Synthesis and second-order nonlinear optical properties of donor-acceptor

582

Organometallics 1999, 18, 582-597

Syn th esis a n d Secon d -Or d er Non lin ea r Op tica l

P r op er ties of Don or -Accep tor σ-Alk yn yl a n d σ-En yn yl

In d en ylr u th en iu m (II) Com p lexes. X-r a y Cr ysta l

Str u ctu r es of

[Ru {CtCCHdC(C₆H₄NO₂-3)₂}(η⁵-C₉H₇)(P P h ₃)₂] a n d

(EE)-[Ru {CtC(CHdCH)₂-C₆H₄NO₂-4}(η⁵-C₉H₇)(P P h ₃)₂]

Victorio Cadierno, Salvador Conejero, M. Pilar Gamasa, and J ose´ Gimeno*^,†

Departamento de Quı´mica Orga´nica e Inorga´nica, Instituto Universitario de Quı´mica

Organometa´lica “Enrique Moles” (Unidad Asociada al CSIC), Facultad de Qu´ımica,

Universidad de Oviedo, E-33071 Oviedo, Spain

Inge Asselberghs, Stephan Houbrechts,^‡Koen Clays, and Andre´ Persoons

Laboratory of Chemical and Biological Dynamics, Center for Research on Molecular

Electronics and Photonics, University of Leuven, B-3001 Leuven, Belgium

J avier Borge and Santiago Garc´ıa-Granda

Departamento de Quı´mica Fı´sica y Analı´tica, Facultad de Qu´ımica, Universidad de Oviedo,

E-33071 Oviedo, Spain

Received August 5, 1998

σ-Alkynyl complexes [Ru(CtC-C₆H₄R-4)(η⁵-C₉H₇)L₂] (L ) PPh₃, R ) NO₂(3a ), CtC-C₆H₄-

NO₂-4 (4), NdCH-C₆H₄NO₂-4 (5); L₂) 1,2-bis(diphenylphosphino)ethane (dppe), R ) NO₂(3b);

L₂) bis(diphenylphosphino)methane (dppm), R ) NO₂(3c)) have been prepared by reaction of

[RuCl(η⁵-C₉H₇)L₂] (1a -c) with HCtC-C₆H₄R-4 and NaPF₆, via deprotonation of the correspond-

ing intermediate vinylidene derivatives. The treatment of the alkynyl-phosphonio complex [Ru-

{CtCCH₂(PPh₃)}(η⁵-C₉H₇)(PPh₃)₂][PF₆] (6) with LiⁿBu and the appropriate aldehyde or ketone

yields, via Wittig type reactions, σ-enynyl complexes [Ru{CtCCHdCR¹(CHdCH)_nR²}(η⁵-C₉H₇)-

(PPh₃)₂] (n ) 0, R¹) H, R²) C₆H₄NO₂-4 (7a ), C₄H₂ONO₂-3,4 (8a ), C₄H₂SNO₂-3,4 (8b), C₆H₄-

CN-4 (13), C₅H₄N-4 (16); n ) 0, R¹) R²) C₆H₄NO₂-3 (9); n ) 1, R¹) H, R²) C₆H₄NO₂-4 (7b))

isolated as mixtures of the corresponding E and Z stereoisomers. The structures of complexes 7b

and 9 have been confirmed by X-ray diffraction. Structural data in the solid state as well as in

solution (¹³C{¹H} NMR) show an extensive electronic delocalization between the donor fragment

[Ru(η⁵-C₉H₇)(PPh₃)₂] and the acceptor nitroaryl group. In accordance with this, values of reso-

nantly enhanced molecular quadratic hyperpolarizabilities (â) for these donor-acceptor derivatives

(â_{1064 nm}) 100-1320 × 10^-30esu), determined by the hyper-Rayleigh scattering technique (HRS)

at 1064 nm which are dependent on the molecular design of the bridged enynyl chain, are

significantly larger than those of their analogous organic chromophores. Mixed-valence bimetallic

donor-acceptor derivatives [(η⁵-C₉H₇)(PPh₃)₂Ru{(µ-CtN)ML₅}][CF₃SO₃]_n(n ) 0, ML₅) Cr(CO)₅

(11a ), W(CO)₅(11b); n ) 3, ML₅) Ru(NH₃)₅(12)), [(η⁵-C₉H₇)(PPh₃)₂Ru{(µ-CtCCHdCH-C₆H₄Ct

N-4)ML₅}][CF₃SO₃]_n(n ) 0, ML₅) Cr(CO)₅[(E, Z)-14a ], W(CO)₅[(E, Z)-14b]; n ) 3, ML₅

)

Ru(NH₃)₅[(E, Z)-15] and [(η⁵-C₉H₇)(PPh₃)₂Ru{(µ-CtCCHdCH-C₅H₄N-4)M(CO)₅}] (M ) Cr [(E)-

17a ], W [(E)-17b]) have also been prepared in high yields. Static quadratic hyperpolarizabilities

values of these derivatives (â_o) 10-150 × 10^-30esu) surpass the largest reported to date for

bimetallic compounds. The bimetallic σ-enynyl complex [Ru(CtCCHdCH(η⁵-C₅H₄)Fe(η⁵-C₅H₅)-

(η⁵-C₉H₇)(PPh₃)₂] [(E)-18] was obtained stereoselectively from the alkynyl-phosphonio complex

6, LiⁿBu, and {η⁵-C₅H₄(CHO)}Fe(η⁵-C₅H₅). Protonation of (E)-18 with HBF₄yields the vinylidene

derivative [Ru{)CdC(H)CHdCH(η⁵-C₅H₄)Fe(η⁵-C₅H₅)}(η⁵-C₉H₇)(PPh₃)₂][BF₄] (19). Quadratic

hyperpolarizabilities for these ruthenium(II)-iron(II) bimetallic complexes are also reported.

In tr od u ction

The search for suitable materials displaying second-

order nonlinear optical (NLO) properties is the focus of

much current research activity due to their potential

applications in optoelectronics, telecommunications, and

optical storage devices.¹A great deal of work has been

carried out on organic molecules which has enabled the

development of certain structure-NLO efficiency rela-

tionships. Thus, it is well-known that organic molecules

^†E-mail: jgh@sauron.quimica.uniovi.es.

^‡Present address: Frontier Research Program, RIKEN, 2-1 Hiro-

sawa, Wako-shi, Saitama 351-01, J apan.

Publication on Web 01/22/1999

Donor-Acceptor Indenylruthenium(II) Complexes

Organometallics, Vol. 18, No. 4, 1999 583

containing donor-acceptor-substituted π-conjugated sys-

tems exhibit large second-order NLO properties.²The

optical nonlinearities of organometallic compounds have

been actively studied only recently, but their potential

as novel NLO materials is yet to be fully explored.

Enhanced second-order NLO reponses have also been

found on organometallic systems with a donor-bridge-

acceptor composition.³In these complexes the metal

fragment can act as an electron donor,⁴as an electron

acceptor group,⁵or as part of a polarizable bridge.⁶

Morover, the incorporation of the metal in the same

plane as the π-conjugated system and the potential

introduction of metal-carbon multiple-bond character

has been suggested to enhance the NLO reponse.^4c

Attention has turned to σ-alkynyl complexes which

certainly satisfy this molecular design. In this respect,

Humphrey et al. have reported the extremely large

molecular second-order responses of several 18 valence

electron ruthenium(II)⁷and nickel(II)⁸complexes and

14 valence electron gold(I)⁹σ-alkynyl derivatives in

which the metal fragments act as electron donor groups.

The quadratic hyperpolarizabilities (â) of these com-

plexes revealed the second-order NLO series [Ru] > [Ni]

> [Au], with a great dependence of the NLO response

on the structure and lengthening of the alkynyl skel-

eton.

potential utility of these derivatives, we wondered about

the possible effect of this metallic auxiliary on second-

order NLO materials. Thus, in this paper we report the

synthesis of novel donor-acceptor indenylruthenium-

(II) complexes which display large quadratic hyperpo-

larizabilities (â). We have investigated systematically

series of compounds of the following types (see Chart

1): (i) σ-alkynyl and σ-enynyl complexes (A) containing

nitro or cyano substituents at the end of the hydrocar-

bon chain, (ii) ruthenium(II)-ruthenium(III) and ru-

thenium(II)-chromium(0) or tungsten(0) bimetallic com-

plexes (B) in which a donor indenylruthenium(II) moiety

and an acceptor metal fragment are bridged by a cyano

group or an enynyl N-functionalized system, and (iii)

ruthenium(II)-iron(II) bimetallic complexes (C) in which

an indenylruthenium(II) moiety and a ferrocenyl frag-

ment are bridged by an enynyl or vinylvinylidene

unsaturated chain. Part of this work has been previ-

ously communicated.¹¹

Resu lts a n d Discu ssion

σ-Alk yn yl Don or -Accep tor Com p lexes [Ru (Ct

C-C₆H₄NO₂-4) (η⁵-C₉H₇)L₂] (L₂) 2P P h ₃(3a ), 1,2

bis(d ip h en ylp h osp h in o)eth a n e (d p p e) (3b), bis(d i-

p h en ylp h osp h in o)m eth a n e (d p p m ) (3c)) a n d [Ru -

(CtC-C₆H₄R-4)(η⁵-C₉H₇)(P P h ₃)₂] (R ) CtC-C₆H₄-

NO₂-4 (4), NdCH-C₆H₄NO₂-4 (5)). The reaction of

complexes [RuCl(η⁵-C₉H₇)L₂] (L₂) 2PPh₃(1a ), dppe

(1b), dppm (1c)) with 4-ethynylnitrobenzene in refluxing

methanol, and in the presence of NaPF₆, results in the

formation of the vinylidene complexes [Ru{)CdC(H)-

C₆H₄NO₂-4}(η⁵-C₉H₇)L₂][PF₆] (2a -c), which have been

During recent years we have been involved in the

study of the reactivity of unsaturated carbene complexes

containing the electron-rich indenylruthenium(II) moi-

ety [Ru(η⁵-C₉H₇)(PPh₃)₂] as a metal auxiliary, and we

have described the synthesis of a large variety of

functionalized (σ-alkynyl)ruthenium(II) complexes.¹⁰

Since we are specially interested in exploiting the

(1) (a) Prasad, P. N.; Williams, D. J . Introduction to Nonlinear

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(2) For example, see: (a) Williams, D. J . Angew. Chem., Int. Ed.

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10643.

(3) (a) Nalwa, H. S. Appl. Organomet. Chem. 1991, 5, 349. (b) Long,

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McDonagh, A. M.; Humphrey, M. G.; Samoc, M. Adv. Organomet.

Chem. 1998, 42, 291. (d) Denning, R. G. J . Mater. Chem. 1995, 5, 365.

(4) The most extensively studied system is that of ferrocenyl

derivatives. For example, see: (a) Green, M. L. H.; Marder, S. R.;

Thompson, M. E.; Bandy, J . A.; Bloor, D.; Kolinsky, P. V.; J ones, R. J .

Nature 1987, 330, 360. (b) Tiemann, B. G.; Marder, S. R.; Perry, J .

W.; Cheng, L.-T. Chem. Mater. 1990, 2, 690. (c) Calabrese, J . C.; Cheng,

L.-T.; Green, J . C.; Marder, S. R.; Tam, W. J . Am. Chem. Soc. 1991,

113, 7227. (d) Yuan, Z.; Taylor, N. J .; Sun, Y.; Marder, T. B. J .

Organomet. Chem. 1993, 449, 27. (e) Blanchard-Desce, M.; Runser,

C.; Fort, A.; Barzoukas, M.; Lehn, J .-M.; Bloy, V.; Alain, V. Chem. Phys.

1995, 199, 253. (f) Hagenau, U.; Heck, J .; Hendricks, E.; Persoons, A.;

Schuld, T.; Wong, H. Inorg. Chem. 1996, 35, 7863.

(5) Metal carbonyl fragments have been used as electron-acceptor

groups. For example, see: (a) Cheng, L.-T.; Tam, W.; Eaton, D. F.

Organometallics 1990, 9, 2856. (b) Cheng, L.-T.; Tam, W.; Meredith,

G. R.; Marder, S. R. Mol. Cryst. Liq. Cryst. 1990, 189, 137. (c) Maiorana,

S.; Papagni, A.; Licandro, E.; Persoons, A.; Clays, K.; Houbrechts, S.;

Porzio, W. Gazz. Chim. Ital. 1995, 125, 377. (d) Lacroix, P. G.; Lin,

W.; Wong, G. K. Chem. Mater. 1995, 7, 1293. (e) Roth, G.; Fischer, H.;

Meyer-Friedrichsen, T.; Heck, J .; Houbrechts, S.; Persoons, A. Orga-

nometallics 1998, 17, 1511.

(7) [Ru(η⁵-C₅H₅)(PR₃)₂]: (a) Whittall, I. R.; Humphrey, M. G.;

Houbrechts, S.; Persoons, A. Organometallics 1996, 15, 1935. (b)

Naulty, R. H.; Cifuentes, M. P.; Humphrey, M. G.; Houbrechts, S.;

Boutton, C.; Persoons, A.; Heath, G. A.; Hockless, D. C. R.; Luther-

Davies, B.; Samoc, M. J . Chem. Soc., Dalton Trans. 1997, 4167. (c)

Wu, I.-Y.; Lin, J . T.; Luo, J .; Sun, S.-S.; Li, C.-S.; Lin, K. J .; Tsai, C.;

Hsu, C.-C.; Lin, J .-L. Organometallics 1997, 16, 2038. (d) Whittall, I.

R.; Cifuentes, M. P.; Humphrey, M. G.; Luther-Davies, B.; Samoc, M.;

Houbrechts, S.; Persoons, A.; Heath, G. A.; Hockless, D. C. R. J .

Organomet. Chem. 1997, 549, 127. (e) Wu, I.-Y.; Lin, J . T.; Luo, J .; Li,

C.-S.; Tsai, C.; Wen, Y. S.; Hsu, C.-C.; Yeh, F.-F.; Liou, S. Organome-

tallics 1998, 17, 2188. trans-[RuCl(dppm)₂]: (f) Whittall, I. R.; Hum-

phrey, M. G.; Houbrechts, S.; Maes, J .; Persoons, A.; Schmid, S.;

Hockless, D. C. R. J . Organomet. Chem. 1997, 544, 277. (g) Whittall,

I. R.; Humphrey, M. G.; Hockless, D. C. R.; Skelton, B. W.; White, A.

L. H. Organometallics 1995, 14, 3970. (h) Naulty, R. H.; McDonagh A.

M.; Whittall, I. R.; Cifuentes, M. P.; Humphrey, M. G.; Houbrechts,

S.; Maes, J .; Persoons, A.; Schmid, S.; Hockless, D. C. R. J . Organomet.

Chem. 1998, 563, 137.

(8) [Ni(η⁵-C₅H₅)(PPh₃)]: Whittall, I. R.; Cifuentes, M. P.; Humphrey,

M. G.; Luther-Davies, B.; Samoc, M., Houbrechts, S.; Persoons, A.;

Heath, G. A.; Bogsa´nyi, D. Organometallics 1997, 16, 2631.

(9) [Au(PPh₃)]: Whittall, I. R.; Humphrey, M. G.; Houbrechts, S.;

Persoons, A.; Hockless, D. C. R. Organometallics 1996, 15, 5738. See

also refs 7b and 7f.

(10) (a) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Lastra, E.; Borge,

J .; Garc´ıa-Granda, S. Organometallics 1994, 13, 745. (b) Cadierno, V.;

Gamasa, M. P.; Gimeno, J .; Lastra, E. J . Organomet. Chem. 1994, 474,

C27. (c) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Borge, J .; Garc´ıa-

Granda, S. J . Chem. Soc., Chem. Commun. 1994, 2495. (d) Cadierno,

V.; Gamasa, M. P.; Gimeno, J .; Gonza´lez-Cueva, M.; Lastra, E.; Borge,

J .; Garc´ıa-Granda, S. Organometallics 1996, 15, 2137. (e) Cadierno,

V.; Gamasa, M. P.; Gimeno, J .; Borge, J .; Garc´ıa-Granda, S. Organo-

metallics 1997, 16, 3178. (f) Cadierno, V.; Gamasa, M. P.; Gimeno, J .;

Lo´pez-Gonza´lez, M. C.; Borge, J .; Garc´ıa-Granda, S. Organometallics

1997, 16, 4453. (g) Cadierno, V.; Gamasa, M. P.; Gimeno, J .; Moreto´,

J . M.; Ricart, S.; Roig, A.; Molins, E. Organometallics 1998, 17,

697.

(6) For example, see: (a) LeCours, S. M.; Guan, H.-W.; DiMagno,

S. G.; Wang, C. H.; Therien, M. J . J . Am. Chem. Soc. 1996, 118, 1497.

(b) Nguyen, P.; Lesley, G.; Marder, T. B.; Ledoux, I.; Zyss, J . Chem.

Mater. 1997, 9, 406. (c) Karki, L.; Vance, F. W.; Hupp, J . T.; LeCours,

S. M.; Therien, M. J . J . Am. Chem. Soc. 1998, 120, 2606. (d) Buey, J .;

Coco, S.; D´ıez, L.; Espinet, P.; Mart´ın-Alvarez, J . M.; Miguel, J . A.;

Garc´ıa-Granda, S.; Tesouro, A.; Ledoux, I.; Zyss, J . Organometallics

1998, 17, 1750.

(11) (a) Houbrechts, S.; Clays, K.; Persoons, A.; Cadierno, V.;

Gamasa, M. P.; Gimeno, J .; Whittall, I. R.; Humphrey, M. G. Proc.

SPIE-Int. Soc. Opt. Eng. 1996, 2852, 98. (b) Houbrechts, S.; Clays, K.;

Persoons, A.; Cadierno, V.; Gamasa, M. P.; Gimeno, J . Organometallics

1996, 15, 5266.

584 Organometallics, Vol. 18, No. 4, 1999

Cadierno et al.

Ch a r t 1

Sch em e 1

or singlet (2b,c) resonance at δ 4.38-5.34 ppm of the

RudCdCH proton and (ii) (¹³C NMR) the typical low-

field resonance of the carbenic C_R, which appears as a

triplet at δ 348.85-352.42 ppm (²J _CP) 14.7-16.5 Hz).

Compounds 2a -c can be readily deprotonated by

treatment with an excess of Al₂O₃in dichloromethane,

at room temperature, to give the donor-acceptor σ-alky-

nyl derivatives [Ru(CtC-C₆H₄NO₂-4)(η⁵-C₉H₇)L₂] (3a -

c) (42-79% yield) (Scheme 1).¹³Complexes 3a -c were

analytically and spectroscopically characterized (see

Tables 1 and 2 and Experimental Section). In particular,

IR spectra exhibit the expected ν(CtC) absorption band

in the range 2051-2060 cm^-1, and the ¹³C{¹H} NMR

spectra show the C_Rresonance which appears as a

characteristic triplet signal at δ 136.44 ppm (²J _CP) 22.0

Hz) for complex 3c and falls within the aromatic region

(δ 127.39-141.97 ppm) for complexes 3a ,b. Comparison

of these chemical shifts with that of the analogous

complex [Ru(CtC-C₆H₅)(η⁵-C₉H₇)(PPh₃)₂]^12a(δ 114.25

ppm) reveals a significant shift of the resonance to a

lower field owing to the presence of the strong electron-

withdrawing NO₂group. The C_âresonance appears in

all of the cases as a singlet in the range δ 115.13-117.77

ppm.

isolated as air-stable hexafluorophosphate salts (49-

67% yield) (Scheme 1). Spectroscopic data (IR and H,

1

³¹P{¹H}, and ¹³C{¹H} NMR) clearly reveal the presence

of the vinylidene moiety and can be compared with those

reported for other indenylruthenium(II) vinylidene com-

plexes (details are given in the Experimental Sec-

tion).^10,12The most remarkable features of the NMR

spectra are (i) (¹H NMR) the triplet (⁴J _HP) 1.5 Hz, 2a )

Treatment of [RuCl(η⁵-C₉H₇)(PPh₃)₂] (1a ) with HCt

C-C₆H₄R-4 (R ) CtC-C₆H₄NO₂-4, NdCH-C₆H₄NO₂-

4) and NaPF₆in refluxing methanol also generates

indenylruthenium(II) vinylidene complexes which were

(12) (a) Gamasa, M. P.; Gimeno, J .; Mart´ın-Vaca, B. M.; Borge, J .;

Garc´ıa-Granda, S.; Pe´rez-Carren˜o, E. Organometallics 1994, 13, 4045.

(b) Gamasa, M. P.; Gimeno, J .; Godefroy, I.; Lastra, E.; Mart´ın-Vaca,

B. M.; Garc´ıa-Granda, S.; Gutie´rrez-Rodr´ıguez, A. J . Chem. Soc.,

Dalton Trans. 1995, 1901.

(13) The deprotonation of monosubstituted vinylidene complexes

represents one of the most expeditious ways to achieve σ-alkynyl

derivatives: Bruce, M. I. Chem. Rev. 1991, 91, 197.

Donor-Acceptor Indenylruthenium(II) Complexes

Ta ble 1. ³¹P {¹H} a n d ¹H NMR Da ta for th e Don or -Accep tor σ-Alk yn yl Com p lexes^a

¹H

Organometallics, Vol. 18, No. 4, 1999 585

d

η⁵-C₉H₇

H-2 J _HH

51.50 s 4.73 d 5.53 t 2.2 6.25 m, 6.71 m 6.84-7.38 (m, PPh₃and C₆H₂H₂NO₂-4); 8.03 (d, C₆H₂H₂NO₂-4, J _HH) 8.8)

complex ³¹P{¹H} H-1,3

H-4,7, H-5,6

others

3a

3b

86.65 s 5.01 d 5.11 t 2.5 b, b

1.82 and 2.25 (m, P(CH₂)₂P); 6.49 and 7.80 (d, C₆H₄NO₂-4, J _HH) 8.8);

6.85-7.48 (m, PPh₂)

3.98 and 4.31 (m, PCH_aH_bP); 6.39 and 7.77 (d, C₆H₄NO₂-4, J _HH) 8.7);

6.92-7.45 (m, PPh₂)

3c

18.79 s 5.27 d 5.11 t 2.3 b, b

4

5

51.82 s 4.75 d 5.59 t 2.2 6.31 m, 6.70 m 6.87-7.68 (m, PPh₃and C₆H₄NO₂-4)

52.04 s 4.78 d 5.66 t 2.4 6.33 m, 6.71 m 6.84-7.84 (m, PPh₃and C₆H₄NO₂-4); 8.00 (s, dCH)

51.60 s 4.74 d 5.63 t 2.0 6.28 m, 6.72 m 6.44 (d, dCH, J _HH) 15.5); 6.83-7.40 (m, PPh₃, dCH and C₆H₂H₂NO₂-4);

7.88 (d, C₆H₂H₂NO₂-4, J _HH) 8.7)

51.48 s 4.67 d 5.50 t 2.0 6.35 m, 6.74 m 6.06 and 6.47 (d, dCH, J _HH) 11.2); 6.83-7.40 (m, PPh₃);

8.19 and 8.35 (d, C₆H₄NO₂-4, J _HH) 8.8)

(E)-7a

(Z)-7a

(EE)-7b 51.44 s 4.74 d 5.66 t 2.2 b, b

6.12-7.61 (m, PPh₃, 4 dCH and C₆H₂H₂NO₂-4);

7.87 (d, C₆H₂H₂NO₂-4, J _HH) 8.7)

6.12-7.61 (m, PPh₃, 4 dCH and C₆H₂H₂NO₂-4);

7.64 (d, C₆H₂H₂NO₂-4, J _HH) 8.7)

(ZE)-7b 52.01 s 4.68 d 5.45 t 2.2 b, b

(E)-8a

(Z)-8a

(E)-8b

9

51.41 s 4.70 d 5.56 t 2.4 6.25 m, b

51.35 s 4.70 d 5.64 t 2.5 6.33 m, b

5.43 (d, C₄HHONO₂-2,3, J _HH) 3.7); 6.15 (d, dCH, J _HH) 15.4);

6.25 (m, C₄HHONO₂-2,3);^c6.67-7.37 (m, PPh₃and dCH)

6.02 (d, dCH, J _HH) 11.0); 6.67-7.37 (m, PPh₃and dCH);

7.06 and 7.58 (d, C₄H₂ONO₂-2,3, J _HH) 3.8)

49.87 s 5.00 d 6.23 t 2.4 6.16 m, 6.68 m 6.21 (d, dCH, J _HH) 15.3); 6.32 and 7.65 (d, C₄H₂SNO₂-2,3, J _HH) 4.5);

6.88-7.33 (m, PPh₃and dCH)

49.89 s 4.73 d 5.84 t 2.2 6.01 m, b

6.52 (s, dCH); 6.63-7.24 (m, PPh₃and 3H of C₆H₄NO₂-3);

7.59 (d, C₆HH₃NO₂-3, J _HH) 7.7); 7.74 (dd, C₆HH₃NO₂-3,

J _HH) 8.1, J _HH) 1.3); 7.96 (dd, C₆HH₃NO₂-3, J _HH) 8.2, J _HH) 1.4);

8.19 and 9.55 (s, C₆HH₃NO₂-3)

(E)-13

(Z)-13

51.66 s 4.73 d 5.63 t 2.2 6.30 m, 6.71 m 6.42 (d, dCH, J _HH) 15.6); 6.76-7.45 (m, PPh₃, dCH and C₆H₄CN-4)

51.48 s 4.68 d 5.54 t 2.3 6.33 m, 6.71 m 6.03 (d, dCH, J _HH) 11.4); 6.76-7.45 (m, PPh₃, dCH and C₆H₂H₂CN-4);

8.32 (d, C₆H₂H₂CN-4, J _HH) 8.4)

(E)-14a 51.36 s 4.73 d 5.59 t 2.0 6.32 m, 6.72 m 6.42 (d, dCH, J _HH) 15.8); 6.83-7.54 (m, PPh₃, dCH and C₆H₄CN-4)

(Z)-14a 50.75 s 4.68 d 5.61 t 1.6 6.32 m, 6.72 m 6.32 (m, dCH);^c6.56 (d, C₆H₂H₂CN-4, J _HH) 8.4);

6.83-7.54 (m, PPh₃, dCH and C₆H₂H₂CN-4)

(E)-14b 51.37 s 4.73 d 5.60 t 2.0 6.30 m, 6.69 m 6.39 (d, dCH, J _HH) 15.6); 6.48 (d, C₆H₂H₂CN-4, J _HH) 8.2);

6.78-7.38 (m, PPh₃, dCH and C₆H₂H₂CN-4)

(Z)-14b 50.71 s 4.69 d 5.58 t 2.0 6.30 m, 6.69 m 5.99 (d, dCH, J _HH) 11.1); 6.78-7.38 (m, PPh₃, dCH and C₆H₂H₂CN-4);

8.23 (d, C₆H₂H₂CN-4, J _HH) 8.5)

(E)-16

51.40 s 4.74 d 5.66 t 2.2 6.29 m, 6.70 m 6.43 (d, dCH, J _HH) 15.6); 6.89-7.45 (m, PPh₃, dCH and C₅H₂H₂N-4);

8.51 (d, C₅H₂H₂N-4, J _HH) 5.9)

(E)-17a 51.92 s 4.73 d 5.62 t 2.2 6.25 m, 6.79 m 6.06 and 6.80 (d, dCH, J _HH) 15.4); 6.25 (m, C₅H₂H₂N-4);^c

6.87-7.83 (m, PPh₃and C₅H₂H₂N-4)

(E)-17b 51.02 s 4.74 d 5.65 t 2.1 6.21 m, 6.70 m 6.05 (d, dCH, J _HH) 15.4); 6.17 and 7.86 (d, C₅H₄N-4, J _HH) 6.5);

6.79-7.35 (m, PPh₃and dCH)

(E)-18

51.69 s 4.73 d 5.70 t 2.2 6.30 m, 6.68 m 4.06 (s, C₅H₅); 4.07 and 4.33 (m, C₅H₄); 6.45 (d, dCH, J _HH) 15.7);

6.59 (dt, dCH, J _HH) 15.7, J _HH) 1.6); 6.94-7.50 (m, PPh₃)

a

Spectra recorded in C₆D₆; δ in ppm and J in Hz. Abbreviations: s, singlet; d, doublet; dd, doublet of doublets; t, triplet; dt, doublet

of triplets; m, multiplet. Overlapped by PPh₃or PPh₂protons. ^cOverlapped by H-4,7 or H-5,6 protons. Legend for indenyl skeleton.

b

d

not isolated but, instead, deprotonated in situ using an

excess of Al₂O₃(4) or K₂CO₃(5) to afford the σ-alkynyl

derivatives [Ru(CtC-C₆H₄R-4)(η⁵-C₉H₇)(PPh₃)₂] (4-5)

in 51% and 60% yield, respectively (Scheme 2). Com-

plexes 4 and 5 display similar spectroscopic properties

to those of complexes 3a -c (see Tables 1 and 2 and

Experimental Section).

σ-En yn yl Don or -Accep tor Com p lexes [Ru {Ct

CCHdCR¹(CHdCH)_nR²}(η⁵-C₉H₇)(P P h ₃)₂] (n ) 0,

R¹) H, R²) C₆H₄NO₂-4 [(E, Z)-7a ], C₄H₂ONO₂-2,3

(R¹) H, Ph), containing an acidic hydrogen atom at C_γ,

are excellent substrates for Wittig reactions, leading to

the formation of new double carbon-carbon bonds, i.e.,

[Ru(CtCCR¹dCR²R³)(η⁵-C₉H₇)(PPh₃)₂].^10c,gGiven the

electron richness of the indenylruthenium(II) fragment,

we believed that it would be of interest to exploit this

methodology for the construction of novel σ-enynyl

complexes with donor-acceptor properties of interest

as materials with good NLO properties. Therefore, we

set up a series of Wittig reactions using unsaturated

aldehydes and ketones bearing the NO₂acceptor group.

The formation of the new double carbon-carbon bond

should give rise to the generation of a π-conjugated

system of a triple and double carbon-carbon bonds

[(E,Z)-8a ], C₄H₂SNO₂-2,3 [(E)-8b]; n ) 0, R¹) R²

)

C₆H₄NO₂-3 (9); n ) 1, R¹) H, R²) C₆H₄NO₂-4

[(EE,ZE)-7b]). As is well-known, Wittig type reactions

are one of the most useful procedures for the generation

of double carbon-carbon bonds in organic synthesis.¹⁴

We have previously reported that alkynyl-phosphonio

complexes [Ru{CtCCH(R¹)(PR₃)}(η⁵-C₉H₇)(PPh₃)₂][PF₆]

(14) For example, see: Kelly, S. E. In Comprehensive Organic

Synthesis; Trost, B. M., Fleming, I., Eds.; Pergamon: Oxford, 1991;

Vol. 1, p 755.

586 Organometallics, Vol. 18, No. 4, 1999

Ta ble 2. ¹³C{¹H} NMR Da ta for th e Don or -Accep tor σ-Alk yn yl Com p lexes^a

η⁵-C₉H₇

complex C-1,3 C-2 C-3a,7a ∆δ(C-3a,7a)^bC-4,7, C-5,6 Ru-C_RJ _CP

Cadierno et al.

2

C_â

others

3a

76.05 95.93 110.23

-20.47

c, c

d

117.77 127.39-129.64 (m, PPh₃, CH of C₆H₄NO₂-4 and

C of C₆H₄NO₂-4); 131.30 (s, C of C₆H₄NO₂-4)

115.13 28.84 (m, P(CH₂)₂P); 124.08-141.97 (m, PPh₂

and CH of C₆H₄NO₂-4); 138.12 and 144.03

(s, C of C₆H₄NO₂-4)

3b

71.12 93.50 108.69

-22.01

d, d

d

3c

68.42 89.96 107.33

75.10 94.86 109.16

75.12 95.49 109.51

75.96 96.06 110.41

75.58 95.81 110.60

-23.37

-21.54

-21.19

-20.29

-20.10

-20.91

d, d

f, f

136.44 t 22.0 115.18 50.30 (t, PCH₂P, J _CP) 23.4); 123.27-138.54 (m,

PPh₂and CH of C₆H₄NO₂-4); 137.41 and

143.36 (s, C of 4 C₆H₄NO₂-4)

4

125.20 t 24.4

e

88.39 and 96.73 (s, tC); 123.19-138.62 (m, PPh₃,

CH of C₆H₄and C₆H₄NO₂-4, and C of C₆H₄or

C₆H₄NO₂-4); 146.93 (s, C of C₆H₄or C₆H₄NO₂-4)

5

118.63 t 24.8 115.67 127.50-138.99 (m, PPh₃); 131.00, 142.18, 146.38

and 148.97 (s, C of C₆H₄and C₆H₄NO₂-4);

154.13 (s, dCH)

133.66 t 24.5 118.36 121.43 (s, dCH); 123.85-139.58 (m, PPh₃, dCH

and CH of C₆H₄NO₂-4); 146.34 and 146.71

(s, C of C₆H₄NO₂-4)

141.39 t 23.9 119.04 120.48 (s, dCH); 123.85-139.58 (m, PPh₃, dCH

and CH of C₆H₄NO₂-4); 146.27 and 146.41

(s, C of C₆H₄NO₂-4)

(E)-7a

(Z)-7a

d, d

(EE)-7b 75.25 95.49 109.79

(ZE)-7b 75.05 95.36 109.72

d

118.50 125.05, 132.69 and 136.40 (s, dCH);

123.22-138.82 (m, PPh₃, dCH and

CH of C₆H₄NO₂-4); 145.05 and 145.93

(s, C of C₆H₄NO₂-4)

-20.98

-20.25

-19.66

-20.63

d, d

132.47 t 25.1 116.71 120.94, 131.41, and 133.71 (s, dCH);

123.22-138.82 (m, PPh₃, dCH and

CH of C₆H₄NO₂-4); 145.11 and 145.88

(s, C of C₆H₄NO₂-4)

(E)-8a

(Z)-8a

(E)-8b

9

76.11 96.07 110.45

75.83 95.88 110.45

76.25 96.39 111.04

75.26 95.47 110.07

123.84,

127.03

140.86 t 24.3 119.19 107.45, 110.74 and 115.25 (s, CH of

C₄H₂ONO₂-2,3 and dCH); 127.38-139.12

(m, PPh₃and CH of C₄H₂ONO₂-2,3 or dCH);

159.28 and 159.38 (s, C of C₄H₂ONO₂-2,3)

147.08 t 24.3 119.77 108.09, 121.44 and 122.70 (s, CH of

C₄H₂ONO₂-2,3 and dCH); 127.38-139.12

(m, PPh₃and CH of C₄H₂ONO₂-2,3 or dCH);

150.75 and 151.77 (s, C of C₄H₂ONO₂-2,3)

124.05,

127.17

124.20,

127.10

d

120.10, 122.13, 124.84, and 129.34 (s, CH of

C₄H₂SNO₂-2,3 and dCH); 128.21-139.01

(m, PPh₃); 145.71 and 152.87 (s, C of

C₄H₂SNO₂-2,3)

123.23,

126.09

d

116.07 119.83, 121.08, 121.66, 122.30 and 125.36

(s, dCH and CH of C₆H₄NO₂-3); 127.48-138.64

(m, PPh₃and CH of C₆H₄NO₂-3); 142.27,

144.80, 148.81, and 148.98 (s, C of C₆H₄NO₂-3)

(E)-13

(Z)-13

75.26 95.36 109.72

74.92 95.18 109.92

-20.98

-20.78

-20.99

-20.91

-20.72

-20.36

-21.81

-20.13

-21.15

d, d

k, k

l, l

129.31 t 24.7

137.19 t 22.3

g

h

i

108.90 (s, CtN); 119.53 (s, dCH); 123.23-138.82

(m, PPh₃, dCH and CH of C₆H₄CN-4);

143.81 (s, C of C₆H₄CN-4)

109.14 (s, CtN); 118.70 (s, dCH); 123.43-138.82

(m, PPh₃, dCH and CH of C₆H₄CN-4);

143.61 (s, C of C₆H₄CN-4)

(E)-14a 75.28 95.36 109.71

(Z)-14a 74.92 95.16 109.79

(E)-14b 75.36 95.37 109.79

(Z)-14b 75.05 95.11 109.98

d

108.80 (s, CtN); 119.58 (s, dCH); 123.22-135.90

(m, PPh₃, dCH and CH of C₆H₄CN-4); 143.85

(s, C of C₆H₄CN-4); 214.71 and 219.67 (s, CtO)

105.80 (s, CtN); 120.84 (s, dCH); 123.22-135.90

(m, PPh₃, dCH and CH of C₆H₄CN-4); 145.07

(s, C of C₆H₄CN-4); 214.71 and 219.67 (s, CtO)

j

135.38 t 24.3 117.79 104.80 (s, CtN); 109.70 and 145.49 (s, C of

C₆H₄CN-4); 118.50-138.64 (m, PPh₃, dCH and

CH of C₆H₄CN-4); 197.00 and 200.31 (s, CtO)

142.45 t 23.8 116.61 105.12 (s, CtN); 108.77 and 145.08 (s, C of

C₆H₄CN-4); 118.50-138.64 (m, PPh₃, dCH and

CH of C₆H₄CN-4); 199.30 and 201.32 (s, CtO)

(E)-16

75.86 96.05 110.34

d

116.82 120.68 (s, dCH); 128.22-139.67 (m, PPh₃and

dCH); 146.93 (s, C of C₅H₄N-4); 151.09 (s, CH

of C₅H₄N-4)

(E)-17a 75.31 95.34 108.89

(E)-17b 76.01 96.01 110.57

138.51 t 24.4 117.88 126.66 (s, dCH); 127.28-138.61 (m, PPh₃and

dCH); 147.65 (s, C of C₅H₄N-4); 154.74 (s, CH

of C₅H₄N-4); 215.33 and 221.18 (s, CtO)

m, m

141.67 t 24.5 119.11 127.83 (s, dCH); 128.23-139.43 (m, PPh₃and

dCH); 148.39 (s, C of C₅H₄N-4); 155.90 (s, CH

of C₅H₄N-4); 200.23 and 203.46 (s, CtO)

(E)-18

74.87 95.60 109.55

123.16,

125.95

113.97 t 24.8 115.01 66.16 and 68.52 (s, CH of C₅H₄); 69.67 (s, C₅H₅);

86.31 (s, C of C₅H₄); 113.61 and 129.43

(s, dCH); 127.45-138.94 (m, PPh₃)

Donor-Acceptor Indenylruthenium(II) Complexes

Organometallics, Vol. 18, No. 4, 1999 587

Ta ble 2 (Con tin u ed )

a

b

Spectra recorded in C₆D₆; δ in ppm and J in Hz. Abbreviations: s, singlet; t, triplet; m, multiplet. ∆δ(C-3a,7a) ) δ(C-3a,7a(η-

indenyl complex)) - δ(C-3a,7a(sodium indenyl)), δ(C-3a,7a) for sodium indenyl 130.70 ppm. See ref 17. ^c123.84, 124.69 and 127.04 ppm

(s, C-4,7, C-5,6 and CH of C₆H₄NO₂-4). Overlapped by PPh₃or PPh₂carbons. ^e115.67 and 115.92 ppm (s, C_âand C of C₆H₄or C₆H₄NO₂-

d

4). ^f121.97, 123.21, 123.81, 126.14, 128.34 and 131.85 ppm (s, C-4,7, C-5,6 and CH of C₆H₄and C₆H₄NO₂-4). 116.64 and 119.68 ppm (s,

g

h

i

j

C

_âand C of C₆H₄CN-4). 117.43 and 119.90 ppm (s, C_âand C of C₆H₄CN-4). 116.65 and 119.72 ppm (s, C_âand C of C₆H₄CN-4). 117.52

and 118.77 ppm (s, C_âand C of C₆H₄CN-4). 120.12, 123.83 and 126.89 ppm (s, C-4,7, C-5,6 and CH of C₅H₄N-4). 119.80, 123.20 and

126.42 ppm (s, C-4,7, C-5,6 and CH of C₅H₄N-4). 120.82, 123.85 and 127.18 ppm (s, C-4,7, C-5,6 and CH of C₅H₄N-4).

k

l

m

Sch em e 2

Sch em e 3

supporting the acceptor group at the end of the unsat-

urated chain. The starting material for the Wittig type

reactions is the alkynyl-phosphonio derivative [Ru{Ct

CCH₂(PPh₃)}(η⁵-C₉H₇)(PPh₃)₂][PF₆] (6) which is ob-

tained in a one-pot synthesis by treatment of complex

1a with 2-propyn-1-ol and NaPF₆in methanol, at room

temperature, and in the presence of a large excess of

triphenylphosphine (65% yield) (Scheme 3).^15aAnalyti-

cal and spectroscopic data are in accordance with this

formulation (see Experimental Section).^10b,e,f

The treatment of a yellow THF solution of complex 6

with 1 equiv of LiⁿBu at -20 °C gives rise to an imme-

diate change to a violet solution probably containing the

ilyde-alkynyl derivative [Ru(CtCCHdPPh₃)(η⁵-C₉H₇)-

(PPh₃)₂]. Subsequent addition of nitro-substituted un-

saturated aldehydes, after the mixture was allowed to

reach room temperature, results in the formation of

σ-enynyl complexes 7-8a ,b (41-90% yield) (Scheme 4).

Complex 8b was isolated as the E stereoisomer while

complexes 7a ,b and 8a were obtained as an unseparable

mixture of the E and Z stereoisomers (2/1, 4/3, and 3/2,

respectively). All attempts to form these compounds ste-

reoselectively were unsuccessful. Similarly, the σ-enynyl

complex 9 was obtained (88% yield) from the reaction

of 6 with LiⁿBu and 3,3′-dinitrobenzophenone. The spec-

troscopic properties (see Tables 1 and 2 and Experimen-

tal Section) of all of these complexes are consistent with

the proposed formulations. Significant features are (a)

the ν(CtC) IR absorption band (2021-2041 cm^-1), (b)

the typical triplet resonance in the ¹³C{¹H} NMR spec-

tra for the Ru-Ct carbon nucleus at δ 123.85-147.08

ppm (²J _CP) 23.9-25.1 Hz), (c) singlet signals of C_âand

the olefinic carbons in the range ca. δ 110-140 ppm

(assigned using DEPT experiments) (see Table 2), and

(d) the olefinic protons resonances, in the ¹H NMR

spectra, which appear at ca. δ 6-7 ppm (see Table 1).

(15) (a) We have recently reported that alkynyl-phosphonio com-

plexes can be readily prepared through the regioselective nucleophilic

addition of phosphines to the C_γatom of indenylruthenium(II) alle-

nylidene complexes [Ru(dCdCdCR₂)(η⁵-C₉H₇)L₂][PF₆] (see refs 10b,e,f).

Thus, the formation of 6 may be understood assuming that the

unsubstituted allenylidene intermediate [Ru(dCdCdCH₂)(η⁵-C₉H₇)-

(PPh₃)₂][PF₆] is formed as a transient species which undergoes a rapid

nucleophilic addition of triphenylphosphine to the electrophilic C_γatom.

(b) Due to the relative imprecision of the crystallographic determination

some caution must be considered in the reliable interpretation of these

data. (c) This fact contrasts with the values of the bond lengths found

in similar systems, i.e., [Ru((E )-4,4′-CtC-C₆H₄-CHdCH-C₆H₄-

7a

NO₂)(η⁵-C₅H₅)(PPh₃)₂] and [Ru((E )-4,4′-CtC-C₆H₄-CtC-C₆H₄-

NO₂)(η⁵-C₅H₅)(PPh₃)₂]^7dwhich are consistent with the sequence of

single, double, and single bond (-CHdCH-) or single, triple, and single

bond (-CtC-), respectively. (d) Iglesias, L. Ph.D. Thesis, University

of Oviedo, 1998. Preliminary theoretical studies using ab initio calcu-

lations (Gaussian94) establish that a molecular minimum energy value

is achieved by the π overlapping of the metal fragment LUMO with

the corresponding π orbital of the 4-nitroarylenynyl chain, as shown

in Figure 3.

588 Organometallics, Vol. 18, No. 4, 1999

Cadierno et al.

Sch em e 4

Similar to the complexes 3a -c, the chemical shifts

of the R carbon atom attached to ruthenium are sensi-

tive to the electronic delocalization through the enynyl

chain as expected by the presence of the strong electron

attractor NO₂group at the end of the chain. Thus, if

the C_Rresonance in complex [Ru(CtC-C₆H₅)(η⁵-C₉H₇)-

(PPh₃)₂] (δ 114.25 ppm)^12ais compared with those of

complexes 3a , 7a , and 7b (δ ca. 128, 141.39 (Z) and

132.47 (ZE) ppm, respectively), a downfield shifting of

ca. 13-27 ppm occurs. It is interesting to note that the

assembling of a second CHdCH moiety in the dienynyl

complex 7b with respect to the enynyl 7a hardly affects

the electronic delocalization. As it will be discussed

below, this is in accord with the NLO properties. In a

lesser extent a similar downfield shifting (4-5 ppm) is

observed for the C_âresonance.

X-r a y Cr yst a l St r u ct u r es of [R u {CtC-(CH d

CH)₂-C₆H₄NO₂-4}(η⁵-C₉H₇)(P P h ₃)₂] (7b) a n d [Ru -

{CtC-CH dC(C₆H ₄NO₂-3)₂}(η⁵-C₉H ₇)(P P h ₃)₂] (9).

Both crystal structures consist of molecules of the

complex together with solvent molecules of crystalliza-

tion (pentane-THF and 2THF for 7b and 9, respec-

tively). Moreover, crystals only of the EE stereoisomer

of the complex (EE,ZE)-7b were obtained by slow

diffusion of pentane in a solution of the complex in THF.

ORTEP views of the molecular geometries of 7b and 9

are shown in Figures 1 and 2. Selected bond distances

and angles are listed in Table 3. Both molecules exhibit

the usual pseudooctahedral three-legged piano stool

geometry with the η⁵-indenyl ligand in the usual al-

lylene coordination mode. The interligand angles P(1)-

Ru-P(2), C(1)-Ru-P(1), and C(1)-Ru-P(2), and those

between the centroid C* and the legs show values

typical of a pseudooctahedron (see Table 3). Ru-P bond

distances of 2.300(8)-2.327(3) Å are in the range of

other ruthenium(II) indenyl complexes,^10,12but the Ru-

To confirm the connectivity and to obtain information

on the potential electronic π-conjugation in the unsatur-

ated hydrocarbon chains, the structure of complexes 7b

and 9 have been determined by X-ray crystallography.

F igu r e 1. ORTEP view of the structure of (EE)-[Ru{CtC(CHdCH)₂-C₆H₄NO₂-4}(η⁵-C₉H₇)(PPh₃)₂] [(EE)-7b]. For clarity,

aryl groups of the triphenylphosphine ligands are omitted (C* ) centroid of the indenyl ring).

Donor-Acceptor Indenylruthenium(II) Complexes

Organometallics, Vol. 18, No. 4, 1999 589

F igu r e 2. ORTEP view of the structure of [Ru{CtCCHdC(C₆H₄NO₂-3)₂}(η⁵-C₉H₇)(PPh₃)₂] (9). For clarity, aryl groups of

the triphenylphosphine ligands are omitted (C* ) centroid of the indenyl ring).

C(1) bond length values for 7b and 9 of 1.99(2) and 1.97-

(1) Å, respectively, are among the shortest ones reported

for alkynyl complexes.^7d,gThe enynyl groups are almost

linearly attached to ruthenium with angles Ru-C(1)-

C(2) of 172.(2)° (7b) and 179.6(9)° (9) and C(1)-C(2)-

C(3) of 178.(3) (7b) and 169.(1)° (9). Complex 7b contains

the first structurally characterized example of a dienyl-

acetylide chain bonded to a metal fragment. Within the

unsaturated seven carbon chain C(1)-C(2)-C(3)-C(4)-

C(5)-C(6)-C(81) the C-C separations are 1.19(3), 1.38-

(3), 1.35(2), 1.35(3), 1.34(3), and 1.44(3) Å, respectively.

It is worth noting the similar and relatively short C-C

distances (1.35(2) Å av) observed in that part of the

chain involving the sequence of single and double bonds

i.e. the C(2)-C(6) fragment.^15bIn contrast, the C-C

distances of the enynyl chain C(1)-C(4) in complex 9

are consistent with a typical sequence of triple, single,

and double bonds, i.e., 1.23(1), 1.42(2), and 1.31(1) Å,

respectively. Although apparently there is no contribu-

tion of a potential quinoidal resonant form (distances

and angles of the nitro substituents and aryl group in

both complexes 9 and 7b are unexceptional), the absence

of bond length alternation of the C-C distances in C(2)-

C(6) seems to indicate that there is an extensive

electronic delocalization.^15cIn accordance with this fact,

the structure of 7b shows that all of the atoms of the

dienynyl chain and those of the nitroaryl ring are

approximately in a plane as is shown in Figure 3. The

deviations of the atoms from the mean least-squares

plane passing through them being in the range of N

-0.0808 to C(3) -0.2515 Å (Table 3). Another interest-

ing feature of this structure is the small diehedral angle

of 7.6(9)° between the mean plane containing the

hydrocarbon chain and the pseudo mirror plane of the

metallic moiety (containing the Ru atom, the C(1) atom,

and the centroid C* of the five carbon ring of the indenyl

ligand). Although we have not studied the features of

the bonding between the metal fragment and the enynyl

group this particular orientation seems to favor the

maximum overlapping of the metallic π frontier orbital

with the π system of the conjugated dienynyl group.^15d

This is in accordance with the good NLO properties

shown by complex 7b which probably stems from the

good electronic communication between the donor metal

fragment and the strong acceptor nitroaryl group through

the hydrocarbon chain (see below).

Bim et a llic Don or -Accep t or Com p lexes [(η⁵-

C₉H₇)(P P h ₃)₂Ru {(µ-CtN)ML₅}][CF ₃SO₃]_n(n ) 0,

ML₅) Cr (CO)₅(11a ), W(CO)₅(11b); n ) 3, ML₅

)

Ru (NH₃)₅(12)), [(η⁵-C₉H₇)(P P h ₃)₂Ru {(µ-CtCCHd

CH-C₆H₄C t-4)ML₅}][CF ₃SO₃]_n(n ) 0, ML₅) Cr -

(CO)₅[(E,Z)-14a ], W(CO)₅[(E,Z)-14b]; n ) 3, ML₅)

Ru (NH₃)₅[(E,Z)-15]), a n d [(η⁵-C₉H₇)(P P h ₃)₂Ru {(µ-

CtCCHdCH-C₅H₄N-4)M(CO)₅}] (M ) Cr [(E)-17a ],

W [(E)-17b]). An alternative entry to the donor-

acceptor complexes is based on the synthesis of mixed

valence dinuclear metallic species providing that a good

electronic coupling between the donor and acceptor

metallic moieties can be established. In this regard we

sought to synthesize novel dinuclear derivatives by

using the indenylruthenium(II) fragment [Ru(η⁵-C₉H₇)-

(PPh₃)₂] as the donor moiety attached to a formally

acceptor metallic fragment through the coordination of

an unsaturated bridging group. We were specially

interested in studying the influence of the acceptor

metallic moiety on the quadratic hyperpolarizabilities

(16) (a) Loucif-Saibi, R.; Delaire, J . A.; Bonazzola, L.; Doisneau, G.;

Balavoine, G.; Fillebeen-Khan, T.; Ledoux, I.; Pucceti, G. Chem. Phys.

1992, 167, 369. (b) Laidlaw, W. M.; Denning, R. G.; Verbiest, T.;

Chouchard, E.; Persoons, A. Nature 1993, 363, 58. (c) Behrens, U.;

Brussaard, H.; Hagenau, U.; Heck, J .; Hendricks, E.; Kornich, J .; van

der Linden, J . G. M.; Persoons, A.; Speck, A. L.; Veldman, N.; Voss,

B.; Wong, H. Chem. Eur. J . 1996, 2, 98. (d) Mata, J .; Uriel, S.; Peris,

E.; Llusar, R.; Houbrechts, S.; Persoons, A. J . Organomet. Chem. 1998,

562, 197.

590 Organometallics, Vol. 18, No. 4, 1999

Cadierno et al.

Ta ble 3. Selected Bon d Dista n ces a n d Slip P a r a m eter D^a(Å) a n d Bon d An gles a n d Dih ed r a l An gles F A^b,

HA^c, a n d CA^d(d eg) for [Ru {CtC-(CH)CH)₂-C₆H₄NO₂-4}(η⁵-C₉H₇)(P P h ₃)₂].THF /n -C₅H₁₂(7b) a n d

[Ru {CtC-CHdC(C₆H₄NO₂-3)₂}(η⁵-C₉H₇)(P P h ₃)₂].2THF (9)

Complex 9

Distances

Ru-C*

1.94(1)

1.97(1)

2.327(3) C(81)-C(82)

2.320(3) C(82)-C(83)

2.39(1)

2.25(1)

2.18(1)

P(2)-C(51)

P(2)-C(61)

1.86(1) C(1)-C(2)

1.84(1) C(2)-C(3)

1.37(2) C(3)-C(4)

1.37(2) C(4)-C(81)

1.43(2) C(4)-C(91)

1.36(2) C(70)-C(78)

1.36(2) C(70)-C(74)

1.42(2) C(70)-C(71)

1.52(1) C(71)-C(72)

1.21(1) C(72)-C(73)

1.20(1) C(73)-C(74)

0.15(1) C(74)-C(75)

1.23(1) C(75)-C(76)

1.42(2) C(76)-C(77)

1.31(1) C(77)-C(78)

1.50(2) C(91)-C(92)

1.48(2) C(92)-C(93)

1.40(2) C(93)-C(94)

1.49(1) C(94)-C(95)

1.39(2) C(95)-C(96)

1.42(2) C(96)-C(91)

1.35(2) C(95)-N(2)

1.41(2) N(2)-O(2A)

1.42(2) N(2)-O(2B)

1.35(2)

1.40(2)

1.36(2)

1.37(2)

1.40(2)

1.36(2)

1.38(2)

1.42(2)

1.48(2)

1.24(2)

Ru-C(1)

Ru-P(1)

Ru-P(2)

Ru-C(70)

Ru-C(71)

Ru-C(72)

Ru-C(73)

Ru-C(74)

P(1)-C(11)

P(1)-C(21)

P(1)-C(31)

P(2)-C(41)

C(83)-C(84)

C(84)-C(85)

C(85)-C(86)

2.212(9) C(86)-C(81)

2.37(1)

1.84(1)

1.83(1)

1.87(1)

C(85)-N(1)

N(1)-O(1A)

N(1)-O(1B)

∆

Angles

C*-Ru-P(1)

124.4(3)

121.8(4)

122.9(5)

86.3(3)

87.1(3)

103.9(1)

179.6(9)

169.(1)

130.(1)

124.(1)

121.(1)

115.(1)

C(86)-C(81)-C(4)

120.(1)

C(71)-C(70)-C(78) 137.(1)

C(92)-C(91)-C(4)

C(96)-C(91)-C(4)

122.(1)

119.(1)

C*-Ru-P(2)

C(83)-C(82)-C(81) 122.(1)

C(82)-C(83)-C(84) 120.(1)

C(85)-C(84)-C(83) 115.(1)

C(84)-C(85)-C(86) 127.(1)

C(71)-C(70)-C(74) 107.(1)

C(70)-C(71)-C(72) 108.(1)

C(73)-C(72)-C(71) 109.(1)

C(72)-C(73)-C(74) 111.(1)

C(73)-C(74)-C(75) 136.(1)

C(73)-C(74)-C(70) 104.(1)

C(75)-C(74)-C(70) 120.(1)

C(76)-C(75)-C(74) 120.(1)

C(75)-C(76)-C(77) 122.(1)

C(78)-C(77)-C(76) 121.(1)

C(77)-C(78)-C(70) 122.(1)

C(92)-C(91)-C(96) 119.(1)

C*-Ru-C(1)

C(93)-C(92)-C(91) 122.(1)

C(92)-C(93)-C(94) 120.(2)

C(95)-C(94)-C(93) 119.(1)

C(94)-C(95)-C(96) 122.(1)

C(1)-Ru-P(1)

C(1)-Ru-P(2)

P(2)-Ru-P(1)

C(2)-C(1)-Ru

C(1)-C(2)-C(3)

C(4)-C(3)-C(2)

C(3)-C(4)-C(81)

C(3)-C(4)-C(91)

C(91)-C(4)-C(81)

C(84)-C(85)-N(1)

C(86)-C(85)-N(1)

115.(1)

117.(1)

C(94)-C(95)-N(2)

C(96)-C(95)-N(2)

121.(1)

117.(2)

C(85)-C(86)-C(81) 116.(1)

O(1B)-N(1)-C(85) 117.(1)

O(1B)-N(1)-O(1A) 126.(1)

O(1A)-N(1)-C(85) 117.(1)

C(95)-C(96)-C(91) 117.(1)

O(2B)-N(2)-O(2A) 124.(2)

O(2B)-N(2)-C(95) 116.(2)

O(2A)-N(2)-C(95) 119.(1)

FA

HA

175.7(5)

177.4(8)

C(82)-C(81)-C(86) 119.(1)

C(82)-C(81)-C(4)

CA

165.0(6)

121.(1)

C(78)-C(70)-C(74) 116.(1)

Complex 7b

Distances

Ru-C*

1.95(2)

1.99(2)

2.307(6) P(2)-C(41)

2.300(8) P(2)-C(51)

2.44(2)

2.19(2)

2.17(2)

2.20(2)

2.40(2)

1.89(2)

P(1)-C(21)

1.88(2)

∆

0.22(2) C(72)-C(73)

1.19(3) C(73)-C(74)

1.38(3) C(74)-C(75)

1.35(2) C(75)-C(76)

1.35(3) C(76)-C(77)

1.34(3) C(77)-C(78)

1.44(3) C(81)-C(82)

1.33(3) C(83)-C(84)

1.45(3) C(85)-C(86)

1.41(3) N-O(2)

1.42(3)

1.33(3)

1.40(2)

1.39(3)

1.34(3)

1.46(3)

1.33(3)

1.36(3)

1.17(3)

Ru-C(1)

Ru-P(1)

Ru-P(2)

Ru-C(70)

Ru-C(71)

Ru-C(72)

Ru-C(73)

Ru-C(74)

P(1)-C(11)

P(1)-C(31)

1.80(2) C(1)-C(2)

1.84(3) C(2) -C(3)

1.84(2) C(3)-C(4)

1.85(2) C(4)-C(5)

1.39(3) C(5)-C(6)

1.50(3) C(6)-C(81)

1.36(3) C(70)-C(78)

1.35(2) C(70)-C(74)

1.20(2) C(70)-C(71)

P(2)-C(61)

C(81)-C(86)

C(84)-N

C(82)-C(83)

C(84)-C(85)

N-O(1)

Angles

C*-Ru-P(1)

C*-Ru-P(2)

C*-Ru-C(1)

C(1)-Ru-P(1)

C(1)-Ru-P(2)

P(2)-Ru-P(1)

C(2)-C(1)-Ru

C(1)-C(2)-C(3) 178.(3)

C(4)-C(3)-C(2) 130.(2)

C(6)-C(5)-C(4) 128.(2)

C(3)-C(4)-C(5) 127.(2)

124.5(7)

121.3(7)

122.(1)

85.4(7)

88.4(7)

104.3(2)

172.(2)

C(5)-C(6)-C(81)

C(86)-C(81)-C(6)

C(6)-C(81)-C(82)

C(84)-C(83)-C(82) 120.(3)

C(83)-C(84)-N 116.(2)

C(84)-C(85)-C(86) 116.(3)

O(2)-N-O(1)

O(1)-N-C(84)

FA

130.(2)

123.(2)

122.(2)

C(78)-C(70)-C(74) 123.(2)

C(70)-C(78)-C(77) 121.(3)

C(78)-C(70)-C(71) 136.(3)

C(71)-C(70)-C(74) 100.(2)

C(72)-C(71)-C(70) 117.(3)

C(71)-C(72)-C(73) 100.(3)

C(74)-C(73)-C(72) 114.(2)

C(75)-C(74)-C(70) 115.(2)

C(73)-C(74)-C(75) 135.(3)

C(73)-C(74)-C(70) 109.(2)

C(76)-C(75)-C(74) 119.(3)

C(78)-C(77)-C(76) 119.(3)

C(86)-C(81)-C(82) 114.(2)

C(83)-C(82)-C(81) 120.(3)

C(83)-C(84)-C(85) 125.(3)

C(85)-C(84)-N

119.(3)

124.(3)

119.(3)

174.(1)

177.(2)

C(85)-C(86)-C(81) 125.(2)

O(2)-N-C(84)

CA

DA

116(3)

161.(1)

7.6(9)

HA

a

b

D ) d[Ru-C(74), C(70)]-d[Ru-C(71), C(73)]. FA (fold angle) ) angle between normals to least-squares planes defined by C(71),

C(72), C(73) and C(70), C(74), C(75), C(76), C(77), C(78). ^cHA (hinge angle) ) angle between normals to least-squares planes defined by

d

C(71), C(72), C(73) and C(71), C(74), C(70), C(73). CA (conformational angle) ) angle between normals to least-squares planes defined

by C**, C*, Ru and C*, Ru, P(2). ^eDA ) angle between normals to least-squares planes defined by C*, Ru, C(1) and Ru, C(1), C(2), C(3),

C(4), C(5), C(6), C(81), C(82), C(83), C(84), C(85), C(86), N, O(1), O(2). (Deviations of the atoms from the plane (Å): Ru: -0.0108; C(1):

0.0093; C(2):0.1068; C(3):0.2515;C(4):0.1680;C(5):0.2056; C(6):0.0964; C(81):0.0878; C(82):0.0757;C(83):0.0397; C(84):-0.0160; C(85):0.0122;

C(86):0.0805; N:-0.0808; O(1):-0.1506; O(2): -0.2448). C* ) centroid of C(70), C(71), C(72), C(73), C(74). C** ) centroid of C(70), C(74),

C(75), C(76), C(77), C(78).

(â). It is worth mentioning that studies concerning

bimetallic complexes possessing second-order NLO prop-

erties are scarce.^4f,16

species by reaction of 1a with KCN in refluxing metha-

nol (Scheme 5). The IR spectrum shows the expected

ν(CtN) absorption band at 2071 cm^-1, and the ¹³C{¹H}

NMR spectrum exhibits the Ru-CtN resonance, which

appears as a triplet at δ 143.49 ppm (²J _CP) 22.7 Hz).

Since the CtN group is one of the most simple and

efficient unsaturated bridging groups the precursor

complex [Ru(CtN)(η⁵-C₉H₇)(PPh₃)₂] (10) was prepared

(81% yield), as an appropiate precursor of dinuclear

As expected, the cyano group acts in complex 10 as a

good bridging ligand which allows the synthesis of

Donor-Acceptor Indenylruthenium(II) Complexes

Organometallics, Vol. 18, No. 4, 1999 591

F igu r e 3. ORTEP view of the structure of complex 9 showing the planarity of the dienynyl chain and the nitroaryl ring.

Sch em e 5

dinuclear metal complexes. Thus, the reaction of com-

pound 10 with an equimolar amount of [M(CO)₅(THF)]

(M ) Cr, W) in THF, at room temparature, yields the

neutral bimetallic derivatives [(η⁵-C₉H₇)(PPh₃)₂Ru{(µ-

CtN)M(CO)₅}] (11a ,b) (70 and 85% yield, respectively)

(Scheme 5). IR and NMR data support the proposed

formulations (see Experimental Section for details).

Thus, IR spectra show typical ν(CtN) and ν(CtO)

absorptions in the range 1881-2109 cm^-1, and the ¹³C-

{¹H} NMR spectra display Ru-CtN triplet resonances

at δ 155.97 (²J _CP) 20.7 Hz) (11a ) and 154.80 ppm (²J _CP

) 20.6 Hz) (11b). Downfield M-CO singlet resonances

were also observed in the range δ 198.18-220.76 ppm.

Similarly, the treatment of 10 with [Ru(NH₃)₅(OSO₂-

CF₃)][CF₃SO₃]₂generates the cationic Ru^II-Ru^IIIbime-

tallic derivative [(η⁵-C₉H₇)(PPh₃)₂Ru{(µ-CtN)Ru(NH₃)₅}]-

[CF₃SO₃]₃(12) which was characterized by elemental

analysis, conductivity measurements and IR spectros-

copy (see Scheme 5 and Experimental Section).

Mixed valence bimetallic derivatives were also syn-

thesized starting from the σ-enynyl complexes [Ru(Ct

CCHdCH-C₆H₄CN-4)(η⁵-C₉H₇)(PPh₃)₂] (13) and [Ru-

(CtCCHdCH-C₅H₄N-4)(η⁵-C₉H₇)(PPh₃)₂] (16) which

bear uncoordinated cyano or pyridine terminal groups.

These complexes were prepared through Wittig-type

reactions as described above for the analogous σ-enynyl

compounds 7-9 (Scheme 6). It is worth mentioning that

while 13 was obtained as a nonseparable mixture of the

E and Z stereoisomers (ca. 4/1, 71% yield), complex 16

was surprisingly obtained stereoselectively as the E

stereoisomer (83% yield). Their analytical and spectro-

scopic data, which are similar to those of σ-enynyl

complexes 7-9 (see Experimental Section and Tables

1 and 2), are consistent with the proposed formulations.

Treatment of 13 and 16 with [M(CO)₅(THF)] (M )

Cr, W) leads to the formation of the neutral bimetallic

complexes 14a ,b and 17a ,b, respectively (70-85% yield)

(Scheme 6) which were characterized by microanalyses,

IR, and NMR spectroscopy (see Experimental Section

and Tables 1 and 2). Significantly, the NMR spectra

show the expected proton and carbon resonances at

similar chemical shifts to those shown in the spectra of

the precursor complexes 13 and 16, indicating a small

electronic effect upon the coordination to the M(CO)₅

fragment. The cationic Ru^II-Ru^IIIbimetallic derivative

15 was similarly prepared from 13 by the reaction with

[Ru(NH₃)₅(OSO₂CF₃)][CF₃SO₃]₂as is described above for

the analogous dinuclear complex 12 (53% yield) (Scheme

6). Complexes 14a ,b and 15 have been isolated as a

mixture of the corresponding stereoisomers E and Z in

accordance with the isomeric mixture of the precursor

derivative 13.

Bim eta llic Ru th en iu m (II)-Ir on (II) Com p lexes

[R u (CtCCH dCH -C₅H ₄F eC₅H ₅)(η⁵-C₉H ₇)(P P h ₃)₂]

[(E)-18] an d [Ru {dCdC(H)-CHdCH-C₅H₄FeC₅H₅}-

(η⁵-C₉H₇)(P P h ₃)₂][BF ₄] [(E)-19]. Since the ferrocenyl

group (η⁵-C₅H₄)Fe(η⁵-C₅H₅) has been widely used in

organometallic complexes with NLO properties, it was

of interest to synthesize a bimetallic complexes involving

this group as part of the π-conjugated system.⁴The

synthesis of the novel ferrocenyl complex was achieved

through the Wittig-type reaction between the alkynyl-

phosphonio complex 6 and ferrocenecarboxaldehyde.

The reaction is stereoselective affording the bimetallic

complex [Ru(CtCCHdCHC₅H₄FeC₅H₅)(η⁵-C₉H₇)(PPh₃)₂]

[(E)-18] isolated as a red crystalline solid (67% yield)

(Scheme 7). ³¹P{¹H}, ¹H, and ¹³C{¹H} NMR spectra

reveal typical signals of both [Ru(η⁵-C₉H₇)(PPh₃)₂] and

592 Organometallics, Vol. 18, No. 4, 1999

Cadierno et al.

Sch em e 6

Sch em e 7

[(η⁵-C₅H₄)Fe(η⁵-C₅H₅)] moieties along with resonances

assigned to the enynyl bridging chain. The coupling

constant (J _HH) 15.7 Hz) for the olefinic protons in the

¹H NMR spectrum clearly indicates an E configuration

of the carbon-carbon double bond. Protonation of (E)-

18 takes place regioselectively on the C_âatom of the

alkynyl group, yielding the cationic vinyl-vinylidene

complex [Ru{)CdC(H)CHdCHC₅H₄FeC₅H₅}(η⁵-C₉H₇)-

(PPh₃)₂][BF₄] [(E)-19] (71% yield) (Scheme 7). The

presence of the vinylidene moiety was identified, as

usual, on the basis of (i) (¹H NMR) a broad singlet

resonance at δ 5.34 ppm for the RudCdCH proton and

(ii) (¹³C NMR) the low-field triplet resonance of the

carbene carbon RudC_R(361.82 ppm, J _CP) 16.5 Hz).

2

Qu a d r a tic Hyp er p ola r iza bilities. The molecular

hyperpolarizabilities of complexes 2-5 and 7-19 as

determined by the hyper-Rayleigh scattering (HRS)

technique are given in Table 4. Comparison of 3-5 and

7 with organic amino analogues shows that despite the

triple carbon-carbon bond the half sandwich [Ru]-Ct

C moiety is a powerful donor that can compete with the

strongest organic donors.^2b,c,18,19It has been suggested

that the high effectiveness of this indenylruthenium-

(II) donor fragment compared to other organometallic

Donor-Acceptor Indenylruthenium(II) Complexes

Organometallics, Vol. 18, No. 4, 1999 593

Ta ble 4. Wa velen gth of Ma xim u m Absor p tion s a n d

term which leads to an underestimated static value for

compounds with their MLCT band close to the harmonic

frequency (532 nm).^7d-9,16a,20The shortcoming of the

two-level model and the presence of strong resonance

enhancement for 5-8 prohibit any presumptions on

their relative NLO efficiencies. Nevertheless, the results

for 7a ,b seem to suggest the hyperpolarizability levels

off upon the addition of the second double bond. The

low hyperpolarizabilities for 2a with respect to 3a

emanates most likely from the net positive charge on

the ruthenium center which results in a decrease of the

electron donor ability of the [Ru]⁺dCdC metal fragment

as compared to that of [Ru]-CtC. Furthermore, the

rather low hyperpolarizability of 9 indicates that the

increased π-system is insufficient to account for the loss

of â as the acceptor p-NO₂group is replaced by the two

m-NO₂groups.²

The hyperpolarizabilities of bimetallic complexes 10-

19 have also been assessed. The addition of a metal

group to a cyano or pyridyl acceptor in the series 10-

12, 13-15, and 16,17 has been found to increase the

NLO effectivity of the monometallic precursor complex

(10, 13, and 16). Previous reports on pyridylmetal

pentacarbonyl complexes by Kanis et al. suggested that

the role of the metal is limited to that of an inductive

acceptor that lowers the energy of the pyridyl-centered

LUMO.²¹The pyridyl ring itself remains the effective

molecular acceptor. If we assume that this mechanism

is also valid for the cyano complexes studied here, then

the differences observed between the bimetallic com-

pounds and their precursor complexes can be explained

by the different σ acceptor effectiveness of the attached

metal groups. It is expected that the tungsten complexes

(11b, 14b, and 17b) should have larger hyperpolariz-

abilities than their chromium analogues (11a , 14a , and

17a ) since the electron density at the tungsten center

is better reduced by the π back-donation to the carbonyl

groups.²²A comparison of the Ru(II)-Ru(III) complexes

(12 and 15) and the Ru(II)-group 6 metal complexes

(11 and 14) is not so straightforward as an inverse order

is observed in both series. Theoretical calculations may

be needed to reveal which has the largest influence on

the LUMO, either the higher intrinsic electronegativity

of the Ru(III) center with respect to W(0) and Cr(0) or

the presence of the donor NH₃ligands as compared to

the π acceptor CO ligands. Note that the group 6 metal

cyanobenzene and pyridyl complexes 14, 15, and 17

exhibit the largest hyperpolarizabilities found for bi-

metallic complexes to date.^3,18

F ir st Hyp er p ola r iza bilities for Com p lexes 2-19^a

complex

λ_max(nm)

â (×10^-30esu)^b

â_o(×10^-30esu)^b

2a

3a

3b

3c

4

379

476

459

456

463

509

507

523

550

598

345

396

392

621

427

442

456

442

399

451

462

345

301

116

746

516

540

1027

1295

1257

1320

908

487

48

50

119

107

117

202

85

89

34

43

88

25

5

10

15

26

71

119

150

80

5

(E,Z)-7a

(EE,ZE)-7b

(E,Z)-8a

(E)-8b

9

10

11a

11b

12*

(E,Z)-13

(E,Z)-14a

(E,Z)-14b

(E,Z)-15*

(E)-16

(E)-17a

(E)-17b

(E)-18

(E)-19

13

25

40

108

238

465

700

315

100

260

535

273

117

37

60

71

141

73

a

Recorded in dichloromethane except for * (acetone solutions).

The hyper-Rayleigh scattering measurements were performed

b

at 1064 nm; all values (10%; the static values â_oare calculated

using the two-level model.

species such as ferrocenes originates from the in-plane

MLCT transition (MLCT lies in the plane formed by the

conjugated system), unlike to the out-of-plane MLCT

transition present in metallocenes (MLCT axis is per-

pendicular to the plane formed by the conjugated

system).^3c,4c,7a,18Although part of the large NLO ef-

ficiency of these complexes is attributed to resonance

enhancement, the calculated static hyperpolarizabilities

(â_o) still confirm this tendency.

Within the series studied, changes induced in the

phosphine ligand (3a -c) do not have an impact on the

static hyperpolarizability. Although there are no differ-

ences in the hyperpolarizability between 4 and 5 and

their cyclopentadienyl counterparts [Ru(η⁵-C₅H₅)(PPh₃)₂]

reported by Humphrey and co-workers (â_o) 202 vs 212

× 10^-30and 85 vs 86 × 10^-30esu, respectively),^3cthe

value found for 3a (119 vs 96 × 10^-30esu)^3cseems to

indicate that the indenyl group is only slightly more

effective than the cyclopentadienyl ring in increasing

the electron donor capability of the ruthenium center.

Chain lengthening of the organic ligands (compare 3-5

and 7 and 8) results in a clear increase of the measured

hyperpolarizability, yet the calculated static values do

not confirm this trend. Since the two-level model has

been originally introduced for molecules showing only

one transition, this may indicate that the model is

inadequate for the complexes investigated in this work.

However, the good results obtained with the two-level

model for other linear organometallic compounds with

the MLCT transition as the main contributor to the

hyperpolarizability is a good indication that the failure

of the model originates from the neglect of the damping

Complexes 18 and 19 contain two metal groups which

have both previously been used as an electron donor and

thus display a D₁-π-D₂symmetry. A previous study by

Colbert et al. on similar chiral bimetallic ferrocene

(20) (a) Coe, B. J .; Chadwick, G.; Houbrechts, S.; Persoons, A. J .

Chem. Soc., Dalton Trans. 1997, 1705. (b) Coe, B. J .; Chamberlain,

M. C.; Essex-Lopresti, J . P.; Gaines, S.; J effery, J . C.; Houbrechts, S.;

Persoons, A. Inorg. Chem. 1997, 36, 3284. (c) Coe, B. J .; Essex-Lopresti,

J . P.; Houbrechts, S.; Persoons, A. Chem. Commun. 1997, 1645. (d)

Coe, B. J .; Harris, J . A.; Harrington, L. J .; J effery, J . C.; Rees, L. H.;

Houbrechts, S.; Persoons, A. Inorg. Chem. 1998, 37, 3391.

(21) (a) Kanis, D. R.; Ratner, M. A.; Marks, T. J . Chem. Rev. 1994,

94, 195. (b) Kanis, D. R.; Lacroix, P. G.; Ratner, M. A.; Marks, T. J . J .

Am. Chem. Soc. 1994, 116, 10089.

(22) (a) Crabtree, R. H. The Organometallic Chemistry of the

Transition Metals; Wiley-Interscience: New York, 1994; p 13. (b) It

has also been reported that the value of â also decreases for chromium

Fischer-type carbene complexes as compared with the analogous

tungsten complexes. See ref 5c.

(17) The parameter ∆δ(C-3a,7a) can be used as an indication of the

indenyl distortion: (a) Baker, R. T.; Tulip, T. H. Organometallics 1986,

5, 839. (b) Kohler, F. G. Chem. Ber. 1974, 107, 570.

(18) Verbiest, T.; Houbrechts, S.; Kauranen, M.; Clays, K.; Persoons,

A. J . Mater. Chem. 1997, 7, 2175.

(19) Matsuzawa, N.; Dixon, D. A. J . Phys. Chem. 1992, 96, 6232.

594 Organometallics, Vol. 18, No. 4, 1999

Cadierno et al.

complexes only revealed negligible NLO properties.²³

Therefore, the large hyperpolarizabilities found here are

rather unexpected. The results suggest that the donor

strength of both groups is sufficiently different to induce

the molecular asymmetry required for good NLO prop-

erties.

studies aimed at a better understanding of the influence

of the acceptor group and the π-conjugated bridging

system on the hyperpolarizability values in these ru-

thenium(II) complexes are in progress.

Exp er im en ta l Section

The manipulations were performed in an atmosphere of dry

nitrogen using vacuum-line and standard Schlenk techniques.

All reagents were obtained from commercial suppliers and

used without further purification. Solvents were dried by

standard methods and distilled under nitrogen before use. The

compounds [RuCl(η⁵-C₉H₇)L₂] (L₂) 2PPh₃,²⁴dppe,²⁵dppm²⁵),

[Ru(NH₃)₅(OSO₂CF₃)][CF₃SO₃]₂,²⁶HCtC-C₆H₄NO₂-4,²⁷and

HCtC-C₆H₄R-4 (R ) CtC-C₆H₄NO₂-4,²⁸NdCH-C₆H₄NO₂-

4^7a) were prepared by following the methods reported in the

literature.

Infrared spectra were recorded on a Perkin-Elmer 1720-XFT

spectrometer. The conductivities were measured at room

temperature, in ca. 10^-3mol dm^-3acetone solutions, with a

J enway PCM3 conductimeter. The C, H, and N analyses were

carried out with a Perkin-Elmer 240-B microanalyzer. Non

satisfactory microanalyses were obtained for complexes 5 and

8a ,b, due to uncompleted combustions, instead mass spectra

(FAB) were recorded for these complexes using a VG Autospec

spectrometer, operating in the positive mode; 3-nitrobenzyl

alcohol was used as the matrix. UV-vis spectra were recorded

using a Shimadzu UV-160 spectrophotometer. NMR spectra

were recorded on a Bruker AC300 instrument at 300 MHz (¹H),

121.5 MHz (³¹P) or 75.4 MHz (¹³C) using SiMe₄or 85% H₃PO₄

as standards. DEPT experiments have been carried out for all

of the complexes. ³¹P{¹H}, ¹H, and ¹³C{¹H} NMR spectroscopic

data for the donor-acceptor σ alkynyl complexes are collected

in Tables 1 and 2.

Con clu d in g Rem a r k s

In this work we describe the synthesis of novel donor-

acceptor ruthenium(II) complexes which show excellent

NLO properties. Through efficient synthetic methodolo-

gies, complexes of the following types have been pre-

pared in good yields: (a) σ-arylacetylideruthenium(II)

complexes (3-5), (b) σ-enynyl- and σ-dienynylruthe-

nium(II) complexes (7-9, 13, 16), and (c) bimetallic

ruthenium(II)-chromium(0) (11a , 14a , 17a ), ruthe-

nium(II)-tungsten(0) (11b, 14b, 17b), ruthenium(II)-

ruthenium(III) (12, 15), and ruthenium(II)-iron(II)

complexes (18, 19). Most of these complexes are char-

acterized by the presence of a formal donor indenylru-

thenium(II) moiety [Ru(η⁵-C₉H₇)L₂] and a strong π

acceptor group such as the NO₂group or a metal

carbonyl fragment. Novel derivatives also include mild

donor-acceptor systems such as Ru(II)-Fe(II) and the

mixed valence Ru(II)-Ru(III) pair. In these complexes

the donor and acceptor centers are linked either by a

π-conjugated hydrocarbon system (i.e., arylacetylide

-CtC-C₆H₄-, -CtC-C₆H₄-CtC-C₆H₄- or -CtC-

C₆H₄-NdCH-C₆H₄-; enynyl -CtC-CHdCH-C₆H₄-

or -CtC-CHdCH-C₄H₂X-; dienynyl -CtC-(CHd

CH)₂-C₆H₄-) or by a N-functionalized bridge (i.e.,

cyanide group -CtN- or -CtC-CHdCH-C₆H₄-Ct

N-; pyridyl group -CtC-CHdCH-C₅H₄N-). All of

these unsaturated skeletons enable the electronic com-

munication between the donor and acceptor fragments

(metal-to-ligand charge transfer (MLCT)). This is ass-

esed by means of the X-ray crystal structure of the

complex [Ru{CtC-(CHdCH)₂-C₆H₄NO₂-4}(η⁵-C₉H₇)-

(PPh₃)₂] (7b) which shows the planarity of the hydro-

carbon chain in such a way that all of the π orbitals of

the conjugated system, including those of the aryl ring,

are able to perform a favorable overlapping.^15c

Determination of molecular quadratic hyperpolariz-

abilities (â) (HRS) for these donor-acceptor derivatives

yields resonantly enhanced values significantly larger

than those of the more commonly studied organometallic

chromophores (â_{1064 nm}) 100-1320 × 10^-30esu). Most

significantly, the complexes 14, 15, and 17 show the

largest static quadratic hyperpolarizabilities values (â₀

) 10-150 × 10^-30esu) found for bimetallic complexes

to date.

In summary, we describe an accessible entry to

organotransition metal complexes of interest as new

materials for nonlinear optics. Some of these complexes

show â values which are among the highest reported

for organometallic complexes, representing good ex-

amples for the still very scarce information on the

relationship between the molecular structures and NLO

properties. In this regard MO calculations to determine

the nature of the LUMO orbitals in these type of donor-

acceptor complexes may be of interest. Theoretical

Syn t h esis of [R u {dCdC(H )-C₆H ₄NO₂-4}(η⁵-C₉H ₇)L₂]-

[P F ₆] (L₂) 2P P h ₃(2a ), d p p e (2b), d p p m (2c)). Gen er a l

P r oced u r e. A mixture of [RuCl(η⁵-C₉H₇)L₂] (1a -c) (1 mmol),

NaPF₆(0.336 g, 2 mmol), and HCtC-C₆H₄NO₂-4 (0.294 g, 2

mmol) in 50 mL of methanol was heated under reflux for 2 h.

The resulting solution was evaporated to dryness, and the solid

residue was dissolved in dichloromethane (ca. 20 mL) and

filtered into stirred diethyl ether (ca. 100 mL) to give a brown

solid precipitate. The resulting solid was washed with diethyl

ether (2 × 20 mL) and vacuum-dried. Yield, IR (KBr, ν(PF₆^-),

cm^-1), analytical data, conductivity (acetone, Ω^-1cm²mol^-1),

and NMR spectroscopic data (ppm) are as follows. For 2a . 67%

(0.692 g). 839. Anal. Calcd for RuC₅₃H₄₂F₆P₃O₂N: C, 61.63;

H, 4.10; N, 1.35. Found: C, 62.22; H, 4.12; N, 1.31. 115. ³¹P-

1

4

{¹H} (CDCl₃) δ 37.72 (s); H (CDCl₃) δ 5.34 (t, 1H, J _HP) 1.5

Hz, RudCdCH), 5.72 (d, 2H, J _HH) 2.6 Hz, H-1,3), 6.04 (m,

3H, H-2 and H-4,7 or H-5,6), 6.82-7.48 (m, 34H, Ph, H-4,7 or

H-5,6 and C₆H₂H₂NO₂-4), 7.91 (d, 2H, J _HH) 8.8 Hz, C₆H₂H₂-

NO₂-4); ¹³C{¹H} (CDCl₃) δ 84.59 (s, C-1,3), 98.75 (s, C-2), 116.43

(s, C-3a,7a), 117.49 (s, C_â), 123.75, 124.31 and 126.61 (s, C-4,7,

C-5,6 and CH of C₆H₄NO₂-4), 128.68-133.98 (m, Ph and CH

of C₆H₄NO₂-4), 136.75 and 146.21 (s, C of C₆H₄NO₂-4), 348.98

(t, ²J _CP) 16.5 Hz, RudC_R); ∆δ(C-3a,7a) ) -14.27. For 2b. 52%

(0471 g). 837. Anal. Calcd for RuC₄₃H₃₆F₆P₃O₂N: C, 56.95; H,

4.00; N, 1.54. Found: C, 57.35; H, 4.18; N, 1.72. 108. ³¹P{¹H}

1

(CDCl₃) δ 71.66 (s); H (CDCl₃) δ 2.44 and 2.84 (m, 2H each

one, P(CH₂)₂P), 4.38 (s, 1H, RudCdCH), 5.95 (t, 1H, J _HH

)

(24) Oro, L. A.; Ciriano, M. A.; Campo, M.; Foces-Foces, C.; Cano,

F. H. J . Organomet. Chem. 1985, 289, 117.

(25) Gamasa, M. P.; Gimeno, J .; Gonza´lez-Bernardo, C.; Mart´ın-

Vaca, B. M.; Monti, D.; Bassetti, M. Organometallics 1996, 15, 302.

(26) Lawrance, G. A.; Lay, P. A.; Sargeson, A. M.; Taube, H. Inorg.

Synth. 1986, 24, 258.

(27) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara, N.

Synthesis 1980, 627.

(28) (a) Lavastre, O.; Cabioch, S.; Dixneuf, P. H.; Vohlidal, J .

Tetrahedron 1997, 53, 7595. (b) Lavastre, O.; Ollivier, L.; Dixneuf, P.

H.; Sibandhit, S. Tetrahedron 1996, 52, 5495.

(23) Colbert, M. C. B.; Lewis, J .; Long, N. J .; Raithby, P. R.; Bloor,

D. A.; Cross, G. H. J . Organomet. Chem. 1997, 531, 183.

Donor-Acceptor Indenylruthenium(II) Complexes

Organometallics, Vol. 18, No. 4, 1999 595

2.2 Hz, H-2), 6.14 (d, 2H, J _HH) 2.2 Hz, H-1,3), 6.30 and 7.62

(d, 2H each one, J _HH) 8.7 Hz, C₆H₄NO₂-4), 6.69-7.52 (m, 24H,

Ph, H-4,7 and H-5,6); ¹³C{¹H} (CDCl₃) δ 25.81 (m, P(CH₂)₂P),

79.75 (s, C-1,3), 97.96 (s, C-2), 113.23 (s, C-3a,7a), 115.36 (s,

C_â), 123.24, 123.52 and 124.96 (s, C-4,7, C-5,6 and CH of C₆H₄-

NO₂-4), 129.16-133.43 (m, Ph and CH of C₆H₄NO₂-4), 135.00

and 145.14 (s, C of C₆H₄NO₂-4), 348.85 (t, ²J _CP) 16.5 Hz, Rud

C_R); ∆δ(C-3a,7a) ) -17.47. For 2c. 49% (0.437 g). 834. Anal.

Calcd for RuC₄₂H₃₄F₆P₃O₂N: C, 56.50; H, 3.83; N, 1.56.

Found: C, 55.92; H, 3.75; N, 1.48. 117. ³¹P{¹H} (CDCl₃) δ 1.69

) 2.3 Hz, H-1,3), 4.82 (t, 1H, J _HH) 2.3 Hz, H-2), 4.91 (d, 2H,

²J _HP) 14.5 Hz, CH₂), 6.07 and 6.84 (m, 2H each one, H-4,7

and H-5,6), 7.07-8.06 (m, 45H, Ph); ¹³C{¹H} ((CD₃)₂CO) δ

2

21.39 (d, J _CP) 54.2 Hz, CH₂), 74.84 (s, C-1,3), 93.03 (d, J _CP

) 12.2 Hz, C_â), 95.46 (s, C-2), 110.15 (s, C-3a,7a), 111.38 (m,

Ru-C_R), 119.85-139.60 (m, Ph, C-4,7 and C-5,6); ∆δ(C-3a,-

7a) ) -20.55.

Syn th esis of [Ru {CtCCHdCH(CHdCH)_nR}(η⁵-C₉H₇)-

(P P h ₃)₂] (n ) 0, R ) C₆H₄NO₂-4 [(E,Z)-7a ], C₄H₂ONO₂-2,3

[(E,Z)-8a ], C₄H₂SNO₂-2,3 [(E)-8b], C₆H₄CN-4 [(E,Z)-13],

C₅H₄N-4 [(E)-16], C₅H₄F eC₅H₅[(E)-18]; n ) 1, R ) C₆H₄-

NO₂-4 [(EE,ZE)-7b]), a n d [Ru {CtCCHd(C₆H₄NO₂-3)₂}(η⁵-

C₉H₇)(P P h ₃)₂] (9). Gen er a l P r oced u r e. A solution of LiⁿBu

(1.6 M in hexane, 0.625 mL, 1 mmol) was added to a solution

of [Ru{CtCCH₂(PPh₃)}(η⁵-C₉H₇)(PPh₃)₂][PF₆] (6) (1.186 g, 1

mmol) in 25 mL of THF kept at -20 °C. After the addition

was complete, the color of the solution had changed from yellow

to violet. After stirring the resulting mixture for 15 min, the

corresponding aldehyde or ketone (3 mmol) was added and

stirred for 30 min after warming to room temperature. The

solvent was then removed in vacuo, and the solid residue was

transferred to an Alox I chromatography column. Elution with

hexane/diethyl ether (3/1) gave an orange band from which

the corresponding σ-enynyl complex was obtained by sol-

vent removal. Yield, IR (KBr, ν(CtC), ν(CtN), cm^-1), and

analytical or mass spectral data (FAB m/e) are as follows. For

7a . 90% (0.822 g). 2034 (E and Z isomers). Anal. Calcd for

RuC₅₅H₄₃O₂P₂N: C, 72.35; H, 4.75; N, 1.53. Found: C, 71.89;

H, 4.96; N, 1.36. For 7b. 73% (0.685 g). 2033 (EE and ZE

isomers). Anal. Calcd for RuC₅₇H₄₅O₂P₂N: C, 72.91; H, 4.83;

N, 1.49. Found: C, 72.91; H, 4.88; N, 1.42. For 8a . 41% (0.370

g). 2027 (E and Z isomers). MS for RuC₅₃H₄₁O₃P₂N: [M⁺] )

903, [M⁺- PPh₃] ) 642. For 8b. 46% (0.423 g). 2021. MS for

RuC₅₃H₄₁O₂P₂NS: [M⁺] ) 919, [M⁺- PPh₃] ) 657. For 9. 88%

(0.909 g). 2034. Anal. Calcd for RuC₆₁H₄₆O₄P₂N₂: C, 70.85; H,

4.48; N, 2.70. Found: C, 70.25; H, 4.82; N, 2.58. For 13. 71%

(0.634 g). 2041 (CtC, E and Z isomers), 2216 (CtN, E isomer),

2137 (CtN, Z isomer). Anal. Calcd for RuC₅₆H₄₃P₂N: C, 75.32;

H, 4.85; N, 1.56. Found: C, 74.59; H, 5.01; N, 1.49. For 16.

83% (0.721 g). 2039. Anal. Calcd for RuC₅₄H₄₃P₂N: C, 74.55;

H, 4.98; N, 1.61. Found: C, 73.95; H, 4.62; N, 1.58. For 18.

67% (0.654 g). 2048. Anal. Calcd for FeRuC₅₉H₄₈P₂: C, 72.61;

H, 4.96. Found: C, 72.36; H, 4.93.

1

(s); H (CDCl₃) δ 4.57 (s, 1H, RudCdCH), 4.74 and 5.10 (m,

1H each one, PCH_aH_bP), 5.86 (t, 1H, J _HH) 2.5 Hz, H-2), 6.33

(m, 4H, H-1,3 and H-4,7 or H-5,6), 7.10-7.44 (m, 24H, Ph,

H-4,7 or H-5,6 and C₆H₂H₂NO₂-4), 7.66 (d, 2H, J _HH) 8.6 Hz,

C₆H₂H₂NO₂-4); ¹³C{¹H} (CDCl₃) δ 45.62 (t, J _CP) 29.0 Hz,

PCH₂P), 80.69 (s, C-1,3), 95.81 (s, C-2), 111.92 (s, C-3a,7a),

117.62 (s, C_â), 124.14, 124.61, 126.02 and 128.82 (s, C-4,7, C-5,6

and CH of C₆H₄NO₂-4), 129.62-133.70 (m, Ph), 135.83 and

2

145.93 (s, C of C₆H₄NO₂-4), 352.42 (t, J _CP) 14.7 Hz, Rud

C_R); ∆δ(C-3a,7a) ) -18.78.

Syn th esis of [Ru (CtC-C₆H₄NO₂-4)(η⁵-C₉H₇)L₂] (L₂

)

2P P h ₃(3a ), d p p e (3b), d p p m (3c)). Gen er a l P r oced u r e.

A solution of 2a -c (1 mmol) in 50 mL of dichloromethane was

treated with Al₂O₃(1.019 g, 10 mmol), and the mixture was

stirred at room temperature for 1 h. The solution was then

evaporated to dryness, and the solid residue was extracted

with diethyl ether. The evaporation of the diethyl ether gave

3a -c as red solids. Yield, IR (KBr, ν(CtC), cm^-1), and

analytical data are as follows. For 3a . 79% (0.701 g). 2051.

Anal. Calcd for RuC₅₃H₄₁P₂O₂N: C, 71.77; H, 4.66; N, 1.58.

Found: C, 70.95; H, 4.33; N, 1.62. For 3b. 68% (0.507 g). 2060.

Anal. Calcd for RuC₄₃H₃₅P₂O₂N: C, 67.88; H, 4.64; N, 1.84.

Found: C, 67.25; H, 4.58; N, 1.69. For 3c. 42% (0.314 g). 2052.

Anal. Calcd for RuC₄₂H₃₃P₂O₂N: C, 67.56; H, 4.45; N, 1.87.

Found: C, 66.97; H, 4.46; N, 1.80.

Syn th esis of [Ru (CtC-C₆H₄R-4)(η⁵-C₉H₇)(P P h ₃)₂] (R )

CtC-C₆H₄NO₂-4 (4), NdCH-C₆H₄NO₂-4 (5)). A mixture of

[RuCl(η⁵-C₉H₇)(PPh₃)₂] (1a ) (0.776 g, 1 mmol), NaPF₆(0.336

g, 2 mmol), and HCtC-C₆H₄R-4 (R ) CtC-C₆H₄NO₂-4 or

NdCH-C₆H₄NO₂-4) (2 mmol) in 50 mL of methanol was

heated under reflux for 30 min. The resulting solution was

evaporated to dryness, and the solid residue was dissolved in

dichloromethane (ca. 20 mL) and filtered into stirred diethyl

ether (ca. 100 mL) to give a brown solid precipitate. The

resulting solid was washed with diethyl ether (2 × 20 mL),

dissolved in dichloromethane (ca. 25 mL), and treated, at room

temperature, with Al₂O₃(for complex 4; 1.019 g, 10 mmol) or

K₂CO₃(for complex 5; 1.382 g, 10 mmol) for 1 h. The solution

was then evaporated to dryness, and the residue was extracted

with diethyl ether. The evaporation of the diethyl ether gave

4 and 5 as red solids. Yield, IR (KBr, ν(CtC), cm^-1), and

analytical or mass spectral data (FAB m/e) are as follows. For

4. 60% (0.592 g). 2070, 2207. Anal. Calcd for RuC₆₁H₄₅P₂O₂N:

C, 74.22; H, 4.59; N, 1.41. Found: C, 73.85; H, 4.22; N, 1.30.

For 5. 51% (0.505 g). 2069. MS for RuC₆₀H₄₆P₂O₂N₂: [M⁺] )

990, [M⁺-PPh₃] ) 728.

Syn th esis of [Ru (CtN)(η⁵-C₉H₇)(P P h ₃)₂] (10). A mixture

of [RuCl(η⁵-C₉H₇)(PPh₃)₂] (1a ) (0.776 g, 1 mmol), and KCN

(0.260 g, 4 mmol) in 50 mL of methanol was heated under

reflux for 1 h. The resulting solution was concentrated (ca. 20

mL) to give, after cooling to -10 °C, yellow crystals of complex

10. Yield, IR (KBr, ν(CtN), cm^-1), analytical, and NMR

spectroscopic data (ppm) are as follows. 81% (0.767 g). 2071.

Anal. Calcd for RuC₄₆H₃₇P₂N: C, 72.05; H, 4.86; N, 1.82.

Found: C, 71.35; H, 4.91; N, 1.72. ³¹P{¹H} (CD₂Cl₂) δ 51.94

1

(s); H (CD₂Cl₂) δ 4.57 (d, 2H, J _HH) 2.5 Hz, H-1,3), 5.17 (t,

1H, J _HH) 2.5 Hz, H-2), 6.45 and 6.90 (m, 2H each one, H-4,7

and H-5,6), 7.13-7.69 (m, 30H, Ph); ¹³C{¹H} (CD₂Cl₂) δ 73.87

(s, C-1,3), 94.43 (s, C-2), 109.26 (s, C-3a,7a), 123.89 (s, C-4,7

or C-5,6), 127.45-137.61 (m, Ph and C-4,7 or C-5,6), 143.49

Syn th esis of [Ru {CtCCH₂(P P h ₃)}(η⁵-C₉H₇)(P P h ₃)₂][P F₆]

(6). A mixture of [RuCl(η⁵-C₉H₇)(PPh₃)₂] (1a ) (0.776 g, 1 mmol),

NaPF₆(0.336 g, 2 mmol), HCtCCH₂(OH) (0.118 mL, 2 mmol),

and PPh₃(2.622 g, 10 mmol) in 50 mL of methanol was stirred

at room temperature for 8 h. A yellow suspension was formed.

The solvent was then decanted, and the solid residue was

dissolved in dichloromethane (ca. 40 mL) and filtered over

kieselguhr. The resulting solution was evaporated to dryness,

and the yellow solid obtained was washed with diethyl ether

(2 × 20 mL) and vacuum-dried. Yield, IR (KBr, ν(PF₆^-),

ν(CtC), cm^-1), analytical, and NMR spectroscopic data (ppm)

are as follows. 65% (0.771 g). 837, 2087. Anal. Calcd for

RuC₆₆H₅₄F₆P₄: C, 66.83; H, 4.59. Found: C, 67.11; H, 4.69.

³¹P{¹H} ((CD₃)₂CO) δ 18.51 (t, ⁵J _PP) 4.6 Hz, CH₂-PPh₃), 51.32

(d, ⁵J _PP) 4.6 Hz, Ru-PPh₃); ¹H ((CD₃)₂CO) δ 4.40 (d, 2H, J _HH

2

(t, J _CP) 22.7 Hz, Ru-CtN); ∆δ(C-3a,7a) ) -21.44.

Syn th esis of [(η⁵-C₉H₇)(P P h ₃)₂Ru {(µ-CtN)M(CO)₅}] (M

) Cr (11a ), W (11b)), [(η⁵-C₉H₇)(P P h ₃)₂Ru {(µ-CtCCHd

CH-C₆H₄CtN-4)M(CO)₅}] (M ) Cr [(E, Z)-14a ], W [(E, Z)-

14b]), a n d [(η⁵-C₉H₇)(P P h ₃)₂Ru {(µ-CtCCHdCH-C₅H₄N-

4)M(CO)₅}] (M ) Cr [(E)-17a ], W [(E)-17b]). Gen er a l

P r oced u r e. A solution of 10, (E, Z)-13 or (E)-16 (1 mmol) in

25 mL of THF was treated with a THF solution of [M(CO)₅-

(THF)] (M) Cr, W) (1 mmol), and the mixture was stirred at

room temperature for 1 h. The solution was then evaporated

to dryness, and the orange solid residue was washed with

hexane (ca. 10 mL). Yield, IR (KBr, ν(CtC), ν(CtO), ν(CtN),

cm^-1), analytical, and NMR spectroscopic data (ppm) are as

follows. For 11a . 70% (0.678 g). 1884, 1930, 2064, 2109. Anal.

596 Organometallics, Vol. 18, No. 4, 1999

Cadierno et al.

Calcd for CrRuC₅₁H₃₇O₅P₂N: C, 63.88; H, 3.89; N, 1.46.

5, 1064 nm, 10 ns pulses, 10 Hz) were focused into a cylindrical

cell (7 mL) containing the sample. The fundamental intensity

was altered by rotation of a half-wave plate placed between

crossed polarizers and measured with a photodiode. An ef-

ficient condenser system was used to collect the light scattered

at the harmonic frequency (532 nm) that was detected by a

photomultiplier. Discrimination of the second-harmonic light

from the fundamental light was accomplished by a low-pass

filter and a 532-nm interference filter. Actual values for the

intensities were retrieved by using gated integrators. In all

experiments, the incident light was vertically polarized along

the z axis. All HRS measurements were performed in dichlo-

romethane, and the known hyperpolarizability of p-nitroa-

niline in this solvent was used as a reference.²⁹The samples

were passed through a 0.45-µm filter (contaminated samples

often produce spurious signals), and were checked for mul-

tiphoton fluorescence that can interfere with the HRS signal.³⁰

Further details of the experimental procedure have been

reported elsewhere.³¹

Found: C, 64.34; H, 4.18; N, 1.43. ³¹P{¹H} (CD₂Cl₂) δ 54.61

1

(s); H (CD₂Cl₂) δ 4.34 (d, 2H, J _HH) 1.5 Hz, H-1,3), 4.46 (t,

1H, J _HH) 1.5 Hz, H-2), 6.67 and 6.79 (m, 2H each one, H-4,7

and H-5,6), 6.92-7.75 (m, 30H, Ph); ¹³C{¹H} (CD₂Cl₂) δ 74.61

(s, C-1,3), 92.52 (s, C-2), 107.95 (s, C-3a,7a), 123.66 (s, C-4,7

or C-5,6), 127.80-136.93 (m, Ph and C-4,7 or C-5,6), 155.97

2

(t, J _CP) 20.7 Hz, Ru-CtN), 216.02 and 220.76 (s, CtO);

∆δ(C-3a,7a) ) -22.75. For 11b. 85% (0.927 g). 1881, 1922,

2065, 2099. Anal. Calcd for RuWC₅₁H₃₇O₅P₂N: C, 56.16; H,

3.42; N, 1.28. Found: C, 55.96; H, 3.65; N, 1.22. ³¹P{¹H} (CD₂-

Cl₂) δ 54.19 (s); ¹H (CD₂Cl₂) δ 4.52 (d, 2H, J _HH) 2.4 Hz, H-1,3),

4.66 (t, 1H, J _HH) 2.4 Hz, H-2), 6.73 and 6.93 (m, 2H each

one, H-4,7 and H-5,6), 7.18-7.70 (m, 30H, Ph); ¹³C{¹H} (CD₂-

Cl₂) δ 75.12 (s, C-1,3), 92.56 (s, C-2), 107.81 (s, C-3a,7a), 123.62

(s, C-4,7 or C-5,6), 127.71-136.93 (m, Ph and C-4,7 or C-5,6),

2

154.80 (t, J _CP) 20.6 Hz, Ru-CtN), 198.18 and 201.84 (s,

CtO); ∆δ(C-3a,7a) ) -22.89. For 14a . 76% (0.825 g). 1909,

1946, 2041, 2073, 2220 (E and Z isomers). Anal. Calcd for

CrRuC₆₁H₄₃O₅P₂N: C, 67.52; H, 3.99; N, 1.29. Found: C, 67.72;

H, 3.87; N, 1.35. For 14b. 82% (0.999 g). 1907, 1980, 2039,

X-r a y Diffr a ction Stu d ies. X-ray suitable single crystals

were obtained by slow diffusion of pentane into THF solutions

of 7b and 9. Data collection, crystal, and refinement param-

eters are collected in Table 5. Data were collected with the

2074, 2221, 2232 (E and

Z isomers). Anal. Calcd for

RuWC₆₁H₄₃O₅P₂N: C, 60.21; H, 3.56; N, 1.15. Found: C, 59.84;

H, 3.41; N, 1.20. For 17a . 70% (0.743 g). 1896, 1933, 2036,

2065. Anal. Calcd for CrRuC₅₉H₄₃O₅P₂N: C, 66.79; H, 4.08;

N, 1.32. Found: C, 66.82; H, 3.97; N, 1.26. For 17b. 85% (1.014

g). 1896, 1927, 2034, 2069. Anal. Calcd for RuWC₅₉H₄₃O₅P₂N:

C, 59.41; H, 3.63; N, 1.17. Found: C, 60.05; H, 3.83; N, 1.09.

Syn th esis of [(η⁵-C₉H₇)(P P h ₃)₂Ru {(µ-CtN)Ru (NH₃)₅}]

[CF ₃SO₃]₃(12) a n d [(η⁵-C₉H₇)(P P h ₃)₂Ru {(µ-CtCCHdCH-

C₆H₄CtN-4)Ru (NH₃)₅}][CF₃SO₃]₃[(E, Z)-15]. Gen er a l P r o-

ced u r e. A solution of complex 10 or (E,Z)-13 (1 mmol) in 20

mL of acetone was treated with [Ru(NH₃)₅(OSO₂CF₃)][CF₃-

SO₃]₂(0.633 g, 1 mmol), and the mixture was stirred at room

temperature for 1 h. The solution was then concentrated (ca.

5 mL). The slow addition of diethyl ether (ca. 25 mL) allowed

the formation of a biphasic system affords, after 24 h, blue

crystals of 12 or red crystals of (E,Z)-15. Yield, IR (KBr,

ν(CtN), ν(CtC), ν(NH₃), cm^-1), analytical, and conductivity

(acetone, Ω^-1cm²mol^-1) data are as follows. For 12. 79% (1.106

g). 2006, 3314. Anal. Calcd for Ru₂C₄₉H₅₂F₉O₉N₆S₃P₂: C, 42.03;

H, 3.74; N, 6.00. Found: C, 41.44; H, 4.04; N, 5.30. 209. For

15. 53% (0.809 g). 2037, (CtC E and Z isomers), 2190 (CtN,

E isomer), 2222 (CtN, Z isomer), 3308 (NH₃, E and Z isomers).

Anal. Calcd for Ru₂C₅₉H₅₈F₉O₉N₆S₃P₂: C, 46.43; H, 3.83; N,

5.50. Found: C, 46.24; H, 3.78; N, 5.54. 215.

ω-2θ scan technique and a variable scan rate, with

a

maximum scan time of 60 s per reflection. Atomic scattering

factors were taken from International Tables for X-ray Crys-

tallography (1974).³²Geometrical calculations were made with

PARST97.³³The crystallographic plots were made with EU-

CLID.³⁴All calculations were made at the University of Oviedo

on the X-ray group ALPHA-AXP computers.

Com p lex (EE)-7b. Crystals contain one molecule of THF

and one of n-pentane. The unit cell parameters were obtained

from the least-squares fit of 25 reflections (with θ between 6°

and 11°). The final drift correction factors were between 0.99

and 1.05. On all reflections, profile analysis³⁵was performed.

Lorentz and polarization corrections were applied and the data

2

were reduced to |F_o| values.

The structure was solved by DIRDIF-96³⁶(Patterson meth-

ods and phase expansion). Isotropic full-matrix least-squares

2

refinement on |F_o| using SHELXL93³⁷was performed.

Finally, all hydrogen atoms were geometrically placed.

During the final stages of the refinement, the positional

parameters and the anisotropic thermal parameters of most

non-H-atoms were refined. Some C-atoms were isotropically

refined because of the thermal parameters were out of physical

meaning. The geometrically placed hydrogen atoms were

isotropically refined, riding on their parent atoms. Two highly

Syn t h esis of [R u {dCdC(H )CH dCH C₅H ₄F eC₅H ₅}(η⁵-

C₉H₇) (P P h ₃)₂][BF ₄] [(E)-19]. A solution of HBF₄‚Et₂O (1.9

mL, 1.5 mmol) in 10 mL of diethyl ether was added dropwise,

at -20 °C, to a solution of complex (E)-18 (0.976 g, 1 mmol) in

30 mL of THF. The reaction mixture was gradually warmed

to room temperature and then concentrated (ca. 5 mL).

Addition of diethyl ether (ca. 100 mL) gave complex (E)-19 as

a brown solid which was washed with diethyl ether (3 × 20

mL) and vacuum-dried. Yield, IR (KBr, ν(BF₄^-), cm^-1), analyti-

cal data, conductivity (acetone, Ω^1-cm²mol^-1), and NMR

spectroscopic data (ppm) are as follows. 71% (1.064 g). 1060.

Anal. Calcd for FeRuC₅₉H₄₉F₄P₂B: C, 66.62; H, 4.64. Found:

(29) Sta¨helin, M.; Burland, D. M.; Rice, J . E. Chem. Phys. Lett. 1992,

191, 245.

(30) (a) Hendricks, E.; Dehu, C.; Clays, K.; Bre´das, J . L.; Persoons,

A. In Polymers for Second-Order Nonlinear Optics; ACS Symposium

Series 601; Lindsay, G. A., Singer, K. D., Eds.; American Chemical

Society: Washington, DC, 1995; p 82. (b) Flipse, M. C.; de J onge, R.;

Woudenberg, R. H.; Marsman, A. W.; van Walree, C. A.; J enneskens,

L. W. Chem. Phys. Lett. 1995, 245, 297. (c) Morrison, I. D.; Denning,

R. G.; Laidlaw, W. M.; Stammers, M. A. Rev. Sci. Instrum. 1996, 67,

1445.

(31) (a) Clays, K.; Persoons, A. Rev. Sci. Instrum. 1992, 63, 3285.

(b) Houbrechts, S.; Clays, K.; Persoons, A.; Pikramenou, Z.; Lehn, J .-

M. Chem. Phys. Lett. 1996, 258, 485.

(32) International Tables for X-ray Crystallography; Kynoch Press:

Birmingham, U.K., 1974; Vol. IV.

1

C, 65.91; H, 4.89. 110. ³¹P{¹H} (CD₂Cl₂) δ 40.60 (s); H (CD₂-

Cl₂) δ 4.14 (s, 5H, C₅H₅), 4.23 and 4.30 (m, 2H each one, C₅H₄),

5.34 (bs, 1H, RudCdCH), 5.52 (d, 2H, J _HH) 2.4 Hz, H-1,3),

5.72 (t, 1H, J _HH) 2.4 Hz, H-2), 5.82 (d, 1H, J _HH) 15.2 Hz,

dCH), 6.15 (m, 2H, H-4,7 or H-5,6), 6.89-7.54 (m, 33H, Ph,

dCH and H-4,7 or H-5,6); ¹³C{¹H} (CD₂Cl₂) δ 66.99 and 69.84

(s, CH of C₅H₄), 70.34 (s, C₅H₅), 84.75 (s, C-1,3), 95.41 (s, C of

C₅H₄), 98.98 (s, C-2), 108.34 and 124.28 (s, dCH), 115.53 (s,

C-3a,7a), 118.55 (s, C_â), 123.43 and 130.70 (s, C-4,7 and C-5,6),

128.96-134.18 (m, Ph), 361.82 (t, ²J _CP) 16.5 Hz, RudC_R); ∆δ-

(C-3a,7a) ) -15.17.

(33) Nardelli, M. Comput. Chem. 1983, 7, 95.

(34) Spek, A. L. The EUCLID Package. In Computational Crystal-

lography; Sayre D., Ed.; Clarendon Press: Oxford, U.K., 1982; p 528.

(35) (a) Grant, D. F.; Gabe, E. J . J . Appl. Crystallogr. 1978, 11, 114.

(b) Lehman, M. S.; Larsen, F. K. Acta Crystallogr., Sect. A 1974, 30,

580.

(36) Beurskens, P. T.; Beurskens, G.; Bosman, W. P.; de Gelder, R.;

Garc´ıa-Granda, S.; Gould, R. O.; Israe¨l, R.; M. Smits, J . M. The

DIRDIF-96 Program System; Technical Report; Crystallography Labo-

ratory, University of Nijmegen: Nijmegen, The Netherlands, 1996.

(37) Sheldrick,G. M. SHELXL93. In Crystallographic Computing 6;

Flack, H. D., Parkanyi, P., Simon K., Eds.; IUCr/Oxford University

Press: Oxford, U.K., 1993; p 111.

HRS Mea su r em en ts. IR laser pulses generated with an

injection-seeded Q-switched Nd:YAG laser (Quanta-Ray GCR-

Donor-Acceptor Indenylruthenium(II) Complexes

Organometallics, Vol. 18, No. 4, 1999 597

Ta ble 5. Cr ysta llogr a p h ic Da ta for th e Com p lexes 9 a n d 7b

complex

formula

fw

cryst syst

space group

a (Å)

b (Å)

c (Å)

a (deg)

9

C

7b

₆₉H₆₂N₂O₆P₂Ru

C₆₆H₆₅NO₃P₂Ru

1083.20

monoclinic

C2/c

32.94(3)

15.73(5)

21.37(3)

90

96.46(5)

90

11004(38)

8

1178.21

triclinic

P1h

11.710(3)

14.977(6)

18.136(6)

65.40(3)

84.07(3)

81.02(3)

2854(2)

â (deg)

γ (deg)

V (Å³)

Z

2

1.36

1224

calcd density (g cm^-3

F(000)

)

1.31

4528

radiation (λ, Å)

cryst size (mm)

temp (K)

monochromator

Mo KR (0.710 73)

0.20 × 0.20 × 0.13

293

graphite cryst

0.39

Mo KR (0.710 73)

0.26 × 0.13 × 0.20

293

graphite cryst

0.39

m (mm^-1

)

diffraction geom

θ range for data collection (deg)

index ranges for data collection

ω - 2θ

1.24 - 22.98

0 e h e 12

-16 e k e 16

-19 e l e 19

8214

1.24 - 24.98

0 e h e 39

0 e k e 18

-25 e l e 25

9855

no. of reflns measd

no. of indep rflns

7921

667

0.084

R1 ) 0.094

wR2 ) 0.224

R1 ) 0.214

wR2 ) 0.241

9674

486

0.46

R1 ) 0.100

wR2 ) 0.192

R1 ) 0.520

wR2 ) 0.351

no. of variables

agreement between equiv rflns^a

final R factors (I > 2σ(I))

final R factors (all data)

a

R_int) ∑(I - I )/∑I.

disordered solvent molecules (pentane and THF) were found.

For both solvent molecules, the non-H-atoms were geometri-

cally fixed and isotropically refined. The H-atoms were geo-

metrically placed riding on their parent atoms and isotropically

refined with fixed temperature factors (1.2 times the temper-

ature factor of the parent carbon). In an attempt to improve

results, one new set of data (10067 reflections) was measured

at 200 K from a different crystal. Unfortunately, no significant

improvements were achieved.

Hydrogen atoms were geometrically placed. During the final

stages of the refinement, the positional parameters and the

anisotropic thermal parameters of the non-H-atoms were

refined. The geometrically placed hydrogen atoms were iso-

tropically refined with a common thermal parameter, riding

on their parent atoms. The two disordered THF solvent

molecules were isotropically refined. Their hydrogen atoms

were refined with a fixed (1.1 times the thermal parameter of

the bonded carbon atom) thermal parameter.

The function minimized was [Σω(F_o- F_c²)²/Σω(F_o²)²]^1/2(ω

Finally, a full-matrix least-squares refinement on |F_o| was

2

made using SHELXL93.³⁷The function minimized was [Σω(F_o

2

) 1/[σ²(F_o²) + (0.0964P)²] where P ) (max(F_o²,0) + 2F_c)/3 with

σ²(F_o²) from counting statistics). The maximum shift to esd

ratio in the last full-matrix least-squares cycle was 0.651. The

final difference Fourier map showed no peaks higher than 0.67

- F_c²)²/Σω(F_o²)²]^1/2(ω ) 1/[σ²(F_o²) + (0.1361P)²] where P )

(max(F_o², 0) + 2F_c²)/3 with σ²(F_o²) from counting statistics).

The maximum shift to esd ratio in the last full-matrix least-

squares cycle was 0.010. The final difference Fourier map

showed no peaks higher than 1.20 eÅ^-3(near the two disor-

eÅ^-3or deeper than -1.27 eÅ^-3

.

Com p lex 9. Crystals contain two molecules of THF. The

unit cell parameters were obtained from the least-squares fit

of 25 reflections (with θ between 4° and 10°). The final drift

correction factors were between 1.00 and 1.05. Profile analy-

sis³⁵was performed on all reflections. Lorentz and polarization

corrections were applied and the data were reduced to |F_o|

values.

The structure was solved by Patterson using the program

SHELXS86³⁸and expanded by DIRDIF.³⁹Isotropic least-

squares refinement was performed using SHELX76.⁴⁰At this

stage an empirical absorption correction was applied using

DIFABS.⁴¹

dered THF solvent molecules) or deeper than -1.81 eÅ^-3

.

Ack n ow led gm en t. This work was supported by the

Direccio´n General de Investigacio´n Cient´ıfica y Te´cnica

(Project PB96-0558), the EU (Human Capital Mobility

Program, Project ERBCHRXCT 940501), Fund and

Scientific Research-Flanders (G.0308.96), the Belgian

Government (IUAP-16), and the University of Leuven

(GOA/1/95). We thank the Ministerio de Educacio´n y

Cultura (MEC) and the Fundacio´n para la Investigacio´n

Cient´ıfica y Te´cnica de Asturias (FICYT) for fellowships

to S.C. and V.C., respectively. S.H. is a Postdoctoral

Fellow and K.C. a Senior Research Associate of the

Belgian National Fund for Scientific Research.

(38) Sheldrick, G. M. SHELX86. In Crystallographic Computing 3;

Sheldrick, G. M., Kruger, C., Goddard R., Eds.; Clarendon Press:

Oxford, U.K., 1985; p 175.

(39) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;

Garc´ıa-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The

DIRDIF Program System; Technical Report; Crystallography Labora-

tory, University of Nijmegen: Nijmegen, The Netherlands, 1992.

(40) (a) Sheldrick, G. M. SHELX76: Program for Crystal Struc-

ture Determination; University of Cambridge: Cambridge, U. K., 1976.

(b) Van der Maelen Ur´ıa J . F. Ph.D. Thesis, University of Oviedo,

1991.

Su p p or tin g In for m a tion Ava ila ble: Crystal structure

data for (EE)-7b and 9, including tables of atomic parameters,

anisotropic thermal parameters, bond distances, and bond

angles. Ordering information is given on any current masthead

page.

(41) Walker, N.; Stuart, D. Acta Crystallogr., Sect. A 1983, 39,

158.

OM980672M

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Synthesis and second-order nonlinear optical properties of donor-acceptor

DOI: 10.1021/om980672m

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