Synthesis of new hydride-carbyne and hydride-vinylcarbyne

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J. Am. Chem. SOC. 1993,115,4683-4689

4683

Synthesis of New Hydride-Carbyne and Hydride-Vinylcarbyne Complexes of Osmium( 11) by Reaction of OsH2C12(P-i-Pr3)2 with Terminal Alkynes Jesiis Espuelas, Miguel A. Esteruelas, Fernando J. Lahoz, Luis A. Oro,' and Natividad Ruiz Contribution from the Departamento de Quimica Inorghnica, Instituto de Ciencia de Materiales de Aragbn, Universidad de Zaragoza, CSIC, E-50009 Zaragoza, Spain Received October 30, 1992

Abstract: The dihydride-dichloro complex O S H ~ C ~ ~ ( P -(1) ~ -reacts P ~ ~ with ) ~ phenylacetylene, cyclohexylacetylene, and l-(trimethylsilyl)-1,4-pentadiyne, in hexane at 60 OC, to give the hydridecarbyne complexes OsHC12(CCH2R)(P-i-Pr3)2(R = Ph (2), Cy (3),CH2C=CSiMe3 (4)). The molecular structure of complex 2 was determined by X-ray crystallography. Crystals of 2 are orthorhombic, space group P212121,with unit cell dimensions a = 8.7490(3) A, b = 15.4051(5) A, and c = 22.4257(8) A. The structure was solved and refined using 4615 unique, observed ( F 1 S.Oa(F)) reflections; R = 0.022 and R, = 0.023. The geometry around the osmium can be described as a distorted octahedron with the two triisopropylphosphine ligands occupying the apical positions. The equatorial plane is formed by the carbyne and the hydride ligands mutually cis disposed and two chlorine atoms. The reaction of 1 with trimethylsilylacetylene leads to OsHC12(CCH3)(P-i-Pr3)2 (5), suggesting that the key intermediates of these processes are dihydrogenvinylidene species of osmium(I1). The hydride-vinylcarbyne complexes OsHC12(CCH=CH(CH3)CH2-

-

CHJ(P-i-Pr3)2 (8), OsHC12(CCH=CCH2CH2CH2CH2CH2)(P-i-Pr3)2 (9),and OSHC~~(CCH=C(CH~)~)(P-~-P~~)~ (11)were prepared by reaction of 1 with 3-methyl-1-pentyn-3-01, 1-ethynyl-1-cyclohexanol,and 2-methyl-1-buten3-yne, respectively. Complexes 8 and 9 were formed via the hydroxycarbyne intermediates OsHC12-

(CCH2C(OH)(CH3)CH2CH3)(P-i-Pr3)2 (6) and 0sHCl2(CCH2&OH)CH2CH2CH2CH2bH2)(P-i-Pr3)2 (7). The synthesis of the hydroxycarbyne OSHC~~(CCH~C(OH)P~~)(P-~-P~& (10) is also reported. Introduction The reactions of alkynes with transition metal hydride complexes generally result in the formation of vinyl derivatives by an insertion of thealkyne into the M-H bonds.' In this respect, we observed, during our investigations directed toward the determination of the reaction mechanisms of the hydrogenation2 and hydr~silylation~ of terminal alkynes catalyzed by OsHCl(CO)(P-i-Pr3)2, that this compound and the cation [OsH(C0)2(q1-O=CMe2)(P-i-Pr3)2]+ react with alkynes such as PhC2H, C2H2, MeC2C02Me,and HC2COzMe to give vinyl derivatives by insertion of the alkynes into the Os-H bond of these complexes. We also reported, as a part of our work in the field of homogeneous catalysis,6 that the tetrahydride OsH4(CO)(P-i-Pr3)2 complex catalyzes the hydrogen transfer reaction from 4 3 5

(1) Crabtree, R. H. The Organometallic Chemistry of the Transition Metals; J. Wiley and Sons: New York, 1988; pp 142-162. (2) Andriolo, A.; Esteruelas, M. A,; Meyer, U.; Oro, L. A,; SdnchezDelgado, R. A,; Sola, E.; Valero, C.; Werner, H. J . Am. Chem. SOC.1989, 111 , 7431.

(3) Esteruelas, M. A.; Oro, L. A,; Valero, C. Organometallics 1991, 10, 462. (4) Werner, H.; Esteruelas, M. A.; Otto, H. Organometallics 1986, 5, 2295. (5) Esteruelas, M. A.; Lahoz, F. J.; L6pez, J. A,; Oro, L. A,; Schliinken, C.; Valero, C.; Werner, H. Organometallics 1992, 11, 2034. (6) (a) Fernandez, M. J.; Esteruelas, M. A.; Jimenez, M. S.; Oro, L. A. Organometallics 1986, 5, 1519. (b) Esteruelas, M. A.; Sola, E.; Oro, L. A.; Werner, H.; Meyer, U. J. Mol. Catal. 1989, 53, 43. (c) Esteruelas, M. A,; Garcra, M. P.; L6pez, A. M.; Oro, L. A. Organometallics 1991.10, 127. (d) Esteruelas, M. A.; Garcia, M. P.; Lbpez, A. M.; Oro, L. A. Ibid. 1992, 11, 702. (e) Bianchini, C.; Meli, A.; Peruzzini, M.; Frediani, P.; Bohanna, C.; Esteruelas, M. A.; Oro, L. A. Ibid. 1992, 11, 138. ( f ) Esteruelas, M. A,; Herrero, J.; L6pez. A. M.; Oro, L. A.; Schulz, M.; Werner, H. Inorg. Chem. 1992,31,4013. (g) Esteruelas, M. A,;Oro, L. A.; Valero, C. Organometallics 1992, I I , 3362.

2-propanol to phenyla~etylene.~During the study designed to determine the mechanism of this reaction, we found that the tetrahydride OsH4(CO)(P-i-Pr3)2 complex reacts with the stoichiometric amount of phenylacetylene to give molecular hydrogen and the alkynyl-dihydrogen complex OsH(C2Ph)(CO)(q2-H2)(P-i-Pr3)~.~ The complex OsH4(CO)(P-i-Pr3)2is coordinatively saturated, and its activation involves the loss of one hydrogen molecule per molecule of tetrah~dride.~ In this way, the formation of OsH(C2Ph)(CO)(q2-H2)(P-i-Pr3)2 could be rationalized as the formal oxidative addition of a terminal alkyne to a dihydride complex of 16 electrons and subsequent intramolecular reduction. Because RC=CH is fairly acidic and the OsH2(CO)(P-i-Pr& fragment is probably rich in electrons, the formation of OsH(C2Ph)(CO)(q2-H2)(P-i-Pr3)2 could involve the initial protonation of O S H ~ ( C O ) ( P - ~ -toP ~give ~ ) the ~ cationic intermediate [OsH(C0)(q2-H2)(P-i-Pr3)2]+ loand subsequent coordination of [PhC=C]-.8 The complex OsH(C2Ph)(CO) (q2-H2)(P-i-Pr3)~is isoelectronic and isostructural with OSHC~(CO)(~~-H~)(P-~-PQ)~.~~ However, they show a marked difference in reactivity toward phenylacetylene. Whereas the hydridechloro compound reacts with phenylacetylene to give the vinyl complex Os( (E)-CH=CHPh)Cl(CO)(P-i-Pr3)2,2the alkynyl analogue leads to the bis(alkyny1) derivative OS(C~P~)~(CO)(P-~-P~~)~.~ This derivative, which can also be obtained directly by reaction of OsH1(CO)(P-i-Pr3)2 with (7) Esteruelas, M. A,; Sola, E.; Oro, L. A.; Werner, H.; Meyer, U.J . Mol. Catal. 1988, 45, 1 .

(8) Esteruelas, M. A.; Oro, L. A.; Valero, C. Organometallics, in press. (9) Esteruelas, M. A,; Valero, C.; Oro, L. A,; Meyer, U.; Werner, H. Inorg. Chem. 1991, 30, 1159. (IO) This complex was recently isolated in our laboratory by reaction of [ (P-i-Pr,)2(CO)HO~(p,g4-BH4)0~H(CO)(P-i-Pr3)2]+ with H2.See: Esteruelas, M. A.; Garcia, M. P.; L6pez, A. M.; Oro, L. A.; Ruiz, N.; Schliinken, C.; Valero, C.; Werner, H. Inorg. Chem. 1992, 31, 5580. (1 1) Esteruelas, M. A,; Sola, E.; Oro, L. A.; Meyer, U.; Werner, H. Angew. Chem., Int. Ed. Engl. 1988, 27, 1563.

0002-7863/93/1515-4683$04.00/00 1993 American Chemical Society

Espuelas et al.

4684 J. Am. Chem. SOC.,Vol. 115, No. 11, 1993 excess phenylacetylene,12 was detected during the hydrogen transfer reaction from 2-propanol to phenyla~etylene.~.~~ Two years ago, the synthesis, molecular structure, and catalytic activity of the dihydride4ichloro complex O S H ~ C ~ ~ ( P - G P ~ ~ ) ~ (1) werereported.I3 This compound catalyzes the hydrogenation of olefins, dienes and a,@-unsaturated ketones. When we attempted the hydrogenation of phenylacetylene in the presence of 1, we observed that rapid deactivation of the catalyst occurs. This unexpected finding prompted us to explore the reactivity of this complex toward terminal alkynes. During these studies, we discovered an unusual reaction pattern. The reaction of 1 with terminal alkynes leads to hydride-carbyne complexes. In this paper, we report the synthesis and characterization of new hydride-carbyne and hydride-vinylcarbyne osmium(I1) complexes, which have been obtained by direct reaction between a transition metal dihydride compound and terminal alkynes. Recently, the synthesis of some hydridecarbyne rhenium complexes which were prepared by reaction of rhenium polyhydrides and alkynes, was reported. However, in this case, the addition of an electrophile was necessary.I4

Results and Discussion Treatment of a suspension of 0 ~ H ~ C l ~ ( P r - i -(1) P r ~with )~ phenylacetylene, cyclohexylacetylene, or 1-(trimethylsily1)- 1,4pentadiyne in hexane at 60 OC results in the formation of solids, which according to the elemental analysis, correspond apparently to 1:l adducts of the starting material and the alkynes. The IR, IH, 3lP{lH}, and I3C{lH) N M R spectra of these solids suggest that the products obtained from these reactions are the carbyne complexes 2-4 (eq 1).

PiPr3

R= Ph (2); Cy (3);CH2C=CSiMe3 (4)

The presence of a hydride ligand in these complexes is inferred from the IR and IH N M R spectra. The IR spectra in Nujol show a strong ~ ( 0 s - H )absorption between 2160 and 2185 cm-I, while the IH N M R spectra in benzene-d6 all contain a triplet between -6.57 and -6.88 ppm, with a P-H coupling constant of about 16 Hz. The sp-carbon atom of the carbyne ligands appears in the '3C(IH) N M R spectra as a triplet between 264 and 270 ppm, with a P-C coupling constant of about 11 Hz. The 31P(lH} N M R spectra show a singlet, indicating that the two phosphine ligands are equivalent. The definitive characterization of 2-4 as hydride-carbyne compounds came from an X-ray diffraction experiment on a single crystal of 2. A view of the molecular geometry of this complex is shown in Figure 1. Selected bond distances and angles are listed in Table I. The geometry of the complex can be rationalized as a distorted octahedron with the two phosphorus atoms of the triisopropylphosphine ligands occupying the apical positions (P( 1)-0s-P(2) = 168.50(4)'). The equatorial plane is formed by the carbyne and the hydride ligands mutually cis disposed (H-Os-C(19) = 94(2)O) and the two chlorine atoms also cis disposed (Cl(1)Os-Cl(2) = 88.65( 5 ) ' ) . The most conspicuous feature of the structure is the very short Os-C(19) bond length at 1.711(4) A, which is fully consistent (12) Werner, H.; Meyer, U.; Esteruelas, M. A,; Sola, E.; Oro, L. A. J . Organomet. Chem. 1989, 366, 187. (13) Aracama, M.; Esteruelas, M. A,; Lahoz, F. J.; L6pez, J . A.; Meyer, U.; Oro, L. A,; Werner, H. Inorg. Chem. 1991, 30, 288. (14) Leeaphon, M.; Fanwick, P. E.; Walton, R. A. J. Am. Chem. SOC.

1992, 114, 1890.

Figure 1. ORTEP diagram of complex 2. Thermal ellipsoids are shown a t 50%. Table I. Selected Bond Distances (A)and Angles (deg) for the (2) Complex [OSHCI~(CCH~P~)(P-~-P~~)~] Os-P(l) Os-P(2) 2.424( 1) 2.429(1) os-CI( 1 ) 2.488(1) Os-CI(2) 2.498( 1) OS-C( 19) 1.711(4) OS-H 1.437(40) C(19)-C(20) 1.475(7) C(22)-C(23) 1.373(8) C(20)-C(21) 1.532(7) C(23)-C(24) 1.351(12) C(21)-C(22) 1.364(8) C(24)-C(25) 1.367(13) C(21)-C(26) 1.375(8) C(25)-C(26) 1.399(8) P(1 )-C(1) 1.846(5) P(2)-C(10) 1.847(5) 1.865(6) 1.863(5) P(2)-C(13) P(l)-C(4) 1.857 (6) 1.857(5) P(2)-C(16) pu-c(7) P( l)-Os-P(2) P( 1)-os-C1( 1) P( l)-OS-C1(2) P( 1)-os-C( 19) P( l)-Os-H P(2)-0s-C1( 1) P( 2)-0s-C1(2) P(2)-0s-C( 19) OS-C( 19)-C(20) C(19)-C(2C-C(21) C(2O)-C(21)-C(22) C(2O)-C(21)-C(26) C(22)-C(21)-C(26)

168.50(4) 86.50(4) 95.04(4) 92.7(2) 78(2) 87.41(4) 94.56(4) 91.4(2) 172.4(4) 117.7(4) 118.3(4) 121.5(5) 120.2(5)

P(2)-Os-H Cl(l)-Os-C1(2) Cl( 1)-Os-C( 19) Cl(l)-Os-H C1(2)-0s-C(19) C1(2)-Os-H C( 19)-0~-H

9 1(2) 8 8.65( 5 ) 168.7(2) 75(2) 102.6(2) 163(2) 94W

C(21)-C(22)-C(23) C(22)-C(23)-C(24) C(23)-C(24)-C(25) C(24)-C(25)-C(26) C(21)-C(26)-C(25)

119.9(6) 121.1(7) 119.7(6) 120.2(8) 118.9(6)

with a Os-C( 19) triple bond formulation. Os-C (carbyne) bond lengths previously reported are between 1.75(1) and 1.84(2) 8,.l5 So, the Os-C(19) bond length is the shortest known osmiumcarbyne distance. The C( 19)-C(20) distance and C( 19)-C(20)C( 2 1) angle are 1.475 (7) 8, and 117.7(4)O , respectively. A slight bending in the Os-C( 19)-C(20) moiety is present (Os-C( 19)C(20) = 172.4(4)'); similar values were found for related complexes.16 Furthermore, it should be mentioned that the Os-Cl(1) bond distance (C1 trans to C(19)) is 0.01 8,shorter than the Os-Cl(2) distance (C1 trans to H), which can be assigned to the different trans-influence of the carbyne and hydride ligands. The Os-P and Os-H distances are clearly in the expected range and deserve no further comment. (15) Schubert,U.SolidStateStructuresofCarbyneComplexes. In Carbyne Complexes;Fischer, H., Hofmann, P., Kreissl, F. R., Schr0ck.R. R.,Schubert, U., Weiss, K., Eds.; VCH Verlagsgesellschaft mbH: Weinheim, 1988; p 53. (16) (a) Clark, G. R.; Marsden, K.; Roper, W. R.; Wright, L. J. J . Am. Chem. SOC.1980,102,6570. (b) Clark, G. R.; Edmonds, N. R.; Pauptit, R. A,; Roper, W. R.; Waters, J. M.; Wright, A. H. J. Organomet. Chem. 1983, 244, C57. (c) Roper, W. R. J . Organomet. Chem. 1986,300,167. (d) Clark, G.R.;Cochrane,C. M.; Marsden,K.;Roper, W. R.; Wright,L. J.J. Organomet. Chem. 1986, 315, 211.

New Hydride-Carbyne and - Vinylcarbyne Complexes

Scheme I

PiPr, H-

OS

Cl'l

C 'I PIFT3

-

PiPr3

CI'

I

C 'I Rpr3

J. Am. Chem. Soc.. Vol. 115, No. 11, 1993 4685

-

-

ization dihydride dihydrogen, shown in Scheme I, involves a formal two-electron reduction of the osmium center (d4 d6), which therefore, must favor the alkyne vinylidene transformation. (iii) The electrophilic character of the dihydrogen complexes has been previously demonstrated. A common property of these compounds seems to be that the coordinated dihydrogen ligand is readily d e p r ~ t o n a t e d . ~ ~ Experimental indications in favor of the participation of vinylidene intermediates, in the formation of 2-4 from 1, were also found. Treatment of a suspension of 1 in hexane with (trimethylsily1)acetylene in a 1:3molar ratio leads to the complex OsHC12(CCH3)(P-i-Pr3)2 (5) according to eq 2.

-

PiPr3

The reactions shown in eq 1 merit further consideration. It was previously reported that the addition of an electrophile to an octahedral alkyenylidene complex results in transformation of the alkenylidene group into a carbyne ligand.I7 M O calculations predict that the regioselectivity of the reaction is governed by a significant charge localized on the @-Catom of the M=C=CHR unit,l* which should therefore undergo electrophilic attack. In this respect, the formation of 2-4 could be rationalized as the electrophilic attack of an acidic hydrogen atom to the 0-C atom of an Os=C=CHR unit. Scheme I summarizes a reaction mechanism, which is consistent with our proposal for the formation of 2-4 from 1. Since we had a 16-electron complex (l),it could thus undergo the nucleophilic attack of the alkyne to give dihydride-a-alkyne-osmium(IV)intermediates, in equilibrium with dihydrogen-?r-alkyne-osmium(I1) species. This formal reduction d4 d6 should favor isomerization from the a-alkyne complexes into vinylidene intermediates, most probably, via a concerted mechanism. The subsequent electrophilic attack of the acidic hydrogen of the dihydrogen ligands to the p-C atom of the vinylidenes could lead to the hydride-carbyne complexes

-

2-4.

In favor of the mechanism shown in Scheme I, the following should be noted. (i) Complex 1 is a useful starting material in preparing dihydrogen complexes. Recent studies carried out in our laboratory have shown that the simple coordination of pyrazole (Hpz) to 1 gives rise to the complex OsC12(v2-H2)(Hpz)(P-iPr3)2, which has been characterized by X-ray ana1y~is.l~So, it is reasonable to assume that the necessary a-coordination of the alkyne to the osmium atom in 1 produces the transformation of Os(H)2 into Os(s2-H2). (ii) The preparation of vinylidene complexes from terminal alkynes via a formal 1,2-hydrogen shift is a well-established process,20 which is very usual in octahedral d6 complexes. In these types of compounds, the alkyne-vinylidene rearrangement is promoted by an unfavorable 4e- 2-center d,-?r conflict, because they have no vacant d orbitals.2' However, in d4 complexes, this isomerization is rarely observed, and, to the best of our knowledge, only one example has been previously reported.22 The isomer-

There are precedents for the cleavage of the Si-C bond in related processes. The vinylidene ligand C=CH2 of the complex [OSI(s6-C6Hs)(C=CH2)(PMetBU2)]PF6 is produced from the reaction Of OS12(s6-C6H6)(PMetBU2)with AgPF6 in the presence of (trimethyl~ilyl)acetylene.*~ The same alkyne and the complex IrCl(P-i-Pr& have been used to prepare IrCl(C=CH2)(P-iPr3)2.25 It has been suggested that these desilylation processes are due to the presence, in the reaction media, of slight traces of H 2 0 , which act as an electrophilic reagent.24 In contrast to the vinylidene-silyl ligands, the alkynyl-silyl ligands seem to be extremely stable in an aqueous medium. Thus, the complex Rh( m S i M e 3 ) ( P M e 3 ) 3was prepared from cis-[RhH(mSiMe3)(PMe3)3]C1 in concentrated aqueous KOH.26 The different behavior of the groups C=CHSiMe3 and C=CSiMe, toward the electrophilic substitution could also explain why the alkyne 1-(trimethylsily1)-1,Cpentadiyne does not undergo desilylation during its reaction with 1. Wer11er2~previously reported that the square-planar iridiumvinylidene complexes IrCl(C=CHR)(P-i-Pr3)2 react with HBF4 in diethyl ether to give the cations [IrHCl(C=CHR)(P-i-Pr3)2]+, which are in equilibrium with the carbyne compounds [IrCl(CCH2R)(P-i-Pr3)2]+. These reactions could be considered as a precedent for our reactions; however, there are significant differences between both processes. Werner's reaction must be rationalized as the nucleophilic attack of a hydride ligand (H-) on the vinylidene group, while our reaction must be rationalized as the electrophilic attack of a proton (H+) on the vinylidene ligand. This difference could be related to the different nature of the fragments IrCl(C=CHR)(P-i-Pr3)2 and OsC12(C=CHR)(P-i-Pr&. While the first shows a Lewis base character reacting with Bransted acids, the second could have Lewis acid character, coordinating a weak Lewis base such as the dihydrogen ligand. The different charge on the metallic centers of both fragments

(23) (a) Crabtree, R. H.; Lavin, M.; Bonneviot, L. J . A m . Chem. SOC. 1986,108,4032. (b) Chinn, M. S.;Heinekey, D. M. J . Am. Chem. SOC.1987, 109, 5865. (c) Cappellani, E. P.; Maltby, P. A,; Morris, R. H.; Schweitzer, C. T.; St;ele, M. R. Inorg. Chem. 1989,28,4437. (d) Chinn, M. S.; Heinekey, D. M.; Payne, N. G.; Sofield, C. D. Organometallics, 1989, 8, 1824. (e) Bianchini, C.; Peruzzini, M.; Zanobini, F. J . Organomef. Chem. 1990, 390, C16. (f)Jia, G.; Morris, R. H. Inorg. Chem. 1990, 29, 581. ( 9 ) Chinn, M. (17) (a) Gallop, M . A.; Roper, W. R. Ado. Organomef. Chem. 1986, 25, S . ; Heinekey, D. M. J . A m . Chem. SOC.1990,112, 5166. (h) Jia,G.; Morris, 121. (b) Fischer, H.; Hofmann, P.; Kreissl, F. R.; Schrock, R. R.; Schubert, R . H . J . A m . C h e m . S o c 1991,113,875. . (i)Cazanoue,M.;He,Z.;Neibecker, U.; Weiss, K. Carbyne Complexes;VCH Verlagsgesellschaft mbH: Weinheim, D.; Mathieu, R. J . Chem. SOC.,Chem. Commun. 1991, 307. (j) Stepan van 1988. (c) Mayr, A. Comments Inorg. Chem. 1990, IO, 227. der Sluys, L.; Miller, M. M.; Kubas, G. J.; Caulton, K. G. J . Am. Chem. SOC. (18) Kostic, N . M.; Fenske, R. F. Organomefallics 1982, 1, 974. 1991, 113, 2513. (k) Jia, G.;Morris, R. H.; Schweitzer, C. T. Inorg. Chem. (19) Esteruelas, M. A.; Lahoz, F. J.; ORate, E.; Oro, L. A,; Ruiz, N . 1991, 30, 593. Manuscript in preparation. (20) Bruce, M. I . Chem. Rev. 1991, 91, 197. (24) Knaup, W.; Werner, H. J . Organomef. Chem. 1991, 411, 471. (21) Templeton, J. L.; Winston, P. B.; Ward, B. C. J . Am. Chem. SOC. (25) (a) Hohn, A.; Otto, H.; Dziallas, M.; Werner, H. J . Chem. SOC., 1981, 103, 7713. Chem. Commun. 1987,852. (b) Hohn, A,; Werner, H. J. Organomet. Chem. (22) The cationic alkyne complex [Mo(I$-HC~BU')(PM~~P~)~($-C