inert atmosphere. It is soluble in THF and CH2Cl2. It has
been characterized by NMR spectroscopy and X-ray crystallog-
1
raphy. The H NMR spectrum of 4 shows a set of signals due
to the SiMe3, cod and phenyl protons. Similar to the case for
compound 1, a 13C{1H} NMR signal for the Cmethanediide atom is
not observed. The 31P{1H} NMR spectrum shows a doublet at
δ 28.36 ppm (2JP−P′ = 26.0 Hz) and a doublet of doublets at δ
2
37.86 ppm (2JP−P′ = 26.0 Hz, JP−Rh = 13.0 Hz) due to two
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dried over and distilled over CaH2 prior to use. 1 was prepared as
described in the literature.8 AdNCO (Ad = admantyl), ArNCO (Ar =
2,6-Pri2C6H1 3), and [RhCl(cod)]2 were purchased from Sigma-Aldrich
Co. The H, 13C, 31P, and 119Sn NMR spectra were recorded on a
JEOL ECA 400 spectrometer. The chemical shifts δ are relative to
1
SiMe4 for H and 13C, to SnMe4 for 119Sn, and to H3PO4 for 31P.
Elemental analyses were performed by the Division of Chemistry and
Biological Chemistry, Nanyang Technological University. Melting
points were measured in sealed glass tubes and were not corrected.
[(PPh2NSiMe3)(PPh2S)C{C(O)N(Ad)}Sn:] (2). A solution of
AdNCO (0.041 g, 0.23 mmol) in THF (5 mL) was added dropwise to
1 (0.14 g, 0.11 mmol) in THF (5 mL) at 0 °C. The yellow suspension
was stirred at room temperature and turned clear gradually. After it
was stirred for 34 h, the reaction mixture was a pale yellow clear
solution. Volatiles were removed in vacuo, and the residue was
extracted with toluene. After filtration and concentration of the filtrate,
2 was obtained as colorless crystals. Yield: 0.068 g (38.8%). Mp 217
°C dec. Anal. Calcd for C39H44N2OP2SSiSn: C, 58.72; H, 5.56; N,
3.51. Found: C, 58.50; H, 5.47; N, 3.14. 1H NMR (399.5 MHz, 25 °C,
C6D6): δ −0.043 (s, 9H, SiMe3), 1.59−1.66 (m, 6H, Ad), 1.87−1.89
(d, 3H, Ad), 1.96−2.00 (m, 6H, Ad), 6.99−7.03 (m, 12H, Ph), 7.35−
7.40 (m, 2H, Ph), 8.15−8.18 (m, 4H, Ph), 8.80−8.86 (m, 2H, Ph).
13C{1H} NMR (100.5 MHz, 25 °C, C6D6): δ 2.37 (SiMe3), 30.57,
37.52, 43.51 (Ad), 56.70 (dd, JP−C = 56.6 Hz, JP′−C = 70.0 Hz, PCP),
127.11, 127.24, 128.22, 130.26, 130.28, 130.85, 130.88, 131.69, 131.72
(CH of Ph), 132.64 (dd, JP−C = 57.3 Hz, 3JP′−C = 10.5 Hz, Cipso of Ph),
134.46 (dd, JP−C = 57.3 Hz, 3JP′−C = 11.5 Hz, Cipso of Ph), 165.16 ppm
(CO). 31P{1H} NMR (161.7 MHz, 25 °C, C6D6): δ 22.29 (d, 2JP−P′
2
2
= 17.3 Hz, JSn−P = 86.7, 121.4 Hz), 41.23 ppm (d, JP−P′ = 13.0 Hz,
2JSn−P = 47.7, 73.7 Hz). 119Sn{1H} NMR (147.6 MHz, 25 °C, C6D6): δ
−255.15 ppm (br).
Figure 3. Molecular structure of 4 with thermal ellipsoids at the 50%
probability level. Disordered CH2Cl2 molecules are omitted for clarity.
Selected bond lengths (Å) and angles (deg): Sn(1)−C(1) =
2.3617(16), Sn(1)−Cl(1) = 2.5311(4), Sn(1)−N(1) = 2.2535(13),
P(2)−N(1) = 1.6060(14), P(1)−S(1) = 2.0256(6), C(1)−P(2) =
1.7370(15), C(1)−P(1) = 1.7233(15), Rh(1)−C(1) = 2.1715(16),
Rh(1)−S(1) = 2.4005(4); C(1)−Sn(1)−N(1) = 68.42(5), C(1)−
Sn(1)−Cl(1) = 96.79(4), N(1)−Sn(1)−Cl(1) = 100.17(4), Sn(1)−
N(1)−P(2) = 98.34(6), N(1)−P(2)−C(1) = 101.84(7), P(2)−C(1)−
Sn(1) = 90.79(6), Sn(1)−C(1)−Rh(1) = 76.66(5), C(1)−Rh(1)−
S(1) = 77.67(4), Rh(1)−S(1)−P(1) = 78.247(17), S(1)−P(1)−C(1)
= 99.71(6), P(1)−C(1)−Rh(1) = 91.53(7), P(1)−C(1)−P(2) =
134.23(10).
[(PPh2NSiMe3)(PPh2S)C¯{C(O)N(Ar)}Sn+:] (3). A solution of
ArNCO (0.05 mL, 0.23 mmol) in THF (5 mL) was added dropwise to
1 (0.14 g, 0.11 mmol) in THF (5 mL) at 0 °C. The yellow suspension
was stirred at room temperature and turned clear gradually. After it
was stirred for 15 h, the reaction mixture was a pale yellow clear
solution. Volatiles were removed in vacuo, and the residue was
extracted with toluene. After filtration and concentration of the filtrate,
3 was obtained as colorless crystals. Yield: 0.066 g (36.5%). Mp 185
°C dec. Anal. Calcd for C41H46N2OP2SSiSn: C, 59.78; H, 5.63; N,
3.40. Found: C, 59.53; H, 5.57; N, 3.32. 1H NMR (399.5 MHz, 22 °C,
3
C6D6): δ 0.21 (s, 9H, SiMe3), 0.51 (d, JH−H = 6.9 Hz, 3H,
CH(CH3)2), 0.67 (d, 3JH−H = 6.4 Hz, 3H, CH(CH3)2), 1.20 (d, 3JH−H
(GeCl)]7b (2.204(3) Å) and [(PPh2NSiMe3)2C{Rh(cod)}2]
(2.148(2), 2.168(2) Å).15d
In conclusion, the formation of [(PPh2NSiMe3)(PPh2
= 6.9 Hz, 3H, CH(CH3)2), 1.37 (d, 3JH−H = 6.8 Hz, 3H, CH(CH3)2),
3
3
2.26 (sept, JH−H = 6.8 Hz, 1H, CH(CH3)2), 3.03 (sept, JH−H = 6.9
Hz, 1H, CH(CH3)2), 6.40−6.45 (m, 2H, Ph), 6.51−6.57 (m, 4H, Ph),
6.83−6.87 (m, 1H, Ph), 7.03−7.16 (m, 4H, Ph), 7.23−7.27 (m, 1H,
Ph), 7.33−7.38 (m, 5H, Ph), 7.83 − 7.89 (m, 2H, Ph), 8.60−8.70 (m,
4H, Ph). 13C{1H} NMR (100.5 MHz, 25 °C, C6D6): δ 4.73 (SiMe3),
24.29, 24.70, 25.99, 26.64 (CH(CH3)2), 28.87, 29.13 (CH(CH3)2),
40.64 (dd, JP−C = 56.6 Hz, JP′−C = 74.3 Hz, PCP), 123.86, 124.18,
126.72, (Ar) 127.78, 127.91, 128.84, 128.87, 128.98, 129.00, 130.56,
130.59, 131.36, 131.39 (CH of Ph), 132.22 (dd, JP−C = 79.4 Hz, 3JP′−C
S)C{C(O)N(Ad)}Sn:] (2) and [(PPh2NSiMe3)(PPh2
S)C¯{C(O)N(Ar)}Sn+:] (3) illustrate that the reactions of 1
with isocyanates probably proceed via a [2 + 2] cycloaddition
of the >CSn: bond or an insertion reaction of the C−Sn+
bond with the NC bond of RNCO (R = Ad, Ar). Moreover,
the formation of [(PPh2NSiMe3)(PPh2S)C{Rh(cod)}-
(SnCl)] (4) underlines the nucleophilic character of the
Cmethanediide atom in 1. Furthermore, X-ray crystal structures
show that the C−Sn bonds in 2−4 are lengthened in
comparison with that in 1. These results are consistent with
the X-ray crystal structure and NBO analyses of 1, which show
that the Sn−Cmethanediide bond has some double-bond character
and the electron densities are mostly occupied by the
Cmethanediide atom. Thus, compound 1 could be between the
resonance forms [(PPh2NSiMe3)(PPh2S)CSn:]2 and
[(PPh2NSiMe3)(PPh2S)C−Sn:+]2.
3
= 11.5 Hz, Cipso of Ph), 134.20 (dd, JP−C = 75.8 Hz, JP′−C = 10.5 Hz,
Cipso of Ph), 140.56, 146.58, 146.77 (Ar), 166.82 ppm (CO).
31P{1H} NMR (161.7 MHz, 22 °C, C6D6): δ 27.79 (d, 2JP−P′ = 8.7 Hz,
2
2
2JSn−P = 69.4, 86.7 Hz), 37.44 ppm (d, JP−P′ = 8.7 Hz, JSn−P = 73.7,
134.4 Hz). 119Sn{1H} NMR (149.0 MHz, 22 °C, C6D6): δ −129.25
ppm (br).
[(PPh2NSiMe3)(PPh2S)C{Rh(cod)}(SnCl)] (4). A solution of
[RhCl(cod)]2 (0.079 g, 0.16 mmol) in THF (8.4 mL) was added
dropwise to a solution of 1 (0.20 g, 0.16 mmol) in THF (8.4 mL) at 0
°C. The yellow suspension was then stirred at room temperature and
turned clear and red gradually. After it was stirred for 5 h, the reaction
mixture became a red suspension with yellow solid. Volatiles were
removed in vacuo, and the residue was extracted with CH2Cl2. After
filtration and concentration of the filtrate, 4 was obtained as red
crystals. Yield: 0.18 g (55.4%). Mp 140 °C dec. Anal. Calcd for
C36H41ClNP2RhSSiSn: C, 49.87; H, 4.77; N, 1.62. Found: C, 49.63; H,
EXPERIMENTAL SECTION
All manipulations were carried out under an inert atmosphere of
nitrogen gas using standard Schlenk techniques. THF and toluene
were dried over and distilled over Na/K alloy prior to use. CH2Cl2 was
■
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Article
Table 1. Crystallographic Data for Compounds 2−4
2
3
4
formula
Mr
C39H44N2OP2SSiSn
C41H46N2OP2SSiSn
823.58
C37.5H47Cl4NP2RhSSiSn
997.5
797.54
color
colorless
colorless
red
cryst syst
space group
a/Å
monoclinic
C2/c
monoclinic
P21/c
monoclinic
P21/n
30.8813(11)
11.1580(4)
22.3386(8)
90
9.4127(3)
21.5662(6)
19.0244(5)
90
11.7899(2)
16.7568(3)
20.4015(3)
90
b/Å
c/Å
α/deg
β/deg
γ/deg
V/Å3
Z
104.853(2)
90
95.3480(10)
90
97.5720
90
7440.1(5)
8
3845.07(19)
4
3995.39(11)
4
d
calcd/g cm−3
1.424
1.423
1.658
μ/mm−1
0.895
0.868
1.497
F(000)
3280
1696
2008
cryst size/mm
index range
0.34 × 0.28 × 0.26
−44 ≤ h ≤ 44
−16 ≤ k ≤ 13
−32 ≤ l ≤ 32
76 461
0.34 × 0.30 × 0.16
−15 ≤ h ≤ 15
−32 ≤ k ≤ 34
−30 ≤ l ≤ 29
73 823
0.40 × 0.34 × 0.30
−19 ≤ h ≤ 17
−27 ≤ k ≤ 27
−32 ≤ l ≤ 32
74 292
no. of rflns collected
R1, wR2 (I > 2σ(I))
R1, wR2 (all data)
0.0612, 0.1625
0.0948, 0.1916
1.351
0.0333, 0.0779
0.0507, 0.0928
1.082
0.0290, 0.0657
0.0412, 0.0704
1.045
goodness of fit, F2
no. of data/restraints/params
largest diff peak, hole/e Å−3
11 810/623/639
0.665, −1.421
17 312/0/449
0.831, −0.750
17 658/3/457
1.436, −1.100
4.64; N, 1.43. 1H NMR (399.5 MHz, 25 °C, THF-d8): δ 0.065 (s, 9H,
SiMe3), 1.57−2.61 (m, 8H cod), 3.21 (m, 1H, cod), 4.14 (m, 1H,
cod), 4.43 (m, 1H, cod), 4.91 (m, 1H, cod), 7.06−7.15 (m, 4H, Ph),
7.21−7.37 (m, 9H, Ph), 7.45−7.56 (m, 3H, Ph), 7.72−7.77 (m, 2H,
Ph), 8.04−8.09 (m, 2H, Ph). 13C{1H} NMR (100.5 MHz, 25 °C,
THF-d8): δ 3.43 (SiMe3), 29.04, 30.40, 32.89, 34.15 (sp3 C of cod),
77.41 (d, JC−Rh = 11.1 Hz, sp2 C of cod), 81.68 (d, JC−Rh = 12.1 Hz, sp2
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by the Academic Research Fund Tier
1 (RG 57/11).
C of cod), 85.23 (d, JC−Rh = 10.1 Hz, sp2 C of cod), 87.11 (d, JC−Rh
=
8.0 Hz, sp2 C of cod), 128.12, 128.23, 128.68, 128.81, 129.00, 129.13,
129.20, 129.31, 131.53, 132.12 (CH of Ph), 132.59 (dd, JP−C = 57.3
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