Transition Met. Chem. 3 ,211-214 (1978) ©Verlag Chemie, GmbH, D-6940 Weinheim, 1978

was filtered off, washed with Et20 and recrystallised from CH2C12 : i-Pr20 giving the complex as orange crystals (0.1 g, 25%).

The compounds [ Rh(CN Et)2(PPh 3)2(HgCI)CI ][ PF6 ] (white crystals, 29%) and [Rh(CNEt)2(PPh3)2(Me)I][PF6] (yellow powder, 58%) were prepared similarly.

[ Rb( C N C t H I 1 )2 (PPh3)2CI2 ][ PF6]

A solution of [Ph(CNCtt l I l)2(PPh3)2 ][PF6] (0.4 g) in Me2CO (30 cm j ) conta in ing MeCOCI (2 cm j ) was stirred for 2 h. On addit ion of i-Pr20 and concent ra t ion of the mixture in vacuo, a pale yellow solid precipitated. This was filtered off and recrystallised from CH2C12 : i-Pr20 mixtures to give the complex as yellow crystals (0.16 g, 24%).

The compound [Rh(CNCtHI I)2(PPh3)2Br2][PFt] (yellow solid, 65%) was prepared similarly.

[ Rb( CNC101t7 )2 (PPb3 )2 Cl2 ][PF 6 ]

The complex [Rh(CNCIoHT)2(PPh3)2][PF6] (0.2 g), dis- solved in Me2CO (25 cm3), was treated with MeCOCI (2 cm3). After stirring for 45 min. the solut ion had become colourless and on addi t ion of EtzO gave a creamy-white precipitate. This was filtered off and recrystallised from Me2CO : Et20 mixtures, giving the complex as white crystals (0.08 g, 37%).

Bis(cyclopentadienyl)zirconium(I V) Oximate Complexes 211

Acknowledgements

We are grateful to the SRC for its support, to Mrs. J. War- rington, Mr. A. Jones and Mr. G. A. Wright for technical assistance, and to Dr. J. Dart for advice.

References

(1) Part I. J. W. Dart, M. K. Lloyd, R. Mason and J. A. McCleverty, J. Cbem. Soc. Dalton Trans., 2039 (1973).

(2) Part. 2. J. W. Dart, M. K. Lloyd, R. Mason and J. A. McCleverty, J. Cbem. Soc. Dalton Trans., 2046 (1973).

(3) K. Kawekami, K. Take-Ouchi and T. Tanaka, lnorg. Chem., 14, 877 (1975); A. L. Balch and M. M. Olmstead, J. Am. Cbem. Soc., 98, 2354 (1976); S. Otsuka and K. Ataka, Bldl. Chem. Soc. Japan, 50, 1118 (1977).

(4) K. R. Mann, J, G. Gordon and H. B. Gray, J. Amer. Chem. Soc,, 97, 3553 (1975).

(5) J. Chatt, R. L. Richards and G. H. D. Royston, J. Chem. Soc. Dalton Trans., 1433 (1973).

(6) P. R. Branson and M. Green, J. Chem. Soc. Dalton Trans., 1203 (1972); P. R. Branson, R. A. Cable, M. Green and M. K. Lloyd, ibid., 12 (1976).

(7) J. W. Dart, M. K. Lloyd, R. Mason, J. A. McCleverty and J. Williams, J. Chem. Soc. Dalton Trans., 1747 (1973);J. A. McCleverty and J. Williams, Transition Met. Cben1., I, 288 (1976). J. M. Jenkins and B. L- Shaw, Proc. Cbem. Soc., 279 (1963). J. A. McCleverty and G. Wilkinson, lnorg. Syntb., 8, 211 (1966). J. A. McCleverty and G. Wilkinson, hlorg. Syntb., 8, 214 (1966).

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Preparation and Characterization of Bis(cyclopentadienyl)zirconium (IV) Oximate Complexes*

Gopal Gupta, Ram Sharan and Ramesh N. Kapoor**

Department of Chemistry, University of Delhi, De lh i -110007 , India

(Received January 5th, 1978)

Summary

Oximate complexes of bis(cyclopentadienyl)zirconium(IV) chloride (CpzZrCI2) having the general formulae Cp2Zr(Ox), Cp2Zr(OxH)C1 and Cp2Zr(OxH)2 [where OxH2 = RC6H4C(OH)R': NOH, R = H, Me, R' -- H, Me, Et, n-Pr; PhC: N(OH)CH(OH)Ph and R"C : N(OH)N(OH) : CR", R" -= H, Me and Ph] have been synthesized by reacting bis(cyclopenta- dienyl)zirconium(IV) chloride with the appropriate oxime in te t rahydrofuran in the presence of t r ie thylamine at room temperature. The complexes have been characterized by

* Reprints of this paper are not available. ** To whom all correspondence should be addressed.

their elemental analysis, i.r. and electronic spectra, molecular weight determinat ion, electrical conductance and magnetic measurements.

In t roduct ion

Complexes of various metals with oximes have been studied in detail and have been reviewed recently (l) and interest in such complexes continues because of their analytical applications. Many zirconium compounds having Z r - O - C bonds have been reported (2-4), however, little is known about complexes containing Z r -O-N and Z r - N - C bonds. Recently Mehrotra et al. (s) studied the reactions of Zr(OPr-i)4 " i-PrOH with oximes.

212 G. Gupta, R. Sharan and R. N. Kapoor Transition Met. Chem. 3, 211 -214 (1978)

There is no reference in the l i terature regarding the pre- paration and characterizat ion of any oximc derivatives of bis(cyclopentadienyl)zirconium(1V) halides. It is, therefore, considered of interest to study the reactions of bis(cyclo- pentadienyl)z i rconium(IV) chloride with different oximes in different molar ratios in nonaqucous media. A large number of oxime derivatives of various metals have been synthesized, in the presence of bases such as triethyl- amine (6-8).

Experimental

All operat ions were carried out under strictIy anhydrous conditions. THF (BDII) was dried by storage over sodium wire overnight and was then boiled under reflux until it gave a blue colourat ion with benzophenone. It was finally dried by distilling over LiAIH4. n-Hexane was dried by distilling over sodium wire.

Oximes were prepared by known methods (9-1°). CpNa and b is (cyclopentadienyl )z i rconium(1V)chlor ide were prepared as reported in the li terature (11' 12)

Zirconium was determined gravimetrically as ZrO2 and chloride was determined as AgCI. Nitrogen was estimated by Kjeldahl 's method. Analytical data of "all these complexes arc given in Tables 1 and 2. Molecular weights of the com- plexes were determined in boiling benzene by ( ;a l lenkamp Ebull iometer , W. G. Pye and Co. Ltd., Cambridge, U. K. The i.r. spectra were recorded on Perkin Elmer IR-621 and IR-137 instruments in Kgr phase in the 4 0 0 0 - 2 0 0 cm - l and 4 0 0 0 - 7 0 0 c m - l ranges. The electronic spectra of the complexes were run on a Perkin-Elmer 4000A instrument in the 4 0 0 - 7 5 0 nm range. Magnetic measurements were carried out by Gouy ' s method using copper sulphate as calibrant. Electrical conductance measurements were carried out in ni t robenzene on a Beckmann Conduct ivi ty Bridge Model RC-18A.

Reaction o J" bis(c3,clopentadienyl) zirconium(IV) chloride (1 mole) with 2-hydroxy-5-metbylacetopbenoneoxirne (1 mole)

A mixture of Cp2ZrCI2 (1.00g) and oxime (0.687g) was dissolved in TIIF (80g) and tr iethylamine (0.715g) was added. The mixture were stirred for 24 h and the Et3N • HCI

which precipitated was removed by filtration. Solvent was removed under reduced pressure and the product (80%) was rccrystallized f rom n-hexane :THl : . (Found: Zr, 23.8; N, 3.1. C l2Hl9NO2Zr calcd.: Zr, 23.6; N, 3.6%).

Reactio;l o f bis(cyclopentadienyl)zirconium(1V) chloride (1 mole) with c~-benzildioxime (1 mole)

To Cp2ZrCl2 (0.917g) and the oxime (0.668g) dissolved in THF (80g) was added t r ie thylamine (0.324g) and the mixture was stirred for 24 h. Precipitated Et3 N " HCI was removed by fi l tration and the complex was crystallized from n - h e x a n e : T l t F (Yield 75%). (Found: Zr, 18.2; N, 5.1; CI, 6.15. C24112tCIN202Zr calcd.: Zr, 18.4; N, 5.7; CI, 7.0%).

Reactien of bis(cyclope,mTdienyl)zirconium(IV) chloride (I mole) with dimethylglyoxime (2 moles)

The oxime (0.919 g) was added to a solution of Cp2ZrCI2 (1.32g) in dry TI tF (75g). To this, t r ie thylamine (0.923g) was added, the mixture was stirred for 30 h then dried under rcduced pressure and complex was extracted with THF (Yield 72%). (Found: Zr, 19.8; N, 11.9. C18H24N404Zr calcd.: Zr, 20.2; N, 12.4%).

Results and Discussion

A systematic study of the reactions of bis(cyclopenta- d ienyl)z i rconium(IV) chloride (1 mole) with hydroxy- or:imcs (1 mole) in the presencc of t r ie thylamine yielded complexes of the type Cp2Zr(Ox): where IOxl = - represents the anion of the corresponding oximes

TH F" Cp2ZrCl 2 + OxH 2 + 2 Et3N ~ Cp2Zr(Ox) + 2 Et3N • HCI

~ ()I t

I~." ~ "CH '=N( ) I I and PhC: N(OII)CfI(OI-I)Ph

t{ = H, M e R' = I I , l~,[t ~, lad.t, H - P Y .

These oximatc complexes are light to dark brown and are soluble in benzene, te t :ahydrofuran, ch loroform and acetone.

Tab le 1. R e a c t i o n s o f C p 2 Z r C I 2 wi th hydr t~xyox i rncs

R e a c t a n t s S t i r r ing P r o d u c t , c o l o u r aJa,.l F o u n d (Calcd . )% (Molar Rat ios) T i m c (h) dec . t e m p t °) Zr. N

C p 2 Z r C I 2 + S O x l l 2 a) + E t3N 24 C p 2 Z r ( S O x ) 2 6 . 0 3.7 (1 : 1 : 2) b r o w n , 2 4 0 (25 .6) (3 .9)

Cp2ZrCI2 + A O x l l 2 b ) + Et3N 24 C p 2 Z r ( A O x ) 2 3 . g 3.1 (1 : 1: 2) da rk b r o w n , 235 (23 .6) (3 .6)

Cp2ZrCI2 + I 'Ox t l2 c) + Et3N 30 (~p2Zr ( l 'Ox) 22 .3 3.4 (1 : 1 : 2) d a r k b r o w n , 2 1 0 (22 .0) (3.5)

Cp2ZrCI2 + BOxl l2 d) + Et3N 30 C p 2 Z r ( B t ) x ) 21 .7 3.25 ( 1 : 1 : 2 ) b r o w n , 193 (21 .2 ) (3 .4)

C p 2 Z r C I 2 + B 'Ox l l2 e) + Et.~N 24 C p 2 Z r ( B ' O x ) 20 .6 3.35 (1: 1 : 2 ) l ight b r o w n , 217 (20 .4 ) (3 .1)

a) SOxll-~ = sa l i cy la ldox ime ; b) A O x H 2 = 2 - h y d r o x y - 5 - m e t h y l a c c t o p h c n o n c o x i m c ; c) i>OxH2 = 2 - h y d r o x v - 5 - m c t h y l p r o p i o p h e n o n e o x i m c ; d) BOxH 2 = 2 - h y d r o x y - 5 - m c t h y l b u t y m p h c n o n c o x i m e ; e) B 'Oxt l 2 = u- "lenzo nox me.

Transition Met. Chem. 3, 211 214 (1978) Bis(cyclopentadienyl)zirconium(IV) Oximate Complexes 213

Analyt ical data and physical properties are given in Table i . React ions of Cp2ZrCI2 (1 mole) with oximes (1 or

2 moles) in te t rahydrofuran in the presence of t r ie thylamine yielded complexes of the type Cp2Zr(Oxtt)Cl and Cp2Zr(OxH)2 :

THI" Cp2ZrCI2 + O x H 2 + E t 3 N } C p 2 Z r ( O x H ) C I +

Et3N • HCI

Cp2ZrCI2 + 2 0 x H 2 + 2 Et3N TI-II,~. Cp2Zr(Oxlt)2 +

2 E t 3 N ' HCI

[OxH]- represents the anion of the corresponding oxime:

t{" I{" \ C _ _ C /

II II N N / x

It{) {)II

R" = H, Me and Ph.

The complexes are cream to yellow, sparingly soluble in te t rahydrofuran but insoluble in benzene and chloroform. Analytical data and physical properties are given in Table 2.

All the above reactions arc quite facile in THF even at room temperature, but in benzene and acetonitr i le the reac- tions arc slow. The complexes are susceptible to hydrolysis and decompose on heating above 150 °. Magnetic susceptibili- ties, measured at room tempera ture by Gouy ' s method using copper sulphate as calibrant, show that the complexes are all diamagnetic. Electrical conductance measured in nitro- benzene show them to be essentially nonelectrolytes . Molecu- lar weights of the soluble complexes in boiling benzene indicate that the complexes are monomeric .

On the basis of elemental analysis, molecular weight determinat ion, i.r. and electronic spectra, the fol lowing structures are assigned for the complexes of the type: CpzZr(Ox); Cp2Zr(OxH)Cl Cp2Zr(Oxrt)2

• - , N ) r ep resen t s the an ion o f the o x i m e

O

( }.-,-[ t - o o o

/ . .N~/N_. . . x

( ;H ()[1 O - t l " . O

(2) (3)

r ep resen t s the anion of oximc

K6pf(13, 14) has reported structures similar to structure

(1). In all complexes having structure (2) the coordinat ion number of z i rconium appears to be five. Tandon (15) e t al.

have also reported the coordinat ion number five for the zirconium complexes. The appearance of band at ca.

360 cm -m due to u ( Z r - C l ) confirms the presence of co- ordinated chlorine. For complexes of type Cp2Zr{Oxl4)2, (3) z i rconium attains the coordinat ion number six which is well known (16). Complexes of bis(cyclopentadienyl)- z i rconium(IV) chloride having similar positions for the cyclopentadienyl ring as in structure (3) are known (17). , Pfeifer(l 8) and Brady (19) have suggested a five membered ring structure (4) for Ni and Co complexes of dioximcs.

1 t R / c - - c II II N N

(),e xlk( XOl-I

(4)

M = Ni or Co It appears that (2) and (3) have similar types of ring.

l.r. s p e c t r a

The impor tant i.r. frequencies are given in Table 3. Ab- sorption bands, indicating the presence of the cyclopenta- dienyl group, are at ca. 3000 cm -1 u ( C - H ) , ca. 1435 cm -1 u (C-C) , ca. 1020 cm - l 6 ( - C H ) and a band at ca~ 810 cm -I 8 ( -CH) . All these bands correspond to those of bis(cyclo- pentadienyl)z i rconium(IV) chloride (20). The persistence of the bands of cyclopentadienyl rings in oximates indicate that these groups remain delocalized and 7r-bonded to the metal and retain their aromatic character.

The i.r. spectra of the oximes exhibit a band at ca.

3300 cm - l assigned to P(OH). This band vanishes in the

Tab le 2. R e a c t i o n s o f C p 2 Z r C l 2 wi th d i o x i m c s

R e a c t a n t s S t i r r ing P roduc t . c o l o u r I . 'ound (Calcd. )% (Molar Ra t ios ) Time (h) a n d dec. t e m p ( ° ) Zr N CI

Cp2ZrCI 2 + I )P( ; I I2 a) + Vt3N 24 Cp2Zr( I )PGt l )CI 18.2 5.1 (1 : 1: 1) b r o w n , 2 0 0 (18 .4) (5 .7)

Cp2ZrCI 2 + I)PGII 2 + i ( t3N 30 C p 2 Z r ( D P ( ; I I ) 2 13.6 7.5 (1 : 2: 2) l ight ye l low, 2 3 0 (13.O) (8 .0)

C p 2 Z r C I 2 + D M G I t 2 b) + E t3N 30 C p 2 Z r ( D M G H ) C I 24 .9 7.2 (1 : 1 : 1 ) l ight b r o w n , 205 (24 .5 ) (7 .5)

Cp2ZrCI 2 + I)M(;II 2 + I,it3N 30 C p 2 Z r ( I ) M G H ) 2 19.8 11.9 (1: 2: 2) c ream, 227 (20 .2) (12 .4)

Cp2ZrCI 2 + GII2 c) + Et3N 24 C p 2 Z r ( G H ) C I 26 .0 7.5 {1 : 1: 1) ye lh ,w, 217 (20 .5) (8 .15)

Cp2ZrCI 2 + 4;112 + t ' i t3N 24 C p 2 Z r ( G H ) 2 23.9 13.6 ( 1 : 2 : 2 ) c ream, 2 3 4 (23 .1) (14 .1)

6 .15 (7 .0)

8 .85 (9.5)

9 . 8 (10.3)

a) i)P(;142 = a - B e n z i l d i o x i m e ; b) DMGII2 = I ) imcthylg ly{}ximc; c) G H 2 = { ; lyox ime .

214 G. Gupta, R. Shaxan and R. N. Kapoor

Table 3. I.r. frequencies (cm -1) for the zirconium complexes

Transition Met. Chem. 3, 211-214 (1978)

Complexes v(Oll) v(C-It) u(C-C) 6i.p.(CH) 6o.p.(CH) v(C=N) v(N- O) v(C-O) b (C-H) b ( N - O )

Cp2 ZrCI2 C ~2 Zr(SOx) C ~2 Zr(AOx) C )2 Zr(POx) C )2 Zr(B'Ox) C ~2Zr(BOx) C )2 Zr(DPGH)CI C )2Zr(DPGH) 2 C )2 Zr(DMGH)CI C 32 Zr(DMBH)2 Cp2Zr(GH)CI CpZr(GH)2

- 3100s 1435s 1020m - 2990mb 1442s lO14b - 2960m 1460m 1025mb - 2950s 1400s 1015m - 3010m 1435s lO18m - 3000s 1450b 1020b 3450mb 3000m 1435s 1020mb 3250s 3005m 14-40s 1030mb 3200b 30lOmb 1440m lO10m 3200b 2950mb 1435b 1005b 3 1 6 O b 2940mb 1440b 1015s 3190b 3000mb 1435m lO18mb

820mb - - - 805b 1592s 1205s, 920s 1290mb 818m 160Ore 1190m, 965m 1295s 80Omb 1575m 12lOre, 960s 1295s 800rob 1575mb 119Ore, 970b 1260s 800rob 1570m 120Ore, 980m 1300s 800mb 1570s 1190m, 925m 1260s 803rob 1580m 1225b, 920m 1265s 800rob 15 lOb 1220b, 960b 1260s 805m 1535b l180b, 980s 1265b 800m 1560mb 1170b, 925b 1260s 800b 1570b l170b, 990mb 1255b

complexes given in Table 1 but is retained in others (Table 2), where it appears as a broad band due to the inter-

molecular and intramolecular hydrogen bonding. The non- conjugated v(C=N) normally appears in the 1 6 9 0 - 1 6 5 0 cm - l range (21), the conjugat ion causing a shift to the lower f requency at ca. 1630 cm -1 for the Schiff 's bases (22). In all ke toximes and salicylaldoxime, the sharp peaks at c~ 1625 cm - l and ca, 1612 cm -1 are due to ~i(OH), but these bands disappear in the complexes. The broad medium band at c~ 1600 cm -1 due to u(C=N) in oximes, shifts to lower f requency ca. 1555 c m - l in the complexes, Similar observa- t ions were also made by Biradar et al. (23). The lowering of the v(C=N) f requency indicates that the C=N bond order decreases and that the N a tom coordina tes to zirconium. The large v(C=N) shift f rom the normal value of 1600 cm - t to 1555 cm - l appears to be due to resonance, conjugat ion or coupling with C=C and with hydrogen bonds (23)

A broad med ium intensity band at c~ 1280 cm -1 in the ligand is probably due to u ( C - O ) phenolic, 8 ( C - H ) and 8 ( N - O ) vibrations (23). The bands in the 1 2 3 5 - 1 1 9 0 cm -~

and 9 8 0 - 9 3 5 cm - j regions in the complexes are a t t r ibuted to a u ( N - O ) vibration. For dioximes, the N - O bonds are probably unequal because of their d i f ferent N--O linkages. The various bands in the b isd imethylg lyoximate are a lmost at identical posit ions to those of nickel and palladium d imethylg lyoxime complexes , indicating close structural similarity. The hydrogen bond involved in the dimethylgly- oximate complex is not of symmetr ical type as suggested by splitting of - O H bands.

F o r Z r l V p y r r o l c o m ~ l ~ x e s , the band at ca 5 5 0 c m -l

is assigned to v ( Z r - N ) t ), similarly the band at ca~ 480 cm-1 is due to v ( Z r - O ) (25). Thus the bands in the 5 7 0 - 5 3 0 cm - l and 5 2 0 - 4 2 0 cm - l regions in the complexes can be as- signed to v ( Z r - N ) and v ( Z r - O ) , respectively.

Electronic Spectra

The electronic spectra of all complexes, recorded in ch loroform and in nujol, show a single band in the 2 4 7 5 0 - 24380 cm - l region, which can be assigned to the charge transfer band (26) and is in accord with their i n - l ) d ° , ns ° electronic configurations.

A c k n o w l e d g e m e n t

Two of the authors (G.G.) and (R.S.) thank the Council of Scientif ic and Industrial Research, New Delhi, for the award of Junior Research Fellowships.

References

(I) R. C. Mehrotra, A. K. Rai, A. Singh and R. Bohra, lnorg. Chitr~ Acta Revs, 13, 91 (1975).

(2) D. C. Bradley, R. C. Mehrotra and W. Wardlaw, J. Chem. Soc., 5020 (1952).

(3) R. C. Mehrotra, lnorg. Chin, Acta R~ws., 199 (1967). (4) D. C. Bradley, Progr. lnorg. Chem., 2, 303 (1961). (5) A. Singh, A. K. Rai and R. C. Mehrotra, lnorg. Cbim. Acta, 7,

450 (1973). (6) A. Singh, (Miss) C. K. Sharma, A. K. Rai, V. D. Gupta and

R. C. Mehrotra. J. Chem. Soc. A, 2440 (1971). (7) R. Bohra, A. K. Rai and R. C. Mehrotra, Indian J. CbenL, 12,

855 (1974). (8) R. C. Mehrotra, A. K. Rai and R. Bohra, Z. Anorg., Allgem.

Chem., 399, 338 (1973). (9) S. Prakash, Pb. D. thesis, University of Dclhi (1970).

(10) A. I. Vogel, A Text Book o f Practical Organic Cbemisto~, l,ongman Green, London, 1948.

(11) W. 1.. Jolly, Synthetic Inorganic Chemistr% Prentice ttall of India (Private) Ltd., New Delhi, 1965, p. 176.

(12) G. Wilkinson andJ. M. Birmingham,./. Am. Chem. Soc., 76, 4281 (1954).

(13) H. K6pf, J, Organometal Cbet~, 14, 353 (1968). (14) H. K6pf, Z. Natur]orscb., B, 23, 1531 (1968). (15) P. Prashar and J. P. Tandon, Z. Anorg., Allgem. CbetrL, 383,

81 (1971). (16) P. Prashar and J. p. Tandon, J. Less Common Mets., 15, 219 (1968). (17) P. C. Wailes and H. Weigold, J. Organometal Chem., 24, 413

(1970). (18) P. Pfeiferand J. Richarz, Chem. Bet., 61, 103 (1928). (19) O. Brady and M. M. Muers, J. Chem. Soc., 1599 (1930). (20) H. P. Fritz, Advan. Organornetal. Cbem, 1, 262 (1964). (21) C. N. R. Rao, Chemical Applications o f lnJ~ared spectroscopy,

Academic Press, New Vork, 1967. (22) C. S. Marvel, S. A. Aspey and E. A. Dudley, J. A~r~ Chem. Soc.,

78, 4905 (1956). (23) N. S. Biradar and V. B. Mah',dc, .I, Less Comm.n htets., 31,

159 (1973). (24) K. Issleib, and G. Biitz, Z. Anorg. Allgent. Chem., 369, 83 (1969). (25) D. R. (',ray and C. It. Brubaker, lnorg. Chem., 10, 2143 (1971). (26) P. B. Dorain, H. H. Patterson and P. C. Jordon, J. ChenL Phys.,

49, 3845 (1968).

TMC 7 8/4