Synthesis and structure of bis(thiomethyl)magnesium compounds [Mg(CH2SR)2(thf)3] (R = Me, Ph) - the first dimethylmagnesium compounds functionalized by a Lewis-basic heteroatom

Article abstract of DOI:10.1016/S0277-5387(98)00106-5

Hg(CH₂SR)₂, (R = Me (1), R = Ph (2)), prepared by reaction of HgCl₂ with [Li₂(CH₂SR)₂(tmeda)₂], reacts with magnesium activated by mercury in boiling THF to give [Mg(CH₂SR)₂(thf)₃] (R = Me (3), R = Ph (4)). 3 readily splitts off THF in vacuo to give the solvate free complex [Mg(CH₂SMe)₂] (3′). The complexes 3′ and 4 are fully characterized by microanalysis and NMR spectroscopy (¹H, ¹³C). The X-ray structure analyses of 3 and 4 reveal mononuclear compounds with two symmetry independent molecules in the unit cell of 3. In both complexes the coordination of Mg is trigonal-bipyramidal. The two apical positions are occupied by THF and the three equatorial positions by one THF and the two thiomethyl ligands. The C-Mg-C angles are slightly greater (123.9(1)-131.0(2)°) than the ideal angle for equatorial atoms in a trigonal-bipyramidal coordination. In neither case, the sulfur atoms are involved in the coordination of Mg.

Full text of DOI:10.1016/S0277-5387(98)00106-5

Polyhedron Vol[ 06\ No[ 08\ pp[ 2164Ð2179\ 0887
Þ 0887 Elsevier Science Ltd
Pergamon
All rights reserved[ Printed in Great Britain
9166Ð4276:87 ,08[99¦9[99
\
PII] SS916Ð6427"68#79909Ð54
Synthesis and structure of
bis"thiomethyl#magnesium compounds
ðMg"CH1SR#1"thf#2Ł "R ꢀ Me\ Ph# ! the _rst
dimethylmagnesium compounds functionalized by
a Lewis!basic heteroatom
Dirk Steinborn\ꢀ Tobias Ru}er\ Clemens Bruhn and Frank W[ Heinemann
Ã
Institut fur Anorganische Chemie der Martin!Luther!Universitat HalleÐWittenberg\
Ã
Ã
Kurt!Mothes!Str[ 1\ D!95019 Halle "Saale#\ Germany
"Received 15 November 0886^ accepted 5 March 0887#
Abstract*Hg"CH1SR#1\ "R ꢁ Me "0#\ R ꢁ Ph "1##\ prepared by reaction of HgCl1 with ðLi1"CH1SR#1"tmeda#1Ł\
reacts with magnesium activated by mercury in boiling THF to give ðMg"CH1SR#1"thf#2Ł "R ꢁ Me "2#\ R ꢁ Ph
"3##[ 2 readily splitts o} THF in vacuo to give the solvate free complex ðMg"CH1SMe#1Ł "2?#[ The complexes 2?
and 3 are fully characterized by microanalysis and NMR spectroscopy "0H\ 02C#[
The X!ray structure analyses of 2 and 3 reveal mononuclear compounds with two symmetry independent
molecules in the unit cell of 2[ In both complexes the coordination of Mg is trigonalÐbipyramidal[ The two
apical positions are occupied by THF and the three equatorial positions by one THF and the two thiomethyl
ligands[ The CÐMgÐC angles are slightly greater "012[8"0#Ð020[9"1#># than the ideal angle for equatorial atoms
in a trigonalÐbipyramidal coordination[ In neither case\ the sulfur atoms are involved in the coordination of
Mg[ Þ 0887 Elsevier Science Ltd[ All rights reserved[
Keywords] thiomethyl magnesium compounds^ functionalized methyl magnesium compounds^ mercury!
magnesium transmetallation^ crystal structures[
———————————————————————————————————————————————
INTRODUCTION
ring "YRn ꢁ SPh ð4Ł\ NPh1 ð6Ł#[ Monomeric com!
pounds are not known at all[
The very low thermal stability "Tdec[ ³ −099>C# and
the carbenoid reactivity of Kobrich|s "halogeno#!
Ã
Compared to the numerous lithium compounds A\
there are far fewer examples of functionalized methyl
Grignard compounds Mg"CH1YRn#X "B# with Lewis!
basic heteroatoms Y "YRn ꢁ OR\ SR\ X# ð1\ 8\ 09Ł[
To date\ there have been no reports of functionalized
dimethyl magnesium compounds Mg"CH1YRn#1 "C#[
Although a lot of structures of organomagnesium
compounds had been described ð00Ł\ those of type B
and C are not known at all[
We report here the synthesis of thiomethyl mag!
nesium compounds ðMg"CH1SR#1"thf#2Ł "R ꢁ Me "2#\
R ꢁ Ph "3## and their solid state structures being the
_rst compounds of type C[
methyl lithium compounds ð0Ł had exhibited\ that a
Lewis!basic heteroatom may strongly in~uence the
reactivity and stability of functionalized methyl lith!
ium compounds[ Since then\ the in~uence of Lewis!
basic heteroatoms Y on structure\ reactivity and sta!
bility of organolithium complexes of the type LiCH1
YRn "A# "YRnꢁNR1\ PR1\ OR\ SR\ Cl\ [ [ [# has been
investigated thoroughly ð1\ 2Ł[ X!ray structure inves!
tigations reveal a wide variety of solid state structures
exhibiting a coordination Y : Li in most cases ð3Ł[
The THF adducts\ ðLi"CH1YRn#"thf#xŁ are polymeric
"YRn ꢁ SMe ð4Ł\ PPh1 ð5Ł#\ tetrameric "YRn ꢁ NC4H09
ð6Ł\ NMe1 ð7Ł# or dimeric with a four!membered Li1C1
RESULTS AND DISCUSSION
The thiomethyl mercury complexes Hg"CH1SR#1
ꢀ Author to whom correspondence should be addressed[
"R ꢁ Me "0#\ R ꢁ Ph "1## were prepared by the reac!
2164

2165
D[ Steinborn et al[
The thiomethyl magnesium complexes 2 and 3 are
tion of HgCl1 with ðLi1"CH1SR#1"tmeda#1Ł in THF\ cf[
Equation "0#[ The identities of 0 and 1 were con_rmed very sensitive against air and moisture[ The "methyl!
by microanalysis and NMR spectroscopy "0H and thio#methyl complex 2 loses the coordinated THF
02C#[ In the case of the complex 1 these values agree very easily in vacuo to give the solvate free complex
with the data given in the literature ð01Ł[
ðMg"CH1SMe#1Ł "2?#[ 2 and 3 are well soluble in THF
The organomercury compounds 0 and 1 undergo and ether and insoluble in aromatic and aliphatic
with magnesium in boiling THF a transmetallation hydrocarbons[ The identities of 2? and 3 were con!
reaction yielding the bis"thiomethyl#magnesium com! _rmed by microanalysis and NMR spectroscopy "0H
plexes ðMg"CH1SR#1"thf#2Ł "R ꢁ Me "2#\ R ꢁ Ph "3## and 02C#[
that precipitate from the concentrated solutions at
−39>C as well shaped colorless crystals\ eq[ "0#[
Table 0 shows the resonances of the methylene
group in 2\ 3 and in related lithium complexes[ Com!
pared with their lithium analogues\ the 0H resonances
of 2 and 3 are shifted down_eld because of the mag!
nesium is less electropositive[ The di}erence
Dd"0H# ꢁ 9[19 ppm between 2 and 3 should be caused
by the electronic e}ect of the phenyl substituent[ As
in the "phenylthio#methyl lithium compounds\ there
is an unusual high _eld shift of the methylene carbon
"0#
0
in 3[ The coupling constants J"02C\0H# for the CH1
groups of all compounds in Table 0 are in the expected
range exhibiting no unusual bonding relationships[
Structures of ðMg"CH1SMe#1"thf#2Ł "2# and ðMg"CH1
There is an induction period of several hours[ Acti! SPh#1"thf#2Ł "3#
vating the magnesium with one drop of mercury\ the
reactions take not more than three hours "degree of
The molecular structures of complexes 2 and 3
conversion ×89)#[ The transmetallation of 1 with along with the atom numbering schemes are shown in
magnesium was proved to proceed also in boiling Figs 0 and 1[ Selected bond lengths and angles are
toluene and xylene with mercury activated magnesium listed in Table 1[
"degree of conversion ×79)#[ Within eight hours no
reaction was observed in boiling ether\ not even with without any unusal intermolecular interactions[ The
magnesium activated by mercury[ unit cell of complex 2 contains two symmetry inde!
The two structures consist of monomeric molecules
For HgÐMg transmetallation reactions\ a wide pendent molecules "2 and 2a#^ one of them "2a# exhi!
range of reactivity was described in the literature] bits a crystallographically imposed C1 symmetry[
Me1Hg was found to react with magnesium immedi! Related bond lengths of 2 and 2a di}er less than 0)
ately in a strong exothermic reaction ð02Ł[ On the while related bond angles show noteable di}erences
other hand\ transmetallation reactions of aryl mercury "up to 4Ð5)#[
compounds take up to two weeks in THF at room
Both in 2 and in 3\ the magnesium displays a dis!
temperature ð03Ł[ An activation of the HgÐMg trans! torted trigonalÐbipyramidal coordination[ As usual
metallation with HgCl1 was observed ð04Ł\ but the for trigonalÐbipyramidal structures ð07Ł\ the more
isolation of R1Mg in a pure state might be di.cult electronegative ligands "THF# occupy the apical po!
due to the Schlenk equilibrium[
sitions[ These MgÐO bonds are longer than that to the
Table 0[ 0H and 02C NMR resonances "in ppm# and 0J"02C\ 0H# coupling constants
"in Hz# of the methylene group in thiomethyl magnesium and lithium complexes
Compounda
d"0H#
d"02C#
0J"02C\ 0H#
Ref[
b
b
c
ðMg"CH1SMe#1"thf#2Ł "2#
ðMg"CH1SPh#1"thf#2Ł "3#
ðLi1"CH1SMe#1"tmeda#1Ł
ðLi1"CH1SPh#1"tmeda#1Ł
ð"Li"CH1SMe#"thf##ꢀŁ
ðLi1"CH1SPh#1"thf#3Ł
9[55
9[75
9[27
9[25
9[25
9[20
01[8
3[8
04[2
3[0
03[7
2[7
010[2
010[6
005[3
010[9
005[9
010[9
c
ð4Ł
ð4Ł
aFormulae refer to aggregation in solid state[
bThis work[
cOwn measurements\ prepared according to the literature ð05\ 06Ł[

Synthesis and structure of bis"thiomethyl#magnesium compounds ðMg"CH1SR#1"thf#2Ł
2166
Table 1[ Selected bond lengths "in Aý# and angles "in ># for
ðMg"CH1SR#1"thf#2Ł
2 "R ꢁ Me# 2a "R ꢁ Me#a 3 "R ꢁ Ph#
Mg0ÐC0
Mg0ÐC1
C0ÐS0
C1ÐS1
S0ÐC04
S1ÐC05
Mg0ÐO0
Mg0ÐO1
1[067"2#
1[080"2#
0[646"2#
0[669"2#
0[792"3#
0[700"3#
1[984"1#
1[067"1#
1[074"1#
012[8"0#
007[0"0#
007[9"0#
83[6"0#
84[0"0#
81[2"0#
82[4"0#
70[48"6#
70[72"6#
052[39"7#
004[0"1#
001[9"0#
095[3"1#
096[6"1#
1[085"2#
0[664"2#
0[700"2#
1[057"5#
1[084"5#
0[666"5#
0[656"5#
0[655"4#
0[662"5#
1[976"3#
1[125"3#
1[039"3#
017[3"2#
009[7"1#
019[3"1#
89[5"1#
1[096"1#
1[078"1#
Mg0ÐO2
C0ÐMg0ÐC1
C0ÐMg0ÐO0
C1ÐMg0ÐO0
C0ÐMg0ÐO1
C1ÐMg0ÐO2
C0ÐMg0ÐO2
C1ÐMg0ÐO1
O0ÐMg0ÐO1
O0ÐMg0ÐO2
O1ÐMg0ÐO2
Mg0ÐC0ÐS0
Mg0ÐC1ÐS1
C0ÐS0ÐC04
C1ÐS1ÐC05
020[9"1#b
003[38"6#
80[51"8#
81[58"8#c
73[68"5#
82[8"1#
86[1"1#
80[0"1#
70[3"1#
73[1"1#
058[5"0#d
000[6"0#
054[1"1#
002[8"2#
003[5"2#
097[3"2#
097[8"2#
096[9"1#
aSymmetry transformations used to generate equivalent
atoms] |] −x\ y\ −z¦0:1[
bC0aÐMg0aÐC0?[
cC0aÐMg0aÐO1?[
dO1aÐMg0aÐO1?[
The MgÐC bond lengths in 2 and 3 "d"MgÐ
C# ꢁ 1[057"5#Ð1[085"2# Aý# are in the range for MgÐ
C bond lengths of other monomeric _ve!coordinate
dialkylmagnesium compounds such as ðMgR1
"pmdta#Ł ð08Ł "R ꢁ Me\ Et^ pmdta ꢁ N\N\N?\Ný\Ný!
pentamethyldiethylenetriamine# "d"MgÐC# ꢁ 1[047"4#Ð
1[112"8# Aý#[
Fig[ 0[ Molecular structure and numbering scheme of the
two crystallographically independent molecules 2 "above#
and 2a "below#[ To make the correspondence between them
clear\ the atoms are numbered in the same way\ but {a| was
added to independent atoms of 2a^ { | | refers to symmetry
related atoms of 2a[ Ellipsoids are drawn at 49) probability[
Hydrogen atoms are omitted for clarity[
The
CH1ÐS
distances
"d"CÐS# ꢁ 0[646"2#Ð
Ä
0[666"5# A# are substantially shorter than the SÐCH2
Ä
distances in 2 "d"CÐS# ꢁ 0[792"3#Ð0[700"3# A#[ They
are in the same range as the SÐCPh distances in 3 "d"CÐ
Ä
S# ꢁ 0[655"4# and 0[662"5# A# in spite of the smaller
covalent radii of sp1 hybridized carbons in comparison
equatorially bonded THF molecule "d"MgÐOap# ꢁ with sp2 hybridized ones ð07Ł[ This indicates a sta!
Ä
1[039"3#Ð1[125"3# A
vs[
d"MgÐOeq# ꢁ1[976"3#Ð bilizing in~uence on the carbanionoid centre of sulfur
Ä
1[096"1# A#[
The distortions of the coordination polyhedron
around Mg are relatively small] The angles OapÐMgÐ dimethylmagnesium complexes Mg"CH1YRn#1 with a
ap are between 052[39"7#> and 058[5"0#> and the sum Lewis!basic heteroatomic centre Y[ Unexpectedly\ the
by polarization[
The complexes 2 and 3 are the _rst functionalized
O
of angles in the equatorial planes is between 248[5"3#> sulfur is not involved in the coordination sphere of
and 259[9"1#>[ The less electronegative organo ligands magnesium[ Furthermore\ for the _rst time a trigonalÐ
are more space!demanding as can be seen at the widen! bipyramidal coordination around magnesium was
ing of the CÐMgÐC angles "012[8"0#Ð020[9"1#># and found with monodentate coligands L "ðMgR1L2Ł#[ To
at the lowering of the OapÐMgÐOeq angles "70[3"1#Ð date\ monomeric _ve!coordinate diorganomagnesium
73[68"5#>#[
compounds were observed only with tridentate co!

2167
D[ Steinborn et al[
Fig[ 1[ Molecular structure and numbering scheme of complex 3[ Ellipsoids are drawn at 49) probability[ Hydrogen atoms
are omitted for clarity[
ligands "ðMgR1L2Ł^ Rꢁalkyl\ aryl^ L2ꢁpmdta\ −67>C[ After stirring for 0 h and warming up to r[t[
diglyme\ tetraglyme# ð08\ 19Ł[ With mono! and oli! water "099 ml# was added[ The half of the solvent was
godentate coligands\ tetrahedral complexes ðMgR1L1Ł removed in vacuo and the colorless precipitate formed
"R ꢁ alkyl\
aryl^
L ꢁ THF\
quinuclidine^ was _ltered o}\ washed with water and cold methanol
L1 ꢁ TMEDA# ð08\ 10Ð15Ł and octahedral complexes and dried in vacuo[ Yields] 0 "4[5 g\ 64)#^ 1 "8[6 g\
ðMgR1L3Ł "R ꢁ alkyl\ alkynyl^ L1 ꢁ TMEDA\ 89)#[
L3 ꢁ crown ether# ð19\ 16Ð18Ł are formed[
Anal[ Calcd for 0] C\ 03[77^ H\ 2[01^ S\ 08[75[
Found] C\ 04[13^ H\ 2[19^ S\ 07[63[ 0H NMR
"499 MHz\
THF!d7#]
d
1[16
"s\
3H\
C
EXPERIMENTAL
1J"088Hg\ 0H# ꢁ 093[9 Hz\ CH1#\ 1[04 "s\ 5H\ CH2#[ 02
NMR "014 MHz\ THF!d7#]
d
32[0 "s¦d\
11[7 "s¦d\
General comments
0J"088Hg\ 02C# ꢁ 719[0 Hz\
CH1#\
2J"088Hg\ 02C# ꢁ 026[9 Hz\ CH2#[
All reactions and manipulations were carried out
under puri_ed argon using standard Schlenk tech!
niques[ n!Hexane\ n!pentane\ TMEDA and THF!d7
were dried with LiAlH3[ Toluene\ xylene\ THF and
diethyl ether were distilled from sodium benzo!
phenone ketyl[ NMR spectra were recorded on Varian
Unity 499 spectrometer using the protio impurities
and 02C resonances of the deuterated solvents as ref!
Anal[ Calcd for 1] C\ 26[51^ H\ 2[05^ S\ 03[24[
Found] C\ 27[02^ H\ 2[11^ S\ 03[97[ 0H NMR
"499 MHz\
THF!d7#]
d
1[59
"s\
3H\
1J"088Hg\ 0H# ꢁ 096[2 Hz\ CH1#\ 6[95Ð6[35 "m\ 09H\
Ph#[ 02C NMR "014 MHz\ THF!d7#] d 28[1 "s¦d\
0J"088Hg\ 02C# ꢁ 744[3 Hz\ CH1#\ 013[8 "p!C#\ 014[8 "o!
C#\ 017[2 "m!C#\ 031[9 "i!C#[
0
erences for H and 02C NMR spectroscopy\ respec!
tively[ Microanalyses "C\ H\ S# were obtained from
the microanalytical laboratory of the Department of
Chemistry[ A CP8999 "Chrompack# was used for gas!
chromatographic analyses[ ðLi1"CH1SR#1"tmeda#1Ł
"R ꢁ Me\ Ph# was prepared according to the literature
ð05\ 06Ł[
Synthesis of ðMg"CH1SR#1"thf#2Ł "R ꢀ Me "2#\
R ꢀ Ph "3##
A mixture of Hg"CH1SR#1 "R ꢁ Me "0#\ R ꢁ Ph
"1## "2[3 mmol#\ powdered magnesium "9[64 g\
20 mmol# and mercury "about 9[0 g\ 9[4 mmol# in THF
"09 ml# was re~uxed under vigorous stirring for about
2 h[ The amalgam formed was _ltered o} and the
solution was concentrated in vacuo up to about 4 ml[
Synthesis of Hg"CH1SR#1 "R ꢀ Me "0#\ R ꢀ Ph "1##
To a solution of HgCl1 "5[4 g\ 13 mmol# in THF At −39>C\ 2 and 3 precipitated in well shaped crystals
"49 ml#\ ðLi1"CH1SR#1"tmeda#1Ł "RꢁMe\ Ph# which were _ltered o}\ washed with hexane and dried
"37 mmol# in THF "49 ml# was added dropwise at in vacuo[ Yield] 2? "9[2 g\ 59)#^ 3 "0[0 g\ 54)#[ To

Synthesis and structure of bis"thiomethyl#magnesium compounds ðMg"CH1SR#1"thf#2Ł
2168
Table 2[ Crystal data and structure re_nement for 2 and 3
2
3
Empirical formula
fw
C05H23MgO2S1
251[77
orthorhombic:P b c n
09[276"1#\ 06[102"2#\ 24[244"7#
C15H27MgO2S1
376[91
¹
Crystal system:space group
triclinic:P0
Ä
a\ b\ c "A#
8[452"1#\ 01[233"2#\ 01[799"3#
a\ b\ g "deg#
89\ 89\ 89
5210"1#
004[97"1#\ 87[27"3#\ 80[25"2#
0236[6"5#
V "Aý2#
Z
01
0[033
9[180
1265
1
Dcalcd "g cm−2
#
0[199
9[134
413
m"MoKa# "mm−0
F"999#
#
Scan range "deg#
Index ranges
1[16 ³ u ³ 13[95
−00 ¾ h ¾ 00\ −07 ¾ k ¾ 08\
−39 ¾ l ¾ 39
0[67 ³ u ³ 11[49
−09 ¾ h ¾ 09\ −02 ¾ k ¾ 02\
−02 ¾ l ¾ 02
Re~ections collected
14458
4889
Independent re~ections
Observed re~ections ðI × 1 s"I#Ł
Parameters re_ned
3784 "Rint ꢁ 9[0933#
2726
368
2415 "Rintꢁ9[0045#
0614
330
Goodness!of!_t on F1
0[977
0[903
Final R indices ðI × 1s"I#Ł
R indices "all data#
R0 ꢁ 9[9401\ wR1 ꢁ 9[0109a
R0ꢁ9[9558\ wR1 ꢁ 9[0299a
9[214 and −9[057
R0 ꢁ 9[9472\ wR1 ꢁ 9[9637b
R0ꢁ9[0528\ wR1 ꢁ 9[9887b
9[292 and −9[170
Largest di}[ peak and hole "e Aý!2#
aw ꢀ 0:ð"s1:F1o#¦"9[9612P#1¦0[8816PŁ^ P ꢀ "Fo1¦1F1c #:2[
bw ꢁ 0:ð"s1:F1o#[
determine the degree of conversion\ in separate experi! ð20Ł#[ Non!hydrogen atoms were re_ned with aniso!
ments MeOH:THF "0:3^ 9[4 ml# was added dropwise tropic displacement parameters[ The hydrogen atoms
at −67>C to the reaction mixture[ The yield of MeSR were found in the Fourier list and re_ned isotropically\
was determined by gaschromatography using naph! except of some in 2\ which were placed in calculated
thalene as internal standard[ Degree of conversion] 2 positions[ Crystal data\ details of data collections\
"THF\ 82)#\ 3 "THF\ 86)^ toluene\ 72)^ xylene\ structure solutions and re_nements are summarized
82)#[
in Table 2[ Complete tables of the atomic coordinates\
Anal[ Calcd for 2?] C\ 21[67^ H\ 5[77[ Found] C\ H!atom parameters\ bond distances\ bond angles and
0
22[19^ H\ 5\71[ H NMR "499 MHz\ THF!d7#] d 9[55 anisotropic displacement parameters atoms have been
"s\ 3H\ CH1#\ 0[78 "s\ 5H\ CH2#[ 02C NMR "014 MHz\ deposited with the Editor as supplementary material[
THF!d7#] d 01[8 "CH1#\ 16[1 "CH2#[
Anal[ Calcd for 3] C\ 53[01^ H\ 6[75[ Found] C\
52[27^ H\ 6[91[ H NMR "499 MHz\ THF!d7#] d 9[75
Acknowled`ements*T[ R[ thanks the Land Sachsen!Anhalt
for a scholarship[ We gratefully acknowledge support by
Deutsche Forschungsgemeinschaft and Fonds der Chemi!
schen Industrie as well as the company Merck "Darmstadt#
for gifts of chemicals[
0
"s\ 3H\ CH1#\ 5[68Ð5[80 "m\ 1H\ p!H#\ 6[94Ð6[97 "m\
3H\ m!H#\ 6[11Ð6[13 "m\ 3H\ o!H#[ 02C NMR
"014 MHz\ THF!d7#] d 3[8 "CH1#\ 011[3 "p!C#\ 017[2
"m!C#\ 013[0 "o!C#\ 040[7 "i!C#[ "Due to partial
hydrolysis a small amount ot MeSPh was detected in
the spectra[#
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