Indian Journal of ChemistryVol. 22A, March 1983, pp 250-252

Monothiocarbamate Derivatives ofSilicon (IV), Germanium(lV),

Tin(IV) & Titanium (IV)

V D GUPTA* & V K GUPTA

Department of Chemistry, Faculty of Science, Banaras HinduUniversity, Varanasi 221 005

Received 16 August 1982; revised and accepted 20 October 1982

A few silicon(IV), germanium(IV), tin(IV) and titanium(lV)N,N-dialkylmonothiocarbamates have been prepared and theirstereochemistries have been discussed mainly on the basis ofIR and PMR data.

Studies on metal monothiocarbamates have evolvednew features from time to timev", This prompted usto examine the ligational behaviour of monothiocarba-mates with some uninvestigated tetravalent elements.

All manipulations were carried out under anhydrousconditions in nitrogen atmosphere. Solvents weredried by standard techniques. Sodium and dialkylam-monium salts of monothiocarbamate were synthesizedby the literature procedure'. SiCl4 (57.8°C), GeCl4(83.0°C), TiCl4 (136°C), n-BuSnCla (93°Cj1O mm Hg)and PhSnCla (90°CjO.07mm Hg) were distilled before

use. The metal, sulphur and chlorine were esti atedgravimetrically and nitrogen by K.ielda~ll'Sme hod.Conductances were measured on a conduc ivity idge(model No. L-370873, Cambridge, En land) ,'sing10-3 M solutions. Molecular weights of soluble 'om-pounds were determined cryoscopicaUy in ben ene.Infrared spectra were recorded on a Perkin- Imer621 instrument in nujol (4000-200 crrr ') a~ insolution (4000-650 cnr-'). PMR spectra were re ord-ed on a Varian A-60 spectrometer using tetram thyl-silane as an internal standard. ~

OrganodichlorotintlvjtMejmtc) (1,2), organ hlo-rotind Vjbist Me.mtc) (3,4), dichloro M(IY)bis(R mtc)(5-10), phenyldichlorotinffvj/Et.mtc) (11), p nyl-chlorotintl vjbisflit.mtc) (12), and organotin(l tris-(Et.mtc) (13,14) complexes[M=Si(IV), T(IV),Ge(IV); Rzmtc=anion of N,N-dialkylmonothio rba-mate, Me.mtc=anion of N,N-dimethylmonoth~ car-bamate, Et2mtc=anionofN,N-diethylmonothio' rba-mate] were prepared as described below: I

The compounds (1-10, Table 1) were synth sizedby adding stoichiometric amount or the " etalchloride or organotin trichloride to a suspenS].1n ofNak.mtc in dichloromethane and the reaction m turewas reftuxed for 3-7 hr. For the isolatibn of om-plexes (11-14) the stoichiometric quantity of org otintrichloride was added dropwise to a benzene so tionof [Et2NHzl+[Et2mtc]- maintained at ,...,5°C a II the

Table I-Analytical Data of Metal N,N-Dialkylmonothiocarbamates

Mol.wt Found (Calc.), %Sl. No. Compound] Appearance m.p. found ----_ .•---------

(0C) (calc.) Metal S N I CIn-BuSnCI2(SOCNMe2) Viscous] liquid 362 32.0 9.9 3.8 ~9.1

(350) (33.S) (9.1) (4.0) 0.2)2 PhSnCI2(SOCNMe.) White 110 31.2 8.9 3.9 ~S.O

(32.0) (S.6) (3.8) 19.1)3 n-BuSnCl(SOCNMe2)2 White 440 28.7 16.2 6.0 8.1

semi-solid (419) (2S.1) (15.3) (6.7) (8.5)4 PhSnCl(SOCNMe2)' White 142 26.1 15.3 6.6 7.S

(27.0) (14.6) (6.4) (S.2)5 GeCI2(SOCNMe,)2 Yellow 170 20.6 18.5 7.6 J9.9

(20.7) (1S.2) (8.0) 20.2)6 GeCI2(SOCNEt2), White 142 176 15.9 6.2 117.2

(17.S) (15.7) (6.8) 17.4)7 TiCl.(SOCNMe.). Orange 150-52(d) 14.8 19.6 8.7 121.6

(14.7) (19.7) (S.6) 121.7)8 TiCI.(SOCNEt2)2 Orange 137-40 12.7 16.9 6.8 18.7

(12.5) (16.8) (7.1)118.6)9 SiClz(OSCNMe2)2 White IS8 9.0 21.1 8.9 24.0

(9.1) (20.S) (9.1)123.1)10 SiCI2(OSCNEt.h White 160(d) 7.5 17.9 7.4 ~9.8

(7.7) (17.6) (7.7)119.5)11 PhSnCI2(SOCNEt.) White 89 402 30.2 7.9 3.4 17.S

(398) (29.7) (S.O) (3.5) 17.7)12 PhSnCI(SOCNEt2). White 100 524 22.1 13.1 6.0 ' 6.7

(495) (23.9) (12.9) (5.7) 1(7.3)13 n-BuSn(SOCNEt.h Brown viscoust 594 20.6 17.3 7.6

liquid (572) (20.7) (16.8) (7.4)14 PhSn(SOCNEt.la White 102 604 19.3 16.0 6.9

(592) (20.0) (16.2) (7.1)+yield 85-90 %; tattempted distillation failed.

250

NOTES

(due to -CH2-protons) and a triplet (due to -CHaprotons) whereas titanium(IV) and monoorganotin(IV)derivatives exhibit overlapping quartets and triplets;in the latter cases the magnetic inequivalence of theethyl protons can be associated with partial doublebond character of C- N which hinders free rota-tion1,2>1o. A comparative study of the nature of PMRspectra of tetravalent metal monothiocarbamatesindicates that the positions of the alkyl protons inPMR spectra can not be taken as diagnostic of themode of bonding of R2mtc moiety. However, for thecomplexes of the same metal atom the values ofchemical shifts can be useful in distinguishing thepresence of the un identate bonding mode.

RSn(Et2mtc)3 complexes appear to involve seven-coordinated tin as these display an intense IR bandin the region 1550-1570 cnr-' due to the chelatingnature of all the three ligands. The spectrum ofSnCl(Et2mtc)3 exhibits (in addition to the intenseabsorption at 1560 crrr+) a strong band at 1605 cm-1which can be explained only by the presence ofunidentate sulphur bonded Et2mtc moiety17-19. Theseobservations are substantiated by PMR spectra ofPhSn(SOCNEt2)3 which shows only one set of over-lapping quartets (due to methylene protons) due tothe three chelating Et.mtc moieties whereas the com-plex CISn(SOCNEt2)3 displays two sets of quartets,separated by 0.658 and 2:1 in intensity due to the twochelating ligands and the third one bonded throughsulphur only (Table 2). The change of the sevencoordinated tin to the six coordinated one in thetris complexes due to replacement of organo group

stirr g was continued for ---4 hr at the room tem-per ure. It was filtered and distilled under reducedpre~ ure. 'llhe products (Table 1) were crystallizedfro chloroform/pet-ether (40-60°C) (1:5) and driedin v uo at 0.1 mm Hg and 30-40°C for nearly6 hr

S· icon(IV), titanium(IV), germanium(IV) andorg otin(IV) monothiocarbamates were synthesizedby I ifferent methods. Attempts to prepare MCI3-

(R2 tc) de1ivatives [M=Si(IV), Ge(IV), Ti(IV)] werefutil as these resulted in the formation of the bispro cts. 1jhis appears to indicate a special stabilityof e octahedral or tetrahedral stereochemistry.Si(I ) and Ge(IV) tetrakis complexes are obtainedas ystalline solids which undergo decompositioneve at ---1O'C in dry nitrogen atmosphere in thesoli state.

11,e metal monothiocarbamates synthesized arecrys lIine and soluble in chloroform, but are lesssolu Ie in benzene. The n-butyltin(IV) (monothio-carb mate) derivatives are viscous liquids or semisoli s, miscible with common organic solvents. Thesebeh we as non-electrolytes in dichloromethane solution(mo r conductances: 0.03-0.70 ohm ? em" mol:").The olecular weight determinations (Table I) of thesolu Ie complexes suggest their monomeric nature inben ne.

T e infrared spectra of SiCl2(R2mtch are remark-ably different from those of the other complexes.The do not show any band in the region> 1500 cm-1sug ¢Sting the unidentate mode of bonding of Rjmtcmoi ,ty through oxygen", which is further evidencedby t e presence of medium intensity bands at 970± 10and 090±15 cm ", assignable to vSi-04 and vC=Sresp ctively, and by absence of band due to vSi-S.The I compounds may be assigned tetrahedralgeo etry unlike the dichloro- and diacetoxy-bis-(~-d etonate )silicon(IV) complexes=" which arekno n to be octahedral. Apparently, this differencemay be due to the very high affinity of silicon foroxy en as compared with that for sulphur. Failure inthe isolation of dithiocarbamate complexes ofsilic n(IV)1 substantiates this finding.

I sharp contrast to the above silicon(IV) complexes,all t e derivatives of germanium(IV), titanium(IV)and, onoorganotin(IV) display intense IR absorp-tion' in the region 1550-1580 cm-1 due to coupledvC 0 and vC=N vibrations revealing the bidentatenat e of Rjrntc moietyt.2,8-10. In bis complexes,MC (SOCNR2)2 (M=Ge, Ti), the presence of twovM- I absorptions in the far IR region in each case[Vas ,e-Clll at 330±5 and vsGe-CI at 325±10 crrr+];[Vas i_CI12at 372±2 and vsTi-Cl at 360±4 cm-l] maybe c neluded to be due to cis-octahedral geometry ofthes complexes in the solid state. The bands at560- .0, 840± 10 and 370-400 crrr+ may arise due tovSn- ,vGe-O and vM-S(M=Ge, Sn) modes respec-tivel 13-16, whereas in titanium(IV) complexes, thecorr sponding vibrations (v'Ti-O and v'Ti-S) may berepr sented by bands in the regions 550-570 and315- 25 cm-l. respectively". acentre of overlapping triplets; bcentre of overlapping quar-

I tets, "centre of triplet, dcentre of quartet, =centre of broadenedP , R spectra (Table 2) of silicon(IV) and germa- quartets.

niu (IV) diethylmonothiocarbamates show a quartet ---: _

Table 2-PMR Data of Metal N,N-Dialkylmonothiocarba-mates in CDCI3

Compound Assignments of PMR signals (Il, ppm)

PhSnCI,(SOCNEt,) C-CH; (1.18, 130);N-CH~ (3.40, 3.50);

Sn-C6H.(9.267.64, 7.65-8.10).

PhSnCI(SOCNEt2), C-CH~(1.12, 1.25);N-Cm(3.38, 3.50);

Sn-C6H.(7.12-7.52,7.70-8.1O)

C-CH~(1.22, 1.26);N-Cm(3.45, 3.58);

Sn-C6H.(7.31-7.70, 7.86-8.26).

C-CH~(1.15);N-CH~(3.40, 2.75).

PhSn(SOCNEt, h

CISn(SOCNEt')3

C-CHg(l.50); N-CH~(3.10).

C-CHi(1.28); N-Cm(3.38, 3.50).

N-CH3(3.36, 3.39).N-CH.(2.76).

C-CH~(1.38);N-CH~(2.95).

TiCI2(SOCNEt2),

TiCI.(SOCNMe,).SiCI,(OSCNMe,),

SiCla(OSCNEt2),

251

INDIAN J. CHEM., VOL. 22A, MARCH 1983

by chIoro moiety on the central tin atom can not beaccounted in terms of electronic effects which wouldmake tin atom otherwise more coordinatively unsatu-rated in the chloro-tin complexes. The increasedaffinity of organotin(IV) moiety for soft bases offerssome explanation of this difference in behaviour.

The authors are grateful to the CSIR, New Delhifor a Junior Research Fellowship (to VKG), and toMis Nitto Kasei for the gift of organotin(IV) chloridesamples.

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