+ Y ---+ Pt(SH3)?Y2-‘ + H20
l-’t(SHj)BY(HnO) ’ -
k6
(14,
By using the steady-state assumption for the concentration of the intermediates Pt(NH&(H?O)Cl-, Pt(NH&YCl+ and Pt(NH&Y(H?O) ++, the rate equation reduces to
(151
I t actually has been observed that the initial, rather rapid, rate of liberation of C1- drops to a much lower value even before half of the total chlorine has been liberated, and that the smaller the con-
[COSTRIBUTION FROM TIIT; ISSTITCTE O F
centration of the incoming group, \-, in the solution, the earlier this drop off occurs. Furthermore, if chloride ion is added to the solution to begin with. then for the same concentration of Y , the slowing down takes place earlier. hddition of inore V a t this stage again speeds up the reaction. These arc all expected on the basis of eq. 15. Eventually all of the chloride ion is replaced by pyridine or nniline (see Experimental). Hence. the rate constant for the initial rate has been divided by two for the data given in Table I for these two re‘igents, ndniely, aniline and pyridine in their re:iction with fra?zs-Pt(NH3)eCl:. 1 < V A \ b T < J Y , ILL.
GEXERAL CHEMISTRY,
T f i E L X I I - E R S I T Y OF l-’ALERXIO]
Studies in Coordination Chemistry. I. The Effect of Solvents on Some Bis- (N-alkylsalicylaldimine)-nickel (11) Complexes I3.i LUIGISICCONI, PIEROPAOLETTI XKD GICSEPPEDEL R E RECEIVED FEBRUARY 5 , 19ST .i series of bis-~S-alk~lsalic~-lalditriiriej-nickel[II I complexes in the solid state and in iuluticiii of organic solvent> was h u b iiiitted t o magnetic, spectrcJphotornetric and electric moment measurements. T h e results of dipole moment determination afford evidence against the 111-pothesis of a tetrahedral structure of such complexes when dissolved in “non-coordinating” solvents. T h e paramagnetism developed in such solutions and some characteristic features of t h e absorption spectra can he understood with t h e hypothesis of an equilibrium involving a n “outer orbital” -Lsip2idplanar configuration. T h e niagnetic behavior and t h e absorption spectral d a t a of these complexes in t h e solid state are discussed in terms of this concept. Observations on the influence of t h e length of t h e n-alkyl chains attached t o t h e nitrogen atoms on these properties arc rcported. T h e zigzag shape of t h e curves of magnetic moments, atomic polarizations and melting points for this series of cornpleses are correlated with changes of base strength and coordination power of t h e parent amines. T h e smaller t h e coordination power of the amine, t h e greater the polarity and thus t h e “outer orbital” character of t h e coordinate bonds of t h e cotiiplex. This is also accompanied by a greater ease of bending vibrations of t h e chelate rings and a greater tendency for interactions betiveen the polarizable molecules in t h e crystals.
The iiiagnet,ic behavior c1-t‘ nickel complexes has proved of considerable value in obtaining useful information concerning the bond type arid the stereochemistry of such compounds. Generally magnetic measurements have been carried out on metal complexes in the solid state. However, some measurements also have been made on complexes dissolved in organic solvents. French, lragee and Sheffield, postulate t h a t the weak paramagnetism (1.0 B.M.‘) exhibited by a methanol solution of diamagnetic bis-(formy1camphor)-ethyleiiediaminenickel(I1) is caused by a partial conLTersion of the planar complex to a tetrahedral form. Subsequently Willis and XIellor2 found t h a t a n u n ber of tetracovalent nickel(I1) complexes, diamagnetic in the solid state, exhibit paramagnetism in various solvents such as pyridine, alcohols, clioxarie, chloroform and benzene. The pararnaglietisin observed in pyridine solutions, corresponding to two impaired electrons, was attributed to an expansion of the coordination number to six. ’This solvation reaction was confirmed by Basolo and Matoush3 through the isolation of the corresponding paramagnetic complexes coilt airiing two molecules of pyridine. Somc complexes such as bis- iformylcariiplioi-! ( I ) IT. S French, 11. Z . 11agee and E . Sheffield, THISJ O U R N A L , 64, 1!124 (1942). ( 2 ) J 13 ll-illis ; $ r i < l 1’ l l c l l o r , ihi.1 , 6 9 , 1 c > 1 < 1 \\’ I < \ I ~ ~ ~ i h~ i i ,~ 76. IIs/I,
r)
ethyleriediariiilienickeliI1j . bis- (salicylaldoxime i nickel(I1) and bis- (3-methylsalicylaldimine)-nickelIII), diamagnetic in the solid state. exhibit paramagnetism even in “non-coordinating” solvents such as benzene and chloroform.? I n such cases, where the magnetic moment is intermediate between 0 and 3.2 B X . , it was suggested that a proportion of the molecules of the complex is c o w vertecl from a. planar to a tetrahedral configuration.’ I n this connection Basolo and Matoush3 found that no direct correlation exists between the magnetic moment of bis-(formy1camphor)-ethylenediarninenickel(I1) in methylbenzenes and the base strength of these solvents. They concluded that the paramagnetism iiiust therefore not be due to solvation but rather to formation o f tetrahedral nickel(I1) compounds. Nyholm4 recently suggested t h a t the interinolecular crystalline forces in solids may sometimes favor the square configuration, whereas in solution. the tetrahedral arrangement of lowest potential energy iriay be adopted by the isolated molecule. The magnetic measureinents by Fujii and S u m - tani5 and by Clark and Ode116 on solutions of such complexes in non-coiirdinating solvents over :I (4) R. S . Nyholm, Chem. Reas., 53, 263 (1953). ( 6 ) S. F u j i i and A I . Sornitnni. ,Pri. Repts. Tdhoku I m p . C > t i v . . I;i~’>l T,,,.ivs, 37,49 (1!458) ilii
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