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Mössbauer study of some disubstituted distannoxanes (R′COO)R2SnOSnR2(OOCR′) and (R′COO)R2SnOSnR2(OH)
177
Journal of Organomctallic Chemistry. 128 (1977) 177-186 0 Elsevier Sequoia S.A.. Lausanne - Printed in The Netherlands
MijSSBAUER STUDY OF SOME DISUBSTITUTED DISTANNOXANES (R’COO)R,SnOSnR2(OOCR’) AND (R’COO)R1SnOSnR2(0H)
SANDRO
CALOGERO
Laboratorio PIER0
di chimica e tecnologia
FURLAN.
VALERIO
Istituto di Chimica Analitica. (Received
dei Radioelementi
PERU220
de1 C.N. R.. Padova (Italy)
and GIUSEPPE
Universitd di Padova.
T_4GLIAVINI
Via Marzolo
1. I35100
l
Padova (Italy)
August Sth, 1976)
Summary Mossbauer parameters have been determined for a series of disubstituted distannoxanes of type A, (R’COO)R2SnOSnR,(OOCR’), and of type B, (R’COO)R2SnOSnR2(OH), (R = n-C4H9, CH,=CH, CHz=CHCH2 and R’ = CHx, CH&l, CHCIZ, CCls, CFs). A treatment of the data by the point-charge method has been carried out. Taken together with the published literature X-ray, IR, NMR and molecular weight data, the results are consistent with dimeric structures in which the tin atoms are in a trigonal-bipyramidal geometry. The quadrupole splitting, with fixed R’, increases on passing from the allyland butyl- to vinyl-haloacetate derivatives_ It is inferred that this trend might be correlated with the structural packing of the skeleton of the very similar ladder-type dimeric structures formed by inter- and intra-molecular Sri--- bonds.
Introduction Many investigations on disubstituted distannoxanes of type A, (XR2SnOSnRZX), and of type B, (XR2SnOSnR20H) by means of X-ray analysis [l-3], IR, MSssbauer and NMR spectra and molecular weight determinations [1,4-lo], have revealed the tendency of these compounds to exist as dimers both as solids and in organic solvents. In such dimers the various functional ligands X, which have different bonding modes, are able to influence the packing of the dimeric skeleton formed by the Sn-0 and Sn-X bonds. This can be seen by comparing the structures of the following compounds: { fMe,SnOSiMe, J*O} 2 [I], { [Me,SnNCS]20)2 [Z] and { [n-Bu:SnOOCCCl~] ,O), 131, schematically represented by structures I, II and-III together with time signifi-t bond length data (A). .It has hee~_sugge$ed -that the ming lengths Of the inter- and intra-molec~ar SIFO .j+$~fun&o~-ligand bonds affect the Mijssbauer quadrupole splittmg
178
(I)
(III
KE,
values [ 41. Thus we have undertaken a Mijssbauer study on disubstituted haloacetate distannoxanes of both types A and B [5-T], (Type A: R = n-GH9, R’ = CHa, CH&I, CHC&, Ccl,; R = CH,=CH, R’ = CH&I, CHC12, CCla, CF,; R = CHz=CHCH2, R’ = CH,Cl, CHC&, CC13_Type Br R = n-CLH,, R’ = CH3. CH,Cl, CC13, CF3; R = CH,=CH, R’ = CHC$, Ccl,). In addition to examining how the different functional ligands influence the dimer skeleton packing, it has been our aim to determine how the organic groups R are acting. The vinyl group is considered to interact with tin by pm-d, bonding [ll] and to make the Sn-0 bonds stronger and more covalent 1121 in the trivinyltin carboxylates than in the trimethyltin carboxylates [13]. On the other hand, the ally1 group, through an hyperconjugation-like interaction between the Sri--- bond and the allylic double bond, decreases the electron density at the tin atom [14,15 ]_ Thus it is thought that these organic ligands with fiied R’, can differ in their effects on the electron density and the electric field gradient [16] at the tin nucleus, leading to differences in the Mijssbauer parameters. Experimental The distannoxanes used have been prepared as previously reported [5-71 by treating tetraallyl-, dibutyldiallyl- and divinyldiallyltin substrates with the appropriate carboxylic acids in methanol or aqueous acetone media. The compounds were crystallized twice from chloroform/n-hexane mixture, giving melting points and IR spectra as previously reported_ IR spectra were recorded on a Perkin-Elmer Model 457 spectrophotometer equipped with KBr optics, using dispersed Nujol mulls or carbon tetrachloride solutions_ Molecular weights were determined in CC4 with a Mechrolab Model 302B Vapour:Phase Osmometer. “%?ln Miissbauer spectra were recorded at 80 K by a conventional constantacceleration spectrometer using a Ca’*-9”Sn0a source at room temperature. The
velocity scale was calibrated and its linearity checked by use of an enriched.
standard iron foil. An RSG-60 Reuter-Stokes proportional counter was used. Centre shift values are relative to SnOl at room tenipeiature. i 1 ,.- ..-I--_:_. Powdered samples; mixed.with.an inert matrix‘ of perspex; weie encapsulated between mylar vvindo+ held _by high purity alunririium containers. :The &&ber ti&nes m app~ox+*$ 50ehg[cm2,:.1. ‘__‘ ;,-ycIi:;_;. :~ I :=,I_.:-,:I.i_--~.~:~~.r.,-l,:ii_c--_Ii. ; :yr_ A Hofman liquid helium c~@stat~~equipp&vith:& self~feed$~g.Iiq~~@troge~~-~ -_~__p_-.. ;: _:-. -:;.p; :.-
179
supply was used. The temperature was checked by a con&i&an-iron thermocouple. 900 channels of the 4096 channel analyzer were used. The contents were collected by a teleprinter (HP 3752A) and by an X-Y recorder (HP 7004B)_ All spectra, corrected for-solid angle effects, were fitted, without constraints to two Lorenzian line shapes by a program 1173 adapted by us for use with a CDC Cyber 76 computer.
In no case was a detectable MSssbauer effect observed at room temperature. Most of the spectra were found to be asymmetric, the average area ratio being, for random polycrystalline samples, less than 1.3. Representative spectra of three of the compounds examined are given in Fig. 1.
as4
_-l__,_
--
Compound
.-_.^--__----
,..______.___._____
.._...,...
db PC
I‘d
_.._.
_._
.
.._._
I,47 1.46 1,87 1,36 1.42 1.42 1.36 1,32f 1,41 I*40 1,19 I,26 1,25 1,34 1,33 1,29 1,lS .
.
*
.
.._.--..-.-
.-..
_-
,8,92 8,91 3,72 8,71 3.01 3,GO 8,4S 3,2G f 3.62 3.42 3.30 3.18 3.06 2,9S 2,96 2,79 2.64 ,..,
-.
1.20 1,2S 1,2G I,18 1.02 1,oo 1,lG 1.08 1.10 1.08 1,16 1.25 1.23 1.29 1.06 0.98 1.20
1050s lG2Gs(br) 1GOGs 1KGOs 1GGOs lG3bs 1688s 1GGOvs lG66ve lGSOs(br) 1668s 1646s lGOk(br)
1GGOs 1646~11 lG26s
Y&OO)e
-______-_---
I_.,- I. . .. . -_.-_..-_-_. _..._ -.-..-._._____
2.67 2,GS 2.72 2.76 2.64 2.G3 2.62 2.44 2.GO 2.49 2.77 2.60 2.44 2.22 2.23 2.10 2.24
....__
tjo,b’
33GOs(br) 3340s(br) 3420m(br) 3600m(br) 83GOm(br) 32GOm(br)
VWf) @ (cm-‘)
j,; IS
c p mA/& d Computed FWHM. c posltior~ of the osymmctric strotchlng vibration band of the In&a. molooulu bddoinr carboxylata urouu and the OH stretohlng vlbratlon band in Nujol mull, KBr optics (see also ref, B-7), 1 See ref. 4 and 9 for previousvalues: 1.82, !,80 mm/w and 3.22,3,24 mmlac, for d and A rcspectlvcly.
f!irdatlve to Sn02 at room temperature. b $0.08 mm/set,
10 11 12 ‘1 18 I4 16 16. l? !,
‘Number
M&SBAUER (SO K) AND IR DATA FOR [R@nXl20 AND XR2SnOSnRzOH COMPOUNDS _____________-,..” ._.._ “.r_-“_.-_ ._._. __..._ __._*__.-_...r_._...-._._._.I_^-.__ _.___
TABLE 1
181 Table 1 lists the Mikbauer
centre shift (6) and the quadrupole
splitting (A)
parameters together with the Herber p-values [lS], the I?,, computed full width at half maximum (FWHM), the v,(COO) and v(OH) stretching frequencies of the distannoxanes examined. These have been divided into five groups (cf. Table 1) with the aim of listing and distinguishing them by compound type and by the organic groups (R). For each group the S, A and v,(COO) values increase in the order, CH, < CHzCl < CHCl, < Ccl, < CF,. Looking at the compounds having fiied R and R’ groups, it is notable that the 6 and A values are greater for a compound of type A than of type B; in addition, for compounds with the same R’, the quadrupole splitting trend is in the order, vinyl > butyl > allyl. The p-values are in the range 2.16-2.77. Using the additive point-charge method [ 16,191, we have obtained a good fit by taking into account models in which the tin atoms are arranged in a regular trigonal bipyramidal geometry_ We used the models represented below, which represent the distannoxanes of types A and B, respectively: 2
z
t XtDc!
t OH
tbo
*toe
Rtbe I r-M,
\
the
-X
\I
;
the
.-hl*
-
x
,‘+ I Xtba
I toa X
CR = x
=
n-C&
,
R’COO.
. Ct-$=CH--CH2.
Ci-$=CH M,
=
COSnR2)2SnR2X,)
(i? =
“-C,H9
.
CH2=CH
X =
R’COO
,
M2
=
.
(OSIIR~)~S~R~XOH)
The components of the electric field gradient (EFG) tensor are given by equations l-3 for compounds of type A and 4-6 for compounds of type I3with
IV&
> IV&
> IVzJ:
V,, = [2 {Mib”) -1 {RCk} - 2(Xtba)].
(1)
VYY= [-fM:“‘}+
(2)
V,,
= [-{M:bc)
vxx = cZ{Mib’} v,,
g (Rcbe) - 2{Xtb’)]e -2(Rtbe}
+ 4{Xtba)]
e
(3)
- k{Rtb”) -
(OHtan) -
{Xtb”)] e
(4)
= [-((M:b= ) + z{Rtbe 3 -
(OHtba 3 -
{Xtba33 e
(5)
V,, = [-{MibeI- 2 {Rtbs ) + 2 {Ol!Pb” ) + 2 {Xtb* )] e
(6)
We used the trigor&bipyramidal apical (tba) and equatorial (tbe) partial quadrupole splittingvalues as reported by Bancroft et al. 1201.as follows. Apical parameters:
_CH&OO
.= 0.075,
CH&lCOO
= 0.13,
CHCl,COO
= 0.175,
CCl&OO
CF$OO 7 0.21, OH = -0.13 mm/set;equatorial parameters: for the but@group the value -1.13 mm/setis assumed,as reported for other alkyl =_OJg;
sups;-:.--..
182 TABLE2 OBSERVBDANDCALCULATEDQUADRUPOLESPLITTINGS
compounds = 1 2 3 4 5 6 7 8 9 10 I1 12 13 14 15 16 17
A obs 3.92 3.91
b
3.72 3.71 3.61= 3.60 3.48 3.26 3.szd 3.42 3.30 3.13e 805 298 296 2.79 264
._
Acalcd
71
4.17 4.03 -3.86 -
0.52 0.54 0.56 -
-3.67 -3.50 -3.28 -3.55 -3.38 -3.41 -3.10 -3.06 -2.95 -2.85
0.46 0.48 0.51 0.43 O-45 0.80 0.71 o-72 0.75 0.78
=ReferencesnumberofTable1.5Usedtoderive ~~~~Iltbe)-0_59mm/~c.=Usedtodedve {CH2=CHcbe) - 1.28 mmf~ec.~Used toderive {CH2=CHCH2tbej-1.08 mm/see_ eusedtodetive {~;?~~~)-0.45 mnllsec.
From equation 3, taking into account the observed quadrupoie splittings of the compounds 5,2, and 9 of Table 2, {Mtb’} = -0.59 mm/see, {CH,=CHtbe) = -1.28 mm/set, {CH2=CHCHibe} = -1.08 mm/set were calculated. Analogously from equation 6 and the observed quadrupole splitting of the compound 12, iMibe) = -0-45 mmlsec is caIcuIated_ Table 2 shows the quadrupole splittings and the asymmetry parameters Q calculated by means of these values in equation l-6 for thirteen of the compounds examined_ The fitting of the tA_& against the IAobsI gives a straight line of slope 1.01, intercept 0.13 mm/set and 1 correlation coefficient 0.9’7, showing a good agreement with the ideal values. The difference I !A\,1 - IA,,I 1<<0.4 mmlsec 1201, for alI the compounds examined, allows us to assign the tin atoms to a trigonal bipyramidal geometry.
On the basis of the previous IR (cf. Table 1) and molecular weight data [1,5-‘7,211 and the X-ray structure of {[n-Bu2SnOOCCC13]20)? [3], all the distannoxanes examined may be regarded as isostructuraI dimeric compounds. Distannoxanes of type B may he thought to have the structure IV. This is in agreement with data from the present work listed in Table 3- These
refer to tetrabutyl-1-trich.Ioroa&etoxy-3-hydroxy-oxanb, which,-in solution, behavesin a similarway to the correspon_pinghaloacetate of type A [3]. It
is a dimer in Cm, and in the solid state or in solution it gives v&00) stretching frequency values typical of a bridging carhoxyIate group- An additional interact MY
183
A\
3h1,
H--O----/
L
,Sn
0
* h-d
I I \ 5s” ,O\sn__c--oNH
u!z) tion seems to ezcistbetween the tin atoms and the OH ligand, since the OH stretching frequency shifts from 3500 cm-’ in the solid to 3650 cm-’ in solution, whereas the v,(COO) frequencies are practically unchanged. The interactions of the haloacetate ligand in structure III or those of the hy- _ droxy !igand in IV with the endocyclic tin atoms seem not to contribute to the hexacoordinated environment of these tin atoms 131.This point of view is supported by the present data-. all MSssbauer spectra show the presence of simple doublets, providing no evidence for distinguishable tin atoms. Whether from Herber’s criterion [lS] or from point charge calculations, the tin atoms must be considered to lie in a pentacoordinated geometry. The centre shift trend (cf. Table 1) increases with the increase of the electronegativity of the functional ligands [22]. In the present class of compounds, as with the class of triorganotin haloacetates previously examined [23-251. Introduction of haloacetate groups having increasing electron-acceptor properties tends to remove electron density from the tin atom through the carboxylate group. Thus halo-substitution increases the positive charge on the tin atom and the result is a deshielding of the 5sorbital which leads to an increase of the effective nuclear charge. The deshielding effect is more pronounced for compounds
TABLE
3
IR DATA FOR SOLID STATE
TETB.ABUTYL-l-TRICHLOROACRTOXY-3-IiYDROXYDISTANNOXANE
AND
IN SOLUTION
AND
MOLECULAR
Medium
Concentration wml).
Nuid
-
16504
Ccl4
6.4.~ b
1665% 1680s
=i = Mk&.
found/moLwt.
akd.
u,
(662.02).
WEIGHT
IN
MOW
5 ~oncentntion
THB
IN CC& (37°C) MoL ut found
i=
1342
2.03
3506mrnr)
3650m neax to a stunted
so~olution.
184
Fig_ of
2. PIot
type
A:
of quadmpole .s vinyl-.
splitting
against
0 butykiistannoxanes
Taft of
inductive
type
factor.
o vinyl-.
‘2 butyl-.
0 eUyl-distannoxane~
B.
of type A than for type B, since in the former four haloacetate groups are pre- . sent. On considering the quadrupole splitting values, we have found a linear correlation between the A values and the Taft factor u* of the R’ groups (cf. Fig. 2), consistent with the behaviour previously demonstrated for a series of triorganotin haloacetates R$SnOOCR (R = Me and Ph) [23-251. In Table 4 are listed the values of the slop.es p and the intercepts A0 (calculated quadrupole splitting value of the acetate) involved in the equation A = A0 + po’ for the five groups of compounds examined and for those previousiy reported. It will be seen that no significant differences, within the standard deviations, appear in the p-values
TABLE
4
LINEAR OF THE stxies
CORRELATION R’ GROUPS_
of kostruchxral
+po*J
BETWEEN
THE
A-VALUES
d Reported
value for the acetate, bObservcbvnlue values
THE
o*
TAFT
FACTOR
compounds
0.131
+ 0.04
853 * 0.09
0.135
* 0.03
3.29 t 0.05
3.26 + 0.03
0.137
= o.aos
3_16
-
in nt
24:
see eIso
nt
25,
0.119
*- 0.01
0_213
*
0.182
=
0.231
5 0_04Sd
lo;
6 o_oaiod 0.01
the acetate.
f
-
(100
283 265 ir 0.05 3ss f 0_02= 3.69 d 3.34d
0.113
* Cdctited
AND
C Our
erlcuhtion
2.64 867 3.68 3.36 from
data
_C0.03 * 0.04 % 0.03 k 0.03
of ref.
2%
185
inside each series of compounds; the values for the isostructural chain polymeric triorganotin derivatives 1241 are greater than those of the dimeric distannoxanes. The linear correlation found is significant in establishing that only electronic effects are important in determining the trend of the A values 1241. For trimethyltin derivatives it has been proposed [24] that the A trend arises from an increasing asymmetry of the two Sn-0 bonds with the increase of the o* of the haloacetate groups. This is consistent with structural data on the trimethyltin acetate and trifluoroacetate 124-261. Starting from this point of view, we suggest that within an isostructural series of compounds, the slope p assumes a vaIue which is in account for different structural parameters. It seems to us that the regular increase in the splitting quadrupole values for all the five groups of compounds examined can be related to the variation of parameters which characterise the isostructural skeleton of the very similar ladder-type dimeric structure formed by the Sri-0 bonds. In these compounds the influence of groups of increasing electron-acceptor ability might reinforce the carboxylate C-O bonds (cf. trend of the v,(COO) values, Table 1) and reduce the Sn---OOCR’ bonding. As a consequence the intra- and inter-molecular Sri-0 bonds become stronger. The effect of the structure packing is also revealed by comparing the A0 values of the distannoxanes of type B, which are lower than those of the distannoxanes of type A, this lowering probably being due to the presence of only two carboxylate groups in the former. Support for the above arguments comes also from analysing the trend of the A, values which concern acetate derivatives having different R groups around the tin atoms. In order to discuss this trend, the intercept values A0 (cf. Table 4) must be taken into consideration. On the basis of these values we obtain the following A0 trend order, vinyl (3.53) > butyl(3.29) > ally1 (3.15) for type A and vinyl (2.83) > butyl(2.65) for type B. The differences between these values do appear to be significant. It is notable that introduction of the different alkyl groups in an homologous series of distannoxanes does not cause any variation in the A values. Tetrabutyl-, tetraoctyl- and tetramethyl-1,3-(trimethylsiloxy)distannoxanes values: 2.46,2.45 and 2.42 respectively effects which could be produced organic groups employed. In our opinion, the Sn-0 bonds
stronger and more covalent [ 12,131, whereas the ally1 group has the opposite effect_ In other words, by comparison with the butyl group, these groups seem to promote a different packing in the dimeric molecule. Acknowledgment We are pleased to &knowledge support of this work to CNR, Roma, Grant
No. 75.01048.03. References 1 RO~-~M,Wa~Advur.OrpnometrlCbc~.5<1967)164.~d~f.thueia 2 y.~~chow.Ino~Chem.10(1971~673.
186 3
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
R. Gnuiani. G. Bombieri. E FoxseXni. P_ Furlas V. Pe-o and G_ Ta&iavini. .I_ OrganometaL Cbem_. 125 <19-i’?) 43. A&. Davies. L. Smith. P.J. Smith and W. McFarIane. J. OrganometaL Chea, 29 (1971) 245. and ref. the&n. v_ PUUUO. G. Pknogna and G. TagIiavinI. J. OrganometaL Chem_. 40 (1972) 121. V_ Perozzo and Cl Ta&IavIni. J. Organomet8L Chem, 66 (1974) 437. V. Peruzzo. G. PIazzogna and G. TazIIavinL Gazz. Chbn It& 104 (1974) 767. LM_ K&ham&% O.Yu. OkhIobytin. A.V. POPOV and B-1. Rogosev. Dokl. Akad. Nauk. SSSR. 160 (1965) 112X V.I. Gol’danskii. EF_ ‘Makarov. R-k Stukas V-k Trukhtanov. and V-V_ Kirapov. DOW_ Phys_ Chem.. 151<1963) 598. V.I. Gol’danskii, V.V. Kbmpov. O.Yu. OkhIobysti and V.Ya Rochev. in V.I. Gol’danskii and R-H_ Herber (Eds). ChemIcaI Applications of Miissbauer Spectroscopy; Academic Press, N-Y.. 1968. Ch. 6. V. Pe-o. G. PIazzogna and G. TagIIavIoI. J. OrganometaL Chem_. 24 (1970) 347. RE Hester and D. bIascord. J_ O~ometaL Cbem.. 51<1973) 181. R.E Hester. in HA_ Szymanski cm). Raman Spectroscope. Plenum Press New York. 1967. K Kawakami and H.G. KuIviIa, J. 0s Chem.. 34 <1969) 1502. A SchweIg. U_ Weidner and G. Manuel. J. OrganometaL Chem. 54 (1973) 145. RV. Pa&band R.H. PI&t. J. Chem. Sot. A. (1969) 2145. B-L. Ck . T.A. TumoIilIo. Compu+ Phys. Commun.. 3 (1971) 322. RK Herber. H.k StiickIer and W.T. ReiehIe. J. Chem. Phys. 42 (1965) 2447. B.W. Fitzsimmons. N.J. 6eeIey and A-W_ Smith. J. Chem_ 6oc.. A. (1969) 143. G-M_ Bancroft. V.G. Kumar Das, T. K. Sham and M.G. CIark. J. Cbem. Sot.. Dalton, (1976) 643. R Okawam and M. Wada. J_ OqamxnetaJ_ Cbem, 1<1963) 81 R.V. Parish and R.H. PIatt. Inorg. ChIm. Acta. 4 <1970) 589. N-W-G_ Debye. D-E Fenton. S.E Ulrich and J.J. Zuckermao. J. Or@uometaL Chem_. 28 <1971) 339. B_F_E Ford and J-R Sams. J. ~ometat Chem_. 31 <1971) 47. C. Poderand J-R 3ams. J. OrgaoometaL Chem.. 19 (1969) 67. II_ Chib and B.R. Penfold J. Cryst. MoL Struct. 3 (1973) 285.
Journal of Organomctallic Chemistry. 128 (1977) 177-186 0 Elsevier Sequoia S.A.. Lausanne - Printed in The Netherlands
MijSSBAUER STUDY OF SOME DISUBSTITUTED DISTANNOXANES (R’COO)R,SnOSnR2(OOCR’) AND (R’COO)R1SnOSnR2(0H)
SANDRO
CALOGERO
Laboratorio PIER0
di chimica e tecnologia
FURLAN.
VALERIO
Istituto di Chimica Analitica. (Received
dei Radioelementi
PERU220
de1 C.N. R.. Padova (Italy)
and GIUSEPPE
Universitd di Padova.
T_4GLIAVINI
Via Marzolo
1. I35100
l
Padova (Italy)
August Sth, 1976)
Summary Mossbauer parameters have been determined for a series of disubstituted distannoxanes of type A, (R’COO)R2SnOSnR,(OOCR’), and of type B, (R’COO)R2SnOSnR2(OH), (R = n-C4H9, CH,=CH, CHz=CHCH2 and R’ = CHx, CH&l, CHCIZ, CCls, CFs). A treatment of the data by the point-charge method has been carried out. Taken together with the published literature X-ray, IR, NMR and molecular weight data, the results are consistent with dimeric structures in which the tin atoms are in a trigonal-bipyramidal geometry. The quadrupole splitting, with fixed R’, increases on passing from the allyland butyl- to vinyl-haloacetate derivatives_ It is inferred that this trend might be correlated with the structural packing of the skeleton of the very similar ladder-type dimeric structures formed by inter- and intra-molecular Sri--- bonds.
Introduction Many investigations on disubstituted distannoxanes of type A, (XR2SnOSnRZX), and of type B, (XR2SnOSnR20H) by means of X-ray analysis [l-3], IR, MSssbauer and NMR spectra and molecular weight determinations [1,4-lo], have revealed the tendency of these compounds to exist as dimers both as solids and in organic solvents. In such dimers the various functional ligands X, which have different bonding modes, are able to influence the packing of the dimeric skeleton formed by the Sn-0 and Sn-X bonds. This can be seen by comparing the structures of the following compounds: { fMe,SnOSiMe, J*O} 2 [I], { [Me,SnNCS]20)2 [Z] and { [n-Bu:SnOOCCCl~] ,O), 131, schematically represented by structures I, II and-III together with time signifi-t bond length data (A). .It has hee~_sugge$ed -that the ming lengths Of the inter- and intra-molec~ar SIFO .j+$~fun&o~-ligand bonds affect the Mijssbauer quadrupole splittmg
178
(I)
(III
KE,
values [ 41. Thus we have undertaken a Mijssbauer study on disubstituted haloacetate distannoxanes of both types A and B [5-T], (Type A: R = n-GH9, R’ = CHa, CH&I, CHC&, Ccl,; R = CH,=CH, R’ = CH&I, CHC12, CCla, CF,; R = CHz=CHCH2, R’ = CH,Cl, CHC&, CC13_Type Br R = n-CLH,, R’ = CH3. CH,Cl, CC13, CF3; R = CH,=CH, R’ = CHC$, Ccl,). In addition to examining how the different functional ligands influence the dimer skeleton packing, it has been our aim to determine how the organic groups R are acting. The vinyl group is considered to interact with tin by pm-d, bonding [ll] and to make the Sn-0 bonds stronger and more covalent 1121 in the trivinyltin carboxylates than in the trimethyltin carboxylates [13]. On the other hand, the ally1 group, through an hyperconjugation-like interaction between the Sri--- bond and the allylic double bond, decreases the electron density at the tin atom [14,15 ]_ Thus it is thought that these organic ligands with fiied R’, can differ in their effects on the electron density and the electric field gradient [16] at the tin nucleus, leading to differences in the Mijssbauer parameters. Experimental The distannoxanes used have been prepared as previously reported [5-71 by treating tetraallyl-, dibutyldiallyl- and divinyldiallyltin substrates with the appropriate carboxylic acids in methanol or aqueous acetone media. The compounds were crystallized twice from chloroform/n-hexane mixture, giving melting points and IR spectra as previously reported_ IR spectra were recorded on a Perkin-Elmer Model 457 spectrophotometer equipped with KBr optics, using dispersed Nujol mulls or carbon tetrachloride solutions_ Molecular weights were determined in CC4 with a Mechrolab Model 302B Vapour:Phase Osmometer. “%?ln Miissbauer spectra were recorded at 80 K by a conventional constantacceleration spectrometer using a Ca’*-9”Sn0a source at room temperature. The
velocity scale was calibrated and its linearity checked by use of an enriched.
standard iron foil. An RSG-60 Reuter-Stokes proportional counter was used. Centre shift values are relative to SnOl at room tenipeiature. i 1 ,.- ..-I--_:_. Powdered samples; mixed.with.an inert matrix‘ of perspex; weie encapsulated between mylar vvindo+ held _by high purity alunririium containers. :The &&ber ti&nes m app~ox+*$ 50ehg[cm2,:.1. ‘__‘ ;,-ycIi:;_;. :~ I :=,I_.:-,:I.i_--~.~:~~.r.,-l,:ii_c--_Ii. ; :yr_ A Hofman liquid helium c~@stat~~equipp&vith:& self~feed$~g.Iiq~~@troge~~-~ -_~__p_-.. ;: _:-. -:;.p; :.-
179
supply was used. The temperature was checked by a con&i&an-iron thermocouple. 900 channels of the 4096 channel analyzer were used. The contents were collected by a teleprinter (HP 3752A) and by an X-Y recorder (HP 7004B)_ All spectra, corrected for-solid angle effects, were fitted, without constraints to two Lorenzian line shapes by a program 1173 adapted by us for use with a CDC Cyber 76 computer.
In no case was a detectable MSssbauer effect observed at room temperature. Most of the spectra were found to be asymmetric, the average area ratio being, for random polycrystalline samples, less than 1.3. Representative spectra of three of the compounds examined are given in Fig. 1.
as4
_-l__,_
--
Compound
.-_.^--__----
,..______.___._____
.._...,...
db PC
I‘d
_.._.
_._
.
.._._
I,47 1.46 1,87 1,36 1.42 1.42 1.36 1,32f 1,41 I*40 1,19 I,26 1,25 1,34 1,33 1,29 1,lS .
.
*
.
.._.--..-.-
.-..
_-
,8,92 8,91 3,72 8,71 3.01 3,GO 8,4S 3,2G f 3.62 3.42 3.30 3.18 3.06 2,9S 2,96 2,79 2.64 ,..,
-.
1.20 1,2S 1,2G I,18 1.02 1,oo 1,lG 1.08 1.10 1.08 1,16 1.25 1.23 1.29 1.06 0.98 1.20
1050s lG2Gs(br) 1GOGs 1KGOs 1GGOs lG3bs 1688s 1GGOvs lG66ve lGSOs(br) 1668s 1646s lGOk(br)
1GGOs 1646~11 lG26s
Y&OO)e
-______-_---
I_.,- I. . .. . -_.-_..-_-_. _..._ -.-..-._._____
2.67 2,GS 2.72 2.76 2.64 2.G3 2.62 2.44 2.GO 2.49 2.77 2.60 2.44 2.22 2.23 2.10 2.24
....__
tjo,b’
33GOs(br) 3340s(br) 3420m(br) 3600m(br) 83GOm(br) 32GOm(br)
VWf) @ (cm-‘)
j,; IS
c p mA/& d Computed FWHM. c posltior~ of the osymmctric strotchlng vibration band of the In&a. molooulu bddoinr carboxylata urouu and the OH stretohlng vlbratlon band in Nujol mull, KBr optics (see also ref, B-7), 1 See ref. 4 and 9 for previousvalues: 1.82, !,80 mm/w and 3.22,3,24 mmlac, for d and A rcspectlvcly.
f!irdatlve to Sn02 at room temperature. b $0.08 mm/set,
10 11 12 ‘1 18 I4 16 16. l? !,
‘Number
M&SBAUER (SO K) AND IR DATA FOR [R@nXl20 AND XR2SnOSnRzOH COMPOUNDS _____________-,..” ._.._ “.r_-“_.-_ ._._. __..._ __._*__.-_...r_._...-._._._.I_^-.__ _.___
TABLE 1
181 Table 1 lists the Mikbauer
centre shift (6) and the quadrupole
splitting (A)
parameters together with the Herber p-values [lS], the I?,, computed full width at half maximum (FWHM), the v,(COO) and v(OH) stretching frequencies of the distannoxanes examined. These have been divided into five groups (cf. Table 1) with the aim of listing and distinguishing them by compound type and by the organic groups (R). For each group the S, A and v,(COO) values increase in the order, CH, < CHzCl < CHCl, < Ccl, < CF,. Looking at the compounds having fiied R and R’ groups, it is notable that the 6 and A values are greater for a compound of type A than of type B; in addition, for compounds with the same R’, the quadrupole splitting trend is in the order, vinyl > butyl > allyl. The p-values are in the range 2.16-2.77. Using the additive point-charge method [ 16,191, we have obtained a good fit by taking into account models in which the tin atoms are arranged in a regular trigonal bipyramidal geometry_ We used the models represented below, which represent the distannoxanes of types A and B, respectively: 2
z
t XtDc!
t OH
tbo
*toe
Rtbe I r-M,
\
the
-X
\I
;
the
.-hl*
-
x
,‘+ I Xtba
I toa X
CR = x
=
n-C&
,
R’COO.
. Ct-$=CH--CH2.
Ci-$=CH M,
=
COSnR2)2SnR2X,)
(i? =
“-C,H9
.
CH2=CH
X =
R’COO
,
M2
=
.
(OSIIR~)~S~R~XOH)
The components of the electric field gradient (EFG) tensor are given by equations l-3 for compounds of type A and 4-6 for compounds of type I3with
IV&
> IV&
> IVzJ:
V,, = [2 {Mib”) -1 {RCk} - 2(Xtba)].
(1)
VYY= [-fM:“‘}+
(2)
V,,
= [-{M:bc)
vxx = cZ{Mib’} v,,
g (Rcbe) - 2{Xtb’)]e -2(Rtbe}
+ 4{Xtba)]
e
(3)
- k{Rtb”) -
(OHtan) -
{Xtb”)] e
(4)
= [-((M:b= ) + z{Rtbe 3 -
(OHtba 3 -
{Xtba33 e
(5)
V,, = [-{MibeI- 2 {Rtbs ) + 2 {Ol!Pb” ) + 2 {Xtb* )] e
(6)
We used the trigor&bipyramidal apical (tba) and equatorial (tbe) partial quadrupole splittingvalues as reported by Bancroft et al. 1201.as follows. Apical parameters:
_CH&OO
.= 0.075,
CH&lCOO
= 0.13,
CHCl,COO
= 0.175,
CCl&OO
CF$OO 7 0.21, OH = -0.13 mm/set;equatorial parameters: for the but@group the value -1.13 mm/setis assumed,as reported for other alkyl =_OJg;
sups;-:.--..
182 TABLE2 OBSERVBDANDCALCULATEDQUADRUPOLESPLITTINGS
compounds = 1 2 3 4 5 6 7 8 9 10 I1 12 13 14 15 16 17
A obs
b
3.72 3.71 3.61= 3.60 3.48 3.26 3.szd 3.42 3.30 3.13e 805 298 296 2.79 264
._
Acalcd
71
4.17 4.03 -3.86 -
0.52 0.54 0.56 -
-3.67 -3.50 -3.28 -3.55 -3.38 -3.41 -3.10 -3.06 -2.95 -2.85
0.46 0.48 0.51 0.43 O-45 0.80 0.71 o-72 0.75 0.78
=ReferencesnumberofTable1.5Usedtoderive ~~~~Iltbe)-0_59mm/~c.=Usedtodedve {CH2=CHcbe) - 1.28 mmf~ec.~Used toderive {CH2=CHCH2tbej-1.08 mm/see_ eusedtodetive {~;?~~~)-0.45 mnllsec.
From equation 3, taking into account the observed quadrupoie splittings of the compounds 5,2, and 9 of Table 2, {Mtb’} = -0.59 mm/see, {CH,=CHtbe) = -1.28 mm/set, {CH2=CHCHibe} = -1.08 mm/set were calculated. Analogously from equation 6 and the observed quadrupole splitting of the compound 12, iMibe) = -0-45 mmlsec is caIcuIated_ Table 2 shows the quadrupole splittings and the asymmetry parameters Q calculated by means of these values in equation l-6 for thirteen of the compounds examined_ The fitting of the tA_& against the IAobsI gives a straight line of slope 1.01, intercept 0.13 mm/set and 1 correlation coefficient 0.9’7, showing a good agreement with the ideal values. The difference I !A\,1 - IA,,I 1<<0.4 mmlsec 1201, for alI the compounds examined, allows us to assign the tin atoms to a trigonal bipyramidal geometry.
On the basis of the previous IR (cf. Table 1) and molecular weight data [1,5-‘7,211 and the X-ray structure of {[n-Bu2SnOOCCC13]20)? [3], all the distannoxanes examined may be regarded as isostructuraI dimeric compounds. Distannoxanes of type B may he thought to have the structure IV. This is in agreement with data from the present work listed in Table 3- These
refer to tetrabutyl-1-trich.Ioroa&etoxy-3-hydroxy-oxanb, which,-in solution, behavesin a similarway to the correspon_pinghaloacetate of type A [3]. It
is a dimer in Cm, and in the solid state or in solution it gives v&00) stretching frequency values typical of a bridging carhoxyIate group- An additional interact MY
183
A\
3h1,
H--O----/
L
,Sn
0
* h-d
I I \ 5s” ,O\sn__c--oNH
u!z) tion seems to ezcistbetween the tin atoms and the OH ligand, since the OH stretching frequency shifts from 3500 cm-’ in the solid to 3650 cm-’ in solution, whereas the v,(COO) frequencies are practically unchanged. The interactions of the haloacetate ligand in structure III or those of the hy- _ droxy !igand in IV with the endocyclic tin atoms seem not to contribute to the hexacoordinated environment of these tin atoms 131.This point of view is supported by the present data-. all MSssbauer spectra show the presence of simple doublets, providing no evidence for distinguishable tin atoms. Whether from Herber’s criterion [lS] or from point charge calculations, the tin atoms must be considered to lie in a pentacoordinated geometry. The centre shift trend (cf. Table 1) increases with the increase of the electronegativity of the functional ligands [22]. In the present class of compounds, as with the class of triorganotin haloacetates previously examined [23-251. Introduction of haloacetate groups having increasing electron-acceptor properties tends to remove electron density from the tin atom through the carboxylate group. Thus halo-substitution increases the positive charge on the tin atom and the result is a deshielding of the 5sorbital which leads to an increase of the effective nuclear charge. The deshielding effect is more pronounced for compounds
TABLE
3
IR DATA FOR SOLID STATE
TETB.ABUTYL-l-TRICHLOROACRTOXY-3-IiYDROXYDISTANNOXANE
AND
IN SOLUTION
AND
MOLECULAR
Medium
Concentration wml).
Nuid
-
16504
Ccl4
6.4.~ b
1665% 1680s
=i = Mk&.
found/moLwt.
akd.
u,
(662.02).
WEIGHT
IN
MOW
5 ~oncentntion
THB
IN CC& (37°C) MoL ut found
i=
1342
2.03
3506mrnr)
3650m neax to a stunted
so~olution.
184
Fig_ of
2. PIot
type
A:
of quadmpole .s vinyl-.
splitting
against
0 butykiistannoxanes
Taft of
inductive
type
factor.
o vinyl-.
‘2 butyl-.
0 eUyl-distannoxane~
B.
of type A than for type B, since in the former four haloacetate groups are pre- . sent. On considering the quadrupole splitting values, we have found a linear correlation between the A values and the Taft factor u* of the R’ groups (cf. Fig. 2), consistent with the behaviour previously demonstrated for a series of triorganotin haloacetates R$SnOOCR (R = Me and Ph) [23-251. In Table 4 are listed the values of the slop.es p and the intercepts A0 (calculated quadrupole splitting value of the acetate) involved in the equation A = A0 + po’ for the five groups of compounds examined and for those previousiy reported. It will be seen that no significant differences, within the standard deviations, appear in the p-values
TABLE
4
LINEAR OF THE stxies
CORRELATION R’ GROUPS_
of kostruchxral
+po*J
BETWEEN
THE
A-VALUES
d Reported
value for the acetate, bObservcbvnlue values
THE
o*
TAFT
FACTOR
compounds
0.131
+ 0.04
853 * 0.09
0.135
* 0.03
3.29 t 0.05
3.26 + 0.03
0.137
= o.aos
3_16
-
in nt
24:
see eIso
nt
25,
0.119
*- 0.01
0_213
*
0.182
=
0.231
5 0_04Sd
lo;
6 o_oaiod 0.01
the acetate.
f
-
(100
283 265 ir 0.05 3ss f 0_02= 3.69 d 3.34d
0.113
* Cdctited
AND
C Our
erlcuhtion
2.64 867 3.68 3.36 from
data
_C0.03 * 0.04 % 0.03 k 0.03
of ref.
2%
185
inside each series of compounds; the values for the isostructural chain polymeric triorganotin derivatives 1241 are greater than those of the dimeric distannoxanes. The linear correlation found is significant in establishing that only electronic effects are important in determining the trend of the A values 1241. For trimethyltin derivatives it has been proposed [24] that the A trend arises from an increasing asymmetry of the two Sn-0 bonds with the increase of the o* of the haloacetate groups. This is consistent with structural data on the trimethyltin acetate and trifluoroacetate 124-261. Starting from this point of view, we suggest that within an isostructural series of compounds, the slope p assumes a vaIue which is in account for different structural parameters. It seems to us that the regular increase in the splitting quadrupole values for all the five groups of compounds examined can be related to the variation of parameters which characterise the isostructural skeleton of the very similar ladder-type dimeric structure formed by the Sri-0 bonds. In these compounds the influence of groups of increasing electron-acceptor ability might reinforce the carboxylate C-O bonds (cf. trend of the v,(COO) values, Table 1) and reduce the Sn---OOCR’ bonding. As a consequence the intra- and inter-molecular Sri-0 bonds become stronger. The effect of the structure packing is also revealed by comparing the A0 values of the distannoxanes of type B, which are lower than those of the distannoxanes of type A, this lowering probably being due to the presence of only two carboxylate groups in the former. Support for the above arguments comes also from analysing the trend of the A, values which concern acetate derivatives having different R groups around the tin atoms. In order to discuss this trend, the intercept values A0 (cf. Table 4) must be taken into consideration. On the basis of these values we obtain the following A0 trend order, vinyl (3.53) > butyl(3.29) > ally1 (3.15) for type A and vinyl (2.83) > butyl(2.65) for type B. The differences between these values do appear to be significant. It is notable that introduction of the different alkyl groups in an homologous series of distannoxanes does not cause any variation in the A values. Tetrabutyl-, tetraoctyl- and tetramethyl-1,3-(trimethylsiloxy)distannoxanes values: 2.46,2.45 and 2.42 respectively effects which could be produced organic groups employed. In our opinion, the Sn-0 bonds
stronger and more covalent [ 12,131, whereas the ally1 group has the opposite effect_ In other words, by comparison with the butyl group, these groups seem to promote a different packing in the dimeric molecule. Acknowledgment We are pleased to &knowledge support of this work to CNR, Roma, Grant
No. 75.01048.03. References 1 RO~-~M,Wa~Advur.OrpnometrlCbc~.5<1967)164.~d~f.thueia 2 y.~~chow.Ino~Chem.10(1971~673.
186 3
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26
R. Gnuiani. G. Bombieri. E FoxseXni. P_ Furlas V. Pe-o and G_ Ta&iavini. .I_ OrganometaL Cbem_. 125 <19-i’?) 43. A&. Davies. L. Smith. P.J. Smith and W. McFarIane. J. OrganometaL Chea, 29 (1971) 245. and ref. the&n. v_ PUUUO. G. Pknogna and G. TagIiavinI. J. OrganometaL Chem_. 40 (1972) 121. V_ Perozzo and Cl Ta&IavIni. J. Organomet8L Chem, 66 (1974) 437. V. Peruzzo. G. PIazzogna and G. TazIIavinL Gazz. Chbn It& 104 (1974) 767. LM_ K&ham&% O.Yu. OkhIobytin. A.V. POPOV and B-1. Rogosev. Dokl. Akad. Nauk. SSSR. 160 (1965) 112X V.I. Gol’danskii. EF_ ‘Makarov. R-k Stukas V-k Trukhtanov. and V-V_ Kirapov. DOW_ Phys_ Chem.. 151<1963) 598. V.I. Gol’danskii, V.V. Kbmpov. O.Yu. OkhIobysti and V.Ya Rochev. in V.I. Gol’danskii and R-H_ Herber (Eds). ChemIcaI Applications of Miissbauer Spectroscopy; Academic Press, N-Y.. 1968. Ch. 6. V. Pe-o. G. PIazzogna and G. TagIIavIoI. J. OrganometaL Chem_. 24 (1970) 347. RE Hester and D. bIascord. J_ O~ometaL Cbem.. 51<1973) 181. R.E Hester. in HA_ Szymanski cm). Raman Spectroscope. Plenum Press New York. 1967. K Kawakami and H.G. KuIviIa, J. 0s Chem.. 34 <1969) 1502. A SchweIg. U_ Weidner and G. Manuel. J. OrganometaL Chem. 54 (1973) 145. RV. Pa&band R.H. PI&t. J. Chem. Sot. A. (1969) 2145. B-L. Ck . T.A. TumoIilIo. Compu+ Phys. Commun.. 3 (1971) 322. RK Herber. H.k StiickIer and W.T. ReiehIe. J. Chem. Phys. 42 (1965) 2447. B.W. Fitzsimmons. N.J. 6eeIey and A-W_ Smith. J. Chem_ 6oc.. A. (1969) 143. G-M_ Bancroft. V.G. Kumar Das, T. K. Sham and M.G. CIark. J. Cbem. Sot.. Dalton, (1976) 643. R Okawam and M. Wada. J_ OqamxnetaJ_ Cbem, 1<1963) 81 R.V. Parish and R.H. PIatt. Inorg. ChIm. Acta. 4 <1970) 589. N-W-G_ Debye. D-E Fenton. S.E Ulrich and J.J. Zuckermao. J. Or@uometaL Chem_. 28 <1971) 339. B_F_E Ford and J-R Sams. J. ~ometat Chem_. 31 <1971) 47. C. Poderand J-R 3ams. J. OrgaoometaL Chem.. 19 (1969) 67. II_ Chib and B.R. Penfold J. Cryst. MoL Struct. 3 (1973) 285.