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E L S E V I E R Journal of OrganometallicChemistry524 (1996) 271-273cy

Pre l iminary communicat ionHyb rid inorganic organo m etall ic compou ndswith gall ium gallium bondsAlan H. Co w ley , And reas Dec ken Claudia A . Olaz .bal

Departmen t o f Chemistry and Biochemistry The University of T~:~as at Austin A u.~tin TX 787 12 USAReceived 10 July 1995; revised 29 M arch 1996

Abstrac tThe first examples of digallium com pound s tha t feature both organ o and halo substituents, [Li(THF)4][Ar'(CI)GaGaCI~] 1) andAr (CI)GaGa(CI)Ar (2) , hav e been prepared by reaction of G aaCi4. 2 d ioxane wi th LiAr ' (A r '= 2 ,4 ,6- 'Bu3C 6H 2) . he Ga:CI ,skeleton of 2 is p lanar w ith a dihed ral angle of 180 .

Ifept ords: Gallium; Digalliumcomlmunds;X-ray crystal stnlctures

I . I n t r o d u c t i o nI n t e r e s t i n t he lowe r ox ida t ion s t a t e s o f t he he a v ie r

Gr o up 13 e l e m e n t s i s e m e r g in g , a o . d p r om ise s a r i c hh a r v e s t o f u n u s u a l d e r i v a t i v e s w i t h m e t a l - m e t a l b o n d s( for a rev iew see Ref . [ I ] ). In the con text o f ga l l iu mc he m is t r y , t he s im p le s t suc h spe c ie s c om pr i se b im e ta l l i cc om pou nds o f t he ty l~ R ~ Ga G a R 2 a nd [ R 3Ga Ga R ~ ]2o .The c un ' e n t ly a va i l a b le e xa m ple s o f t he se c l a s se s o fc o m p o u n d a ~ e i t h e r f u l l y o r g a n o - s u b s t i t u t e d n e u t r a lm o l e c u l e s ( R - ( M e 3 S i ) z C H [ 2] , 2 , 4, 6- ~ P r3 C 6 H 2 [ 3] ,2 , 4 , 6 .( C F 3) 3C o H 2 [ 4] ; R 2 ~ c a r bo r a ne [ 5 ] o r c om ple t e lyha lo - subs t i t u t e d ( se e R e f . [ 2 ] f o r b ib l iog r a phy ; f o r a nin t e r e s t ing c a ge - a m ido de r iva t ive , s e e R e f . [ 6 ] ) . We~ p o r t t h e fi r st e x a m p l e s o f d i g a l l i u m c o m p o u n d s t h a tf e a tu r e bo th o rgoaa o a nd ha lo subs t i t ue n ts .

T h e r ea c ti o n o f 1 e q u i v a l en t o f G a 2 C I 4 . 2 d i o x a n ew i t h 1 .4 e q u iv a le n ts o f L i A r ' ( A r ' = 2 , 4 ,6 - t B u 3 C 6 H 2 )i n E t 2 0 s o l u ti o n a t - 7 8 C a f fo r d e d , a f t er w o r k - u p , a54% y ie ld o f t he sa l t I ( S c he m e 1 ). I f t he num be r o fe qu iv a le n t s o f L iA r ' w a s inc r e a se d to 2 .2 , a nd the o r de ro f a dd i t i on wa s r e ve r se d , a d i f f e r e n t p r oduc t , 2 , wa sob ta ine d in 51% y ie ld . M or e ove r , I c ou ld be c onve r t e dt o 2 b y t re a t m e n t w i t h . 0 e q u i v a l e n t o f L i A r ' i n E t 2 0s o l u t i o n a t - 7 8 C , a l b e it i n l o w y i e ld (1 2 % ) . C o r n -

" Correspondingauthor.~Presen t address: Department of Chem istry, Unive rsity of NewBrunswick, Fredericton, NB E3B 5A 6, Canada.

pounds 1 a nd 2 a t e bo th a i r - se ns i t i ve , c o lo r l e s s c r ys -t a l li ne so l id s . The p r e l im ina r y ide n t i f i c a t ion o f I wa sba se d on a sa t i s f a c to r y e l e m e n ta l a na lys i s a nd I H a ndI ~ C { l i f l NM R e v ide nc e f o r t he p r e se nc e o f a n Ar 'moie ty . Compoul~d 2 was charac te r ized in i t ia l ly in as im i l a r f a sh ion ; howe ve r , i n t h i s c a se i t wa s a l so poss i -b le to secure a sa t is fac tory highoresolut ion mass spec t ra lva lue tb r t he m ole c uhu ion ( F ound 698 . 2424 ; C a lc .698 . 2427) .F or a m or e de f in i t i ve c ha r a c t e r i z a t ion o f I a nd 2 i twa s ne c e ssa r y to a ppe a l t o X- r a y c r ys t a l log r a phy .[ C r ys t a l da t a f o r 1" C~ ,, H61C I, ,Ga ~ L, O4 . M = 8 2 2 . 0 ,m o n o c l i n i c , P 2 1 / c , a = 19 . 531( 3 ), b= 9 . 9 02 ( 2 ) , c -~2 2 . 7 7 0 (3 ) A , / 3 - -- 1 0 1 . 6 1 (1 ) . V = 4 3 1 3 ( 2 ) / ~ ~, Z = 4 ,P ca te = 1 . 2 6 6 g c m - I M o Ko t 0 . 7 1 0 7 3 ~ , ~ =15 .28 c m - ~ . 587 6 un ique da t a we r e c o l l e c te d a t 298 Ko n an E n r a f - N o n i u s C A D 4 d i ff ra c t om e t e r ( 0 - 2 0 s c ante c hn ique , 4 . 0 < 20 < 45) . O f the se , 1996 ha d F >4o ' ( F ) a nd w e r e use d f o r s t r uc tu r e so lu t ion ( d i r e c tm e th ods ) a nd r e f ine m e n t , R = 8 . 40%. C r ys t a l da ta f o r2 : C 34H ~ sC I z Ga 2 . M = 701 . 2 , o r tho r ho m b ic , C m c a , a= 12 . 839( 3 ) , b - - - 1 3 . 55 3( 3 ) , c = 25 . 890(5 ) ,~ , , V- --

o4 5 0 6 (2 ) A ' , Z = 4 , P ca tc -- 1 . 0 3 3 g c m - ~ , M o K a0 . 7 1 0 7 3 ~ , / . t = 1 3 . 3 2 c m - I . 1 5 3 8 u n i q u e d a ta w e r ec o l le c t ed a t 2 9 8 K o n a n E n r a f - N o n i u s C A D 4 d i f f r ac -tom e te r ( 0 - 2 0 sc a n t e c hn ique , 4 . 0 < 20 < 45) . O ft h e se , 8 43 h a d F > 4 o ' ( F ) a n d w e r e u s ed f o r s t ~ c t u r eso lu t ion ( d i r e c t m e thods ) a nd r e f ine m e n t , R = 10 . 26%. ]C o m p o u n d 1 c r y s t a l l i z e s i n t h e P 2 ~ / c spa c e g r oup

0022-32 8X/96 / 15 .00 Copyright 1996 Elsevier Science S.A. All rights reserved.Pli S 0 0 2 2 - 3 2 8 X ( 9 6 ) 0 6 3 8 2 - 6


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272 A.It. Cow ley et al. / Journal of Organometallic Chemistry 524 1996) 271-273

Ga~14.2 io~eme,1 4 A Y L i ~ E ~ [L KT IW ),d "

Et20 ~ LiCIAt: Cl2 2 A g L i + C~I~I4 2dioxM EtzO ~C~

Scheme I.wi th four molecules pe r uni t ce l l . There a re no unusu-a l ly shor t in te r ionic contac ts and the [A r ' (CI)G aGaC i 3]-and [Li (THF )4] + ions res ide o n genera l p os i t ions ; ne i -t he r i on ha s c rys t a l l og ra ph i c a l l y i mpose d symme t ry .The anion of I fea tures both three - and four-coordina tega l l i um a t oms w h i c h a re un i t e d by a ga l l i um-ga l l i umbond (F i g . I ) . The ge ome t ry a t t he G a ( I ) c e n t e r i s

t r igona l p lanar (sum of angles 359.0(5) ) ; however ,ow i ng t o t he s t e r i c de ma nds o f t he bu l ky a ry l g roup , t heC ( I ) - G a ( I ) - G a ( 2 ) a n g l e ( 1 3 6 .9 ( 5 ) ) i s a p p r ec i ab l ymore obtuse than the idea l va lue . This i s not t rue of theC ( 1 ) - G a ( I ) - C I ( 1 ) a n g le , b e c a u se th e a ry l a n d C ( I ) -G a ( l ) - G a ( 2 ) p l a n e s ar e a lm o s t o r th o g o n a l . T h e g e o m e -t ry of Ga(2) i s t e t rahedra l and the depar tures fzom thei de al va l ue s c a n be unde rs t ood o n t he ba s i s o f t he s t e ri ci n f l ue nc e o f t he A r ' mo i e t y . S pe c i f i c a l l y , t he G a ( I ) -G a ( 2 ) - C I ( 2 ) (1 1 2 .4 (2 ) ), G a ( I ) - G a ( 2 ) - C I ( 3 )(11 . 4 (2 ) ), a nd G a ( I ) -G a (2 ) -C I (4 ) (115 .0 (2 ) ) a ng l e sa re la rger than the remaining three bond angles a tG a (2 ) . The ga l l i um-ga l l i um bond l e ng t h i n I i s2 .422(3) /~ . In te rms of th i s met r ica l pa ramete r , thec l ose s t a na l ogue s o f 1 a re t he s a l t s [N Me 4]~ [CI3G a -G a CI~ ] [7] a nd [P h3P H ]2[CI3G a -G a CI 3 ] [8] fo r w h i c ht h e g a l l i u m - g a l l i u m b o n d l e n g t h s a r e 2 , 3 9 ~ 2 ) a n d

O 2.404(2)A respec t tve ly . I t mtght be expec ted tha t thega l l i um-ga l l i um bond l e ng t h i n 1 w ou l d be sho r t e r t ha ttha t in the [Ga2CI6] 2- anion, s ince the form er fea turesone sp r and one sp 3 ra the r than two sp 3 hybrid ized

CtB} 1 ~ c (g )

C ( 1 ~ C ( 3 ) C , 2 1 / v - - C ,,3 , . ~ C,,4,

C~t2~e o,C~lB)(:(17)

F ig . I . V i ew and humo r i ng scheme or I . Hydr ogenatoms are om i tted for c lar it y .

CI

CI13)

~C191

Fig 2 V iew and numl~dn g scheme or Z Hydrogen a toms are omi t ted fo r c la ri ty


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A.H. Cowley et al. / Journal of Orgaemmetallic Chemiswy 524 1996) 271-27 3 273gal l ium a toms. The longer bond leng th in the mono-an-ion 1 i s p resumably due to s te r ic e f fec ts .Compound 2 crysta l l izes in the or thorhombic spaceg r o u p C m c a with four molecu les per un i t ce l l . Thereare no unusual ly shor t in termolecu lar con tac ts , ' andmolecu les o f 2 res ide on a m ir ror p lane tha t inc ludes CI ,Ga, and (2( i ) , and the o ther ha l f o f the molecu le i sgenera ted by a cen ter o f symmetry loca ted a t the mid-p o in t o f t h e Ga- Ga b o n d ( F ig . 2 ) . As a co n seq u en ce ,the (2(1)CIG a-Ga (A)C I(A)C (IA) skele ton is requ ire~a tobe p lanar and the ary l r ings are perpendicu lar to th isp lane . For compar ison , the d ihedra l ang les be tween theGa C z p lane s in o rgano-subst i tu ted d iga l lanes are around0, 43 .8 , and around 90 fo r Ga2{CH(SiMe3)2}4 (3) [2] ,G a z ( 2 , 4 , 6 - i P r 3 C 6 H 2 ) 4 ( 4 ) [ 3 ] , a n d G a 2 ( 2 , 4 , 6 -

C F 3 ) 3 C 6 H z ) 4 5 ) [4] respectively.Th e g a l l i u m- g a l l i u m b o n d l en g th in 2 (2 .4 3 8 ( 6 ) ~ , ) i sshor ter than those in 3 (2 .541(1) ~, ) [2 ] , 4 (2 .5 13(3) ,~ )[31 , and 5 (2 .479(1) A) [4] . Presum ably , the reason forth is shor ten ing s tems f rom the fac t tha t 2 fea tures twora ther than four bu lky subst i tuen ts . However , a l thoughthe geometry of ga l l ium is t r igonai p lanar , the C(I ) -G a- G a( A ) an g le ( 1 4 2 .7 ( 8 ) ) i s co n s id er ab ly l a r g e r t h anthe o ther two, thus ind ica t ing the opera t ion of s te r iceffects.

2 Exp erimen tal sect ionI : A so lu t ion of (2 ,4 ,6- tBu:~C 6l tz)Li (1 .31 g ,5 .18 re too l) in 30 ml of Et~O was added to a so lu t ion ofG a ~ C I 4 . 2 d i ox a n e ( I . 6 8 g , 3 .7 m m o l ) i n 3 O ra l o f E t a Oat ~. 78 '~C. The reac t ion mix ture w as a l lowed to w armto ambient temperature and was stirred for an additional19h. ' l l le colorless mixture was f i l tered and the solventwas removed under reduced pressure . The whi te res iduewas w ashed wi th 15 ml of hexane , fo l lowing w hich i twas d i s so lv ed in 7 0 ml o f a I : 1 mix tu r e o f E t2 0 an dTH F. C o lo r l e ss c r y s ta l s o f 1 (m .p . 1 6 0 - 1 6 2 C ) f o r medin 54% yie ld upon cool ing the sa tura ted so lu t ion to- 2 0 C . t H N M R ( T H F - d s ) : ~ 1 . 3 1 ( s, 9 H , ( s , p -(CH 3)3C) , 1 .58 ( s , 18H, ( s , o - (CH~)~C ) , 7 .46 ( s , 2H,H-ary l ) ; L~C{IH}NMR C6D6) : 8 31 .38 ( s , p - (CH 3)3C ) ,34 .93 ( s , p - (CH~)3C) , 33 .71 ( s , o - (CH3)~C) , 38 .44 ( s ,o - (CH0.aC) , 122 .14 ( s , m-C ary l ) , 128 .66 ( s , ipso-C) ,151.39 ( s , p -C ary l ) , 157 .94 ( s , o-C ary l ) . Anal . Found:C, 49 .47 ; H, 7 .30 . C34H6tCi4Ga2LiO4 Calc . : C , 49 .68 ;H, 7 .4 8 %.2: A so lu t ion of Gaz CI a d ioxane ( .2 5 g , 2 .7 mm ol)in 3 0 ml o f E t2 0 was ad d ed to a s t i r r ed so lu t io n o f( 2 , 4 ,6 - t B u 3 C 6 H 2 ) L i ( 1 .5 g , 6 . 0 m m o l ) i n 3 0 m l o f E t 2 0a t - 7 8 0 (2 . Th e r eac t io n m ix tu re w as a l lo wed to w a r m

slowly to ambien t tempera ture and was s t in ' ed for a

fur ther 4 .5h . Fo l lowing f i l t ra t ion , the resu l t ing whi tep o wd er was wash ed wi th 1 0 ml o f h ex an e , t h en d i s -solved in 30 ml o f toluene. Co lorles s crystal~ of 2 (m.p.109-110(2) fo rmed in 51% yie ld upon cool ing thesa tura ted so lu t ion to -2 0 C . ~H NM R (C6D6): 6 1 .26(s , 18H, ( s , p - (CH 3)3C) , 1 .52 ( s , 36H , ( s , o - C H 3 ) 3 C ) ,7.48 ( s , 4H, H-ary l ) ; t3C{IH}NMR (C6D6) : 6 31 .36 ( s ,p - ( C H 3 ) 3 C ) , 3 4 .9 0 ( s , p - ( C H 3 ) 3 C ) , 3 3 .5 4 ( s , o -( C H3 ) 3 C ) , 3 8 .4 8 ( s , o - C H 3 ) 3 C ) , 122.30 ( s , m -C ary l ) ,141.74 (s, ipso-C) , 151.43 ( s , p -C ary l ) , 156 .49 ( s , o -Caryl ). Anal . F ound: C , 60 .91 ; H , 8 .10 . C36HssGa2CI 2Calc . : C , 61 .66 ; H, 8 .34%.As an a l te rna t ive (bu t lower y ie ld) syn thesis o f 2 , aso lu t io n o f ( 2 ,4 ,6 - tB u 3 C 6 H2 ) L i ( 0 .4 0 g , i . 6 mm o l ) i n15ml of EtzO was added to a so lu t ion of (1 .31 g ,1 .6 mmo l ) in 1 5 mi o f E t2 0 a t - 7 8 C . Th e r eac tionmixture was a l lowed to warm slowly to ambien t tem-pera ture and was s t ir red for a fu r ther 3 h . Wo rk-up ofthe reaction mixture as described above afforded a 12%yield of 2.

3 Note adde d i n pr oof

Since the submit ta l o f th is m anuscr ip t , a comm unica-tion has appeared in which the (dimeric) tr is( tr imethyl-silyl)si lyl analogue of 2 is described: G. Linti and W.Kost ler , Angew. Chem., In t . Ed. Engl . , 35 1996) 550.

A c k n o w l e d g e m e n t sWe are grateful to the National Science I :oundadonand the Rober t A. Welch Foundat ion for generous

financial support .

References[I] W. Uhl, Angew. Chem ., Int. Ed. EngL, 32 1993) 1386.[2] W . Uhl, M. Layh and T. Hildenbrand, J. Organomet. Chem.. 364

1989) 289.[3] X. He, R.A. Bartle tt, M .M. OImstead, K.R. Senge, B .E. Sturgeonand P.P. Power, Angew. Chem., Int. E d. F,t~gl., 32 1993) 717.[4] R.D. Schluter, A .H . Cowley, D.A. Atwood, R.A. Jones, M.R.Bond and C.J . Carrano, J. Am. Chem. Soc., 115 1993) 2070.[5] A.K. Saxena, H. Zhang, J .A. Maguire , N.S. Hosmane and A.H.Cowley , Angew. Chem., Int. Ed. Engl., 34 1995) 332.[6] M. Veith, F. Goffing, S. Becker and V. Huch, J. Organomet.Chem., 406 1991) 105; M. Veith and J . P~hlmann, Z. Natur-forsch. B, 43 1988) 505.[7] K.L. Brown and D. Hall, J. Chem. Soc., Daiwn Trans., 1973)1843.[8] M . Khan, C. O Idham, M .J . Tay lor and D.ed. Tuck, Inorg. Natl .Chem. Lea., 16 1980) 469.

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