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Non planar coordination in a Cu++ complex
Non planar coordination in a Cu +÷ complex EDOARDO FRASSON, ROBERTO ZANNETTL RENATO BARDI SILVIO BEZZI, GIOVANNI GIACOMETTI C e n t r o dl s t r u t t u r i s t / c a C h l n d c a del C N R - P a d o v a - I t a l i a
I S u ~ From the refined strttotura of the Cu-dinmth/lgIyoxime i t is evident t h a t t h e t w o r i n p i n the moiseule do not lie in the s a ~ plam~ f o r m h t ~ a n anlile of a bout 28. betwe~. The structure is therefore very d l f f e m t from the struetm~ of the ~ l n ~ Nicompannd w~h, as G o d ~ d and nundle showod, has two eopkmsr r t n ~ The N i - m ~ o f f i ' b . ~ structure has very short H-bo~l llke other s ~ of the organic 4-covelant m e ~ p ~ I t is pointed ou t t h a t tim s t ~ of t he Metal-Nitrogen bonds, depending from the different Ni-Cu atomic radii, does not s t re t c h t h e H-bond or causes a variation In O N - M e angle, b u t p r o d u ~ s a distortion of the molecule and a loss of p l a n a r i t y of the four C u + + covalences. This p h ~ o m e l m does not happen in the Pd an d Pf complexes Isomorphous w i t h the Ni..complex. The /~f-Pt-dioffilm~ have the same s t r u c t m of the nlchel-dioxime also ff these nmtsls have t he atomio radii largm"
than Cu. On the other the structure of Cu-dimethilglyoxime is different from the structure of Pd, Na, PL-dioximes: in these later there is an octah~bral e o m ~ o a t i o n of t he ~ t he metal atoms beeing bonded each other:, in l h .~ former t he Cu-Cu bonds are n o t p e r m i t t e d by the steric interposition of t h e organic p e r t of t he mo/ecule. The pyramidal structure of the Cu+-]--compisx depends from t he dp s or 4/~p s - s ( I > n > O ) Ibridisation. W i t h such an ibridlmtion i t is possible a 15.40' shift from t he planar disposition of the orbitais and a bond force intermediate between t he planar a nd tetrahedral structures.
INTRODUCTION.
A few years ago Bezzi, Bua and Schiavinato [1] had given notice in a preliminary work of the crystallographic characteristics and of some structural characters of the complex Cu-dymethylglioxime, and later Godycki and Rundle [2] published the structure of Ni-dymethylglioxime. The X-ray researches have revealed very deep structural differences besides the crystallographic ones between the two substances. The Ni-dymethylglioxime belongs to the space group I b a m with 4 molecules in the elementary cell. The atom of Ni is localized in crystallographic symmetry centers, therefore the necessary derivation of the molecular centrosymmetry around Ni. Moreover the molecule rests perfectly parallel to the plane (001). The molecular impact is such to permit the existence of a bond Ni-Ni of 3,45 A between the metallic atoms belonging to the overset molecules.
NON PLANAR COORDINATION IN A CI/"4"'4" COMPLEX
453
The Cu-dymethylglioximc belongs to the space Group C,6~= P 21# with 4 molecules in the elementary cell and the atom of Cu is found in general positions. The existence of intermetallic bonds between Cu atoms is not possible, owing to the noticeable distance between them and the interposition between the overset molecules of the organic part of another molecules. The lack of an intermetallic bond in this structure accounts for the noticeable increased solubility of this complex in comparison to the one derivated from th~ Ni. We have taken into examination the structure of the Cu-dymethylglioxime in order to determine exactly the parameters of the molecule organic part. EXPERIMENTAL.
The results referred to in this comunication are drawn from examination of severs] crystals collected from different crystallizations and submitted to X ray diffraction, under normal temperature and also even submitted to a very low temperature, very close to the one of liquid air. The diffracted intensities linearly integrated in Weissenberg's camera, have been integrated in surface for photometric exploration of the diffraction and potentiometric registration. The crystal having also a low coefficient of absorbtion, it has been deemed necessary to correct the intensity by an absorbtion factor calculated with a graphic method. From the experimental data the electronic density projections have been obtained on the three fundamental plans of the unit cell which possesses the following dimensions: a =
9.72 A
b ~-~ 16.90 A c=
7.08k
---~ 71030' Owing to the noticeable overlapping of maximals due to different atoms in the maps of electronic density, the atomic coordinates have been determined by progressive closing by means of Fourier differences. The structure refinement has been brought up to a reliability index: R=
Z[tF, I--IF, I]
IF.[
By this deeper examination the result was that a new fundamental difference exists betweeb the two structures and also the placing of the
454
B . F R A S S O N , R . Z A N N R T T I # R . B A R D I , S. B E Z Z l ,
O. O I A C O M E T T I
organic part of the two complex regarding the metallic atom is different. The two organic rings which depart from the metallic atom are not any longer complanary in the Cu-dymethylglioxime in which the centro-symmetry of the molecule results destroyed. The plan of one of the two organic
J
o
b
L
Fze. 1. - C u - d f m e t h ¥ 1 1 l i y o x f m e : p r o | e e t f o u o n (001).
rings shows an angle of 23 ° with the plan of the other ring. On fig. 1. the electronic density" projection is show on plan (001). In order to represent it in a complete couple of molecules, the origin of the cell coinciding with a symmetry centre has been set at the centre of the figure itself. On fig. 2. a model molecule is shown. The right hand side of the molecule lies fundamentally parallel to the projection plan and therefore one can see the real bounding distances existing in the molecule itself. The other half of the molecule presents itself in a distorted and compressed position, this is due to the inclination respectively to its projection plan.
NON PLANAR COORDINATION IN A Cu + +
COMPLEX
455
F.z
t a 2'
Pse. ~L - Molecular s t r u e t u r e of c o p p e r - d i m e t h y l l ~ o x f m e : peoJeetJon on (001~ DISCUSSION.
The majority of the known up to date structures of Cu++-4-coordinste complexes show a noticeable preference of the straight disposition of the bonds, most implying of hybrid orbitals dsp s. Owing to the electronic structure of the Cu++ lone (3 do), use of such orbitals may result at a glance rather hortodox for the noticeable promoting energy necessary to take a 3d electron at a 4p level (about 420 Kcal/mole) and so deliver a orbital d for the coordinate groups bounding. Pauling [3] resolves the difficulty inferring that "There is, on the other hand, no loss fo energy by the copper atom caused by placing the unshared electron in the third 4p orbital and using the 3d orbital for bond formation, inasmuch as each of the five orbitals under discussion (one 3d, one 4s, three 4p) is occupied either by a shared pair or by the single unshared electron on either formulation (single electron i n 3d with sp s bonds or single electron in 4p with dsp s bonds), and the interaction energy of a shared pair with the copper atom is the same as that of a single unshared electron ".
456
~-. FRASSON, R. ZANNETTI, R. BARDI, S. BEZZI, G. GIACOMETTI
On this basis, copper prefers forming complexes of plan structure (orbitals strength 2,69) better than tetraedric (strengt 2,00). The case of complex with dymethylglioxime seemes to present an interesting intermediate position, as it refers to the orbital strength. To explain the pyramidal structure which was found we have to admit that hybridization should be of the type dp' or d s"p s - " (con 1 > n ~ o) in which use of the third orbital p projects all bonds towards direction 2. These orhitals are of the type --S-~ 2
- - P , + 2
-~
P,+
2-
d~,--¢
For a -- o (n -~ O) the orbital strength is 2,31 and the direction of the maximals is: ? ---- O, ~ -~ 74 ° 20 : [4]. The bonds get apart of plan • y of an angle of 15 ° 40' which is approximately the one found for our structure. One can see then, that by means of an hybridisation which, by the point of view of the promotional energy, is perfectly alike to the planar one, one can form a pyramidal structure in which the bonds strength is intermediate between the plan and the tetraedric structures. The reason by which in this structure one gets the pyramidal configuration is to be believed that it is tied to the fact that with it one realizes a shortening of about 0,1 4 in the bounding of hydrogen between the two atoms of oxygen. By thys opportunity we have to point out that Cu-salicylimine has instead a planar structure [5] and that besides the N i complex also the complexes Pd ad Pt with dymethyglioxime are planar, being atomic radius of these two last elements greater than those of Cu. REFERENCES [1] [2] IS] [4] [5]
Bzzzx S., BUA E., ~ W l A V m A T O G. • GaZZ. (]him. Ital. ,, 81, 856 (1951). GODVC~ L. E. R w m t ~ R. E. • Acta C.r~t ,, 6, 487 (1953). P A ~ @ L., • The Nature of t h e Chem. B o n d . , (Cornel Univ. Press. ,, 104 (1940). Sz~'r S. S n ~ r r F. • Anales Real Sue. Esp. Fis. of Quire. • A 47, 197 (1951). SmONSZN S. H., P ~ u o m ~ C. E. , Acta Crylt. ,, 10, 471 (1957~
DISCUSSIONS V U W l Z f ( 0 z t o r d ) - W h i c h is t h e r e l a t i v e p o s i t i o n o f t h e molecule of c o m p l e x in r e s p e c t t o t h e u n i t cell ? Is a n i n t e r a t i o n possible b e t w e e n a n o x y g e n of a molecule w i t h c o p p e r of a n o t h e r , so h a v i n g s o m e t h i n g - like a p e n t a c o o r d i n a t l o n ? F r a s s o n - E f f e c t i v e l y one gets a p e n t a c o o r d i n a t i o n , as e a c h Cu a t o m finds itself b e t w e e n two a t o m s of o x y g e n of different molecules r e s p e c t i v e l y a p a r t 2',40 A a n d 4,68 A. B y t h i s , one h a s . a c o u p l i n g of t h e molecules placed r o u n d t h e s i m m e t r y c e n t r e s (fig. I) w i t h t w o b o u n d l n g s Cu-O. T h e s t r u c t u r e of t h e C u - d y m e t h y l g l i o x i m e is t h e r e f o r e c h a r a c t e r i z e d b y t h e f o r m a t i o n of a d l m e r o , d i f f e r e n t l y to t h e N l - d y m e t h y l g l i o x i m e in w h i c h t h e b o n d N i - N i b r i n g s t o a s t r u c t u r e p o l l m e r e lineal t y p e ,.
NON PLANAR COORDINATION IN A Cu "l''j" COMPLEX
457
S c J ~ i t z D u l ~ f l t (Bern) - Die yon Herrn Frasson 8efundene n i c h t coplanare S t r u k t u r gilt wohl n u t fttr den festen Zustand oder k a n n man auch a n n e h m e n class sie lm gei6sten Zustand aueh besteht 7 Im letzteren Falle musste Methylitthylglyoxlm-kupfer In optlsche Antlpoden zu spaiten sein.
F t l t u o n - W i t denken dass das MolekQl auch In L6sung dieselbe Konflsuration behalten kann w~nn diese konfl~mration aus ether gtarken H,BrQcke s t a m m t . Aus keinem Grunde soil diese H - B i n d u n g in L6sung gebrochen werden. Ftlr was sich aug des Methyl-~thylglyoxim-kupfer bezieht, mt~chten wit bemerken das Methyl-gLthylglyoxim-kupfer isomorph dem Methylitthyiglyoxtm-nickei Jst (Cox E. G., S h a r r a t t E. Wardlaw W., Webster K. C. - J. Chem. Soc. (1936) 129), und dass dleser Komplex als planar, b e s t i m m t wurde (Mllone M., 10o Congr. Int. Chim. Boma, 2 (1938) 346). @ s p r l n ( F r a n k l u r t A . M . ) - Zuerst wird aug eine frOhere r o e n p n o g r a p h i s c h e Untersuehung yon Peeh, Polster, Regabek in Chemieki Listy augmerktam gemacht, die ebeugalls p zeigt h a t dass Cu-dlmethyl-g]yoxim Komplex nicht isomer ist m l t den entsprechender Komplexen yon N i , Pt, Pd. Wird p f r a g t ob aus der U n t e r s u c h u n g angenommen werden kann dass die Bindtmgen zwischen Cu u n d den vler N-Atomen in alien Fallen gleichartig angesehen werden k6nnen. FruNn wertig.
- Wie m a n aus dem Blld 2 sehen kann, sind die vJer Bindungen C u - N gleich-
I S u ~ From the refined strttotura of the Cu-dinmth/lgIyoxime i t is evident t h a t t h e t w o r i n p i n the moiseule do not lie in the s a ~ plam~ f o r m h t ~ a n anlile of a bout 28. betwe~. The structure is therefore very d l f f e m t from the struetm~ of the ~ l n ~ Nicompannd w~h, as G o d ~ d and nundle showod, has two eopkmsr r t n ~ The N i - m ~ o f f i ' b . ~ structure has very short H-bo~l llke other s ~ of the organic 4-covelant m e ~ p ~ I t is pointed ou t t h a t tim s t ~ of t he Metal-Nitrogen bonds, depending from the different Ni-Cu atomic radii, does not s t re t c h t h e H-bond or causes a variation In O N - M e angle, b u t p r o d u ~ s a distortion of the molecule and a loss of p l a n a r i t y of the four C u + + covalences. This p h ~ o m e l m does not happen in the Pd an d Pf complexes Isomorphous w i t h the Ni..complex. The /~f-Pt-dioffilm~ have the same s t r u c t m of the nlchel-dioxime also ff these nmtsls have t he atomio radii largm"
than Cu. On the other the structure of Cu-dimethilglyoxime is different from the structure of Pd, Na, PL-dioximes: in these later there is an octah~bral e o m ~ o a t i o n of t he ~ t he metal atoms beeing bonded each other:, in l h .~ former t he Cu-Cu bonds are n o t p e r m i t t e d by the steric interposition of t h e organic p e r t of t he mo/ecule. The pyramidal structure of the Cu+-]--compisx depends from t he dp s or 4/~p s - s ( I > n > O ) Ibridisation. W i t h such an ibridlmtion i t is possible a 15.40' shift from t he planar disposition of the orbitais and a bond force intermediate between t he planar a nd tetrahedral structures.
INTRODUCTION.
A few years ago Bezzi, Bua and Schiavinato [1] had given notice in a preliminary work of the crystallographic characteristics and of some structural characters of the complex Cu-dymethylglioxime, and later Godycki and Rundle [2] published the structure of Ni-dymethylglioxime. The X-ray researches have revealed very deep structural differences besides the crystallographic ones between the two substances. The Ni-dymethylglioxime belongs to the space group I b a m with 4 molecules in the elementary cell. The atom of Ni is localized in crystallographic symmetry centers, therefore the necessary derivation of the molecular centrosymmetry around Ni. Moreover the molecule rests perfectly parallel to the plane (001). The molecular impact is such to permit the existence of a bond Ni-Ni of 3,45 A between the metallic atoms belonging to the overset molecules.
NON PLANAR COORDINATION IN A CI/"4"'4" COMPLEX
453
The Cu-dymethylglioximc belongs to the space Group C,6~= P 21# with 4 molecules in the elementary cell and the atom of Cu is found in general positions. The existence of intermetallic bonds between Cu atoms is not possible, owing to the noticeable distance between them and the interposition between the overset molecules of the organic part of another molecules. The lack of an intermetallic bond in this structure accounts for the noticeable increased solubility of this complex in comparison to the one derivated from th~ Ni. We have taken into examination the structure of the Cu-dymethylglioxime in order to determine exactly the parameters of the molecule organic part. EXPERIMENTAL.
The results referred to in this comunication are drawn from examination of severs] crystals collected from different crystallizations and submitted to X ray diffraction, under normal temperature and also even submitted to a very low temperature, very close to the one of liquid air. The diffracted intensities linearly integrated in Weissenberg's camera, have been integrated in surface for photometric exploration of the diffraction and potentiometric registration. The crystal having also a low coefficient of absorbtion, it has been deemed necessary to correct the intensity by an absorbtion factor calculated with a graphic method. From the experimental data the electronic density projections have been obtained on the three fundamental plans of the unit cell which possesses the following dimensions: a =
9.72 A
b ~-~ 16.90 A c=
7.08k
---~ 71030' Owing to the noticeable overlapping of maximals due to different atoms in the maps of electronic density, the atomic coordinates have been determined by progressive closing by means of Fourier differences. The structure refinement has been brought up to a reliability index: R=
Z[tF, I--IF, I]
IF.[
By this deeper examination the result was that a new fundamental difference exists betweeb the two structures and also the placing of the
454
B . F R A S S O N , R . Z A N N R T T I # R . B A R D I , S. B E Z Z l ,
O. O I A C O M E T T I
organic part of the two complex regarding the metallic atom is different. The two organic rings which depart from the metallic atom are not any longer complanary in the Cu-dymethylglioxime in which the centro-symmetry of the molecule results destroyed. The plan of one of the two organic
J
o
b
L
Fze. 1. - C u - d f m e t h ¥ 1 1 l i y o x f m e : p r o | e e t f o u o n (001).
rings shows an angle of 23 ° with the plan of the other ring. On fig. 1. the electronic density" projection is show on plan (001). In order to represent it in a complete couple of molecules, the origin of the cell coinciding with a symmetry centre has been set at the centre of the figure itself. On fig. 2. a model molecule is shown. The right hand side of the molecule lies fundamentally parallel to the projection plan and therefore one can see the real bounding distances existing in the molecule itself. The other half of the molecule presents itself in a distorted and compressed position, this is due to the inclination respectively to its projection plan.
NON PLANAR COORDINATION IN A Cu + +
COMPLEX
455
F.z
t a 2'
Pse. ~L - Molecular s t r u e t u r e of c o p p e r - d i m e t h y l l ~ o x f m e : peoJeetJon on (001~ DISCUSSION.
The majority of the known up to date structures of Cu++-4-coordinste complexes show a noticeable preference of the straight disposition of the bonds, most implying of hybrid orbitals dsp s. Owing to the electronic structure of the Cu++ lone (3 do), use of such orbitals may result at a glance rather hortodox for the noticeable promoting energy necessary to take a 3d electron at a 4p level (about 420 Kcal/mole) and so deliver a orbital d for the coordinate groups bounding. Pauling [3] resolves the difficulty inferring that "There is, on the other hand, no loss fo energy by the copper atom caused by placing the unshared electron in the third 4p orbital and using the 3d orbital for bond formation, inasmuch as each of the five orbitals under discussion (one 3d, one 4s, three 4p) is occupied either by a shared pair or by the single unshared electron on either formulation (single electron i n 3d with sp s bonds or single electron in 4p with dsp s bonds), and the interaction energy of a shared pair with the copper atom is the same as that of a single unshared electron ".
456
~-. FRASSON, R. ZANNETTI, R. BARDI, S. BEZZI, G. GIACOMETTI
On this basis, copper prefers forming complexes of plan structure (orbitals strength 2,69) better than tetraedric (strengt 2,00). The case of complex with dymethylglioxime seemes to present an interesting intermediate position, as it refers to the orbital strength. To explain the pyramidal structure which was found we have to admit that hybridization should be of the type dp' or d s"p s - " (con 1 > n ~ o) in which use of the third orbital p projects all bonds towards direction 2. These orhitals are of the type --S-~ 2
- - P , + 2
-~
P,+
2-
d~,--¢
For a -- o (n -~ O) the orbital strength is 2,31 and the direction of the maximals is: ? ---- O, ~ -~ 74 ° 20 : [4]. The bonds get apart of plan • y of an angle of 15 ° 40' which is approximately the one found for our structure. One can see then, that by means of an hybridisation which, by the point of view of the promotional energy, is perfectly alike to the planar one, one can form a pyramidal structure in which the bonds strength is intermediate between the plan and the tetraedric structures. The reason by which in this structure one gets the pyramidal configuration is to be believed that it is tied to the fact that with it one realizes a shortening of about 0,1 4 in the bounding of hydrogen between the two atoms of oxygen. By thys opportunity we have to point out that Cu-salicylimine has instead a planar structure [5] and that besides the N i complex also the complexes Pd ad Pt with dymethyglioxime are planar, being atomic radius of these two last elements greater than those of Cu. REFERENCES [1] [2] IS] [4] [5]
Bzzzx S., BUA E., ~ W l A V m A T O G. • GaZZ. (]him. Ital. ,, 81, 856 (1951). GODVC~ L. E. R w m t ~ R. E. • Acta C.r~t ,, 6, 487 (1953). P A ~ @ L., • The Nature of t h e Chem. B o n d . , (Cornel Univ. Press. ,, 104 (1940). Sz~'r S. S n ~ r r F. • Anales Real Sue. Esp. Fis. of Quire. • A 47, 197 (1951). SmONSZN S. H., P ~ u o m ~ C. E. , Acta Crylt. ,, 10, 471 (1957~
DISCUSSIONS V U W l Z f ( 0 z t o r d ) - W h i c h is t h e r e l a t i v e p o s i t i o n o f t h e molecule of c o m p l e x in r e s p e c t t o t h e u n i t cell ? Is a n i n t e r a t i o n possible b e t w e e n a n o x y g e n of a molecule w i t h c o p p e r of a n o t h e r , so h a v i n g s o m e t h i n g - like a p e n t a c o o r d i n a t l o n ? F r a s s o n - E f f e c t i v e l y one gets a p e n t a c o o r d i n a t i o n , as e a c h Cu a t o m finds itself b e t w e e n two a t o m s of o x y g e n of different molecules r e s p e c t i v e l y a p a r t 2',40 A a n d 4,68 A. B y t h i s , one h a s . a c o u p l i n g of t h e molecules placed r o u n d t h e s i m m e t r y c e n t r e s (fig. I) w i t h t w o b o u n d l n g s Cu-O. T h e s t r u c t u r e of t h e C u - d y m e t h y l g l i o x i m e is t h e r e f o r e c h a r a c t e r i z e d b y t h e f o r m a t i o n of a d l m e r o , d i f f e r e n t l y to t h e N l - d y m e t h y l g l i o x i m e in w h i c h t h e b o n d N i - N i b r i n g s t o a s t r u c t u r e p o l l m e r e lineal t y p e ,.
NON PLANAR COORDINATION IN A Cu "l''j" COMPLEX
457
S c J ~ i t z D u l ~ f l t (Bern) - Die yon Herrn Frasson 8efundene n i c h t coplanare S t r u k t u r gilt wohl n u t fttr den festen Zustand oder k a n n man auch a n n e h m e n class sie lm gei6sten Zustand aueh besteht 7 Im letzteren Falle musste Methylitthylglyoxlm-kupfer In optlsche Antlpoden zu spaiten sein.
F t l t u o n - W i t denken dass das MolekQl auch In L6sung dieselbe Konflsuration behalten kann w~nn diese konfl~mration aus ether gtarken H,BrQcke s t a m m t . Aus keinem Grunde soil diese H - B i n d u n g in L6sung gebrochen werden. Ftlr was sich aug des Methyl-~thylglyoxim-kupfer bezieht, mt~chten wit bemerken das Methyl-gLthylglyoxim-kupfer isomorph dem Methylitthyiglyoxtm-nickei Jst (Cox E. G., S h a r r a t t E. Wardlaw W., Webster K. C. - J. Chem. Soc. (1936) 129), und dass dleser Komplex als planar, b e s t i m m t wurde (Mllone M., 10o Congr. Int. Chim. Boma, 2 (1938) 346). @ s p r l n ( F r a n k l u r t A . M . ) - Zuerst wird aug eine frOhere r o e n p n o g r a p h i s c h e Untersuehung yon Peeh, Polster, Regabek in Chemieki Listy augmerktam gemacht, die ebeugalls p zeigt h a t dass Cu-dlmethyl-g]yoxim Komplex nicht isomer ist m l t den entsprechender Komplexen yon N i , Pt, Pd. Wird p f r a g t ob aus der U n t e r s u c h u n g angenommen werden kann dass die Bindtmgen zwischen Cu u n d den vler N-Atomen in alien Fallen gleichartig angesehen werden k6nnen. FruNn wertig.
- Wie m a n aus dem Blld 2 sehen kann, sind die vJer Bindungen C u - N gleich-