Molecular addition compounds of tin (IV) chloride—II

J. Inorg. Nucl. Chem., 1964, Vol. 26, pp. 2185 to 2190. Pergamon Press Ltd. Printed in Northern Ireland

MOLECULAR ADDITION COMPOUNDS OF TIN (IV) CHLORIDE--II PREPARATION AND INFRARED SPECTRA OF THE COMPLEXES OF STANNIC CHLORIDE WITH ALKYL AND ARYL SUBSTITUTED UREAS R. C. AGGARWAL a n d P. P. SINGH Department of Chemistry, Lucknow University, Lucknow (India) (Received 16 December 1963; in revisedform 6 May 1964)

Abstract---Co-ordination complexes of tin (IV) chloride with tetramethyl urea 1,3-dimethyl urea, 1,l-dimethyl urea and monophenyl urea have been prepared. They are of the type SNC14-2Donor, as shown by indicator titration of stannic chloride against the donor molecules in dichloroethane. Molecular weight determinations by freezing-point depression and conductivity measurements in nitromethane show that they are monomeric molecular addition compounds. The infra-red spectra indicate oxygen to metal bonding and the relative values of the shift in 7(C=O) and the melting points of the adducts indicate the following order for the donor strength: Tetramethyl urea > 1,3-dimethyl urea > 1,1-dimethyl urea > monophenyl urea. IN a previous c o m m u n i c a t i o n ~1~ the m o l e c u l a r a d d i t i o n c o m p o u n d s o f tin (IV) chloride with a n u m b e r o f a m i d e s were investigated, a n d o x y g e n - m e t a l b o n d s were f o u n d in all these c o m p o u n d s . M e t a l - o x y g e n b o n d i n g has also been shown by the infra-red spectral m e a s u r e m e n t s o f BYSTROV~ on SnC14.2CO(NH~) ~ a n d o f RIVESTtD~ on the m o l e c u l a r a d d i t i o n c o m p o u n d s o f Ti(IV) chloride with alkyl- a n d aryl-substituted ureas. I n the present p a p e r the investigations have been e x t e n d e d to the m o l e c u l a r a d d i t i o n c o m p o u n d s o f tin (IV) c h l o r i d e with alkyl- a n d aryl-substituted ureas. T h e infra-red measurements again show o x y g e n - m e t a l b o n d s in these complexes. EXPERIMENTAL Materials and methods

Reagent grade stannic chloride was purified by the method of HILDEBRANDand CASTERt41 and redistiUed, the middle fraction was used for our experiments. Reagent grade tetramethyl urea (TMU), 1,3-dimethyl urea (1,3-DMU) and 1,1-dimethyl urea (1,1-DMU) were used after drying over phosphorus pentoxide. Monophenyl urea (MPU) was prepared and purified as described by MANN a n d lAUNDERS, t~l

Solvents were dried before use, and the water-sensitive compounds were handled in a dry box. ta~ R. C. AGGARWALand P. P. SINOH. Z. Anorg. Chem. In press. t2~ D . S. BYSTROV, T . N . SUMAROKOVA a n d V. M . FILIMONOV,

Opt. Spektrosk. 9,

4 6 0 (1960).

tD~R. RIVEST, Can. J. Chem. 40, 2234 (1962). c4~j. H. HILDEBRANDand J. M. CASTER, .Jr.Amer. Chem. Soe. $4, 3592 (1932). ts~ e. G. MANN and B. C. SAUNDERS,Practical Organic Chemistry, p. 96, Longrnans Green London (1953). 10 2185

2186

R . C . AGGARWALand P. P. SINGH

The infra-red spectra of the donor molecules and of the adducts were recorded on a Perkin-Elmer Infra Cord, fitted with sodium chloride optics.

Preparation of the adducts The adducts were prepared in a dry-box by mixing in suitable molar proportions a solution (~10%) of the reactants in chloroform or petroleum ether. The composition of the adducts corresponded to SNC14"2Donor irrespective of which component was initially in excess. Stannic chloride-tetramethyl urea. On mixing petroleum ether (boiling range 80-90°C) solutions of stannic chloride and TMU a white precipitate separated immediately. The compound was filtered and washed several times with petroleum ether, and finally with ether. The compound was recrystallized from chloroform and dried in vacuum desiccator. It is a white nonhygroscopic solid, m.p. 205°C. Stannic chloride-l,3 DMU. On mixing solutions of stannic chloride and 1,3 DMU in chloroform a viscous layer first separated, which on standing changed into a white solid; this was filtered and washed several times with chloroform. The compound was recrystallized from nitromethane and dried in vacuum desiccator. It is non-hygroscopic crystalline solid, m.p. 195°C. Stannic chloride-l,1 DMU. On mixing solutions of stannic chloride and 1,1-DMU in chloroform and shaking vigorously a viscous layer appeared. It was separated, scratched first with carbon tetrachloride then with ether, and dried in vacuo, when it changed into a crystalline solid. When the solid compound was treated with chloroform, the viscous layer again appeared; this was dried as before, the process was repeated three to four times to obtain the pure compound. It is a non-hygroscopic, dull-coloured solid, m.p. 175°C. Stannic chloride-MPU. On mixing a hot solution of MPU in chloroform with solution of stannic chloride in chloroform and shaking vigorously, a white crystalline solid separated, which was filtered and washed several times with chloroform, and finally dried in vacuo. It is an extremely hygroscopic solid, m.p., 65°C. RESULTS Analysis o f the adducts The a d d u c t s were analysed for tin, chloride, a n d nitrogen as described earlier, (1) with the results given in T a b l e 1. TABLE

1

i

Compound 1. 2. 3. 4.

SnCI4"2TMU SnCI4"2DMU(1,3) SnCI4.2DMU(1,1) SnC14"2MPU

Tin Calc.(%) 24"91 27"18 27'18 22'28

Obs.(%) 24.94 27.20 27.26 22.22

Chloride Calc.(%) 28.82 32'51 33.28 26.65

Obs.(%) 28"49 32'44 33.01 26"54

Nitrogen Calc.(%) 11"36 12"82 12.82 10.51

Obs.(%) 11"42 12"88 12.91 10.48

Indicator titration o f stannic chloride versus donors. I n d i c a t o r titrations were carried o u t in d i c h l o r o e t h a n e (in the case o f M P U in nitro methane), as described elsewhere, (1) using Crystal Violet as indicator, with the results given in T a b l e 2. T h e results confirm t h a t the a d d u c t s possess the general f o r m u l a SNC14.2 D o n o r . W h e n s t a n d a r d solutions o f stannic chloride a n d substituted ureas were m i x e d in various m o l a r ratios a n d the unreacted c o m p o n e n t was titrated, the m o l a r ratio in which stannic chloride a n d the d o n o r s reached was always f o u n d to be - ~ 1 : 2 . Molecular weight determinations The m o l e c u l a r weights o f the a d d u c t s were d e t e r m i n e d b y freezing p o i n t depression with the results given in Table 3, showing t h e m to be m o n o m e r i c .

Molecular addition compounds of tin (IV) chloride--II TABLE 2

(a)

STANNIC CHLORIDE--TMU

SnCI~(A) (ml) 0.0506M

TMU (B) (ml) 0.1008M

Mole ratio B/A

1'00 2.00 3,00

1.02 2.03 3.07

2.03 2-00 2-01

(b)

STANNIC CHLORIDE--l,3DMU

SnC14(A) (ml) 0-0506M

1,3 DMU (B) (ml) 0.1M

Mole ratio B/A

1'0 2.0 3.0

1.01 2-02 3-03

1.996 1.996 1'995

STANNIC CHLORIDE--l,1 DMU

(C)

SnC14(A) (ml) 0"0253M

1,1 DMU (ml)

0-0511M

Mole ratio B/A

1.0

1"0

2.01

2.0 3.0

2'0 3"0

2.01 2.01

(d)

STANNIC CHLORIDE--MPU

SnC14(A) (ml) 0.0506M

MPU (B) (ml) 0.1007M

Mole ratio B/A

1-0 2.0 3'0

1"0 2.0 3-06

1.99 1"99 1-94

TABLE 3

Compounds 1. SNC14-2TMU 2. SNC14"2DMU(I,3) 3. SNC14'2DMU(1,1)

Molecular weight (found)

Molecular weight (calc.)

480'6 421'9 426'0

492-7 438.7 436-7

TABLE 4.--MOLAR CONDUCTANCE OF NITROMETHANE AT 30°C = 0.5917 Concentration of adduct

Molar conductance at 30°C

M/64 M/128 M/256 M/512 M/1024

5-655 6.118 6.896 10.94 11.44

2187

2188

R . C . AGGARWALand P. P. S]NGI-I

Conductivity measurements The conductivity o f the adducts was determined in nitromethane; for the sake o f brevity the results for only one adduct, viz. SnC142DMU-(1,3 ), are given in the Table 4. These results show them to be true molecular addition compounds. Infra-red spectra The assignments o f the various bands in the infra-red spectra o f the substituted ureas and o f their molecular addition c o m p o u n d s are given in the Table 5; the spectra are illustrated in Figs. 1-3. TABLE 5 Assignments

Donor

Adduct

Shift (cm-X)*

1650 (s) 1485 (s) 1365 (s)

TMU (CC14 soln) 1650 (s) -1363 (s)

SnC142TMU (emulsion in Nujol) 1569 (s) 1513 (s) 1365 (s)

--81

DMU(1,3) (emulsion in Nujol)

DMU(I,3) (soln. CHCla)

SnC1,2DMU(1,3) (emulsion in Nujol)

3325 (s) 1625 (s) 1575 (s) 1265 (m) 1170 (m)

3325 (s) 1642 (s) 1560 (s) 1256 (m) 1165 (m)

3325 (s) 1575 (s) --1155 (m)

TMU (pure) C = O st C---N st C--N st

N--H (st) C=-O (st) NH deformation NH rocking NH rocking

DMU(1,1) (emulsion in Nujol) N - - H (st) N - - H (st) C------O(st) NH deformation NH rocking NH rocking

3150 (s) 3355 (s) 1650 (sh)t 1590 (s) 1270 (s) 1090 (s)

--67

DMU(1,1) SnC142DMU(1,1) (soln. C~H2CI~) (emulsion in Nujol) --1650 (s) 1584 (s) ---

3300 (s) 3400 (s) 1620 (s) 1588 (s) 1268 (m) 1071 (m)

-30

s = strong, sh = shoulder, m = medium, st = stretching. * Note: Shifts in C = O frequency have been calculated from the value of C~------Odonors in solution. J" The shoulder at 1650 cm-1 assigned to the C ~ O stretching frequency in the case of 1,1-DMU in nujol is well resolved into a strong band when the spectrum is taken in KBr. DISCUSSION COOKt~ has discussed the d o n o r characteristics o f the carbonyl g r o u p in the amides in terms o f the ionization potential and the carbonyl stretching frequency ( v C ~ O ) , and has presented data to show that with alkyl substitution in the amides the electron density at the carbonyl oxygen increases, resulting in decreases in the C = O stretching frequency and the ionization potential (IP). We have arrived at similar conclusions f r o m our investigations o f the addition c o m p o u n d s o f stannic f~ D. CooK, J. Amer. Chem. Soc. 80, 49 (1958).

Molecular addition compounds of tin (IV) chloride--I( - -

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2190

R.C. AGGARWALand P. P. StNOH

chloride with amides, and have explained the results of our infra-red measurements on the basis of coordination of the amides through oxygen. Application of the inductive and mesomeric effects leads one to expect that the electron density at the carbonyl oxygen should decrease in the order T M U > 1, 3-DMU > 1, 1-DMU > MPU; consequently the donor activity of the Lewis bases and the stability of the adducts should decrease in the same order. Reference to Table 5 shows that these expectations have been experimentally realized. Our infra-red spectra of the adducts (Figs. 1-3) and the assignments in Table 5 show a negative shift of the carbonyl stretching frequency and a positive shift of the C - - N stretching frequency, indicating co-ordination of the donor molecule to stannic chloride through oxygen. This is also clear from the retention of the N - - H stretching band in SnC14.2DMU(1, 3) and the positive shift of the band in SnC14.2DMU(I, 1). As would be expected, T M U and its adduct show no band in this region. This observation is in good agreement with that of PENLANDet al. ta) on the urea complexes. SAVATOS et al., tT) from a study of various donors containing carbonyl groups, have shown that on complexing with metals the C = O stretching frequency decreases with increasing strength of the O - - M bond. If we also relate the magnitude of the shifts in C ~ O with the stability of the co-ordinated bond, the observed trend is in good agreement with the melting points of our adducts shown below: Adducts SnC14"2TMU SnCI4"DMU(1,3) SnCI4"2DMU(I,1) SnC14"2MPU

Shift in vC~----O (cm-x)

Melting point (°C)

81 67 30 --

205 198 175 68

Acknowledgement--We are indebted to Dr. M. ONVSZCHUK,McGill University, Montreal, and Head

of the department of Chemistry, Lucknow University, for help received in the form of Chemicals and equipment. One of us (P. P. SINOH)is thankful to the authorities of M.L.K.Degree College, Balrampur, for the grant of study leave from the college. (TJSs. C. CURRANand J. V. QUAGLIANO, J. Amer. Chem. Soc. 77, 6159 (1955). (al R. B. PENLAND, S. MIZUSHIMA, C. CURRAN and J. V. QUAGLIANO, ,Jr. Amer. Chem. Soc. 79, 1575

(1957).