Bimetallic bridged dppb {dppb=Ph2P (CH }2 (μ-dppb) ](M=MoW) : X-ray crystal structure of [{MoI2 (CO) 3 (P(O i Pr ) 3) } (μ-dppb)]

Article abstract of DOI:10.1016/S0277-5387(98)00293-9

Reaction of [MI₂ (CO) ₃ (NCMe) ₂] with one equivalent of P (OR) ₃ in CH₂Cl₂ at room temperaturefollowed by the in situ addition of half a molar equivalent of dppb {dppb=Ph₂P (CH₂) ₄PPh₂} gave the bimetallic complexes [{MI₂ (CO) ₃ (P (OR) ₃) }₂ (μ-dppb) ] (M=MoWR=MeEtⁱ Prⁿ Bufor M=W onlyR=Ph) (1→9) in good yield The molybdenum complex [{MoI₂ (CO) ₃ (P (Oⁱ Pr) ₃) }₂ (μ-dppb) ] (5) was crystallographically characterised and has crystallographic C₂ symmetry Each molybdenum has a capped octahedral environment with P (Oⁱ Pr) ₃ in the capping positionthree carbonyls in the capped face and the phosphorus from the bridging dppb ligand together with two iodines in the uncapped face.1998 Elsevier Science Ltd. All rights reserved.

Full text of DOI:10.1016/S0277-5387(98)00293-9

\
Polyhedron 07 "0888# 146Ð150
PERGAMON
Bimetallic bridged dppb "dppbꢀPh1P"CH1#3PPh1# complexes
ð"MI1"CO#2"P"OR#2##1"m!dppb#Ł "MꢀMo\ W#] X!ray crystal
structure of ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł
Paul K[ Bakera\ ꢁ\ Latifah Abdol Latifa\ b\ Margaret M[ Meehana\ Sabrina Zanina\
Michael G[ B[ Drewc
a Department of Chemistry\ University of Wales\ Bangor\ Gwynedd LL46 1UW\ U[K[
b Centre for Foundation Studies in Science\ University of Malaya\ 49592\ Kuala Lumpur\ Malaysia
c Department of Chemistry\ University of Reading\ Whiteknights\ Reading RG5 5AD\ U[K[
Received 4 June 0887^ accepted 11 July 0887
Abstract
Reaction of ðMI1"CO#2"NCMe#1Ł with one equivalent of P"OR#2 in CH1Cl1 at room temperature\ followed by the in situ addition
of half a molar equivalent of dppb "dppbꢀPh1P"CH1#3PPh1# gave the bimetallic complexes ð"MI1"CO#2"P"OR#2##1"m!dppb#Ł
"MꢀMo\ W\ RꢀMe\ Et\ iPr\ nBu^ for MꢀW only\ RꢀPh# "0:8# in good yield[ The molybdenum complex
ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł "4# was crystallographically characterised and has crystallographic C1 symmetry[ Each mol!
ybdenum has a capped octahedral environment with P"OiPr#2 in the capping position\ three carbonyls in the capped face and the
phosphorus from the bridging dppb ligand together with two iodines in the uncapped face[ Þ 0888 Elsevier Science Ltd[ All rights
reserved[
Keywords] Bimetallic phosphine!bridged^ Molybdenum"II#^ Tungsten"II#^ crystal structure
0[ Introduction
Ph1P"CH1#nPPh1 "nꢀ0\ 1\ 3#^ LÐLꢀðFe"h4!C4H3PPh1#1Ł#[
No X!ray crystal structures of these complexes were
obtained[ Very few phosphite seven!coordinate com!
plexes of molybdenum"II# and tungsten"II# have been
described^ two crystallographically characterised exam!
ples are ðMoCl"SnBuCl1#"CO#1"P"OMe#2#2Ł ð02Ł and
ðWBr1"CO#"P"OMe#2#1 "Me1AsC"CF2#1C"CF2# AsMe1#Ł
ð03Ł[ Phosphite ligands often help to increase the solu!
bility of complexes\ and enable suitable single crystals to
be grown for X!ray analysis[ In this paper\ we describe the
synthesis of the bimetallic phosphine!bridged phosphite
complexes ð"MI1"CO#2"P"OR#2##1"m!dppb#Ł "dppbꢀ
Bimetallic transition!metal complexes containing
bridging phosphines such as dppm "dppmꢀ
Ph1P"CH1#PPh1# have received considerable attention
over the years^ in particular by Shaw and co!workers
ð0Ð6Ł[ Although the zero!valent six!coordinate bimetallic
complexes ð"Mo"CO#4#1"m!Ph1P"CH1#nPPh1#Ł "nꢀ1\ 2#
have been prepared ð7Ł by the reaction of ðMo"CO#5Ł with
ONMe2 in the presence of Ph1P"CH1#nPPh1\ very little
work has been carried out on bimetallic phosphine!
bridged seven!coordinate complexes of molybdenum"II#
and tungsten"II#[
In 0875 ð8Ł\ we described the synthesis of the highly
versatile seven!coordinate complexes ðMI1"CO#2
"NCMe#1Ł "MꢀMo\ W#[ The complexes ðMI1 "CO#2"N!
CMe#1Ł have been shown to display a wide range of chem!
istry ð09\00Ł[ In 0880 ð01Ł\ we described the preparation
and characterisation of a series of phosphine!bridged
seven!coordinate complexes ð"MI1"CO#2L#1"m!LÐL#Ł
"MꢀMo\ W^ LꢀPPh2\ AsPh2\ SbPh2^ LÐLꢀ
i
n
Ph1P"CH1#3PPh1^ MꢀMo\ W\ RꢀMe\ Et\ Pr\ Bu^ for
MꢀW only\ RꢀPh#\ which has been crystallogra!
phically characterised for MꢀMo\ RꢀiPr[
1[ Experimental
All reactions described in this paper were carried out
under an atmosphere of dry nitrogen using standard vac!
uum:Schlenk line techniques[ The starting materials\
ðMI1"CO#2"NCMe#1Ł "MꢀMo\ W# were prepared by the
published method ð8Ł[ The solvents CH1Cl1 and diethyl
ꢁ Corresponding author[ Fax] ¦33!0137!26947[
9166!4276:88:, ! see front matter Þ 0888 Elsevier Science Ltd[ All rights reserved[
PII] S9166!4276 "87#99182!8

147
P[K[ Baker et al[ : Polyhedron 07 "0888# 146Ð150
Table 0
ether were dried and distilled before use[ All chemicals
were purchased from commercial sources[
Dimensions in the metal coordination sphere
bond lengths "A# and angles ">#
Ä
Elemental analyses "C\ H and N# were determined
using a Carlo Erba Elemental Analyser MOD 0097 "using
helium as a carrier gas#[ Infrared spectra were recorded
as thin CHCl2 _lms between NaCl plates on a Perkin!
Elmer 0599 series FTIR spectrophotometer[ 0H "ref!
erenced to SiMe3# and 20P "referenced to 74) H2PO3#
NMR spectra were recorded on a Bruker AC 149 NMR
spectrometer[
Mo"0#ÐC"199#
Mo"0#ÐC"299#
Mo"0#ÐC"099#
Mo"0#ÐP"3#
Mo"0#ÐP"2#
Mo"0#ÐI"0#
Mo"0#ÐI"1#
0[847 "08#
1[093 "05#
1[033 "08#
1[396 "4#
1[502 "4#
1[762 "2#
1[770 "2#
C"199#ÐMo"0#ÐC"299#
C"199#ÐMo"0#ÐC"099#
C"299#ÐMo"0#ÐC"099#
C"199#ÐMo"0#ÐP"3#
C"299#ÐMo"0#ÐP"3#
C"099#ÐMo"0#ÐP"3#
C"199#ÐMo"0#ÐP"2#
C"299#ÐMo"0#ÐP"2#
C"099#ÐMo"0#ÐP"2#
P"3#ÐMo"0#ÐP"2#
C"199#ÐMo"0#ÐI"0#
C"299#ÐMo"0#ÐI"0#
C"099#ÐMo"0#ÐI"0#
P"3#ÐMo"0#ÐI"0#
P"2#ÐMo"0#ÐI"0#
C"199#ÐMo"0#ÐI"1#
C"299#ÐMo"0#ÐI"1#
C"099#ÐMo"0#ÐI"1#
P"3#ÐMo"0#ÐI"1#
P"2#ÐMo"0#ÐI"1#
I"0#ÐMo"0#ÐI"1#
001[3 "6#
000[3 "6#
001[2 "6#
69[8 "5#
63[4 "4#
63[1 "4#
66[2 "4#
059[8 "4#
65[8 "4#
013[44 "05#
059[4 "4#
66[9 "4#
1[0[ Preparations
1[0[0[ ð"MoI1"CO#2"P"OMe#2##1"m!dppb#Ł "0#
To a solution of ðMoI1"CO#2"NCMe#1Ł "9[499 g\
9[858 mmol# in CH1Cl1 "29 cm2# was added P"OMe#2
"9[019 g\ 9[858 mmol# with continuous stirring under a
stream of dry nitrogen[ The dark brown solution immedi!
ately changed to yellowish green[ After 0 min of stirring\
dppb "9[196 g\ 9[374 mmol# was added and the mixture
was further stirred for 0 h[ Filtration\ and removal of
most of the solvent in vacuo\ followed by a dropwise
addition of Et1O gave a yellowish green complex[ After
cooling the mixture at −4>C for 61 h\ the solid upon
recrystallisation from CH1Cl1ÐEt1O "79]19# yielded
ð"MoI1"CO#2"P"OMe#2##1"m!dppb#Ł "0# "9[727 g\ 45)#[
Similar reactions of ðMI1"CO#2"NCMe#1Ł with an equi!
molar amount of P"OR#2 in CH1Cl1\ followed by an in
situ reaction with half an equivalent of dppb gives the
bimetallic complexes ð"MI1"CO#2"P"OR#2##1"m!dppb#Ł
"MꢀMo\ W\ RꢀEt\ iPr\ nBu^ MꢀW only\ RꢀMe\ Ph#
"1:8#[ Suitable single crystals for X!ray crystallography
of ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł "4# were grown by
cooling a CH1Cl1]Et1O 79]19 solution of "4# at −4>C for
61 h[ See Table 0 for physical and analytical data[
67[3 "4#
017[47 "05#
78[00 "00#
67[8 "4#
62[7 "4#
052[9 "4#
011[56 "03#
81[84 "02#
77[90 "7#
valent to 0[1 times those of the atom to which they were
attached[ There was one water solvent molecule for which
the hydrogen atoms could not be located and were not
included and one benzene solvent molecule with a crys!
tallographic centre of symmetry[ An empirical absorption
correction was carried out using the DIFABS program
ð06Ł[ The structure was then re_ned using Shelxl ð07Ł[ All
calculations were carried out on a Silicon Graphics R3999
Workstation at the University of Reading[ The _nal R
values were R0ꢀ9[9461\ and wR1ꢀ9[0093 for 0848 data
with I×1s"I#[
1[1[ X!ray crystallography
Crystals of ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł "4# were
grown as described in Section 1[0[ Bond lengths and
angles for the metal coordination spheres of 4 are given
in Table 0[ Crystal data for 4] C47H79I3Mo1O03P3\
Mꢀ0713[47\ Mo Ka radiation\ monoclinic\ space group
2[ Results and discussion
Ä
C1:c\ aꢀ39[41"3#\ bꢀ09[358"01#\ cꢀ19[65"1# A\
2
−2
Ä
bꢀ82[52"0#>\ Uꢀ7675 A \ Zꢀ3\ dmꢀ0[268 Mg m
\
The complexes ðMI1"CO#2"NCMe#1Ł "MꢀMo\ W# ð8Ł
were prepared by re~uxing ðM"CO#5Ł in NCMe to give
fac!ðM"CO#2"NCMe#2Ł ð08Ł\ followed by an in situ
addition of one equivalent of I1 at 9>C[ Treatment of
ðMI1"CO#2"NCMe#1Ł with an equimolar amount of
P"OR#2 in CH1Cl1 at room temperature gave
ðMI1"CO#2"NCMe#"P"OR#2#Ł\ which react in situ with
half an equivalent of dppb to give high yields of the
bimetallic complexes ð"MI1"CO#2"P"OR#2##1"m!dppb#Ł
"MꢀMo\ W^ RꢀMe\ Et\ iPr\ nBu^ MꢀW\ RꢀPh# "0:
8#[ Complexes 0:8 have been characterised by elemental
mꢀ0[798 mm−0\ F"999#ꢀ2473[ 8560 re~ections were col!
lected of which 5039 were unique\ R"int#ꢀ9[9469[ Data
were collected using the MARresearch Image Plate
System[ The crystal was positioned at 69 mm from the
Image Plate[ 84 frames were measured at 1> intervals with
a counting time of 1 min[ Data analysis was carried out
with the XDS program ð04Ł[ The structure was solved
using direct methods with the Shelx75 program ð05Ł[ The
non!hydrogen atoms were re_ned with anisotropic ther!
mal parameters[ The hydrogen atoms were included in
geometric positions and given thermal parameters equi!
analysis "C\ H and N# "Table 1#\ IR\ H and 20P NMR
0

P[K[ Baker et al[ : Polyhedron 07 "0888# 146Ð150
148
Table 1
Physical and analytical dataa for ð"MI1"CO#2"P"OR#2##1"m!dppb#Ł complexes
Complex
Yield ")# Colour
C ")#
H ")#
0 ð"MoI1"CO#2"P"OMe#2##1"m!dppb#Ł
1 ð"WI1"CO#2"P"OMe#2##1"m!dppb#Ł
2 ð"MoI1"CO#2"P"OEt#2##1"m!dppb#Ł=CH1Cl1
3 ð"WI1"CO#2"P"OEt#2##1"m!dppb#Ł
4 ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł
5 ð"WI1"CO#2"P"OiPr#2##1"m!dppb#Ł
6 ð"MoI1"CO#2"P"OnBu#2##1"m!dppb#Ł
7 ð"WI1"CO#2"P"OnBu#2##1"m!dppb#Ł
8 ð"WI1"CO#2"P"OPh#2##1"m!dppb#Ł=CH1Cl1
45
42
50
52
67
79
40
70
59
yellow:green
yellow
green:brown
yellow:green
brown
yellow
green:yellow
yellow
20[5 "20[0#
17[4 "17[9#
22[8 "23[9#
29[8 "29[6#
26[0 "25[4#
22[9 "22[0#
28[9 "27[6#
24[6 "24[3#
28[4 "28[1#
2[1 "2[9#
1[8 "1[6#
2[6 "2[5#
2[2 "2[1#
3[6 "3[0#
2[7 "2[6#
3[7 "3[5#
3[2 "2[8#
2[0 "1[7#
yellow
a Calculated values in parentheses[
spectroscopy "Table 2Table 3#\ and for MꢀMo\ RꢀiPr
by X!ray crystallography[ Complexes 2 and 8 were con!
_rmed as CH1Cl1 solvates by repeated elemental analyses
example\ the IR spectrum "CHCl2# of the crys!
tallographically characterised complex ð"MoI1"CO#2"P"O
iPr2#1##1"m!dppb#Ł "4# showed three carbonyl bands at
n"CO#ꢀ1922 "w#\ 0865 "s# and 0839 "s#\ which agrees the
structure for 4 shown in Fig[ 0[ The complex has two
identical molybdenum"II# centres bridged by a bis"di!
phenylphosphino#butane molecule\ with three carbonyl
ligands in a capped face in a capped octahedral structure[
As expected all of the very similar new complexes 0Ð8
have three carbonyl stretching bands in their IR spectra
with both similar patterns and stretching frequencies to
each other[ Suitable single crystals for X!ray crys!
tallography were grown by cooling a CH1Cl1]Et1O "79]19#
solution of 4 at −4>C for 61 h[
0
and H NMR spectroscopy[ The complexes are all very
soluble in CHCl2 and CH1Cl1\ and reasonably soluble in
diethyl ether[ They are considerably more soluble than
the closely related complexes ð"MI1"CO#2L#1"m!LÐL#Ł
"MꢀMo\
W^
LꢀPPh2\
AsPh2\
SbPh2^
LÐ
LꢀPh1P"CH1#nPPh1 "nꢀ0\ 1\ 3#^ LÐLꢀðFe"h4!
C4H3PPh1#1Ł# which have been previously described ð01Ł[
Complexes 0:8 are inde_nitely stable in the solid state
when stored under nitrogen\ but decompose in solution
when exposed to air[
The IR spectra of complexes 0:8 all show three car!
bonyl bands which suggests that the molybdenum centre
has the same arrangement of ligands\ this has been con!
_rmed by growing suitable single crystals for X!ray analy!
sis of ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł "4#[ For
The molecular structure of 4 is shown in Fig[ 0\ tog!
ether with the atomic numbering scheme[ The structure
consist of discrete ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł
dinuclear units with crystallographically imposed C1 sym!
Fig[ 0[ The structure of ð"MoI1"CO#2"P"OiPr#2##1"m!dppb#Ł "4# with ellipsoids at 29) probability[

159
P[K[ Baker et al[ : Polyhedron 07 "0888# 146Ð150

P[K[ Baker et al[ : Polyhedron 07 "0888# 146Ð150
150
Table 3
20P Ð"0H# NMR data "d#a for the complexes ð"MI1"CO#2"P"OR#2##1"m!dppb#Ł
Complex
20P "d#"ppm#:J"Hz#
0
1
2
3
4
5
6
7
8
060[72 "d\ P"OMe#2#^ 5[98 "d\ Ph1P"CH1#3PPh1#^ JWPꢀ201
025[25 "br\ P"OMe#2#^ JWPꢀ105^ −05[30 "br\ Ph1P"CH1#3PPh1#^ JWPꢀ250
052[69 "br\ P"OEt#2#^ 5[89 "d\ Ph1P"CH1#3PPh1#\ 1JPPꢀ13[7
016[71 "br\ P"OEt#2#^ −04[42 "br\ Ph1P"CH1#3PPh1#
045[31 "d\ P"OiPr#2#\ 1JPPꢀ14[3^ 6[22 "d\ Ph1P"CH1#3PPh1#
008[50 "d\ P"OiPr#2#\ JWPꢀ119\ 1JPPꢀ13[3^ −04[07 "d\ Ph1P"CH1#3PPh1#\ JWPꢀ036
052[64 "br\ P"OnBu#2#^ 6[92 "d\ Ph1P"CH1#3PPh1#\ 1JPPꢀ13[3
016[54 "br\ P"OnBu2##\ JWPꢀ178^ −04[21 "br\ Ph1P"CH1#3PPh1#
015[29 "br\ P"OPh#2#^ −06[61 "br\ Ph1P"CH1#3PPh1#
a Spectra recorded in CDCl2 "¦14>C# and referenced to 74) H2PO3^ brꢀbroad\ dꢀdoublet[
metry[ As is apparent in Fig[ 0\ the butane link is con!
sistently trans[ The environment of each molybdenum
atom "dimensions given in Table 0# is capped octahedral
with the phosphite in the capped position "MoÐP 1[396"4#
Award# and the University of Malaya for other _nancial
support and leave[ S[Z[ thanks the ERASMUS scheme
for support[ We also thank the EPSRC and the Uni!
versity of Reading for funds for the Image Plate System\
and A[ W[ Johans for his assistance with the crys!
tallographic investigations[
Ä
A#\ three carbonyls in the capped face "0[85"1#\ −1[03"1#
Ä
A# and the phosphorus from the bridging dppb ligand in
Ä
the uncapped face "MoÐP"3# 1[502"4# A#\ together with
Ä
two iodides "MoÐI"0# 1[762"2#\ MoÐI"1# 1[770"2# A#[
0
The H and 20P NMR spectra for 0:8 also suggest
the presence of a single isomer in solution\ and conform
with structure for 4 shown in Fig[ 0[ The 0H NMR data
Table 2\ have as expected all the ligand proton resonances
slightly shifted down_eld compared to the uncoordinated
ligands[ The symmetrical nature of the bridging dppb
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ð01Ł Baker PK\ van Kampen M\ ap Kendrick D[ J[ Organomet[ Chem[
0880^310]130[
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ð03Ł Mihichuk L\ Pizzey M\ Robertson B\ Barton R[ Can[ J[ Chem[
0875^53]880[
ð04Ł Kabsch W[ J[ Appl[ Cryst[ 0877^10]805[
ð05Ł Sheldrick GM[ Shelx75[ Acta Cryst[ A 0889^35]356[
ð06Ł Walker N\ Stuart D[ Acta Cryst[ A 0872^28]047[
ð07Ł Sheldrick GM[ Shelxl\ Program for Crystal Structure Re_nement\
0
ligand is also con_rmed in the H NMR spectra of 0Ð8\
all of which show the CH1 groups next to the phosphorus
atoms to be equivalent and the inner pair of CH1 groups
are also found to be equivalent[ The 20P"0H# NMR spec!
tra of 0Ð8 Table 3 also agree with the symmetrical struc!
ture of complex 4[ For example\ the crystallographically
characterised complex 4 has two resonances in its 20P
NMR spectrum[ One at dꢀ045[31 ppm due to the equi!
valent phosphite ligands\ which is split into a doublet by
the equivalent PPh1 groups on the dppb ligand\ with a
1
coupling constant of JPPꢀ14[3 Hz[ Similarly\ the res!
onance for 4 at dꢀ6[22 ppm due to the equivalent PPh1
groups on the dppb ligand\ also a doublet with an ident!
0
ical coupling constant[ In summary\ the IR\ H and 20P
NMR data con_rms the symmetrical structure as shown
for complex 4\ and it is very likely that complexes 0Ð3
and 5Ð8 have similar structures to complex 4[ We are
currently exploring the catalytic activity of 0:8 as alkene
metathesis catalysts[
ꢂ
ꢂ
Acknowledgements
L[A[L[ thanks the British Council for providing her
with a Research Attachment Award "British Chevening
University of Gottingen\ 0882[
ð08Ł Tate DP\ Knipple WR\ Augl JM[ Inorg[ Chem[ 0851^0]322[
Ã