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S,N,N′-Substituted sulfurdiimines as ligands
Journal of OrgcmometaIZic Chemistry= 120 (1976) 285-295 @ Elsevier Sequoia S.A., Lausanne - Printed in The Netherlands
S,N,N’-SUBSTITUTED
SULFURDIIMINES
AS LIGANDS
H *- COMPOUNDS [(q3-RC3H,)Pd{R’NS(RZ)NR’)] ( R = H, CH,; R’ = ARYL; R2 = CH,, t-C4H9) AND SOME RELATED TRIAZENIDO AND AMIDINO COMPOUNDS OF PALLADIUM(I1)
P. HENDRIKS,
J. KUYPER
and K. VRIEZE
*
Anorganisch Chemisch Laboratorium, Universiteit van Amsterdam, Nieuwe Achtergracht 166, Amsterdam (The Netherlands)
J.H. van ‘t Hoff Instituut,
(Received April 20th, 1976)
The complexes [(q3-RC3H,)Pd{R’NS(R2)NR’}] (R = H, CH,; R’ = aryl; R2 = CH3, t-C,H,) have been obtained from the reaction of [(q3-RC3H4)PdCl12 with [Li{R’NS(R2)NR1)]; two isomers are produced, differing in the orientation of the ally1 group. The sulfurdiimino group has some n-allylic character. The compounds decompose in sol&ion into azocuenes and [(q3-RC3H4)Pd(SR’)]*, and this is shown to be dependent upon steric and electronic factors. The properties of the sulfurdiimino compounds are compared with those of the compounds [(q3-RC3H,)Pd(R3N3R3)] 2 and [ (q3-RCxHe)Pd(R3NC( R4)NR3) J2 (R = H, CH3; R3 = CH3, aryl; R4 = H, CH,), which have been prepared by new methods. Introduction Our interest in the chemistry of pseudo-allenic [l-4] and pseudo-allylic ligands [5-103 has recently focussed on sulfurdiimino, triazenido and amidino ligands (Fig. 1). The recently reported sulfurdiimino ligand may be formed by inserting N,N’substituted sulfurdiimines R’N=S=NR’ into metal-carbon bonds [5] (e.g. LiC *, Mg-C) analogous to the insertion of allenes [ll-131. Further reaction of with suitable metal compounds 15,153 afforded dimeric [Li{R’NS(R*)NR’)] complexes [M{R’NS(R2)NR’)]2 of copper(I) and silver(I), in which the ligand is bridging, and monomeric complexes [(C0)2Rh{R’NS(R2)NR’ )I, in which the ligand acts as a chelate and in its bonding characteristics bears a resemblance l For part I see ref. 15. * A ~ez&,i~n of ~CH3)gSiN=S=NSi(CH&
with LiCH3 has been reported cl41.
to -ir-allylbonding 1161. In solution the sulfurdiiminometal compounds may decompose, one of the products being an azo-ene. The ease of this process depends on both electronic and steric factors. In order to obtain more insight into the bonding of the sulfurdiimino ligand, complexes of palladium(E: have been prepared, along with palladium(I1) complexes of the formally analogous triazenido and formamidino ligands. During the course of this work, a .n.unber of triazenido and formamidino complexes of palladium(II) were reported by others [17,18]_ The complexes described here, some of them new, were prepared by different methods. The structure of one of them has been reported by us [9]. Experimental The preparations were carried out under dry nitrogen_ Solvents were dried carefully prior to use. Diaryltriazenes [19], diarylamidines [ZO], their silver salts [21-231, dimethyltriazenidosilver [7], S,N,N’-substituted sulfurdiiminolithium [E&15] and [~3-(methyl)allylPdCl]z [24] were prepared as described in the literature. Preparation of [(q3-RC&.&)Pd (R ‘NS(R’)NR 1) J (R = H, Me; R 1 = p-tolyl, pCICJ&, 35xylyl, 2,4&Lmesityl: R2 = Me, t-Bu) As an example, the preparation of [(q3-C,H,)Pd{MesNS(t-Bu)iiMes)] (Mes = 2,4,6-mesity!) is given. C(v3-GH7jPdc112(1 mmol) was added, with stirring, to a solution of [Li{MesNS(t-BujNMes)] (2 mmol) in ether (20 ml) at -30°C After 5 min the solution was evaporated to dryness under vacua. The residue was dissolved in cold hexane (20 ml) and LiCl was removed by filtration. At -35°C yellow crystals were obtained in 80% yieldAll methallylpalladium compounds are soluble in ether except for the p-Cl&H, derivatives. In this case, and with the allylpalladium compounds, the residue was dissolved in cold benzene. LiCl was removed quickly, and cold hexane was added to induce crystallization in the cold (-20°C). Preparation of [(q3-RC&)Pd(SR2)]2 (R2 = t-Bu) t-BUSH (1.0 mmol) was added to a solution of [(s3-CaH,)PdCl]Z in CHC13 (20 ml)_ After 3 h stirring the solution was filtered and evaporated to dryness. The residue was crystallized from benzene/hexane to give orange crystals in 85% yieldPrepamfion of q3-(methyl)allyl- triazenido- and -amidino-paltadium compounds * * Analogous
compounds have been prepared 181. am3 by Jeck and Powell [301-
in a different
way by Candeloro
De Sanctis et a.L [17.
Method I Preparation of [(q3-RC3H4)Pd(DMT)J2 (R = H, CH,; DMT = dimethyltriazenido). Dimethyltriazenidosilver (2.0 mmol) was dissolved in benzene (20 ml) and [(q3-RC3H4)PdC1]2 (1.0 mmol) was added. After 1 h the precipitated AgCl was removed by filtration and the solution was evaporated to dryness under vacuum. The residue was recrystallized from ether. Yellow prisms were obtained in about 75% yield. Preparation of [(v3-RCJI,)Pd(ArN,Ar)], (Ar = p-tolyl, p-ClCJ&, 3,5-C1&H3, Z,4,6-CZ3C6r,)_ Equivalent amounts (2 mmol) of diaryltriazenidosilver and [(?j3 RC,H,)PdCl], were heated under reflux in benzene (20 ml)_ After 1 to 2 h the AgCl was removed by filtration and the solution was evaporated to dryness under vacuum_ The residue was recrystallized from benzene/hexane or chloroform/hexane and yellow crystals were obtained in about 75% yield. Method II Preparation of [(q3-RC&)Pd(ArN,Ar)], (Ar = as above). Diaryltriazene (2.0 mmol) was added to a chloroform solution of [(q3-RC3H4)PdC112 (1 mmol). Subsequently KO-t-Bu (2.0 mmol) was added to the solution of [(q3-RC3H4)PdCl(diaryltriazene)] *. After 5 min the precipitated KC1 was removed by filtration and the solution was worked up as above. The yields were about 85%. When KOH was used instead of KO-t-Bu a reaction time of 30 min was needed, and the yields were about 60%. ~3-(Methyl)allylditolyl-formamidino and -acetamidino-palladium were prepared according to methods I and II. C, H and S analyses were carried out in this laboratory (Table 1). 13C and ‘H NMR spectra were recorded with a XL 100 Varian spectrometer, IR spectra with a Beckmann 4250 spectrometer. Molecular weights were measured with a Hewlett-Packard vapour pressure osmometer Model 320 B. Results S,N,N’-substituted
sulfurdiimino(methyl)allylpalladium compounds
[(q3-RC3H4)PdCl]2 + 2Li{R’SN(R’)NR’} + [ (q3-RC3H4)Pd { R’NS(R*)NR’
]] + 2Li
(I)
The compounds are monomeric (Table 1) and both R’ groups are equivalent (Table 2). The characteristic NSN vibrations (Table 3) are in the ranges of 850910 and 1190 to 1250 cm-‘. Both NMR shifts and IR vibrations correspond well with those of [(CO),Rh {R’NS(R’)NR’ )] [5,15] which are also monomeric. Therefore, the sulfurdiimino group is bonded as a chelate and probably also has some a-allylic character 1161. Depending on the orientation of the ~3-(methyl)allyl groups two isomers can exist (Fig. 2), and these were indeed observed at low temperature. At higher temperatures the resonances of the two isomers merge which shows that the two isomers interconvert, except for the compounds [(q3-RC3H4)Pd* &Ionomeric ~yltriazenepalladium-complexes by Boschi et al. L251.
have been prepared
recently
and are fully
discussed
* DpTT = di-p.toIyItrInzenIdo; DpClPT = di-y.chlorophcnyltriuzenido: trbzenIdo; DMT = dlmcthyltriazenldo; DpTP = di-p.tolylformamidino;
[(v3-C$r#d(DpTA)12 [(t13-C&)Pd(DpTW2 [(q3-C.&)Pd(DpTA)12
[h3-C&)Pd(DMT)l 2 [(q3-C$Is)Pd(DpTF)12
[(r13-C~I~#‘d(DMT)12
I(s3-C&)Pd(DpTT)12 [(t13-C#17)Pd(DpCIPT)12 I(r13-C4117)Pd(D.3,6.C12PT)12 [(t13-C41i,)Pd(D.2,4,6.C13PT)]2
6,08(6.27) 4.36(4.G1) G.83(6.7G) 7.12(7,17) 6.28(6,52) 4.20(4.71) 7.36(7.00) 7,40(7,40) G.lO(6.02) 6.41 (G,G2) 6.10(6,12) 3.23(3,16) 2.20(2.29) 1*70(1.64) 5,4O(G.46) 3.60(3.62) 2.59(2.63) 1.99(1.98) 4.98(6.02) G.GZ(5.G8) 5.35(G.41) B.70(5.73) bGE(5.73) 6,05(6.03)
--_-_-
I-i
(a) _---_-
-I ---I
G,H6(6.20)
6,24(6.95) 6,18(6.38)
5,95(G,57)
s
.
= di(2,4,6.trIchloro)phcnyb
798(768) 851(79(1)
422(438) 441(466)
1071(890)
1131(1092) 760(770)
758(742)
4GO(GOl) 484(488) blO(516)
410(44G) 488(502)
.
Mol,wt. found (cnlcd.)
p2,4,6+PT
.---
b3NW4)NR3)lz
D.3,6-C12PT = di(3,G~di~chloro)phcnyltrlnzcnIdo; DpTA = dl~p~tolylacctamidino.
55.48(5G.50) 46,10(46.82) 57.98(58,23) 59,56(69,7G) 56.76(57,39) 47.18(47,90) 68.00(58.95) GO.20(60.46) 54.86(55,66) G7.01(57.39) 64.76(64,99) 43.62(43,69) 37.38(37,42) 32,59(32.73) 55.77(66.10) 44.90(45.07) 38.60(38,79) 33.94(34,04) 27.02(27,40) 31.12(30.90) 57.61(58,3S) 88.91(69.38) 58.75(59.38) 69.96(00.30)
._._-..-
C
Analysis found (wlcd,)
_-_
[(t13~RC311,+)Pd {It”N3R3)l~ AND W?4WLW
___“___,,“--_-I.v--
{R’NS(RZ)NR’}l,
S.t.Bu~N,N’~l.~.tolyI(NSN)}l S~t~Bu~N,N’~i~(4~Cl~pI~e~~yl)(NSN)}l ‘Jbt-Bu.N,N ‘&3,6-xylyl(NSN)}l ~~~L-Bu-N,N’~l~2,4,6~mesltyl(NSN)}l ‘:S.t.Bu-N,N’~ip.tolyl(NSN)}l .~~t.Bu-N,N’~i(4-Cl.ph~~yl)(NSN)}l +Bu-N,N’&3,5-xylyl(NSN)}l +Bu-N,N’111~2,4,&medtyl(NSN)}1 .Me.N,N’dI-3,5~xylyl(NSN)}I -Me-N,N ‘~1.2,4,6-mcsityl(NSN)}l
_ -......--_---
DATA FOR [(+Rc3ki4)Pd
t(q3-C&)Pd(DpTT)I2 [(t13-C$IS)Pd(DpCIPT)12 [(~3-C3115)Pd(D.3,G.C12PT)]~ [(~3-C311S)Pd(D.2,4,6.C13PT)]*
[(q3-C&)Pd [(q3-C$I#d [(q3-C$IS)Pd [(q3.C3Bs)Pd [(q3-Qti7)I’d [(q3-C&)Pd
Compound ’
--__l-.._l._-__---
ANALYTICAL
TABLE 1
289
R
Fig.2. PossibIeisomersof
L(~~~-RC~H,)P~{R'NS
)I-
{MesNS(t-Bu)NMes )]. In this case the isomers do not interchange at 35°C. The similarity with the rhodium compounds is also demonstrated by the decomposition which generally takes place in solution at ambient temperatures and which leads to azocuenes. The palladium compounds offer the additional advantage that the decomposition can be more fully studied, as the SR- group can be captured in the form of f(q3-RC3Hq)Pd(SR2)la, which contains a bridging mercapto group. This was confirmed by comparing the NMR data of the decomposition products with those of a mixture of azoarenes and [ (77’-RC3H4)Pd(SR2)12. The mechanisms of the decomposition are discussed below. Of interest is that, in contrast to the compound [(CO),Rh{MesNS(t-Bu)NMes}], the mesityl groups of the corresponding (methyl)allylpalladium compound can freely rotate (Table 2) above +lO”C. This agrees with the observation that the rhodium compound mentioned above, in which the mesityl groups do not rotate, is stable to decomposition into azo-arene, while the palladium compounds are not. The rate of decomposition showed the following orders: S-Me > S-t-Bu and p-to1 > p-Cl&H4 > 3,5-xylyl > 2,4,6-mesityl. Owing to rapid decomposition the S-Me-N,N’-ditolyl- and the S-Me-N,N’-di@-ClC,H,)-sulfurdiimino derivatives could not be isolated_ Triazenido- and amidino-(methyl)allylpalladium compounds The complexes, some of which are already known [17,18,30] by two new methods: [(n3-RC3H4)PdC1]2 + BAg(DMT) + [(q3-RC,H,)Pd(DMT)]z
were obtained
+ 2AgCl
(2)
[(q3-R&H4)PdCl]2 + 2DpTTH + BKO-t-Bu --f [(q3-RC,H,)Pd(DpTT)]2
+ 2KCl+
BHO-t-Bu
(3)
On the basis of molecular weights (Table l), crystal structures of [ (q3-C4H7)Pd(MeNsMe)lZ [9] and of [(q’-C3HS)Pd {p-MeC6H4N3C6H4@-Me) )I2 [ 261 and of
IR data (v,,(NNN) - 1350-1375 cm-‘, characteristic for a bridging triazenido group 171) (Table 4), it was -oneluded that all compounds are dimeric and have
bridging triazenido or amidino groups. It has already been pointed out [17,18, 301 that three isomers are possible, in principle, in the case of the ally1 compounds (Fig. 3), depending on the orientation of the ally1 group. Two of these have been observed up till now [17,18,30]. The third isomer was also found, and occurs in all our compounds except for [(q3-C3HS)Pd{ (2,4,6-Cl&H2)Ns(2,4,6-C13GH*) 112,which exists in solution in only one isomeric form. In the
IH NEAR DATA FOR rel. to TMS) n.o.=not
L&-Rc3H4)Pd{~'~~(~2)~R')3 AND L(n3-RC3H4)Pd(sRZ)lt observcd:d =doublet.m = multiPIet Solvent
Compound
L<&C3Hs)Pd{S-t-Bu-.V..V'di-.+tolYl(NSN)}l L
C7D8 C7D8 CGD6 C6D6 C6D6 C6D6 C7DS C7Ds C7Ds C6D6 C7Ds C7Ds C7D8 C6D6 C7D8 C7D8 C7D8 C6D6 C6D6 C7D8 C7D8 C7D8
+30 -l-30 0 -60 -60 +30 +30 +30 +30 0 -60 -60 130 0 -60 -60 +30 0 -60 --6O c30 i-30 +10 +10 -0
C7D8
-60
C6D6 C6D6 C7Ds
[(q3-CqH7)Pd{S-t-Bu-X.N'-di-2.4.6-mesityl(NSN))l
[(+C3H5)Pd{S-Me-i\i.N'-di-2.4.6~mesitYl(NSN))l L
T ("0
C6D6 C6D6 C6D6 C6D6
+30 +30 +30 t30
ISOmer
(chemicaishifts inppm
Resonancesofthe ~YigrOUP anti
SYR
Ii I II I II I
3.33 3.17(d) 3.20(d) 3.19(d) 3.03(d) 3.43(d) 2.62(d) 2.85(d) 3-27 3.28 3.29 3.20 3.16 3.18 3.11 3.03 3.33 3.36 3.36 3.32 2.48 2.68 2.45 2.69 2.57
2.13(d) 2.12(d) no. 1.70(d) 2.22(d) 2.20(d) 2.17(d) 1.88(d) 2.17 n-o. 1.90 2.42 2.03 n-o. 1.73 2.29 2.10 2.15 1.88 n-o. 2.13 1.85 2.13 1.83 n-0.
II
2.61
1.73
2.23(d) 3.75(d) 3.61 3.37
2.03(d) 2.57(d) 2.54 2.33
I II
I Ii
I
II
I II
I
case of the methallylpalladium compounds only one isomer (I) is possible for steric reasons (Table 5). In contrast to the monomeric sulfurdiimino compounds the dimeric triazenido compounds are very stable in solution and they strongly resist bridge fcontinued OR p_ 293)
1
Fig.3.PossibleiSomenof
II L(~3-C3Hs)Pd{R3NNNR3)lz
m and C
291
H.Me
Resonances of the sulfurdiimina ligands s-tble(aryl) ArYl Bl.l.Me
n.on-o. n-o. n.o. n.o. n.o. n-0. 1.63 1.74 1.69 1.90 1.53 1.49 1.58 1.73 1.68 1.77 1.70 1.88 1.4i 1.73 1.47 1.76 1.30
1.20 1.05 1.02 0.94 0.97 1.26 0.93 0.87 1.21 1.20 1.12 1.18 1.10 1.02 0.96 0.99 1.27 1.25 1.21 1.26 0.93 0.87 0.91 0.86 0.84
1.61
0.77
6.78;(n.o.)
4.73m 4.60111 1.58 1.63
3.34 1.47 1.51 2.50
6.60
ILO.
6.93 7.07.6.62 7.075.64 7.16;6.56
2.18
6.72l6.37 6.80
2.20
6.97 6.97~6.85 7.03x6.84
2.77c2.18 2.20 2.19 2.26
7.11:6.67 7.08r6.63 7.16~6.56 6.68~6.53 6.66;6.34 6.75~6.45 6.80
2.22 2.21 2.33 2.26 2.78;2.18
6.82
2.78:2.17
6.835.73
2.69;2.19 2.16 2.54:3.08 2.16 2.33:2.01
TABLE3 INFRAREDDATA(KBrdisk)
FOR [(q3-RC3fi4)Pd{~'~S(RZ)NR'}]
Compound
v(NSN)" 1237 1242 1245 1218
a Frequencies characteristic for this group.
~Ncm-1
891 897 890 853
292 TABLE
4
INFRARED IN cm-I Compound
DATA
(KBr
disk)
FOR
[(n3-RC3H4)Pd
a
v(triazenIdo.amidIno) 1357(v&: 1366(v,): 1363(u,): 1357(Ua& 1366(V,s); 1363(pa,): 136O(vas); 1572
t(03-CsHs)Pd(DMT)]+ t(s3-C311g)Pd(DpTT)17 C(n3-C3Hs)Pd(DpCIPT)J2 I(r13-C~II,JPd(DMT)12 t(n3-GtH7)Pd(DpTT)Jt E(s3-C4H7)Pd(DpClPT)l* C(~3-C4H,)Pd(D-2,4,6-C13PT)IZ C(n3-C3Hg)PdWpTF)Jz t<123-C311SJPd(DpT-~)]2 C(n3-C4H7)Pd(DpTF)32 C(s3-GzII,)Pd(DpTA)IZ = See note a of Table T-ABLE
{R3N3R3)37
1. b A tentative
assignment
AND
C(n3-RC3Ii4)Pd
b
{R3NC(R4)NR5}]7
6(NNN) 630 600 593 631 620 609
1338: 1189Ws) 1322: 1206(vs) 1323: lZOl(vs) 1337: 119O(vs) 1317; lZlO(Vs) 1317: 1205(vs) 1329; 1212(vs) 135O(vs) 1255Ws) 1349(Q) 1254(vs)
is given of the bending
b
vibration_
5
lII NLIR DATA FOR C(q3-RCaH4)Pd(R3NaR3)l 12 AND L(n3-RC3H4)Pd {R3NC(R4)NR3}l (ii ppm rel. to TMS) no. = not observed; d = doublet: t = triplet; q = quartet Compound
a
lsomer
Resonances
QVZ-H
anti-H
H.CHJ
2.52(d) 2.40(d) 2.79(d) 2.66(d) 2.76(d) 2.66(d) 2.96(d) 2.96(d) 2.80(d) 2.69(d) 295(d) 2.95(d) 2.90(d) 2.80(d) 3.12(d) 2.95(d) 3.08(d) 2.79(d) 2.71(d) 2.89(d)
3.50(d) 3.38(d) 3.62(d) 3.55(d) 3.66(d) 3.60(d) 3.70(d) no _ 3.74(d) 3.65(d) 3.80(d) n-o. 3.92(d) 3.84(d) 3.97(d) no. 3.73(d) 3.56(d) 3.49(d) 3.66(d)
5.37(m) 4.74(m) 5.49(m) 4.84(m) 5.85(m) 5.00(m) 5.85(m)
I II III I II
I(q3-C3tIs?Pd(DpTT)Ja
III I II
[(n3-C5Iis)Pd(D-3.5ClgPT)12
III I II
[(n3-C3Hs)Pd(D-2.4.6-CI3PT)Jz [(n3-C3H5)Pd(DpTF)Iz
III I I iI III I II
[(rj3-C3Hg)Pd(DpTA]12
III L(n3-C4H7)Pd(D~T)Jz [(n3-C4H,)Pd(DpTT)], [(~3_C4H7)Pd(DpCIPT)]2 [(q3-C4H7)Pd(D-3S-CI$‘T)]2
[<~3-C4H1)Pd
of the ally1
group
2.83(d) 2.69(d) 2.34(d) 2.60(d) 2.25(d) 3.33 3.49 3.56 3.66 3.40 3.33 2.88
1. ’ Not aII frequencies
f:&(d) 2.92(d) 3.38(d) 3.31 (d) 2.34 2.75 2.79 2.81 3.23 2.63 2.49
could be assigned
IN CDC13
Resonances of the trkxrenido(amidino) Iigands Aryl
b
CII3(arYI)
H.CH3
3.35 3.30(q) 3.58(q) 3.50 6_9(d):7_3(d)
= 2.27
ILO.
5.75(m) 5.10(m) 5.75(m) n-0 _ 5.80(m) 5.10(m) 5.80(m)
l.l
n.0.
7_00(t):7_33(d) 6.96(t);7.28(d) 7_03(t);7_42(d) 7.OO(t):7.38(d) 7.24 6.96 6.89 7.03 7.00
5.15(m)
6-7
2.13 2.27 2.24 2.37 1.93 2.28 1.78
6.96(d):7.41(d) ?.ll(d):7_39(d) 7.OO(t);7.4O(d) 7.20 6.93 6.57(d);6.85(d)
ll.0.
5.30(m) 5.35(m) 4.70(m) 5.35(m)
because
’
7.84 2.28 7-77 7.69 2.27 2.28 2.31 2.25
=
1.66
3.40
of overkp.
c 4 AA’XX’
2.27
2.26 2.27
7.78 1.68
patterns
293
breaking by most ligands. Within the NMR time scale there is no fluxional behaviour of the (methyl)allyl groups for both the triazenido * and amidino ** compounds between -50 to +115OC as indicated by ‘H and i3C NMR measurments. The triazenido and amidino groups can be replaced in chloroform by other more acidic triazenes or amidines. The order of ease of replacement is: Di-ptolylacetamidine < dimethyltriazene < di-p-tolylformamidine < di-p-tolyltriazene < di-p-Cl-phenyltriazene. Discussion Comparison of the S,N,N’-substituted sulfurdiimino compounds of rhodium(1) and palladium(H), in which the ligand acts as a chelate, shows that there is a close structural relationship. Because of the presence of the (methyl)allyl group in the case of palladium(I1) two isomers are possible in principle (Fig. 2), and are indeed observed. Except in the case of [(q3-RC3H4)Pd {MesNS(t-Bu)Mes )] these isomers interconvert at room temperature in the NMR time-scale_ There is also a strong chemical relationship between the palladium and rhodium compounds_ In both cases the decomposition of the compounds of rhodium(I) and palladium(I1) proceeds similarly. The palladium compounds decompose more rapidly than the rhodium compounds at +35”C. The order of decomposition rates is, in the case of palladium(H): S-Me > S-t-Bu and R’ = p-tolyl > p-Cl-phenyl > 2,4,6-mesityl, which corresponds well with that found for rhodium. The decomposition reaction involves the formation of azoaLenes and SR-, but only in the case of palladium(I1) could the formation of SR- be demonstrated conclusively, by isolation of [(q3-RC3H4)Pd(SR2)]z. On the basis of the electronic and steric influences on the decomposition rates the following mechanism is proposed (Fig. 4). The first step is probably an attack of the metal atom on the sulfur atom via a n-allylic intermediate, which agrees with the observed steric influences. In the case of R’ = 2,4,6-mesityl the formation of a a-allylic intermediate or a direct intramolecular attack of the metal atom on the sulfur atom is strongly hindered by the two ortho-methyl groups which point between the metal atom and the sulfur atom (see crystal structure of [(C0)2Rh{MesNS(t-Bu)NMes}] [15,16]). The steric hindrance can be diminished, if the mesityl groups can rotate, which is the case when S-t-Bu is replaced by S-Me. Consequently the rate of decomposition is much higher in the case of the S-Me substituted compound than in the case of the S-t-Bu compounds. We can also now understand why the p-tolyland p-Cl-phenyl substituted compounds decompose more rapidly than the 2,4,6mesityl derivatives_ The rate increasing effect of electrondonating R’ groups on the azo formation i.e. ringclosure of the S,iV,N’-moiety becomes clear from a comparison
* In accord with previous findings [17.30]. ** Flu-xional bebavioux was proposed previously that the reported merging of the appropriate of the chemical shifts without broadening_
[18] on the basis of ‘II spectra only. We conclude signals is due only to temperature dependent changes
294
R
iv ’ .,
_____w-
LR
d
J
-6
‘N=
4
2
N,
Fig_ 4. Proposed
R’ mechanism
for
the
formation
of azo-arenes
and C:~3-RC~H4)Pd
with O=S=O_ The O-S-O angle decreases and the S-O bond length increases with increasing negative charge, since extra electronic charge will go into an orbital with S-O antibonding and O-O bonding character [ 271. Comparison of the S,N,N’-sulfurdiimino group with the triazenido or amidino group bonded to palladium(I1) shows that the first ligand prefers to be bonded as a chelate, whereas the last two ligands are bridging *. It should be noted here that the azenido group may bond as a chelate, a bridging ligand or as a monodentate [28], while the S,N,N’-sulfurdiimino has only been observed, up till now, to occur as a bridging ligand or as a chelate. The absence of the monodentate form is probably due to the fast decomposition into azo compounds. The general occurrence of three isomers in the case of the q3-allyl-triazenidoand arnidino-palladium compounds agrees well with the expected possibilities (Fig. 3). The presence of only isomer I in the case of [(q3-C3K,)Pd{2,4,6-C13CsH,)N,(2,4,6-Cl,C,I-I,) ]] is probably due to the fact that, in the isomers II and III, there is steric interaction of the ally1 moieties with the ortho-Cl atoms. Steric interactions are also probably the reason why, in the case of the methally1 compounds, only isomer I was observed. Finally we wish to note that the vas(NNN) in the IR spectra was found in the region of 1350-1375 cm-’ **, which is an additional support for our assignment in previous papers of bridging triazenido groups [6,7]. Acknowledgement We thank Mr. D. Prins for the analysis and Dr. A. Oskam for valuable help and discussions. The investigations were supported by the Netherlands * It
should be noted that a chelate azenido is not the use for the S.h’,N’-suIfurdiimio
group liesin a PIam? with the metal atom c28.291. This grouP which is more n-all~licin its mode of bonding
C161. ** These data differ from those of others I17.181.
295
Foundation for Chemical Research (SON) with financial aid from the Netherlands Organization for the Advancement of Pure Reseach (ZWO). References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
J. Kuyper and K. Vrieze. J. Organometal. Chem.. 74 (1974) 289. J. Kuyper and K. Vriere. J. Organometal. Chem.. 86 (1975) 127. J. Kuyper. P-1. van Vhet and K. Vrieze. J. Organometal. Chem.. 108
(1976)
J. Kuyper. L.G. Hubert-Pfalzgraf. P.C. Keijzer and K. Vrieze, J. Organometal. J_ Kuyper and K. Vrieze. J. Chem. Sot. Chem. Commun.. (19i6) 64.
257. Chem.,
108
(1976)
271.
J. Kuyper. P-1. van VIiet and K. Vrieze. J. Organometal. Chem.. 96 (1975) 289. J. Kuyper. P-1. van Vfiet and K. Vrieze. J. Organometai. Chem.. 105 (1976) 379. E. Pfeiffer. J. Kuyper and K. Vrieze. J. Organometal. Chem.. 105 (1976) 371. P. Hcndriks. K. Olie and K. Vriere. Cryst. Struct. Comm.. 4 (1975) 621. E. Pfeiffer and K. OIie. Cryst. Struct. Comm.. 4 (1975) 605. R-G. Schultz. Tetrahedron. 20 (1964) 2809. MS. Lupin and B.L. Shaw. Tetrahedron Lett., (1964) 883. J. Tsuji and T. Susuki. Tetrahedron Lett.. (1965) 3027. O.J. Schcrer and R. Schmidt. J. Organometal. Chem.. 16 (1969> Pll. J. Kuyper. P.C. Keijzef and K. Vrieze. J. Organometal. Chem.. 116 (1976) 1. H. van der Meer. Cryst. Struck Comm.. to be published. S. Candeloro De Sanctis. L. Toniolo, T. Boschi and G. Deganello. Inorg. Chim. Acta.. 12 (1975) 251. L. Toniolo. T. Boschi and G. Deganello. J. Organometal. Chem., 93 (1975) 405. Iiouben-Weijl, Methoden der Organischen Chemie, Part 1013. Thieme. Stuttgart, 1965. p. 699 etc. E.C. Taylor and W. Ehrhart. J. Org. Chem.. 28 (1963) 1108. F-P. Dwyer. J. Amer. Chem. Sot.. 63 (1941) 78. W. Bradley and J. Wright J. Chem. Sot.. (1956) 640. J. Kuyper and K. Vrieze. J. Organometal. Chem.. 107 (1976) 129. F.R. Hartley and S. Jones. J. Organometal. Chem., 66 (1974) 465. T. Boschi. L. Toni010 and U. BeBuco. to be pubhshed. S. Candeloro De Sanctis. N.V. Pave1 and L. Toniolo. J. Organometal. Chem.. 108 (lSi6) 409. P.D. Dacre and AI. Eider. Theor. Chim. Acta. 25 (1972) 254. hl.Corbett and B-F. Hoskins. Chem. Commun. (1968) 1602. K.R. Laing. SD. Robinson and M.F. Uttley. J. Chem. Sot.. Dalton. (1974) 1205. T. Jack and J. Powell. J. Organometal. Chem.. 27 (1971) 133.
S,N,N’-SUBSTITUTED
SULFURDIIMINES
AS LIGANDS
H *- COMPOUNDS [(q3-RC3H,)Pd{R’NS(RZ)NR’)] ( R = H, CH,; R’ = ARYL; R2 = CH,, t-C4H9) AND SOME RELATED TRIAZENIDO AND AMIDINO COMPOUNDS OF PALLADIUM(I1)
P. HENDRIKS,
J. KUYPER
and K. VRIEZE
*
Anorganisch Chemisch Laboratorium, Universiteit van Amsterdam, Nieuwe Achtergracht 166, Amsterdam (The Netherlands)
J.H. van ‘t Hoff Instituut,
(Received April 20th, 1976)
The complexes [(q3-RC3H,)Pd{R’NS(R2)NR’}] (R = H, CH,; R’ = aryl; R2 = CH3, t-C,H,) have been obtained from the reaction of [(q3-RC3H4)PdCl12 with [Li{R’NS(R2)NR1)]; two isomers are produced, differing in the orientation of the ally1 group. The sulfurdiimino group has some n-allylic character. The compounds decompose in sol&ion into azocuenes and [(q3-RC3H4)Pd(SR’)]*, and this is shown to be dependent upon steric and electronic factors. The properties of the sulfurdiimino compounds are compared with those of the compounds [(q3-RC3H,)Pd(R3N3R3)] 2 and [ (q3-RCxHe)Pd(R3NC( R4)NR3) J2 (R = H, CH3; R3 = CH3, aryl; R4 = H, CH,), which have been prepared by new methods. Introduction Our interest in the chemistry of pseudo-allenic [l-4] and pseudo-allylic ligands [5-103 has recently focussed on sulfurdiimino, triazenido and amidino ligands (Fig. 1). The recently reported sulfurdiimino ligand may be formed by inserting N,N’substituted sulfurdiimines R’N=S=NR’ into metal-carbon bonds [5] (e.g. LiC *, Mg-C) analogous to the insertion of allenes [ll-131. Further reaction of with suitable metal compounds 15,153 afforded dimeric [Li{R’NS(R*)NR’)] complexes [M{R’NS(R2)NR’)]2 of copper(I) and silver(I), in which the ligand is bridging, and monomeric complexes [(C0)2Rh{R’NS(R2)NR’ )I, in which the ligand acts as a chelate and in its bonding characteristics bears a resemblance l For part I see ref. 15. * A ~ez&,i~n of ~CH3)gSiN=S=NSi(CH&
with LiCH3 has been reported cl41.
to -ir-allylbonding 1161. In solution the sulfurdiiminometal compounds may decompose, one of the products being an azo-ene. The ease of this process depends on both electronic and steric factors. In order to obtain more insight into the bonding of the sulfurdiimino ligand, complexes of palladium(E: have been prepared, along with palladium(I1) complexes of the formally analogous triazenido and formamidino ligands. During the course of this work, a .n.unber of triazenido and formamidino complexes of palladium(II) were reported by others [17,18]_ The complexes described here, some of them new, were prepared by different methods. The structure of one of them has been reported by us [9]. Experimental The preparations were carried out under dry nitrogen_ Solvents were dried carefully prior to use. Diaryltriazenes [19], diarylamidines [ZO], their silver salts [21-231, dimethyltriazenidosilver [7], S,N,N’-substituted sulfurdiiminolithium [E&15] and [~3-(methyl)allylPdCl]z [24] were prepared as described in the literature. Preparation of [(q3-RC&.&)Pd (R ‘NS(R’)NR 1) J (R = H, Me; R 1 = p-tolyl, pCICJ&, 35xylyl, 2,4&Lmesityl: R2 = Me, t-Bu) As an example, the preparation of [(q3-C,H,)Pd{MesNS(t-Bu)iiMes)] (Mes = 2,4,6-mesity!) is given. C(v3-GH7jPdc112(1 mmol) was added, with stirring, to a solution of [Li{MesNS(t-BujNMes)] (2 mmol) in ether (20 ml) at -30°C After 5 min the solution was evaporated to dryness under vacua. The residue was dissolved in cold hexane (20 ml) and LiCl was removed by filtration. At -35°C yellow crystals were obtained in 80% yieldAll methallylpalladium compounds are soluble in ether except for the p-Cl&H, derivatives. In this case, and with the allylpalladium compounds, the residue was dissolved in cold benzene. LiCl was removed quickly, and cold hexane was added to induce crystallization in the cold (-20°C). Preparation of [(q3-RC&)Pd(SR2)]2 (R2 = t-Bu) t-BUSH (1.0 mmol) was added to a solution of [(s3-CaH,)PdCl]Z in CHC13 (20 ml)_ After 3 h stirring the solution was filtered and evaporated to dryness. The residue was crystallized from benzene/hexane to give orange crystals in 85% yieldPrepamfion of q3-(methyl)allyl- triazenido- and -amidino-paltadium compounds * * Analogous
compounds have been prepared 181. am3 by Jeck and Powell [301-
in a different
way by Candeloro
De Sanctis et a.L [17.
Method I Preparation of [(q3-RC3H4)Pd(DMT)J2 (R = H, CH,; DMT = dimethyltriazenido). Dimethyltriazenidosilver (2.0 mmol) was dissolved in benzene (20 ml) and [(q3-RC3H4)PdC1]2 (1.0 mmol) was added. After 1 h the precipitated AgCl was removed by filtration and the solution was evaporated to dryness under vacuum. The residue was recrystallized from ether. Yellow prisms were obtained in about 75% yield. Preparation of [(v3-RCJI,)Pd(ArN,Ar)], (Ar = p-tolyl, p-ClCJ&, 3,5-C1&H3, Z,4,6-CZ3C6r,)_ Equivalent amounts (2 mmol) of diaryltriazenidosilver and [(?j3 RC,H,)PdCl], were heated under reflux in benzene (20 ml)_ After 1 to 2 h the AgCl was removed by filtration and the solution was evaporated to dryness under vacuum_ The residue was recrystallized from benzene/hexane or chloroform/hexane and yellow crystals were obtained in about 75% yield. Method II Preparation of [(q3-RC&)Pd(ArN,Ar)], (Ar = as above). Diaryltriazene (2.0 mmol) was added to a chloroform solution of [(q3-RC3H4)PdC112 (1 mmol). Subsequently KO-t-Bu (2.0 mmol) was added to the solution of [(q3-RC3H4)PdCl(diaryltriazene)] *. After 5 min the precipitated KC1 was removed by filtration and the solution was worked up as above. The yields were about 85%. When KOH was used instead of KO-t-Bu a reaction time of 30 min was needed, and the yields were about 60%. ~3-(Methyl)allylditolyl-formamidino and -acetamidino-palladium were prepared according to methods I and II. C, H and S analyses were carried out in this laboratory (Table 1). 13C and ‘H NMR spectra were recorded with a XL 100 Varian spectrometer, IR spectra with a Beckmann 4250 spectrometer. Molecular weights were measured with a Hewlett-Packard vapour pressure osmometer Model 320 B. Results S,N,N’-substituted
sulfurdiimino(methyl)allylpalladium compounds
[(q3-RC3H4)PdCl]2 + 2Li{R’SN(R’)NR’} + [ (q3-RC3H4)Pd { R’NS(R*)NR’
]] + 2Li
(I)
The compounds are monomeric (Table 1) and both R’ groups are equivalent (Table 2). The characteristic NSN vibrations (Table 3) are in the ranges of 850910 and 1190 to 1250 cm-‘. Both NMR shifts and IR vibrations correspond well with those of [(CO),Rh {R’NS(R’)NR’ )] [5,15] which are also monomeric. Therefore, the sulfurdiimino group is bonded as a chelate and probably also has some a-allylic character 1161. Depending on the orientation of the ~3-(methyl)allyl groups two isomers can exist (Fig. 2), and these were indeed observed at low temperature. At higher temperatures the resonances of the two isomers merge which shows that the two isomers interconvert, except for the compounds [(q3-RC3H4)Pd* &Ionomeric ~yltriazenepalladium-complexes by Boschi et al. L251.
have been prepared
recently
and are fully
discussed
* DpTT = di-p.toIyItrInzenIdo; DpClPT = di-y.chlorophcnyltriuzenido: trbzenIdo; DMT = dlmcthyltriazenldo; DpTP = di-p.tolylformamidino;
[(v3-C$r#d(DpTA)12 [(t13-C&)Pd(DpTW2 [(q3-C.&)Pd(DpTA)12
[h3-C&)Pd(DMT)l 2 [(q3-C$Is)Pd(DpTF)12
[(r13-C~I~#‘d(DMT)12
I(s3-C&)Pd(DpTT)12 [(t13-C#17)Pd(DpCIPT)12 I(r13-C4117)Pd(D.3,6.C12PT)12 [(t13-C41i,)Pd(D.2,4,6.C13PT)]2
6,08(6.27) 4.36(4.G1) G.83(6.7G) 7.12(7,17) 6.28(6,52) 4.20(4.71) 7.36(7.00) 7,40(7,40) G.lO(6.02) 6.41 (G,G2) 6.10(6,12) 3.23(3,16) 2.20(2.29) 1*70(1.64) 5,4O(G.46) 3.60(3.62) 2.59(2.63) 1.99(1.98) 4.98(6.02) G.GZ(5.G8) 5.35(G.41) B.70(5.73) bGE(5.73) 6,05(6.03)
--_-_-
I-i
(a) _---_-
-I ---I
G,H6(6.20)
6,24(6.95) 6,18(6.38)
5,95(G,57)
s
.
= di(2,4,6.trIchloro)phcnyb
798(768) 851(79(1)
422(438) 441(466)
1071(890)
1131(1092) 760(770)
758(742)
4GO(GOl) 484(488) blO(516)
410(44G) 488(502)
.
Mol,wt. found (cnlcd.)
p2,4,6+PT
.---
b3NW4)NR3)lz
D.3,6-C12PT = di(3,G~di~chloro)phcnyltrlnzcnIdo; DpTA = dl~p~tolylacctamidino.
55.48(5G.50) 46,10(46.82) 57.98(58,23) 59,56(69,7G) 56.76(57,39) 47.18(47,90) 68.00(58.95) GO.20(60.46) 54.86(55,66) G7.01(57.39) 64.76(64,99) 43.62(43,69) 37.38(37,42) 32,59(32.73) 55.77(66.10) 44.90(45.07) 38.60(38,79) 33.94(34,04) 27.02(27,40) 31.12(30.90) 57.61(58,3S) 88.91(69.38) 58.75(59.38) 69.96(00.30)
._._-..-
C
Analysis found (wlcd,)
_-_
[(t13~RC311,+)Pd {It”N3R3)l~ AND W?4WLW
___“___,,“--_-I.v--
{R’NS(RZ)NR’}l,
S.t.Bu~N,N’~l.~.tolyI(NSN)}l S~t~Bu~N,N’~i~(4~Cl~pI~e~~yl)(NSN)}l ‘Jbt-Bu.N,N ‘&3,6-xylyl(NSN)}l ~~~L-Bu-N,N’~l~2,4,6~mesltyl(NSN)}l ‘:S.t.Bu-N,N’~ip.tolyl(NSN)}l .~~t.Bu-N,N’~i(4-Cl.ph~~yl)(NSN)}l +Bu-N,N’&3,5-xylyl(NSN)}l +Bu-N,N’111~2,4,&medtyl(NSN)}1 .Me.N,N’dI-3,5~xylyl(NSN)}I -Me-N,N ‘~1.2,4,6-mcsityl(NSN)}l
_ -......--_---
DATA FOR [(+Rc3ki4)Pd
t(q3-C&)Pd(DpTT)I2 [(t13-C$IS)Pd(DpCIPT)12 [(~3-C3115)Pd(D.3,G.C12PT)]~ [(~3-C311S)Pd(D.2,4,6.C13PT)]*
[(q3-C&)Pd [(q3-C$I#d [(q3-C$IS)Pd [(q3.C3Bs)Pd [(q3-Qti7)I’d [(q3-C&)Pd
Compound ’
--__l-.._l._-__---
ANALYTICAL
TABLE 1
289
R
Fig.2. PossibIeisomersof
L(~~~-RC~H,)P~{R'NS
)I-
{MesNS(t-Bu)NMes )]. In this case the isomers do not interchange at 35°C. The similarity with the rhodium compounds is also demonstrated by the decomposition which generally takes place in solution at ambient temperatures and which leads to azocuenes. The palladium compounds offer the additional advantage that the decomposition can be more fully studied, as the SR- group can be captured in the form of f(q3-RC3Hq)Pd(SR2)la, which contains a bridging mercapto group. This was confirmed by comparing the NMR data of the decomposition products with those of a mixture of azoarenes and [ (77’-RC3H4)Pd(SR2)12. The mechanisms of the decomposition are discussed below. Of interest is that, in contrast to the compound [(CO),Rh{MesNS(t-Bu)NMes}], the mesityl groups of the corresponding (methyl)allylpalladium compound can freely rotate (Table 2) above +lO”C. This agrees with the observation that the rhodium compound mentioned above, in which the mesityl groups do not rotate, is stable to decomposition into azo-arene, while the palladium compounds are not. The rate of decomposition showed the following orders: S-Me > S-t-Bu and p-to1 > p-Cl&H4 > 3,5-xylyl > 2,4,6-mesityl. Owing to rapid decomposition the S-Me-N,N’-ditolyl- and the S-Me-N,N’-di@-ClC,H,)-sulfurdiimino derivatives could not be isolated_ Triazenido- and amidino-(methyl)allylpalladium compounds The complexes, some of which are already known [17,18,30] by two new methods: [(n3-RC3H4)PdC1]2 + BAg(DMT) + [(q3-RC,H,)Pd(DMT)]z
were obtained
+ 2AgCl
(2)
[(q3-R&H4)PdCl]2 + 2DpTTH + BKO-t-Bu --f [(q3-RC,H,)Pd(DpTT)]2
+ 2KCl+
BHO-t-Bu
(3)
On the basis of molecular weights (Table l), crystal structures of [ (q3-C4H7)Pd(MeNsMe)lZ [9] and of [(q’-C3HS)Pd {p-MeC6H4N3C6H4@-Me) )I2 [ 261 and of
IR data (v,,(NNN) - 1350-1375 cm-‘, characteristic for a bridging triazenido group 171) (Table 4), it was -oneluded that all compounds are dimeric and have
bridging triazenido or amidino groups. It has already been pointed out [17,18, 301 that three isomers are possible, in principle, in the case of the ally1 compounds (Fig. 3), depending on the orientation of the ally1 group. Two of these have been observed up till now [17,18,30]. The third isomer was also found, and occurs in all our compounds except for [(q3-C3HS)Pd{ (2,4,6-Cl&H2)Ns(2,4,6-C13GH*) 112,which exists in solution in only one isomeric form. In the
IH NEAR DATA FOR rel. to TMS) n.o.=not
L&-Rc3H4)Pd{~'~~(~2)~R')3 AND L(n3-RC3H4)Pd(sRZ)lt observcd:d =doublet.m = multiPIet Solvent
Compound
L<&C3Hs)Pd{S-t-Bu-.V..V'di-.+tolYl(NSN)}l L
C7D8 C7D8 CGD6 C6D6 C6D6 C6D6 C7DS C7Ds C7Ds C6D6 C7Ds C7Ds C7D8 C6D6 C7D8 C7D8 C7D8 C6D6 C6D6 C7D8 C7D8 C7D8
+30 -l-30 0 -60 -60 +30 +30 +30 +30 0 -60 -60 130 0 -60 -60 +30 0 -60 --6O c30 i-30 +10 +10 -0
C7D8
-60
C6D6 C6D6 C7Ds
[(q3-CqH7)Pd{S-t-Bu-X.N'-di-2.4.6-mesityl(NSN))l
[(+C3H5)Pd{S-Me-i\i.N'-di-2.4.6~mesitYl(NSN))l L
T ("0
C6D6 C6D6 C6D6 C6D6
+30 +30 +30 t30
ISOmer
(chemicaishifts inppm
Resonancesofthe ~YigrOUP anti
SYR
Ii I II I II I
3.33 3.17(d) 3.20(d) 3.19(d) 3.03(d) 3.43(d) 2.62(d) 2.85(d) 3-27 3.28 3.29 3.20 3.16 3.18 3.11 3.03 3.33 3.36 3.36 3.32 2.48 2.68 2.45 2.69 2.57
2.13(d) 2.12(d) no. 1.70(d) 2.22(d) 2.20(d) 2.17(d) 1.88(d) 2.17 n-o. 1.90 2.42 2.03 n-o. 1.73 2.29 2.10 2.15 1.88 n-o. 2.13 1.85 2.13 1.83 n-0.
II
2.61
1.73
2.23(d) 3.75(d) 3.61 3.37
2.03(d) 2.57(d) 2.54 2.33
I II
I Ii
I
II
I II
I
case of the methallylpalladium compounds only one isomer (I) is possible for steric reasons (Table 5). In contrast to the monomeric sulfurdiimino compounds the dimeric triazenido compounds are very stable in solution and they strongly resist bridge fcontinued OR p_ 293)
1
Fig.3.PossibleiSomenof
II L(~3-C3Hs)Pd{R3NNNR3)lz
m and C
291
H.Me
Resonances of the sulfurdiimina ligands s-tble(aryl) ArYl Bl.l.Me
n.on-o. n-o. n.o. n.o. n.o. n-0. 1.63 1.74 1.69 1.90 1.53 1.49 1.58 1.73 1.68 1.77 1.70 1.88 1.4i 1.73 1.47 1.76 1.30
1.20 1.05 1.02 0.94 0.97 1.26 0.93 0.87 1.21 1.20 1.12 1.18 1.10 1.02 0.96 0.99 1.27 1.25 1.21 1.26 0.93 0.87 0.91 0.86 0.84
1.61
0.77
6.78;(n.o.)
4.73m 4.60111 1.58 1.63
3.34 1.47 1.51 2.50
6.60
ILO.
6.93 7.07.6.62 7.075.64 7.16;6.56
2.18
6.72l6.37 6.80
2.20
6.97 6.97~6.85 7.03x6.84
2.77c2.18 2.20 2.19 2.26
7.11:6.67 7.08r6.63 7.16~6.56 6.68~6.53 6.66;6.34 6.75~6.45 6.80
2.22 2.21 2.33 2.26 2.78;2.18
6.82
2.78:2.17
6.835.73
2.69;2.19 2.16 2.54:3.08 2.16 2.33:2.01
TABLE3 INFRAREDDATA(KBrdisk)
FOR [(q3-RC3fi4)Pd{~'~S(RZ)NR'}]
Compound
v(NSN)" 1237 1242 1245 1218
a Frequencies characteristic for this group.
~Ncm-1
891 897 890 853
292 TABLE
4
INFRARED IN cm-I Compound
DATA
(KBr
disk)
FOR
[(n3-RC3H4)Pd
a
v(triazenIdo.amidIno) 1357(v&: 1366(v,): 1363(u,): 1357(Ua& 1366(V,s); 1363(pa,): 136O(vas); 1572
t(03-CsHs)Pd(DMT)]+ t(s3-C311g)Pd(DpTT)17 C(n3-C3Hs)Pd(DpCIPT)J2 I(r13-C~II,JPd(DMT)12 t(n3-GtH7)Pd(DpTT)Jt E(s3-C4H7)Pd(DpClPT)l* C(~3-C4H,)Pd(D-2,4,6-C13PT)IZ C(n3-C3Hg)PdWpTF)Jz t<123-C311SJPd(DpT-~)]2 C(n3-C4H7)Pd(DpTF)32 C(s3-GzII,)Pd(DpTA)IZ = See note a of Table T-ABLE
{R3N3R3)37
1. b A tentative
assignment
AND
C(n3-RC3Ii4)Pd
b
{R3NC(R4)NR5}]7
6(NNN) 630 600 593 631 620 609
1338: 1189Ws) 1322: 1206(vs) 1323: lZOl(vs) 1337: 119O(vs) 1317; lZlO(Vs) 1317: 1205(vs) 1329; 1212(vs) 135O(vs) 1255Ws) 1349(Q) 1254(vs)
is given of the bending
b
vibration_
5
lII NLIR DATA FOR C(q3-RCaH4)Pd(R3NaR3)l 12 AND L(n3-RC3H4)Pd {R3NC(R4)NR3}l (ii ppm rel. to TMS) no. = not observed; d = doublet: t = triplet; q = quartet Compound
a
lsomer
Resonances
QVZ-H
anti-H
H.CHJ
2.52(d) 2.40(d) 2.79(d) 2.66(d) 2.76(d) 2.66(d) 2.96(d) 2.96(d) 2.80(d) 2.69(d) 295(d) 2.95(d) 2.90(d) 2.80(d) 3.12(d) 2.95(d) 3.08(d) 2.79(d) 2.71(d) 2.89(d)
3.50(d) 3.38(d) 3.62(d) 3.55(d) 3.66(d) 3.60(d) 3.70(d) no _ 3.74(d) 3.65(d) 3.80(d) n-o. 3.92(d) 3.84(d) 3.97(d) no. 3.73(d) 3.56(d) 3.49(d) 3.66(d)
5.37(m) 4.74(m) 5.49(m) 4.84(m) 5.85(m) 5.00(m) 5.85(m)
I II III I II
I(q3-C3tIs?Pd(DpTT)Ja
III I II
[(n3-C5Iis)Pd(D-3.5ClgPT)12
III I II
[(n3-C3Hs)Pd(D-2.4.6-CI3PT)Jz [(n3-C3H5)Pd(DpTF)Iz
III I I iI III I II
[(rj3-C3Hg)Pd(DpTA]12
III L(n3-C4H7)Pd(D~T)Jz [(n3-C4H,)Pd(DpTT)], [(~3_C4H7)Pd(DpCIPT)]2 [(q3-C4H7)Pd(D-3S-CI$‘T)]2
[<~3-C4H1)Pd
of the ally1
group
2.83(d) 2.69(d) 2.34(d) 2.60(d) 2.25(d) 3.33 3.49 3.56 3.66 3.40 3.33 2.88
1. ’ Not aII frequencies
f:&(d) 2.92(d) 3.38(d) 3.31 (d) 2.34 2.75 2.79 2.81 3.23 2.63 2.49
could be assigned
IN CDC13
Resonances of the trkxrenido(amidino) Iigands Aryl
b
CII3(arYI)
H.CH3
3.35 3.30(q) 3.58(q) 3.50 6_9(d):7_3(d)
= 2.27
ILO.
5.75(m) 5.10(m) 5.75(m) n-0 _ 5.80(m) 5.10(m) 5.80(m)
l.l
n.0.
7_00(t):7_33(d) 6.96(t);7.28(d) 7_03(t);7_42(d) 7.OO(t):7.38(d) 7.24 6.96 6.89 7.03 7.00
5.15(m)
6-7
2.13 2.27 2.24 2.37 1.93 2.28 1.78
6.96(d):7.41(d) ?.ll(d):7_39(d) 7.OO(t);7.4O(d) 7.20 6.93 6.57(d);6.85(d)
ll.0.
5.30(m) 5.35(m) 4.70(m) 5.35(m)
because
’
7.84 2.28 7-77 7.69 2.27 2.28 2.31 2.25
=
1.66
3.40
of overkp.
c 4 AA’XX’
2.27
2.26 2.27
7.78 1.68
patterns
293
breaking by most ligands. Within the NMR time scale there is no fluxional behaviour of the (methyl)allyl groups for both the triazenido * and amidino ** compounds between -50 to +115OC as indicated by ‘H and i3C NMR measurments. The triazenido and amidino groups can be replaced in chloroform by other more acidic triazenes or amidines. The order of ease of replacement is: Di-ptolylacetamidine < dimethyltriazene < di-p-tolylformamidine < di-p-tolyltriazene < di-p-Cl-phenyltriazene. Discussion Comparison of the S,N,N’-substituted sulfurdiimino compounds of rhodium(1) and palladium(H), in which the ligand acts as a chelate, shows that there is a close structural relationship. Because of the presence of the (methyl)allyl group in the case of palladium(I1) two isomers are possible in principle (Fig. 2), and are indeed observed. Except in the case of [(q3-RC3H4)Pd {MesNS(t-Bu)Mes )] these isomers interconvert at room temperature in the NMR time-scale_ There is also a strong chemical relationship between the palladium and rhodium compounds_ In both cases the decomposition of the compounds of rhodium(I) and palladium(I1) proceeds similarly. The palladium compounds decompose more rapidly than the rhodium compounds at +35”C. The order of decomposition rates is, in the case of palladium(H): S-Me > S-t-Bu and R’ = p-tolyl > p-Cl-phenyl > 2,4,6-mesityl, which corresponds well with that found for rhodium. The decomposition reaction involves the formation of azoaLenes and SR-, but only in the case of palladium(I1) could the formation of SR- be demonstrated conclusively, by isolation of [(q3-RC3H4)Pd(SR2)]z. On the basis of the electronic and steric influences on the decomposition rates the following mechanism is proposed (Fig. 4). The first step is probably an attack of the metal atom on the sulfur atom via a n-allylic intermediate, which agrees with the observed steric influences. In the case of R’ = 2,4,6-mesityl the formation of a a-allylic intermediate or a direct intramolecular attack of the metal atom on the sulfur atom is strongly hindered by the two ortho-methyl groups which point between the metal atom and the sulfur atom (see crystal structure of [(C0)2Rh{MesNS(t-Bu)NMes}] [15,16]). The steric hindrance can be diminished, if the mesityl groups can rotate, which is the case when S-t-Bu is replaced by S-Me. Consequently the rate of decomposition is much higher in the case of the S-Me substituted compound than in the case of the S-t-Bu compounds. We can also now understand why the p-tolyland p-Cl-phenyl substituted compounds decompose more rapidly than the 2,4,6mesityl derivatives_ The rate increasing effect of electrondonating R’ groups on the azo formation i.e. ringclosure of the S,iV,N’-moiety becomes clear from a comparison
* In accord with previous findings [17.30]. ** Flu-xional bebavioux was proposed previously that the reported merging of the appropriate of the chemical shifts without broadening_
[18] on the basis of ‘II spectra only. We conclude signals is due only to temperature dependent changes
294
R
iv ’ .,
_____w-
LR
d
J
-6
‘N=
4
2
N,
Fig_ 4. Proposed
R’ mechanism
for
the
formation
of azo-arenes
and C:~3-RC~H4)Pd
with O=S=O_ The O-S-O angle decreases and the S-O bond length increases with increasing negative charge, since extra electronic charge will go into an orbital with S-O antibonding and O-O bonding character [ 271. Comparison of the S,N,N’-sulfurdiimino group with the triazenido or amidino group bonded to palladium(I1) shows that the first ligand prefers to be bonded as a chelate, whereas the last two ligands are bridging *. It should be noted here that the azenido group may bond as a chelate, a bridging ligand or as a monodentate [28], while the S,N,N’-sulfurdiimino has only been observed, up till now, to occur as a bridging ligand or as a chelate. The absence of the monodentate form is probably due to the fast decomposition into azo compounds. The general occurrence of three isomers in the case of the q3-allyl-triazenidoand arnidino-palladium compounds agrees well with the expected possibilities (Fig. 3). The presence of only isomer I in the case of [(q3-C3K,)Pd{2,4,6-C13CsH,)N,(2,4,6-Cl,C,I-I,) ]] is probably due to the fact that, in the isomers II and III, there is steric interaction of the ally1 moieties with the ortho-Cl atoms. Steric interactions are also probably the reason why, in the case of the methally1 compounds, only isomer I was observed. Finally we wish to note that the vas(NNN) in the IR spectra was found in the region of 1350-1375 cm-’ **, which is an additional support for our assignment in previous papers of bridging triazenido groups [6,7]. Acknowledgement We thank Mr. D. Prins for the analysis and Dr. A. Oskam for valuable help and discussions. The investigations were supported by the Netherlands * It
should be noted that a chelate azenido is not the use for the S.h’,N’-suIfurdiimio
group liesin a PIam? with the metal atom c28.291. This grouP which is more n-all~licin its mode of bonding
C161. ** These data differ from those of others I17.181.
295
Foundation for Chemical Research (SON) with financial aid from the Netherlands Organization for the Advancement of Pure Reseach (ZWO). References 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30
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(1976)
J. Kuyper. L.G. Hubert-Pfalzgraf. P.C. Keijzer and K. Vrieze, J. Organometal. J_ Kuyper and K. Vrieze. J. Chem. Sot. Chem. Commun.. (19i6) 64.
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