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Cyclooctatetraenyl complexes of the early transition metals and lanthanides IX. (Cyclooctatetraenyl)lanthanide diazadiene complexes
oumal & meEi%c
of
Chemistry
ELSEVIER
Cyclooctatetraenyl .
complexes of the early transition metals and lanthanides IX. ’ ( Cyclooctatetraenyl) lanthanide diazadiene complexes Peter Poremba, Frank T. Edelmann
*
Abstract Complexes prepared
of’ the type (COT
in a ‘one-pot’ reaction
silyl kyclooctatricne coordinated DAD
and
’)Ln(DAD)(THF)
[Ln = Sm. Yb: COT
by treatment of elemental
+ = I.4(Me,Si),C,H,;
samarium or ytterbium
I .-I-dia/.adicnc ligands. ’H and “‘Yb
NMR
DAD
with equimolar
= l.$diaLadienes]
data show that the Sm derivatives
radical anions. while in the case of Yb the neutral DAD
have been
amounts of 1,4bis(trimethylcontain Sm’+
ions and
lipand is coordinated to divalent ytterbium. 0 1997 Elsevier
Science S.A. Kc~.~o~ls: Organolunthnnide coml4exc.s: Cyclooctatetraenyl ligands: Dkadiene
1. Introduction I ,4-Diazadienes are highly versatile, structurally tlcxible ligantls for which complcxcs arc known with various metals throughout the Periodic Table. The diazadienc (DAD) ligands can hc coordir~a~ed to a metal ion either as neutral ligands [2-61, as radical anions [7- 121, or as dianions [I%- 181. The latter coordination mode is preferred in the case of early transition metals in their high oxidation states as well as alkali metals. In recent years, DAD ligands have been frequently employed in lanthanide chemistry as well. It has been shown by NMR studies and crystallographic investigations that diazadienes are coordinated to lanthanides preferably as the radical anions. Among the first examples was the corn plex horn oleptic neodym ium(III) (rBuN=CHCH=NtBu),Nd, which was prepared by co-condensation of the ligand with neodymium vapor [ 19,201. Later, other homoleptic complexes of the type (DAD),Ln (Ln = Y. Sm. Yb) [2O] and (DAD),Ln (Ln = Y b) [2 I] have also been reported. #I, Me,), Sm(THF), readily adds diazadienes to yield samarium(III) complexes the dark brown
’ Corresponding author. ’For Part VIII. see Ref. [ 11. 0022-.32~X/97/$17.00 0 1997 Elsevier Science S.A. All rights reserved PI/ soo22-328X(97)00523-8
ligands; Samarium: Ytterbium
(C,Me,),Sm(DAD) [22]. More recently it has been shown by Scholz et al. that [(DAD)Li] units may act as complexes Cp-like ligands in orlanolanthanide [IS, 16,231. We report here the preparation and characterization of the first (cyclooctatetraenyl)land~anide diuzadienc complexes. For solubility rcrrsons the expcriments have been carried out using the I,4-bis(trimcthyIsilyl)cyclooctatetraenyl ligand, I.4-!Me,Si),C,H,?,(COT * ).
2. Results and discussion The I .4-bis(trimethylsilyl)cyclooctatetraenyl ligand has been introduced into organolanthanide chemistry by Cloke et al. [24-261. This very bulky cycloctatetraenyl dianion often provides higher solubility and better crystallinity to organolanthanide derivatives as compared to The preparation of the parent COT complexes. organolanthanide half-sandwich complexes containing one COT ’ ligands is, however, not always straightforward, as the products are often contaminated with the anionic sandwich complexes [Ln(COT * J2]- [I]. Therefore, a salt-free route to the title compounds was developed, which involves the simultaneous reaction of lanthanide metal powders with equimolar amounts of I&
bis(trimethylsilyl)-2.5.7~cyclooctatriene and diazadienes
in THF solution according to Scheme I. The reactivity of the lanthanides was enhanced by addition of a small amount of I-&Cl, which is known to activate the metal surface [27]. Only in the case of ytterbium and glyoxalno reaction bis( r-butylimine). rBuN=CHCH=NrBu, was observed. In the course of the reaction. the starting material I .4-bis(trimethylsilyl)-2,5.7-cyclooctatriene is 1,4_bis(trimethyldeprotonated to the silyl)cyclooctatetraenyl dianion (COT * )‘-. It is known from the literature that (C, Me,),Sm(II) reacts with various reagents such as cyclopentadiene, terminal acetylenes, or hydrazines under deprotonation and formation of the corresponding anionic ligands [X29]. Thus, it is plausible to assume the formation of a (COT ’)Ln(II) intermediate. which then adds the diazadiene l&and. Thz latter step has once again a precedent in (C,Me,),Sm(II) chemistry [Z]. The proposed reaction pathway is supported by the fact, that the reaction was successful only with samarium and ytterbium, which are known to have a rich organolanthanide(I1) chemistry [30]. The preparation fails in the case of other lanthanide elements such as praseodymium or neodymium. which are much more difficult to reduce. All three diazadiene complexes are isolated as deeply colored, thermally stable though highly air-sensitive crystalline solids. The dark brown color of the samarium dcrivativcs in solution closely resembles the brown coloration of the related (C, Me, & Sm(DAD) complexes [??I. All three compounds have been charncterizcd by spectroscopic methods. The NMR spcctru (I l-l and ’ ’Yh) R?VCiikd interesting diffcrenccs in the bonding ~lWtk!s of the coordin;Wd diazadicne ligands. 111 the cast’
+
Me&i
of the samarium derivatives 1 and 2. most of the proton NMR resonances originating from the coordinated diazadiene ligands exhibit very strong paramagnetic shifts. For example, broad peaks at 6 -182 and -226 ppm are observed for the methine protons of the tBuN=CHCH=NrBu ligand in 1. These unusual chemical shifts are typical for a combined effect of the paramagnetism of the metal ion and the radical anion of the ligand [ 19,20,22]. Thus, the ’H NMR results clearly show. that the samarium derivatives 1 and 2 should be formulated as Sm3+ complexes of the DAD radical anions. In marked contrast. all ‘H NMR resonances of the ytterbium complex 3 appear in the ‘normal’ range and show no significant paramagnetic shifts. This behavior is compatible only with the presence of divalent ytterbium, as Yb’+ is diamagnetic. The formulation of 3 as an organoytterbiumW complex is further confirmed by the fact that a “‘Yb{’ H} NMR spectrum could be recorded. “’ Yb NMR spectroscopy is restricted to diamagnetic ytterbium(I1) compounds [3 1.321. In this case, a single resonance at 224.3 ppm with a line width at half intensity of 55 Hz is observed. Thus, the chemical shift is somewhere between the range typical for Yb’+ complexes with carbocyclic VTligands (e.g.. 0 ppm for (C.5Me5),Yb(THF), which is used as the internal standard [3l]) and complexes containing only N-donor ligiulds (cu. 700-800 ppm [33]). In this sense, the “‘Yb chemical shift further confirms the formulation of 3 as (COT ’ )Yh”[PhN=C(Me)C(Mel=NPh]. The observed differences in the hondinF m(jdcs 01’ the dii~~udknc ligimds CiIn 17~ c!xpli\ined by the dif’l’cront electronic properties 01’the Ln2 ’ ions. Sm’ ’ is a ~ILKII strong
Ln
Me3S
\ R’
f H2
R
3:R=Ph,R’=Me 2:R=Ph,R’=Me Scheme
I. Preparation of the (cyclooct~~tet~~nyI)lanthanidediurrdiene complexes I-3.
O’qz:Z- ‘(IIaiJN=H3jj3=NIIal ‘H I ‘ZH S’d[ [ = “‘fi ‘4) 0’28 I - ‘(H-, LO3 ‘H Z ‘ZH Zl = “‘/I 'lq)p6'9-
y :(%4H~) tiWN H I ‘[OOI ‘:H’3] LS ‘[8l ‘faW!S] CL ‘[Xl ‘+H3H3=Nn81] Lh ‘[9l ‘+ntUN=H3H3=N”8J] ‘ #‘El1 N = H3H3= NnfU)uJS] 69 I ?? ( I L‘ / 111 : ( A a ‘1 U! Clt’ I( I’/ ‘la’) OL) SW-13 ‘(“1 SLE ‘(M) S9P ‘(WI ZSS ‘(u.‘) 009 ‘(YS M) 369 ‘(U’) OZL ‘(M) 8PL ‘(“) I8L ‘(5) I08 ‘(4 s”) 8E8 ‘(!I” s) Z06 ‘(W) IL‘6 ‘(4 S”) OZOI ‘(U’) Pt’Ol ‘(.“I S*) Z60I ‘(qs u’) t’SI I ‘(q” M) 891 I ‘(“*I 6PZI ‘(“) I9Zl ‘(M) EOEl ‘(M) OlPl :(,-‘.“3) (IofnN) tII ‘3/Jc’ti ‘N iZ.8 ‘H :L’ES ‘3 :‘pDlI?s ($‘6E9) UJS’!SO’N t-t-H “3 ’1‘p ‘N :z’(j ‘H :L’~s ‘3 :punod ‘&g9! *d-W ‘pgos uaa&anlq y.n?p n se 1 JO (.yJLp) Y ZE’I p-10~~001 wnrmh Japun pa!ip pm (lug OZ) aunxaq ~J!M a3y pm (1u.101) auanlol qJ!M 33!M1 paysI?M S!anp!S~lal~~WU/hp 01 palwodma s! awllg aql pun p!a Jailg alya3 ~0 JaAcl u!ql I? qdnoJqi pa~ailg s! aJnlx!iu uoy3aaJ aq& msahlowp leialu papuadsns aql JO IJnd JO@I ayl pw sdolamp uoym~lo~ *m)i?Jadiua]
‘(M) OSP ‘(u.‘) Z6P ‘(M) IOS ‘(M) t’t’9 ‘(“1 6S9 ‘(“*) t’ZL ‘(“A) 6t’L ‘(UJ) IO8 ‘(U’) SZ8 ‘(u’) Z16 ‘(qs m) Pt’6 ‘(qs s) l L6 ‘(sdi) P86 ‘(qs S) t’66 ‘(4 “) L60 I ‘(“) DSI I ‘(qs w) 69 I I ‘(qs u) CSZI ‘(“) Z9Z I ‘(M) SOt‘I ‘(A) 695 I ‘(M) I S6l I(, 33) (IO!-“N) Ill ‘%8X ‘N :9’9 ‘H :6’SS ‘3 :‘pDlQ (O’Ot’L) qAc!SO”NX’H t13 ‘O’p ‘N :O’L ‘H :p’SS ‘3 :puno~ 3,881 -d-W ~~t?xaq/~~~ UIOJ~pazq -lnlsAmaJ aq UF~rl3y~ ?? pgos umoJq-uaaJ3 ?? ay!suas-J!R Alq&q I? st? 8 LL’O pla!/C 0) ;l~dH ~UJ 01 pur! ‘JapMod (l0UU.U()'p) qA (~OUUl S’o) d 8L’O “H “f(&aW)-O’l 2 00’I ‘YdN =(aW D(aW D= Nqd (l”U’UJ 0’0) 3 S6’0 ~pW~iql?UI? apI?NISl?M puncrdum S!ljL umJ_~';3U!lJI?]S
8 :ei')zO.0 ‘(nal
-w&j (ZH c;s = % ‘“) t”Pz’L 9 :( “CJY3/AHU XWN tiWN ‘IA,,, .wdd (s) Z-t- 8 :( ‘a”a/dHL) ‘SK wdd (’ Ha ‘H q ‘s) ZO’O ‘( ‘aW!S ‘l-l 8 I ‘s) ZI’O ‘(H- t LO3 ‘H 9 ‘u,l) OS’S_SO’9‘(‘H “3-M Jo -II ‘H p ‘w)
6P’9-C6.9 ‘(‘H’3 -d ‘H Z ‘u) E6’9-61 ‘L ‘(‘H “3-M lo -0 ‘H p ‘u.‘) (XL-6t”L 9 :( %IH.L) tlWN H, ‘[89 ‘:‘aW!S] EL ‘[96 ‘:‘H1’3] LL ‘[ZL ‘fHNqd] E6 ‘[OOI ‘+aWI)Nqd] 9Pl b[9 “Hb-+( ,LO3)] LOZ #I I ‘[OZ ‘;aW;!S] '[z“H ‘3+( . ,LO3)] ZZZ ‘[S ‘+~dN(WD(W)3Nqd] f3EZ :( J/
‘lu!
‘I=)
L’/ 111 ‘(Aa
(IL)
sbi-12
'(H-, 103
'H Z 'ZH 4 = "'d
'Jq) $t"p-- '("aW!S 'H
‘H 8 I ‘“) I z’ I ‘(H-
* L0.J
‘H z ‘“) t’8.L
uMO.l()~.ll?p ,7SU31U!UI!';riU~l . s!ql dtyna lUOO1 ]I?Sh?p t‘10.1p3ll!lSS! AHL
IllI ()()I U! '13;7H thll
01 PIN? h.Iap/wd Nls (~oWUl s’p) 3 #J() bSHHJ’(!S’3W) -VI (P’u’ 0%) s 00’1 “‘8lN=H3H3=N”81 (low w 0-c) d L9.0 Jo 3inlxy.u v
‘rudd (“I 9’Z- 8 :(?l”3/AHU IlWN !S,,, ‘wdd (H -..L03’HZb,zH8El= “‘,I ‘-“I) SC’!+ ‘(H-, .LO3 ‘H Z’ZHO8l= ; ! ’,t ‘Jq) SO’PZ- ‘(H- r .LO3 ‘H Z ‘“) Z9’8‘(‘aW!S ‘H 81 'S) t‘()'()'(3w 'H 9 ‘S) I()'() '('H"3-tl 'H Z 'ZH Et'= "%I
'19 S) z6.t '('H'a-111'H p 'ZH
OZI = “‘ti '1s)()I'LE‘(SH"3-" 'H p ‘ZH mc = ;'%1 88’LP 9 :(%AH.L) IIWN H I ‘[VZ ’:‘aW!S] EL ‘[96 '1‘I) ‘,jH”3] LL ‘[OOI ‘+aW3Nqd] 811 781 ‘:aW’!S] 9PI ‘[8L “Hb-+( vLOa)] LOZ b[ZZ‘+qdN(aW)3(aWDNqd] 8EZ ‘[Zl b+( 4 LO311 8PZ ‘[Z ‘Nqd-qd-AHL -+ W] 89t7 :( 35 ‘lu! IaJ) L‘/ 111:(A3 OL) Sfl-Ig ‘(“) 68E ‘(M) 969 ‘(u) IZL ‘(W) SPL ‘(“A) 008 ‘(s) 9t‘8 ‘(‘J’) E98 ‘(qs m) SO01 ‘(Jq s) IZOI ‘(qs “) 8LOI ‘(Jq sA) S6Ol ‘(uJ) ZSl I ‘(Ml 69 I I ‘(“A) LPZ I ‘(“A) I9Z I ‘(M) OOE1 ‘(qs “1 68t7l ‘(M) 90s I ‘(U’) L8S I :( I 3’3) (lo!-nN) 2iJ ‘%O’P ‘N :8’9 ‘H :L’LS ‘3 :‘pDlt?a (t”LOL) LIJS‘!SO”N ‘+H “3 ‘E’P ‘N : l ‘L ‘H :c’9S ‘3 :punod ‘3,801 -d-W SIZES& UMOJq Wp
se Z (3/3Ep)s IZ'I PaplOJJI?"@H
8w
()I
PIE *lapMod UIS (l0UN.US'P) s 89.0 ‘XHX3;(!s"a~)-~'~ (louJUJ (louIur03) d 00’I ‘qdN=(aW)3(aW)3=Nqd 0%) = S6’0 JO uoymi aqi ‘Jauum lqp.I!s R Ul
'ludd("1 L'@ S
Udd
(“fllN=r’-I3/f3=Nn81
:(“a”3/dH~) ‘H
HWN !S,_
I ‘ZH ()f.Jp = +I
Qqj
-sa.xnpaaoJd aJnlwal!l 01 %.HplO3X paicdaid aJaM [s] qdN =(aW)a(aW)a=Nqd PuE [S] nHJN=H3H3=Nn81 ‘[SZ] XHX3c(!S”aW)-P‘I slyaiew %y.~ws aqL .par\!amJ SB pasn pm q3pplv u10.g paseqmd aJaM siapMod qA pue UIS *uaiiuyGD ~0 /Cl!sraA!un ‘/drjsyaq3 +?%ou J JO lualulmdaa aql Jo Aioieioqvl le3yAlsuV :sas/Clme lrziuawalg ‘(;>,ZE ‘%IH.L)qA’( ‘aW ‘3) ‘ZHW S9LXP) OSZ-WV JaT’J~ IWN ‘IA,,, ‘(3,ZC ‘SW1 ‘ZHW 09P’6L) OSZ-WV J=fma
:wxdS
aWN
!s,;:
‘(&,z~
“lx3
SwL
‘ZHW
()sz)
13yIllg PUI?AS 08 dM 13yIIlfl muads 8WN ()Sz-WV HI ‘sys!p 18~ uaamiaq sllnlu lo[nN ‘L Su pea-o!fl pm 08 I JalawoJlaads iauqa-ugiad mlaads YJ ‘asn 01 mud c~ iapun pa#w!p IclqsaJ~ pm auouaqdozuaq/r?N Jam paup AllnJam aJaM slua~los -sanbluqaal xoq-hp pue awl yualq3S p.xepu~is 3qsn a.m~s!ow pur! J!VJO uop -nlma snoio3!i Japun in0 paw.3 aJaM suoyeai llV
msagm!iap unglues aql U! @peaJ aiow qmu mm 01 palDadxa s! aVa paiwpJoo3 aqi 01 uo! apyqwl lRiiua3 aql UOJJ 13~ uomala u1?‘snqL -[vE] +;qA ueqi lua% duypai -SUE4
Acknowledgements We thank the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie and the Otto-vonGuericke-Universitt Magdeburg for financial support of this work. Generous support by Professor Herbert W. Roesky, Gijttingen, is also gratefully acknowledged.
References [II P. Porembu. U. ReiUmann. M. Noltemeyer, H.-G. Schmidt. F.T. Edelmann. J. Organomet. Chem.. in press.
El K. Vrieze. G. van Koten, Adv. Organomet. Chem. 2 I ( 1982) 151.
Dl H. tom Dieck. C. Munz. J. Ehlers. in: H. Werner. G. Erker (Eds.). Organometallics in Organic Synthesis. Vol. 3. Springer. Heidelberg. 1989. p. 3 I. I41 K. Vrieze. J. Organomet, Chem. IOU (1986) 307. H. Bock. H. tom Dieck. Chem. Ber. IO0 ( 1967) 228. t J. Schulz. B. Richter. R. Goddard. C. Ktiper. Chem. Ber. 126 (1993) 57. 171 M.G. Gardiner. G.R. Hanson. M.J. Henderson. F.C. Lee. C.L. Raston. Inorg. Chem. 33 (1994) 2456. WI F.G.N. Cloke. C.I. Dalhy. M.J. Henderson. P.B. Hitchcock. C.H.L. Kennard. R.N. Lamb. C.L. Raston. J. Chem. Sot.. Chem. Commun. ( 1990) 1394. [‘)I F.G.N. Cloke. G.R. Hanson. M.J. t lenderson. P.B. Hitchcoch. C.L. Raston, J. Chem. Sot.. Chem. Commun. ( 1989) 1002. WI K.-H. Thiele. V. Lorenz. G. Thiele. P. Ziinnchen. J. Schob. Angew. Chcm. I06 ( 1994) 1461, (1 II K.-H. Thicle, V. Lorcnl. G. Thiele. P. Ziinnchcn. J. Sch&. Anpw. Chem.. ha Ed. En@. 33 ( 1994) 1372. WI A. Schob.. K.-H. Thicle. J. Schob. R. Weimann. J. Orgxmome~. Chcm. $01 (1005) 19.5. ml C-l.bn~ Ditch. J, Ricpcr, G. F~ndcsacb. Inorg. C‘him. Acla 177
2;
( I000) 1‘11,
iI41 W.A.
Herrmann. M. Denk, W. Scherer. F.-R Klinpan. J. Organomet. Chem. 444 ( 199.3) C2 I. ml H. Giirls. B. Neumiiller. A. Scholz. J. Scholr.. A-gew. Chem. I07 (1995) 732. [I61 H. G&Is. B. Neumi,iller, A. Scholz. J. Scholz. Angew. Chem.. lnt. Ed. En@. 34 (1995) 673. iI71 B. Richter. J. Scholz. J. Sieler, K.-H. Thiele. Angew. Chem. I07 ( I9951 2865. and references cited therein. [M B. Richter. J. Scholz, J. Sieler. K.-H. Thiele. Angew. Chem.. Int. Ed, Engl. 34 (1995) 2865, and references cited therein. 1191 F.G.N. Cloke, H.C. de Lemos. A.A. Sameh. J. Chem. Sot.. Chem. Commun. ( 1986) 53. PO1 F.G.N. Cloke, H.C. de Lemos and A.A. Sameh. Chem. Sot. Rev. (1993) 17. m A.A. Trifonov. A.V. Protchenko. V.K. Cherkasov. M.N. Bochkarev. Metalloorg. Khim. 2 ( 1989) 47 I. [22] A. Recknagel, M. Noltemeyer. F.T. Edelmann. J. Orgtlnomet. Chem. 410(1991) 53. [23] A.A. Trit’onov. L.N. %akhnrov. M.N. Bochkarev. Yu.T. Struchkov. bv. Aknd. Nauk SSSR. Ser. Khim. (1994) 148. Dl N.C. Burton, F.G.N. Clokc. P.B. Hitchcock. H.C. de Lemos. A.A. Sameh. J. Chem. Sot.. Chem. Commun. ( 1989) 1462. [2s] N.C. Burton. F.G.N. Cloke. S.C.P. Joseph, H. Knramallakis. A.A. Sameh. J. Organomet. Chem. 462 (I9931 39. Da N.C. Burton. F.G.N. Cloke, P.B. Hitchcock. S.C.P. Joseph. H.C. de Lemos. J. Chem. Sot.. Dalton Trans.. in press. [271 G.B. Deacon. A.J. Koplick, T.D. Tuong. Aust. J. Chem. 37 ( 1984) 5 17. [W W.J. Evans. T.A. Ulibarri. J. Am. Chem. Sot. ICI9 (1987) 3292. PI W.J. Evans. T.P. Hanusrt. K.R. Levan. lnorg. Chim. Aclu 1IO (1985) 191. [XI] F.T. Edelmann. in: E.W. Abel. F.G.A. Stone. G. Wilkinson IEds.1. Comprehensive Organometallic Chemistry II, Vol. 4. Perganion, 1995. p. I I. ~~~1 A.G. Aver& M.A. Edelman. M.F. Lupperr. G.A. Lawless. J. Am. Chem. Sot. I I I ( 1989) 3423. [x!] 1. van den Hcndc. P.R. Hitchcock. S.A. Holmes. M.F. Lilppert. I. C~CI~I. SOC. I>nlIln~ Trans. ( 199.5) 143s. 13.11 A. Rcdm~gcl, Ph.D. Thehis. llnivcrsiry of Giitringcn. 1991. IN W .J. livan~. Polyhedron 6 ( 1187) X03.
of
Chemistry
ELSEVIER
Cyclooctatetraenyl .
complexes of the early transition metals and lanthanides IX. ’ ( Cyclooctatetraenyl) lanthanide diazadiene complexes Peter Poremba, Frank T. Edelmann
*
Abstract Complexes prepared
of’ the type (COT
in a ‘one-pot’ reaction
silyl kyclooctatricne coordinated DAD
and
’)Ln(DAD)(THF)
[Ln = Sm. Yb: COT
by treatment of elemental
+ = I.4(Me,Si),C,H,;
samarium or ytterbium
I .-I-dia/.adicnc ligands. ’H and “‘Yb
NMR
DAD
with equimolar
= l.$diaLadienes]
data show that the Sm derivatives
radical anions. while in the case of Yb the neutral DAD
have been
amounts of 1,4bis(trimethylcontain Sm’+
ions and
lipand is coordinated to divalent ytterbium. 0 1997 Elsevier
Science S.A. Kc~.~o~ls: Organolunthnnide coml4exc.s: Cyclooctatetraenyl ligands: Dkadiene
1. Introduction I ,4-Diazadienes are highly versatile, structurally tlcxible ligantls for which complcxcs arc known with various metals throughout the Periodic Table. The diazadienc (DAD) ligands can hc coordir~a~ed to a metal ion either as neutral ligands [2-61, as radical anions [7- 121, or as dianions [I%- 181. The latter coordination mode is preferred in the case of early transition metals in their high oxidation states as well as alkali metals. In recent years, DAD ligands have been frequently employed in lanthanide chemistry as well. It has been shown by NMR studies and crystallographic investigations that diazadienes are coordinated to lanthanides preferably as the radical anions. Among the first examples was the corn plex horn oleptic neodym ium(III) (rBuN=CHCH=NtBu),Nd, which was prepared by co-condensation of the ligand with neodymium vapor [ 19,201. Later, other homoleptic complexes of the type (DAD),Ln (Ln = Y. Sm. Yb) [2O] and (DAD),Ln (Ln = Y b) [2 I] have also been reported. #I, Me,), Sm(THF), readily adds diazadienes to yield samarium(III) complexes the dark brown
’ Corresponding author. ’For Part VIII. see Ref. [ 11. 0022-.32~X/97/$17.00 0 1997 Elsevier Science S.A. All rights reserved PI/ soo22-328X(97)00523-8
ligands; Samarium: Ytterbium
(C,Me,),Sm(DAD) [22]. More recently it has been shown by Scholz et al. that [(DAD)Li] units may act as complexes Cp-like ligands in orlanolanthanide [IS, 16,231. We report here the preparation and characterization of the first (cyclooctatetraenyl)land~anide diuzadienc complexes. For solubility rcrrsons the expcriments have been carried out using the I,4-bis(trimcthyIsilyl)cyclooctatetraenyl ligand, I.4-!Me,Si),C,H,?,(COT * ).
2. Results and discussion The I .4-bis(trimethylsilyl)cyclooctatetraenyl ligand has been introduced into organolanthanide chemistry by Cloke et al. [24-261. This very bulky cycloctatetraenyl dianion often provides higher solubility and better crystallinity to organolanthanide derivatives as compared to The preparation of the parent COT complexes. organolanthanide half-sandwich complexes containing one COT ’ ligands is, however, not always straightforward, as the products are often contaminated with the anionic sandwich complexes [Ln(COT * J2]- [I]. Therefore, a salt-free route to the title compounds was developed, which involves the simultaneous reaction of lanthanide metal powders with equimolar amounts of I&
bis(trimethylsilyl)-2.5.7~cyclooctatriene and diazadienes
in THF solution according to Scheme I. The reactivity of the lanthanides was enhanced by addition of a small amount of I-&Cl, which is known to activate the metal surface [27]. Only in the case of ytterbium and glyoxalno reaction bis( r-butylimine). rBuN=CHCH=NrBu, was observed. In the course of the reaction. the starting material I .4-bis(trimethylsilyl)-2,5.7-cyclooctatriene is 1,4_bis(trimethyldeprotonated to the silyl)cyclooctatetraenyl dianion (COT * )‘-. It is known from the literature that (C, Me,),Sm(II) reacts with various reagents such as cyclopentadiene, terminal acetylenes, or hydrazines under deprotonation and formation of the corresponding anionic ligands [X29]. Thus, it is plausible to assume the formation of a (COT ’)Ln(II) intermediate. which then adds the diazadiene l&and. Thz latter step has once again a precedent in (C,Me,),Sm(II) chemistry [Z]. The proposed reaction pathway is supported by the fact, that the reaction was successful only with samarium and ytterbium, which are known to have a rich organolanthanide(I1) chemistry [30]. The preparation fails in the case of other lanthanide elements such as praseodymium or neodymium. which are much more difficult to reduce. All three diazadiene complexes are isolated as deeply colored, thermally stable though highly air-sensitive crystalline solids. The dark brown color of the samarium dcrivativcs in solution closely resembles the brown coloration of the related (C, Me, & Sm(DAD) complexes [??I. All three compounds have been charncterizcd by spectroscopic methods. The NMR spcctru (I l-l and ’ ’Yh) R?VCiikd interesting diffcrenccs in the bonding ~lWtk!s of the coordin;Wd diazadicne ligands. 111 the cast’
+
Me&i
of the samarium derivatives 1 and 2. most of the proton NMR resonances originating from the coordinated diazadiene ligands exhibit very strong paramagnetic shifts. For example, broad peaks at 6 -182 and -226 ppm are observed for the methine protons of the tBuN=CHCH=NrBu ligand in 1. These unusual chemical shifts are typical for a combined effect of the paramagnetism of the metal ion and the radical anion of the ligand [ 19,20,22]. Thus, the ’H NMR results clearly show. that the samarium derivatives 1 and 2 should be formulated as Sm3+ complexes of the DAD radical anions. In marked contrast. all ‘H NMR resonances of the ytterbium complex 3 appear in the ‘normal’ range and show no significant paramagnetic shifts. This behavior is compatible only with the presence of divalent ytterbium, as Yb’+ is diamagnetic. The formulation of 3 as an organoytterbiumW complex is further confirmed by the fact that a “‘Yb{’ H} NMR spectrum could be recorded. “’ Yb NMR spectroscopy is restricted to diamagnetic ytterbium(I1) compounds [3 1.321. In this case, a single resonance at 224.3 ppm with a line width at half intensity of 55 Hz is observed. Thus, the chemical shift is somewhere between the range typical for Yb’+ complexes with carbocyclic VTligands (e.g.. 0 ppm for (C.5Me5),Yb(THF), which is used as the internal standard [3l]) and complexes containing only N-donor ligiulds (cu. 700-800 ppm [33]). In this sense, the “‘Yb chemical shift further confirms the formulation of 3 as (COT ’ )Yh”[PhN=C(Me)C(Mel=NPh]. The observed differences in the hondinF m(jdcs 01’ the dii~~udknc ligimds CiIn 17~ c!xpli\ined by the dif’l’cront electronic properties 01’the Ln2 ’ ions. Sm’ ’ is a ~ILKII strong
Ln
Me3S
\ R’
f H2
R
3:R=Ph,R’=Me 2:R=Ph,R’=Me Scheme
I. Preparation of the (cyclooct~~tet~~nyI)lanthanidediurrdiene complexes I-3.
O’qz:Z- ‘(IIaiJN=H3jj3=NIIal ‘H I ‘ZH S’d[ [ = “‘fi ‘4) 0’28 I - ‘(H-, LO3 ‘H Z ‘ZH Zl = “‘/I 'lq)p6'9-
y :(%4H~) tiWN H I ‘[OOI ‘:H’3] LS ‘[8l ‘faW!S] CL ‘[Xl ‘+H3H3=Nn81] Lh ‘[9l ‘+ntUN=H3H3=N”8J] ‘ #‘El1 N = H3H3= NnfU)uJS] 69 I ?? ( I L‘ / 111 : ( A a ‘1 U! Clt’ I( I’/ ‘la’) OL) SW-13 ‘(“1 SLE ‘(M) S9P ‘(WI ZSS ‘(u.‘) 009 ‘(YS M) 369 ‘(U’) OZL ‘(M) 8PL ‘(“) I8L ‘(5) I08 ‘(4 s”) 8E8 ‘(!I” s) Z06 ‘(W) IL‘6 ‘(4 S”) OZOI ‘(U’) Pt’Ol ‘(.“I S*) Z60I ‘(qs u’) t’SI I ‘(q” M) 891 I ‘(“*I 6PZI ‘(“) I9Zl ‘(M) EOEl ‘(M) OlPl :(,-‘.“3) (IofnN) tII ‘3/Jc’ti ‘N iZ.8 ‘H :L’ES ‘3 :‘pDlI?s ($‘6E9) UJS’!SO’N t-t-H “3 ’1‘p ‘N :z’(j ‘H :L’~s ‘3 :punod ‘&g9! *d-W ‘pgos uaa&anlq y.n?p n se 1 JO (.yJLp) Y ZE’I p-10~~001 wnrmh Japun pa!ip pm (lug OZ) aunxaq ~J!M a3y pm (1u.101) auanlol qJ!M 33!M1 paysI?M S!anp!S~lal~~WU/hp 01 palwodma s! awllg aql pun p!a Jailg alya3 ~0 JaAcl u!ql I? qdnoJqi pa~ailg s! aJnlx!iu uoy3aaJ aq& msahlowp leialu papuadsns aql JO IJnd JO@I ayl pw sdolamp uoym~lo~ *m)i?Jadiua]
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8 :ei')zO.0 ‘(nal
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'ludd("1 L'@ S
Udd
(“fllN=r’-I3/f3=Nn81
:(“a”3/dH~) ‘H
HWN !S,_
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Qqj
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msagm!iap unglues aql U! @peaJ aiow qmu mm 01 palDadxa s! aVa paiwpJoo3 aqi 01 uo! apyqwl lRiiua3 aql UOJJ 13~ uomala u1?‘snqL -[vE] +;qA ueqi lua% duypai -SUE4
Acknowledgements We thank the Deutsche Forschungsgemeinschaft, the Fonds der Chemischen Industrie and the Otto-vonGuericke-Universitt Magdeburg for financial support of this work. Generous support by Professor Herbert W. Roesky, Gijttingen, is also gratefully acknowledged.
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