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Preparation of some diselenocarbamate complexes of tin(IV) and their i.r. and pmr spectra
J. inorg,nuel.Chem., 1970,Vol.32, pp. 2621to 2628. PergamonPress. Printedin Great Britain
PREPARATION OF SOME DISELENOCARBAMATE COMPLEXES OF TIN(IV) A N D THEIR I.R. A N D PMR SPECTRA T A K A S H I K A M I T A N I , H I R O M I T S U Y A M A M O T O and T O S H I O T A N A K A Department of Applied Chemistry, Osaka University, Yamada-kami, Suita, Osaka, Japan (Received 16 December 1969) A b s t r a c t - S e v e r a l N,N-dimethyldiselenocarbamate complexes of tin(IV), RaSn(dmdsc)2 (R = C H 3 and C2H5), CH3CISn(dmdsc)2, CI2Sn(dmdsc)2 and (CH3)2SnX(dmdsc) i X = CI and Br), dimethyltin bis(N,N-diethyldiselenocarbamate) and bis(N-methyI-N-phenyldiselenocarbamate) have been prepared. The i.r. and pmr spectra of the dmdsc complexes suggest the chelation of diselenocarbamate group. The N-alkyl or Sn-alkyl proton signals of all the complexes show characteristic benzeneinduced solvent shifts, which are analogous to the case o f N,N-dimethyldithiocarbamate(dmdtc) complexes of tin(IV). A mixed chelate compound, (CH3)2Sn(dmdtc)(dmdsc), has also been isolated. The pmr spectrum indicates that difference in the coordination power toward tin atom is hardly discernible between diselenocarbamate and dithiocarbamate. INTRODUCTION
N,N-DIALKYLDITHIOCARBAMATE complexes of transition and non-transition metals have extensively been studied by many workers. However, the study of diselenocarbamate complexes have been limited to those of some transition metals [ 1-3]. It seems to be of interest to compare the coordination abilities of sulfur and selenium to metal atoms. This paper reports the preparation of several N,Ndimethyl-, N,N-diethyl- and N-methyl-N-phenyl-diselenocarbamate complexes of tin(IV), and their i.r. and pmr spectra. The spectroscopic results are discussed in comparing with those of the corresponding dithiocarbamates, which have previously been reported by one of the present authors [4, 5], and the configuration of the representative complexes is also described. EXPERIMENTAL Preparation (CHa)2Sn(dmdsc)2, (C2Hs)2Sn(dmdsc)2 and CI2Sn(dmdsc)z (dmdsc: Se~CN (CH3)2). A solution of CSe216] 112.4 m-mole) in dioxane was added dropwise to an aqueous solution containing N a O H ( 12.4 m-mole) and (CHa)2NH ( 12.4 m-mole) at --10°C under dry nitrogen, and the mixture was stirred for about ! hr at room temperature. N a O H + ( C H a ) 2 N H + C S e 2 - - - * Na[Se2CN(CHz)2]+HzO. This solution was added to an aqueous solution of (CHz)~SnCI2, (C2Hs)2SnCI2 or SnCI4 (6.2 m-mole), and followed by stirring for 30 min to give white precipitates of dimethyltin, diethyltin or dichlorotin bis(N,N-dimethyldiseleno1. 2. 3. 4. 5.
D. Barnard and D. T. Woodbridge, J. chem. Soc. 2922 (1961). K. A. Jensen and V. Krishnan, Acta chem. scand. 21, 1988 (1967). C. Furlani, E. Cervone and F. D. Camessei, Inorg. Chem. 7, 265 (1968). M. Honda, Y. Kawasaki and T. Tanaka, Tetrahedron Lett. 3313 (1967). M. Honda, M. Komura, Y. Kawasaki, T. Tanaka and R. Okawara, J. inorg, nucl. Chem. 30, 3231 (1968). 6. D . J . G . lves, R. W. Pittman and W. Wardlaw, J. chem. Soc. 1080 (1967). 2621
2622
T. KAMITANI, H. YAMAMOTO and T. TANAKA
carbamate) almost quantitatively. The former two were recrystallized from carbon tetrachloride, and the latter from chlorobenzene. (CH3)zSn(dedsc)2 and (CHa)2Sn(mpdsc)2 (dedsc: Se2CN(C2H5)2, mpdsc: Se2CN(CHa)(C6H5)). A solution of sodium N,N-diethyldiselenocarbamate or N-methyl-N-phenyldiselenocarbamate was prepared by the reaction of CSe2 in dioxane with (C2Hs)2NH or (CHz)(C6Hs)NH in aqueous NaOH solution. These solutions reacted similarly with (CH3)2SnCIz in water to yield dimethyltin bis(N,N-diethyldiselenocarbamate) and bis(N-methyl-N-phenyldiselenocarbamate), respectively, which were recrystallized from carbon tetrachloride. CHaCISn(dmdsc)2. To a solution of methylstannoic acid (6"2 m-mole) in I N-HCI was added dropwise a solution of Na{dmdsc) in water-dioxane, and the mixture was stirred for 30 min to give white precipitates of methylchlorotin bistN,N-dimethyldiselenocarbamate), which was recrystallized from o-dichlorobenzene. CHaSnOOH + 3HCI + 2Na [SesCN (CH3)2] -* CH3CISn [Se2CN (CH3)212+ 2NaCI + 2HzO. (CH3)2SnX(dmdsc) (X = CI and Br). Equimolar amounts of (CH3)2SnX2 and (CH3)2Sn(dmdsc)2 were dissolved in carbon tetrachloride, and the solution was evaporated to dryness under reduced pressure to give quantitatively dimethylhalogenotin N,N-dimethyldiselenocarbamates, which were recrystallized from carbon tetrachloride. (CHa)2SnX2 + (CHa)2Sn[Se2CN (CHa)2]z -'->2(CHa)zSnX[Se2CN(CH3)2]. (CH3)2Sn(dmdtc) (dmdsc) (dmdtc: S2CN(CH3)2). This compound was obtained by vacuum evaporation of a carbon tetrachloride solution containing equimolar amounts of (CH3)2Sn(dmdtc)2 and (CH3)~Sn(dmdsc)2, and recrystallized from carbon tetrachloride. Dibromo-, diiodo- and diphenyltin bis (N,N-dimethyldiselenocarbamates) are unstable to oxygen and for others; they have not been isolated as analytically pure compounds. The diselenocarbamate complexes of tintlV) obtained here are soluble in common organic solvents, except for Cl2Sn(dmdsc)2 and CH3CISn(dmdsc)2, which are less soluble in non-polar solvents. Melting points and analytical data of these complexes are summarized in Table 1. Molecular weights Molecular weights of the representative complexes were determined in chloroform using a Mechrolab Vapor Pressure Osomometer. The N,N-dimethyldiselenocarbamate complexes are essentially monomeric, while (CH3)2Sn(dedsc)2 and (CHa)2Sn(mpdsc)2 dissociate partly in solution, as shown in Table 1. I.R. and PMR spectra The i.r. spectra were measured in Nujol and in hexachlorobutadiene mulls by a Hitachi EPI-2G 15000-400 cm-1) and a Hitachi EPI-L {700-200 cm-1) Grating Spectrophotometers. The proton magnetic resonance spectra were recorded in dichloromethane, in benzene and in their mixtures on a Japan Electron Optics JNM-3H-60 Spectrometer operating at 60 MHz. Tetramethylsilane was used as an internal standard.
RESULTS AND DISCUSSION I . R . spectra
R e l e v a n t i.r. f r e q u e n c i e s of the d i s e l e n o c a r b a m a t e c o m p l e x e s a n d the t e n t a tive a s s i g n m e n t s are listed in T a b l e 2. G e n e r a l a p p e a r a n c e of the i.r. s p e c t r a of (CH3)2Sn(dmdsc)z (a), CHaC1Sn(dmdsc)2 (b), Ci2Sn(dmdsc)2 (c), a n d (CHa)2S n X ( d m d s c ) ( X = CI a n d Br) (d), are s i m i l a r to that of the c o r r e s p o n d i n g dithioc a r b a m a t e c o m p l e x e s of t i n ( I V ) , in w h i c h the d i t h i o c a r b a m a t e ligand c o o r d i n a t e s to the tin a t o m b y a b i d e n t a t e m a n n e r [ 4 , 5]. F u r t h e r m o r e , the i.r. f r e q u e n c i e s o f the d i s e l e n o c a r b a m a t e s are close to t h o s e o f the d i t h i o c a r b a m a t e s , e x c e p t that
Preparation of some diselenocarbamate complexes of tin(l V)
262 3
Table 1. Melting points, analytical data and molecular weights of the diselenocarbamate complexes of tin(IV)
Compound
M.P. (°C)
(CH3)2Sn(dmdsc)~
200-201
(CHa)2Sn(dedsc)2
147-149
(CH3)2Sn(mpdsc)~
186-187
(C2Hs)~Sn(dmdsc)2
198-199
CH3CISn(dmdsc)2
185-187
Cl2Sn(dmdsc)2
266-268
(CH3)2SnCl(dmdsc)
145-146
(CH3)zSnBr(dmdsc)
145-146
(CH3)2Sn(dmdtc) (dmdsc)
185-186
C% Found (Calcd.) 16.45 (16-63) 23.01 (22.75) 30-64 (30.81) 19.46 (19.83) 14.44 (14.07) 10.60 (11-65) 15.06 (15.06) 13.26 (13.54) 20-20 (19.88)
H% Found (Calcd.)
N% Found (Calcd.)
Mol. wt. Found (Calcd.)
3.39 (3.12) 4.29 (4.11) 3.10 (3.14) 3-86 (3.64) 2.51 (2.51) 1.87 (1-94) 3.22 (3-01) 2.77 (2.71) 4.08 (3.73)
4.67 (4-85) 4.49 (4.42) 3.87 (3.99) 4.60 (4.62) 4.41 (4.69) 4.23 (4.53) 3-50 (3.51) 3.14 (3.16) 5-80 (5.80)
567 (577) 597 (633) 671 (701) 611 (605) 592 (597)
the Se-containing vibrations o c c u r in considerably lower w a v e numbers than the S-containing ones. T h e s e observations suggest that the diselenocarbamate c o m plexes of tin(IV) h a v e a chelated structure, and therefore the tin a t o m is hexacoordinated in (a), (b) and (c), and penta-coordinated in (d). Similarly, the compounds (CH3)2Sn(dedsc)2, (CHz)2Sn(mpdsc)2, (C~Hs)2Sn(dmdsc)2 and (CH3)2Sn (dmdtc) (dmdsc) may be a s s u m e d to be hexa-coordinated. All the c o m p l e x e s in T a b l e 2 show a characteristic band in the 1 5 4 5 - 1 4 8 4 c m -~ to be assigned as v(C--- N ) mode. T h e position of this band is sensitive to the substituents on the tin atom, and also on the nitrogen atom. T h e introduction of m o r e electronegative substituents on the tin a t o m shifts the v ( C = = N ) band to a higher frequency, as is seen in the series of Cl~Sn(dmdsc)2, C H 3 C I S n ( d m d s c ) 2 and R2Sn(dmdsc)2 (R = CH3 and C2H~). This trend has already been interpreted by one of the authors in reporting the i.r. spectra of dmdtc complexes of tin(IV) [5]. On the other hand, the introduction of phenyl or ethyl group on the nitrogen a t o m shifts the v ( C - - - N ) band to a lower frequency b e c a u s e of m e s o m e r i c and/or mass effects. F o r dmdtc c o m p l e x e s of tin(IV), the both bands at near 1240 and 975 c m -~ have been associated with v(CS2) vibrations [5]. T h e corresponding bands of the d m d s c c o m p l e x e s a p p e a r at around 1225 and 870 c m -1. F r o m the mass consideration of selenium and sulfur atoms, the latter band can reasonably be assinged to v(CSe2) vibrations, while the contribution of v (CSe2) m o d e to the f o r m e r seems to be not so important. T h u s the 1225 c m -~ b a n d m a y be assinged to v~ym(N-CH3) or p ( N - C H 3 ) mode. On the basis of the similar mass consideration, the 2 5 7 - 2 1 6
* v ( C - S ) : 979 s, v ( S n - S ) : 373 s. TX = CI or Br.
222 m
216 m
225 m
517s
242 m
228 m
522s 474 w
v(Sn-Se)
554s 509 m
875s
1221 m
1535 s
(CHa)CISn (dmdsc)~
254 sh
553s 506 m
875s 856 m
1222 s
1510 s
(C2Hs)2Sn (dmdsc)2
v(Sn-X)T
[ 550s 503 m
v(Sn-C)
875s 860 m
1229 s
855s 821 m
1243 s
1267 s 1189 s
[ 882s 857 m
1484 s
(CH3)2Sn (pmdsc)z
1490 s
(CH3)~Sn (dedsc)2
1508 s
v(C-Se)
v(C-N)
(CH3)2Sn (dmdsc)z
305 s 277 s 257 m
872S 862 m
1225 s
1545 s
CI2Sn (dmdsc)2
250 s
263 s
552s 511 s
880s 860 w
1227 s
1540 s
(CH3)2SnC1 (dmdsc)
250 m
200
550s 509 s
870S 860 m
1218 s
1529 s
(CHa)2SnBr (dmdsc)
Table 2. Relevant i.r. frequencies of some diselenocarbamate complexes of tin(i V) and their assignments, c m - '
228 m
553s 515 m
883s 860 m
1248 s 1223 m
1505 s
(CH~)zSn (dmdtc) (dmdsc) *
~.
~. .--t
O
~,
.~ ).
rr
Z
IxJ
Preparation of some diselenocarbamate complexes of tin(IV)
2625
cm -1 bands can be associated with v(Sn-Se) mode; the v(Sn-S) of the dithiocarbamates appeared in the 394-356 cm -~ range [5]. Three dimethyltin complexes, (CH3)2Sn(dmdsc)z, (CH3)2Sn(dedsc)2 and (CHz)2Sn(mpdsc)2, exhibit the Vasym(Sn--C) and Vsym(Sn-C) at near 550 and 505 cm -1. Since the intensity of the latter band is not so weak, the C-Sn-C moiety is not considered to be linear. The i.r. spectrum of (CH3)2Sn(dmdtc) (dmdsc) is not necessarily superimposed by those of (CH3)2Sn(dmdtc)2 and (CHz)2Sn(dmdsc)2. This result and the sharp melting point indicate a mixed chelate complex for this compound. PMR spectra Table 3 shows the chemical shifts of N-alkyl and Sn-alkyl proton signals, and the spin-spin coupling constants between the 119Sn and CH3 protons in the tin(I V)-diselenocarbamate complexes. Table 3. Chemical shifts and coupling constants of the tin(IV)-diselenocarbamate complexes.
"r, (ppm) in CHzC12 in C6H6
Compound (CHa)2Sn(dmdsc)2 (CHz)2Sn(dedsc)2
(CH3)zSn(mpdsc)2 (C2Hs)2Sn(dmdsc)2
CHaCISn(dmdsc)2 Cl2Sn(dmdsc)2 (CHa)2SnCl(dmdsc)
(CH3)2SnBr(dmdsc)
N-CH3 Sn-CHa N-CH2 C-CHz Sn-CH3 N-CHa Sn-CH3 N-CHz Sn-CH2 C-CH3 N-CH:~ Sn-CHa N-CH3 N-CH3 Sn-CH3 N-CHa Sn-CH3
6"58 8"26 6-lit 8.65:~ 8.22 6"32 8.32 6.55 7.86? 8.46~t 6'60 8.47 6.58 6.64 8.64 6"63 8.53
7.36 7"87 6.59T 9.10t 7.88 6"73 7.95 7.35 7.43? 8-12~t § § 7"75 8.64 7.73 8.53
A* (ppm) +0-78 - 0"39 +0.48 + 0-45 - 0.34 +0"41 --0"37 +0.80 - 0.47 - 0.34
+ 1"11 0 + 1"10 0
J (119Sn-CHa) in CH2C12, (c.p.s.)
84
84 80
74 74
*A = ~'(C6H6)-~'(CH2CI2). fQuartet. ~tTriplet.
§Less soluble.
Only one sharp signal of the N-CH3 protons is observed in the dmdsc complexes. This is suggestive of the two N-CH3 groups being almost equivalent by chelation of the diselenocarbamate. J(llaSn-CH3) of (CHa)sSn(dmdsc)2 and (CH3)2Sn(dedsc)2 are both 84 c.p.s, in dichloromethane, and those of (CHa)2SnX(dmdsc) (X = CI and Br) 74 c.p.s. These values are identical with those of the corresponding dithiocarbamate complexes in chloroform. The N-CHa and N-C2H5 proton
2626
T. K A M I T A N I , H. Y A M A M O T O and T. T A N A K A
signals of the hexa-coordinated complexes in benzene are observed at higher magnetic field than in dichloromethane ( A = + 0 . 4 1 - +0-80ppm), while the signals of the Sn-CH3 and Sn-C2H5 protons in benzene appeza~at lower magnetic field than in dichloromethane (A = - - 0 . 3 4 - - - 0 . 4 7 p p m ) . In the case of the penta-coordinated complexes, (CH3)2SnX(dmdsc), large positive values (+1.10 +1-11 ppm) are observed for N-CH3 protons. On the other hand, the chemical shifts of the Sn-CH3 protons remain constant when the solvent is changed from benzene to dichloromethane, in contrast with the results for the hexa-coordinated complexes. These solvent effects in benzene are analogous to those observed in the pmr spectra of N,N-dimethyldithiocarbamate complexes of tin(IV)[4,5]. It is therefore concluded that in solution R2Sn[Se2CNR~]2 (R, R' = CHa, C2H5) and (CH3)zSnX[Se2CN (CH3)z] (X = CI, Br) have the similar configurations to (CH3)2Sn[S2CN (CHa)2]z and (CH3)2SnX[S2CN (CH3)z], respectively, and the benzene induced solvent shifts are due to a benzene-solute stereospecific interaction at electron-deficient nitrogen atom [4, 5]. The existence of the mixed chelate is also supported from the NMR study in solution. The spectrum of (CH3)zSn(dmdtc)(dmdsc) in dichloromethane shows a broad Sn-CH3 proton signal at room temperature (Fig. I), which suggests the ligand exchange in solution at the NMR time scale. A t - 6 0 ° C , however, the t"t(3
i
6
i
I
7
~
¢0
eJ
~0
(30
(D
co
i
8
i
ot
25 °
ot
- 60 °
L
9
ppm(r)
Fig. 1. The PMR spectra of (CH3)2Sn(dmdtc)(dmdsc) in dichloromethane (Internal standard, TMS).
Preparation of some diselenocarbamate complexes of tin(IV)
2627
methyl proton signal is split into three at 8.56, 8.42 and 8.28ppm (Fig. 1), of which the signals at the highest and lowest field can be assigned independently to those of (CH3)zSn(dmdtc)2 and (CHD2Sn(dmdsc)z. Then the middle one is assigned to the Sn-CHz protons of the mixed chelate. It is noted that there are only two N - C H 3 proton signals even when the ligand exchanges are very slow among the three species, (CH3)zSn(dmdsc)z, (CH3)2Sn(dmdsc)(dmdtc) and (CH3)zSn(dmdtc)2. This result may be due to the CHz (a) and CH3 (D) protons being magnetically equivalent to the CH3 (B) and CH3 (c) protons, respectively, in the following species:
CHn(A)~ N ....
CH,~)/
.,~,/,Se~ I --Snf
. Se..,= /CHn(A) "",'~C :--:,-:-'N./"
Cf:
"k S e / I \ s e 7
,.S~.
CH#e).
I/
\CH,~)
s,.~
.... c./,,
CH.~B~. / -- "'ks./I c..~ok.,.. --N
.CH,(C) .... ../
~s/"
_~.s.
\c..~c~
I/S~.
/CH.ID)
.... CE~ ~ ~Sn
CH.5(D) '/''/
S
s C.... N
I
S
CHAD)
On the other hand, a dichloromethane solution of (CH3)2Sn(dmdsc)2 and (CH3)2Sn(mpdtc)2(mpdtc: S2CN (CH3) (CnH.~)) at the mole ratio of 1/1 shows two doublets of the N - C H 3 and three Sn-CH3 proton signals at - 60°C, although at room temperature two N - C H 3 and three Sn-CH3 proton signals are observed (Fig. 2). The higher field doublet is tentatively assigned to the CHa (A) and CH3 (B') protons, and the lower one to the CH3 tc') and CH3 tD') protons in the following formula:
CH~(A)
CH,(A)/
Se~l
.... "~"Se /
CH~(B')~ ....
CH~(D').
~N---C
e
CHelA)
SI ~Se/~
C.... N~CH~,(A }
,/.S~ ""
i
,~.S.
I
/
"" ~ S . ~
S.~ .CH~C') / "'~'b'c .... N /
S,.~,
--CH~(D')
"" c .... . /
2628
T. K A M I T A N I , H. Y A M A M O T O and T. T A N A K A o
to tO
to f¢)
at 25 °
tb
¢0 ub
rt)
~b
to
~
~
co
~
t'xl
to
Po
.%
i, r
Qb
\
L "i U
/
'\
" 1
'
of - 60 °
t i
6
i
i
i
i
7
8 ppm
t
i
9
(r)
Fig. 2. The PMR spectra of (CHa)2Sn(dmdsc)2-(CH3)zSn(mpdtc)2 mixture at the mole ratio of 1/1 in dichloromethane (Internal standard, TMS).
The splits of the CH3 (A) and CH3 tB'~, and also CH3 (c') and CH3 (D') proton signals may be resulted from the difference in coordination ability between dmdsc and mpdtc. It is therefore concluded from these N M R observations that the coordination ability of the dmdsc to the tin atom is virtually invariant with that of the dmdtc.
PREPARATION OF SOME DISELENOCARBAMATE COMPLEXES OF TIN(IV) A N D THEIR I.R. A N D PMR SPECTRA T A K A S H I K A M I T A N I , H I R O M I T S U Y A M A M O T O and T O S H I O T A N A K A Department of Applied Chemistry, Osaka University, Yamada-kami, Suita, Osaka, Japan (Received 16 December 1969) A b s t r a c t - S e v e r a l N,N-dimethyldiselenocarbamate complexes of tin(IV), RaSn(dmdsc)2 (R = C H 3 and C2H5), CH3CISn(dmdsc)2, CI2Sn(dmdsc)2 and (CH3)2SnX(dmdsc) i X = CI and Br), dimethyltin bis(N,N-diethyldiselenocarbamate) and bis(N-methyI-N-phenyldiselenocarbamate) have been prepared. The i.r. and pmr spectra of the dmdsc complexes suggest the chelation of diselenocarbamate group. The N-alkyl or Sn-alkyl proton signals of all the complexes show characteristic benzeneinduced solvent shifts, which are analogous to the case o f N,N-dimethyldithiocarbamate(dmdtc) complexes of tin(IV). A mixed chelate compound, (CH3)2Sn(dmdtc)(dmdsc), has also been isolated. The pmr spectrum indicates that difference in the coordination power toward tin atom is hardly discernible between diselenocarbamate and dithiocarbamate. INTRODUCTION
N,N-DIALKYLDITHIOCARBAMATE complexes of transition and non-transition metals have extensively been studied by many workers. However, the study of diselenocarbamate complexes have been limited to those of some transition metals [ 1-3]. It seems to be of interest to compare the coordination abilities of sulfur and selenium to metal atoms. This paper reports the preparation of several N,Ndimethyl-, N,N-diethyl- and N-methyl-N-phenyl-diselenocarbamate complexes of tin(IV), and their i.r. and pmr spectra. The spectroscopic results are discussed in comparing with those of the corresponding dithiocarbamates, which have previously been reported by one of the present authors [4, 5], and the configuration of the representative complexes is also described. EXPERIMENTAL Preparation (CHa)2Sn(dmdsc)2, (C2Hs)2Sn(dmdsc)2 and CI2Sn(dmdsc)z (dmdsc: Se~CN (CH3)2). A solution of CSe216] 112.4 m-mole) in dioxane was added dropwise to an aqueous solution containing N a O H ( 12.4 m-mole) and (CHa)2NH ( 12.4 m-mole) at --10°C under dry nitrogen, and the mixture was stirred for about ! hr at room temperature. N a O H + ( C H a ) 2 N H + C S e 2 - - - * Na[Se2CN(CHz)2]+HzO. This solution was added to an aqueous solution of (CHz)~SnCI2, (C2Hs)2SnCI2 or SnCI4 (6.2 m-mole), and followed by stirring for 30 min to give white precipitates of dimethyltin, diethyltin or dichlorotin bis(N,N-dimethyldiseleno1. 2. 3. 4. 5.
D. Barnard and D. T. Woodbridge, J. chem. Soc. 2922 (1961). K. A. Jensen and V. Krishnan, Acta chem. scand. 21, 1988 (1967). C. Furlani, E. Cervone and F. D. Camessei, Inorg. Chem. 7, 265 (1968). M. Honda, Y. Kawasaki and T. Tanaka, Tetrahedron Lett. 3313 (1967). M. Honda, M. Komura, Y. Kawasaki, T. Tanaka and R. Okawara, J. inorg, nucl. Chem. 30, 3231 (1968). 6. D . J . G . lves, R. W. Pittman and W. Wardlaw, J. chem. Soc. 1080 (1967). 2621
2622
T. KAMITANI, H. YAMAMOTO and T. TANAKA
carbamate) almost quantitatively. The former two were recrystallized from carbon tetrachloride, and the latter from chlorobenzene. (CH3)zSn(dedsc)2 and (CHa)2Sn(mpdsc)2 (dedsc: Se2CN(C2H5)2, mpdsc: Se2CN(CHa)(C6H5)). A solution of sodium N,N-diethyldiselenocarbamate or N-methyl-N-phenyldiselenocarbamate was prepared by the reaction of CSe2 in dioxane with (C2Hs)2NH or (CHz)(C6Hs)NH in aqueous NaOH solution. These solutions reacted similarly with (CH3)2SnCIz in water to yield dimethyltin bis(N,N-diethyldiselenocarbamate) and bis(N-methyl-N-phenyldiselenocarbamate), respectively, which were recrystallized from carbon tetrachloride. CHaCISn(dmdsc)2. To a solution of methylstannoic acid (6"2 m-mole) in I N-HCI was added dropwise a solution of Na{dmdsc) in water-dioxane, and the mixture was stirred for 30 min to give white precipitates of methylchlorotin bistN,N-dimethyldiselenocarbamate), which was recrystallized from o-dichlorobenzene. CHaSnOOH + 3HCI + 2Na [SesCN (CH3)2] -* CH3CISn [Se2CN (CH3)212+ 2NaCI + 2HzO. (CH3)2SnX(dmdsc) (X = CI and Br). Equimolar amounts of (CH3)2SnX2 and (CH3)2Sn(dmdsc)2 were dissolved in carbon tetrachloride, and the solution was evaporated to dryness under reduced pressure to give quantitatively dimethylhalogenotin N,N-dimethyldiselenocarbamates, which were recrystallized from carbon tetrachloride. (CHa)2SnX2 + (CHa)2Sn[Se2CN (CHa)2]z -'->2(CHa)zSnX[Se2CN(CH3)2]. (CH3)2Sn(dmdtc) (dmdsc) (dmdtc: S2CN(CH3)2). This compound was obtained by vacuum evaporation of a carbon tetrachloride solution containing equimolar amounts of (CH3)2Sn(dmdtc)2 and (CH3)~Sn(dmdsc)2, and recrystallized from carbon tetrachloride. Dibromo-, diiodo- and diphenyltin bis (N,N-dimethyldiselenocarbamates) are unstable to oxygen and for others; they have not been isolated as analytically pure compounds. The diselenocarbamate complexes of tintlV) obtained here are soluble in common organic solvents, except for Cl2Sn(dmdsc)2 and CH3CISn(dmdsc)2, which are less soluble in non-polar solvents. Melting points and analytical data of these complexes are summarized in Table 1. Molecular weights Molecular weights of the representative complexes were determined in chloroform using a Mechrolab Vapor Pressure Osomometer. The N,N-dimethyldiselenocarbamate complexes are essentially monomeric, while (CH3)2Sn(dedsc)2 and (CHa)2Sn(mpdsc)2 dissociate partly in solution, as shown in Table 1. I.R. and PMR spectra The i.r. spectra were measured in Nujol and in hexachlorobutadiene mulls by a Hitachi EPI-2G 15000-400 cm-1) and a Hitachi EPI-L {700-200 cm-1) Grating Spectrophotometers. The proton magnetic resonance spectra were recorded in dichloromethane, in benzene and in their mixtures on a Japan Electron Optics JNM-3H-60 Spectrometer operating at 60 MHz. Tetramethylsilane was used as an internal standard.
RESULTS AND DISCUSSION I . R . spectra
R e l e v a n t i.r. f r e q u e n c i e s of the d i s e l e n o c a r b a m a t e c o m p l e x e s a n d the t e n t a tive a s s i g n m e n t s are listed in T a b l e 2. G e n e r a l a p p e a r a n c e of the i.r. s p e c t r a of (CH3)2Sn(dmdsc)z (a), CHaC1Sn(dmdsc)2 (b), Ci2Sn(dmdsc)2 (c), a n d (CHa)2S n X ( d m d s c ) ( X = CI a n d Br) (d), are s i m i l a r to that of the c o r r e s p o n d i n g dithioc a r b a m a t e c o m p l e x e s of t i n ( I V ) , in w h i c h the d i t h i o c a r b a m a t e ligand c o o r d i n a t e s to the tin a t o m b y a b i d e n t a t e m a n n e r [ 4 , 5]. F u r t h e r m o r e , the i.r. f r e q u e n c i e s o f the d i s e l e n o c a r b a m a t e s are close to t h o s e o f the d i t h i o c a r b a m a t e s , e x c e p t that
Preparation of some diselenocarbamate complexes of tin(l V)
262 3
Table 1. Melting points, analytical data and molecular weights of the diselenocarbamate complexes of tin(IV)
Compound
M.P. (°C)
(CH3)2Sn(dmdsc)~
200-201
(CHa)2Sn(dedsc)2
147-149
(CH3)2Sn(mpdsc)~
186-187
(C2Hs)~Sn(dmdsc)2
198-199
CH3CISn(dmdsc)2
185-187
Cl2Sn(dmdsc)2
266-268
(CH3)2SnCl(dmdsc)
145-146
(CH3)zSnBr(dmdsc)
145-146
(CH3)2Sn(dmdtc) (dmdsc)
185-186
C% Found (Calcd.) 16.45 (16-63) 23.01 (22.75) 30-64 (30.81) 19.46 (19.83) 14.44 (14.07) 10.60 (11-65) 15.06 (15.06) 13.26 (13.54) 20-20 (19.88)
H% Found (Calcd.)
N% Found (Calcd.)
Mol. wt. Found (Calcd.)
3.39 (3.12) 4.29 (4.11) 3.10 (3.14) 3-86 (3.64) 2.51 (2.51) 1.87 (1-94) 3.22 (3-01) 2.77 (2.71) 4.08 (3.73)
4.67 (4-85) 4.49 (4.42) 3.87 (3.99) 4.60 (4.62) 4.41 (4.69) 4.23 (4.53) 3-50 (3.51) 3.14 (3.16) 5-80 (5.80)
567 (577) 597 (633) 671 (701) 611 (605) 592 (597)
the Se-containing vibrations o c c u r in considerably lower w a v e numbers than the S-containing ones. T h e s e observations suggest that the diselenocarbamate c o m plexes of tin(IV) h a v e a chelated structure, and therefore the tin a t o m is hexacoordinated in (a), (b) and (c), and penta-coordinated in (d). Similarly, the compounds (CH3)2Sn(dedsc)2, (CHz)2Sn(mpdsc)2, (C~Hs)2Sn(dmdsc)2 and (CH3)2Sn (dmdtc) (dmdsc) may be a s s u m e d to be hexa-coordinated. All the c o m p l e x e s in T a b l e 2 show a characteristic band in the 1 5 4 5 - 1 4 8 4 c m -~ to be assigned as v(C--- N ) mode. T h e position of this band is sensitive to the substituents on the tin atom, and also on the nitrogen atom. T h e introduction of m o r e electronegative substituents on the tin a t o m shifts the v ( C = = N ) band to a higher frequency, as is seen in the series of Cl~Sn(dmdsc)2, C H 3 C I S n ( d m d s c ) 2 and R2Sn(dmdsc)2 (R = CH3 and C2H~). This trend has already been interpreted by one of the authors in reporting the i.r. spectra of dmdtc complexes of tin(IV) [5]. On the other hand, the introduction of phenyl or ethyl group on the nitrogen a t o m shifts the v ( C - - - N ) band to a lower frequency b e c a u s e of m e s o m e r i c and/or mass effects. F o r dmdtc c o m p l e x e s of tin(IV), the both bands at near 1240 and 975 c m -~ have been associated with v(CS2) vibrations [5]. T h e corresponding bands of the d m d s c c o m p l e x e s a p p e a r at around 1225 and 870 c m -1. F r o m the mass consideration of selenium and sulfur atoms, the latter band can reasonably be assinged to v(CSe2) vibrations, while the contribution of v (CSe2) m o d e to the f o r m e r seems to be not so important. T h u s the 1225 c m -~ b a n d m a y be assinged to v~ym(N-CH3) or p ( N - C H 3 ) mode. On the basis of the similar mass consideration, the 2 5 7 - 2 1 6
* v ( C - S ) : 979 s, v ( S n - S ) : 373 s. TX = CI or Br.
222 m
216 m
225 m
517s
242 m
228 m
522s 474 w
v(Sn-Se)
554s 509 m
875s
1221 m
1535 s
(CHa)CISn (dmdsc)~
254 sh
553s 506 m
875s 856 m
1222 s
1510 s
(C2Hs)2Sn (dmdsc)2
v(Sn-X)T
[ 550s 503 m
v(Sn-C)
875s 860 m
1229 s
855s 821 m
1243 s
1267 s 1189 s
[ 882s 857 m
1484 s
(CH3)2Sn (pmdsc)z
1490 s
(CH3)~Sn (dedsc)2
1508 s
v(C-Se)
v(C-N)
(CH3)2Sn (dmdsc)z
305 s 277 s 257 m
872S 862 m
1225 s
1545 s
CI2Sn (dmdsc)2
250 s
263 s
552s 511 s
880s 860 w
1227 s
1540 s
(CH3)2SnC1 (dmdsc)
250 m
200
550s 509 s
870S 860 m
1218 s
1529 s
(CHa)2SnBr (dmdsc)
Table 2. Relevant i.r. frequencies of some diselenocarbamate complexes of tin(i V) and their assignments, c m - '
228 m
553s 515 m
883s 860 m
1248 s 1223 m
1505 s
(CH~)zSn (dmdtc) (dmdsc) *
~.
~. .--t
O
~,
.~ ).
rr
Z
IxJ
Preparation of some diselenocarbamate complexes of tin(IV)
2625
cm -1 bands can be associated with v(Sn-Se) mode; the v(Sn-S) of the dithiocarbamates appeared in the 394-356 cm -~ range [5]. Three dimethyltin complexes, (CH3)2Sn(dmdsc)z, (CH3)2Sn(dedsc)2 and (CHz)2Sn(mpdsc)2, exhibit the Vasym(Sn--C) and Vsym(Sn-C) at near 550 and 505 cm -1. Since the intensity of the latter band is not so weak, the C-Sn-C moiety is not considered to be linear. The i.r. spectrum of (CH3)2Sn(dmdtc) (dmdsc) is not necessarily superimposed by those of (CH3)2Sn(dmdtc)2 and (CHz)2Sn(dmdsc)2. This result and the sharp melting point indicate a mixed chelate complex for this compound. PMR spectra Table 3 shows the chemical shifts of N-alkyl and Sn-alkyl proton signals, and the spin-spin coupling constants between the 119Sn and CH3 protons in the tin(I V)-diselenocarbamate complexes. Table 3. Chemical shifts and coupling constants of the tin(IV)-diselenocarbamate complexes.
"r, (ppm) in CHzC12 in C6H6
Compound (CHa)2Sn(dmdsc)2 (CHz)2Sn(dedsc)2
(CH3)zSn(mpdsc)2 (C2Hs)2Sn(dmdsc)2
CHaCISn(dmdsc)2 Cl2Sn(dmdsc)2 (CHa)2SnCl(dmdsc)
(CH3)2SnBr(dmdsc)
N-CH3 Sn-CHa N-CH2 C-CHz Sn-CH3 N-CHa Sn-CH3 N-CHz Sn-CH2 C-CH3 N-CH:~ Sn-CHa N-CH3 N-CH3 Sn-CH3 N-CHa Sn-CH3
6"58 8"26 6-lit 8.65:~ 8.22 6"32 8.32 6.55 7.86? 8.46~t 6'60 8.47 6.58 6.64 8.64 6"63 8.53
7.36 7"87 6.59T 9.10t 7.88 6"73 7.95 7.35 7.43? 8-12~t § § 7"75 8.64 7.73 8.53
A* (ppm) +0-78 - 0"39 +0.48 + 0-45 - 0.34 +0"41 --0"37 +0.80 - 0.47 - 0.34
+ 1"11 0 + 1"10 0
J (119Sn-CHa) in CH2C12, (c.p.s.)
84
84 80
74 74
*A = ~'(C6H6)-~'(CH2CI2). fQuartet. ~tTriplet.
§Less soluble.
Only one sharp signal of the N-CH3 protons is observed in the dmdsc complexes. This is suggestive of the two N-CH3 groups being almost equivalent by chelation of the diselenocarbamate. J(llaSn-CH3) of (CHa)sSn(dmdsc)2 and (CH3)2Sn(dedsc)2 are both 84 c.p.s, in dichloromethane, and those of (CHa)2SnX(dmdsc) (X = CI and Br) 74 c.p.s. These values are identical with those of the corresponding dithiocarbamate complexes in chloroform. The N-CHa and N-C2H5 proton
2626
T. K A M I T A N I , H. Y A M A M O T O and T. T A N A K A
signals of the hexa-coordinated complexes in benzene are observed at higher magnetic field than in dichloromethane ( A = + 0 . 4 1 - +0-80ppm), while the signals of the Sn-CH3 and Sn-C2H5 protons in benzene appeza~at lower magnetic field than in dichloromethane (A = - - 0 . 3 4 - - - 0 . 4 7 p p m ) . In the case of the penta-coordinated complexes, (CH3)2SnX(dmdsc), large positive values (+1.10 +1-11 ppm) are observed for N-CH3 protons. On the other hand, the chemical shifts of the Sn-CH3 protons remain constant when the solvent is changed from benzene to dichloromethane, in contrast with the results for the hexa-coordinated complexes. These solvent effects in benzene are analogous to those observed in the pmr spectra of N,N-dimethyldithiocarbamate complexes of tin(IV)[4,5]. It is therefore concluded that in solution R2Sn[Se2CNR~]2 (R, R' = CHa, C2H5) and (CH3)zSnX[Se2CN (CH3)z] (X = CI, Br) have the similar configurations to (CH3)2Sn[S2CN (CHa)2]z and (CH3)2SnX[S2CN (CH3)z], respectively, and the benzene induced solvent shifts are due to a benzene-solute stereospecific interaction at electron-deficient nitrogen atom [4, 5]. The existence of the mixed chelate is also supported from the NMR study in solution. The spectrum of (CH3)zSn(dmdtc)(dmdsc) in dichloromethane shows a broad Sn-CH3 proton signal at room temperature (Fig. I), which suggests the ligand exchange in solution at the NMR time scale. A t - 6 0 ° C , however, the t"t(3
i
6
i
I
7
~
¢0
eJ
~0
(30
(D
co
i
8
i
ot
25 °
ot
- 60 °
L
9
ppm(r)
Fig. 1. The PMR spectra of (CH3)2Sn(dmdtc)(dmdsc) in dichloromethane (Internal standard, TMS).
Preparation of some diselenocarbamate complexes of tin(IV)
2627
methyl proton signal is split into three at 8.56, 8.42 and 8.28ppm (Fig. 1), of which the signals at the highest and lowest field can be assigned independently to those of (CH3)zSn(dmdtc)2 and (CHD2Sn(dmdsc)z. Then the middle one is assigned to the Sn-CHz protons of the mixed chelate. It is noted that there are only two N - C H 3 proton signals even when the ligand exchanges are very slow among the three species, (CH3)zSn(dmdsc)z, (CH3)2Sn(dmdsc)(dmdtc) and (CH3)zSn(dmdtc)2. This result may be due to the CHz (a) and CH3 (D) protons being magnetically equivalent to the CH3 (B) and CH3 (c) protons, respectively, in the following species:
CHn(A)~ N ....
CH,~)/
.,~,/,Se~ I --Snf
. Se..,= /CHn(A) "",'~C :--:,-:-'N./"
Cf:
"k S e / I \ s e 7
,.S~.
CH#e).
I/
\CH,~)
s,.~
.... c./,,
CH.~B~. / -- "'ks./I c..~ok.,.. --N
.CH,(C) .... ../
~s/"
_~.s.
\c..~c~
I/S~.
/CH.ID)
.... CE~ ~ ~Sn
CH.5(D) '/''/
S
s C.... N
I
S
CHAD)
On the other hand, a dichloromethane solution of (CH3)2Sn(dmdsc)2 and (CH3)2Sn(mpdtc)2(mpdtc: S2CN (CH3) (CnH.~)) at the mole ratio of 1/1 shows two doublets of the N - C H 3 and three Sn-CH3 proton signals at - 60°C, although at room temperature two N - C H 3 and three Sn-CH3 proton signals are observed (Fig. 2). The higher field doublet is tentatively assigned to the CHa (A) and CH3 (B') protons, and the lower one to the CH3 tc') and CH3 tD') protons in the following formula:
CH~(A)
CH,(A)/
Se~l
.... "~"Se /
CH~(B')~ ....
CH~(D').
~N---C
e
CHelA)
SI ~Se/~
C.... N~CH~,(A }
,/.S~ ""
i
,~.S.
I
/
"" ~ S . ~
S.~ .CH~C') / "'~'b'c .... N /
S,.~,
--CH~(D')
"" c .... . /
2628
T. K A M I T A N I , H. Y A M A M O T O and T. T A N A K A o
to tO
to f¢)
at 25 °
tb
¢0 ub
rt)
~b
to
~
~
co
~
t'xl
to
Po
.%
i, r
Qb
\
L "i U
/
'\
" 1
'
of - 60 °
t i
6
i
i
i
i
7
8 ppm
t
i
9
(r)
Fig. 2. The PMR spectra of (CHa)2Sn(dmdsc)2-(CH3)zSn(mpdtc)2 mixture at the mole ratio of 1/1 in dichloromethane (Internal standard, TMS).
The splits of the CH3 (A) and CH3 tB'~, and also CH3 (c') and CH3 (D') proton signals may be resulted from the difference in coordination ability between dmdsc and mpdtc. It is therefore concluded from these N M R observations that the coordination ability of the dmdsc to the tin atom is virtually invariant with that of the dmdtc.