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Ir intensity measurements on group VIIIB, C metal-alkyne complexes
453
Journal of OrganometaZIic Cfremisfry, 131 (1977) 453-465 @ EIsevier Sequoia S.A., Lausanne -Printed in The Netherlands
IR RVTENSITY _MEASUREMENTS ON GROUP C METAL-ALKYNE COMPLEXES
H.L.M. van Gk4L ’ Department Netherlands)
VIIIB,
=*, M.W.M. GRAEF a,b and A. van der ENT ’
of Inorganic Chemistry, Catholic University, Toernooiveld, b Unilever Research, Olivier van Noortlaan 120, Vlaardingen
Nijmegen (The (The Netherlands)
(Received November 3rd, 1976)
Summary
The integrated molar absorption coefficients Atilt of the C-C stretching-vibration of the coordinated alkynes of Rh, Ir, Ni and Pt complexes of hexafluorobutyne (HFB), tolane and hexyne have been measured. A relative scale of donor and acceptor interactions in the complexes has been calculated from the measured values of Kti, and A(v’) = v’(free alkyne) - Y’(coordinated alkyne). Competitive as well as synergic relations between donor and acceptor bonding have been found. The order of increasing donor and decreasing acceptor bonding has been found for the alkynes HFB + tolane + hexyne. Within the series of complexes of a given alkyne, the acceptor bond increases for the metals in the order: Pt(I1) (4) < Rh(1) (4) < Ir(1) (4) < Pt(I1) (5) < Ni(0) (3) < Pt(0) (3) (coordination number in parentheses) and the donor bonding increases synergically with the acceptor bonding in this series. Introduction The by the a bond empty +-orbit&
transition metal-alkyne bond has a dual nature and is usually described Dewar, Chatt, Duncanson bonding model [1,2] as being composed of (i) of o-symmetry, in which the alkyne donates n-electron density to the metal orbitals, and (ii) a bond of ;T-symmetry, in which the antibonding of the alkyne
accept
electron
density
from
filled
metal
orbitals
(z-
backbonding), In addition, there may be a contribution from the second n.and 7r* orbital pair. Both donor and acceptor bonding weaken the coordinated C=C bond and lower the C=C stretching vibration frequency. The GC stretching vibration of a coordinated alkyne is accompanied by a change in dipole moment which is perpendicular to t.he vibrational motion along the metalqlkyne bond. The change in the permanent dipole moment, due to the movements of the nuclear coordinates during the CZC stretching vibration, is not likely to be of great importance, since this symmetric vibration consists
455
TABLE
1
ANALYTICAL
DATA
Compound
values are given in puentbeses)
Atiysis
i c Pt(PPh3)2(HFB) Ni(PPh3)2(HFB) P~(CH~)WBPZ~)WFB) LrCl(PPh$z(HFB) RhCl(PPh32
H
N
Cl
P
55.0
3.7
6.9
(55.5) 64.3 (64.6) 29.6 (28.7) 52.1
(3.4) 3.9
(7.0) 8.5
(4.1) 2.4 (2.2) 3.3
(52.8) 58.8 (58.3) 66.5 (66.9) 67.7 (68.5) 64.7 (64.5) 70.6 (71.4) 61.2 (62.9) 63.7 (64.7) --___
(8.2) 14.6 (14.4)
(3.3) 3.9 (4.1) 4.4
(Z)
12.5 (12.9) 15.2 (15.4) 17.0 (19.6) 12.5 (12.5) 13.1 (13.8)
.
7.2
(4.5) 8.2
3.7
(8.8) 4.5
(4.0) 3.7
(4.3) 4.6 (4.8) 4.8
(3.3) 3.7 (i-2)
(5-O) 9.6 (9.8)
F
(6.9)
6.8 (6.7)
8.0 3.6 (3.5)
(7.8) 8.3 (8.0)
peak, which we attribute to Fermi resonance doubling [23]. In those cases the total intensity of both absorptions has been taken. Results
The IR vibration under consideration is acceptably described by a 5-center model of Czu-symmetry, comprising the central metal, the two acetyienic carbon atoms and the two substituent atom groups (Fig. 1). From the seven fundamental in-plane vibrations, four belong to the A 1representation. With the aid of tabulated G-mat& elements 1241 and estimated force constants 125,261 it is confirmed that contributions of the lower frequency vibrations to the commonly called CEC stretching vibration in the 1700-2000 cm-’ region do not exceed IO%, so that approximation by a pure CS! stretching vibration does not introduce large errors. The integrated molar absorption coefficient &, is defined as 1271: .A& = IZdzJ = 2.303(1/U)
$
log(&,/I,)dv
(1)
band
its dimension is I mol-’ cm-‘. A - 1s _ the molar absorption coefficient in 1 mol-’ cm-’ ;C is the concentration in mol I-’ and L isthe cell width in cm. Table 2 gives, together with some other IR data, the measured values of Xtit, with the
%
_....._ ___._ .._..........._. _._._...__-.. ” Pt(PP11~)2(111~~13)
et”
._..
140
449 39G
138
376 36G 330
24 18
20 20 26 IG 19
370
467
lb
441
22 19 17 14.5 13
527 599 430
.._-___.____ .._. --__.r,.._._--I-.._-..___--
2247 1798 1941 195G(!Jl) 2101
2,222 1742 1768 la47 lab7 ia85 1898 2007
1773 1791 1aa2 lR33 1009 1903 1921
2300
O.GO(4) 0.42(S) c
O.BB(Q) 0.70(5) O&1(2)
1.31(10)
-___.___.______l____l
181 128 a4
C&I. 0.0
GA
1113 149 130
la0
180
0.3G 0.29
cn. 0.0
0.42 0.40 0.3a
O.B2
O.G7
172 0.04
2.00(6) l&1(7)
216 208 la2 0;77 0.07
4(r;‘L) (lo4 cm+) -..---_.__._
3,22(O) 298(a) 2.31(7) OS1
(n.u,) _ ___l_.--.___
wm)cnl~
-..---_.-.--I-.- ...... ..._.._ _..____ _I.__ ..-...__-_-.-.._..,._.._
CL1. 0.0
0.191 0.146
0.277 0.277 0.24G 0.387 0.14B 0.171 cn. 0.0
1.216 1.150 0,74c 0,402 9.990 0.647 0.822
AIJ(C-:C) Amex x 10-3 &t x 10-4 (6 10112 (1 mol”t cm-t) (cm-() (cm”) (1 mol-* cm-l) ._____. .._. ,_.___...- . . .._._.._-.- ....- _.__.. -._,____... _...__. - -._..._._.-___.___-..
I1 In Knrnanspccttum. 5; Date from ref. a. ’ KhCl(YCY3)p(CO) absorpa stronab st 1947 cm- * , A trncc amount of this comyound, trltltouglrnot detcctcd tn tha 31P &MR rind 1R spectru, muy be mwent. This may hrcrcssc the mcnsurcd value of jimt ol KhCI(PCy3)2(KEX).
__.- __.____._________._.___.___
~Pt(C~I3)(Ao~le3)~(Tot)lr
rthCL(PCY3)$rOL) irCI(PPh3)~(TOL) ILhCI(PPh~)#wL)
l’t(i’Ph~)~(TOL)
Dfphcn;f”cdy/ene a
Ni(PPh~)2(IlF’U) el(Cs3)(~rnPx~)(~rI~u)
~7~.raflrroroblrfyrlr’
___~._
. DIPOLE MOMENT CIIANGKS OF ALKYNE COMPLEX&S
(cm-l)
u(Cqq
IR INTKNSITY DATA AND CALCULATED
l)i.nm
Journal of OrganometaZIic Cfremisfry, 131 (1977) 453-465 @ EIsevier Sequoia S.A., Lausanne -Printed in The Netherlands
IR RVTENSITY _MEASUREMENTS ON GROUP C METAL-ALKYNE COMPLEXES
H.L.M. van Gk4L ’ Department Netherlands)
VIIIB,
=*, M.W.M. GRAEF a,b and A. van der ENT ’
of Inorganic Chemistry, Catholic University, Toernooiveld, b Unilever Research, Olivier van Noortlaan 120, Vlaardingen
Nijmegen (The (The Netherlands)
(Received November 3rd, 1976)
Summary
The integrated molar absorption coefficients Atilt of the C-C stretching-vibration of the coordinated alkynes of Rh, Ir, Ni and Pt complexes of hexafluorobutyne (HFB), tolane and hexyne have been measured. A relative scale of donor and acceptor interactions in the complexes has been calculated from the measured values of Kti, and A(v’) = v’(free alkyne) - Y’(coordinated alkyne). Competitive as well as synergic relations between donor and acceptor bonding have been found. The order of increasing donor and decreasing acceptor bonding has been found for the alkynes HFB + tolane + hexyne. Within the series of complexes of a given alkyne, the acceptor bond increases for the metals in the order: Pt(I1) (4) < Rh(1) (4) < Ir(1) (4) < Pt(I1) (5) < Ni(0) (3) < Pt(0) (3) (coordination number in parentheses) and the donor bonding increases synergically with the acceptor bonding in this series. Introduction The by the a bond empty +-orbit&
transition metal-alkyne bond has a dual nature and is usually described Dewar, Chatt, Duncanson bonding model [1,2] as being composed of (i) of o-symmetry, in which the alkyne donates n-electron density to the metal orbitals, and (ii) a bond of ;T-symmetry, in which the antibonding of the alkyne
accept
electron
density
from
filled
metal
orbitals
(z-
backbonding), In addition, there may be a contribution from the second n.and 7r* orbital pair. Both donor and acceptor bonding weaken the coordinated C=C bond and lower the C=C stretching vibration frequency. The GC stretching vibration of a coordinated alkyne is accompanied by a change in dipole moment which is perpendicular to t.he vibrational motion along the metalqlkyne bond. The change in the permanent dipole moment, due to the movements of the nuclear coordinates during the CZC stretching vibration, is not likely to be of great importance, since this symmetric vibration consists
455
TABLE
1
ANALYTICAL
DATA
Compound
values are given in puentbeses)
Atiysis
i c Pt(PPh3)2(HFB) Ni(PPh3)2(HFB) P~(CH~)WBPZ~)WFB) LrCl(PPh$z(HFB) RhCl(PPh32
H
N
Cl
P
55.0
3.7
6.9
(55.5) 64.3 (64.6) 29.6 (28.7) 52.1
(3.4) 3.9
(7.0) 8.5
(4.1) 2.4 (2.2) 3.3
(52.8) 58.8 (58.3) 66.5 (66.9) 67.7 (68.5) 64.7 (64.5) 70.6 (71.4) 61.2 (62.9) 63.7 (64.7) --___
(8.2) 14.6 (14.4)
(3.3) 3.9 (4.1) 4.4
(Z)
12.5 (12.9) 15.2 (15.4) 17.0 (19.6) 12.5 (12.5) 13.1 (13.8)
.
7.2
(4.5) 8.2
3.7
(8.8) 4.5
(4.0) 3.7
(4.3) 4.6 (4.8) 4.8
(3.3) 3.7 (i-2)
(5-O) 9.6 (9.8)
F
(6.9)
6.8 (6.7)
8.0 3.6 (3.5)
(7.8) 8.3 (8.0)
peak, which we attribute to Fermi resonance doubling [23]. In those cases the total intensity of both absorptions has been taken. Results
The IR vibration under consideration is acceptably described by a 5-center model of Czu-symmetry, comprising the central metal, the two acetyienic carbon atoms and the two substituent atom groups (Fig. 1). From the seven fundamental in-plane vibrations, four belong to the A 1representation. With the aid of tabulated G-mat& elements 1241 and estimated force constants 125,261 it is confirmed that contributions of the lower frequency vibrations to the commonly called CEC stretching vibration in the 1700-2000 cm-’ region do not exceed IO%, so that approximation by a pure CS! stretching vibration does not introduce large errors. The integrated molar absorption coefficient &, is defined as 1271: .A& = IZdzJ = 2.303(1/U)
$
log(&,/I,)dv
(1)
band
its dimension is I mol-’ cm-‘. A - 1s _ the molar absorption coefficient in 1 mol-’ cm-’ ;C is the concentration in mol I-’ and L isthe cell width in cm. Table 2 gives, together with some other IR data, the measured values of Xtit, with the
%
_....._ ___._ .._..........._. _._._...__-.. ” Pt(PP11~)2(111~~13)
et”
._..
140
449 39G
138
376 36G 330
24 18
20 20 26 IG 19
370
467
lb
441
22 19 17 14.5 13
527 599 430
.._-___.____ .._. --__.r,.._._--I-.._-..___--
2247 1798 1941 195G(!Jl) 2101
2,222 1742 1768 la47 lab7 ia85 1898 2007
1773 1791 1aa2 lR33 1009 1903 1921
2300
O.GO(4) 0.42(S) c
O.BB(Q) 0.70(5) O&1(2)
1.31(10)
-___.___.______l____l
181 128 a4
C&I. 0.0
GA
1113 149 130
la0
180
0.3G 0.29
cn. 0.0
0.42 0.40 0.3a
O.B2
O.G7
172 0.04
2.00(6) l&1(7)
216 208 la2 0;77 0.07
4(r;‘L) (lo4 cm+) -..---_.__._
3,22(O) 298(a) 2.31(7) OS1
(n.u,) _ ___l_.--.___
wm)cnl~
-..---_.-.--I-.- ...... ..._.._ _..____ _I.__ ..-...__-_-.-.._..,._.._
CL1. 0.0
0.191 0.146
0.277 0.277 0.24G 0.387 0.14B 0.171 cn. 0.0
1.216 1.150 0,74c 0,402 9.990 0.647 0.822
AIJ(C-:C) Amex x 10-3 &t x 10-4 (6 10112 (1 mol”t cm-t) (cm-() (cm”) (1 mol-* cm-l) ._____. .._. ,_.___...- . . .._._.._-.- ....- _.__.. -._,____... _...__. - -._..._._.-___.___-..
I1 In Knrnanspccttum. 5; Date from ref. a. ’ KhCl(YCY3)p(CO) absorpa stronab st 1947 cm- * , A trncc amount of this comyound, trltltouglrnot detcctcd tn tha 31P &MR rind 1R spectru, muy be mwent. This may hrcrcssc the mcnsurcd value of jimt ol KhCI(PCy3)2(KEX).
__.- __.____._________._.___.___
~Pt(C~I3)(Ao~le3)~(Tot)lr
rthCL(PCY3)$rOL) irCI(PPh3)~(TOL) ILhCI(PPh~)#wL)
l’t(i’Ph~)~(TOL)
Dfphcn;f”cdy/ene a
Ni(PPh~)2(IlF’U) el(Cs3)(~rnPx~)(~rI~u)
~7~.raflrroroblrfyrlr’
___~._
. DIPOLE MOMENT CIIANGKS OF ALKYNE COMPLEX&S
(cm-l)
u(Cqq
IR INTKNSITY DATA AND CALCULATED
l)i.nm