INDIAN J. CHEM., VOL. 16A, NOVEMBER 1978

Synthesis of Some Novel Bromo Complexesof Molybdenum Containing Mixed Ligands

DHRUVA N. PATHAK

Department of Chemistry. M.L. K. CollegeBalrampur 271201

Received 16 January 1978; accepted 24 111arch 1978

Reaction of large excess of bromine with Mo(CO)3(L-L) (Am) (where L-L=O-phen or 2.2'-bipy andAm = butylamine. rr-hexylamlna, cyclohexylamlne,benzylamlne, piperidine or morphollne) yield para-magnetic complexes. (L-L) (Am) MoBr.. of hepta-coordinated Mo(IV). Their formation has beeninterred on the basis of IR spectra. conductivity data,magnetic measurement and elemental analysis.

A NUMBER of hexa-coordinated halogeno com-plexe.s of g~oup VI metals have been reportedl-6,

but relatlve~y little attention has been paid'' to theirhepta-coordmated derivatives. In continuation ofOur previous studies? on bromine oxidation ofmixed amine molybdenum tricarbonyls, some newseven-coordinated complexes of the type (L-L)(Am)MoBr. (where L...L = o-phenanthroline or2,2'-bipyridyl.and Am = butylamine, n-hexylamine,eyclohexylamme, benzylamine, piperidine or mor-pholine) are being reported here.

All the reactions were performed under an inertat!ll0sphere of nitrogen. Mixed aminemolybdenumtncarbonyls were synthesized by known methods''.

p'reparation of tetrabromo-o-phenanthroline(butyl-am7n~)molybdenu~(IV) - A suspension of o-phenan-!hroh~e(butylamme)tricarbonylmolybdenum (0)(0,1 g)in a httle benzene was treated with a large excessof bromine solution (0·5 g in 15 ml benzene) atambIent temperature under dry nitrogen with con-stant stirring. The black colour of the solid

carbonyl turned greenish yellow with the dischargeof bromine colour. Addition of more bromineresulted in effervescences of carbon monoxide;greenish yellow product changed to orange and finallydissolved. Effervescence completely ceased after1 hr, stirring was stopped and solid material wasseparated by filtration. Orange filtrate was pouredinto excess hexane (60 ml) when an orange-redcompound precipitated. It was filtered off andwashed with hexane to remove traces of bromine(if any). The residue was dried in vacuo. Analyticaldata showed it to be tetrabromo-o-phenanthroline(butylamine)molybdenum(IV); yield, 35 %.

Other (L-L)(Am)MoBr4 derivatives were similarlysynthesized in •...•..30% yields. Colour, and ana-lytical data of the derivatives are given in Table 1.

Reaction of a large excess of bromine with Mo(CO)3(L-L)(Am) yielded complexes of the type (L-L)(Am)MoBr4' The complexes are orange to redcrystalline solids, insoluble in aliphatic hydro-carbons and light petroleum but soluble in aromatichydrocarbons and polar solvents. On _heating insealed capillary tubes, they first converted togreyish yellow (unidentified) products which onfurther heating decomposed to black masses at hightemperature. The complexes are stable in nitrogenatmosphere but they slowly decompose on exposureto air or in solutions giving sticky masses.

IR spectra (4000-1200 crrr" in K.Br) of (o-phen)(Am)MoBr4 compounds exhibit bands due to N-Hstretching and deformation modes (due to amine)around 3360-3340 m(br), and 1630 (s), 1575 (s) crrr"respectively. Characteristic bands of o-phenan-throline" were observed around 1610 (sh), 1596 (s),1550 (w), 1490 (s), 1424 (vs) and 1340 (m) .ern-l. ~oband was observed in the CoO stretching regionindicating the complete displacement of CO groupsduring excessive brominr tion of Mo(CO)3(o-pl:en)(Am) derivatives. In the IR spectra of (2,2'-bipy)

TABLE 1 - COLOUR AND ANALYTICAL DATA OF THE COMPLEXES

Complexes Colour Found (Calc.), (%)C H N Br

(Cl>H.N.) (C4H~NH.)MoBr4 Orange 28·0 2-9 6·0 47·1(28'6) (2-8) (6'2) (47'8)

(C12H.X.) (CeH13NH.)MoBr. Orange-red 30'2 3·3 5·8 45·3(30'9) (3-2) (6'0) (45·9)

(C11H.X.) (CeHll XH.) MoBr. Orange 30·3 3'0 5'7 45·1(31'0) (3'0) (6'0) (46'0)

(C12H8X,)(CeH5CH.KH.)MoBr. Orange-red 31·9 2·4 5·7 44·8(32-4) (2-4) (5'9) (45'5)

(C12H8X5) (C5Hll X)MoBr. do 29'4 2·8 6·0 46·1(29,9) (2'7) (6'1) (46'9)

(C12H.X.) (C.H.-!\O)MoBr. Orange 46·1(46'8)

(C,oH8X2) (C.H.XH2)MoBr4 Red 25-4 2·8 6'3 48-9(26'0) (2'9) (6'5) (49-4)

(C1oH.XI) (CeH13KH.)MoBr. Orange-red 28'3 3·6 6·1 47·0(28'5) (3-4) (6'2) (47'5)

(C,oH8X.) (CeHllKH.) MoBr. Orange 28'1 3·2 6'1 47·3(28'6) (3'1 ) (6·2) 47·6

(C1oH8N.)(CeH5CH.XH.) MoBr4 do 46·4(47'1)

(C1oH8X.)(C5HllK) MoBr. Orange-red 27·2 2·8 6·1 48·0(27,3) (2-8) (6·3) (48'5)

(ClOH8K.)(C.H~NO)MoBr4 Orange 47'6(48'5)

986

(Am)MoBr(, bands z round 3378-3360 s(br) and 1608{m), 1560 (fns) crrr? are observed which may beattributed to NH stretching and deformation modes.Bands around 1595 (vs), 1565 (sh), 1435 (vs) arid1260 (m) em"! may be <. ttributed to char-.cteristicvibrations of 2,2-bipyridylu. Absence of bands inthe C-O stretching region confirmed the replace-ment of all the carbonyl groups.

All the complexes a re non-electrolytes in benzene(molar conductance < 1 mole+ ohm-l cm-), Megneticmoments (Faraday's method) of the derivativeslie in the range 2·52-2·77 BM at room temperaturewhich indicates their paramagnetic nature similarto that of seven-coordina ted phosphine complexesof the type (PMe2Ph)3MX4 (where M = Mo, WandX = Cl, Br) reported earlier".

Attempts to synthesize similar iodo complexes re-suited in the production of greenish black masses whichcould not be identified due to their sticky nature.

The author thanks Dr P. P. Singh, M.L.K.College, Balrampur, for his constructive suggestions.Facilities provided by Prof. R. P. Rastogi andDr S. C. Tripathi, Chemistry Department, Universityof Gorakhpur, are gratefully acknowledged.

References1. XIGAM, H. L., NYHOLM, R. S. & STlDDARD, M. H. B.,

}. chem. Soc., (1960), 1806.2. LEWIS, J., l'\YHOLM, R. S., PANDE, C. S. & STlDDARD,

~f. H. B., j. chem . Soc., (1963), 3600.3. LEWIS, J., l'\HYOLM, R. S., PAKDE, C. S., SANDHU, S. S. &

STlDDARD, M. H. B., J. (hem. Sac., (1964), 3009.4. COOK, C. D., l'\YHOLM, R. S. & TOBE, M. L., 1. (hem.

Soc., (1965), 4194.5 DJORDJEv'IC, C., NYHOLM, R. S., PANDE, C. S. & STlDDARD,

1\1. H. B., 1. chem. Soc. A, (1966), 16.6. Moss, ]. R. & SHAW, B. L.,}. cheni, Sac. A, (1970),595.7. PATHAK, D. N., Indian 1. Chem., 16A (1978), 158.8. TRIPATHI, S. C. & SRIVASTAVA, S. C., J. organometal.

ClleYl/.,25 (1970), 193.9. SCHILT, A. A. & TAYLOR, R. c., 1. inorg. nucl, Chenr., 9

(1959), 211.

Chelates of Niobium(V) & Tantalum(V)Phenoxides with Benzoin

K. C. MALHOTRA, U. K. B.\NERJEE & S. C. CHAUDHRY

Department of Chemistry, Himachal Pradesh UniversitySimla 171005

Received 11 April 1978; accepted 16 May 1978

Compounds of composition M(OC.H.)4.Benz; MCI(OC.H')3.Benz and MCI.(OC.H5) s-Benz (where M = Nb,Ta; BenzH = Benzoin) have been prepared by reflux-ing M(OC.H')5' MCI.(OC.H')3 and MCI3(OC.H.). withbenzoin in 1 : 1 molar ratio in benzene. From elementalanalysis, molar conductance, magnetic susceptibilityand IR spectral studies their structures have beenproposed. •

BENZOIN forms a variety of complexes withLewis acidst+, Niobium(V) and tantalum(V)

alkoxy compounds containing (?-diketones and otherrelated ligands of composition M(OC2H5)4.L;M(OC2Hs)3·L2 and M(OC2Hslz.L3 where L is benzoyl-acetones, ethyl benzoylacetate", methyl acetoacetate''and ethyl acetoacetate have been isolated. The

NOTES

corresponding acetylacctone complexes are alsoknowns. Recently Syamal and coworkers" havereported the coordination compounds of Nb(V)and Ta(V) chloroalkoxides with similar ligands.Prakash and Kapoor!" and Schonherr et at.ll haveisolated phenoxides and chlorophenoxides of Nb(V)and Ta(V). The latter have also reported theadducts of these phenoxides with methyl cyanidesand triethyl ammonium derivatives. In this notewe have investigated the Lewis acid character ofNb(V) and Ta(V) phenoxides and chlorophenoxidesby isolating their chelates with benzoin.

Niobium and tantalum pentaphenoxides andchlorophenoxides, viz. ;,\1:(OC6H5)5; ;\'ICI(OC6H5l(;MCI2(OC6Hs)3 and MCI3(OC6H5h were prepared bythe method reported in literaturev'-!". Benzoin(BenzH) (E. Merck) was purified by crystallizationfrom hot benzene (m.p. 137"). Compounds ofcomposition M(OC6Hs)4·Benz; MCl(OCsH5)3.Ben-zoin and MCI2(OC6H5hBenz were prepared byrefluxing M(OC6HS)Sor MCl(OC6Hs)( with benzoin in1:1 molar ratio in benzene for M(OC6Hs)(.Benzand for the rest two by refluxing MCI2(OCeHshand MCI3(OC6H5h with benzoin in 1: 1 molar ratioin benzene. The reactions were carried till therewas no more evolution of hydrogen chloride gas[except in the case of M(OC6Hs)5]. The compoundM(OC6Hs),.Benz was isolated by decanting benzene,washing with petroleum ether and dried in vacuo.In the case of MCI(OCsH5hBenz and MC12(OC.Hsh.Benz petroleum ether was added to extract thecompounds and then evaporating in vacuo.

Elemental analysis and physical constants are givenin Table 1. Except M(OCeHs)4.Benz, the rest arefairly soluble in nitrobenzene. Molar conductancevalues (1·21-3·0 ohrrr+ cm-2 mole-') of the millimolarsolutions in nitrobenzene suggest them to be non-electrolytes.

The "CO· of benzoin appearing at 1690 is loweredby 40-60 in the spectra of the complexes of thesephenoxides with benzoin, due to the coordinationof carbonyl group of the ligand to the central metal.The vO-H generally observed at 3360 in pure ben-zoin disappeared in the complexes. This is supportedby the observation that hydrogen chloride gas wasevolved during the reaction of chlorophenoxideswith benzoin and that phenol could be isolated fromthe filtrate of the complexes prepared from penta-phenoxides. However, no attempt was made forthe quantitative estimation of phenol. It suggeststhat M-CI bond is weaker than M-O bond and thedimeric structure of the compound is ruptured. Itis also observed that vO-C originally present at 1094in pure benzoin is lowered by 50-60 in these com-plexes, indicating that oxygen of the hydroxylgroup is attached to metal ion. Similar observationshave been made in case of complexes of penta-chlorides of niobium and tantalum with benzoint-,No such band which could be assigned to bridgingM-O~M bonds except the one around 470 in thecase of niobium phenoxide adducts and around 572in the case of tantalum phenoxide adducts assignedto IR active v(M-O) are observed in these com-plexes. These bands are in the same region asreported earlier in Iiteraturew. No band that could

*IR vmax throughout the paper in cm+,

987