.,

Indian Journal of Chemistry Vol. 38A, December 1999, pp. 1209-121 8

Synthesis, characterization and spectroscopic studies of homo- and hetero-Ieptic glycolates of alkaline earth metals, and tin (II) with aluminium

Malti Sharma", Anirudh Singh* & Ram C. Mehrotra*

Department of Chemistry, University of Rajasthan,

Jaipur 302 004, India

Received 14 August 1998; revised 13 JLlne 1999

The reactions of HAI (O-G-O\ with alkaline earth me!als (Mg, Ca, Sr, 8 a) and those of AI (OPr'\ wit h H 2~)2 (M = Mg, Ca , Sr, 8 a, Sn(II ); G = -CMe

2.CH2.CHMe-) in 2: I molar ratio yield derivatives of the types M{AI (O-G-O),} ,

~ --and {AI(OPr\ l; {M(O.-G-O\ l , respecti ve ly. An allerna tive rout e to prepare the above homo- and hetero- Ieptic derivati ves is

to react M {AI(OPr\ l2 with hexylene glycol in 1:4 and 1:2 mol ar ratios , respectivel y, in benzene . All these derivati ves have

been characte ri zed by elemental analyses , spectroscopic [IR and NMR CH, IJC, 27 AI and II"Sn)] studies, and molecular weight

measurements.

Homometallic g lycolate de rivatives synthesized previously in our laboratories I have shown interesting variation in their properties and structural features . In general , the chelating ligands such as ~arboxylic

acids2, ~-diketones\ glycols4, and alkanolamines5

have played a significant role in modifying6 the solubility and reactivity of the resulting alkoxide derivatives to make them better suited to form homogenous gels during hydrolysis . It may be mentioned that sterically compact alkoxides of bivalent metals are generally polymeric, non-vol atile , and insoluble in organic solvents. Special attention has been focussed on these during the last decade in view of the important role of some (e.g., Ba and Cu) of these in the preparation of superconducting oxide materials.?

In continuation of our earlier investigations on the preparation of hydrocarbon solubl e monomeric derivatives of alkaline earth metals. we have now synthesized novel heterobi meta llic glycolate derivatives of the types, M {AI(O-G-O)o} 0' and {AI(OPr i

)} ,. _ _ 2 2

{M(O-G-O)2} by two different routes. In thi s context, 2-methylpenlane-2,4-diol (hexylene glycol) has played a crucial role in making accessabi lity of homomelall ic glycol derivatives having facil e protons as reactive centres for other metals and metal alkoxides leading to the formation of novel heterobimetallic glycolate systems.

We report in th is paper preparation and characterization of novel homo- and hetcro-Ieptic

"Nee Malti 8hagat

heterobimetallic glycolate deri vatives , with attracti ve features, that can be used as precursors for the synthesis of ultrahomogenous ceramic materials .

Materials and Methods All operations were carried out under moisture­

free environment. Benzene (BOH), isopropyl alcohol (BOH), l1-hexane (BOH) and toluene (BOH) were carefully dried and distilled before use. AI(OPr')j (ref.8) , and M(OPr\ (ref.9) (where M = Mg, Ca, Sr, Ba), M {Al(OPri\} 2 (ref. I 0) were prepared by literature methods. Sn(OPri)2 was prepared by I : 2 molar reaction of SnClo and KOPri in C H , followed by _ 6 6

fi ltration and removal of volati les under reduced pressure and analyzed (Calc. for Sn(OPri)o : Sn , 50. 11 %. Found: Sn, 50.08 %) . 2-Methylpenta-ne-2,4-dio l (hexylene glycol ) was purified by distillation at 19]DC1760 mm.

Barium, strontium, and aluminium were estimated gravimetrica lly as barium sulphate, stront ium sulphate, and aluminium oxinate l l

. Magnesium and calcium were estimated volumetrically by complexometric titration with EOTNI . Isopropyl alcohol in the azeotrope was estimated oxidimetrica lly using a 1 N K2Crp? solution in 12.5 % H

2S0

4 ac id 12

. The above method was standard ized (with an accuracy of ±0 .5%) for the estimation of 2-methy lpentane -2,4-diol also.

Infrared spect ra (4000-200 cm l ) were reco rded a~ nujol mull s o n a Nicolet Magna 550 spectrophotometer. The NMR CH, DC, 21 AI and 11 9Sn) spectra were recorded in COCl) (PMR), CCI

4 or

1210 INDIA J CHEM, SEC. A. DECEMBER 1999

Table 1- Reactions of metal isopropoxides with 2-methylpcntane-2,4-diol

ReaelaniS Produel Liberaled Pr 'OH M.P. Analys is M.wt. (g, mol) Colour and slal e Found (OC) Found Found

Melal isopropoxide Glycol Yield (g,%) (Cald .) (Caled) (Caled .) M Glycoxy

Mg(OPr), H ,Mg(O.G.6 )J 1) 0.6 1 a 9.09 89.68 243 (0.74,0.005) (1.23.0.01 0) While solid pow or (0.62) (939) (89.82) (259)

( 1.46, 66%)

~

Ca(OPr), H,Ca (O ·G·O )~2) 0.6 1 14.29 84.25 287 (080,0 005 ) ( 1.19.0.010) While solid powder (0.6 1) (14 61) (84.66) (274)

( 1.38.93'70)

Sr(OPr), H SrtO~(1» (3) 0 .74 27. 11 71.89 338 (1.27,0.006)

, , (1.46,00 12) While solid powder (074) (27 .22) (7216) (322)

( 1.95.6 1%)

Ba(OPr), H,B3(O.G.b J,(4) 0.95 36.66 62.16 340 (2.01.0.008) ( l. g6,0.0 16) While solid powder (0.95) (3695) (62.5 1 ) (372)

(2.92. 78%)

Sn(OPr), ~(5)

H,Sn(O·G.O), O . R~ 33.37 363 (1 .66.0.007 ) (1.64.00 14) While solid powder (0.R4) (3362) (353 )

(2.45 . 63'70)

HAI(O.G.O), (6)

AI(OPr), 5.01 64 10.01 89. 16 264 (5.67, 0.028) (658. 0.055) Colourless sli cky 'so lid (50 1) ( 1037) (89. 23) (260 )

dill'" rll li melt uplll JOO"c.

Table 2-Reactions of metal s (Mg. Ca, Sr, Ba) wi th 2-methylpentane-2 .4-diol

R~ac tants Timc of Product (g, mol) retluxing Colour and slale

M Glycol (h) Yi eld (g. '70)

r---l Mg H , ~ l !!( O ·G ·O), (1) (0 .14. 0006) (1.31.0.011) IS \Vhilt.: solid powdL' r

(1.2 1,6 I 'k )

r---, Cn H,Cn(O·G·O), (2) (0.3 1, DOOR ) ( I. HI. 00 15) IS Will Ie ,olid powder

( 1.92. 63'7c)

Sr H ,~I , (3) (0 .. '2 . 0.(06) (1.19 . 0012) 10 Wh ir"e solid po,,;kr

( 1.82.65'''' 1

,----. (4) Ba H,13,,(O· G·O), (1 39.00 10) (2 32,0.020) WIllie solid powder

(3 .61. 6~'k)

ti tle !> /lIlt melt upto JOf) C

C H (liC 27 Al and 119Sn) solutions on a JEOL FX 90Q o 6 '

spec trometer. Mo lecular we ights were determined in benzene on a Gallenkamp ebulliometer.

Preparation of homo- and helero-leptic glyco lates The complexes were synthesized by a simil ar

procedure . For brevity, we have described onl y one method of eac h type.

Preparation 0/ H/;f(OCHMe.CHz.CMe/J)!

(a) The reac tion mixture containing 2 : I molar ratio of 2-methylpentane-2,4-diol and M(OPr')2

M.P. Analysis M.WL (OC) Found Found

(Ca l.lil (Caled.) M Glycoxy

9. 19 89.76 243 (9 .39) (8982) (259)

14A6 R4.30 283 ( 1-1.61 ) (84.66) (274)

27.08 71.93 344 (27 .22) (72.16) (322)

3629 62.46 387 (3595) (62.5 1 ) (372)

(M = Mg, Ca, Sr, Ba, Sn) in benzene suspension was refluxed for - I Oh and the liberated isopropy I alcohol was continuously fractionated out azeotropica ll y. The isopropyl alcohol content in the azeotrope was estimated periodically by oxidimetric method to monitor the progress of the reaction . When the azeotrope showed negligible presence of isopropyl a lcohol, the reaction was stopped and excess so lvent was removed under reduced pressure to afford a white coloured so lid. Recrystallizati on from II-hexane and to luene mi xture at -20°C afforded

SHARMA el at. : HOMO- & HETERO-LEPTIC GL YCOLATES 12 11

Table 3-Reactions of metal glycolates with AI (OPr')J

Reactants Produci LiberOied Pr 'OH M. P Analysis M.w!. (g. 11101) Colour and slale

,-----, Yield (g. %) H,M(O-G- O), AI(OPr').

r-----' .----. H .Mg(O-G-Ol , 1 AI(OPr'), ), 1 Mg(O-G-O), ) (1-02. 0004) -( I ) (1.4.1. 0(07) While solid powder

( 1.88.76%) ,....----, ~,

H.Ca(O-G-Ol, 1 AI(OPr'), }, 1 Ca(O-G-O), ) (0~8 2. 000.1 ) - (2) (1.21. 0 .006 ) While solid powder

( 1.60.75%)

r----1 r--' H.SrIO-G-OL 1 AI(OPr'), ), 1 Sr(O-G-O),) (1-6.1. 0 (05)- (3 ) (2 .08. 00 I 0) While solid powder

006.67%) ,.-----, ,----;

H.Ba(O-G-Ol. IA I(OPr'), ),I Ba(O-G-O), ) ( 1 ~ 2. 1. 0.(03) - (4) (l.30. 0006) Yellow so lid powder -

(2. 10. 64%) ,------. ,-----,

H.Sn(O-G-O), 1 AI(OPr), ) ,I Sn(O-G-O),! ( 1-59. 0.004) - (5) (1.79. 0(09) Yellow soli d powder

(28 1. 7 190)

the tit le derivatives . Preparati ve and analyt ical details are listed in Table I .

(b) The I : 2 reaction mixture conta ining freshly c leaned metal(M) (where M = Mg, Ca, Sr, B.a), and hexy lene glycol in toluene was refluxed - 10- 15 h to obtain a colourless solution (in case

of Mg and Ca, a pinch of HgC I2 and -2ml isopropyl alcohol were added to obtain the solution). Removal of the volatiles under reduced pressure, followed by recrystallizat ion from a mixture of n- hexane and to luene at -20°C

afforded white coloured derivatives of the

co mp os ition H/~1 (OCHMe.CH 2 .CM e 20 ) 2 ' Preparative and analytica l data for the deri vati ves

are given in Table 2 .

I I

2. Preparation (~f (Af (OPr')) } (Ba(O-G-O )}}

(10) (cf. Table 3)

(7)

(8)

(9)

(10)

(11 )

The ben zene (-70 ml) so lutions of H2 , . Sa (OCHMe. CH

2.CMe20)2 (4) ( 1.21 g, 0.003 mol)

and AI(OPr')l ( 1.30g , 0 .006 mo l) were refluxed for - J 2 h, with continuous fractionation of the li be rated isopropyl alcohol azeotropically. The progress of the reac ti on was monitored by estimating periodicall y the quantity of isopropy l a lcoho l co llected in the azeotrope. After co mpletion of the reacti on (as shown by the neglig ible presence of alcohol in the collected azeotrope) the sol vent was re moved under reduced press ure to obtain a ye ll ow solid(2.IOg) . Recrystallizati on from a mixture of n-hexane and to luene at _20DC yie lded a yellow coloured so lid

powJer (64%) . (Found : Sa , 20.65; AI, 8 .0 1 % ; m.wt. , 701 . Required : S a, 20.8 1; AI , 8. J 8 % ; m .w!. ,

660).

found (OC) found found (Caled.) (Caled.) (Caled .)

M Al

0.46 4.23 9.3 1 567 (0.47) (4.44) (9.87) (547 )

036 7.08 9.30 578 (0 . .16) (7 . 12) (9 .59) (563 )

0.60 14.29 8.64 600 (060) (14 .36) (8 .84) (6 10)

0.38 20 .65 8.0 1 701 (038) (20.8 1) (8. 18) (660)

0.53 18.42 8. 12 653 (053) (185 1 ) (8.42) (641 )

. ,- I

Derivatives {AI(OPr)? }? {Mg(O-G-O)?} (7), {AI(OPr')?}? {Ca(O-G-OU (8), {Ai(OPr')J 2 {S'r(O-G-O)? )(9 )~ and {A I(OP~\} 2 {SI\ (0-G-O) 2 }( 11 ) were prepa~ed in a simi lar manner. Preparative and analytical deta il s a re listed in Table 3 .

j I

Preparation of Ba (Af(OP'; )} (O-G-O)}2 (15 )

(c f. Table 4) To a benzene solution of freshly prepared

Sa {AI(OPri)4} 2 ( 1.69g, 0 .0025 mol ), hexy lene glycol (O.60g, 0.005 mo l) was added , and the reacti on mixture was refluxed for -6hr. The liberated isopropyl alcohol was fractionated out azeotropically and estimated . On removal of volati les unde r reduced pressure followed by recrystallization from ll-hexane and to luene mixture at _20DC, the titl e compound was

obtained as a white solid (1.65g, 83%) (Found : S a, 20.62 ; AI , 7.95 %; m.wt. , 701. Required : S a, 20.8 1; AI, 8. 18%; m.wt., 660).

Simi lar procedure was also e m p loyed for the preparation of derivatives Mg{AI(OPri), (O-G-O)}, (12) , Ca{AI (OPr i ) , (O-G-O) }, (13), and SrI A'I (OPr\ (O-G-O) }e - (14) . Pre para ti ve and analytical deta il s are summarized in Tabl e 4.

4. I ,

Preparation of Mg {AI (O-G-OU2 (16)

(c f. Table 5) Magnesium foi ls (0.22 g, 0.009 mol),

I I

HA l (O-G-0)2 (4.76 g, 0 .018 mol) , isopropy l alcoho l (- 1-2 ml) , and a pinch of HgCI2 were taken in toluene and refluxed for -20 hr to obtain a c lear soluti on. Vo latiles were removed from the so luti on, fo ll owed by recrysta llization from to luene (at-20D C )yielded a colourless solid powder (4.49 g, 79 Cfo ) (Found :Mg, 4.2 1; AI,

Table 4 - React ions of M {AI(OPr')J ~ with 2-methlpentane-2,4-diol

Reactants Product Liberated Pr'OH MP. (g, mol) Colour and Slate FOWld (oq

M{Al(OPr).}z Glycol Yield (g, %.) (Calc.)

I . 1 M=Mg Mg{AI(OPr>z(O-G-O)} 2 (12) 1.29 a

(2.92,0.005) (1.27,0.011) white solid powder (1.29) (2.85,89%)

j I M = Ca Ca {AI(OPI'>Z<0-G-O)} 2 (13) 1.07 a

(2.53,0.004) (1.06,0.009) white solid powder (1.07) (2.50,88%)

I I M=Sr Sr{AI(OPI')iO-G-O)}2 (14) 0.46 a

(1.2 1.,0.002) (0.47,0.004) white solid powder (0.47) (1.18, 7(010)

I I

M=Ba Ba{Al(OPrMO-G-O)}2 (15) 0.60 a (1 .69,0.0025) (0.60,0.005) white solid powder (0.61)

(1.65,83%) , I

M=Mg Mg {AI(O-G-O)2} 2 (16) 3.43 a (3.93,0.007) (3.38,0.028) colourless solid (3.43)

(3.87,61%) ,. I

M=Ca Ca{AI(O-G-O»)2 (17) 3.02 a (3.56,0.006) (2.97,0.025) colourless solid (3.02)

(3.48,85%) I i

M = Sr Sr{AI(O-G-O»)2 (18) 2.35 a (3.01,0.005) (2.32,0.020) colourless solid (2.36)

(2.96,74%) , I

M = Ba Ba{AI(O-G-O)2} 2 (19) 2.02 a (2.81,0.004) (2.00,0.011) colourless solid (2.03)

(2.76,66%)

Analysis Found (Calc.)

M AI

426 9.90 (4.44) (9.87)

6.99 918 (7.12) (9.59)

1413 8.66 (14.36) (8.84)

20.62 7.95 (20.81) (8.18)

414 9.66 (4.48) (9.94)

7.34 9.88 (7.17) (9.66)

14.19 8.39 (14.45) (8.90)

20.47 8.10 (20.93) (8.23)

Glycoxy

85.23 (85.58)

83.04 (83.17)

7633 (76.65)

7024 (70.84)

M.wt. Found (Calc.)

JlO (547)

579 (563)

005 (610)

701 (660)

564 (543)

589 (559)

623 (606)

668 (656)

tv

tv

Z 0 :; z

(') :r:: tTl

.s:.. C/)

tTl (1

> . 0 tTl (') tTl s:.. co tTl ;>;:I

:0 \0 \0

SIIARMA el 01. : IIOMO- & HETERO-L EPTI C GL YCOLATES 1213

Tahle 5-Reacliom or aluminium glycolale wi lh melals

ReaCIJnlS (g, mol)

Ti llleofrelluxing ProdUCI M .P. Analysis M .w!. (Ilr) Colour and Slale (DC) Found Found

.------, M = Mg,Ca,Sr,Ba HAI(O·G·O ),

yield (g. o/r )

,.---,

M

(Ca lcd.) (Caled.)

A I Gl ycoxy

Mg 20 Mgl lI /( U·G·O ) .I. (16) a 4 21 '! 76 X'i 26 'i6 1 (0 22, 0009) (4.76. 00 1 X) colourlcl\, ~t) h( l -

( 4 A~ . 7'!'7r) .--,

Ca 20 Ca ll1 l(O ·G·O >'I . (0.32. 000R) (4.16.0.01 6) culnllrk ... " so lid -

P .cO. 7 1'. ) r--.

Sr 10 S .. 1/\ I( o ·G ·O >'1 . (() ".1 . 0.006) (:1 .11, 0.0 12) cohltlrk!-s so ll d-

n 22. 57 '/. )

.-----. 11:. Ha l AI«(l·G ·O ). I . (0.42. 000.1) ( 1.59.0.006) rolourh::-.s ~olid -

(2 0 1. 6WI

9.76; glycoxy, 85.26 %; m.wl. 56 1. Required : Mg, 4.48; AI , 9.94; glycoxy. 85.28 %; m.w!. ,

Similar method was employed for the preparation of Ca{AI(O-G-O)2}2 ( 17). Preparative and analytical details are li sted in Table 5.

I I

5. Prepawlioll (~/B{/(AI(O-G -O)) 2 (19) (d. Table 5)

(a) Reacti on mi xture containing freshl y cleaned Sa metal (0.42 g. 0 .003 mo l), HAI (O-G-b )l ( 1.59g, 0.006 mol) , and hexy lene glycol (3 .0 I g, 0.008 mol) in toluene was refluxed for - 18h. Remova l of the vo lat iles under reduced pressure foll owed by di stilling out at 60°C/O.2mm the excess hex ylene glyco l, a white fluffy so lid compo und (2 .I Og) was ob tain ed . Recrys talli zation from toluene at low temperature afforded a colourl ess powdery solid (659'r) (Found : Sa. 20.16; AI. 8.0 1; glycoxy, 70.52%; m.w!. , 665. Required : Sa, 20.93; AI , 8.23; glycoxy, 70.84%; m.w!., 656). Derivati ve Sri AI(O-G-O )2} 2 (17) has been sy nthesized in a similar manner. Preparative und analytical detail s are collected in Table 5.

(b) Hexylene glyco l (2 .00g, 0.01 7 mo l) ami the benze ne so lut io n o f rre s h l~ prepa red Sa{AI (OPr\ }} (2.9 Ig, 0.004 11101) were retlu xed for - 12h. During thi s period the li berated isopropyl alcohol was fracti onated out azeotrop icall y and estimated. After the completi on of the reaction , the volatiks wae

(17)

(18)

(19)

(4AX) ( ~ . '!4 ) IXS 2X) (54:1)

7 01 'J -19 X.l II I 543 (7 17) (') ( 6 ) (Xl 17) ('i5')

14 07 X 67 76 11 6l.1 ( 1-1 -1 ») (X .<)O ) (76 (5) 16(6)

201 6 X 0 1 70 '; 2 66 '; (20<).1) (X21) (70 X4 ) (6'i6)

removed ill \'[[CIIO . Recrystall ization from toluene at -20°C afforded the title derivati \'e as a colourl ess solid powder (2.76g. 66Cff ) (Found : Sa, 20.47: AI , 8. 10: glycox y. 70.24% ; m.w!. , 668. Required : Sa. 20.93: AI , 8.23: glycox y. 70. 849'c ; m.wt .. 656).

A similar procedure was adopted to prepare Mg{AI(O-G-O), }, (16). Ca{AI(O-G-O), }, (17 ). and Sr{ AT(0-G-O)2}2 (18). Preparat~\;e and anal ytical detail s are li sted in Tab le -+ .

Results and Discussion Reacti ons of hex ylene glyco l (abbreviated as HO­

G-O H) in 2: I molar rati o with alkal ine earth metals (Mg, Ca, Sr. Sa) in toluene under rellu xin g conditi ons afford white coloured homometalli c g l ycolate~ :

C.H ,ClI ) '---.1 Il M + 2 HO-G-OH ) (O-G-O)M (O-G-O ) + H,i

10- I 5 hr H ~ I .

eM = Mg(J), Ca(2) , .. .(1)

Sr(3), Ba(4»

As the preparat iOIl of (1)-(4) by the react ion (i) requires longer period or rcflu xin g. these derivati \'es have also been pre pared by an alternati ve route (Eq. (i i)) in whi ch alkaline earth metal (Mg. . Ca. Sr. Ba) isopropoxides (prqxmxJ by the dissolut ion of alkal ine e<u1h meta ls in isopropyl alcohol) have been employed. This latter route of preparatic'n hcLs been extended to the corresponding Sn (lI ) deri vati\'e (5), for which the stL1l1ing

tv .... ~

Table 6 - NMR(' h. ~ 7 Al and llYS n) spec tra l data (8. p.pm) fo r homol eptic g lycolates

S.No. Compound IHNMR 17 Al/lI9Sn NMR

I I 1. H)Mg(0-G-0)2 (1) 1.25 (d(l = 6Hz), ~H , CHMe), 1.29 (s,6H, CMe), 1.34 (s,6H,CMez)' 1.52-1.83 (m,4H, CH2),

3.15 (hr, 2H, OH), 4.20-4.65 (m, 2H, CHMe)

I I 2. H

1Ca(0-G·0)2 (2) 1.16 (d(J = 6Hz), 6H, CHMe), 1.30(s, 6H, CMe

2) , 1.34 (s,6H, CMe), 1.56-1.70 (m,4H. CHl ),

3.80 (hr, 2H, OH), 4.11·4.51 (m,2H, CHMe)

I I S2 3. HzSr(O-G-O)~ (3) 1.21(d(J = 6Hz), 6H, CHMe), 1.31 (5,6H, CMez), 1.35 (s,6H, CMe2), 1.50-1.98 (m,4H,CH1), >-3.61 (br, 2H, OH), 3.84-4.21 (m,2H,CHMe) z

I I n 4. H2Ba(0-G-0)2 (4) 1.24 (d(J = 6ijz), 6H, CHMe), 1.27 (5,6H, CMe), 1.36 (5,6H, CMe), 1.~6-2.0 1 (m,41-'1,CH), :c

3.01 (hr, 2H,OH), 4.06-4.69 (m,2H,CHMe) m ~

I I {/l

5. H2Sn(0-G-0)2 (5) 1.25 (d(J = 6Hz), 6H, CHMe), 134 (5,6H,CMez)' 1.38 (s,6H,CMe2), 1.56-1 .70 (m, 4H, CHz)' -295.73 m

3,62 (br. 2H, OH), 4.11-4.56 (m, 2H, CHMe) n >-

I I (6) 6. HAI(0-G-0)2 1.23 (d(J = 6Hz), 6H, CHMe), 1.27 (5, 6H, CMe), 1.33 (s,6H, CMe2), 1.57-1.81 (m, 4H, CHz)' 66.00 0 m

3.34 (hr, IH, OH), 3.98-4.76 (m, 2H, CHMe) n m

I I ~

7. Mg{Al(0-G-O)2} 2 (16) 1.24 (d(J == 6Hz), 12H, CHMe), 1.39 (s, 12H, CMez)' 1.43 (s, 12H, CMe) , 1.61 -1.78 (m, 8H, CH2), 65.00 CP m

3.84-4.5 1 (m, 4H, CHMe) ;>;l

-I I

'D 'D

8. Ca{AI(O-G-O\ } 2(17) 1.25 (d(J = 6Hz), 12H, CHMe), 1.34 (s, 12H, CMe), 1.38 (5, 12H, CMe2), \.56-1.74 (m, 8H, CH), 66.00 'D

4.02-4.56 (m, 4H, CHMe)

r'~ 9. Sr i AI(O-G-O)z} 2 (18) 1.25 (d(J = 6Hz), 12H, CHMe), 1.30 (s, 12H, CMez), US (s, 12H, CMez)' 1.61-1.92 (m, 8H, CHz)' 70.10

4.11-4.56 (m, 48. CHMe)

I I 10. Ba {AI(O-G-O)l} 2 (19) 1.25 (d(l = 6Hz), 12H, CHMe), 1.33 (s,12H, CM e), 1.37 (s,12H,CMcz)' 1.58-1.74 (m, 8H, CH), 69.10

3.90-4.66 (m, 4H, CHMe)

~ '" -+ ..

Table 7 - NM R(' h. ~ 7A I and " ' Sn) spectral data (8. ppm ) for homoleptic glycolates

S.No. Compound IHNMR

I 1. (AI(OPri)z }z{Mg(O-G-O),}(7) 1.18 (d(J = ?Hz), 6H,CHMe), \.20 (d(J:::: 6Hz), 24H, CHMez)' 1.30 (s,.6H, CMel) , 1.38 (s, 6H, CMe2),

\.65-2.01 (m, 4H, CHz)' 4.21 (sept(J == 6Hz), 4H';'CHMe2), 4.31-4.66 (m, 2H, ClIMe)

2. . r--i

{AI(OPr'») z{ Ca(O-G.O)z} (8) \.23 (d(J == 6Hz), 6H, CHMe), 1.23 (d(J = 6Hz), 24H, CHMez)' \.30 (s, 6H, CMel ), \.37 (s, 6H, CMe), 1.53-1 .91 (M, 4H, CHz)' 4.12 (sept.(J :::: 6Hz, 4H, CHMez)' 4.34-4.75 (m, 2H, CHMe)'

I I 3. ( AI(OP~)z}z {Sr(O-G-O)l}(9) 1.16 (d(J = 6Hz), 6H, CHMe), 1.24 (d(J :::: 6Hz), 24H, CHMe), 1.34 (5, 6H, CMez)' 1.38 (s, 6H, CMe2),

1.52-1.89(m, 4H, CH2) , 4.09 (sept(J :::: 6Hz), 4H, CHMe

2), 4.44-4.79 (m, lH, CHMe)

4. I I .

{AI(OPr')2}, (Ba(O-G-O)2}(10) 1.17 (d{J = 6Hz), 6H, CHMe), 1.22 (d(J:::: 6Hz),.24H, CHMe2), 1)3 (s, 6H, CMel), 1.39 (s, 6H, CMez)' 1,49-1.55 (m, 4H, CHz)' 4.12 (m, 4H, CHMe), 4.41-4.72 (m, 2H, CHMe)

1 5. {AI(OPri)2} 2 (Sn(O-G-O)z}(ll) 1.23 (d(J:::: 6Hz), 6H, CHMe), 1.36 (d(J:::: 6Hz), 24H, CHMez)' 1.30 (s, 6H, CMe2), 1.34 (s, 6H, CMe2),

1.52-1.81 (m, 4H, CH2) , 3.91 (sept(J == 6Hz), 4H, CHMe), 4.14-4.45 (m, 2H, CHMe)

6. I I

Mg {AI(OPr\(O-G-O)} 1 (12) 1.I9-1.79 (CHMe. CHMe2, CMez' CHz), 4.11-4.83 (CHMc, CHMez)

I I 7. Ca{AI(OPriMO-G-O)} z (13) 1.12-2.01 (CHMe, CHMe

2, CMe

l, C~), 3.89-4.65 (CHMe, CHMez)

8. I I

Sr{AI(OPr\(O-G-O)}z (14) 1.12-1.79 (CHMe, CHMe2, CMe2, CHz)' 3.71-4.49 (CHMe, CHMel)

I -I 9. Ba{AI(OPri)2(O-G-O)}! (15) 1.12-1.88 (CHMe, CHMe2, CMe2, CHz)' 3.66-4.60 (CHMe, CHMe})

'r

17 AI! lI9$n NMR

66.41

65.31

45.3

64.33

75 .001-595.67

70.73

69.70

62.50

65.94

V1 ::r: >-~ >­~ ,::, :--

::r: o $: 9 Ro ::r: tTl -l tTl ;I:l

9 r tTl "0

::? n o r -< n o r >­-l tTl V1

IV

'JI

12 16 INDIAN J ('HEM, SEC. A, DECEMBER 1999

material, Sn(OPr)2 has been synthesized by the reaction of stannous chl oride with potassium isopropoxide in I .2 molar rdtio in benzene (SnCI2 + 2 KOPri ~ Sn(OPri)2 + 2 KClt) : thi s has been done as II YSn NMR spectrum was particu larl y helpful in the elucidati on of stmctural fea tures .

C II ,- , II 1«( )f\ 'l ~ 2 11O-G-OH _~ h~ ' (~-G-O)~1 (O-~ + 2 Pr()HI

(M ~ Mg( I ). C"(2) ,

Sr(3), Fl.(4) , Sn(1 I)(5»

.. (i i )

The his-deri vati ve of AI has been synthesized by the reacti on (iii ) illustrated below.

C H ,---, . . ~ !(OPr'), T 2 HO-G-Ol! -' -' ~ HAI(O-G-O), + 3 Pr'OHI ...

.. 7 hr (6) ... ( 11 1)

The deri vat ives (1 )-(5), which can be stmctural ly represented by the fo rm (A) or (8 ) (the latter , being more probable)

(A) (8)

are use fu l syn th ons for the sy nthesis of novel heterob imetallic glyco late deri vati ves.

C· H -----. (1)-(5) + 2 AI(OPr'), -t2 hr ) {i\ I (OP~),),{ M(O-G-O), } + 2 I'r'O II 1

(M = Mg(7). CarR).

Sr(9), Ba( I O), Sn(ll) (11)

.. ( i v)

Reactions (in I • 2 molar ratio in benzene) of metal bi s( tetraisopropoxoaluminate) derivati ves with hexylene glycol un?er rellux ing colndi tions afford deri vatives of the type M {AI(OPr')/O-G-O)} 2.

C H ,---, \!fAUOI'r) : q IIO-G-D1i •• ) M\A1I01'r'),(O-G-OH, +4PrOHi . , , , -6 hr ' .

. (M ~ Mg(12) , Ca( 13). ...(v)

Sr(14), Ba(15»

Homokptic heterobimeta llic glyco lates of the alkaline eart h metals can easily be prepared accordi ng to the reac ti on (v i) shown below:

,~I ) ? H;\UO-:za) C.H ,C H " 1\.1(AI(O-G ) >) , I , + H , t - . , - 20 tu - - -

(6) (M = M g(1 6). Co(l 7),

S r ( I S) , Fl ,, ( l 'l»)

(v i )

Preparations of similar derivati ves of Mg and Ca require a minimum amount of isopropyl alcohol (- 1-2 ml) and a pinch of HgCI2 as a catalys t.

The above deri vati ves (16)-(19) have also been prepared by the reaction of M{ A I (OPri ) ~ } 2 with hexylene glyco l:

M{AI(OPI')J }1+4 HO-G-OH -t M (AI(O-G-O)1}2 + 8 PI'OHi

(vii )

All these deri vatives <ire soluble in common organic so lvents (benzene, to lue ne, etc.) , monomeric (ebullioscopically) in benzene, and moisture-sensiti ve.

Infrared spectra of hornoleptic heterobimetallic glycolates (16) - (19) exhibi t absorptions (in em-I) due to glyco late moietyB I2 in the reg ions: 1170-11 35 (vCMe2), 1 090~ I 030 (vC-O) , and new absorpti ons due to metal-oxygen bond 6 10-695 (v AI-O) and 570-490 (v M-O) (M = Mg, Ca, Sr, Sa, Sn).

The homoleptic homometall ic glycolates (1 ) - (6) show absorpti ons at 11 93-11 72, 1095- 103 1, and 698-422 em-I respecti vely due to vCMe

2, vC-O and vM­

o (M = Mg. Ca, Sr, S a, Sn, AI). These deri vat ives also ex hi bit a broad peak at 3379-3344 cm-I due to vOH. The deri vati ves (7)-( 11) ex hibit peaks at 11 59-11 09 cm-I due to vOPri due to glyco late mo iety and no absorption in the v(O-H) reg ion an expected .

IH NMR da ta for the new derivati ves are co ll ected in the Tables 6 and 7 and peak ass ignments are based on the bas is of publi shed data on 2-methy lpcntane-2.4-dlol and their known metal derivat ives I 2.13

IH NMR spectra of the homometall ic glyco late deri vati ves (1)-(6) show two si nglets in the regions 8 1.2 1- 1. 34 and 1.30 - 1.38(CMc

2), a doublet (J =

6Hz) at 1.16- 1.25 (CHMe), two mu ltiplets . one at 8 1.49-2 .0 1(CH

2) and other 3.84 -4.73(CHMe), as

well as a broad peak due to OH protons at 3.0 1-3.80 (Table 6).

In add ition to the above (except the OH peak ). the heterob imeta llic alkox idc - glycox icle derivatives (i )­(I I) ex hi bit resonances due to isopropoxy group : a doublet (1 = 6Hz) at 8 1.22- 1.36 (CHMe

2) and a septet

(.I = 6Hz) at 3.9 1-4.12(CHMe2

) (Table 7) .

The derivat ives (12)-(15) (prepared accordin g to the reaction (equat ion v) illustrated above) exhibit broad peaks in the regions 8 1.12-2.0 I and 3.66-4.83. where signa ls due to CMe=:, CHMe, CHMe

2, CH

2 and

CHMe, CHMe2

groups are generall y observed, respectively (Table 7).

SHARMA el 01.: HOMO- & HETE RO-L EPTIC GL YCOLA TES 12 17

Heterometall ic homoleptic glycolates (16) - (19) ex hibit 'H NMR signal s characteristic of glycolate systems (Table 6).

Homo- and hetero- metallic homoleptic glycolate deri vatives (1)-(6) and (16)-(19) ex hibit L1C peaks at 824.3 - 24.7 and 27.03 -28.93 (CMe

2), 31.96 - 32.96

(C HMe), 49.90-53.9 1 (CH), 64.46 -65.66 (CHMe), and 70.80 - 71.29 (CMe2).

Heterometallic alkoxide-glycoxide derivatives (7)­(15) exhibit i3C resonances in the regions: 825.51 -26.76 (C HMe?) and 62.84 - 66.53 (C HMe) characteristic of the isopropoxy groups, alongwith the resonances due to the glycolate component.

" 'ISn chemical shift (Table 6) for the derivative (5) at 8 -295.73 is indicati ve of penta-coordinated '4 1) tin ( II ), whereas the derivative (11 ) exh ibits 119S n NMR signal (Table 7) at 8-595 .67 cons istent with hexa­coordination '4. ' 6 around tin .

Appearance of 27AI NMR signals (Tables 6 and 7) in the region of 8 60-80 for the deri vatives (6)-(19) is indicati ve for a tetrahed ral geometry l7· I R. 19 around the aluminium atom.

Although in the absence of X-ray crystallographic data (for which our attempts failed so far) ass ignement of definitive structures for thest.! new derivatives (7)­

( 19) is a difficult task , the observed spectroscopic and molecular we ight data, along with the precedence ava ilable in the literature ' R it is possible to suggest structures (7)-(11), (12-15), and (16)-(19) of the types show n in Stmcture I, II and III , respectively.

(M = Mg(7) . ea(S), Sr(9) , l3a(10). S11(11)(II »

PI' PI'

(M = Mgt12). Cat13). Sr( 14) . n .(15»

11

(M = Mg(16), Ca(17) , Sr(18), Ba(19)

III

Although the derivatives (12)-(15) adopt the more logical stmcture shown in II , but due to the larger size of alkaline earth metals , glycol moiety is expected to shift from aluminium to the central metal atom in an attempt to coordinatively saturate the larger alkaline earth metals. In view of thi s, the stmcture shown in I appears to be more plausible. Such type of shi fting of a chelating ligand (e.g., Zr

2(OPr i) 9 - ) from smaller

atom (e.g ., Cd) to a larger one (e.g., Ba) has recently been observed by Veith and co-workers20 in a react ion shown below:

{Zr, (OPr).} ICdl + KBa(OPr'), -7 { (OPr'),Cd I Ba{ Zr2(OPr' )~ I - + KI t

Acknowledgement

The Department of Science and Technology, ew Delhi is thanked for supporting of our work .

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