摘要：

Heft 14 ~959 (Jg. 46) K u r z e Originalmilieilungen Speclrophotometric Determination of the Dissociation Constant of r 13-Naphthol in Aqueous Solutions ~-nitroso fi-naphthol, ( a f t ) H , is used extensively as ana- lytical r e a g e n t for detection and e s t i m a t i o n of Ag +, Zr =+, Cu 2+, Co ~+, Fe s+, etc.l-~); for these purposes, solutions of (~-fi) H in b o t h a q u e o u s and n o n a q u e o u s media are employed. The dissociation c o n s t a n t k of (~-/~)H in n o n a q u e o u s media such as alcohol h a s been determined~). No d a t a exist in t h e literature on h for ( e - ~ ) H in a q u e o u s medium. ~-nitroso fi-naphthol of B. D. H_ q u a l i t y was used. This was recrystallized several t i m e s f r o m p e t r o l e u m ether and dried in a v a c u u m desiccator tilI it gave a c o n s t a n t melting p o i n t of 110 ~ C~). The a b s o r p t i o n m e a s u r e m e n t s of aqueous solutions of (~-~)H were m a d e on B e c k m a n D U s p e c t r o p h o t o m e t e r , using I cm cell. Buffers of CLAIR and LuBs, and of SORENSON were used. Fig. ~ gives t h e a b s o r p t i o n s p e c t r u m of (a-t) H ; it ex- hibits a b s o r p t i o n m a x i m a at A : 2 6 0 and 380 rob; at b o t h these wavelengths, the a b s o r p t i o n obeys fairly satisfactorily BEE~'S L a w (see inset, Fig. t). F u r t h e r the a b s o r p t i o n at = 380 m b varies m a r k e d l y w i t h p ~ (Table). The values of t h e : ~ , - - I ~ Zi4 5 76, 6025 (1954). - - x) FRITZ, F.: Anal. Chem. 27, I315 (1953). - - 4) WSSGXR, P.E., D. NONNIE~ and F. JACeARD: Heir. chim. Acts 33, t458 (1950). - - ~) KOMER, N.P., and V.N. ToLNAcnEv; Zhur. Anal. Khim. S, 21 ( t 9 5 0 ) . - 6) TREAnWELL, W.D., and G. ScnwAR- ZEXBACR: Helv. chim. Acts 11, 386 (t928). - - ~) Cf. Dictionary of Organic Compounds, Vol. III. London: Eyre & Spottiswoode 1946. - - s ) SAXTON, 13., and L.S. DARKEN: J. Amer. Chem. See. 62, 846 (t940). - - 9) KATCttALSKY, A., H. EISENBERG and S. LIFSON: J. Amer. See. 73, 5889 (1951). Eleetronegativity Considerations on Metal-ligand Bonds in Complexes I n t h e p r e v i o u s p a p e r s ] ) t h e electronic states of metallic complexes h a v e been t r e a t e d on t h e basis of LCAO M e t h e o r y and the a b s o r p t i o n spectra and m a g n e t i c b e h a v i o u r s of com- plexes, including the so-called spectrochemieal series and sol- v e n t effects of the s p e c t r a and solution p a r a m a g n e t i s m of some diamagnetic N i ( I I ) complexes, have been discussed emphasizing t h e i m p o r t a n c e of t a k i n g into a c c o u n t covalency of metal-ligand bonds. The t r e a t m e n t has led n a t u r a l l y to t h a t some a m o u n t of electron charge m i g r a t e s from ligands to a central metal cation due to coordination r a t h e r neutraliz- ing its net charge. According to the result, the electronegati- vities of t h e first t r a n s i t i o n metal ions b o u n d to ligands to f o r m complexes h a v e been calculated 1) a s s u m i n g t h a t the n e t charge of the ions is reduced to zero due to covalency of m e t a M i g a n d b o n d s (Table). Since several a u t h o r s =-7) h a v e t a k e n notice recently of covalency of m e t a l ligand bonds, it would be of interest to s t u d y the subject f r o m a v i e w - p o i n t of electronegativities. Table 1. Electronegativities o/ the ]irst transitwn metal cations coordinated with ligands i Metal E.N. dgg Z~:# 2#d 280 30~ 320 ?gg d#g def# fgY mp- Fig. 1. Absorption spectrum of a-nitrose a-naphthol. (Cone. 10.2 x t0 -~ M.) Inset: Applicability of BEER'S law. Curve I: Z = 260 m/5 I f : ~ = 380 m~ classical dissociation c o n s t a n t k c o m p u t e d f r o m t h e results given in c o l u m n s t and 2 are r e t u r n e d in c o l u m n 3. I t m a y be noted t h a t k does n o t r e m a i n c o n s t a n t at different p ~ . The d a t a are, however, explicable b y an e q u a t i o n s ) logh -- 2 A V ~ = locK-- B0 - ~)e, where A is the DEBYB-HOClCEL c o n s t a n t ; K, t h e t h e r m o - d y n a m i c dissociation c o

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