Kazi A. Azam

Electron deficient bonding of benzoheterocycles to triosmium clusters: synthesis and applications to organic chemistry

Abstract A new synthetic methodology for the addition of carbon based nucleophiles to the carbocyclic ring of quinolines has been developed which is based on the electron deficient bonding of the C(8) carbon and the protective coordination of the nitrogen atom to the metal core in the complexes [Os3(CO)9(μ3-η2-C9H5(R)N)(μ-H)] (R can be a wide range of substituents in the 3-, 4-, 5- and 6-positions of the quinoline ring). These complexes react with a wide range of carbanions (R′Li, R′=Me, nBu, tBu, Bz, Ph, CHCH2, C2(CH2)3CH3, CH2CN, (CH3)2CCN, –CHS(CH2)2S–; CH2CO2tBu, R′MgBr, R′=CH3, CH2CHCH2) to give the nucleophilic addition products [Os3(CO)9(μ3-η3-C9H7(5-R′)N)(μ-H)] (2a–2l), after quenching with trifluoracetic acid, in isolated yields of 43–86%. Substitution at the 3- or 4-position is well tolerated giving the expected nucleophilic addition products [Os3(CO)9(μ3-η3-C9H6(3 or 4-R)(5-R′)N)(μ-H). The 6-substituted derivatives give >95% of the cis-diastereomer, [(Os3(CO)9(μ3-η3-C9H6(5-R′)(6-R)N)(μ-H)]. The stereochemistry is preserved even in the case of less bulky carbanions (R′=CH3). In the case of the 6-Cl derivative, a second product is obtained on reaction with the isobutyryl carbanion, [Os3(CO)9(μ3-η2-C9H5(6-Cl)(5-C(CH3)2CN)N)(μ-H)2] (4) which is the result of protonation at the metal core and rearrangement of the carbocyclic ring. The trans-diastereomer of the addition products obtained from the 6-substituted derivatives can be synthesized by reaction of the unsubstituted complex with R′Li followed by quenching with (CH3O)2SO2. Acetic anhydride can also be used as the quenching electrophile for the intermediate anions generated from R′Li [(trans-Os3(CO)9(μ3-η3-C9H6(6-CH3CO)(5-CH3)N)(μ-H)] (5). Nucleophilic addition occurs across the 3,4-bond in the cases where the 5-position is occupied by a substituent. The nucleophilic addition products can be rearomatized by reaction with DBU/DDQ or by reaction of the intermediate anion with trityl cation or DDQ. The resulting rearomatized complexes can be cleanly cleaved from the cluster by reflux in acetonitrile under a CO atmosphere yielding the functionalized quinoline and Os3(CO)12 as the only two products. An overview of this previously reported work along with additional examples of this novel chemistry is given here as well as an extention of the synthesis of the electron deficient triosmium clusters to a wide range of heterocycles structurally related to quinoline. These complexes include those containing the heterocycles: phenanthridine (7), 5,6-benzoquinoline (8), 2-CH3-benzimidazole (9), 2-methyl benzotriazole (10), 2-methyl-benzoxazole (11), 2-R-benzothiazole (R=H, 12; CH3, 13) and quinoxaline (14). The solid state structures of 7–10, 12, and 14 are reported.

X-ray structure of [Os3(CO)10(μ-Ph2PCH2PPh2)]

Decacarbonyl-μ-bis(diphenylphosphino)methane triosmium crystallizes in the monoclinic space group P21/c with a = 24.422(5), b = 12.381(2), c = 24.788(5) Å, β = 103.69(3)°, V = 7282 (2) Å3, and Z = 8. The molecule consists of a triangular arrangement of osmium atoms with the organic ligand bridging two adjacent osmium atoms at equatorial sites. The Os—Os distances lie in the close range 2.8563(9)–2.8895(11) Å with an average value of 2.87(1) Å.

Triosmium clusters containing bridging sulphur, hydrido, and diphosphine ligands: A study of hydride site preferences and mobility

Abstract Reaction of dppm (Ph 2 PCH 2 PPh 2 ) with [OS 3 (μ-H) 2 (μ 3 -S)(CO) 9 ] in refluxing toluene leads to the cluster [Os 3 (μ-H) 2 (μ 3 -S)(CO) 7 (dppm)] ( 1 ) (34% yield), the crystal structure of which has been determined. If the reaction is carried out at higher temperatures in refluxing octane, it gives the known cluster [Os 3 (CO) 8 (μ-dppm) 2 ] (11%) in addition to 1 . Cluster 1 is protonated to give [Os 3 (μ-H) 3 (μ 3 - S)(CO) 7 (dppm)] + , isolated as its hexafluorophosphate salt. The bridging dppm compound [Os 3 (CO) 10 (dppm)] reacts with RSH (R  Ph, or 4-MeC 6 H 4 ) in refluxing toluene to give the thiolato hydrido clusters [Os 3 (μ-H)(μ-SR)(CO) 8 (dppm)], which on protonation with trifluoroacetic acid give the protonated species [Os 3 (μ-H) 2 (μ-SR)(CO) 8 (dppm)] + , isolated as their hexafluorophosphate salts. We have examined the hydride coordination sites with respect to the position of the μ-dppm ligand and the effect of the μ-dppm ligand on the mobility of hydrides in these complexes.

Triosmium clusters derived from the reactions of thioureas with dodecacarbonyltriosmium: Crystal structures of [Os3(CO)11{η1-SC(NMe2)2}], [Os3(CO)9(μ-OH)(μ-OMeOCO){η1-SC(NMe2)2}] and [(μ-H)Os3(CO)9{μ3-NHC(S)NH2}]

AbstractThe reaction of [Os3(CO)12] with tetramethylthiourea in the presence of a methanolic solution of Me3NO·2H2O at 60° yields the compounds [Os3(CO)11{η1-SC(NMe2)2}] (1) in 56% yield and [Os3(CO)9(μ-OH)(μ-MeOCO){η1-SC(NMe2)2}] (2) in 10% yield in which the tetramethylthiourea ligand is coordinatedvia the sulfur atom at an equatorial position. Compound2 is a 50 e− cluster with two metal-metal bonds and the hydroxy and methoxycarbonyl ligands bridging the open metal-metal edge. In contrast, the analogous reaction of [Os3(CO)12] with thiourea gives the compounts [(μ-H)Os3(CO)10{μ-NHC(S)NH2}] (3) in 8% yield and [(μ-H)Os3(CO)9{3-NHC(S)NH2}] (4) in 30% yield. In3, the thioureato ligand bridges two osmium atomsvia the sulfur atom, whereas in4 in addition to the sulfur bridge, one of the nitrogen atoms of thioureato moiety bonds to the remaining osmium atom. The decacarbonyl compounds 3 can also be obtained in 50% yield from the reaction of [Os3(CO)10(MeCN)2] with thiourea at ambient temperature. Compound3 converts to4 (65%) photochemically. Compound1 reacts with PPh3 and acetonitrile at ambient temperature to give the simple substitution products [Os3(CO)11(PPh3)] and [Os3(CO)11(MeCN)], respectively, while with pyridine, the oxidative addition product [(μ-H)Os3(CO)10(μ-NC5H4] is formed at 80°C. All the new compounds are characterized by IR,1-H-NMR and elemental analysis together with the X-ray crystal structures of1,2 and4. Compound1 crystallizes in the triclinic space group P

Triosmium clusters containing thiazolide ligand: crystal structures of [(μ-H)Os3(CO)10(μ-3,4-η2-H)] and [(μ-H)Os3(CO)9(μ-3,4-η2-H)(PPh3)]

P\bar 1

Synthesis and reactivity of tetramethylthioureatriosmium clusters: crystal structures of [(μ-H)Os3(CO)8(μ3-S)(μ-OMeCO){η1-SC(NMe2)2}] and [Os3(CO)9(μ-OH)(μ-OMeCO)(PPh3)]

with unit cell parametersa = 8.626(3) Å,b = 11.639(3) Å,c = 12.568(3_ Å,α = 84.67(2)°,β = 75.36(2)°,γ = 79.49(3)°,V = 1199(1) Å3, andZ = 2. Least-squares refinement of 4585 reflections gave a final agreement factor ofR = 0.0766 (Rw = 0.0823). Compound2 crystallizes in the monoclinic space group P21/n with unit cell parametersa = 9.149(5) Å,b = 17.483(5) Å,c = 15.094(4) Å,β = 91.75(2)°,V = 2413(2) Å3, andZ = 4. Least-squares refinement of 3632 reflections gave a final agreement factor ofR = 0.0603 (Rw = 0.0802). Compound4 crystallizes in the monoclinic space group C2/c with unit cell parametersa = 13.915(7) Å,b = 14.718(6) Å,c = 17.109(6) Å,β = 100.44(3)°,V = 3446(5) Å3, andZ = 8. Least-squares refinement of 2910 reflections gave a final agreement factor ofR = 0.0763 (Rw = 0.0863).

A novel pentaruthenium cluster containing three thiazole derived ligands; X-ray structure of [(Ru3(CO)9(μ-H)(μ5-η5-HCNCCHS)Ru2-(CO)4(μ-H) (η1-HC=NCH=CHS) (μ-2,3-η3-C=NCH=CHS)]

The reaction of the unsaturated cluster [(μ-H)Os3(CO)8{Ph2PCH2P(Ph)C6H4}] 2 with C2H5SH, CH3CH(CH3)SH and C6H5SH are reported. The reaction of 2 with C2H5SH yields the new complexes [Os3(CO)8(μ-SC2H5)(η1-SC2H5){Ph2PCH2P(Ph)C6H4}(μ-H)] 9 and [Os3(CO)8)(SC2H5)(Ph2PCH2P)(Ph)C6H4}] 8 in 24 and 57% yields respectively and the known compound [(Os3(CO)8)(μ-SC2H5)(μ-dppm)(μ-H)] 7 in 5% yield. Compound 9, which exists as two isomers in solution, converts into 8 almost quantitatively in solution at 25°C and more rapidly in refluxing hexane. Compound8 reacts with H2 at 110°C to give 7 in high yield (86%). Treatment of 2 with propane-2-thiol yields [Os3(CO)8{μ-SCH(CH3)CH3}{Ph2PCH2P(Ph)C6H4}] 10 and [(Os3(CO)8{μ-SCH(CH3)CH3}{η1-SCH(CH3)CH3}{Ph2PCH2P(Ph)C6H4}(μ-H)] 11 in 75 and 3% yields respectively while with C6H5SH, [(Os3(CO)8(μ-SC6H5)(μ-dppm)(μ-H)] 6 is obtained as the only product in 75% yield. In both 8 and 10, the thiolato ligand bridges the Os–Os edge which is also bridged by the metallated phenyl group. The new compounds have been characterized by elemental analyses and spectroscopic methods (IR, 1H and 31P NMR). The molecular structures of 7, 8, 9 and 10 are reported as determined by X-ray diffraction studies.

Photochemical reaction of Re2(CO)10 with tetramethylthiourea; structural characterization of two novel pentarhenium carbonyl complexes containing sulfido and tetramethyldiaminocarbene ligands, [Re5(CO)17(μ-R)(μ4-S)2{C(NMe2)2}2] (R=SH or OH)

The reaction of [Os 3 (CO) 10 (MeCN) 2 ] with thiazole at ambient temperature affords two isomeric isolable compounds [( μ -H)Os 3 (CO) 10 ( μ -2,3- η 2 - )] 2 and [( μ -H)Os 3 (CO) 10 ( μ -3,4- η 2 -H )] 3 in 20 and 60% yields, respectively. Compound 3 reacts with PPh 3 at 110°C to give [( μ -H)Os 3 (CO) 9 ( μ -3,4- η 2 -H )(PPh 3 )] 4 , which exists as two isomeric forms in solution. Reaction of 3 with trimethyl phosphite at 110°C gives the substitution product [( μ -H)Os 3 (CO) 9 ( μ -3,4- η 2 -H ){P(OMe 3 }] 5 , which is structurally analogous to 4 in solution. Similarly compound 2 reacts with PPh 3 at 110°C to afford [( μ -H)Os 3 (CO) 10 ( μ -2,3- η 2 - )(PPh 3 )] 6 , which also exists as two isomers in solution. The compounds have been characterised by IR, 1 H-NMR and elemental analysis together with single crystal X-ray analysis for 3 and 4 .