Mixed ligand complexes involving hydroxamic acids I. Complexes of benzohydroxamic acid in aqueous solutions

1N0R6. NUCL CHEM. LE77ER5 V~. 1~ pp. 391~9~ 1976. ~r8am0n Pre~ Pr1nted~ 6re~ 8r1~1n

M1XED L16AND C0MPLEXE5 1NV0LV1N6 HYDR0XAM1C AC1D5 1. C0MPLEXE5 0P 3EN20HYDR0XAM1C AC1D 1N AQUE0U5 50LU710N5 5hah1d A66a5 A66a51, 8.6. 8ha~ and R.5. 51n9h Department

0f Chem15try, 1n~1an 1n5t1tute 0f 7echn0109y, P0wa1, 8 0 m 6 ~ - 4 0 0 076

~ece1ved 20 0ct06er 1975)

8en20hydr0xam1c

aC1d (8HA), 8-hydr0xy4u1n011ne

(HQ),

2,2~ 61pyr1dy1 (81PY), 5a11Cy11c ac1d (5A) and the1r ana109me5 have 6een rec09n15ed a5 che1at1n9 a9ent5 that p1ay 1mp0rtant r01e 1n med1C1na1 Chem15try (1) and ana1yt1Ca1 Chem15try

(2).

5tud1e5 0n the 5ta6111t1e5 0f m1xed C0mp1exe5 0f Cu(11) w1th tw0 0f the f0110~1n9 119and5: HQ, 81PY mad 5A have rep0rted

(3,4) 6ut there 15 n0 5uch 4uant1tat1ve

6een

1nf0rmat10n

a60ut the 5ta6111t1e5 0f m1xed c0mp1exe5 1nv01v1n9 8HA 0r

1t5

a~a109ue5. C0n51der1~9 the e v e r 1n0rea51n9 1 ~ p 0 r t ~ 0 e 0 f hydr0xa~10 aC1d 11Eand5

(5,6), 1t wa5 f0Und de51ra61e t0 1n1t1ate 5tud1e5

0n m1xed 119and C0mp1exe5 1nv01v1n9 them. p0tent10metr1C

We rep0rt here

the

5tud1e5 0n a4ue0u5 501ut10n5 c0nta1n1n9 Cu (11)

0r N1 (11), 8HA and 0ne 0f the f0110w1n9 119and5 81PY, HQ5 (8-hydr0xY4u1n011ne

~-5u1f0n1c ac1d) and 5A.

~he 11~and5 81PY,

5A and HQ5 are ch05en 6eCau5e 81PY ha5 tw0 n1tr09en5 a5 d0n0r at0m5, 5A ha5 0xy9en5 a5 d0n0r at0m5 wh11e HQ5 ha5 60th 0xy9en and n1tr09en a5 d0n0r at0m5.

8114 15 an unchar9ed

119and, wh11e 5A and HQ5 are 10n15a61e t0 d1ne9at1ve f0rm.

391

392

M1xedL19andC0m~exe5

~

~ ~

~

~ ~

~

0=6

0~

~2

0;~

M0LE5 0F Na0H PER M0LE 0F L16AND Cu(11) 0r N1(11L 81PY and 8HA 5Y57EM

~2~ ~nt10metr~c

~

~

~

10

t1trat10n 0 u ~ e ~

~

~

~

~

~ 0f 5 ~ u t 1 ~ 5 1

0.1 ~

C°mP°5N~(~10u(1~ 1et++ 1

5

: 5

c0nt~n~9

~

2

1

=

~ ~

3

~0 0~1 a~2 a~3 M0LE5 0F N a ~ PER M0LE 0F L16AND Cuff11 0r N1 (111.HQ5 0nd 8HA 5Y57EM P1~E

P0ten%10me~r1¢

~1trat10n c u ~ e 5

5

0~ ~ 0 ~ t 1 0 n 5

c0nta1n~

0.1 M

M1xed L19andC0mp~xe5

393

~r~t~ 8en20hydr0xam1c ac1d wa5 prepared and pur1f1ed 6y the pr0cedure 0f 81att (7). 7he axper1ment51 pr0cedure f0r determ1nat10n

0f 10n1-

5at10n c0n5tant5 5md meta1-119and 5ta6111ty c0n5tant5 wa5 e55ent1a11y the cme deta11ed 6y 601d6er9 (8). were perf0rmed at 35°C and 1n an atm05phere

71trat10n5 0f (02 aud C02

free) N 2 w1th car60nate free 0.1 M Na0H. 7he m1xed 119and t1trat10n5 were perf0rmed w1th 0.1 M Na0H 501ut10n

0n 50 m1

501ut10n5 c0nta1n1n9:0.1 M NaC104

+ 0.01 M HC104 + 1 x 10-~ M meta1 10n + 1 x 10 "~ M 81PY 0r 5A 0r HQ5 and 1 x 10 -~ M 8HA under c0nd1t10n5 51m11ar t0 th05e 1n wh1ch 1:1 meta1-1198nd t1trat10n5 were d0ne.

7he m1xed

119and c0mp1ex f0rmat10n wa5 1nterpreted (5ee d15cu5510n) a5 tak1n9 p1ace ~n 5eparate neutra115at10n 5tep5 5md the

m1xed

119and 5ta6111ty c0n5tant5 were theref0re ca1cu1ated acc0rd1n9 t0 the meth0d 0f Marte11 et a1 (4). Re5u1t5 and D15cu5510n 81FY - 8HA - ~ 525tem 7he pH t1trat10n curve5 0f 81~Y, 8HA, 1:1 m1xture5 0f 81FY 0r 8HA w1th Cu(11) 0r N1(11) amd 1:1:1 m1xture5 0f 81FY and 8HA w1th Cu(11) 0r N1(11) are 5h0wn 1n F19.1.

1t 15

5een that 1n 5y5tem5 c0nta1a1m9 8fPY aud Cu(11) 0r N1 (1f) (curve5 6 and V, F19.1)

6uffer re~10n5 ex15t up t0 a ( 2

(where a repre5ent5 num6er 0f m01e5 0f 6a5e added per m01e 0f meta1 1cm)

f0110wed 6y 5harp 1nf1ax10n5.

d1pr0t0nated f0rm, 1nf1ex10n5 at a ~---- 2 f0rmat10n 0f 1:1 c~mp1ex.

51mce 81PY 15 1n 1nd1cate the c0mp1ete

7he c0mp1exat1~ c~,mence5 at

~4

~x~ L~

~m~

(a ~---~, pH < 3) and 15 e 0 m p 1 e ~

at pH ~-- 4.

1n the t1trat10n 0f 1:1 m ~ t u r e 5

0f 3HA and meta1 1~n,

the 8HA + 1 curve 6e91n5 t0 5eparate frcm 8HA curve at pH ~ A 6uffer re910n 15 065erved up t0 pH ~

4.

6.8, (a ~- 1) 1nd1ca-

t1n9 the f0rmat10n cf 1:1 8 H A ~ e t a 1 c0mp1ex. ~

the t1trat10n 0f m 1 x ~ r e 5

c0nta1n1D~ ~eta1, 81PY add

81~ 1n the rat10 1:1:1, the m1xed 119and curve5 are a1m05t ~per1mp05a61e cn the meta1-81PY curve up t0 pH "~ 4 1n ca5e 0f Cu(11) and up t0

~----5.5

1n ca5e 0f N1(11).

7he m1xed

119and curve 1nv01v1n9 Cu(11) ~ p a r a t e 5 fr0m 1:1 Cu-81P¥ curve a60ve pH > 4 and there 15 a 6uffer re910n f0110wed 6y prec1p1tat10n at pH -~ 7.1 (a ~

3).

7he N1-8HA-81PY curve 5eparate5

fr~m 1:1 N1-81PY curve at pH > 5.5 and a 6uffer re910n 15 065erved up t0 a=~- 3; pH =~ 8.5. 7hu5 there 15 a65en0e 0f prec1p1tat10n at a ~-- 5 1n ternary 5y5tem5 and there 15 a new 6uffer re910n 6etween a ~--- ~ ~nd a "~ 3.

A150 there 15 a c010ur chan9e 6etween 2 < a ~-- 3;

the C u - 8 1 P Y ~ H A m 1 x ~ r e Cu-81PY m1xture

15 9reen15h 61ue at pH 4 - 6

wh11e

15 5Ey 61ue 1n th15 pH ran9e.

7he5e 065ervat1~n5 p01nt t0ward5 a 5 t e 1 ~ 1 ~ f0rmat10n 0f m1xed 119and ccmp1exe5.

7he 1:1 met51-81PY c0m~1ex 15

f0rmed f1r5t f0110wed 6y m1xed 119and ccmp1ex, a5 1 n d 1 c a t ~ 6e10w.

~ ~

0H0--~N~--H ~ ~2~~:~N--~H ~

Where~ repre5ent5~U(1~)0r ~1(11);Waterm01~U1e56e1n9 0~1ttedf0r the 58~Ce0f 51mp1101t7.

M1x~ L ~

395

C0mp1ex~

7he n0n-5uper1mp05a6111ty 0f the the0ret1ca1 c0mp051te curve5 (curve5 10 and 11) drawn 6y add1n9 the h0r120nta1 d15tance5 0f M-81PY and 8HA curve5 w1th the c0rre5p0nd1n9 curve5 c0nta1n1n~ M-81PY-8HA, 15 an added ev1dence. 5A- 8HA - M 5y5tem 1t 15 5een that 1n t1trat10n5 w1th 1:1:1 m01ar rat10 m1xture 0f 5A, 8HA and meta1 10n5 (f19ure n0t drawn), prec1p1tate5 are 065erved at pH ~----6.8 and (a ~

2).

7he the0ret1ca1

c0mp051te curve 5uper1mp05e5 w1th the 1:1 Met51-5A curve 1nd1cat1n9 the a65ence 0f m1xed c0mp1ex f01mat10n up t0 the 0n5et 0f prec1p1tat10n. H45 - 8HA - M 5y5tem 1n th15 5y5tem m1xed-119and c0mp1ex f0rmat10n 15 065erved (curve5 8, 9, F19.2).

7he ar9ument5 1n fav0ur 0f

m1xed-c0mp1ex f0rmat10n are 5ame a5 1n 81FY-8HA-M 5y5tem5. 1t 15 5een fr0m curve5 6 and 9 1n ca5e 0f Cu(11) and curve5 7 and 8 1n ca5e 0f N1(11) that 1:1 c0mp1ex 15 f0rmed at 10wer pH f0110wed 6y 1:1:1 c0mp1ex at h19her pH 1n a 5tepw15e manner. 7A8LE 1 Ac1d D1550c1at10n C0n5tant5 and 5ta6111ty C0n5tant5 0f 1:1 and 1:2 Cmnp1exe5 (55° C, 0.1 M NaC104) ~1~11 ) 109 109 K 1

1 8HA

8.68

-

7.07

5.81

5.~

4.10

81PY

1.45

4.59

8.41

5.64

~.01

6.81

5A

2.52

15.24

10.51

7.98

6.96

4.8~

HQ5

5.84

8.45

11.95

9.98

9.10

~.76

~ x ~ L~nd C0m~ex~

396

7he 10n15at~n and 5ta6111ty c0n5tant va1ue5 are 5h0wn 1n 7a61e5 1 and 2. 7A8LE

2

N~xed L1~and 5ta6111ty C0n5tant5 (at ~°C, 0.1 H Na0104) Meta1

1109 ~ 1 x 8~Y-8HA 1109 ~ 1 x 8HA-5A1109 ~ 1 x 8HA-HQ5

0u ( 22 )

7.24

-

5.8~

N1(11 )

5.04

-

4.44

P~1~1n9 ~ta1n~.

~ ~ 1 ~ 5

C ~ 6e made f r ~ the re~1t5

F0r the 5a~e 0f c 0 n v ~ e

are ~rther ~ ~ d

t0 H ~ , H ~ , X ~

81~, HQ5, 5A and ~ A ~ d H2.

Ca) A1th~u9h the evera11 6a51c1ty (pK1 + pK2) 0f

H2X > H ~ , 109 ~ 2 (6)

<

109 ~ 2

A1theu~h the 0vera11 6a51c1ty 0f H2 ~ M

10~ ~

109~(

(1) H2X ,

M

>

10~ ~

...

(2)

(~)

109~

10~~ ~ 10~2

~d

(¢)

...

Ca)

A1th0u9h the 0vera11 6a51c1ty 0f H2 > H2N , M

and

M

109 ~

> 109 K~2

109 ~ 2

~-- 109 K~2~

109 K~2 ( 109 K~2 ~1~

...

C~) (~)

...

7he 065ervat10n5 2, 4 and 5 are 1m ~eep~n9 w1th the

(~)

~x~ ~

C0m~

397

preference 0f Cu(11) and N1(11) f0r n1tr09en d0n0r5 0Ver 0xy9en d0n0r5. 7he exp1anat10n 0f a11 0ther 065ervat10n5 can 6e 50u~ht fr0m the nature 0f c0u1em61c 1nteraCt~n5

0f the 10n5 1m

4ue5t10n. 7he 5ta6111ty 1ncrea5e5 w1th the 1ncrea5e 1n the ma9n1tude 0f the d1fference 1n char9e5 0f the 10n5. attract10n 15 max1~um 1n M ++- 2decrea5e5 1n ca5e5 0f ~

- L-

7he c0u10m6~

and ~W ++- 2- aud 1t

and ~W ++- W, cau51n9 the 5ta61-

11ty 0rder: KM

~

M2

KMW ~2

>

K ~x

>

MX2

K MW MW~

Re~r~ce 1.

D.R.H. 60URLEY 1n A. 8 ~ 6 E ~ ,

Ed.,

~Med1c1na1 Chem15try•,

1nter5c1ence, New Y0rk (1960). 2.

A.K. DE, 5.M. EH~PKAR and R.A. CHALMER5, 0f Meta15~, V0n N05tr5md,

3.

•501vent Extract10n

L0nd0n (1970).

5.6. 5CHUL~AN and H. 6ER5H0N, J. 1n0r9. N~uc1. Chem. D31

2467 (1969) 4.

6.A. L•HEUREUX and A.E. MAR7ELL, J. 1n0r9.

Nuc1. Chem.

~28 481(1966). 6.

A.K. MAJU)DAR,

~-8en20y1pheny1hydr0xy1am1ne

8nd 1t5

Ana10£ue5•, Per~am0n Pre55~(1972). 6.

6.R. 6ALE and L.M. A7K1N•, ArCh. 1nt. Pharmac0dyn. ~180 289 (1~6~).

7.

A.H. 8LA77,

•0r9an1C 5ynthe515•, 0011.V01.11,

p.67,

J0hn W11e~ and 50n5 1nC. ~ew Y0rk (1945). 8.

D.E. 60LD8~6,

J. Chem. Edu0. ~9 328 (1962), 40

541(196~).