Werner Centennial

36 Complexes of Some Transition Metals with Polydentate Aliphatic Amines G E R T G. SCHLESSINGER

Downloaded by CORNELL UNIV on June 14, 2017 | http://pubs.acs.org Publication Date: January 1, 1967 | doi: 10.1021/ba-1967-0062.ch036

Newark College of Engineering, Newark, N. J. The background, chemistry, and steric assignments of ali phatic and cycloaliphatic amines containing three or more coordinating nitrogens are discussed in relation to complex formation of transition metals. Particular attention is focused on the polyethyleneimines and recent work on 5-coordinated structures. Spatial arrangements of many well-known and new complexes are proposed, based on analogy to known ammines, steric ligand requirements, and physical and chemical data. General synthetic methods are outlined according to the number of coordi nated nitrogen atoms, including recent work with the new ligand pentaethylenehexamine. he purpose of this paper is to describe the preparation and properties of coordination compounds containing ligands with three or more aliphatic or cycloaliphatic amino nitrogens. In this discussion the material will be divided into three major sections: 1) The period 1925-1950 2) Some current work 3) Research carried out i n the author's laboratory, including general preparative methods In order to stress the great potential for further work in this field, the problem of stereoisomerism is treated concurrently with the structures considered. The Early Period A t the time of Werner's premature death i n 1919, the three basic geometric configurations of ligands i n complexes, the square plane, the tetrahedron, and octahedron had been well-accepted for unidentate and bidentate ligands. The 169 papers written by Werner and his students 565 Kauffman; Werner Centennial Advances in Chemistry; American Chemical Society: Washington, DC, 1967.


566

WERNER CENTENNIAL

attest to his painstaking efforts to establish his fundamental stereochemical postulates. It was obvious to chemists in the early twenties that an extension of Werner's ideas into compounds with polydentate ligands involved the syntheses of suitably constituted, organic substances. Among these were the higher homologs of aliphatic amines related structurally to 1, 2diaminoethane (en), dl-\, 2-diaminopropane (pn), and 1, 3-diaminopropane (tn). Efficient synthetic routes to these "long-chain" bases were at best tedious and frequently very difficult with conventional laboratory equipment. A s a result, rapid preparative progress in this field was hindered until after World War II when many of these amines became commercially avail able due to their use as cross-linking agents in the polymer and rubber industries. One of the first tridentate amines studied was 1, 2, 3-triaminopropane (24, 25, 26, 27, 28, 29, 30) (ptn) with a large variety of transition metals. The expected 3-coordination was found in all cases except with P t ( I V ) where the amine is only bidentate. This produced a demonstrable optical activity due to the preferential formation of a five-membered chelate ring. _ H H H N—CH N- C Cl Ptb \ -NH X Cl Ptb \ N- CH HC\ N- / H H -CH 2

2

2

2

4

4

2

I

3

2

2

CH NH X_ 2

3

Symmetric—optically

Asymmetric dl form

inactive

The compound [Coptn ]Cl was also partly resolved into a dextro rotatory form. This was probably the f a c - A B A cis B form—the only possible optically-active isomer. The others are m e r - A B A and f a c - A B A trans B where ptn = A B A , fac = facial or occupying one face of the octa hedron, and mer = meridianal or positioned along the edge of the figure (45). Stability constants of ptn have been reported (37). 2

3

®

Facial-uvw

Meridianal-uvw

Kauffman; Werner Centennial Advances in Chemistry; American Chemical Society: Washington, DC, 1967.

36.

Transition Metal Complexes

SCHLESSINGER

567

Another amine specifically designed to test Werner's postulates is 2,2',2''-triaminotriethylamine (12, 21, 33) (tate), which can be either t r i - or tetradentate. In the latter capacity it can fill four vicinal positions i n an octahedron or tetrahedron but not in a square-planar form. W i t h Co (III) it can form the expected octahedral cis-[Co (tate) (SCN) ]+ as well as the tridentate [Co3en (tate) ] . The two tate molecules presumably occupy trans positions i n the polymeric complexes because attempts at resolution proved fruitless. A possible structure is: 2

6

+9

2

+9

N


C!H>

I

C2H4

NH

H N

C2H4

\ NH2

2

2

3o

3o NHj \ C2H4

NH \

C

| N

NH /

S

2

C2H4 H

V

with Ni(II) and Pt(II) tate forms tetrahedral structures due to the re strictive geometry of the ligand. A variety of stability constant data is available (84). Compounds containing diethylenetriamine or 1, 4, 7-triazaheptane (den) have been well studied (7, 22, 23, 32). Due to the apparent lack of resolution data and the fact that models show no preferential configura tional alignment for the amine, it may be tentatively assumed that the octahedral complexes prepared to date are the f a c - A B A trans B or the merA B A forms for [ M ( d e n ) ] + and the latter type alone for structures such as [ M d e n X ] , where X = any assortment of unidentate groups. This is in analogy to the known trans forms of the analogous triammino com plexes (17). Because the amine can assume either a planar or tetrahedral geometry, no problem seems to exist with other metals having these steric requirements. Stability data have been determined for den complexes of many transition metals (9, 13, 14, 36). The next member of the "polymeric" ethylenediamine series, triethyl enetetramine or 1, 4, 7, 10-tetraazadecane(trien), was used by Basolo (1), Jonassen (15, 16), and Pearson (32) to prepare some Co(III), N i ( I I ) , P t ( I I ) , and Pd(II) complexes. In all cases tetradentate behavior was observed. W i t h Co (III) only m-[CotrienCl ]Cl could be obtained, which m

i n

2

3

3

2


568

WERNER

CENTENNIAL

suggested a preferential nonplanar octahedral orientation of the trien— viz., cis-u-trans A (trien = A B B A ) , or cis-u-trans A B (u = CI); the com pound was resolvable. On the other hand, the diamagnetism and nonresolvability of [Pttrien][PtCl ] and the Pd(II) analog was in accord with a square planar structure. The low values of the instability constants for most trien complexes (9, 35) attest to the ability of the ligand to assume both configurations. Octahedral complexes of [ M t r i e n X ] + ( X = unidentate) should exist as (45): 4

in

a) trans-X

2

b) cis-X trans-A

3

c) cis-X trans-AB with b and c

as dl pairs and compounds such as [ M t r i e n ( G G ) ] + ( G G = bidentate) in two optically-active forms—viz., trans A and trans A B (45). Finally, the earlier literature lists (32) the preparation of [CotetraenCl] C l , where tetraen = tetraethylenepentamine or 1, 4, 7, 10, 13-pentaazatridecane. It was noted at that time that the compound obtained appeared t o be an intractable mixture of two components. This is not surprising in view of the fact that foui, optically-active, octahedral stereoisomeric pairs are theoretically predictable—i.e.:


in

3

2

a) b) c) d)

trans-A, trans-uC trans-AB', trans-uC trans-AC, trans-uB' trans-AC, trans-uA'

where tetraen = A B C B ' A ' and CI = u. Some Current Studies Very recently (20) the three possible stereoisomers of [CodenIDA] were prepared by Legg and Cooke ( I D A H = iminodiacetic acid).

+

2

[CodenCl J + Ag IDA + A g N 0 -> [CodenIDA]N0 + 3AgCl 3

2

3

3

This is the first known example where octahedral compounds of the type [ M ( A B A ) ( G H G ) ] have been resolved into all predicted forms—viz., m

a) mer-ABA

b) fac-ABA, trans-BH

c) fac-ABA, cis-BH.

It was unfortunate that the resolution of form c), the potentially optically-active one, was not reported. Also, it is interesting to observe that the easy technique of preferential chromatographic elution, developed earlier by Kauffman and co-workers (18) for isomer separation, was the method of choice. A simple route to Cr(III) tridentate monoamines was reported earlier this year (10), based on Werner's early work with C r 0 - ( N H ) or [ C r ( N H ) ( 0 ) ] in the triammine series (47, 50). 4

3

3

2

2


3

3

36.

569


SCHLESSINGER

Complexes such as [CrdenCl ] were readily made from the analogous [Crden(0 )2]H 0 and H C I . Again, no apparent attempts at stereochemical resolution were attempted, although compounds such as ( M A B A u ] should exist in two isomeric forms. However, the visible absorption spec trum of [ C r d e n ( H 0 ) ] indicates a f a c - A B A conformation i n analogy to findings with the ammonia analog (17). 3

2

2

m

2

3

3

+3

The ligand 1, 1, 7, 7-tetraethyldiethylenetriamine (Et den) has been employed (8) to prepare unusual 5-coordinated species such as [Co(Et den)Cl ] and the Ni(II) analog. Because these materials are nonelectrolytes and paramagnetic, they may be regarded as high-spin trigonal bipyramidal complexes. B y contrast, [Rh(Et den)Cl ] is apparently octa hedral, and it is likely that the one of two possible stereoisomers obtained has the m e r - A B A structure; the f a c - A B A form would involve considerable steric repulsion between the bulky terminal N E t groups. 4

4

2


4

3

2

Sargeson and Searle (89) have followed the spatial changes in substi tution reactions of the two pairs of dl isomers in complexes of trien and Co(III), such as [Cotrien (u , uv, or GG)], where u = C l , ( H 0 ) , ( N 0 ) ; uv = CI and H 0 ; and G G = C 0 ~ . Optical methods such as circular dichroism, and rotary dispersion and absorption were used i n addition to polarimetric measurements. Regrettably their paper did not present the synthesis of the enantiomers employed in the work. A similar series of salts to the above was made by House and Garner (11) with Cr(III) as the central ion. However, only the cis-u trans A unresolved forms of [Crtrienu ] were prepared, where u = C l ~ , N C S ~ , or N and the trans A form of [Crtrien(C 0 )]+. Visible and infrared spectra were used to support the above assignments of configuration. The reaction of the dextrorotatory trans A isomer of [CotrienCl ] with liquid ammonia or en (19) leads to optical inversion. However, gaseous N H causes extensive racemization with retention of configura tion. This was also observed by treatment with 1, 10-phenanthroline i n boiling pyridine. 2

2

2

2

3

2

2

2

2

2

2

3

+

_

2

4

2

+

3

The levorotatory form of the trans A B isomer showed no inver sion or appreciable optical activity loss in its reaction with en to form [Cotrien(en)]Cl . The fact that the Z-trans A B form was obtained from both dichloro isomers indicates that Basolo's [Co(trien)(en)]Cl (1) was the racemic form (trans A B ) because his [CotrienCl ]Cl was also inactive. Nothing can be said of the structure of this complex which was used as starting material because either possible isomer would have led to the inactive trans A B [Cotrien(en)]Cl above. He was unsuccessful i n resolving the latter, owing to the extreme solubilities of the intermediate salts required. 3

3

2

3


570

WERNER CENTENNIAL

dl-trans A-[Co(trien) CI,]C1\ or dl-trans AB-[Co (trien) en]Cl dl-trans AB-[Co(trien)Cl ]Cl/< 2

s

en

Ciampolini and co-workers in Italy have prepared some 5-coordinated complexes with tris (2-dimethylaminoethyl) amine (4) (metren) and bis (2-dimethylaminoethyl) methylamine (5) (medien). Conductance and spectral data in nonaqueous media for materials such as M X - metren preclude 6-coordinate formulation as a nonelectrolyte but favor rather a trigonal bipyramidal structure such as:


n

a)

[Mn(metren)X]X

2

b)

which is a 1:1 ionic type salt; apparently the workers did not consider form b) seriously in their configurational assignment, possibly due to the fact that known 5-coordinate structures are distorted in relation to their axial-trigonal planar, bond distances. This might cause some strain in the N - C - C - N link of the ligand in b) which is shaded above. In a) this would not be expected to occur. It was noted that largely on the basis of physical evidence, similar compounds of the nonmethylated amine (tate) seem to be on the borderline of compatibility for 5- or 6-coordination, depending on the nature of the metal and the other ligands present. Either formulation, such as [ M ( t a t e ) X ] X with C . N . 5 ( C . N . = coordination number) or [ M ( t a t e ) X ] with C . N . 6 (octahedral), can be written for these complexes. U n doubtedly, crystal-field effects play an important role in these particular cases. Transition metal compounds with tridentate (medien), such as [ M ( m e d i e n ) X ] , were shown to be 5-coordinate also but showed only small conductivities in nitroethane and, with the exception of C u (medien) C l , were nonconducting in chloroform or nitrobenzene. These products were thus written as nonelectrolytes with a stereochemical arrangement intermediate between a square pyramid and trigonal bipyramid. This appears necessary since the N - M e t a l - N angle must be equal to n

H

n

2

2


2

36.

SCHLESSINGER

or less than 90° for these figures. It should be noted that both geometric forms have been found by x-ray data (31, 38). A series of extremely interesting complexes of Co (III) and N i ( I I ) has been recently reported by Bosnich and his colleagues (2, 8), using tetradentate 1, 4, 8, 11-tetraazocyclotetradecane (cyclam). These sub stances, made by conventional methods, have the four nitrogens of the ligand more or less i n a planar configuration, giving rise to octahedral trans complexes such as [Co(cyclam)X ] , where X is a unidentate nega tive or neutral species. I n addition to the trans dichloro compound (green), a small amount of a purple isomer, presumably the cis form, was also obtained. Octahedral models of the cyclic amine show that four possible strainfree planar conformations are possible, as well as two bent arrangements which lead to cis orientation of the remaining two coordination positions. Because each of these six unhindered configurations is distinct from one another, mirror images of each form are possible—even for the trans structures. The latter phenomenon would be without precedent, and further investigation may open a new chapter in inorganic isomerism. W i t h N i ( I I ) salts cyclam forms a series of salts which are represented by N i ( c y c l a m ) X . These behave as 2:1 electrolytes in water and methanol, and the visible absorption spectra are independent of the nature of the anion. However, an x-ray diffraction study of the dichloride ( X = CI) shows a planar ligand arrangement with the two chlorine atoms at the apices of an octahedron but unusually far away (2.5 A.) from the nickel. A t this point, the nature of these unusual compounds is perhaps best formulated as [Ni(cyclam)X ], which dissociates to [Ni(cyclam) (Sol) ]X (Sol = solvent) i n water or methanol. More work is needed to solve the problem unequivocally. 2


571


+n

2

2

2

2

Synthetic Methods and Author's Work Complexes i n this section will be described according to the number of coordinated amino nitrogens per metal atom. Included are preparative techniques which can be generally applied i n the area of polydentate coordination chemistry (40,41,42,48,44)Cobalt (III). HEXAMINES. Materials such as [Coden ]+ , [Codpn ] , where dpn = dipropylenetriamine or 2, 5-dimethyl-l, 4, 7-triazaheptane, [Co trien ] and [Copenten] , where penten = pentaethylenehexamine or 1, 4, 7, 10, 13, 16-hexaazahexadecane, are most readily prepared from Co (II) salts by the general equation 2

2

4Co

3

+2

+6

3

2

+3

+3

+ 4 X amine + 4 amine H

+

+ 0 -> 4[Co(amine) i] 2

x+

+3

+ 2H 0 2

(1)

where X , of course, will vary according to the polydentate nature of the amine. The anion of the Co (II) salt and the ligand should be the same


572

WERNER

CENTENNIAL

if a product is to be isolated; for a solution of the complex cation alone it is immaterial. A i r is generally bubbled through the aqueous mixture although hydro gen peroxide is usually much more rapid in its action and convenience. Aeration times may vary from two or three hours for den to one week for bis (3-aminopropyl) methylamine (medtn). Methods which start from preformed Co (III) salts are more versatile in synthetic scope but necessitate the prior formation of the intermediate. In these instances solvents such as methyl, ethyl, or isopropyl alcohol are preferred over water due to the ease of product isolation; solubilities in H 0 sometimes cause serious problems in preparation and purification. However, 1-10% (vol.) of water may be desirable in the alcohol as a catalyst. Also, an excess of 10-50% (wt.) of the entering ligand is usually required to ensure rapid and complete conversion. The following equations will summarize the methods employed.


2

[Co(NH ) ] 3

6

+3

+ X amine -* [Co (amine) ] x

+3

+ 6NH

(2a)

3

[Co(NH ) Y] Y + X amine -* [Co(amine) J Y + 5 N H 3

5

2

3

(2b)

3

[Co(amine)Cl or (N0 ) ] + (amine) —> [Co(amine)(amine) ] C l or (N0 ) 3

2

1

3

1

3

2

(3a)

3

The first tridentate amine may be the same or different from the second; ammonia (with activated charcoal in water) may even replace the latter to produce salts such as [Co (den, dpn or dtn)(NH ) ]+ , where dtn = 1, 5, 9-triazanonane. The series [Codtn ]+ had to be prepared by Equation 3 because Method 1 gave only the red binuclear [Co dtn (OH) ]+ . This is a /i-triol complex of which the hexammine analog is long known (49). The same result was obtained with the new ligand medtn or 5-methyl-l, 5, 9-triazanonane. Procedure 3a can be used to prepare complexes with mixed ligands of the widest variety as follows: 3

2

i)

[Co den (en, pn, tn^] *

ii)

[Co dpn (en, pn);}]*

2

2

3

3

4

2

2

3

3

3

2

6

2

e.g., 2[CodenCl ] + 3 en -> [Co den en ]Cl 3

2

2

3

(3b)

6

T n yielded no analogous product in this case. While [Codtn(N0 ) ] gave no hexamine type salts with en, pn, or tn, [CodtnCl ] produced the desired [Co dtn (en or pn^]" " ; again tn gave anomalous results. [CodenCy reacted with medtn to yield the unexpected product, [Co4den medtn (OH)6] (brown violet), a tetranuclear complex of the /x-hexol type (48), where the medtn appears to be unidentate; the possi bility that both amine ligands are bidentate cannot be excluded. F r o m the reaction of [CodtnCl ] with medtn, purple [CodtnmedtnCl]Cl (medtn = bidentate) and red [Co dtn medtn (OH) ]+ (dtn = bidentate; 2

3

3

2

3

1

2

3

6

+6

3

2

2

2

2

3

3


36.

573


SCHLESSINGER

+3

—C H -NH

H N—C H —HN 2

3

3

6

H C 6

C H 3

3

Proposed Structure for the [Co Medtn $ (0H) ] * 6


3

+

6

2

6

Ion

medtn = unidentate) were obtained. The last complex also belongs to the M-triol series above. When excess medtn was refluxed with [ C o ( N H ) C l ] C l in 2-propanol (99%) for one week (Method 2b), with the hope of obtaining [Comedtn ]Cl , two polynuclear products were isolated: brown [Co4medtn (OH) ]" (48) (medtn = tridentate) and deep olivegreen [Co medtn (OH) ] (medtn = bidentate), which belongs to the relatively little known hexammine-/x-hexol-tricobalt series (46). It is difficult to see how one of the medtn molecules could span the first and third octahedra in this case, except with the two terminal nitrogen atoms, while the other two ligands use their neighboring N atoms. A poly meric constitution seems to be the only alternative. Apparently medtn has a C . N . of one, two, or three, depending on the geometry of the cation and steric requirements of other ligands present. The preparation of transition metal complexes with penten marks the last step in mononuclear octahedral complexes begun by J0rgensen and Werner last century with ethylenediamine. Stuart models indicate that the fifth and sixth amine nitrogens are progressively harder to fit into place on the octahedron. If we assume a five-membered ring strain with each tetrahedral nitrogen of 1.5°, the fourth and fifth rings would have a cumula tive strain of 6 and 7.5°, respectively. The ion [Copenten]+ should exist in four pairs of optically-active isomers: 3

5

2

2

4

3

6

3

6

3

f6

+3

3

a) b) c) d)

trans-AC trans-AC trans-A trans-AB

1

1

trans-A^ trans-A^ trans-B trans-A^

where hexen = A B C C ^ A

1

1

The stereochemistry of polynuclear complex ions is quite involved and will be mentioned only in passing here. Thus, an ion such as [ M ( A B A ) ( G G ) ] + , where A B A = tridentate amine and G G = bidentate amine, has 10 isomers, of which four are optically active and five 2

m

2

3

6


574

WERNER

CENTENNIAL

are internally-compensated, meso forms. In this case, one molecule of the amine G G serves to link the two octahedra together. PENTAMINES. B y simply adjusting the molar proportions i n E q u a tion 3b to a 1:1 reactant ratio, compounds such as [Co(den or dpn) (en, pn, or tn)Cl]+ may be readily prepared. Ammonia may replace the bidentate amine i n the absence of carbon to form [Co (den or dtn) (NH ) C1P. When [CodtnCl ] was heated with en, pn, or t n i n 1:1 ratio, only hexamine salts were formed with en and pn—viz., [Co (dtn) (en or pn) ]+ , leaving one-third of the nonelectrolyte starting material unreacted as required for a 3 amine: 2 complex stoichiometry. W i t h both 1:1 and 3:2 ratios, t n produced the binuclear "pentamine" compound [Co dtn tn Cl ]+ , where the dtn is bidentate, presumably due to steric requirements. A 3:2 ratio is also involved here: 2[CodtnCl ] + 3tn —» [ C o d t n t n C l ] C l and unused trichloro complex was recovered when the reaction was carried out i n equimolar proportions. Of particular interest i n this section is tetraen, which has not yielded any isolable hexamine-type salts with Co (III) as yet. The pentanuclear structure required is [Co tetraen ]Xi and should be formed without diffi culty. The solubility of salts of this cation appears to be very high in water; more work is currently i n progress. However, this ligand is ideally suited for the facile preparation of purple [CotetraenCl]Cl , which can be easily made from [ C o ( N H ) C l ] C l and the amine by refluxing one day in absolute ethanol. The alcoholinsoluble product is contaminated with a trace of starting material while the mother liquor contains a green basic polynuclear by-product. Attempts to make the tetraen complex i n water gave impure substances or mixtures. When aqueous tetraen was heated with C o ( N H ) ( N 0 ) (32), the final purple "product" was shown to consist of at least three different constituents, of which only about 1 0 % seemed to be the desired material. This was demonstrated by its conversion to [CotetraenNH ]I with aqueous ammonia and activated carbon. Octahedral complexes of the type [ M ( A B A ) ( G G ) u ] exist as a) m e r - A B A ; b) f a c - A B A trans-uB; c) f a c - A B A cis-uB (dl pair). [ M ( A B C B A ) u ] has four stereoisomeric forms, below, all of which are optically active. 2

3

2

3


2

2

2

3

5

6

6

3

2

2

3

2

4

2

3

2

4

5

2

3

3

3

3

5

2

2

3

3

m

I I I

1

1

a) b) c) d)

trans A trans A B trans A C trans A C

1

trans uC trans uC trans uA trans u B

1 1

TETRAMINES. B y careful treatment of triamines such as [Coden(N0 ) C1] for short periods of time with dilute aqueous ammonia, one N H molecule displaces a chloride ion to form [ C o d e n N H ( N 0 ) ] , 2

2

3

3


2

2

+

36.

Transition

SCHLESSINGER

575

Metal Complexes

which is the only example (6) of its amine type—viz., [ M A B A u v ] , where u = N 0 , v = N H , A B A = tridentate amine. m

2

2

3

Treatment of the above ion as the chloride with cold concentrated H C I replaces one N 0 group giving [ C o d e n N H ( N 0 ) C l ] C l represented by [M ABAuvw]. 2

3

2

m

In analogy to the behavior of Zrans-[Co(NH ) (N0 ) ]Cl with H C I , it appears certain that the dinitroamine complex is the inactive m e r - A B A (Structure I) trans-u isomer of the four possible ones. The resultant chloronitroamine chloride should then be the inactive m e r - A B A trans uw, where w = CI, u = N 0 , and v = N H 3


2

N0

4

2

3

©

2

NH

2

N0

3

0

2

N

NH

N

N

3

CI

NO,

II

I

For Structure I I five other stereoisomers can be written. three are dl pairs.

Of these,

TRIAMINES. The most useful starting materials i n this series are represented by the general formula [Co (amine) ( N 0 ) ] and can be made, with varying success, by three different routes (6). 2

3

1) From Co(II) salts: 4 Co

+2

+ 12N0 " + 4(amineH) + 0 - » 4[Co(amine)(NO,),] + 2 H 0 +

2

2

2

2) F r o m Jrans-trinitrotriammine cobalt ( I I I ) : Co(NH ) (N0 ) + amine -> [Co(amine)(NO,) J + 3 N H 3

3

2

3

3

3) From sodium hexanitrocobaltate ( I I I ) : Na [Co(N0 ) ] + amine -> [Co(amine) (NO ) ] + 3 N a N 0 3

2

6

2

3

2

The den and dpn analogs can be made by all three methods, while with dtn Procedure 2 has been used. The latter is the most convenient and rapid preparative technique for all these three amines. When Method 2 was applied to medtn, a good yield of a brick-red water-insoluble product was obtained. The other trinitro compounds are mustard-yellow by contrast. Analysis of the red substance gave 25.2%C, 5.89%H, and 2 2 . 9 % N . This checks for [ C o m e d t n ( N 0 ) ( H 0 ) ] , where medtn is only bidentate. 2

2

2

5

2

2


576

WERNER

CENTENNIAL

Upon heating a mixture of the amine with N a [ C o ( N 0 ) 6 ] i n absolute ethanol, no reaction occurred until a small amount of water (ca. 5 % by volume) was added; the identical red nitro compound and colorless sodium nitrite then formed rapidly. A suggested tentative structure is: 3

N0

2

0* N •

H N 2

NO, NH

)

4[Co(amine)(SCN) ] 2

4

2

2

3

+

4R0K + 2H 0 + 4KSCN 2

The same procedure, when carried out with dtn, yielded a tan pre cipitate upon mixing the reagents which turned brown on aeration. Two preparations gave S = 19.55, 15.51%; N = 20.20, 20.28%; calcd. for


36.

577


SCHLESSINGER

[Codtn(SCN) ]: S = 26.4; N = 23.05%. these two latter substances is not clear.

A t this writing the nature of

8

Other Transition Metals. COPPER. W i t h den, dpn, trien, tetraen, and penten, Cu(II) forms the interesting series (40, 4U 4®, 44)' i) [CuadenJ

[CuIJ.

olive-green

ii) [CujdpnJ

[Child. ;

dark olive-green

iii) [Cutrien]

[CuIJ, ;

green-black

iv) [Cutetraen] [CuIJ,

green-black

v) [Cu penten ] [CuIJ, ;

deep olive-green


3

2

by the following sequence of reactions: y Cu

+ 2

+ x amine —> [Cu (amine) ] w

x

+2tf

2yl~ + [Cuy(amine) ]+* + 2y C u l —> [Cu (amine)x][CuI ]2 T

1/

2

W

The first three compounds have been shown to be nontetrahedral in structure by their reflectance spectra (40, 41, 42, 48, 44)) presumably they are square planar. W i t h trien this seems to confirm previous findings with Pt(II) and Pd(II) (15). Apparently, the tetraen analog has an uncoordinated ethylamine group i n preference to forming a pentanuclear copper complex cation such as [Cu tetraen ] °. More physical studies are i n order for these materials to establish their nature unambiguously. 5

4

+1

N I C K E L . W i t h tetraen and penten, N i ( I I ) produces the violet octa hedral ions [ N i t e t r a e n ] and the expected [Nipenten]+ isolated as the perchlorates. The behavior of copper and nickel with tetraen thus presents an interesting contrast as yet unclarified. 5

6

+10

2

ZINC. Zn(II) forms [Zntetraen]+ and [Znpenten]+ with the same ligands and thus behaves similarly to Cu(II) with tetraen; the stereo chemistry of these cations is still i n doubt. It is puzzling why zinc reacts in a 1:1 ratio with penten instead of forming a trinuclear complex such as [Zn penten ]+ in analogy to Cu(II). 2

3

2

6

2

CADMIUM. This element behaves i n the same way as Cu(II) towards tetraen and penten forming [Cdtetraen] and [Cd penten ] , both isolated as the iodides. When the latter compound is recrystallized from a large quantity of boiling water, apparent degradation occurs to produce [Cd pentenI ]I , tentatively written as a 4-coordinate 2:1 electrolyte. +2

2

2

3

2

+6

2

M E R C U R Y . Upon mixing a solution of mercury (II) chloride i n acetone with tetraen and penten i n the same solvent, the initially gummy precipi-


578

WERNER CENTENNIAL

tates become crystalline on standing. The molar ratios were 5 H g C l : 2 tetraen and 3 H g C l : 1 penten. Analytical data gave the following results. 2

2

Found

Calcd.

N

CI

11.75

20.20 N:C1 = 3:2

8.25


Hg tetraen Clio: 5

2

N = 8.08 11.95

N:C1 = 7:4

for

CI = 20.4

for Hg pentenCl : 3

6

N = 8.05

CI = 20.4

While the chloride value checks for the tetraen complex, the nitrogen analysis is satisfactory for the penten analog. If the first material is formulated as H g t e t r a e n C l i , in which the three ligand molecules use only 10 amino nitrogens to coordinate to mer cury, the calculated values become N = 10.9; CI = 18.4%. Also, assum ing an amido-type complex in the case of penten such as Hg (penten-3H)C1 , where the amine now has the formula C i H N , values of N = 9.0 and CI = 11.4% are obtained. A t best, the whole problem requires considerable further work. 5

3

0

3

0

2 5

3

6

Conclusion W i t h the ever-increasing variety of organic ligands available and the perfection of synthetic and physical investigative methods, coordination chemistry can systematically expand further into a vast but orderly array of chemical data. We owe all this to the ingenuity and genius of Alfred Werner, as well as to his successors in the scientific tradition he established. Literature

Cited

(1) Basolo, F., J. Am. Chem. Soc. 70, 2634 (1948). (2) Bosnich, B., Poor, C. K., Tobe, M. L., Inorg. Chem. 4, 1102 (1965).

(3) Ibid., p. 1109.

(4) Ciampolini, M . , Nardi, N . , Inorg. Chem. 5, 41 (1966). (5) Ciampolini, M . , Speroni, G. P., Inorg. Chem. 5, 45 (1966). (6) Crayton, P. H . , Inorg. Syn. 7, 211 (1963). (7) Crayton, P. H . , Mattern, J. A., J. Inorg. Nucl. Chem. 13, 248 (1960). (8) Dori, Z., Gray, H . B., J. Am. Chem. Soc. 88, 1394 (1966). (9) Douglas, B. E., Latinen, H. A., Bailar, J. C., Jr., J. Am. Chem. Soc. 72, 2484 (1950). (10) House, D. A., Garner, C. S., Inorg. Chem. 5, 840 (1966). (11) House, D. A., Garner, C. S., J. Am. Chem. Soc. 88, 2156 (1966). (12) Jaeger, F. M., Koets, P., Z. Anorg. Chem. 170, 347 (1928). (13) Jonassen, H . B., J. Am. Chem. Soc. 72, 4968 (1950). (14) Jonassen, H . B., J. Phys. Chem. 56, 16 (1952). (15) Jonassen, H . B., Cull, N . L., J. Am. Chem. Soc. 71, 4097 (1949).


36.

SCHLESSINGER


579

(16) Jonassen, H . B., Douglas, Β. E., J. Am. Chem. Soc. 71, 4094 (1949). (17) Jones, M. M., "Elementary Coordination Chemistry," p. 236, Prentice-Hall, New York, 1964. (18) Kauffman, G. B., Pinnell, R. P., Takahashi, L.T.T., Inorg. Chem. 1, 544(1962). (19) Kyuno, E., Bailar, J. C., Jr., J. Am. Chem. Soc. 88, 1125 (1966). (20) Legg, J. I., Cooke, D. W., Inorg. Chem. 5, 594 (1966). (21) Mann, F. G., J. Chem. Soc. 128, 482 (1926). (22) Ibid. 132, 1734 (1930). (23) Ibid. 136, 466 (1934). (24) Mann, F. G., Pope, W. J., Chem. Ind. (London) 44, 834 (1925). (25) Mann, F. G., Pope, W. J., J. Chem. Soc. 128, 2675 (1926). (26) Ibid. 129, 1224 (1927). (27) Mann, F. G., Pope, W. J., Proc. Roy. Soc. 109A, 80 (1925).


(28) Ibid., p. 444.

(29) (30) (31) (32) (33) (34)

Morgan, G. T., Smith, J. D . M., J. Chem. Soc. 127, 2030 (1925). Ibid. 127, 1684 (1925). Pauling, P., Robertson, G. B., Rodley, G. Α., Nature 207, 73 (1965). Pearson, R. G., J. Phys. Chem. 59, 305 (1955). Pope, W. J., Mann, F. G., Chem. Ind. (London) 44, 834 (1925). Prue, J. E., Schwarzenbach, G., Helv. Chem. Acta 33, 963 (1950).

(35) Ibid., p. 974. (36) Ibid., p. 985. (37) Ibid., p. 995.

(38) Sacconi, L., J. Am. Chem. Soc. 87, 2059 (1965). (39) Sargeson, A. M., Searle, G. H . , Inorg. Chem. 4, 45 (1965). (40) Schlessinger, G. G., Gannon Coll. Chem. J. 1964, 4. (41) Ibid. 1965 (2), 12. (42) Ibid. 1965 (2), 20.

(43) Schlessinger, G. G., "Inorganic Laboratory Preparations," Chap. 6, Chemical Publ. Co., New York, 1962. (44) Schlessinger, G. G., unpublished data. (45) Trimble, R. F., J. Chem. Ed. 31, 176 (1954). (46) Werner, Α., Ann. 375, 141 (1910). (47) Werner, Α., Ber. 39, 2656 (1906). (48) Ibid. 40, 2118 (1907). (49) Ibid., p. 4837. (50) Ibid. 43, 2286 (1910). RECEIVED July 5, 1966.


Werner Centennial

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