Activation of carbon disulphide by transition metal complexes

Journd of Orgnnometallic Chemistry, 66 (1974) 161-194 @ ELwier Sequoia S-A., Lausanne - Printed in The Netherlands ._

Review

-, --

ACTIVATION COMPLEXES

OF CARBON DISULPHIDE BY TRANSiTIoN

IS. BUTLER and A.E. FENSTER

METAL.

*

Department of Chemistry, McGill University, P-0. Box 6070. kc&real

101; Quebec [Canada)

(Received June 29th, 1973)

Contents I. Introduction II. Carbon disulphide complexes A. rr-CSs complexes 1. PIatinum, paRadium and nickel 2. Vanadium 3. Iron and ruthenium 4. Rhodium and iridium B. S-Bonded complexes C. Complexes with brid_eingCSa groups D. CSa insertion complexes 1. Metal-hydrogen bonds 2. Metal-carbon bonds 3. Metal-nitrogen bonds 4. Metal-oxygen and~metal-sulphur bonds 5..Metal-halogen bonds III. Thiocarbonyls A. Group VIII metals 1. Iron 2. Ruthenium 3. Cobalt 4. Rhodium 5. Iridium B. hlanganese IV. Conclusion V. Infrared data for carbon disulphide a& thiocarbonyl compIexes References - : .’

162 162 162 I62 164 164 165 I68 169 169 170 172 1?3 173 174 174 175 175 176 177 177 -178 181 184: is5 193’

‘.-

‘.

:

‘_ :

:

-:

...

* Present address: Department of Chemistry, University of British Columbia, Vancouver 8, British. Columbia (Canada).

I. Introduction

In 193 1, Duncan et al. [l] reported that &bon disulphide reacts with copper mercap- :: tides (Cu-SR) to give trithiocarbonates (Cu-SSCSR). However, this initial discovery was ._ not followed up and the subject of activation

of carbon disulphide by transition metal

complexes lay dormant for over three decades. It came to light again in 1966 when Baird and Wilkinson [2] synthesized first thiocarbonyl rrrm~-RhX(CS)(Pph~)~

1

’

= Cl, from the of RhX(PPhs)s CSz. Since then, a number of metal I thiocarbonyls have been prepared by reactions in which CS, acts as the source, of the CS ligand in the formation of M-CS bonds. These reactions, however, represent only one as- .-’ pect of the activation the

of CS, by transition metal complexes.

past seven years indicate that CS, itself can coordinate

In fact, papers published over. to transition

metals to form

four distinctly different types of complexes. A review of the activation of carbon disulphide by transition metal complexes yet appeared in the literature

view an attempt has been made to summarize the known reactions metal complexes.

has not

despite the growing interest in this field. In the present re-

Since most of the new complexes

of CS2 with transition

formed have been identified

chiefly

by infrared spectroscopy, it was felt worthwhile to tabulate the pertinent infrared data immediately following the review. The literature coverage is considered to be complete to hiarch 1973.

II. Carbon disulphide complexes A. n-CS2 complexes The first examples of transition

metal complexes

tion” were the carbon disulphide complexes

to exhibit so-called “n-CS,

coordina-

of platinum and palladium. These complexes,

together with a related complex of nickel, will be discussed first; following this, the 7r--CS, complexes of vanadium, iron, ruthenium, rhodium and iridium will be described. The n-CS, complexes of manganese believed to be intermediates in the formation of ncyclopentadienylmangauese thiocarbonyl complexes will be considered later (see p. 182). 1. Platinum, palladium Qnd nickel

During their investigation

of potential methods for the synthesis of transition

thiocarbonyl complexes, Baird and Wilkinson CS, to form the stable adduct, Pt(PPh&(CS,). ture I for thiscomplex: sr-arylacetylene Pt(PPh&(CS,)

hloreover,

metal

[3] discovered that Pt(PPh,), reacts with They proposed the square-planar struc-

they noted the similarity of this structure

to that of the

complexes, Pt(PPh&(acetylene) [4]. In fact, they were able to obt&n by displacement of the phenylacetylene group in Pt(PPh&(PhC,H) by

CS2. The platinum carbon disulphide complex and its palladium analogue can also be prepared by treatment :.

of M(PPh& _.

(M = Pd, Pt) with CS,

.,..

[5,6].

..-

...

..

’

163

:

(I) The z-CS,

coordination

suggested for Pt(PPh&(CS,)

dimensional X-ray diffraction

of the complex

has been confirmed by three-

[S, 7] and of its palladium analogue 161.

The geometry of the CS, ligand is modified drastically upon coordination. Uncoordinated CS2 is linear with a C-S bond length of 1.554 A. The coordinated molecule is bent with S-C-S

bond angles of 136.2”

and 140” for the platinum and palladium complexes,

pectively; the mean C-S bond lengths are 1.626 A for Pt(PPh3)2(CSZ)

res-

and 1.64 A for its

palladium analogue. The geometry around the central metal atom in the two complexes is essentially similar. The metal atom and the four atoms coordinated

to it are almost CO-

planar in both cases. Triphenylstibine

displaces the CS, group from Pt(PPh&(.rr-CS2)

and its palladium

analogue to yield the tetracoordinated species, Pt(PPh3),(SbPh3), and Pd(PPh,),(SbPh3)2 [6]. However, with Diphos * the two triphenylphosphine groups in Pd(PPh&(5r-CS2) are substituted, resulting in the formation of a new n-C& complex, Pd(Diphos)(rr-CS*). Baird and Wilkinson [8] failed to obtain the nickel analogue of the platinum and palladium n-CS2 complexes. stoichiometry,

Reaction

Ni(PPh3)(CS,),

of Ni(CO)z(PPh3)2

with CSz affords a complex of

which has a much simpler X-ray powder pattern than those

for the palladium and platinum r-C&

complexes.

The nickel complex is dimeric in solu-

tion but could be polymeric when solid. The structure proposed for the dimer involves sulphur bridging between the two nickel atoms (II).

* Diphos = 1,2-bis (diphenyl$hosphino)ethane.

.: -.

-_

1$4 2.

.._-

V~j~*

.._:-: ’

‘..~

? Baird et al. (91 have reported that CS, reacts with the purple complex, CpzV (Cp-= T-~_C$-I.&,to give a green solutiorr. This solution is extremeIy air-sensitive but a 7i-CS, corn;-_; f pleX could be identified by :p&roscopic mea.&. In addition to bands due to the Cp moiety, there is a strong absorption in the IR spectrum at 114i

cm-l

_.A'similar band is

.I

also present in the spectra of the platinum and palladium+CS2 compIexcs. Consequently, the 1141 cm21 band ivas assigned as a C=S stretching frequency. The tetrahedral strut-

: ::

ture Ii1 is supported by the ESR spectrum of the green. solution which indicates the pre&ence of vanadium(N).

.:

..

.-

‘_

3.

Iron and ruthenium

The iron complex, Fe(CO)a(PPh:,)2(a-CS2), has been prepared by the reaction of. Fe2(CO)9 and CS, in the presence of PPh, [9] _A more stable complex is obtained when P@-FC$& is used instead of PPh, ; a less stable one is produced when the reaction is

..

carried out in the presence of Plp-(MeO)C&4]3. The &is@-ffuorophenyl)phosphine complex undergoes phosphine exchange with excess of PPh, to give the triphenylphosphine complex. A hexacoordinated structure (IV) was proposed for the complexes.: I-

.L mn Busem

et al_[lOl

have postuJated that the intermediate,

formed during the synthesis of the iron t@oca@onyl

cation,

[CPF~(CO)~CS;]-, [CpFe(CC&CS]+(see_e

is p_ 1.~5).

I$ :.:. ~. -..c

. ._ :;i ::.<. _,

165 However, no-decision was made as to the nature of the CS2 coordination

The reaction of PPh, with RuCI~(PP~~)~

or RuCl,(PPh,),

m the complex.

in refluxing CS, solution

yields the ionic species, [RuC~(PP~~)~(~-CS~)] Cl; the bromo analogue has also been prepared [ 111. Structure V is suggested for these cationic species. _

(PI X =

Cl

or

Br

.. 4.

. Rhodium ahd iridium ‘* The reactions of CS;! with a variety of rhodium and iridium complexes have been in-

_, vestigated. Details of some of these reactions are given in Fig:la’. When RhCl(PPh& is treated with CS, a rather unstable complex analysing approximately as RhCl@‘Ph&(CS-&

is produced

two strong bands at 1510 and 1020 cm-l.

[8].

The IR spectrum of this complex exhibits

The latter band is roughly in the same region

as the v(C=S) frequency for Pt(PPh&(n-CS,) and Pd(PPh3)2(rr-CS,). Consequently, this frequency has been assigned to a n-bonded CS2 ligand. The presence of the 1510 cm-l band has been attributed to a CS2 molecule coordinated to the rhodium atom through one of its sulphur atoms (structure

VI).

* In 1963;Marko et ai. [ 121 reported the preparation of the fist cobalt carbony disulphide complex, allegedly Co4(CO)&S2. The complex.is formed in low yield from the reaction, oE.Co2(~O)a witi.. CS2..In a subsequknt publicatidti [ 131; the same autQors indicated that‘anisomer, of Fe ?l@e CS2 com$ex cddd be obtained by varying the Co2(CO&/CSz ratio. However, X-iajf.diffraction’studies .. have indicated-that the true compositions of the “isomers” are in fadt CO~(CO)&S~[SCO~(CO)~.] [14] and [SCO~(CO)~](SC)(S)[CC~~(C~)~~ [15], r$spectively. Details of.these. . studies haye not yet _ .. . been published.

Yagupslq

and Wilkinson [ 161 have prepared several cationic n-CS2 complexes

as their tetraphenylborate salts. For instance, reaction of RhCI(PPh,), presence of MeOH tid excess PPh, affords [Rh(PPhs)3(CS,)(n-CSz)J+. to contain (CS2)(sr-CS,).

S-bonded CS2 CS, group

similar to

readily lost

[Rh(PPh&(rr-CSi)]‘. of CS2 pans-RhCl(CO)(PPh& in produces a solution. Treatment this blue

with CS, in the This is be-

shown above

the complex

isolable

RhCl(PPh,),-

yield the

in the with sodium

cation,

of excess

results in rr4ns-RhCl(CS)(PPh3)2

of [Rh(CO)(PPh3)3(zr-CS,)IBPh4. The thiocarbonyl analogue, (see p. 177), al so reacts with CS, in the presence of MeOH and excess PPh, to give [Rh(CS)(PPh3),(CS2)(?r-CS2)]+ and A complex, as RhC1(CS)2(PPh2Et)z, be obtained the reaction the rhodium(II1). plex are

Addition

BhCl,H(PPh,Et),, wi’ih the VII.

SnCIZ in-ethanol

complex,.Bh(PPh&&r-CS&(SnCl$ is very

to that

a CSz ]16]; the rhodium

with

[17].

Infrared

for this

of RhCI(PPh3)~

PPh3 affords.the

of the dis&sed

iridium corn-.. above.

161 L Cationic

species are also produced in the presence of MeOH, PPhi.-arrd CS;‘ (Fig.. l(b)).

:

~khCI(PPh3)~ ’

(a) Y.Y..

[Rh(Pph,),(Cs,x=-CSz)I+

Rhc1(Pph3)2(C~2X=-=J)

d

C 1

n~ns-RhCI(&)(PPh3)2

(Rh(PPha)&--C&)1*

inxns-F3KI(CO)(PPh,)2

rn?ns-RhCl(CS)(PPhs )1 b

b I [Rh(COMPPha)&-CS,)I+

1

T

(Rh(CSXPPh~)2(CS~Xa-CS2)1

1 d

[Rh(CS)(PPh&(+CS2)1’

[Ir(CO)(PPhs)j(ir--CSz )] +

IrX(CO)(PPh&(n-C.Sz)

Fig. 1. Typical reactions of rhodium and iridium complexes with CS2 [S, 9,161. a, in CSa ; b, in CS2 and in the presence of PPha and MeOH; c, in CHC13 followed by addition of MeOH; d, in vacua; e, upon heating in CHCl,; f, in CS2 and in the presence of PPh3 and CHC13; g, in CS2 and CH2C12.

The reaction of ~~L~K+I~CI(CO)(PP~~)~ with CS, produces a mixture of unreacted starting material and the new complex, separate the two complexes

IrCl(CO)(PPh,),(%C!Q

is used instead, the pure complex, IrI(CO)(PPh3),(?r-CS,), spectrum in CS2 solution exhibits two bands m the ~43~

-l . Consequently, :%I)

whichdiffer

]8]. All attempts

to

failed. However, when the iodo analogue, rr~izs-IrI(CO)(PPh3)2, can be isolated. Its infrared region at 1188 m.&nd 1165 s

it was proposed that the complex is in fact a mixnrre of two isomers __ ‘. in the orientation of the n-bonded C& group.

PPh,

Deeming and Shaw [ 181 have isolated the analogous dimethylphenylphosphine complex, IrCl(CO)(PPhMe2)2(7r-CS2)~ The NMR specrrum of the complex consists of two 1/2/l triplets..How&r, because two triplets would be expected for each of the two possible n-C& isomers, it was suggested that only one isomer is presented in solution. This may also be true for the solid state as there is only one Ir-CI stretch observed (at 252 cm-l). A dimeric chlorine-bridged structure containing two A&. groups has been proposed for the complex ofstoichiometry between the 1,5-cyclooctadiene

B. S-Bonded complexes

IrCI(CsH12)(CSZ), which is the product of the reaction complex, [IrCI(CSH1$ J2, and CSz [9] _ .

There are only a few complexes in which a CS, molecule is believed to be bonded to a transition metal solely through a sulphtir atom. Some of these for rhodium and iridium have already been described in the previous section since they also contain r-bonded CS, groups. Purely on the basis of IR data in the CO stretching region, a complex with structure IX allegedly results from the reaction of Fe,(CO)9 with CS, [?I.

co

_. _-----*=.y$--q*

c I

‘.,:

I

..,' Y.-& :., t \

-scs

...

169

:

of Pt(Me)I(PPh&

with CS, [ 1’71. The stiong band in the spectrum at 1520 cm-l was taken to be indicative of an S-bonded CS, m&m.&. The e&se of CS2 dissociation from the

complex supports this suggestion. ._ C. Complexes with briaging CS, groups The complex,

..

Kg [(CN),CoCS,Co(CN),]

has been obtained independently

et al. [ 191 and by IBaird et al. [9] from the reaction of I$ [C~(CN)~]with

by Mizuta

CS,. The two

research groups differ in their ideas on the propose-d mode of CS; bridging in the complex. The Japanese chemists prefer a structure (X) in which there are two Co-S bridges, while the British group consider that the CS, molecule is‘C-bonded to one Co atom and S-bonded to the other (XI)_ 9 .I&, [(CN)&OS+-C+N)~]

I$, [(CN)$o-S=C=S-COG]

WI)

(X)

with CS2 leads to green solutions from which complexes Direct reaction of IrCl(PPh,), of stoichiometry, IrCI(PPh&(C!Q, (x ? 2-3, y = l-3), can be obtained [ 16]_ The actual composition of the complexes depends critically on the experimental conditions employed. Owing to their instability, the exact nature of these compounds has not been determined. However, from IR data alone; .it was suggested that IrCl(PPh,),(CS,) and IrC1(PPh3)2(CS2)3 might be dimeric with bridging CS2 groups and that in the latter an S-bonded CS, group might also be present. A special case of CS, bridging results from the reaction of the anions, (1, 2-BgC2H, 1)2MY (M = Fe, Co) with CS, in the presence of AlCl, and HCl. .Zwitterionic species are formed which have an -SCH*-S bridge between the two n-bonded.dicarbollide ligands of the complex

1201.

D. CS2 insertion complexes Althoughinsertion known

reactions between main group metal complexes

for some time [21],

reactions with transition metal cornpIeties. Potentially, into G M-X

and CS2 have been

very little work had been reported until recently .on similar the insertion of a CS, molecule.

bond (M = transition metal, X = H, alkyl, aryl, amine, alkoxide, etc.) could

lead to a variety of known or new dithio compounds:

: .A

_

.

.

..:

..

.. ,

M-X

C

-MY---

CS,

&fetal-hydrogen. bonds Recently, Chmereuc et al. [ 171 have reported that CS, inserts into metal-hydrogen bonds of d8 rhodium, iridium, and platinum complexes. For example, reaction of with CS, lezids to the formation of a compound of stoichiometry, =WCO)(PPh3)3 [Rh(CO)(PPh&(C&)]$L The low solubility of this compound in organic solvents precluded a moIecuIar weight determination. In its IR spectrum there is no Rh-H absorp tion but there is a strong band at 993 cm-l which was assigned to a T&S, group. The absence of the metal hydride group in-the compIex was also confirmed by protdn NMR spectroscopy. Structure XII was suggested for the complex; it can be arrived at by coupling together two molecules of the insertion product, RIJ(CO)(PP~~)~(~-CS,)(CSSH), wit.IreIimination of H,S.

co am) -.

:.

:

171

The CS, insertion reactions of iridium hydrides such as IrH(CO)(PPh& have been moriiioied by NMR spectroscopy 1171. In this case, the following reaction scheme was proposed: IrH(CO)(PPh&

+ CSz --t PPh3 + IrH(CO)(PPh,),(lr-CS,) -1 H- transfer Ir(CO)(PPh&(CSSH)

The lack of documentation on the chemical shift of the SH proton precluded a distinction between a -CSSH or -SSCH type of bonding in the insertion product. The reaction of IrH(CO),(PPh,), with CS2 yields a solid which analyses as Ir(CO)(PPh&CS,), [173. Infrared data point to an increase of the oxidation state of the iridium atom and to the presence of a a-C!$group. Although the two formulations compatible with an lrul complex containing two CS, molecules are Ir(CO)(PPh&(n-CS2)(CSSH) no NMR signal attributable to -CSSH or -SSCH proand Ir(CO)(PPh&(+CS$(SSCH), tons was observed_ Interaction of CS, with the n-cyclopentadienyl hydride complexes, Cp,WH? and Cp;?ReH, has also been studied but no definite products were obtained [ 171. Pallazzi et al. 1221 have obtained the insertion products, PtX(PPh,),(SSCH) (X = Cl, Br, I, CN), from the reactions of frans-PtXH(PPh,), with CS,. The chloro complex, PtCl(PPh&(SSCH), has two new bands in its IR spectrum at 1050 and 930 cm-* but no Pt-H absorption. Structure XIII is preferred for the -SSCH group.

I I

-PPt-S-C

2 Ll

This choice was made on the basis that the complex does not exhibit acidic properties. Moreover, treatment of the complex with KCN yields potassium dithioformate; KS2CH. Kinetic data.1221 seem to indicate that there are two steps in the formation of PtCl(PPh&(SSCH): (1) S-coordifiation of CS, to produce a labile species a&(2) intramoIecular hydrogen migration in a four-centre transitioti state to form the insertion product. Another complex prepared by CS, insertion into a metal-hydrogen bond for which X-ray data are.available is Re(CO)$PPh&(SSCH) [23]. This complex, which is prepared [24] by refluxing a CS, solution of ReH(C0)2(PPh3)2, contaifis a chelated-dithioformdto group. Although the presence of a hydrogen atdm associated with the CS2 group could not be detected by, X-ray diffraction, $ectroscopic data indicatk that the original hydride-. ligand has been transferred to the carbon atom of the‘ CS2 entity. Moreovei, although it

was Aot mentioned in’the above work, the bonding parameters for: the four-membereii : &elate-ring in Re(CO)z(PPhj)i(SSCH) are essentiatly sir&ar to those observed for Re(CO)4(SSCPh) which is aIso obtained by a CS, insertion process (see beltiw). The results for Re(C0)2(PPhs)2(SSCI!I) led AIbano et al. [23] to suggest that the related iridium complex, ‘Ir(CO)(PPh&(CSSII), described earlier must also contain a chelated . . dithioformato group. Einstein et al. 1251 have shotin that CS, will insert at room temperature into the M-H bonds of&-Mn(CO)s(Diphos) H and fac-Mn(C0)3(P%PCH2PPh2) H (M = Mn, Re) to form M(C0)3(Diphos)(SSCH) and M(CO),(PhiPCH,PPh,)(SSCH), respectively. The molecular arrangement of the M(SSCH) moiety was coilfirmed by stigle crystal X-ray diffraction.of the manganese bis(diphenylphosphino)methane complex. The four complexes are of particular interest because they are among the fust for which laser Rarnan data have been’ obtained_ The v(CS) modes are of relatively high intensity and fall in the region 999-649 cm-l. 2. Metal-carbon bonds Complexes ofthe type, M(C0)4(SSCR) (M = Mn, Re; R = Ph, CF3), have been prepared by treatment of the appropriate free dithioacid with M(CO),R [26,27]; An alternative synthetic route to Re(CO)4(SSCPh) and a variety of new dithiocarboxylato complexes of manganese and rhenium has been reported by Lindner et al. [28-301. The reactions invofve direct CS, insertion into metal-carbon bonds. M(CO),R

+ CS,

3-S days. so-150”

M(CO)&SSCR)

+ CO

(M = Mn, R = Me, Ph, p-MeC,H,; M = Re, R = Me, Ph, p-MeC6H4, p-ClC,H,,

PhCH,, Ph, C)

An X-ray diffraction study of Re(CO)4(SSCPh) indicates that the dithio group acts as bidentate Iigand and the coordination around the central met+ is pseudo-octahedral [3 1J. The vibrational spectra of the manganese and rhenium complexes are in agreement with the observed pseudc+, molecular symmetry [28,.30]. L&rdner et al. (301 have noted.that the trend towards CS, insertion into the &l(CO)SR complexes is the same as that observed for the “CO insertion” reactions df.the pentacarbonyImanganese(I) complexes, M~I(CO)~R, viz., the reaction is more facile with an aromatic than with an aliphatic derivative. The rhenium dithiocarboxylates a&more stable than their manganese an$ogues. The.dithiobenzoato derivative, Re(CO)&SSCPh), undergoes CO substitution by PPhs to,give the tricarbonyl .derivative, fac-Re(CO)3-PPhs(SSCPh).. During the course. of their work on the’CS2 insertion reactions of a variety of tmnsi_ ?ion metal complexes,. Comrnereuc,et .al. (I 7] prepared a compIex.of stoichiometry, RhI,(Me)(CS,)(PPh&.= CcH6, from-the reaction of Rh12(Me)(PPh&= C,H, with CS,.: It was suggested that the complex contains a dithiomethy1 ester group -CSSMe. However, .

in view of the CS, insertion reactions described earlier, it seems much more.likely.that -’ the MeCS, in this complex is S-bonded and chelated to the rhodium atom. Moreover,

such a structure is in accord with the tendency of Rh*” to become hexacoordinated.. A complex of stoichiometry, Rh(Ph)(PPh3)3(CS2)2, has been isolated from the reaction of Rh(Ph)(PPh& with CSi [ 171; a-structure comaining both a a-B2 and a dithiophenyl ester group was proposed. However, the dithiobenzoato complexes, M(C0)4-. (SSCPh) (M = Mn, Re), exhibit an IR band at 1267 cm-l which is very close to that assigned to a dithiophenyl ester group at 1261 cm-l: Consequently, it seems much more likely that the PhCSS group in the rhodium complex is S- rather than C-bonded. 3. Metal-nitrogen bonds Vetter et al. [32,33] have prepared N, N-dialkyldithiocarbamates of phosphorus and arsenic by the insertion of CS, into P-N and As-N bonds. This method has been extended to the early transition metals by Bradley et al_ [34,71]. In particular, complexes of TiTv, VW, and Zrn’ give the hitherto unknown tetrakis (N, N-dialkyldithiocarbamato) complexes: M(NR.& -I-4CS2 -

M(SSCNR,), (M = Ti, Zr, R = Me, Et, n-Pr; M = V, R = Me, Et)

In the case .of pent&is (N, N-dimethylamido) derivatives of niobium and tantalum, different products are obtained. . Nb(NMe&

+ 5CS2 -

Ta(NMe&

+ 5CSz -

Nb(SSCNMe& Ta(SSCNMe,),

+ 1/2(Me2NCS,),

McCormick and Kaplan [35] have.synthesized a series of dithiocarbamates of Nil1 by the direct insertion of CS, into Ni-N bonds of a variety of amine complexes, e.g. [Ni(En)3]C12 and [Ni(Amp)3]C12 *. Carbon disulphide also gives insertion products with [tetraaziridinenickel] 2* and [ tetrakis(2-methylaziridine)nickel] 2+ [36]. Infrared data suggest that the resulting cornplexes contain N, S- rather than the expected S, S-bonded ligands. 4. Metal-oxygen

and metal-m&h& borzds Insertion of CS, into metal-oxygen and metal-sulphur bonds in alkoxides and mercaptides leads to the formation of metal xanthates and metal trithiocarbonates, respectively

*

En =

N

e’khylenediamine

; Amp== H$lCH2

43

174.-‘--. ._.

:.

e.g.-with Ni(OMe)2,

& ..

nickel methylxanthate.

[~i(SSCOMe)2]

is formed 1371.

early as-1931, it was known that co@er merc@tides ieact.with CSa to &e Cur

aIkj&rithio&rbonates-

[ 11. More~recentIy, it has been shown-that

the trithiocarbonates

of

n-~oIybc&mm and tungsten,.CpM(C0)2(SSCSR) (M = MO, W; R = Me; Ph), can be obtained in a s_imilar_Wayfrom CpM(C0)3SR or [CpM(CO)$R] 2 1381. Also, spectroscopic evi- -

dence indicates that the corresponding nickel complexes, [CpNiSR] 2 (R = Me, Et), undergo CS2 insertion to give the unstable species, CpNi(SSCSR) 1391: . Whjle investigating the reactions of Pt(PPh&O, with various unsaturated molecules, Hayward et al.. [40] discovered that this complex and its pahadium anaIogue react with CSz to give the known dithiocarbonates, Pt(PPh3)2(SSCO) and Pd(PPh&(SSCO), respectively. 5. Metar-halogen bonds There is only one example of CSz inserting into a metal-halogen bond viz., the formation of [Pt(PPh&(SSCF)]HF2 from the reaction of [PtF(PPh&]HF, with CS, [41]. The crystal

structure of this complex displays pseudo-square-planar coordination around the metal with the FCSS group bonded through the two suIphur atoms.

III. Thiocarbonyls The first examples of transition metal thiocarbonyl complexes, trans-&X(CS)(PPh3)z and RhX~(CS)(PPI& (X = Cl, Br), were synthesized by Baird and Wiikinson [2] in 1966. Since then, relatively few thiocarbonyl complexes have been prepared and even these have been restricted to certain Group VIII metaIs and manganese. Furthermore, in sharp contrast to metal carbonyls, only three metal thiocarbonyIs containing more than one CS group attached to a central metal have so far been identified. The discovery of the first transition metal thiocarbonyls

prompted Richards [42] to

undertake a molecular orbital calculation for the CS molecule. The ground state ebctronic configurations for the CO and CS molecules are: CO, (1 o)~ (20)~ (30)~ (440)~ (50)~ (1~)~

;

CS, (10)~ (2oj* (3~)~ (40)~ (Ifl)4 (5~)~ (So)* (7~); (2~)~. The caIcuIation indicated that while the 70 and 277 orbit&

are almost degenerate the 70 orbital is localized largely on the

carbon atom and the 27r is a bonding orbital distributed on both the carbon and the sulphur atoms. The two electrons in the 7o‘orbitaI constitute a lone pair which can be used to bond the CS group to a metal in a thlocarbonyl complex. This situation is similar to that for CO in metal carbonyls in which the 50 lone pair is used. Moreover, the pair of electrons in the 70 orbital of CS should be more readiIy available since the energy of this orbital is -0-4705 a-u. as compared to -0.5704 a-u. for the !$a CO orbital. Furthermore, there appears to be-a greater.po+GIity of backbonding in thiocarbonyIs than in carbonyls. The energy of the empty 3~ antibonding orbital on CS is i-O.0848 a.u. which is significantly layer than the energy +O. 1507 au. of the equivalent 2n antibonding orbital .on CO. The_above conclusions were based 6n &culation

of the wave function for- CS and CO

.

.

175

at their equilibrium internuclear distances. Richards repeated his calculations for three internuclear CS distances to see if there was any-significant change when the bond was stretched during complex formation. He found that while the energy of the 70 orbital decreases slightly with increasing interatomic distance, the. energy of the 3n orbital decreases somewhat more rapidly. In other words, the availability of the 70 electrons for a-bonding is affected only slightly by the increase in mteratomic distances expected during complex formation, whereas the empty 3n antibonding orbital becomes more readily available for backbonding. Richards felt that his analysis revealed that thiocarbonyls should be significantly more stable than their carbonyl counterparts because CS is favoured over CO both in terms of o and rr bonding. This conclusion appears to be contradicted by the present paucity of tbiocarbonyls. However, some fragmentary experimental data for the known thiocarbonyl complexes do suggest that CS is a better n-acceptor than CO and so should be more strongly bound to a transition metal than is CO. A. Group VII.. metals 1. Iron

The cationic iron thiocarbonyl from [CpFe(C0)2]- and CS,. [CpFe(CO)2]-

complex

[CpFe(CO),CS]*

CpFe(CO)$CSSMe)

[lo]

MeI,

CWWW2CS$

+ CS, -

has been synthesized

x

[CpFe(CO),CS]*Cl-

+ MeSH

Attempts to isolate the two proposed intermediates in this reaction were unsuccessful. However, the IR spectrum of the reaction mixture after addition of Me1 was consistent with the presence of a dithioester. was fust prepared [43] by the followIt should be mentioned that [CpFe(CO),CS]+ ing reaction sequence: [CpFe(C0)2]-

+ ClC(S)OR

w

CpFe(CO)$(S)OR (R = Me, Et)

*

[CpFe(CO),CS]‘Cl-

+ ROH

This represents the only example of the formation of an M-CS bond where CS2 does not act as the CS donor. Busetto et al. [44] have investigated the reactions of [CpFe(CO)2CS]’ with various nucleopbilic agents. Three different types of reactions were observed depending upon the nature of the nucleophile. In allthe reactions described above, the nucleophilic attack occurs at the CS group.

176 .

.’ _ Nj

:

.._

.:

:

.

CpFe(C012NCS

+

.i .

N2 ’

-.

-..

._

I‘ ._

NH2yNH;

CpFe(C0)2NCS

NY

+

‘+

H+

...

I RO-

@m?(Cb~,CS-j+ 7

-

NH2R

-

OR

.

CpFe(CO)&(S)NHR

NCOi

1.

cpFeKiO),C(S)

c . CpFe(CO&CN

NCS-

CPFe(CO),CN

+

+

+

H+

(R = iR=

Me, Me,

Et)

Et1

COS

CS,

Consequently, it was suggested that the electrophilic character of the thiocarbonyl carbon atom in [CpFe(C0)2CS]+ is significantly higher than that of the carbonyl carbon atoms. The 57Fe Mossbauer spectra of a variety of cationic complexes of the type [CpFe(CO)2LJ* (L = monodentate ligand_including CO and CS) have been investigated [45]. On the basis of isomer shifts, it was concluded that CS is a better rr-acceptor than is co. .

As mentioned earlier (see p. 169, the reaction of RuCl,(PPh,), or RuCl,(PPh,), with cS2 and excess PPh3 leads exciusively to the formation of the r&S2 complex, [RuC1(PPh3)3(n-CS2)JCl. However, in the absence of PI%,, the n-CS2 complex precipitates out of solution and concentration of the filtrate affords the dimer [RuC12(CS)(PPh&] 2_ On the basis of IR evidence, structure XIV (or a similar one with cis-CS groups) was proposed for the complex; for steric reasons the PFh, groups were considered to be mm .to each other. The bromo analbgue is also known.

I

l=Ph3

:. ‘_

I PPh3

.-

177

The reactions of the chloro complex with CO; Py. Bipy and o-Phen have been investi-gated [l l]*.

As expected,

the complex undergoes cleavage reactions typical of a halogen-

bridged species, e.g.:

P.Ph3

F;Ph,

The anionic ruthenium thiocarbonyl,

[RuC13(CS)(PPh3)2]-,

[RuC1#S)(PPh,),l 2 and Cl-, has been reported recently the only example of a tbiocarbonylmetallate. 3. Cobalt The evidence for a thiocarbonyl

complex

prepared from [46] _ This complex is as yet

of cobalt is by no means conclusive. Among

the numerous sulphur-containing products of the reaction of Co,(CO), with CS, is a complex of stoichiometry, Co,(CO)&S, (yield 1 .S%) [ 13]_ Its infrared spectrum exhibits one band at 1011 cm-r

and it was suggested that this could indicate a triply-bridged CS

group. The proposed structure consists of a triangle of three Co(CO),

units bonded to an

apical trivalent sulphur atom with CS group bridging on the other side of the cluster. 4. Rhodilrm It was mentioned earlier (p. 165) that RhCl(PPh,), unstable complex,

RhCl(PPh3)2(CS2)(rr-CS2)_

reacts with CS, to form the rather

D issolution of this complex in CHCl,,

fol-

lowed by addition of MeOH and subsequent removal of the solvent yields the thiocarbonyl, in 50% yield [9]. Among the side-products of the reaction are tiQWRhCi(CS)(Pph&, PPh,S and PPh,O.

That PPh$ is the snlphur-acceptor

was demonstrated

by repeating the

reaction in the presence of excess PPh, _ Addition of a l/ 1 mixture of MeOH and CS, ‘to RhCl(PPh&

and PPh3 leads to the formation of an emerald-green solution. The cationic

species, [Rh(PPh&(z-CS,)]

+, can be precipitated

from.this solution as its tetraphenyl-

borate salt. However, if CS, is removed from the solution before precipitation of the r&S2 complex, orange crystals of tram-RhCl(CS)(PPh,)2 are formed in almost quantitative yield_ The residual solution contains all the abstracted sulphur in the form of PPb,S. The molecular structure of trans-RhCl(CS)(PPh3)2 has been determined by de Boer et al. [47].

Although there is a slight distortion,

the structure contains the expected

* Py = pyridine, Bipy = bipyridine, oPhen = o-phenanthroline.

17g._- ..

_’ :

.:-3 .i.::,_-.

coordination’around the rhodium atom together with a nearly-line& thio- .. _. $ ligaml (L Rh-C-S; 177.2”). The Rh-C.distar?ce (1.787 A) in the coni$ex is.ap- '.$ -:!! pzciably shorter than that in the carbonyl dialogue, trans-RhCl(CO)(PPh& (1;86 a), .../. -.i suggesting a greater Rh-_C double bond character for the former. ‘i! The & &carbonyI undergoes-oxidaiive addition with Cl2 to give ihe grn deriva-.j< tive, I%hCl&CS>(PPh,?2 [2,9]. (The analogous bromo compounds have also been pre-. _j p&&d.) hi contrast to its carbonyl analogue, pans-RhCl(CS)(PPh& does not aid HCl. It was suggested that this could indicate a lowering of the non-bonding electron.density on ;: .-: the metal resulting from the better n-acceptor character of CS. Moreover, it has proved .experimentally impossible to replace the thiocarbonyl ligand in the complex by CO “I (1 atm, 25”) and the complex decomposes following attack by Me1 and HgCIZ _ These resuits were also explained in terms of the n-acidity of CS. Treatment of rrans-RhCl(CS)(PPh& with LiSCN gives the S-bonded thiocyanato cornplex, tratrs-Rh(CS)(SCN)(PPh3j2 [9]_ The thiocarbonyl complex also reacts easily with tetracyanoethylene (TCNE) to give RhCl(CS)(PPh&(TCNE) [48]. Infrared data seem to support a hexacoordinated structure with TCNE bonded to the rhodium atom via meta&carbon o-bonds. The reaction of trans-RhCl(CS)(PPh,), with CSz to give complexes containing CS and I~-CS, ligands has been discussed already (see p_ 166).

squxe-p!aar

carbony

5. Iridium The chemistry

of the iridium thiocarbonyl, rrans-IrC1(CS)(PPh3)2, has been studied somewhat more extensively than that of its rhodium analogue. The complex was first prepared in low yield by Yagupsky and Wilkinson [ 16 ] from.IrCl(PPh,), or [IrCl(CsHr7_)]2 and CS,. In the case of IrC1(PPh3)3, an unidentified product exhibiting a strong infrared absorption at 1360 cm-l, was also formed. Kubota and Carey [49] h ave reported a high yield synthesis of fmns-IrCl(CS)(PPh& using trans-IrCl(PPh,),(N,) as the starting material_ The reaction scheme (Fig. 2) clearly demon+rates that the nature of the products formed in G-&reactions of transition metal complexes with CS, is highly dependent on the experimental conditions employed. The presence of PPhs and MeOH is essential to the formation. of transdrC1(CS)(PPh3)2. The struc&es proposed for the intermediates, IrCl(PPh&C,S, and IrCl(CS)(PPh&CS,, were based OF the similarity of their infrared absorption patterns in the 1050-800 cm-l region to that of Ni” c&mplexes containing the perthiocarbonatg ligand, CS; r The complex, IrCl(CS)(P~h-&CS, (y(CS).l360 cm-l) was thought to be the unidentified complex obseyed by Yagupsky &d jGlkinson [ 161 in their synthesis of rrans-IrCl(CS)(PPh&. Thermal @composition of kither IrCI(PPi+C2S5 or Irc1(CSj(PP~3)2C!S3 yields a complex which was fqrmulated. tentatively as IrCl(CS)(PPh& CS, __‘j& formation of PPh3S as a byproduct of the reactions involving PPh3 indicates that the latter acts as the suiphur acceptor in the synth& of thiocarbonyls in Fig..2. The low yields and experimental difficulties in their synthetic methods prompted i YaguPsky and Wilkinson [16] to restrict their investigation of the-chetiistj of fl~ns-

179

tmns

If Cl (PPh,),

-

trUnS-IrCI(CS)

(r&J

PPh3,

(PPh&

CHC13/MeOH

Ph3P

s

Fig. 2.

IrCI(CS)(PPh3)2

mainly to a spectroscopic

trans-IrCl(CS)(PPh& of pans-IrCl(CS)(PPh&

survey. In contrast to its carbonyl analogue,

does not’oxidatively add molecular hydrogen. However, treatment with CO and SO, gives the adducts, IrCl(CO)(CS)(PPh3)2 and respectively_ The structure of the latter is believed to be similar

IrCl(CS)(SO2)(PPh&, to that of its c&bony1 analogue, IrCl(CO)(SO,)(PPh,),, viz., a tetragonal pyramid with the SOZ group in the apical position bound to the metal through the sulphur atom.

The hydride, IrH(CS)U’Pha)a, formed from the reaction of trans-IrCl(CS)(PPh,), with NaBHa in the presence of excess PPh,, was actually isolated. Its NMR spectrum indicated a trigonal-bipyramidal Recently, (PPh&

structure with equivalent equatoriaI PPh,

Fitzgerald et al. [SO] demonstrated

groups.

the Lewis basicity of trans-IrCl(CS)-

by successfully forming adducts with boron trichloride, boron tribromide,

cyanoethylene or acrylonltrlle.

and fumaronitrile.

tetra-

No reaction took place with boron trifluoride, ethylene

The boron trihalide adducts could not be assigned a definitive stoichio-

metry.while the two other adducts were of l/ 1 stoichiometry. The BCl, adduct readiIy undergoes hydrolysis to form the hydrogen chloride oxidative addition product, IrHCl,(CS)(PPh&. The thiocarbonyl stretching frequency, v(CS), of the parent complex increases by about 25 cm-’ upon adduct formation. These shifts were interpreted as i&icatlng the diminished transition metal basic&y of the tbiocarbonyl its carbonyl analogue. (L= The cationic_thiocarbonyls of iridium, [Ir(C~),(CS)~]) l

Cy = cyclohexyl, C~HI 1.

complex compared PI%,, PCy3

to

j *, were

180

.-. .’

:.

prepared recently by Mays and Stefanini of the appropriate retracoordinated

[Sl]

complex,

phosphine exchange reaction. The crystal structure of [Ir(CO), me Ir-c(S)

(CS)(PPh3)2]

a CHCl, solution

h ; the tricyclohexylphos-

[PF6] - Me,CO

and the II--C(S)

distances (mean i-938&

providing further support for the

related tricarbonyls

in order to determine the extent of reactivity

by the replacement

of a CO group by CS [Sl].

dihydrides,

cations undergo

the tbiocarbonyl

fails to add Hz under the same conditions.

vation prompted the preparation kinetic investigation

to that of the

change brought about

Whereas the the tricarbonyl

facile reversible addition of H, to give hexacoordinate [Ir(CO)2(CS)(PPh3)2]+,

of [Ir(CO)~(CS)(PCy&]*

of the complexes,

[72].

is significantly

better o-donor and n-acceptor properties of CS compared to CO. The chemistry of &e thiocarbonyl cations was investigated and compared

complex,

in a

shows that the cation

distance (1.867A)

This obser-

in the first place, since a

[IrH2(C0)2L2]C,

had shown that the more basic

the phosphine the less readily was hydrogen displaced from the dihydride. The complex, the most (kinetically) with to hydrogen [IrH$XO)#‘Q&l+, The thlocarbonyl H, to and the ly

derivative,

the dihydride analogue indicate

[Ir(C0)2(CS)(PCy3)2]+,

replaces hydrogen [IrH2(CO)(CS)(PCy&]+ more than in cations and particular, loss H, from CO analogue, by comparison. was suggested this could , is very

of the

Wb(CO)2(PCydd attributed the

to

T-his

better rr-acceptor density at metal and of thiocarbonyls (see p.

of CS destabilizing H2 addition.

Neither [Ir(C0)2(CS)(PPh3)2]i

to CO, state compared

the

been noted

[Ir(CO),(CS)(PCy&]’

dGzarboxylate, although

forms

carbonyl cations

[CpFe(C0)2CS]+

with dido so

complexes, trans-IrCl(CS)L,, be regenerated [Ir(CO)f(CS)I&J’. Tb reaction is to that trans-IrCl(CO)L.2.

Reaction

lowering Irr.

for trans-

room temperature_ on the to

in fact

Spectroscopic data this comhydride and ligands are mutual-

positions. Carbon

by Cl[Ir(CO),LJ+

in anhydrous leads to formation of thioester, CpFe(C0)2C(S)OMe p_ 175). in the [Ir(CO),(CS)nucleophihe attack place at carbon atom a coordinated (pPh&l rather than that of thiocarb&yl.group_ This in the of the

with

Protonation

[Ir(Co),(Cs)(PPh,),l+. the

cation, and Stefr&ni

of

ester regenerates

k .reaction

[Ir(CO),(CS)(PPh,),]’ [Ir(CO)(CSj(PMePhZ)$. also investigated

formation

complex, with

of

affords

cationic species

: ,I

from tra,ls-IrCl(CS)(PPh&

geometry with the phosphines in mutuahy trms positions

group is I&ear (178.2O)

shorter than the Ir-C(0)

rrans-IrCl(CS)

&as synthesized

phine derivative, trans-IrCl(CS)(PCy&,

has a tn‘gonal bipyramidal

by bubbling CO through

181

tram-IrCl(CS)

L2. In these reactions,

the square-planar

thiocarbonyl

complexes

behave in

an analogous way to trans:IrCl(CO) L,. For example, with NOtiF,+, the pentacoordinated cations, [IrCl(CS)(NO)L_]+, are produced. The structure of these cations is probably similar to that of [IrCl(CO)(NO)(PPh3)z}+. be square-pyramidal

with a bent Ir-N-O

gives [Ir(CS)(Diphos),]+

which has been shown by X-ray diffraction.to linkage. With Diphos, trans-IrCl(CS)(PPh3)2

which is analogous to [Ir(CO)(Diphos)a]+.

B. Manganese _ The monothiocarbonyl complex, CpMn(C0)2CS, was first prepared in low yield (< 10%) by reaction of CpMn(CO),(C8H,,) with CS, at about 40” for approximately 1 week [52].

The reaction is complicated

CpMn(C0)3

and various unidentified

by the formation

carbonyl

of minute quantities

plexes. When the same reaction is repeated in the presence of excess PPh,, complex is produced in essentially ducts are PPh,S

and cis-cyclooctene

quantitative (C,H,,).

of

and/or carbon disulphide-containing yield after 24 h [53].

com-

the thiocarbonyl

The on&other

Infrared evidence and kinetic data [54]

the reaction suggest that it proceeds by an SN1 dissociative

mechanism

profor

involving the slow

loss of CgHl4 in the rate-determining step to form the coordinatively unsaturated species CpMn(CO), which then undergoes rapid reaction with CS,, followed by sulphur abstraction by PPh3. The complete

slow

proposed mechanism

9

-0iefin

is shown in Fig. 3.

:;;>

9

Mn’ co4

Mn* co‘I\ co

co

lc=s / s

-LPPh3

1 fast

9 Md

4’ co

Fig. 3.

co

+ cs

PPh~S

,‘182‘.

..

:: _.

:

.The,-IR data leave little doubt asto the formation of the intermedi&e @&r(CO)2CS2..$~ as a ,~-n_CS2:corriplex;‘Moreover, its:[email protected] not- um2soriable tihen.one remembers tha$ .$ : the syntheses of the Group~ViiI metal thioc’arbonyis also appear to inv&e-%-CSi- inter-mediates. Structr.& XV is proposed [54] ‘for CpMn(CO)@ZS$ -Such a heptacoordimkd :i n-cyclopentadienyIm&igauese(III) dicarbonyl species is not withoutprecedent because’ ,: the complexes, CpMn(CO)&SiP$)H f55], CpMn(CO)t(SiCl$H [56] and CpMn(C0)2(SiCl$(SnCl,) [57] have been synthesized recently. X-ray data for CpMn(C0)2(SiPh3)H suggest the presence of a hydrogen bridge between manganese and silicon, thus forming a three-membered ring similar to that proposed for CpMn(CO)2(n-CS2).

The mechanism of the reaction in the absence of PPh, is difficult to assess. However, there is some evidence [54] that suggests that CpMn(C0)2CS, CpMn(CO)s and the other products may be formed via thermal decomposition of CpMn(CO)&CS2). Infrared data have also been obtained [54} for the methyl-rr-cyclopentadienyl derivative, (Ir-MeC~H4)Mn(CO),CS. Both CO groups, but not the CS group, in CpMn(C0)2CS undergo UV induced substitution with Cl80 [58], C,H,,, Diphos [54], and various monodentate Group VA ligands such as PPh3, SbPh3, P(OMe)3 and P(OPh)3 (591 to form CpMn(CO)(CS)L and CpMn(CS) L2. Some of the Group VA derivatives, CpMn(CO)(CS) L, exhibit “CO frequency doubling” presumably due to conformational isomerism similar to that observed for various other n-cyclopentadienylmetal carbonyl derivatives, e.g., CpFe(CO),SiMe,Cl 1601 and CpMn(CO)&r-Buq 16 l] _No splitting of the CS absorptions was detected for any of the thiocarbonyl derivatives. The cis-cyclooctene derivative, cpMn(cO)(cS)(c8H14), has been used as a precursor to CpMn(co)(cs), and CpMn(CS)3 [53]. CpMn(co)~cs

+ CgH,4

cP~(~aKsxc*EJ~4) cP~(co)(cs)2

hu

+ cs,

+ C&$4

-

CpMn(CO)(CS)(CsH14) pph hV

.3

CpMn(CO)(CS)2

CPMdCS)&$$4)

+ CO + C,H,, + CO

+ PPh,S

It%.& the dithiocarbonyl d&i
is of interest that the v(CS) frequencies for the CpMn(CS)Lz derivatives are lower than those for the related CpMn(C@(CS)L derivatives [59]- This may imply that the C-S bond in the former has become weaker with concomitant strengthening of the Mn-CS bond, A sin&r bond-weakening/bond-strengthening effect has been noted for the C-OIh4n-CO bonds in the analogous CpMn(CO),L complexes on replacement of CO by L 1643. The mass spectra of CpMn(CO),CS, C~~GI(CO)(CS)~ and severai of the CpMn(CO)(CS) L and CpMn(CS) Lz derivatives have been recorded [S4,593. The proposed fragmentation pathways for the degradation of CpMn(CO),CS are shown in Fig. 4. All the spectra exhibit peaks corresponding to the parent molecular ions, as do the spectra of their carIt

9 dTni co m/e

220

&?n+

-co -

==

-co Mn+

I\

ccl

m/e

-

CS

m/e 192

-.

Fig_ 4.

.m(e

99

55

i84

.

-.; cleavage is favoured over C-S, bond cieavage;, .. : : ai for CO;’ the .f&mentation of CS from-the n&nganese atom ‘occurs in one St&p:Idiioib j trast.to: the. CpMn(CO)2L derivetives, for which both CO groups are lost sirr$taneously bony1 analogues [6S],Moreover,

Mn-CS_bond

from the p~arent rriolecular ions;-CpMn(CO)&S follored

by t$e loss of CS. There is a peakat

high resolution

exhibits

proves to be due to Mn(CS)~;The

addition to Ythepathway’!eading also lose the Ir_cyclopentadienyl

the stepwise Loss of ihe CO groups

m/e 99 in all of the spectra.which

under

presence of this’peak indicates that, in

to CpMn+ (m/e j20), the.CpMn(CS)i ion (m/e i64) may ring before rupture of the Mn-CS bond. This contrasts to

the fragmentation of Ir-cyclopentadienylmanganese carbonyl complexes where the groups &rd any other ligands present are always lost before the ring [66] _ The kinetics and mechanism of the cis-cyclooctene (c8 HIa) by PPh3 in methylcyclohexane range employed OO-700),

substitution

have been investigated

the rate is approximately

ogous reaction of CpMn(CO),(C,H,,)

with PPh,.

.CO

in CpMn(CO)(CS)-

[67] _ Over the temperature

four times faster than for the analThe kinetic data for the thiocarbonyl

reaction are in accord with the following S, 1 dissociative mechanism, i.e., a similar mechanism to that proposed by Angelici and Loewen for the reaction of CpMn(C0)2(C8H14)

with PPh,

[68]. slow

CpMn(CO)(CS)(C@l4) That the.&iocarbonyl

l

-C8H14

CpMn(CO)(CS)

reaction is significantly

h

fast +PPH3

CpMn(CO)(CS)PPh3

faster than that for the carbonyl

complex

can be explained in terms of the greater n-acceptor capacity of CS compared to CO. Finally, the absolute integrated infrared intensity of the CS stretching mode in CpMn(C0)2CS has been measured in CS2 solution 1691. The value calculated for the associated dipole moment derivative p’(CS) is supportive of the similar bonding characteristics of CS and CO. IV. Conclusion This review has shown that over the past seven years a great deal of research has been carried out on the activation

of CS2 by transition metal complexes.

Nevertheless,

this

topic remains largely unexplored. In particular, little structural data on the five main types of complexes have been reported and the best synthetic procedures are only just becoming apparent. In the case of the metal thiocarbonyls, it is obvious that the generation of the CS &and from CS, necessitates the presence of an efficient sulphur acceptor such as PPh,. The physical and chemical properties of the thiocarbonyl complexes seem to point to the greater stability of these complexes compared to the analogous carbonyl ones, in agreement &-ith .the theoretical predictions of Richards [42]. This means that the present scarcity of metal thiocarbonyls is probably instability of the complexes.

due to experimental procedure rather than the inherent

.’ ’ ’

In conclusion, it is clear that the use of CS, as a solvent for reactions involving transition metal complexes must be carefully considered in future. Carbon disulphide undergoes many more reactions than is often realized. Of the five main types of complexes examined in this review, it is anticipated that in the next few years the study of CS, insertion and thiocarbonyl complexes will prove to be two of the most fruitful areas of research in transition metal chemistry. V. Infrared data for carbon disulphide and thiocarbonyl complexes Infrared spectroscopy provided the chief physical tool used in the studies described in the preceding sections of this review. Consequently, we felt that an analysis of the infrared data collected for the known carbon disulphide and thiocarbonyl complexes would be of importance for future investigations in this field. The frequency ranges for the CS stretching absorptions for the different types of complexes are shown in Table 1; the corn-’ plete data are listed in Tables 24 *_ Of particular interest is the range of the v(CS) frequencies in metal thiocarbonyls, viz., 1381-l 193 cm-l _ This is somewhat surprising in view of the similarity in bonding properties of CO and CS. Upon coordination, the CO stretching frequency of free CO decreases from 2143 cm-l to approximately 2000 cm-l (sometimes even as low as 1850 cm-l for terminal CO bonding). However, it appears that the CS stretching frequency can both increase and decrease with respect to the frequency of “free” CS (1274 cm-l when trapped in a CS2 matrix [70]). Since n-backbonding is almost certainly present in metalCS bonds, the most probable explanation for this effect lies ‘m the extent of coupling of the CS stretching modes with the low frequency modes (below 700 cm-l) of the molecules. TABLE 1 u(CS) FREQUENCY RANGES FOR THE KNOWN TYPES OF TRANSITION METAL CS2 AND THIOCARBONYL COMPLEXES Type of complex

rGSl(cm-‘1

1235-95s M-S=C=S M-CS2-M M-S2CXd M-CS

=, 653-632

b

1520-1503 980,840 e 1267-815 e, 780-6125 1381-1193

Q Out-of-ring v(C=S) vibration. b In-ring Y(C-S) vibration. c Data only available for one CS2 bridging complex viz., R~[(CN)~COCS~CO(CN)~ ] [9,19]. d X = H, alkyl, aryl, or amine. e V(CSz)asym. fv(CS*&n. * Notd that data are only presented for those complexes whose molecular stoichiometries and probable

structures have been reasonably weII estabIished.

.:‘(.

.-

_

:

_--d__-0000000

‘~.~‘~-~--s-~.5,~

%%%%%%%v

i

.--_.1_--

1152 1152

1145

1151 1177 1167 1141s 1163 653

636 632 651s

1520

d

Nujol Nujol Nujol CH2Cl2 Nujol Nujol

(32

(32

8 8 6 6 a,40 8 6 17

8 8

Nujol Nujol Nujol

d

Nujol

a 16 16 9 16 16 16

Nujol Nujol

8

Nujol (32

.,

flY(C=S),out.of.ring vibration; UK-S), in-ringvibration.The relative intensitiesgivenate those quoted in the variousrcfcrences.In those cases where the nCS2 absorptions were not specificallyassigned,the assignmentsgivenarc those of the present authors,6 Alreadypresent but less intense in the parent compound RhClzI-I(PPh&)3. c The two v(C=S) absorptionsobservedfor this complex were attributed to the prcscnccof two isomers differingin the orientation of the nCS2 ligdnd.d Mediumunspecified.

--_I_

Pd(Dipho&n-C&), PtVPh$&rCSz)

1193 1176 1190 1178 1146s 1160s 1179

1117

1122 1196

1510

1009m 1000s 1000s

1510

1154 1165s 1012m 1009m

1161 1188m 1106m 1106m 1170 1106m 1005m 1OOSm

.’

‘.

‘. :

,.

‘,

',

,, ::

..’

‘,

,’

,.

‘,

,,

.’

..,

,’

',

”

.,

‘.

‘,

,‘. .___.__I___ ‘, ,’

”

vv&)~

. . __.-.~.--:---.-L-.-.--_+-

_.-___--.-_-_-

KBr KBr KBr KB; KBr 616m 613m 612m 616m 623m

‘Rk(C0)4(SSCk) : Re(CO)&SSCPh)’ (’ Rd(~0)4[~SC’OI-McCaHq)l Rc(CO)4[SSC@CtCcjH4)] Rc(Cd)#Ph,)(SSCPh)

114Gm 1267 1264m 1258m ,126Sm

22 22

Nujol Thin film KBr KBr

930 618m 613m

25 25 24 KBr KBr Nujol

1267m 1265m

930

645 780

Fran! iti~ation into tneral-carlton bortds ‘Mn(C0)4W$ZPl~) i Mn(CO)r,[SSC(p-McC6H4)]

815 1008 940

25 25

Ref.

KBr KBr

Mcdilim

.lOSO 1050

RF(COjj(PhzPCH*PP1,2)(SSCtl) Rc#ZO)~(Diphos)(SSCH) Rc(C0)2(PPh3)2(SSCtl)

ComplcX,‘I asym sym ” ,~_____..__ ._._.___.___ .._ ___________.,-__... .-...._.-- .____..-_____.___l+onr insertiott into tnctal-ltydrogetl bonds 652? 818 Mn(CO)g(Ph2PCH2PPII2)(SSCtI) 992 719 Mn(CO)a(Diphos!(SSCH)

.,

CARBON4ULl't~URABSORPTlONS(cm") FORCS21NSERT10NCOMPLEXES

TABLE3

.’

PtCi(PPh$,(SSCH) ,P~CI(PE13)2(SSCH)

.’

,,

,‘,

‘.

:‘, .’

.’

,, ‘,,I’ .,

,’

,,

‘,

;:. ).

.,

,I .,/

‘.’

‘.,

‘,’

;

‘,

.’

,’

‘:

‘,

‘.;

“:

,.

.'

..’

.’

_.,

‘,.’

.’

m.,

i_:

,.:“:

‘..’

2.

c

34 34 34 34 34 34 34 34 36 36

CHaCl2 CH2Cl2 CHaC12 CHaCla CH2CIa Cf-l2Cl2 CH2C12 CHsCls Nujol Nujol

996 1003 1000 1045 1045

Nb(SSCNMc& Nb(SSCNEt2)4

Ta(SSCNMc&

Ni(SSCNU‘)2 NHSSCNQMe)?

- _ __ __. . .. .._... ..

__._. _____

0 nle relative intensitiesgivenarc those quoted in thevariousreferences,In.those caseswherethe v(CS2)absorptionswetc not specificallyassigned, the assignments given are those of the present authors,b u(n-CS2)1003scm-‘, c Mediumunspecified.

’

998 999 994 1006 1000

Zr(SSCNEt2)4 Zr(SSCWn-k2)4 .V(SSCNMe& V(SSCNEt2)4

Ti(SSCNn.Pr&

Tf(SSCNEt&'

Zr(SSCNMe2)4

17 17 34 34 34

c

CH2C12 CH2Cl2 CH2C12

630

1002 1004 994

1110 1261111

Ti(SSCNMea)4

fibrn indbrtion’into metal-nitrogen borrds

‘Rh12(PPl13)2(SSCMe)~ C&j Rh0’Ph3)3WS2)(SSCPh) I’

,.

-.-___--__--_.

Cpkn(C$ (Triphkj

CpMn(CO)(CS)(P(OPh),I Cp,MniCS, (PPh& CpMnKS) (PMc2Ph)z CpMnKWP(OMe)3l2 CpM@S)[P(OEt)3 12 CpMn(CS)[P(oCH2CH2CI)3]2 CpMn&S)[P(OPh)& CpMidCWDiphos) :

CP~~~(~O)(CS)[PIOCH~CA~CI)~ ]

CpMn(Co)(CS)[P(Oet),I

CpM~(CO)(CS~I’P(OMc)J]

CpM1$0)(&‘Ikk~Ph I’ CpMn(C6)(CS)(PCy3)

CpMn (CO)(CS) AsPh3 CpMn (CO)(CS)SbPh3

(n-M&s H4) Mn (CO&CS CpMn(CO)(CS)(CBC114) CpM,n(CO)(CS)PPh3

C~MII(CO)~CS

Complex

_..__-l__--_---

1266s 1271s 1262s 1242s 1231s 1236s 1217s 1231s 1230s 1237s 1228s 1234s 1222s 1230s 1239s 1245s 1236s 1243s 1240s 1247s 1254s 1193s 1195s 1218s 1214s 1223s 1219s 1207s 1211s 1203s.b 1206s,C

___.._-..-_..--------^-_.

v(CS) u

cs2

(32

Nujol

cs2

(32

(32

(32

cs2

(32

i-32

cs2

n-hexanc

(32

n-hcxane

cs2

n-hexanc cs, n-hcxane CS2 n-hexanc

cs2

n-hcxanc

(32

(32

n-hcxanc Nujol

f32

(32

(32

Nujol

cf32

_-..-__

Medium

CARBON-SULPHUR ABSORlWONS (cm-* 1 FOR THIOCARBONYL COMPLEXES

TABLE 4

59 59 59 59 54,63 54 63 63

52,.54 52.54 54 54 54 54 54 59 59 59 59 59 59’ 59 ‘59 39 59 59 59 59 59 ‘59 59

Rd.

.,’

.)’

‘,

;

‘,

:

.:..

0‘ .,‘,’

;;,.

.’

14)

63 53,54 54 54 53‘54 54 54 63 63 63 63

C6H6 C6H6 C6H6 C6H6 C6H6 CH2C12 Nujol Nujol Nujol

1299 1298 1362 1355 1304 1355 1289vs 1289vs 1328s 1315s 1305vs 1305vs

rruns-RhCl(CS)(PPh3)2 ir&RhBr(CS) (PPh3)2 RhCl3KS) (PPh3)2 RhBrj(CS) (PP113)2 f~airs_Rh~SdN)(CS)(PPh3)2’ RhCI(C+)(PPh3)2(TCNE)g [Rh(CS)(PPh3)2(CS2)(n-CS2)1BPh4 [pa(CS)(PPh3?2(n~S2)lBPh4

frans-JrCl(CS)(PPh3)2 rro;lS-lrCl(CS)(PCy3)2 [I~~CS)(PPII~)~~CS~)~~‘CS~)IBPJI~ ‘[JriCS)(PPh3)2(n~S2)lBPh4

Nujol Nujol Nujol

46

Nujol

(continued)

16 51 16 ,16

9 45 16 16

9

9

9

9

11 11

[RuCl2(CS)0’Ph3)2l2 RUCl2(CO)KS)(PPh3)2 “‘RlJCl2(C!S)(Py)(PPh3)2 R~CI~(C!S)(B~~~)(PP~~)~O.SCH~C~Z RuCl2(CS)(Phh)(PPh3)*0SCH2C12 Ph4As(RuCl&CS)(PPh3)2 1

::

f

llCXdChJOrO- 43 butadicnc 44 CS2

CS2 CS2 CS2 CS2

CS2 CS2 Nujol cs2 CS2 CS2 Nujol

::

1235~s 1240s 1217~s 1240~s

11 11 11

1316

1348s

1203s 1305s 1308s 1289s 1338m 1226s 1230s 1204m d 1208m e 1205m 1209m

1290s 1290s 1280s 1280s 1280s 1272

.’ CpFc (CO)(CSXObMe)

[CpMnK!O)WS)]~(Diphos~

CpMW%

CpMnW2Kell

CpMn(CS) (Triphos=O) CpMn(CO)(CS)2

‘I5

PPh4

1360 1289 1345 1252 1321s 1303s 1332s 1322s 1287s 1381s 1340s 1263s 1297 1361 1377 1370 1350

vICS)a

. .-.-_-

. ..__

:

Nujol Nujol Nujol Nujol Nujol :

cm3

CHCl3

cIIc13

CIKI3

KBr tolucnc CH2C12 Nujol

51 51 51 51 51 50 50 50 50

51 51 51

5’

46 16 16 16

.2. . _.._.._ Medium Ref. ____

a Abiorptions associated with nCS2 or S-bonded CS2 groups arc listed in Table 3. The rclutivc intensities given arc those quoted in the variousrcfcrences./J yisorner. c r~5 isomer. d-+somcr.’ Ed isomer. f Mddiuni tkpccified. 6 TCNE = tertracyanoethylcne, C2(CN)4. I’,PUM = fumaronitrile,C4N2 Hz.

l

Ir(CO)(CS)W’h3);(COOMc) (!rCI(NO)(CS)(PPh3)2]BF4 [Wl(NO)(CS)O’Cy3)2]B~4 [Ir(CS)(Diphos)z/BPh4 [Ir (CO) ES) (PMcPh2)31BPb4 IrCWSWh3)~ (BCl3),, IrCI(CS)(PPh3)2 9(BBr3),1 IrCI(CS)(PPh3)2*(TCNE)R IrCI(CS)(PPh3)2 l(PUM) II

I!~D~(CO)(CS)(PCY~)~]C~O~

I!rH2(CO)(CS)(PCy3)21C104

[IrK0)2(9(PC~3)2

~Ir(CO)2(CS)(PPil3)2]Rl’h4

IrCI(CS)(PPh3)2(CS3) IrCI(C0) (CS) (PPR3)* lrCl(CS)(SOz)(PPh3)2 IrHW(PPh3)3

compicx

TABLE 4 (corMwed) -___L .^_... -- _..._..--...,-._..,._ ...__......__.._._

193 I

References

.

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’

~

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(1970)

Note added in proof Angelici

and co-workers

have succeeded

in isolating

M(C0)5 CS (M = Cr, MO, W) and [PtCl(PPh3)2 [M (CO) 5] 2-- + Cl, C=S

W’Ph3)4

+ Cl (OMe)C=S

four new meta

(CS)] + by the following synthetic

viz., routes:

+- M (CO)5 CS + Xl+

PtCNPPh,)2

(CSOMe)

st;

For details see R.J. Angelici, B.D. Dombrek &d E. Dobrzynski, on Organometallic

thiocarbonyls,

[PtCI(PPh&(CS)] 6th International

+ Conferen&:;

Chemistry, Amherst, Mass., U.S.A., August 1973, abstract no. 134.