Transition metal complexes of (schiff base)divalent group 14 element species [(salen)M](n)=M'(CO)(6-n) (n = 1, 2; M = Ge, Sn, Pb; M'= Cr, W)

Article abstract of DOI:10.1002/(SICI)1099-0682(200004)2000:4<693::AID-EJIC693>3.0.CO;2-J

The syntheses, characterization, and reactivities of the new stable mono- and cis-disubstituted Group 14 metal(II) chromium and tungsten carbonyl complexes (salen)M=M'(CO)₅ [salen = 2,2'-N,N'- bis(salicylidene)ethylenediamine; M' = Cr, M = Ge (4), Sn (5), Pb (6); M' = W, M = Ge (7), Sn (8), Pb (9)] and [(salen)M]₂=M'(CO)₄ [M' = W, M = Ge (10), Sn (11), Pb (12); M' = Cr, M = Sn (14), Ge (15)] are described. Complexes 4-9 were obtained in high yields by treatment of the M'(CO)₅. THF intermediates with the stable divalent species (salen)M(II) [M = Ge (1), Sn (2), Pb (3)]. Direct irradiation of mixtures of (salen)M(II) and M'(CO)₆ resulted in formation of the monosubstituted compounds 4-9 together with the disubstituted species 10-12, 14, and 15 in ratios depending on the nature of both M and M'. Pure complexes 10-12 were obtained by two different synthetic approaches starting from the (salen)M(II) species or the (salen)M=M'(CO)₅ complexes. Each of the new complexes has been characterized by ¹H- and ¹³C-NMR, and by ¹¹⁹Sn-NMR in the case of 5, 8, 11, and 14, as well as by IR spectroscopy in all cases. The molecular structures of 5, 8, 11, and 14, determined by X-ray structure analyses, reveal a pentacoordinated tin atom. The tin-chromium distances are among the shortest (in particular that in 5, 2.557 A) observed for transition metal divalent tin complexes and the tin lies about 0.99 A above the plane defined by the O₂N₂ atoms of the salen ligand. All these complexes have been found to be unreactive towards water and organic acids. Simple phosphane monosubstitution of carbonyl in 8 using Ph₃P led to the new complex 13. Reactions with 1,2- bis(diphenylphosphanyl)ethane and 3,5-di-tert-butyl-1,2-benzoquinone resulted in displacement of the divalent species from the carbonyl complexes 5 and 8.

Full text of DOI:10.1002/(SICI)1099-0682(200004)2000:4<693::AID-EJIC693>3.0.CO;2-J

FULL PAPER
Transition Metal Complexes of (Schiff Base)Divalent Group 14 Element
Species [(salen)M]n؍MЈ(CO)6–n (n ؍ 1, 2; M ؍ Ge, Sn, Pb; MЈ ؍ Cr, W)
Dominique Agustin,[a] Ghassoub Rima,[a] Heinz Gornitzka,[a] and Jacques Barrau*[a]
Keywords: Germylene / Stannylene / Plumbylene / Schiff base / Transition metal complexes of M14 divalent species
The syntheses, characterization, and reactivities of the new
stable mono- and cis-disubstituted Group 14 metal(II) chro- and 13C-NMR, and by 119Sn-NMR in the case of 5, 8, 11, and
Each of the new complexes has been characterized by 1H-
mium and tungsten carbonyl complexes (salen)M=MЈ(CO)5
[salen = 2,2Ј-N,NЈ-bis(salicylidene)ethylenediamine; MЈ = Cr,
M = Ge (4), Sn (5), Pb (6); MЈ = W, M = Ge (7), Sn (8), Pb (9)]
14, as well as by IR spectroscopy in all cases. The molecular
structures of 5, 8, 11, and 14, determined by X-ray structure
analyses, reveal a pentacoordinated tin atom. The tin–chro-
and [(salen)M]2=MЈ(CO)4 [MЈ = W, M = Ge (10), Sn (11), Pb mium distances are among the shortest (in particular that in
˚
5, 2.557 A) observed for transition metal divalent tin com-
(12); MЈ = Cr, M = Sn (14), Ge (15)] are described. Complexes
4–9 were obtained in high yields by treatment of the plexes and the tin lies about 0.99 A above the plane defined
˚
MЈ(CO)5 THF intermediates with the stable divalent species
(salen)MII [M = Ge (1), Sn (2), Pb (3)]. Direct irradiation of
mixtures of (salen)MII and MЈ(CO)6 resulted in formation of
the monosubstituted compounds 4–9 together with the disub-
by the O2N2 atoms of the salen ligand. All these complexes
have been found to be unreactive towards water and organic
acids. Simple phosphane monosubstitution of carbonyl in 8
using Ph3P led to the new complex 13. Reactions with 1,2-
stituted species 10–12, 14, and 15 in ratios depending on the bis(diphenylphosphanyl)ethane and 3,5-di-tert-butyl-1,2-
nature of both M and MЈ. Pure complexes 10–12 were ob- benzoquinone resulted in displacement of the divalent spe-
tained by two different synthetic approaches starting from
the (salen)MII species or the (salen)M=MЈ(CO)5 complexes.
cies from the carbonyl complexes 5 and 8.
Introduction
species L2M [L2 ϭ 2,2Ј-N,NЈ-bis(salicylidene)ethylenediam-
ine (salen), (R,R)-(–)-N,NЈ-bis(3,5-di-tert-butylsalicylidene)-
1,2-cyclohexanediamine, and N-methyl-2,2Ј-iminobis(8-hy-
droxyquinoline); M ϭ Ge, Sn, Pb].[15] These compounds
are monomeric and feature twofold N M intramolecular
coordination, which lowers the Lewis acidity of the metal
atom (characteristic of the free divalent species). Neverthe-
less, they are efficient σ donors and can be used as mono-
dentate ligands in transition metal chemistry. In this work,
we consider the salen compounds (salen)M (M ϭ Ge, Sn,
Pb) as precursors of new L2MϭMЈ(CO)5 and (L2M)2ϭ
MЈ(CO)4 complexes (M ϭ Ge, Sn, Pb; MЈ ϭ Cr, W). The
syntheses, crystal structures, and some chemical properties
of these bimetallic compounds are presented herein.
Heavier analogs of carbenes can be used as ligands in
transition metal chemistry. They can play an important role
in the synthesis of precursors of new materials, and various
metallic analogs of carbenic complexes of transition metals
have been used or postulated as catalysts in reactions invol-
ving the formation or cleavage of M–M bonds. The major-
ity of characterized complexes involve four-coordinate M
atoms with type II structures; with bulky or donor substitu-
ents, a few structures with a three-coordinate M atom
(structure I) have been isolated. Only a few examples of
complexes with structures of type III having a five-coordin-
ate M atom have been observed.
The earlier chemistry of these transition metal complexes
with divalent species of Group 14 elements has been sum-
marized in various review articles;[1–5] recent investigations
concern mainly tin–Group
6 transition metal com-
plexes.[6–14]
Recently, we reported the synthesis and characterization
of new stable divalent germanium, tin, and lead homoleptic
[a]
´ ´
´
Heterochimie Fondamentale et Appliquee, UPRES-A 5069 du
´
CNRS, Universite Paul-Sabatier,
118 route de Narbonne, F-31062 Toulouse Cedex, France
Fax: (internat.) ϩ 33-5/61 55 82 04
E-mail: barrau@ramses.ups-tlse.fr
Scheme 1
Eur. J. Inorg. Chem. 2000, 693Ϫ702
WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000
1434Ϫ1948/00/0404Ϫ0693 $ 17.50ϩ.50/0
693

D. Agustin, G. Rima, H. Gornitzka, J. Barrau
FULL PAPER
up to 70% yield by irradiation of a mixture of (salen)M and
(salen)MϭW(CO)5 or by irradiation of a mixture of two
equivalents of (salen)M and one of W(CO)6 (Scheme 3).
Results and Discussion
Synthesis of Complexes of Divalent Species (salen)M؍
MЈ(CO)5 and [(salen)M]2؍MЈ(CO)4 (M ؍ Ge, Sn, Pb;
MЈ ؍ Cr, W)
Treatment
of
the
photochemically
produced
MЈ(CO)5 THF intermediates with the (salen)M com-
pounds in THF led to the expected monosubstituted com-
plexes 4–9 in high yields (Scheme 1).
Scheme 3
These complexes were obtained as yellow-orange crystalline
solids in yields in excess of 80% by recrystallization from
CHCl3. They were found to be soluble only in polar and pro-
tic solvents (THF, CHCl3, CH2Cl2, DMSO, DMF, MeOH).
Direct irradiation at room temperature of mixtures of the di-
valent compounds (salen)M and the hexacarbonyl complexes
MЈ(CO)6 (MЈ ϭ Cr, W) also resulted in the formation of the
expected monometal(II) complexes in yields depending on the
nature of both the Group 14 atom M and the transition metal
MЈ (Scheme 2). With (salen)germylene and -stannylene, the
mono compounds 4 and 5 were produced in high yields when
the reactions were carried out using Cr(CO)6. Using W(CO)6
under similar reaction conditions, substitution of more than
one carbonyl was observed and the disubstituted compounds
10–12 with the ligands in a cis arrangement were formed
alongside the monosubstituted species 7–9 (Scheme 2). Exten-
sion of this procedure to the reactions of (salen)plumbylene
with Cr(CO)6 and W(CO)6 led to complexes 6 in 70% yield
It is interesting to note that under UV irradiation, the
cis-[(salen)M]2ϭMЈ(CO)4 complexes were converted into
the trans isomers. Such conversions have been particularly
well-studied in the case of 11; irradiation of a solution of
cis-[(salen)Sn]2ϭW(CO)4 (11) for 6 h resulted in 50% con-
version to trans-[(salen)Sn]2ϭW(CO)4 (11Ј). Crystals of 11Ј
suitable for X-ray structural analysis could not be obtained
1
but its H- and 13C-NMR data, a 119Sn-NMR resonance
at δ ϭ –374, an IR band at νCO ϭ 1999 cm–1, and mass
spectroscopic data were consistent with the trans structure.
Such cis/trans photochemical isomerizations, as well as
thermal reverse conversions, have previously been reported
in the case of (carbene)2ϭW(CO)4.[16] In our case, it has
not been possible to unambiguously observe reversion to
the thermodynamically favoured cis isomer by heating a
mixture of 11 and 11Ј in the solid state or in solution. When
a solid-state 50:50 cis/trans mixture was maintained at
180 °C for 12 h, the subsequently recorded 119Sn-NMR
spectrum featured only resonances due to the cis isomer
(δ ϭ –348) and due to an unidentified product (δ ϭ –410).
Compounds 4–12 were found to be soluble in polar and
protic solvents and insoluble in pentane. All these com-
pounds proved to be stable to moisture.
1
and to a mixture of 9 and 12 (30:70, as determined by H-
NMR), respectively. In contrast, attempts to prepare the (sa-
len)MϭMЈ(CO)5 (MЈ ϭ Cr, W) complexes simply by heating
mixtures of the starting materials at 80 °C for 24 h proved un-
successful.
Physicochemical and Structural Studies of the (salen)M؍
MЈ(CO)5 and [(salen)M]2؍MЈ(CO)4 Complexes (M ؍ Ge,
Sn, Pb; MЈ ؍ Cr, W)
Molecular weight determinations (cryoscopy in benzene)
showed 4, 5, 7, and 8 to be monomeric in solution. Com-
pounds 4–12 have been characterized by 1H-, 13C-, and
119Sn-NMR (for the complexes 5, 8, and 11), as well as by
IR spectroscopy. 1H- and 119Sn-NMR and IR spectroscopic
data are collected in Table 1. The thermal stabilities of these
complexes were found to be high; they decompose only on
melting, but the germanium and tin complexes proved suffi-
ciently volatile to allow recording of their mass spectra.
1
The H-NMR spectra of complexes 4–12 show different
shifts for the signals of the salen ligand relative to those
seen for the divalent compounds 1–3. The most noticeable
shifts are seen in the methine proton resonances, which ap-
pear at lower field strengths as compared to those of the
parent divalent species. For compounds 10–12, NMR can-
not distinguish between the two tin species complexed on
Scheme 2
In view of the particular sensitivity of the tungsten sys- the tungsten since the NMR signals of the various protons
tem and the difficulties encountered in separating the are similar and therefore non-resolvable. In all cases, as in
mono- and disubstituted tungsten products, we investigated 1–3, the chemical shifts and splitting patterns of the CH2N
alternative synthetic methods to confirm the structures of protons are consistent with the presence of NǞM intramo-
10–12. Thus, syntheses of pure 10 and 11 were achieved in lecular coordination in these molecules.
694
Eur. J. Inorg. Chem. 2000, 693Ϫ702

Transition Metal Complexes of (Schiff Base)Divalent Group 14 Element Species
FULL PAPER
Table 1. Spectroscopic data for compounds 4–12
4
5
6
7
8
9
10
11
12
1H (δ, ppm)
CH2
3.90
8.32
4.01
8.42
–137
1638
1917
1978
2047
3.80
8.24
3.93
8.25
3.99
8.73
–328
1641
1913
1977
2063
3.87
8.27
3.93
8.17
3.81
8.43
–348
1638
1902
1929
1954
2062
4.07
8.03
CHϭN
119Sn (δ, ppm) ([D6]DMSO)
IR (Nujol, KBr, cm–1)
νCϭN
νCϭO
1630
1910
1970
2047
1620
1915
1976
2048
1620
1916
1972
2067
1630
1914
1970
2060
1620
1892
1980
2009
2060
1625
1906
1930
2015
2060
The 13C-NMR spectra of 4–12 feature signals with the
characteristic chemical shifts of the carbon atoms of the
salen ligand, shifted slightly downfield from those in the
(salen)M compounds,[15] along with two carbonyl reson-
ances for the monosubstituted complexes 4–9 (relative in-
tensity 1:4) and for the disubstituted complexes 10–12 (rel-
ative intensity 1:1).
The 119Sn-NMR spectra of 5, 8, and 11 feature singlets
at δ ϭ –137, –328, and –348, respectively, which fall within
the range of shift values appropriate for pentacoordinate
tin compounds; the shift variations between the signal of
(salen)Sn and those of the corresponding (salen)Snϭ
MЈ(CO)5 complexes reflect the electron-withdrawing effect
1
of the MЈ(CO)5 groups. The J(119Sn-183W) coupling con-
stants are very similar to those observed in four-coordinate
Figure 1. Solid-state structure and atom numbering scheme of (sa-
len)SnϭCr(CO)5 (5)
tin(II)–tungsten compounds.[16]
The IR spectra of compounds 4–9 show strong absorp-
tions in the range 1620–1640 cm–1 attributable to the
νCϭN stretching frequency under the influence of the NǞM
intramolecular coordination; these bands are shifted toward
higher frequencies by 5–20 cm–1 in comparison with the
spectra of the free ligands but are not affected to any appre-
ciable extent compared to those observed for the (salen)M
compounds. In the metal carbonyl region, three carbonyl
bands (AЈЈ1 ϩ AЈ1 ϩ E) are seen, with an intensity pattern
characteristic of C4v local symmetry at chromium or tung-
sten. Since the unique CO trans to the metal M is involved
in the AЈ1 mode, the position of this band [1970 (4), 1978
(5), 1976 cm–1 (6)] is indicative[18] of the π-acceptor ability
of the (salen)M groups trans to the axial carbonyl. IR and
13C-NMR data show that the (salen)M ligands are stronger
donors of electron density, but are also π-acceptors. For
complexes 10–12, the appearance of four bands due to the
CO groups is compatible with C2v symmetry (cis geometry).
The five-coordinate environment about the M atom was
Figure 2. Solid-state structure and atom numbering scheme of (sa-
len)SnϭW(CO)5 (8)
confirmed structurally for 5, 8, and 11. Compound 11 rep- cupying the base plane at Sn–N2O2 plane distances of 0.948
resents the first distannylene–tungsten complex [L2Sn]2ϭ A in 5, 0.996 A in 8, and 1.005 A and 1.024 A in 11. The
˚
˚
˚
˚
˚
W(CO)4 to be structurally characterized. Figure 1, Figure 2, observed σ Sn–O distances [2.039(3)–2.074(3) A] are a little
and Figure 3 show solid-state structures of 5, 8, and 11, longer than classical σ Sn–O bonds (1.94–2.03 A).
[19]
˚
The
˚
respectively, together with the numbering scheme adopted. lengths of the SnǟN bonds [2.230(5)–2.288(4) A] appear
In the case of 11, the three CHCl3 solvating molecules are to be normal. On going from 5 to 8 and 11, these Sn–N
omitted for the sake of clarity. Crystal data of 5, 8, and 11 and Sn–O distances increase as a result of the decreased
are presented in Table 6. Relevant bond lengths and angles inductive effect of the transition metal fragment. The tin–
in 5, 8, and 11 are given in Table 2, Table 3, and Table 4, chromium or tin–tungsten bonds, which are shorter than
respectively. In all three compounds, the tin resides in a dis- typical Sn–MЈ (MЈ ϭ Cr, W) single bonds,[20] are among
torted square-pyramidal geometry with the salen ligand oc- the shortest ever observed in transition metal–divalent tin
Eur. J. Inorg. Chem. 2000, 693Ϫ702
695

D. Agustin, G. Rima, H. Gornitzka, J. Barrau
FULL PAPER
˚
Table 4. Selected bond lengths [A] and angles [deg] in 11
Distances
Angles
Sn(1)–W(1)
Sn(1)–O(4)
Sn(1)–O(3)
Sn(1)–N(4)
Sn(1)–N(3)
Sn(2)–W(1)
Sn(2)–O(2)
Sn(2)–O(1)
Sn(2)–N(2)
Sn(2)–N(1)
W(1)–C(35)
W(1)–C(34)
W(1)–C(33)
W(1)–C(36)
2.711(1)
2.062(3)
2.086(4)
2.265(4)
2.282(4)
2.703(1)
2.066(3)
2.074(3)
2.261(4)
2.288(4)
1.953(6)
1.964(6)
2.013(7)
2.028(7)
O(4)–Sn(1)–O(3)
O(4)–Sn(1)–N(4)
O(3)–Sn(1)–N(4)
O(4)–Sn(1)–N(3)
O(3)–Sn(1)–N(3)
N(4)–Sn(1)–N(3)
O(4)–Sn(1)–W(1)
O(3)–Sn(1)–W(1)
N(4)–Sn(1)–W(1)
N(3)–Sn(1)–W(1)
O(2)–Sn(2)–O(1)
O(2)–Sn(2)–N(2)
O(1)–Sn(2)–N(2)
O(2)–Sn(2)–N(1)
O(1)–Sn(2)–N(1)
N(2)–Sn(2)–N(1)
O(2)–Sn(2)–W(1)
O(1)–Sn(2)–W(1)
N(2)–Sn(2)–W(1)
N(1)–Sn(2)–W(1)
Sn(2)–W(1)–Sn(1)
82.57(14)
79.43(14)
137.91(15)
108.90(14)
79.91(14)
70.65(16)
116.76(9)
115.26(11)
106.82(11)
133.06(10)
79.67(14)
81.40(16)
124.75(15)
125.58(15)
80.00(15)
70.29(17)
125.30(12)
115.03(10)
118.30(11)
109.07(10)
96.161(15)
Figure 3. Solid-state structure and atom numbering scheme of
{[(salen)Sn]2ϭW(CO)4} 3 (CHCl3) (11); solvent molecules have
been omitted for the sake of clarity
˚
Table 2. Selected bond lengths [A] and angles [deg] in 5
liar arrangement resulting from the structure of the salen
ligand maximizes the possibility of [d(MЈ)-d(p)(Sn)] π over-
lap.
Distances
Angles
Sn(1)–Cr(2)
Sn(1)–O(1)
Sn(1)–O(2)
Sn(1)–N(2)
Sn(1)–N(1)
Cr(2)–C(21)
Cr(2)–C(18)
Cr(2)–C(20)
Cr(2)–C(17)
Cr(2)–C(19)
2.578(1)
2.041(4)
2.058(4)
2.230(5)
2.260(5)
1.861(6)
1.873(7)
1.886(6)
1.894(7)
1.915(7)
O(1)–Sn(1)–O(2)
O(1)–Sn(1)–N(2)
O(2)–Sn(1)–N(2)
O(1)–Sn(1)–N(1)
O(2)–Sn(1)–N(1)
N(2)–Sn(1)–N(1)
O(1)–Sn(1)–Cr(2)
O(2)–Sn(1)–Cr(2)
N(2)–Sn(1)–Cr(2)
N(1)–Sn(1)–Cr(2)
82.27(16)
121.22(16)
80.95(16)
81.41(17)
134.07(18)
71.72(17)
120.85(12)
115.05(12)
117.33(11)
110.20(13)
˚
˚
The Sn–W distances in 8 [2.712(1) A] and 11 [2.711(1) A
˚
and 2.703(1) A] are very similar, which shows that the
strength of the π interaction between the transition metal
and the tin atom is not influenced by the number of dival-
ent species on the transition metal. In 5, 8, and 11, the
coordination about the Cr or W atom is almost perfectly
octahedral. In each compound, the MЈ–C distances are very
similar; the MЈ–C bonds trans to Sn are the shortest, but
do not differ significantly from the MЈ–C equatorial bonds.
This suggests that the (salen)Sn ligand is comparable to or
slightly poorer than CO as a π acceptor.
˚
Table 3. Selected bond lengths [A] and angles [deg] in 8
The mass spectra of complexes 4, 5, 7, and 8 exhibit
peaks corresponding to molecular ions Mϩ [weak (4 and 7)
or very weak (5 and 8) intensity] and to the characteristic
fragmentations of such structures (particularly loss of car-
bonyl groups and of substituents on the Ge and Sn atoms).
Distances
Angles
W(1)–Sn(1)
Sn(1)–O(6)
Sn(1)–O(7)
Sn(1)–N(2)
Sn(1)–N(1)
W(1)–C(3)
W(1)–C(1)
W(1)–C(2)
W(1)–C(4)
W(1)–C(5)
2.712(1)
2.039(3)
2.074(3)
2.260(3)
2.261(3)
1.994(4)
2.032(4)
2.039(5)
2.040(5)
2.057(4)
O(6)–Sn(1)–O(7)
O(6)–Sn(1)–N(2)
O(7)–Sn(1)–N(2)
O(6)–Sn(1)–N(1)
O(7)–Sn(1)–N(1)
N(2)–Sn(1)–N(1)
O(6)–Sn(1)–W(1)
O(7)–Sn(1)–W(1)
N(2)–Sn(1)–W(1)
N(1)–Sn(1)–W(1)
81.02(11)
118.87(12)
79.77(11)
80.05(11)
131.39(11)
71.27(12)
123.81(9)
115.95(8)
116.83(8)
111.83(9)
Chemical Reactivity of the (salen)M؍MЈ(CO)5 Complexes
Due to their ‘‘transition metal–carbene-like’’ character,
the (salen)MϭMЈ(CO)5 complexes would appear to have
interesting potential in organometallic chemistry. However,
˚
complexes, the Sn–Cr distance [2.558(1) A] in complex 5 as observed previously, the chemistry of the complexes
being particularly short. These distances reflect a lower L2MϭMЈ(CO)5 differs markedly from that of their carbene
electron density at the tin atom in these complexes and may counterparts despite the many structural similarities.
be indicative of double-bond character in the Sn–MЈ unit
(typical SnϭCr: 2.60 A,
In contrast to their parent compounds (1–3) and various
[7,21,22]
SnϭW: 2.74 A[10,17,23,24]). L2MϭMЈ(CO)5 complexes, the (salen)MϭMЈ(CO)5 and
˚
˚
Thus, it seems that despite its tetradentate capacity the [(salen)M]2ϭMЈ(CO)4 complexes 4–12 were found to be
salen ligand does not cancel out the electronic deficiency totally unreactive towards water and organic acids
at the tin atom through N Sn intramolecular coordination (Scheme 3). This lack of reactivity may be attributed to elec-
thereby reducing the back-donation by the transition metal. tronic and particularly steric factors, most notably about
Conversely the solid-state structures suggest that the pecu- the tin atom.
696
Eur. J. Inorg. Chem. 2000, 693Ϫ702

Transition Metal Complexes of (Schiff Base)Divalent Group 14 Element Species
FULL PAPER
With iodine, we observed the expected reactions for com- to the νCO region were in agreement with an octahedral
pounds with Group 14 metal–transition metal bonds coordination sphere about the chromium center and a cis
(Scheme 4).
geometry. This conclusion was confirmed by an X-ray crys-
tal structure determination (Figure 4, Table 5). The struc-
Scheme 4
Since ligands having a lone pair, such as Ph3P, are able
to substitute one or more of the CO groups of metal car-
bonyls, the monotriphenylphosphane complex of 8 (or 13,
respectively) could easily be prepared by UV irradiation
(λ ϭ 254 nm) or by heating (Scheme 4). In contrast, at-
tempted substitution of two CO groups by the chelating
ligand 1,2-bis(diphenylphosphanyl)ethane (diphos) were
unsuccessful; reactions of this doubly chelating phosphane
with 5 and 8 surprisingly led to the distannylene–metal car-
bonyl complexes 14 and 11, respectively (Scheme 5).
Figure 4. Solid-state structure and atom numbering scheme of
{[(salen)Sn]2ϭCr(CO)4} 3 (CHCl3) (14); solvent molecules have
been omitted for the sake of clarity
˚
Table 5. Selected bond lengths [A] and angles [deg] in 14
Distances
Angles
Scheme 5
Sn(1)–Cr(1)
Sn(1)–O(1)
Sn(1)–O(2)
Sn(1)–N(2)
Sn(1)–N(1)
Sn(2)–Cr(1)
Sn(2)–O(3)
Sn(2)–O(4)
Sn(2)–N(3)
Sn(2)–N(4)
Cr(1)–C(33)
Cr(1)–C(34)
Cr(1)–C(35)
Cr(1)–C(36)
2.568(1)
2.085(3)
2.057(3)
2.262(3)
2.288(4)
2.555(1)
2.071(3)
2.071(3)
2.255(4)
2.293(4)
1.875(5)
1.833(5)
1.831(5)
1.875(5)
O(1)–Sn(1)–O(2)
O(1)–Sn(1)–N(1)
O(1)–Sn(1)–N(2)
O(2)–Sn(1)–N(1)
O(2)–Sn(1)–N(2)
N(1)–Sn(1)–N(2)
O(3)–Sn(2)–O(4)
O(3)–Sn(2)–N(3)
O(3)–Sn(2)–N(4)
O(4)–Sn(2)–N(3)
O(4)–Sn(2)–N(4)
N(3)–Sn(2)–N(4)
Sn(1)–Cr(1)–Sn(2)
82.08(11)
97.34(11)
137.73(13)
107.84(12)
79.49(12)
70.68(13)
79.48(12)
81.32(14)
125.70(13)
124.12(13)
79.80(12)
70.34(15)
96.97(3)
Since compounds 5 and 8 are stable towards UV irradi-
ation, it seems that in these cases entry of a second phos-
phane group into the coordination sphere about MЈ causes
displacement of the (salen)Sn ligand, which reacts in situ
with remaining 5 or 8 to give 14 or 11, respectively
(Scheme 6).
Scheme 6
Complex 14 could be separated from the reaction mixture
in the form of orange crystals, by virtue of its low solubility
in pentane. The 13C-NMR spectrum and IR data relating Scheme 7
Eur. J. Inorg. Chem. 2000, 693Ϫ702
697

D. Agustin, G. Rima, H. Gornitzka, J. Barrau
FULL PAPER
ture shows similarities to that of 11; the two cis-stannane-
diyl fragments (salen)Sn, in which the tin atoms show dis-
torted square-pyramidal geometries, are bonded to a
Cr(CO)4 fragment with an octahedral environment about
the chromium atom. The Cr–Sn distances [2.555(1) and
˚
2.568(1) A] are indicative of double-bond character in the
Cr–Sn unit.
Complexes 4, 5, 7, and 8 were found to react similarly
with equimolar amounts of 3,5-di-tert-butyl-1,2-benzoqui-
none (DBQ), leading to 15, 14, 10, and 11, respectively,
along with the MЈ(CO)2(DBCat)2 complexes (Scheme 7).
This reaction is consistent with a mechanism involving
initial interaction of the quinone with the transition metal
atom causing labilization of the M–MЈ bond as a result of
decreased π-back-bonding (this effect is amplified by che-
late ring formation as in the case of the reaction of diphos).
The resulting (salen)M ligand then primarily reacts with
(salen)MϭMЈ(CO)5, leading to the bis-(divalent species)–
transition metal complexes [(salen)M]2ϭMЈ(CO)4 rather
than with the quinone to give the corresponding catecholate
16 (Scheme 8). Supporting evidence for this explanation
was obtained by studying the relative reactivities of (sa-
len)Sn towards coordination to the transition metal in (sa-
len)SnϭCr(CO)5 and towards addition to the quinone.
Starting with a 1:1:1 mixture of (salen)Sn/DBQ/(salen)Snϭ
Cr(CO)5, the distannylene–chromium complex [(sa-
len)Sn]2ϭCr(CO)4 was by far the favored product (ratio
Scheme 8
97:3). No evidence of a stable semiquinone intermediate to the corresponding distannylene metal carbonyl com-
was observed in this reaction. Using two equivalents of 3,5- plexes; displacement of the (salen)Sn ligand seems to be the
di-tert-butyl-1,2-benzoquinone in addition to the disubsti- key step in such reactions.
tuted complexes, we observed substantial formation of the
previously characterized (salen)SnII-3,5-di-tert-butyl-1,2-
benzoquinone adduct 16.[15]
Experimental Section
General: All manipulations were performed under inert atmo-
spheres of nitrogen or argon using standard Schlenk and high-va-
cuum-line techniques. Dry, oxygen-free solvents were employed
throughout. All solvents were distilled from sodium benzophenone
Conclusion
Several new stable mono- and cis-disubstituted Group 14
metal(II)–chromium and tungsten carbonyl complexes have
been prepared and their reactivities towards phosphane and
3,5-di-tert-butyl-1,2-benzoquinone have been studied.
1
or P2O5 prior to use. H-NMR spectra were recorded on a Bruker
AC 80 spectrometer operating at 80 MHz (chemical shifts are re-
ported in ppm relative to internal Me4Si); 13C-NMR spectra were
recorded on an AC 200 spectrometer; the multiplicities of the 13C-
Physicochemical and structural studies have shown that the NMR signals were determined by the APT technique. 1H-de-
coupled 119Sn-NMR spectra were recorded on Bruker AC 200 or
Group 14 metal resides in a five-coordinate environment.
The Sn–MЈ bond lengths observed in the tin complexes
400 instruments (chemical shifts are reported in ppm relative to
external Me4Sn). Mass spectra were obtained under electron im-
are shorter than the typical single-bond lengths and are
pact (EI) or chemical ionization (CH4) conditions at 70 eV and
among the shortest ever observed (in particular the Sn–Cr
30 eV, respectively using Hewlett Packard 5989 and Nermag R10-
bond). This indicates that in these complexes, in spite of
10H spectrometers. IR spectra were recorded on a Perkin–Elmer
NǞM intramolecular coordination, the divalent species
(salen)M behave as σ-donors with π-acceptor properties.
These results underline the influence of the stabilizing li-
gand (bound to the Group 14 element) on the magnitude
1600 FT-IR spectrophotometer. Irradiations were carried out at
room temperature using a low-pressure immersion lamp in a quartz
glass immersion tube. Molecular weight determinations were car-
ried out with a custom-built apparatus. Melting points (uncorrec-
of the MϭM bonding interaction. In short, the (salen)Sn ted) were obtained on a Leitz Biomed hot-plate microscope appar-
atus. Elemental analyses (C, H, N) were performed at the Microan-
group, with its square-pyramidal geometry, seems to favor
the π interaction between the Group 14 element and the
chromium or tungsten atom.
´
alysis Laboratory of the Ecole Nationale Superieure de Chimie de
Toulouse.
Substitution of one CO group has been observed upon
reaction with PPh3. Interestingly, reactions with diphos and
X-ray Measurements of 5, 8, 11, and 14: Crystal data for all the
structures are presented in Table 6. All data were collected at T ϭ
3,5-di-tert-butyl-1,2-benzoquinone have been found to lead 173 K using an oil-coated shock-cooled crystal[25] in each case on
698
Eur. J. Inorg. Chem. 2000, 693Ϫ702

Transition Metal Complexes of (Schiff Base)Divalent Group 14 Element Species
FULL PAPER
Table 6. Crystallographic data for compounds (salen)SnϭCr(CO)5 (5), (salen)SnϭW(CO)5 (8), {[(salen)Sn]2ϭW(CO)4} 3 (CHCl3) (11),
and {[(salen)Sn]2ϭCr(CO)4} 3 (CHCl3) (14)
5
8
11
14
formula
MT
C21H14CrN2O7Sn
577.03
C21H14N2O7SnW
708.88
173(2)
C39H31Cl9N4O8Sn2W
1423.96
173(2)
C39H31Cl9N4O8Sn2Cr
1292.11
173(2)
T [K]
173(2)
crystal system
space group
monoclinic
P21/c
monoclinic
P21/n
monoclinic
C2/c
monoclinic
C2/c
˚
a [A]
12.213(2)
16.257(3)
11.691(2)
90
7.018(1)
14.692(2)
20.821(3)
90
22.456(4)
23.240(3)
18.636(3)
90
22.437(2)
23.048(3)
18.335(2)
90
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
115.24(2)
90
91.44(2)
90
96.38(2)
90
96.08(1)
90
3
˚
V (A )
2099.6(6)
4
2146.1(5)
4
9665(3)
8
9428.2(18)
8
Z
ρcalcd [Mg/m3]
cryst. size [mm]
µ [mm–1]
1.825
2.194
1.957
1.821
0.4 ϫ 0.4 ϫ 0.1
1.754
0.5 ϫ 0.3 ϫ 0.2
6.566
0.6 ϫ 0.5 ϫ 0.5
3.950
0.5 ϫ 0.3 ϫ 0.1
1.842
F(000)
2ϕmax [°]
1136
1336
5472
5072
46
48
46
48
refl. collected
indep. refl.
Rint
15265
16882
38119
38584
2962
3409
6889
7500
0.0687
0.0426
numerical
0.219/0.491
289
0.0514
0.0679
absorption correct.
Tmin, Tmax
parameters
R [I Ͼ 2σ(I)]
wR2[a]
numerical
0.678/0.830
289
numerical
0.307/0.603
640
numerical
0.607/0.798
676
0.0468
0.1086
0.0220
0.0561
0.0273
0.0691
0.0294
0.0618
(all data)
–3
˚
˚
(∆/ρ)min [e.A ]
–0.820
1.645
–0.702
0.720
–0.718
1.238
–0.596
0.737
–3
(∆/ρ)max [e.A ]
[a]
2
2 2
2 2
wR2 ϭ {[Σw(Fc – Fo ) ]/[Σw(Fo ) }1/2
.
a Stoe-IPDS diffractometer employing Mo-Kα (λ ϭ 0.71073 A) ra-
KBr): νCϭN 1630; νCO 1910, 1970, 2047 cm–1. – MS (EI, 70 eV):
m/z ϭ 532 [Mϩ ], 504 [M – CO]ϩ, 476 [M – 2 CO]ϩ, 448 [M –
˚
diation. The structures were solved by direct methods by means of
SHELXS-97[26] and refined with all data on F2 using SHELXL- 3 CO]ϩ, 420 [M – 4 CO]ϩ, 392 [M – 5 CO]ϩ. – C21H14CrGeN2O7
97.[27] All non-hydrogen atoms were refined anisotropically. Hydro-
gen atoms were placed in geometrically ideal positions and refined
using a riding model. Selected bond lengths and angles in 5, 8, 11,
and 14 are presented in tables 2, 3, 4, and 5, respectively. Crystallo-
graphic data (excluding structure factors) for the structures re-
ported in this paper have been deposited with the Cambridge Crys-
tallographic Data Centre as supplementary publication nos.
CCDC-136101 (5), 136102 (8), 136103 (11), and 136104 (14). Cop-
ies of the data can be obtained free of charge on application to the
CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K. [Fax: (in-
ternat.) ϩ44 (0)1223/336033; E-mail: deposit@ccdc.cam.ac.uk].
Synthesis of (salen)Ge؍Cr(CO)5 (4). – Procedure 1: A mixture of
(salen)Ge[15b] (0.51 g, 1.50 mmol) and Cr(CO)6 (0.33 g, 1.50 mmol)
in THF (50 mL) was irradiated for 2 h, during which a red color
developed. The solvent was then removed under reduced pressure
and the residual solid was treated with pentane. The resulting sus-
pension was filtered and the collected solid was dried in vacuo to
afford 4 (0.64 g, 80%) as an orange powder.
(531.94): calcd. C 47.37, H 2.65, N 5.26; found C 47.58, H 2.70,
N 5.10.
Synthesis of (salen)Sn؍Cr(CO)5 (5). – Procedure 1: A mixture of
(salen)Sn[15b] (0.26 g, 0.67 mmol) and Cr(CO)6 (0.15 g, 0.67 mmol)
in THF (50 mL) was irradiated for 2 h, during which a red color
developed. After removal of the solvent, the crude product was
treated with pentane and the resulting suspension was filtered.
Crystallization of the collected solid from chloroform afforded 5
(0.31 g, 80%) as red-orange crystals.
Procedure 2: Following a procedure similar to that described for
4, compound 5 (0.30 g, 83%) was obtained from (salen)Sn (0.24 g,
0.62 mmol) and Cr(CO)5THF (0.17 g, 0.62 mmol); m.p. 270–280
°C (dec.). – 1H NMR ([D6]DMSO): δ ϭ 4.01 (m, 4 H, CH2), 6.50–
7.50 (m, 8 H, Ar), 8.42 (s, 2 H, CHϭN). – 13C NMR ([D6]DMSO):
δ ϭ 52.86 (CH2), 117.77 (CHAr), 118.97 (Cq), 122.32 (CHAr),
134.58 (CHAr), 135.90 (CHAr), 165.65 (Cq–O), 169.41 (CHϭN),
218.54 (CϭO), 230 (CϭO). – 119Sn{1H} NMR ([D6]DMSO): δ ϭ
–149.5. – IR (Nujol, KBr): νCϭN 1638; νCO 1917, 1978, 2047 cm–1.
– MS (EI, 70 eV): m/z ϭ 438 [M – 5 CO]ϩ. – C21H14CrN2O7Sn
(577.92): calcd. C 43.60, H 2.44, N 4.85; found C 43.71, H 2.50,
N 4.90.
Procedure 2: A solution of Cr(CO)6 (0.33 g, 1.50 mmol) in THF
(30 mL) was irradiated for 1.5 h. The solution was then purged of
CO by passing a stream of nitrogen through it for 15 min., and
then a suspension of (salen)Ge (0.51 g, 1.50 mmol) in THF (20 mL)
was added. Complex 4 (0.65 g, 83%) was obtained following the
same work-up procedure as outlined above; m.p. 280–285 °C
Synthesis of (salen)Pb؍Cr(CO)5 (6): To a suspension of (sa-
len)Pb[15b] (0.15 g, 0.32 mmol) in THF (30 mL) a solution of
(dec.). – 1H NMR (CDCl3): δ ϭ 3.90 (m, 4 H, CH2), 6.50–7.80 (m, Cr(CO)5 THF (0.09 g, 0.32 mmol) in THF (20 mL) was added
8 H, Ar), 8.32 (s, 2 H, CHϭN). – 13C NMR (CDCl3): δ ϭ 59.83 dropwise. The reaction mixture was stirred at room temperature for
(CH2), 117.03 (CHAr), 118.60 (Cq), 118.78 (CHAr), 131.60 (CHAr), 1 h and then the solvent was evaporated under reduced pressure.
132.49 (CHAr), 161.08 (Cq–O), 167.88 (CHϭN), 217.08 (CϭO The residual maroon-orange solid was washed with pentane and
1
trans), 218.41 (CϭO), 222.47 (CϭO), 224.62 (CϭO). – IR (Nujol, dried to afford 6 (0.15 g, 70%); m.p. Ͼ 300 °C (dec.). – H NMR
Eur. J. Inorg. Chem. 2000, 693Ϫ702
699

D. Agustin, G. Rima, H. Gornitzka, J. Barrau
FULL PAPER
([D6]DMSO): δ ϭ 3.80 (m, 4 H, CH2), 6.20–7.40 (m, 8 H, Ar), 8.24
Ar), 8.17 (s, 2 H, CHϭN). – 13C NMR (CDCl3): δ ϭ 59.79 (CH2),
(s, 2 H, CHϭN). – IR (Nujol, KBr): νCϭN 1620; νCO 1915, 1976, 117.00 (CHAr), 116.43 (Cq), 117.10 (CHAr), 131.55 (CHAr), 132.45
2048 cm–1. – C21H14CrN2O7Pb (665.99): calcd. C 37.84, H 2.12, N (CHAr), 160.91 (Cq–O), 166.56 (CHϭN), 196.08 (CϭO), 196.38
4.21; found C 38.01, H 2.20, N 4.03.
(CϭO). – IR (Nujol, KBr): νCϭN 1620; νCO 1892, 1980, 2009, 2060
cm–1. – MS (EI, 70 eV): m/z ϭ 608 [M – Ge(salen) – 2 CO]ϩ, 522
[M – Ge(salen) – 5 CO]ϩ. – C36H28Ge2N4O8W (975.98): calcd. C
44.26, H 2.89, N 5.74; found C 44.50, H 2.95, N 5.68.
Synthesis of (salen)Ge؍W(CO)5 (7): A solution of W(CO)5 THF
(0.15 g, 0.35 mmol) in THF (30 mL) was added dropwise to a sus-
pension of (salen)Ge (0.12 g, 0.35 mmol) in THF (20 mL) and the
resulting mixture was stirred at room temperature for 1 h. The solv-
ent was then removed in vacuo and the residual orange solid was
washed with pentane. Filtration of the washings and drying of the
collected solid gave 7 (0.22 g, 92%) in the form of orange crystals;
m.p. 260–270 °C (dec.). – 1H NMR (CDCl3): δ ϭ 3.93 (m, 4 H,
CH2), 6.72–7.60 (m, 8 H, Ar), 8.25 (s, 2 H, CHϭN). – 13C NMR
(CDCl3): δ ϭ 57.25 (CH2), 57.40 (CH2), 118.74 (CHAr), 121.00
(CHAr), 131.87 (CHAr), 133.11 (CHAr), 134.70 (CHAr), 135.22
(CHAr), 138.29 (CHAr), 139.85 (CHAr), 160.92 (Cq–O), 167.98
(CHϭN), 168.78 (CHϭN), 196.37 (CϭO), 198.92 (CϭO). – IR
(Nujol, KBr): νCϭN 1620; νCO 1916, 1972, 2067 cm–1. – MS (EI,
70 eV): m/z ϭ 662 [Mϩ ], 634 [M – CO]ϩ, 608 [M – 2 CO]ϩ, 580
[M – 3 CO]ϩ, 522 [M – 5 CO]ϩ. – C21H14GeN2O7W (663.95): calcd.
C 37.95, H 2.13, N 4.22; found C 38.20, H 2.29, N 4.10.
Synthesis of [(salen)Sn]2؍W(CO)4 (11). – Procedure 1: A mixture
of (salen)Sn (0.27 g, 0.70 mmol) and W(CO)6 (0.25 g, 0.70 mmol)
in THF (50 mL) was irradiated for 3 h, during which a red-maroon
color developed. The volatiles were then removed in vacuo and the
crude product was washed with pentane and dried to afford a mix-
ture of 11 (90%*) and 8 (10%*) as a yellow-orange powder (* relat-
1
ive % as determined by H-NMR).
Procedure 2: A mixture of (salen)Sn (0.27 g, 0.70 mmol) and
W(CO)6 (0.13 g, 0.35 mmol) in THF (50 mL) was irradiated for
3 h, during which the solution turned pale-orange. After removal
of the solvent, the crude product was washed with pentane and
dried to afford pure 11 (0.69 g, 92%) as an orange powder.
Procedure 3: A mixture of (salen)Sn (0.55 g, 1.40 mmol) and
W(CO)6 (0.26 g, 0.70 mmol) in THF (50 mL) was irradiated for
4 h, during which the solution again turned pale-orange. After re-
moval of the solvent, the crude product was washed with pentane
and dried to afford an orange powder consisting of a 30:70 cis/
trans (11/11Ј) mixture, which was characterized by 1H-, 13C-, and
119Sn-NMR and IR spectroscopy.
Synthesis of (salen)Sn؍W(CO)5 (8): A suspension of (salen)Sn
(0.11 g, 0.28 mmol) in THF (20 mL) was added dropwise to a solu-
tion of W(CO)5 THF (0.12 g, 0.28 mmol) in the same solvent. The
reaction mixture was stirred for a further 30 min, during which an
orange color developed. The volatiles were then removed in vacuo
and the residual solid product was washed with pentane and puri-
fied by crystallization from chloroform to give 8 (0.18 g, 92%) in
the form of yellow crystals; m.p. 280–285 °C (dec.). – 1H NMR
([D6]DMSO): δ ϭ 3.99 (m, 4 H, CH2), 6.70–7.00 (m, 8 H, Ar), 8.73
(s, 2 H, CHϭN). – 13C NMR ([D6]DMSO): δ ϭ 52.71 (CH2),
117.75 (CHAr), 118.87 (Cq), 122.32 (CHAr), 134.55 (CHAr), 135.83
(CHAr), 165.50 (Cq–O), 166.99 (CHϭN), 197.06 (CϭO), 201.16
Procedure 4: As Procedure 2, but after irradiation for 8 h, a 50:50
mixture of 11/11Ј was obtained from (salen)Sn (0.55 g, 1.40 mmol)
and W(CO)6 (0.26 g, 0.70 mmol).
Procedure 5: According to the previous procedure, pure 11 was ob-
tained from (salen)Sn (0.27 g, 0.70 mmol) and
8 (0.49 g,
0.70 mmol); yield: 0.67 g, 90%. Crystallization from CHCl3 gave
11 3 (CHCl3) as orange crystals.
(CϭO). – 119Sn{1H} NMR ([D6]DMSO): δ ϭ –328 (2JSn–W
1458 Hz). – IR (Nujol, KBr): νCϭN 1641; νCO 1913, 1977, 2063
cm–1. 5 CO]ϩ.
MS (EI, 70 eV): m/z 568 [M
ϭ
11 (cis): m.p. 250–260 °C (dec.). – 1H NMR ([D6]DMSO): δ ϭ 3.78
(s, 4 H, CH2), 6.50–7.50 (m, 16 H, Ar), 8.43 (s, 2 H, CHϭN). –
13C NMR ([D6]DMSO): δ ϭ 52.50 (CH2), 116.94 (CHAr), 118.96
(Cq), 122.17 (CHAr), 134.37 (CHAr), 135.37 (CHAr), 165.69 (Cq–
O), 169.32 (CHϭN), 202.19 (CϭO), 207.30 (CϭO). – 119Sn{1H}
NMR ([D6]DMSO): δ ϭ –348 (2JSn–W ϭ 1456 Hz). – IR (Nujol,
KBr): νCϭN 1638; νCO 1902, 1929, 1954, 2062 cm–1. – MS (EI,
70 eV): m/z ϭ 568 [(salen)SnWϩ]. – C36H28N4O8Sn2W (1067.94):
calcd. C 40.45, H 2.64, N 5.24; found C 40.61, H 2.72, N 5.14.
–
ϭ
–
–
C21H14N2O7SnW (709.93): calcd. C 35.50, H 1.99, N 3.94; found
C 35.70, H 2.12, N 4.00.
Synthesis of (salen)Pb؍W(CO)5 (9): In a similar manner, reaction
of (salen)Pb (0.15 g, 0.32 mmol) with W(CO)5 THF (0.13 g,
0.32 mmol) afforded 9 (0.20 g, 79%); m.p. Ͼ 300 °C (dec.). – 1H
NMR ([D6]DMSO): δ ϭ 3.87 (s, 4 H, CH2), 6.30–7.30 (m, 8 H,
Ar), 8.27 (s, 2 H, CHϭN). – IR (Nujol, KBr): νCϭN 1630; νCO
1914, 1970, 2060 cm–1. – C21H14N2O7PbW (798.00): calcd. C 31.58,
H 1.77, N 3.51; found C 31.64, H 1.92, N 3.30.
1
11Ј (trans): H NMR ([D6]DMSO): δ ϭ 3.82 (s, 4 H, CH2), 6.30–
7.50 (m, 16 H, Ar), 8.19 (s, 2 H, CHϭN). – 13C NMR
([D6]DMSO): δ ϭ 51.96 (CH2), 115.97 (CHAr), 118.96 (Cq), 122.06
(CHAr), 131.56 (CHAr), 132.25 (CHAr), 134.17 (CHAr), 165.82 (Cq–
Synthesis of cis-[(salen)Ge]2؍W(CO)4 (10). – Procedure 1: A mix-
ture of (salen)Ge (0.12 g, 0.36 mmol) and W(CO)6 (0.13 g,
0.36 mmol) in THF (50 mL) was irradiated for 3 h, during which a
red-orange color developed. After removal of the solvent, the crude
product was washed with pentane and dried to afford a mixture of
10 (85%*) and 7 (15%*) as a red-maroon powder (* relative %).
O), 167.99 (CHϭN), 211.23 (CϭO).
–
119Sn{1H} NMR
([D6]DMSO): δ ϭ –374. – IR (Nujol, KBr): νCϭN 1640; νCO 1999
cm–1.
Synthesis of cis-[(salen)Pb]2؍W(CO)4 (12). – Procedure 1: A mix-
ture of (salen)Pb (0.15 g, 0.32 mmol) and W(CO)6 (0.11 g,
0.32 mmol) in THF (50 mL) was irradiated for 3 h, during which a
maroon color developed. After filtration, the volatiles were re-
moved under reduced pressure. The residue was washed with pent-
ane and dried in vacuo to afford a mixture of 12 (70%*) and 9
Procedure 2: A mixture of (salen)Ge (0.25 g, 0.73 mmol) and
W(CO)6 (0.13 g, 0.36 mmol) in THF (50 mL) was irradiated for
2.5 h, during which the solution became orange. After removal of
the solvent, the crude product was washed with pentane and dried
to afford pure 10 (0.65 g, 92%) as an orange powder.
1
(30%*) as a red-brown powder (* relative % as determined by H-
NMR).
Procedure 3: A mixture of 7 (0.48 g, 0.73 mmol) and (salen)Ge
(0.25 g, 0.73 mmol) in THF (50 mL) was irradiated for 4 h. After Procedure 2: A mixture of (salen)Pb (0.54 g, 1.14 mmol) and
removal of the solvent, the residue was washed with pentane, the W(CO)6 (0.20 g, 0.57 mmol) in THF (50 mL) was irradiated for
washings were filtered, and the collected solid was dried to give
2.5 h, during which the solution turned maroon. After work-up as
pure 10 (0.62 g, 87%) as orange powder; m.p. 230–240 °C (dec.). –
described in the previous procedure, 12 (0.51 g, 72%) was obtained
1H NMR (CDCl3): δ ϭ 3.93 (m, 8 H, CH2), 6.50–7.50 (m, 16 H, as an orange powder.
700
Eur. J. Inorg. Chem. 2000, 693Ϫ702

Transition Metal Complexes of (Schiff Base)Divalent Group 14 Element Species
FULL PAPER
Procedure 3: According to the previous procedure, pure 12 (0.42 g,
60%) was obtained from (salen)Pb (0.27 g, 0.57 mmol) and 9
(0.45 g, 0.57 mmol); m.p.
iles were subsequently removed under reduced pressure. The crude
product was washed with pentane and dried in vacuo to afford 14
Ͼ 300 °C (dec.). –
1H NMR (0.02 g, 85%)
([D6]DMSO): δ ϭ 4.07 (s, 4 H, CH2), 6.25–7.35 (m, 8 H, Ar), 8.03
(s, 2 H, CHϭN). – IR (Nujol, KBr): νCϭN 1625; νCO 1906, 1930,
2015, 2060 cm–1. – C36H28N4O8Pb2W (1244.09): calcd. C 34.72, H
2.27, N 4.50; found C 34.90, H 2.40, N 4.32.
Reaction of 7 with One Equivalent of DBQ: A mixture of 7 (0.05 g,
0.10 mmol) and DBQ (0.02 g, 0.10 mmol) was dissolved in CHCl3
(5 mL). The color of the solution immediately darkened and evolu-
tion of CO was observed. After stirring for 8 h, the volatiles were
removed in vacuo. The crude product was washed with pentane
and dried in vacuo to afford 10 (0.04 g, 82%).
Reactions of 4 and 7 with Iodine: To a solution of 4 (0.05 g,
0.10 mmol) or 7 (0.06 g, 0.10 mmol) in DMSO (10 mL) was added
iodine (0.03 g, 0.10 mmol). CO was immediately evolved and the
solution turned orange. The mixture was stirred at room temper-
ature for 3 h. Subsequent analysis by 1H- and 13C-NMR and by
mass spectroscopy revealed that (salen)GeI2 had been produ-
ced.[15b]
Reaction of 8 with One Equivalent of DBQ: A mixture of 8 (0.09 g,
0.12 mmol) and DBQ (0.03 g, 0.12 mmol) was dissolved in CHCl3
(5 mL). The solution immediately turned dark-red. The volatiles
were subsequently removed under reduced pressure and the crude
product was washed with pentane and dried in vacuo to afford 11
(0.05 g, 78%).
Reactions of 5 and 8 with Iodine: According to the same procedure
as above, reactions of 5 (0.06 g, 0.10 mmol) and 8 (0.07 g,
0.10 mmol) with iodine (0.03 g, 0.10 mmol) afforded (sa-
len)SnI2.[15b]
Reaction of 8 with Two Equivalents of DBQ: A mixture of 8 (0.09 g,
0.12 mmol) and DBQ (0.06 g, 0.24 mmol) was dissolved in CHCl3
(5 mL). The solution immediately turned intensely red. The volat-
iles were subsequently removed under reduced pressure. The crude
product was washed with pentane and dried in vacuo to afford a
Synthesis of cis-(salen)Sn؍W(CO)4(PPh3) (13): A solution of 8
(0.22 g, 0.31 mmol) and triphenylphosphane (0.08 g, 0.31 mmol) in
THF (30 mL) was irradiated for 1.5 h. The solvent was then re-
moved in vacuo affording a maroon-orange powder, which was
washed with pentane and dried under reduced pressure to give 13
(0.26 g, 90%); m.p. 250–260 °C (dec.). – 1H NMR ([D6]DMSO):
δ ϭ 3.77 (s, 4 H, CH2), 6.72–7.60 (m, 23 H, Ar), 8.44 (s, 2 H, CHϭ
N). – 13C NMR ([D6]DMSO): δ ϭ 57.95 (CH2), 122.37 (CHAr),
124.33 (Cq), 127.62 (CHAr), 134.18 (CHAr), 134.40 (CHAr), 134.48
(CHAr), 137.41 (CHAr), 137.91 (CHAr), 139.82 (CHAr), 140.80
(CHAr), 171.16 (Cq–O), 174.77 (CHϭN), 202.34 (CϭO), 202.53
(CϭO), 207.64 (CϭO), 212.74. – 119Sn{1H} NMR ([D6]DMSO):
1
mixture of 11 and 16 (ratio 1:2, as determined by H-NMR).
Reaction of 8 with Four Equivalents of DBQ: A mixture of 8 (0.09 g,
0.12 mmol) and DBQ (0.12 g, 0.48 mmol) was dissolved in CHCl3
(10 mL). The solution immediately turned red. The volatiles were
subsequently removed in vacuo. The crude product was washed
with pentane and dried in vacuo to afford 16 (0.06 g, 83%)
Reaction of 4 with DBQ: A mixture of 4 (0.03 g, 0.05 mmol) and
DBQ (0.01 g, 0.05 mmol) was dissolved in CHCl3 (5 mL). The
color of the solution immediately darkened and the volatiles were
subsequently removed in vacuo. The crude product was washed
with pentane and dried in vacuo to afford 15. – 1H NMR (CDCl3):
δ ϭ 4.21 (m, 4 H, CH2), 6.40–7.70 (m, 10 H, Ar), 8.40 (s, 2 H,
CHϭN). – 13C NMR (CDCl3): δ ϭ 54.50 (CH2), 119.09 (CHAr),
120.89 (CqAr), 120.13 (CHAr), 134.03 (CHAr), 136.54 (CHAr),
164.20 (Cq–O), 161.81 (Cq–O), 172.2 (CHϭN), 211.70 (CO cis),
217.23 (CO). – C36H28N4O8Ge2Cr (843.97): calcd. C 51.19, H 3.34,
N 6.64; found C 51.40, H 3.51, N 6.23.
3
δ ϭ –347.5 (d, JSn–P ϭ 2088 Hz). – 31P{1H} NMR ([D6]DMSO):
δ ϭ –16.2 (3JSn–Pϭ 2088 Hz). – IR (Nujol, KBr): νCϭN 1639; νCO
1876, 1977, 2011, 2055 cm–1. – MS (EI, 70 eV): m/z ϭ 502
[Ph3PW(CO)2]ϩ,
446
[Ph3PW]ϩ,
386
[(salen)Sn]ϩ
.
–
C38H29N2O6PSnW (944.03): calcd. C 48.30, H 3.10, N 2.97; found
C 48.70, H 3.30, N 2.90.
Reaction of 5 with 1,2-Bis(diphenylphosphanyl)ethane: A solution of
5 (0.22 g, 0.38 mmol) in THF (30 mL) containing 1,2-bis(diphenyl-
phosphanyl)ethane (0.15 g, 0.38 mmol) was irradiated for 2.5 h.
The solvent was then removed in vacuo, affording a maroon-orange
powder, which was washed with pentane and dried under reduced
pressure to give a mixture of 14 and (DPPE)Cr(CO)4. The product
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NMR (CDCl3): δ ϭ 3.99 (m, 4 H, CH2), 6.60–7.50 (m, 10 H, Ar),
8.10 (s, 2 H, CHϭN). – 13C NMR (CDCl3): δ ϭ 48.70 (CH2),
118.56 (CHAr), 119.22 (CqAr), 123.98 (CHAr), 134.37 (CHAr),
136.64 (CHAr), 164.03 (Cq–O), 166.66 (Cq–O), 170.12 (CHϭN),
211.68 (CO cis), 218.43 (CO cis), 224.99 (CO trans). – 119Sn{1H}
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1931, 1982, 2052 cm–1. – C36H28CrN4O8Sn2 (935.93): calcd. C
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