Complex OsHCl Research Articles

Structural and spectroscopic trends in the phosphine Os(II) complexes OsHCl(CO)(L)(PPh3)2

A series of four isostructural Os(II) complexes, OsHCl(CO)(L)(PPh3)2 with mutually trans triphenylphosphines and a stereospecifically introduced ligand L trans the hydride have been prepared by treating OsHCl(CO)(PPh3)3 with PMe3, PMe2Ph, PMePh2, and CNN=PPh3. These new derivatives have been characterized spectroscopically and by single crystal X-ray diffraction in three cases. In addition, an ordered non-twinned structure of the starting material has been obtained. Structures of three of these complexes as well as OsHCl(CO)(PPh3)3 provide an insight into the bonding and chemistry of this useful fragment.

Azo Complexes of Osmium(II): Preparation and Reactivity of Organic Azide and Hydrazine Derivatives

Mixed-ligand hydride complexes OsHCl(CO)(PPh3)2L (2) [L = P(OMe)3, P(OEt)3] were prepared by allowing OsHCl(CO)(PPh3)3 (1) to react with an excess of phosphite P(OR)3 in refluxing toluene. Dichloro compounds OsCl2(CO)(PPh3)2L (3, 4) were also prepared by reacting 1, 2 with HCl. Treatment of hydrides OsHCl(CO)(PPh3)2L (2), first with triflic acid and then with an excess of RN3 afforded organic azide complexes [OsCl(η(1)-N3R)(CO)(PPh3)2L]BPh4 (5-7) [R = 4-CH3C6H4CH2, C6H5CH2, C6H5; L = P(OEt)3]. Benzylazide complexes react in CH2Cl2/ethanol solution, leading to the imine derivative [OsCl(CO){η(1)-NH═C(H)C6H4-4-CH3}(PPh3)2{P(OEt)3}]BPh4 (8b). Hydrazine complexes [OsCl(CO)(RNHNH2)(PPh3)2L]BPh4 (9-11) [R = H, CH3, C6H5; L = P(OMe)3, P(OEt)3] were prepared by allowing hydride species OsHCl(CO)(PPh3)2L (2) to react first with triflic acid and then with an excess of hydrazine. Aryldiazene derivatives [OsCl(CO)(ArN═NH)(PPh3)2L]BPh4 (12, 13) were also prepared following two different methods: (i) by oxidizing arylhydrazine [OsCl(C6H5NHNH2)(CO)(PPh3)2L]BPh4 (11) with Pb(OAc)4 in CH2Cl2 at -30 °C; (ii) by allowing hydride species OsHCl(CO)(PPh3)2L (2) to react with aryldiazonium cations ArN2(+) (Ar = C6H5, 4-CH3C6H4) in CH2Cl2. The complexes were characterized spectroscopically and by X-ray crystal structure determination of OsHCl(CO)(PPh3)2[P(OEt)3] (2b) and [OsCl{η(1)-NH═C(H)C6H4-4-CH3}(CO)(PPh3)2{P(OEt)3}]BPh4 (8b).

Ruthenium hydride and vinyl complexes supported by nitrogen–oxygen mixed-donor ligands

The Schiff base, 2-chlorophenylsalicylaldimine (HL 1), is formed readily from salicylaldehyde and 2-chloroaniline. After deprotonation, this ligand is found to react as a bidentate mixed-donor chelate with the complexes [RuRCl(CO)(BTD)(PPh 3) 2] (R = H, CH CHC 6H 5, CH CHC 6H 4Me-4, CH CH t Bu, CC CPh CHPh; BTD = 2,1,3-benzothiadiazole) to form the compounds [RuR(L 1)(CO)(PPh 3) 2] through displacement of the chloride and BTD ligands. An analogous reaction occurs with the osmium complex [OsHCl(CO)(BTD)(PPh 3) 2] to provide [OsH(L 1)(CO)(PPh 3) 2]. The compound [Ru(CH CHC 6H 4Me-4)(L 2)(CO)(PPh 3) 2] is formed through reaction of salicylaldehyde (HL 2) with [Ru(CH CHC 6H 4Me-4)Cl(CO)(BTD)(PPh 3) 2] in the presence of base. Two further ligands were investigated to extend the study to encompass 5- and 4-membered chelates; 8-hydroxyquinoline (HL 3) and 2-hydroxy-4-methylquinoline (HL 4) react with [Ru(CH CHPh)Cl(CO)(BTD)(PPh 3) 2] and [Ru(CH CHC 6H 4Me-4)Cl(CO)(BTD)(PPh 3) 2] in the presence of base to yield the complexes [Ru(CH CHPh)(L 3)(CO)(PPh 3) 2] and [Ru(CH CHC 6H 4Me-4)(L 4)(CO)(PPh 3) 2], respectively. The crystal structure of [Ru(CH CHC 6H 4Me-4)(L 1)(CO)(PPh 3) 2] is reported.

Does type of phosphine affect rotational barrier of vinylidene in the complexes OsHCl(C [dbnd]CH 2)(L) 2 (L = phosphine)?

Density functional molecular orbital calculations at the BP86 level were performed to investigate rotational barrier of vinylidene ligand in the model complexes OsHCl(C CH 2)(L) 2 (L = PMe 3, PH 3, PF 3). Results of calculations indicate that the rotational barrier increases with the increasing π-accepting ability of phosphine. This result has been explained on the basis of the extent of π-interaction between metal and vinylidene ligand in the complexes.

OsHCl(CO)(PiPr3)2 as catalyst for ring-opening metathesis polymerization (ROMP) and tandem ROMP–hydrogenation of norbornene and 2,5-norbornadiene

Complex OsHCl(CO)(PiPr3)2 catalyzes the ring-opening metathesis polymerization (ROMP) of norbornene and 2,5-norbornadiene to give poly(norbornene) and poly(norbornadiene), respectively. In both cases the resulting polymers have a high cis (74–95%) content. The stereoregularity or tacticity of the cyclopentane and cyclopentene ring sequences in poly(norbornene) and poly(norbornadiene) estimated from the 13C{1H} NMR spectra of the hydrogenated derivatives was found to be syndiotactic. Complex OsHCl(CO)(PiPr3)2 is also active in tandem ROMP–hydrogenation of norbornene and 2,5-norbornadiene. At 40 °C and 3 atm of H2, poly(norbornene) is fully hydrogenated in 48 h, while poly(norbornadiene) is fully hydrogenated in 48 h at 75 °C and 3 atm of H2. The complex RuHCl(CO)(PiPr3)2 is also active in ROMP and tandem ROMP–hydrogenation of norbornene, obtaining trans-poly(norbornene) and hydrogenated poly(norbornene), respectively.

Double C−H Activation on Osmium and Ruthenium Centers: Carbene vs Olefin Products

Cyclometalation of bis(di-tert-butylphosphino)pentane (DtBPP) and subsequent product dehydrogenation take place in reactions of DtBPP with [OsCl6]2- and [RuCl2(p-cymene)]2 to give the M(IV) dihydrides, MH2Cl[CH(C2H4PBut2)2], and the (alkylidene)osmium and (olefin)ruthenium complexes OsHCl[C(C2H4PBut2)2] and RuHCl[But2PCH2CH2((E)-CHCH)CH2PBut2].

Alkyne-Coupling Reactions Catalyzed by OsHCl(CO)(PiPr3)2 in the Presence of Diethylamine

Complex OsHCl(CO)(PiPr3)2, in the presence of diethylamine, catalyzes the dimerization of terminal alkynes HC⋮CR (R = Me3C, Cy, Ph, and Me3Si). The reactions initially give butatrienes RCHCCCHR, which are stable under the reaction conditions for R = Me3C and Cy. For R = Ph, the butatrienes polymerize to −[CH(Ph)C⋮CCH(Ph)]n−, while for R = Me3Si, the butatriene isomerizes into the enyne Z−Me3SiCHCH−C⋮CSiMe3. The formation of butatrienes takes place via butenynyl intermediates of the type Os(C⋮CR){η3-C(C⋮CR)CHR}(CO)(PiPr3)2.

Selectivity of the OsHCl(CO)(O2)(PCy3)2 catalyzed hydrogenation of nitrile-butadiene rubber

A new homogeneous catalyst precursor has been discovered for the hydrogenation of carbon-carbon unsaturation resident within acrylonitrile-butadiene copolymers. The hydrido-phosphine complex OsHCl(CO)(O 2 )(PCy 3 ) 2 (1) selectively and quantitatively saturates olefin, leaving the copolymer's nitrile functionality intact. However, the process suffers from an undesirable crosslinking reaction that is not demonstrated by the established rhodium technology. The extent of this crosslinking is dependent on the process conditions and can be minimized by operating with a low catalyst concentration and high H 2 pressure. Kinetic studies have identified a previously unknown unexpected influence of olefin on the polymer crosslinking process. In light of this new information, the prevailing mechanism for this class of reactions has been reconsidered.

Ligand exchange processes of OsHCl(CO)(L)(PR 3) 2 (L=vacant, H 2, R′CN, O 2; R=Cy, i-Pr)

The reactivity of complexes formed by the addition of O 2, H 2 and R′CN to OsHCl(CO)(PR 3) 2 ( 1a:R=Cy; 1b:R= i-Pr) has been examined. Under 24 bar H 2 and 65°C, the dioxygen ligand of OsHCl(CO)(O 2)(PR 3) 2 ( 2a, b) is displaced to yield the trans-hydridodihydrogen complexes OsHCl( η 2-H 2)(CO)(PR 3) 2 ( 3a, b). Measurements of the equilibrium constant, K H 2 =[ 3a]/[ 1a][H 2], for the direct addition of H 2 to 1a yield Δ H°=−49.1±2.4 kJ/mol and Δ S°=−95.7±7.9 J/mol K. 1a, b react reversibly with aryl and alkyl nitriles to produce the isolable complexes, OsHCl(CO)(R′CN)(PR 3) 2 ( 4a, b). The phosphine ligands of 1a, b and 3a, b exchange with unbound, bulky alkyl phosphines at a rate that is slow relative to the NMR timescale. In the presence of excess PCy 3, complex 3b yields the exchange products OsHCl( η 2-H 2)(CO)(P i-Pr 3)(PCy 3) and 3a. While a tris-phosphine complex cannot be detected, limited kinetic data characterize the exchange as associative process.

A series of triisopropylstibine ruthenium and osmium complexes including the X-ray crystal structure of [RuCl 2(CO)(Sb iPr 3) 3] and [RuCl 2(CCCPh 2)(CO)(Sb iPr 3) 2

With [( p-cym)RuCl 2] 2 ( 1) as the starting material, the halfsandwich-type complexes [( p-cym)RuCl 2(Sb iPr 3)] ( 2) and [( p-cym)RuCl(Sb iPr 3) 2]PF 6 ( 3) were prepared. Treatment of RuCl 3·3H 2O in ethanol gave, after addition of Sb iPr 3, the monocarbonyl compound [RuCl 2(CO)(Sb iPr 3) 3] ( 4), which reacted with CO by ligand exchange to yield [RuCl 2(CO) 2(Sb iPr 3) 2] ( 5). The reaction of RuCl 3·3H 2O in ethanol, in the presence of Na 2CO 3, afforded the chloro(hydrido) derivative [RuHCl(CO)(Sb iPr 3) 3] ( 6). Analogously, using OsCl 3·3H 2O as the starting material, the chloro(hydrido)osmium complex [OsHCl(CO)(Sb iPr 3) 3] ( 8) was prepared. The reactions of 8 with C 2H 4, C 2(CO 2Me) 2 and NaBH 4 led to the formation of compounds 9, 10 and 11, which all contain the Os(Sb iPr 3) 2 unit as a building block. While treatment of 6 with C 2(CO 2Me) 2 yielded the substitution product [RuHCl(CO)(MeO 2CCCCO 2Me)(Sb iPr 3) 2] ( 14), the corresponding reaction of 6 with HCCPh and HCCCPh 2OH afforded the alkynyl and allenylidene ruthenium(II) complexes [RuCl(CCPh)(CO)(Sb iPr 3) 3] ( 16) and [RuCl 2(CCCPh 2)(CO)(Sb iPr 3) 2] ( 17), respectively. Compounds 4 and 17 were characterized by X-ray crystal structure analysis.

Synthesis and Reactivity of the Unusual Five-Coordinate Hydrido−Hydroxo Complex OsH(OH)(CO)(PiPr3)2

The five-coordinate complex OsHCl(CO)(PiPr3)2 (1) reacts with KOH in methanol to give the hydroxo derivative OsH(OH)(CO)(PiPr3)2 (2). Treatment of 2 with 1 equiv of dimethyl acetylenedicarboxylate which is the result of the trans addition of the OH bond of 2 to the carbon−carbon triple bond of the alkyne. The structure of 3 was determined by an X-ray investigation. The geometry of the complex can be rationalized as a distorted octahedron with the two phosphorus atoms of the triisopropylphosphine ligands occupying apical positions. The equatorial plane is formed by the hydride, the carbonyl group, and the κ2-O-donor ligand, which has a bite angle of 84.17(7)°. Complex 2 also reacts with methyl acrylate, methyl vinyl ketone, and allyl alcohol. Reaction with methyl acrylate leads to OsH(OH)(CO)(η2-CH2CHCO2CH3)(PiPr3)2 (4). The structure of 4 was also determined by an X-ray investigation. The coordination geometry around the osmium atom can be rationalized as derived from a highly distorted octahedron with th...

New Cyclopentadienylosmium Derivatives Prepared from the Five-Coordinate Complex [OsHCl(CO)(PPri3)2

New Cyclopentadienylosmium Derivatives Prepared from the Five-Coordinate Complex [OsHCl(CO)(PPrⁱ₃)₂

Synthesis of new hydride-carbyne and hydride-vinylcarbyne complexes of osmium(II) by reaction of OsH2Cl2(P-iso-Pr3)2 with terminal alkynes

The dihydride-dichloro complex OsH 2 Cl 2 (P-i-Pr 3 ), (1) reacts with phenylacetylene, cyclohexylacetylene, and 1-(trimethylsilyl)-1,4-pentadiyne, in hexane at 60 o C, to give the hydride-carbyne complexes OsHCl 2 (CCH 2 R)-(P-i-Pr 3 ) 2 (R=Ph (2), Cy (3), CH 2 C≡SiMe 3 (4)). The molecular structure of complex 2 was determined by X-ray crystallography. Crystals of 2 are orthorhombic, space group P2 1 2 1 2 1 , 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≥5;0σ(F)) reflections; R=0.022 and R w =0.023

Hydrogenation of benzylideneacetone catalyzed by OsHCl(CO)(PR3)2 (PR3 = P-iso-Pr3, PMe-tert-Bu2): new roles of dihydrogen complexes in homogeneous catalytic hydrogenation

The five-coordinated hydrido carbonyl complexes OsHCl(CO)(PR{sub 3}){sub 2} (PR{sub 3} = P-i-Pr{sub 3} (1), PMe-t-Bu{sub 2} (12)) catalyze selective hydrogenation of benzylideneacetone to 4-phenylbutan-2-one. In 2-propanol solutions, selectives close to 100% are achieved. In the presence of 1, the reaction is first-order with respect to the concentrations of catalyst and substrate and independent of the hydrogen pressure. For the reaction catalyzed by 12, the kinetic experimental data are in accordance with an expression of the form-d[benzylideneacetone]/dt = k[12]{sup 2}[benzylideneacetone](P(H{sub 2})). The mechanisms deduced for these reactions, on the basis of the rate laws and spectroscopic observations, illustrate new roles of the dihydrogen complexes in homogenous catalytic hydrogeneation. 1, initially nonactive, is activated as a result of the formation of trans(hydride, dihydrogen)-OsHCl({eta}{sup 2}) (CO)(P-i-Pr{sub 3}){sub 2} (6), which isomerizes to cis(hydride,dihydrogen)-OsHCl({eta}{sup 2}-H{sub 2})(CO)(P-i-Pr{sub 3}){sub 2} (14) and subsequently dissociates molecular hydrogen. The reaction catalyzed by 12 is proposed to go by the intermediate trans-[OsCl(CO)(PMe-t-Bu{sub 2}){sub 2}]{sub 2}H{sub 4} (18), which could be formed by reaction of 12 with cis(hydride,dihydrogen)-OsHCl({eta}{sup 2}-H{sub 2})(CO)(PMe-t-Bu{sub 2}){sub 2} (20). According to the theoretical works of Burdett and Pourian, this binuclear intermediate could contain a planar 4-gon of cyclically bound hydrogen atoms. 38 refs., 7 figs., 2more » tabs.« less

A new hydridocarbonyl complex of osmium(II)

The reactions of K2OsCl6 with tricyclohexyl-phosphine in alcohols leads to the hydridocarbonyl complex OsHCl(CO)(PCy3)2.