Indian Journal of ChemistryVol. 22A. October 1983. pp. 871-874

Reactions of Bls(acetylacetonato cis-cllOxo)moiyhdenum l) wlthAroylhydrazines, Arylamines & Aroylhydrazone Schiff Bases

RLDUTTA*&AKPALDepartment of Chemistry, University of Burdwan, Burdwan 713104

Received 15 February 1983; revised and accepted 21 June 1983

Bis(acetylacetonatoXcis-dioxo)molybdenum(VI} (A) reacts with benzoylhydrazine in dry methanol to give-red crystals of(benzoyldiazinoXbenzoylhydrazidoXacetylacetonato)molybdenum(VI). The same reaction, when conducted in ordinarymethanol or acetone provides light-yellow cyrstals of (acetylacetonatoXcis-dioxo)molybdenum(VI)-/l-diol-{ben:iIOylhydr-azinoXcis-dioxo)molybdenum(Vl) dihydrate. Reaction of salicyloylhydrazine in dry methanol gives deep-red crystals of(salicyloyldiazinoXsalicyloylhydrazido)molybdenum(Vl)-/l-diol-(salicyloyldiazinoXsalicyloylhydrazido)molybdenum(VI).Reaction of (A) with aniline in ordinary methanol provides greenish yellow crystals of (acetylacetonato)(cis-dioxo)molybdenum(Vl)-jl-diol-{acetylacetonatoanil)(cis-dioxo)molybdenum(VI) monohydrate. A similar yellow colouredproduct is obtained with benzidine. Reaction of (A) with salicylidene-benzoylhydrazine leads to orange-yellow crystals of(salicylidene-benzoylhydrazinoXcis-dioxoXmonoaquo)molybdenum(VI). A similar product is obtained with 5,6-benzosalicylidene salicyloylhydrazine. The quadridentate schiff base bis(benzamido)acetylacetoneimine gives dark-redcrystals of bis(benzamidato)acetylacetoneimine(cis-dioxo)molybdenum(VI).

•

We have recently reported some reactions ofbis(acetylacetonato)oxovanadium(IV) with aroyl- andheteroaroyl-hydrazines in a variety of solvents 1. It wasobserved that the solvents played a key role in theretention or abstraction of the vanadyl-oxa bonds,thus giving products of different types. In view of thefact that the second and third row transition metalshave a strong tendency to form multiple bonds, it wasthought worthwhile to study the reactions ofbis(acetylacetonatoXcis-dioxo)molybdenum(VI) witharoylhydrazines, arylamines and aroyl hydrazoneschiff bases.

Chatt and coworkers" have recently reported someinteresting reactions of bistdithiocarbamato'(dioxo-)molybdenum(VI) with a series of substitutedhydrazines. We report here the preparation andcharacterisation of following compounds: (I)(benzoyldiazino) (benzoylhydrazido) (acetylacetonato)molybdenum(V I)(red); (2)(acetylacetonato) (cis-dioxo)mo I ybden um( V 1)- p-dio I-(benzoyl h ydrazi no)molybdenum(VI) dihydrate (light-yellow); (3) (sali-cyloyldiazino) (salicyloylhydrazido) molybdenum(VI)-p-diol-(salicyloyldiazino) (salicyloylhydrazido)molybdenumt Vl) (deed-red); (4) (acetylacetonato) (cis-dioxo) molybednum(VI)-p-diol-(acetylacetonatoanil)(czv-dioxo) molybdenum(VI) monohydrate (greenish-yellow); (5) (acetylacetonato) (cis-dioxo)molybdenum(V I)-p-diol (acetylacetonatobenzidine)(cis-dioxo) molybdenum(VI) yellow; (6) (salicylidene-benzoylhydrazino) (cis-dioxo) (monoaquo)molybdenum(VI); (7) (5,6-benzosalicylidene-salicyloylhydrazino) (cis-dioxo) (monoaquo)molybdenum(VI) (red); and (8) bis(benzamidato)

(acetylacetoneimino) (czs-dioxo) molybdenum(VI)(dark-red).

Materials and MethodsBis(acetylacetonato)(cis-dioxo)molybdenum(VI)3,

benzoylhydrazine", salicyloylhydrazine'', salicylidene-benzoylhydrazine", 5,6-benzosalicylidene-salicyloyl-hydrazine" and bis(benzamido)acetylacetoneimine 7

were prepared following published procedures.

Preparation of compounds (1) & (2)(cis)-MoOiacac)2 (0.002 mol, 0.652 g) was dissolved

in dry G R grade methanol (10 ml) and mixed with asolution ofbenzoylhydrazine (0.004 mol, 0.544 g) in 10ml of the same solvent. The solution was refluxed for20 min. The crude crystals were filtered and dissolvedin refluxing methanol (80 ml) and the solution obtainedthus deposited red shining crystals of compound I.Compound 2 was obtained similarly using ordinarymethanol or acetone. This compound could not berecrystallized.

Preparation of compound (3)This was obtained ~ following the procedure of

compound (1) using salicyloylhydrazine instead ofbenzoylhydrazine. The compound could not berecrystallized.

Preparation of compounds (4) & (5)(cis-)-MoOz{acac)2 (0.001 mol, 0.32 g) in ordinary

methanol (10 ml)and 2 ml aniline or benzidine (0.001mol, 0.184 g) in 25 ml of the same solvent were mixedtogether and refluxed for 45 min when yellow crystalsseparated out.

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INDIAN J. CHEM., VOL. 22A, OCTOBER i'983

Preparation of compounds (6), (7) & (8)(cis)-MoOlacach in ordinary methanol was taken

as usual. The appropriate schiff base (0.001 mol) wasdissolved in the same solvent (20-40 ml). On mixing thetwo solutions and refiuxing, orange-yeuow to dark-redcrystals separated out.. All the compounds werewashed with appropriate solvents and dried in vacuoover silica gel.

Analysis and other physical measurementsNitrogen was estimated by the combustion

technique. Carbon and hydrogen were determined atCDRI, Lucknow. The complexes were decomposed byfuming with cone. HN03 (3 ml) and cone. H2S04 (4ml). After dilution and adjustment of acidity,molybdenum(VI) was precipitated by 8-hydroxy-quinoline, filtered, dried and weighed. The latticewater of compounds 2 and 4 was determined at 1200

while a thermogram was run for compound 6 on aShimadzu Instrument. Magnetic susceptibilities weredetermined using a Gouy balance.

The infrared spectra were recorded on a BeckmanAcculab 10 spectrophotometer in KBr.

Results and DiscussionAll the compounds were found to be diamagnetic as

expected for molybdenum(VI). The electronic spectraof compounds (I), (3) and (6) in anhydrous methanol at0.00002 M, 0.00005 M and 0.0002M concentrationsrespectively gave bands with molar extinction'coefficients of 15000 (A = 410 nm), 15000 (A = 420 nm)and 3750 (A = 420 nm) respectively. Beyond 500 nm,optical density values were extermely low and therewas no evidence of any d-d transition over the visiblerange. Thus, the magnetic measurements along withelectronic spectral data leave little doubt that thecomplexes are genuine molybdenum(VI) species ratherthan molybdenum(V).

The complexes may be considered to belong to twodifferent classes: compounds(l), (6), (7) and (8)have nohydroxo bridge while the compounds (2),(3), (4) and (5)have hydroxo bridges. It is reported in the literature"that a slightly higher pH (above 6.5) tends to favour theformation of hydroxo bridge in the case ofdioxouranium(VI) complexes. Addition of aniline,benzidine and benzoylhydrazine to ordinary methanolor acetone raises the pH favouring the formation ofhydroxo bridges. It is also important to note thatacetone is somewhat less basic than methanol". It is,therefore, likely that anhydrous methanol favoursenolisation of benzoylhydrazine and also removal ofwater (through condensation of the hydrazineNH2 with the molybdenyl oxygens) leading to theformation of compound (1). Our earlier work 1 on theabstraction and retention of vanadyl-oxygen bond of

872

bis(acetylacetonato)oxovanadium(IV) complex withbenzoylhydrazine and related ligands in anhydrousmethanol and acetone respectively also supports thetwo different modes of reaction. Furthermore,formation of com~ounds\ 6),(1)and ,'&) V\'<ln~'<lct\o\\~o~MoOlacach with a tridentate or a quadridentateschiff base leads to removal of both the acetylac-etonato groups with the retention of the cis-dioxobonds. This observation is in agreement with a recentstudy of Rajan and Chakravorty '".

During these synthetic studies, partial or totalremoval of the coordinated acetylacetonato groupswas observed. Though it was not possible to followquantitatively the release of acetylacetone, we didisolate bis(acetylacetonato)copper(II) in pure con-dition from the filtrate of the preparations except forreactions involved in the synthesis of(3) and (4).To citethe best case, after isolation of compound (8), thefiltrate was treated with copper(II) acetate mono-hydrate. The blue precipitate contaminated with alittle green product [presumably a schiff base complexof copper(II)] was dissolved in the minimum amountof methanol and pure bis(acetylacetonato)copper(II)was isolated after removal of the solvent and finallydried and weighed. In this particular case 80-90%recovery of released acetylacetone was achieved. Forcompounds (I), (2), (5), (6) and (7), recovery was 50%,80%,45%, 85% and 30% respectively.

Assignment of structures to the compounds (Fig. 1)is based on their analytical data (Table 1)and infraredspectra. Insolubility of the compounds restrictedprobing of the structures by other techniques.

Compound (l)-(BenzoyldiazinoXbenzoylhydra-zido.xacetylacetonato}molybdenum(VI), exhibits vC=0 at 1580cm -1. This mode is exhibited in the sameposition by (cis)-MoOiacach vNH mode is observedat 3150cm -1, while the deformation mode of NH2 isobserved at 1170cm -1. vC=N appears at 1550cm -1.

The cis-molybdenyl (Mo02) bands 11 expected at 890and 920cm -1 (shoulder) are completely absent in thiscompound. The literature does not record any straightforward assignment of Mo = N bond". These infrareddata are consistent with the structure proposed for thecompound (I) (Fig. I).

Compound (2)- The water molecules in(acetylacetonatoXcis-dioxo)molybdenum(VI)-li-diol-(benzoylhYdrazino)molybdenum(VI) dihydrate canbe easily removed by heating around 120cC. Thisindicates that these are lattice-bound. Coordinatednature of acetylacetonato group is revealed by a vC= 0 band appearing at 1580 em -1. l'C = N appears at1550em -1 while I'Mo02 exhibits bands at 880 and 920ern -1 (shoulder). A broad and strong band centredaround 3150cm -1 is due to overlapping of I'N - Hand1'0H modes. Unambiguous assignment of li-diol

~I

iI,

DUTrA & PAL: Mo(VI) COMPLEXES

Table I-Characterisation Data of Products Obtained from the Reaction of MoOiacach with DifferentAroylhydrazines, Arylamines and Aroylhydrazone Schiff Bases

Compound Reaction medium Reactants Found (Calc.), %No.

Mo N C H

Dry methanol Mo02(acac),: BH 20.5 12.0 49.6 3.6(I : 2) (20.7) (12.1) (49.4) (3.8)

2 Methanol/acetone Mo02(acach: BH 34.4 5.0 25.7 3.5

(ordinary) (I : 2) (34.3) (5.0) (25.7) (3.6)3 Dry methanol Mo02(acac), : SH 24.1 13.1 39.6 3.1

(I: 2) (23.3) (13.6) (40.8) (2.9)4 Methanol MoO,(acach aniline 33.5 2.9 32.5 3.6

(ordinary) (I: 2) (33.0) (2.4) (33.0) (4.0)5 Methanol Mo02(acac)2 : Benzidine 30.0 4.4 40.0 3.6

(ordinary) (I : I) (293) (4.3) (40.4) (3.9)6 Methanol MoO,(acac)2 SalHBH 24.2 7.2 44.4 2.9

(ordinary) (I : I) (25.0) (7.2) (43.8) (3.1)7 Methanol MoO,(acac), naphthHSH 20.9 6.1 48.4 3.3

(ordinary) (I : I) (213) (6.2) (48.0) (3.1)8 Methanol MoO,(acac)2: acac(BH), 20.5 12.5 50.7 4.0

(ordinary) (I : I) (20.7) (\2.1) (49.2) (3.9)

acacH = acetyl acetone; SalHBH = salicylidene-benzoylhydrazine; BH = benzoylhydrazine; naphthHSH = naphthylidene-salicyloylhydrazine: SH = salicyloylhydrazine; acac(BH), = bis(benzamide)acetylacetoneimine.

2

5 6 7

0-0:: anion of c cetytccetor-e •0 -N= ocptyloct"tont"onll,O -N- C6HI.-C6Hl.- NH2=

anion of mon ot cc e tyiocetone -be-nZ1dmE1',O-N -0:: d.":'"Ior :)f SCIICY'10t"nE'-

benzoylhydrazonf' "'r S,6-bpnzosol C/"df'nf'-sal,cylo)'lhydrozonp, ')-N-N-Q=dlOnlon of bls( oenzo re.oo) ccetvtc cetonermme

bridge is not possible because of the appearance of thebands due to benzoylhydrazine in the region reportedfor bridging OH(900-1120 em 1)12. However, ouranalytical data strongly support a dimeric sturcture (2)(Fig. I).

Compound 3- This compound appears to be adimer from the reaction of MoOz<acach and

salicyloylhydrazine in dry methanol. Coordination ofsalicyloylhydrazido /51UUP LV uiotybuenum throughthe keto oxygen is evident from the presence of a verystrong vC = a at 1600 em -I. The ligand salicyloyl-hydrazine shows the keto band at 1650 em -I. Thepresence of coordinated salicyloyldiazino group isindicated by the presence of a strong vC = N at 1560ern -I. A composite broad band centered around 3200em -I is assigned to vN - H + vOH. That the phenolicOH is not linked to molybdenum is indicated by non-shifting 1

3 of vC - a from its original position at 1240cm -I. vMo02 bands of MoOz{acac)2 are completelyabsent in the IR spectrum. Although compounds Iand3 have been obtained under similar reactionconditions, they differ significantly in their nature.Probably the formation of the two different types ofcompounds is influenced by a wide difference insolubilities.

Compounds 4 & 5-Compound 4 exhibitscharacteristic bands for vMo02 at 890 and 930 em -I

(shoulder). vC = a and vC = N appear around 1590and 1530 em -r l respectively. The vC=N obviouslyindicates schiff base formation between coordinatedacetylacetone and aniline. Compound 5 givescharacteristic bands at 880 and 920 em -I (shoulder)due to vMo02, at 1600 due to vC=O of coordinatedacetylacetonato group and at 1550 em -I (sh) due to vC= N. Bands at 3000, 3200 and 3300 em -r- l may be takento be due to - NH2 and J1-0H groups. It appears thatschiff base formation with acetylacetone occurs at onlyone of the two - NH2 groups of benzidine.

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INDIAN J. CHEM., VOL. 22A, OCTOBER 1983

Compounds 6 & 7-Compound 6 gives vMo02 at 900and 940 em -1. Besides, there is a strong, sharp band!"due to >C = N - N = C < moiety at 1600 em -1.

Coordinated phenolic vC - 0 appears 13 at 1270 em -1

while in the free ligand, salicylidene-benzoylhydrazine,this band appears at 1240 em -1. The thermogram ofthis complex shows that the coordinated watermolecule is slowly lost over the range 100-180aC.Compound 7 registers vMo02 at 900 and 940 em -1

(shoulder), v > C = N - N = C < at 1600 em -1, andphenolic vC - 0 at 1340em -1. For the free ligand 5,6-benzosalicylidene-salicyloylhydrazinel5 phenolic vC-0 band appears at 1310 em -1.

Compound 8- The molybdenyl bands appear at 900and 940 cm -1 (shoulder). The vC = 0 band 7 of the freeligand at 1660 em -1 disappears while the vC = N at1605 em -1 is lowered to 1530 em -1. The ligandbis(benzamido)aeetylacetoneimine is coordinated tomolybdenum(VI) as a quadridentate dibasie(O N N 0)donor in its deprotonated enol form.

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