Synthesis and characterization of triosmium and triruthenium pyrene clusters

The reaction between 1-pyrenecarboxaldehyde (C₁₆H₉CHO) and the labile triosmium cluster [Os₃(CO)₁₀(CH₃CN)₂] gives rise to the formation of two new compounds by competitive oxidative addition between the aldehydic group and an arene C-H bond, to afford the acyl complex [Os₃(CO)₁₀(μ-H)(μ-COC₁₆H₉)] (1) and the compound [Os₃(CO)₁₀(μ-H) (C₁₆H₈CHO)] (2), respectively. Thermolysis of [Os₃(CO)₁₀(μ-H)(μ-C₁₆H₉CO)] (1) in n-octane affords two new complexes in good yields, [Os₃(CO)₉(μ-H)₂(μ-COC₁₆H₈)] (3) and the pyryne complex [Os₃(CO)₉(μ-H)₂(μ₃-η¹:η¹:η²-C₁₆H₈)] (4).In contrast, when 1-pyrenecarboxaldehyde reacts with [Ru₃(CO)₁₂] only one product is obtained, [Ru₃(CO)₉(μ-H)₂(μ₃-η¹:η¹:η²-C₁₆H₈)] (5), a nonacarbonyl cluster bearing a pyrene ligand. All compounds were characterized by analytical and spectroscopic data, and crystal structures for 1, 2, 4 and 5 were obtained.     

Two isomeric products [Os3(μ-H)(C14H9N4)(CO)9] formed by orthometallation of the cluster [Os3(C14H10N4)(CO)10] containing the chelating ligand 2,3-bis(2-pyridyl)pyrazine

Treatment of the labile compound [Os₃(CO)₁₀(CH₃CN)₂] with 2,3-bis(2-pyridyl)pyrazine (C₁₄H₁₀N₄) in dichloromethane at room temperature gave the cluster [Os₃(C₁₄H₁₀N₄)(CO)₁₀] (1), which contains the chelating ligand co-ordinated axially through one of the pyridine rings and equatorially through a pyrazine nitrogen atom while one of the pyridine rings remains unco-ordinated. Thermolysis of 1 leads to loss of CO and yields two structural isomers of [Os₃(μ-H)(μ,η³-C₁₄H₉N₄)(CO)₉] (2) and (3). Isomer 2 contains an orthometallated 2-pyridyl group and a co-ordinated 2-pyridyl which is not orthometallated. A seven-membered chelate ring is formed and the pyrazine ring is uncoordinated. On the other hand, isomer 3 contains a 2-pyridyl-1,4-pyrazine fragment metallated in the pyrazine ring to form a five-membered chelate ring with the one pyridine ring remaining unco-ordinated. The molecular structures of 1-3 were confirmed by X-ray crystallographic studies.     

Reactivity of [Os3(CO)10(NCMe)2] and [Os3(CO)10(μ-Cl)(μ-AuPPh3)] with 4-mercaptopyridine: X-ray structure of [Os3(CO)10(μ-H)(μ-SC5H4N)] and [Os3(CO)10(μ-AuPPh3)(μ-SC5H4N)]

The compound [Os₃(CO)₁₀(μ-Cl)(μ-AuPPh₃)] (2) was prepared from the reaction between [Os₃(CO)₁₀(NCMe)₂] (1) and [AuClPPh₃] under mild conditions. The reaction of 2 with 4-mercaptopyridine (4-pyS) ligand yielded compounds [Os₃(CO)₁₀(μ-H)(μ-SC₅H₄N)] (4), formed by isolobal replacement of the fragment [AuPPh₃]⁺ by H⁺ and [Os₃(CO)₁₀(μ-AuPPh₃)(μ-SC₅H₄N)] (5). [Os₃(CO)₁₀(μ-H)(μ-SC₅H₄N)] (4) was also obtained by substitution of two acetonitrile ligands in the activated cluster 1 by 4-pyS, at room temperature in dichloromethane. Compounds 2-5 were characterized spectroscopically and the molecular structures of 4 and 5 in the solid state were obtained by single crystal X-ray diffraction studies.     

Two modes of C-H bond activation of tris(2-thienyl)phosphine in trinuclear osmium carbonyl clusters

Tris(2-thienyl)phosphine, P(C₄H₃S)₃, reacts with [Os₃(CO)₁₂] at 110 °C to give the phosphine-substituted derivatives [Os₃(CO)₁₁{P(C₄H₃S)₃}] (1), [Os₃(CO)₁₀{P(C₄H₃S)₃}₂] (2) and [Os₃(CO)₉{P(C₄H₃S)₃}₃] (4), as well as the C-H activated product [Os₃(μ-H)(CO)₉{μ-P(C₄H₂S)(C₄H₃S)₂}{P(C₄H₃S)₃}] (3), in which the bridging ligand is equatorially coordinated to two osmium atoms. Thermolysis of 2 in refluxing toluene results in the formation of 3. Compound 1 can also be prepared in high yield from [Os₃(CO)₁₁(NCMe)]. The reaction of [Os₃(μ-H)₂(CO)₁₀] with tris(2-thienyl)phosphine at room temperature afforded [Os₃(μ-H)₂(CO)₉{P(C₄H₃S)₃}] (5) and [Os₃H(μ-H)(CO)₁₀{P(C₄H₃S)₃}] (6), with the ligand coordinated through the phosphorus atom whereas at elevated temperature the cyclometallated compounds [Os₃(μ-H)(CO)₉{μ₃-P(C₄H₂S)(C₄H₃S)₂}] (7) and [Os₃(μ-H)(CO)₈{μ₃-P(C₄H₂S)(C₄H₃S)₂{P(C₄H₃S)₃}] (8) were obtained in addition to 5. Heating 6 in refluxing heptane furnished 5 via loss of one carbonyl ligand. Thermolysis of 1 and 3 in refluxing toluene gives 7 and 8, respectively, in good yields. In 3, the μ-P(C₄H₂S)(C₄H₃S)₂ ligand is coordinated through the phosphorus to one Os atom and through a σ-Os-C bond to the second osmium atom. Compound 7 contains the μ₃-P(C₄H₂S)(C₄H₃S)₂ ligand bound through phosphorus to one Os atom, through a σ-Os-C bond to another and by an η² (π)-interaction to the third osmium atom. Compounds 1, 2 and 4 contain the ligand coordinated exclusively through the phosphorus atom. The crystal and molecular structures of 2, 3, 5, 6 and 7 are reported.     

Complexation and metallation of Ph2PCC(CH2)5CCPh2 in triosmium carbonyl clusters

Reaction of Ph₂PCC(CH₂)₅CCPh₂ with Os₃(CO)₁₀(NCMe)₂ affords Os₃(CO)₁₀(μ,η²-(Ph₂P)₂C₉H₁₀) (1) and the double cluster [Os₃(CO)₁₀]₂(μ,η²- (Ph₂P)₂C₉H₁₀)₂ (2), through coordination of the phosphine groups. Thermolysis of 1 in toluene generates Os₃(CO)₇(μ-PPh₂)(μ₃,η⁵-Ph₂PC₉H₁₀) (3) and Os₃(CO)₈(μ-PPh₂)(μ₃,η⁶-Ph₂P(C₉H₁₀)CO) (4). The molecular structures of 1, 3, and 4 have been determined by an X-ray diffraction study. Both 3 and 4 contain a bridging phosphido group and a carbocycle connected to an osmacyclopentadienyl ring, which are apparently derived from C-P bond activation and C-C bond rearrangement of the dpndy ligand governed by the triosmium clusters.     

The activation and transformations of acenaphthylene by osmium carbonyl cluster complexes

The reaction of Os₃(CO)₁₀(NCMe)₂ (1) with an excess of acenaphthylene at room temperature provided the complex Os₃(CO)₁₀(μ-H)(μ-η²-C₁₂H₇) (2). Compound 2 contains a σ-π coordinated acenaphthyl ligand bridging an edge of the cluster. Compound 2 was converted to the complex Os₃(CO)₉(μ-H)₂(μ₃-η²-C₁₂H₆) (3) when heated to reflux in a cyclohexane solution. Compound 3 contains a triply bridging acenaphthyne ligand. Compound 3 reacts with acenaphthylene again at 160 °C to yield four new cluster complexes: Os₄(CO)₁₂(μ₄-η²:η²-C₁₂H₆) (4); Os₂(CO)₆(μ-η⁴-C₂₄H₁₂) (5); Os₃(CO)₉(μ-H)(μ₃-η⁴-C₂₄H₁₃) (6); and Os₂(CO)₅(μ-η⁴-C₂₄H₁₂)(η²-C₁₂H₈) (7). All compounds were characterized crystallographically. Compound 4 is a butterfly cluster of four osmium atoms bridged by a single acenaphthyne ligand. Compounds 5 and 7 are dinuclear osmium clusters containing metallacycles formed by the coupling of two equivalents of acenaphthyne. Compound 6 is a triosmium cluster formed by the coupling of an acenaphthyne ligand to an acenapthyl group that is coordinated to the cluster through a combination of σ and π-bonding.     

Synthesis of new heterometallic complexes by tin-sulfur bond cleavage of pySSnPh3 (pySH = pyridine-2-thiol) at triruthenium and triosmium centres

The ruthenium-tin complex, [Ru₂(CO)₄(SnPh₃)₂(μ-pyS)₂] (1), the main product of the oxidative-addition of pySSnPh₃ to Ru₃(CO)₁₂ in refluxing benzene, is [Ru(CO)₂(pyS)(SnPh₃)] synthon. It reacts with PPh₃ to give [Ru(CO)₂(SnPh₃)(PPh₃)(κ²-pyS)] (2) and further with Ru₃(CO)₁₂ or [Os₃(CO)₁₀(NCMe)₂] to afford the butterfly clusters [MRu₃(CO)₁₂(SnPh₃)(μ₃-pyS)] (3, M=Ru; 4, M=Os). Direct addition of pySSnPh₃ to [Os₃(CO)₁₀(NCMe)₂] at 70 °C gives [Os₃(CO)₉(SnPh₃)(μ₃-pyS)] (5) as the only bimetallic compound, while with unsaturated [Os₃(CO)₈{μ₃-PPh₂CH₂P(Ph)C₆H₄}(μ-H)] the previously reported [Os₃(CO)₈(μ-pyS)(μ-H)(μ-dppm)] (6) and the new bimetallic cluster [Os₃(CO)₇(SnPh₃){μ-Ph₂PCH₂P(Ph)C₆H₄}(μ-pyS)[(μ-H)] (7) are formed at 110 °C. Compounds 1, 2, 4, 5 and 7 have been characterized by X-ray diffraction studies.     

Reactions of 1,8-bis(diphenylphosphino)naphthalene with Os3(CO)12: C-H and C-P bond cleavage reactions

Reactions of Os₃(CO)₁₂ with 1,8-bis(diphenylphosphino)naphthalene (dppn) are described. Crystallographically characterised complexes isolated from a reaction carried out in refluxing toluene are Os₃(μ-H)₂{μ-PPh₂(nap)PPh(C₆H₄)}₂(CO)₆ (1), Os₃(μ-H){μ₃-PPh₂(nap)PPh(C₆H₄)}(CO)₈ (2) and Os₂(μ-PPh₂){μ-PPh₂(nap)}(CO)₅ (3) (nap=1,8-C₁₀H₆), while at r.t. in the presence of ONMe₃, only Os₃(CO)₁₁{PPh₂(1-C₁₀H₇)} (4) was isolated. While 1 and 2 contain ligands formed by metallation of a Ph group of dppn, as found also in complexes obtained from dppn and Ru₃(CO)₁₂, ligands in 3 and 4 are formed by cleavage of a P-nap bond, not found in the Ru series.     

Complexation and C-H bond activation of 1,5-cyclooctadiene on triosmium carbonyl clusters

Reaction of Os₃(CO)₁₀(NCMe)₂ and 1,5-cyclooctadiene (C₈H₁₂) affords the diene complex Os₃(CO)₁₀(η⁴-C₈H₁₂) (1) with the two alkene moieties coordinated to an equatorial and an axial positions of one osmium atom. Thermolysis of 1 in refluxing n-hexane results in a vinylic C-H bond activation to form (μ-H)Os₃(CO)₉(μ,η⁴-C₈H₁₁) (2) in good isolated yield. The crystal structures of 1 and 2 have been established by an X-ray diffraction study.     

Reaction of tri(2-furyl)phosphine with triosmium clusters: C-H and P-C activation to afford furyne and phosphinidene ligands

Addition of tri(2-furyl)phosphine, PFu₃, to [Os₃(CO)₁₀(μ-H)₂] at room temperature gives [HOs₃(CO)₁₀(PFu₃)(μ-H)] (1), while in refluxing toluene the same reactants afford [Os₃(CO)₉{μ₃-PFu₂(C₄H₂O)}(μ-H)] (2) resulting from orthometallatation of a furyl ring. Reaction of PFu₃ with [Os₃(CO)_10−n(NCMe)_n] (n = 0, 1, 2) affords the substituted clusters [Os₃(CO)_12−n(PFu₃)_n] (n = 1-3) (3-5), the phosphine ligands occupying equatorial position in all cases. Heating [Os₃(CO)₁₁(PFu₃)] (3) in refluxing octane gives [Os₃(CO)₉(μ₃-PFu)(μ₃-η²-C₄H₂O)] (6) which results from both carbon-hydrogen and carbon-phosphorus bond activation and contains both μ₃-η²-furyne and furylphosphinidene ligands. All new clusters have been characterized by spectroscopic methods together with single crystal X-ray diffraction for 2, 3 and 6.     

Activation of 1,3,5-trimethyl-1,3,5-triazacyclohexane by Os3(CO)12 to form amidino [(MeN)2CH] cluster complexes

Reaction of 1,3,5-trimethyl-1,3,5-triazacyclohexane [(MeNCH₂)₃] with Os₃(CO)₁₂ in refluxing toluene results in C-H and C-N bond activation of the (MeNCH₂)₃ ligand to afford three amidino cluster complexes (μ-H)Os₃(CO)₁₀[μ,η²-CH(NMe)₂] (1), (μ-H)Os₃(CO)₉[μ₃,η²-CH(NMe)₂] (2), and Os₂(CO)₆[μ,η²-CH(NMe)₂]₂ (3). The controlled experiments show that thermolysis of 1 yields 2, and heating 2 in the presence of (MeNCH₂)₃ ligand produces 3. The molecular structures of 1 and 3 have been determined by an X-ray diffraction study.     

Synthesis and structural characterization of mesitylphosphinidene-capped ruthenium and osmium clusters

Thermal reaction of [Ru₃(CO)₁₂] with PH₂Mes (Mes = mesityl) in refluxing toluene afforded mesitylphosphinidene-capped ruthenium carbonyl clusters, [Ru₃(CO)₉(μ-H)₂(μ₃-PMes)] (1), [Ru₃(CO)₈(PH₂Mes)(μ-H)₂(μ₃-PMes)] (2), [Ru₃(CO)₉(μ₃-PMes)₂] (3), [Ru₄(CO)₁₀(μ-CO)(μ₄-PMes)₂] (4), and [Ru₅(CO)₁₀H₂(μ₄-PMes)(μ₃-PMes)₂] (5). All products were fully characterized and structurally confirmed by X-ray crystal structure analysis. Complexes 2-4 were also obtained in high yields by stepwise reaction starting from 1. Fluxional behavior of carbonyl groups was observed in case of 4. Complex 5 reveals a new type of skeletal structure, bicapped-octahedron having μ₃- and μ₄-phosphinidene ligands at the capping positions. Similar reaction of [Os₃(CO)₁₂] with PH₂Mes yielded a phosphido-bridged osmium cluster [Os₃(CO)₁₀(μ-H)(μ-PHMes)] (6) and a phosphinidene-capped cluster [Os₃(CO)₉(μ-H)₂(μ₃-PMes)] (7).     

A comparative study of the reactivity of unsaturated triosmium clusters [Os3(CO)8{μ3-Ph2PCH2P(Ph)C6H4}(μ-H)] and [Os3(CO)9{μ3-η-C7H3(2-Me)NS}(μ-H)] with BuNC

Treatment of unsaturated [Os₃(CO)₈{μ₃-Ph₂PCH₂P(Ph)C₆H₄}(μ-H)] (2) with ^tBuNC at room temperature gives [Os₃(CO)₈(CNBu^t)){μ₃-Ph₂PCH₂P(Ph)C₆H₄}(μ-H)] (3) which on thermolysis in refluxing toluene furnishes [Os₃(CO)₇(CNBu^t){μ₃-Ph₂PCHP(Ph)C₆H₄}(μ-H)₂] (4). Reaction of the labile complex [Os₃(CO)₉(μ-dppm)(NCMe)] (5) with ^tBuNC at room temperature affords the substitution product [Os₃(CO)₉(μ-dppm)(CNBu^t)] (6). Thermolysis of 6 in refluxing toluene gives 4. On the other hand, the reaction of unsaturated [Os₃(CO)₉{μ₃-η²-C₇H₃(2-Me)NS}(μ-H)] (7) with ^tBuNC yields the addition product [Os₃(CO)₉(CNBu^t){μ-η²-C₇H₃(2-Me)NS}(μ-H)] (8) which on decarbonylation in refluxing toluene gives unsaturated [Os₃(CO)₈(CNBu^t){μ₃-η²-C₇H₃(2-Me)NS}(μ-H)] (9). Compound 9 reacts with PPh₃ at room temperature to give the adduct [Os₃(CO)₈(PPh₃)(CNBu^t){μ-η²-C₇H₃(2-Me)NS(μ-H)] (10). Compound 8 exists as two isomers in solution whereas 10 occurs in four isomeric forms. The molecular structures of 3, 6, 8, and 10 have been determined by X-ray diffraction studies.     

Reactions of the triosmium cluster Os3(μ-H)(μ-OH)(CO)10 with naphthols

Reaction of the cluster Os₃(μ-H)(μ-OH)(CO)₁₀ (1) with 1-naphthol afforded the isomeric clusters 2a and 3a with the formulae Os₃(μ-H)₂(μ₃-1-OC₁₀H₆)(CO)₉. A similar reaction with 2-naphthol, however, gave Os₃(μ-H)(μ-2-OC₁₀H₇)(CO)₁₀, 4b, and the analogue of 2a. These clusters have been structurally characterised to confirm the mode of anchoring of the naphthols.     

Reactions of benzothiazolide triosmium clusters with tetramethylthiourea

The valence saturated benzothiazolide triosmium cluster [Os₃(CO)₁₀(μ-η²-C₇H₄NS)(μ-H)] (1) reacts with tetramethylthiourea in refluxing toluene to give [Os₃(CO)₈(μ-η²-C₇H₄NS)(η²-SCNMe₂NMeCH₂)(μ-H)₂] (5), which exists as a mixture of two isomers in solution, whereas the electron-deficient cluster [Os₃(CO)₉(μ₃-η²-C₇H₄NS)(μ-H)] (2) reacts with tetramethylthiourea in refluxing cyclohexane to give two new compounds [Os₃(CO)₈(μ-η²-C₇H₄NS)(η²-SCNMe₂NMeCH₂)(μ-H)₂] (6) and [Os₃(CO)₉(μ-η²-C₇H₄NS)(η¹-SC(NMe₂)₂)(μ-H)] (7). In contrast, the reaction of [Os₃(CO)₉(μ₃-η²-C₇H₃(2-CH₃)NS)(μ-H)](3) with tetramethylthiourea in refluxing cyclohexane at 81 °C, gives only [Os₃(CO)₉(μ-η²-C₇H₃(2-CH₃)NS)(η¹-SC(NMe₂)₂)(μ-H)] (8) in 15% yield. Compound 7 converts into 6 in refluxing toluene whereas a similar thermolysis of 8 results non-specific decomposition. All the compounds have been characterized by elemental analysis, IR, ¹H NMR and mass spectroscopic data together with single crystal X-ray diffraction analysis for 5 and 7. Both compounds 5 and 6 contain a cyclometallated tetramethylthiourea ligand which is chelating at the rear osmium atom and are structurally very similar. In 5, the benzothiazolide ligand is coordinated to Os₃ triangle via the nitrogen lone pair and C(2) carbon atom of the heterocyclic ring whereas in 6 the ligand is coordinated to the Os₃ triangle via the nitrogen lone pair and the C(7) carbon atom of carbocyclic ring. In 7 and 8, the tetramethylthiourea ligand is coordinated at an equatorial site of the osmium atom which is also bound to the nitrogen atom of the benzothiazolide ligand.     

Reaction of the heterometallic cluster Os3Ru(μ-H)2(CO)13 with diphenylphosphine: phosphido-bridged tetrahedral and butterfly clusters

TMNO-activated reaction of the heteronuclear cluster Os₃Ru(μ-H)₂(CO)₁₃ (1) with diphenylphosphine afforded the novel phosphido-bridged clusters Os₃Ru(μ-PPh₂)(μ-H)₃(CO)₁₁ (2), Os₃Ru(μ-PPh₂)₂(μ-H)₂(CO)₁₀ (3), Os₃Ru(μ-PPh₂)₂(μ-H)₄(CO)₉ (4), and Os₃Ru(μ-PPh₂)(μ-H)₃(CO)₁₁(PPh₂H) (5). The formation of 2-5 proceeded via P-H bond cleavage in the adduct Os₃Ru(μ-H)₂(CO)₁₂(PPh₂H) (6). Reaction of 2 with PPh₃ afforded the adduct Os₃Ru(μ-PPh₂)(μ-H)₃(CO)₁₁(PPh₃) (7) and the substituted derivative Os₃Ru(μ-PPh₂)(μ-H)₃(CO)₁₀(PPh₃) (8).     

Reactions of linked tetrahedron clusters [Co2(CO)6(μ-HC2CH2O)-]2R with Rh2(CO)4Cl2 to give mixed-metal linked alkyne-bridged butterfly clusters containing C2Co2Rh2 unit

The reactions of compound Rh₂(CO)₄Cl₂, 1 with [Co₂(CO)₆(μ-HC₂CH₂O)-]₂R (R = C₆H₄, 2; (COCH₂)₂, 3; C₆H₄-1,4-(CO)₂, 4; (COCH)₂, 5; (CO)₂, 6) in benzene at 60 °C produce five new mixed-metal linked clusters Rh₂Co₂(CO)₁₀(μ₄,η²-HC₂CH₂O-R-OCH₂C₂H-μ)Co₂(CO)₆ (R = C₆H₄, 7a; (COCH₂)₂, 7b; C₆H₄-1,4-(CO)₂, 7c; (COCH)₂, 7d; (CO)₂, 7e) and five known linked octahedral clusters [Rh₂Co₂(CO)₁₀(μ₄,η²-HC₂CH₂O-)]₂R (R = C₆H₄, 8a; (COCH₂)₂, 8b; C₆H₄-1,4-(CO)₂, 8c; (COCH)₂, 8d; (CO)₂, 8e), respectively. Treatment of clusters 7a-8e in benzene at room temperature under air for 24 h with stirring afford the precursor clusters 2-6, respectively. The structure of cluster 7a has been determined by single-crystal X-ray diffraction. The linked cluster 7apossesses two isomers A and B in its structures, the Rh₂(CO)₄ unit inserts into one of two Co-Co bonds and coordinates to the Co₂C₂ core forming one distorted closo-Rh₂Co₂C₂ octahedron framework which is connected to the Co₂C₂ tetrahedron unit via C₆H₄(OCH₂)₂-1,4 as a bridging ligand. All clusters were characterized by C, H elemental analysis, IR and ¹H NMR spectroscopy.     

Hexa- and triosmium carbonyl clusters bearing bridging dppm and capping sulfido ligands

Treatment of [Os₃(CO)₇(μ₃-S)₂(μ-dppm)] (1) with Me₃NO in toluene at 80 °C affords the trinuclear cluster [Os₃(CO)₆(μ₃-S)₂(NMe₃)(μ-dppm)] (2) and the hexanuclear cluster [Os₆(CO)₁₂(μ₃-S)₄(μ-dppm)₂] (3) in 30% and 51% yields, respectively. The reaction of 1 with [Os₃(CO)₁₀(MeCN)₂] in refluxing benzene at 80 °C gives the hexanuclear cluster [Os₆(CO)₁₄(μ₃-S)₂(μ-dppm)] (4) in 15% yield. Compound 2 reacts with CO, PPh₃ and P(OMe)₃ at room temperature to give 1, [Os₃(CO)₆(μ₃-S)₂(μ-dppm)(PPh₃)] (5) and [Os₃(CO)₆(μ₃-S)₂(μ-dppm){P(OMe)₃}] (6), respectively; in high yields indicating that the NMe₃ ligand is weakly bound. Compound 1 reacts with PPh₃ in presence of Me₃NO to afford 5, 2 and 3 in 53%, 6% and 18% yields, respectively, whereas with P(OMe)₃1 gives only 6 in 84% yield. Compound 3 reacts with CO at 98 °C to regenerate 1 by the cleavage of the three unsupported osmium-osmium bonds. The molecular structures of 4 and 6 have been unambiguously determined by single crystal X-ray diffraction studies. The hexanuclear compound 3 appears to be a64-electron butterfly core with four triply bridging sulfido ligands and two bridging dppm ligands based on the spectroscopic and analytical data. The metal core of 4 can be described as a central tetrahedral array capped on two faces with two additional osmium atoms. The triply bridging sulfido ligands face cap the two tetrahedral arrays formed by metal capping of the two faces of the central tetrahedron. The dppm ligand bridges one edge of one of the external tetrahedral arrays. Compounds 5 and 6 are formed by the displacement of equatorial carbonyl group of 1 by a PPh₃ and P(OMe)₃ ligand respectively and their structures are comparable to that of 1.     

Synthesis and diphosphine ligand fluxionality in Os3(CO)10(bmi): Kinetic evidence for nondissociative diphosphine isomerization and X-ray crystal structure of 1,1-Os3(CO)10(bmi)

The triosmium cluster 1,2-Os₃(CO)₁₀(MeCN)₂ reacts rapidly with the diphosphine ligand 2,3-bis(diphenylphosphino)-N-p-tolylmaleimide (bmi) at room temperature to give bmi-bridged cluster 1,2-Os₃(CO)₁₀(bmi) (2b) as the major product, along with the chelating isomer 1,1-Os₃(CO)₁₀(bmi) (2c) and the hydride-bridged cluster HOs₃(CO)₉[μ-(PPh₂)CC{PPh(C₆H₄)}C(O)N(tolyl-p)C(O)] (3) as minor by-products. All three cluster compounds have been isolated and fully characterized in solution by IR and NMR spectroscopies (¹H and ³¹P), and X-ray crystallography in the case of 2c. Cluster 2b is unstable and readily isomerizes to 2c in quantitative yield on mild heating. The kinetics for the conversion of 2b → 2c have been measured over the temperature range of 318-348 K in toluene solution, and based on the observed activation parameters a nondissociative isomerization process that proceeds via a transient μ₂-bridged phosphine moiety is presented. Near-UV photolysis of cluster 2c at room temperature affords HOs₃(CO)₉[μ-(PPh₂)CC{PPh(C₆H₄)}C(O)N(tolyl-p)C(O)] (3) with a quantum yield of 0.017. The reactivity of clusters 2b, 2c, and 3 is discussed with respect to related diphosphine-substituted Os₃(CO)₁₀(P-P) clusters prepared by our groups.     

From straight chain to macrocyclic complexes containing mixed sulfur/nitrogen donors and coordinated 1,3-diynes

The acid-mediated reaction of [{Co₂(CO)₆(μ-η²-HOCH₂CC-)}₂] (1) with the meta- and para-substituted aminothiophenols, 3-NH₂-C₆H₄SH and 4-NH₂-C₆H₄SH, affords the straight chain species, [{Co₂(CO)₆(μ-η²-(3-NH₂-C₆H₄S)CH₂CC-)}₂] (2) and [{Co₂(CO)₆(μ-η²-(4-NH₂-C₆H₄S)CH₂CC-)}₂] (3), respectively. The molecular structure of 3 reveals the presence of two isomeric forms differing in the relative disposition of the S-aryl groups. Conversely, reaction of 1 with the ortho-substituted aminothiophenol, 2-NH₂-C₆H₄SH, furnishes the 10-membered macrocyclic species [{Co₂(CO)₆}₂{cyclo-μ-η²:μ-η²-CH₂C₂C₂CH₂SC₆H₃-NH-2}] (4) along with the linear chain complex [{Co₂(CO)₆(μ-η²-(2-NH₂-C₆H₄S)CH₂CC-)}₂] (5). On the other hand, treatment of 1 with the ortho-substituted mercaptopyridine, 2-SH-C₅H₄N, in the presence of HBF₄ gives the salt [{Co₂(CO)₆(μ-η²-(2-S-C₅H₄NH)CH₂CC-)}₂](BF₄)₂ (6a) in good yield; work-up in the presence of base affords the neutral complex [{Co₂(CO)₆(μ-η²-(2-S-C₅H₄N)CH₂CC-)}₂] (6b). Single crystal X-ray diffraction studies have been reported on 3-5 and 6a.