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Richard D. Adams - One of the best experts on this subject based on the ideXlab platform.

  • Activation of metal hydride complexes by tri-tert-butylphosphine-platinum and -palladium groups.
    Journal of the American Chemical Society, 2007
    Co-Authors: Richard D. Adams, Burjor Captain, Eszter Trufan
    Abstract:

    The compounds HM(CO)4SnPh3, M = Os (10), Ru (11) are activated in the presence of Pt(PBut3)2 and Pd(PBut3)2 toward the insertion of PhC2H into the M−H bond. The compounds PtOs(CO)4(SnPh3)(PBut3)[μ-HCC(H)Ph], 12, and PtOs(CO)4(SnPh3)(PBut3)[μ-H2CCPh], 13, were obtained from the reaction of 10 with PhC2H in the presence of Pt(PBut3)2. Compounds 12 and 13 are isomers containing alkenyl ligands formed by the insertion of the PhC2H molecule into the Os−H bond at both the substituted and unsubstituted carbon Atoms of the alkyne. Both compounds contain a Pt(PBut3) group that is bonded to the Osmium Atom and a bridging alkenyl ligand that is π-bonded to the Osmium Atom. The reaction of 11 with PhC2H in the presence of Pt(PBut3)2 yielded the products PtRu(CO)4(SnPh3)(PBut3)[μ-HC2(H)Ph], 14, and PtRu(CO)4(SnPh3)(PBut3)[μ-H2C2Ph], 15, which are also isomers similar to 12 and 13. The reaction of 11 with PhC2H in the presence of Pd(PBut3)2 yielded the product PdRu(CO)4(SnPh3)(PBut3)[μ-H2C2Ph], 16. Compound 16 contains...

  • Platinum promoted insertion of an alkyne into a metal-hydrogen bond.
    Journal of the American Chemical Society, 2006
    Co-Authors: Richard D. Adams, Burjor Captain
    Abstract:

    HOs(CO)4SnPh3, 1 reacts with PhC2H in the presence to Pt(PBut3)2 to yield the alkyne insertion product PtOs(CO)4(SnPh3)(PBut3)[μ-HC2(H)Ph], 2 containing a Pt(PBut3)(CO) group coordinated to the Osmium Atom and the alkenyl ligand. In the absence of PhC2H, 1 reacts with Pt(PBut3)2 to form a Pt(PBut3) adduct, PtOs(CO)4(SnPh3)(PBut3)(μ-H), 3 at the Os−H bond. This adduct is readily transformed to 2 upon reaction with PhC2H. In the absence of the Pt(PBut3) promoter, PhC2H does not react with 1.

  • Cluster Fragmentation and Facile Cleavage of Phenyl Groups from the SnPh3 Ligand in Reactions of Os3(CO)11(SnPh3)(μ-H) with CO and HSnPh3
    Organometallics, 2006
    Co-Authors: Richard D. Adams, Burjor Captain
    Abstract:

    Two new cluster complexes, Os3(CO)12(Ph)(μ3-SnPh), 8 (35% yield), and Os4(CO)16(μ4-Sn), 9 (10% yield), were formed when the complex Os3(CO)11(SnPh3)(μ-H), 6, was heated to reflux in toluene solvent under a CO atmosphere. Compound 8 was transformed to 9 in 28% yield when a solution in octane solvent was heated to reflux under a CO atmosphere. Biphenyl was a coproduct in this reaction. Compound 8 contains three Osmium Atoms with a triply bridging SnPh group. The triOsmium cluster has opened and there is only one Os−Os bond between the three Osmium Atoms. Compound 9 contains two Os2(CO)8 groups held together by a central quadruply bridging tin Atom, giving an overall bow-tie structure for the five metal Atoms. Two other new compounds, Os2(CO)6(μ-SnPh2)2(SnPh3)2, 10, and HOs(CO)4(SnPh3), 11, were formed in 51% and 20% yields, respectively, from the reaction of 6 with HSnPh3. Compound 10 contains only two Osmium Atoms linked by an Os−Os bond and two bridging SnPh2 ligands. Each Osmium Atom also contains one te...

  • The synthesis and structural characterization of Os_3(CO)_8[Si(OMe)_3][μ-PMe_2(C_6H_4](μ-H)_2: An unusual unsaturated triOsmium cluster complex
    Journal of Cluster Science, 1995
    Co-Authors: Richard D. Adams, Jeffrey E. Cortopassi
    Abstract:

    The reaction of Os_3(CO)_10(NCMe)[Si(OMe)_3](μ-H), 1 , with PMe_2Ph yielded the new complex Os_3(CO)_10(PMe_2Ph)[Si(OMe)_3](μ-H), 2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound 2 was decarbonylated and transformed into the new unsaturated cluster complex Os_3(CO)_8[μ-PMe_2(C_6H_4)][Si(OMe)_3](μ-H)_2, 3 in 54% yield. Compound 3 was characterized by a single crystal X-ray diffraction analysis, Osmium bonds. The phenyl ring of the phosphine ligand has undergone ortho -metallation by a neighboring metal Atom. A terminally coordinated Si(OMe)_3 ligand is coordinated to the third Osmium Atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted Osmium Atom that is partially filled by a weak interaction with one of the π-bonds of the ortho -metalled phenyl ring. Complex 3 reacts with CO at 1 atm to reform compound 2 in 85% yield in 5 h at 40°C. Crystal Data: for 3 : space group = P2_1/ n , a = 9.911(2) Å, b = 18.451(6) Å, c = 14.872(2) Å, β = 95.64(2)°, Z = 4, 1994 reflections, R = 0.028.

  • The synthesis and structural characterization of Os3(CO)8[Si(OMe)3][μ-PMe2(C6H4](μ-H)2: An unusual unsaturated triOsmium cluster complex
    Journal of Cluster Science, 1995
    Co-Authors: Richard D. Adams, Jeffrey E. Cortopassi
    Abstract:

    The reaction of Os3(CO)10(NCMe)[Si(OMe)3](μ-H),1, with PMe2Ph yielded the new complex Os3(CO)10(PMe2Ph)[Si(OMe)3](μ-H),2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound2 was decarbonylated and transformed into the new unsaturated cluster complex Os3(CO)8[μ-PMe2(C6H4)][Si(OMe)3](μ-H)2,3 in 54% yield. Compound3 was characterized by a single crystal X-ray diffraction analysis, Osmium bonds. The phenyl ring of the phosphine ligand has undergoneortho-metallation by a neighboring metal Atom. A terminally coordinated Si(OMe)3 ligand is coordinated to the third Osmium Atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted Osmium Atom that is partially filled by a weak interaction with one of the π-bonds of theortho-metalled phenyl ring. Complex3 reacts with CO at 1 atm to reform compound2 in 85% yield in 5 h at 40°C. Crystal Data: for3: space group = P21/n,a = 9.911(2) A,b = 18.451(6) A,c = 14.872(2) A,β = 95.64(2)°,Z = 4, 1994 reflections,R = 0.028.

Pavel V. Petrovskii - One of the best experts on this subject based on the ideXlab platform.

Jeffrey E. Cortopassi - One of the best experts on this subject based on the ideXlab platform.

  • The synthesis and structural characterization of Os_3(CO)_8[Si(OMe)_3][μ-PMe_2(C_6H_4](μ-H)_2: An unusual unsaturated triOsmium cluster complex
    Journal of Cluster Science, 1995
    Co-Authors: Richard D. Adams, Jeffrey E. Cortopassi
    Abstract:

    The reaction of Os_3(CO)_10(NCMe)[Si(OMe)_3](μ-H), 1 , with PMe_2Ph yielded the new complex Os_3(CO)_10(PMe_2Ph)[Si(OMe)_3](μ-H), 2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound 2 was decarbonylated and transformed into the new unsaturated cluster complex Os_3(CO)_8[μ-PMe_2(C_6H_4)][Si(OMe)_3](μ-H)_2, 3 in 54% yield. Compound 3 was characterized by a single crystal X-ray diffraction analysis, Osmium bonds. The phenyl ring of the phosphine ligand has undergone ortho -metallation by a neighboring metal Atom. A terminally coordinated Si(OMe)_3 ligand is coordinated to the third Osmium Atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted Osmium Atom that is partially filled by a weak interaction with one of the π-bonds of the ortho -metalled phenyl ring. Complex 3 reacts with CO at 1 atm to reform compound 2 in 85% yield in 5 h at 40°C. Crystal Data: for 3 : space group = P2_1/ n , a = 9.911(2) Å, b = 18.451(6) Å, c = 14.872(2) Å, β = 95.64(2)°, Z = 4, 1994 reflections, R = 0.028.

  • The synthesis and structural characterization of Os3(CO)8[Si(OMe)3][μ-PMe2(C6H4](μ-H)2: An unusual unsaturated triOsmium cluster complex
    Journal of Cluster Science, 1995
    Co-Authors: Richard D. Adams, Jeffrey E. Cortopassi
    Abstract:

    The reaction of Os3(CO)10(NCMe)[Si(OMe)3](μ-H),1, with PMe2Ph yielded the new complex Os3(CO)10(PMe2Ph)[Si(OMe)3](μ-H),2 by substitution of the MeCn ligand with the phosphine ligand. When heated to 125°C compound2 was decarbonylated and transformed into the new unsaturated cluster complex Os3(CO)8[μ-PMe2(C6H4)][Si(OMe)3](μ-H)2,3 in 54% yield. Compound3 was characterized by a single crystal X-ray diffraction analysis, Osmium bonds. The phenyl ring of the phosphine ligand has undergoneortho-metallation by a neighboring metal Atom. A terminally coordinated Si(OMe)3 ligand is coordinated to the third Osmium Atom. The cluster is unsaturated by the amount of 2 electrons, and there is an open coordination site on the siloxyl substituted Osmium Atom that is partially filled by a weak interaction with one of the π-bonds of theortho-metalled phenyl ring. Complex3 reacts with CO at 1 atm to reform compound2 in 85% yield in 5 h at 40°C. Crystal Data: for3: space group = P21/n,a = 9.911(2) A,b = 18.451(6) A,c = 14.872(2) A,β = 95.64(2)°,Z = 4, 1994 reflections,R = 0.028.

A. A. Koridze - One of the best experts on this subject based on the ideXlab platform.

Shariff E. Kabir - One of the best experts on this subject based on the ideXlab platform.

  • Synthesis, Structure and Reactivity of Electron Deficient TriOsmium Cluster Bearing 2,6-Dimethylbenzothiazolide Ligand
    Journal of Chemical Crystallography, 2010
    Co-Authors: Shishir Ghosh, Md. Nazim Uddin, Noorjahan Begum, G. M. Golzar Hossain, Kazi A. Azam, Shariff E. Kabir
    Abstract:

    Reaction of [Os_3(CO)_10(NCMe)_2] with 2,6-dimethylbenzothiazole at room temperature affords [Os_3(CO)_10( μ -H){ μ - η ^2-C_7H_2NS(Me)_2}] ( 1 ) in 45% yield. Decarbonylation of 1 in refluxing toluene furnishes the electron-deficient cluster [Os_3(CO)_9( μ -H){ μ _3- η ^2-C_7H_2NS(Me)_2}] ( 2 ) in almost quantitative yield. Treatment of 2 with PPh_3 at 40 °C gives the addition product [Os_3(CO)_9(PPh_3)( μ -H){ μ - η ^2-C_7H_2NS(Me)_2}] ( 3 ) in 85% in which the PPh_3 ligand is coordinated to the rear Osmium Atom. A similar treatment of 2 with P(OMe)_3 gives [Os_3(CO)_9{P(OMe)_3}( μ -H){ μ - η ^2-C_7H_2NS(Me)_2}] ( 4 ) in 60% yield with P(OMe)_3 ligand also coordinated to the rear metal. Compounds 3 and 4 differ by the disposition of the hydride ligands. In compound 4 both the hydride and the heterocyclic ligands simultaneously bridge the same metal–metal edge whereas they bridge different metal–metal edges in 3 . Compounds 1 – 4 have been characterized by a combination of elemental analysis, infrared, NMR and mass spectral data together with single crystal X-ray diffraction studies for 3 . Compound 3 crystallizes in the monoclinic space group P 2_1/ n with a  = 9.2659(10), b  = 23.643(2), c  = 16.382(3) Å, β  = 91.324(12)°, Z  = 4 and V  = 3,587.8(8) Å^3. Graphical Abstract Synthesis and reactivity of electron-deficient 2,6-dimethylbenzothiazole Osmium cluster [Os_3(CO)_9( μ -H){ μ _3- η ^2-C_7H_2NS(Me)_2}] ( 2 ) are described. Reaction of 2 with PR_3 (R = Ph, OMe) furnishes [Os_3(CO)_9(PR_3)( μ -H){ μ - η ^2-C_7H_2NS(Me)_2}] ( 3 , R = Ph; 4 , R = OMe) in which the PR_3 ligand is coordinated to the rear Osmium Atom.

  • Two modes of C-H bond activation of tris(2-thienyl)phosphine in trinuclear Osmium carbonyl clusters
    Journal of Organometallic Chemistry, 2007
    Co-Authors: M. Abdul Mottalib, Shariff E. Kabir, Derek A. Tocher, Antony J. Deeming, Ebbe Nordlander
    Abstract:

    Abstract Tris(2-thienyl)phosphine, P(C 4 H 3 S) 3 , reacts with [Os 3 (CO) 12 ] at 110 °C to give the phosphine-substituted derivatives [Os 3 (CO) 11 {P(C 4 H 3 S) 3 }] ( 1 ), [Os 3 (CO) 10 {P(C 4 H 3 S) 3 } 2 ] ( 2 ) and [Os 3 (CO) 9 {P(C 4 H 3 S) 3 } 3 ] ( 4 ), as well as the C–H activated product [Os 3 (μ-H)(CO) 9 {μ-P(C 4 H 2 S)(C 4 H 3 S) 2 }{P(C 4 H 3 S) 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 [Os 3 (CO) 11 (NCMe)]. The reaction of [Os 3 (μ-H) 2 (CO) 10 ] with tris(2-thienyl)phosphine at room temperature afforded [Os 3 (μ-H) 2 (CO) 9 {P(C 4 H 3 S) 3 }] ( 5 ) and [Os 3 H(μ-H)(CO) 10 {P(C 4 H 3 S) 3 }] ( 6 ), with the ligand coordinated through the phosphorus Atom whereas at elevated temperature the cyclometallated compounds [Os 3 (μ-H)(CO) 9 {μ 3 -P(C 4 H 2 S)(C 4 H 3 S) 2 }] ( 7 ) and [Os 3 (μ-H)(CO) 8 {μ 3 -P(C 4 H 2 S)(C 4 H 3 S) 2 {P(C 4 H 3 S) 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(C 4 H 2 S)(C 4 H 3 S) 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 μ 3 -P(C 4 H 2 S)(C 4 H 3 S) 2 ligand bound through phosphorus to one Os Atom, through a σ –Os–C bond to another and by an η 2 (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.

  • Reactions of Unsaturated Quinoline TriOsmium Clusters [Os_3(CO)_9(μ_3-η^2-C_9H_5(4-R)N)(μ-H)] (R=Me or H) with Tetramethylthiourea: X-ray Structures of [Os_3(CO)_8(μ-η^2-C_9H_5(4-Me)N)(η^2-SC(NMe_2NCH_2Me)(μ-H)_2] and [Os_3(CO)_9(μ-η^2-C_9H_6N)(η^1-S
    Journal of Cluster Science, 2005
    Co-Authors: Noorjahan Begum, Shariff E. Kabir, Dennis W. Bennett, G. M. Golzar Hossain, Ayesha Sharmin, Daniel T. Haworth, Tasneem A. Siddiquee, Edward Rosenberg
    Abstract:

    Treatment of the electronically unsaturated 4-methylquinoline triOsmium cluster $$[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_3\hbox{-}\upeta^{2}\hbox{-}\hbox{C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upmu\hbox{-H})]$$ ( 1 ) with tetramethylthiourea in refluxing cyclohexane at 81°C gave $$[\hbox{Os}_{3}\hbox{(CO)}_{8}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5} \hbox{(4-Me)N})(\upeta^2\hbox{-SC}(\hbox{NMe}_2\hbox{NCH}_2\hbox{Me})(\upmu \hbox{-H})_2]$$ ( 2 ) and $$[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N})(\upeta^1\hbox{-SC}(\hbox{NMe}_2)_2)(\upmu\hbox{-H})]$$ ( 3 ). In contrast, a similar reaction of the corresponding quinoline compound $$[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu_{3}\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upmu\hbox{-H})]$$ ( 4 ) with tetramethylthiourea afforded $$[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu\hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N})(\upeta^{1}\hbox{-SC(NMe}_{2})_{2})(\upmu\hbox{-H)}]$$ ( 5 ) as the only product. Compound 2 contains a cyclometallated tetramethylthiourea ligand which is chelating at the rear Osmium Atom and a quinolyl ligand coordinated to the Os_3 triangle via the nitrogen lone pair and the C(8) Atom of the carbocyclic ring. In 3 and 5 , the tetramethylthiourea ligand is coordinated at an equatorial site of the Osmium Atom, which is also bound to the carbon Atom of the quinolyl ligand. Compounds 3 and 5 react with PPh_3 at room temperature to give the previously reported phosphine substituted products $$[\hbox{Os}_{3}\hbox{(CO)}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{5}\hbox{(4-Me)N)(PPh}_{3})(\upmu\hbox{-H)}]$$ ( 6 ) and $$[\hbox{Os}_{3}\hbox{(CO}_{9}(\upmu \hbox{-}\upeta^{2}\hbox{-C}_{9}\hbox{H}_{6}\hbox{N)(PPh}_{3})(\upmu\hbox{-H)}]$$ ( 7 ) by the displacement of the tetramethylthiourea ligand.

  • Phosphine derivatives of the 4-methylquinoline triOsmium cluster [(μ-H)Os3(CO)10{μ-1,2-η2-C9H5(CH3)N}]: crystal structures of two isomeric compounds [(μ-H)Os3(CO)9{μ-1,2-η2-C9H5(CH3)N}(PPh3)] and [(μ-H)Os3(CO)9{μ-1,2-η2-C9H5(CH3)N}{P(OMe)3}]
    Journal of Organometallic Chemistry, 1998
    Co-Authors: Michael B. Hursthouse, Shariff E. Kabir, K.m. Abdul Malik, Markus Tesmer, Heinrich Vahrenkamp
    Abstract:

    Abstract The 4-methylquinoline triOsmium cluster [(μ-H)Os3(CO)10{μ-1,2-η2-C9H5(CH3)N}] 9 reacts with PPh3 at 110°C to give the mono and bis-substituted products [(μ-H)Os3(CO)9{μ-1,2-η2-C9H5(CH3)N}(PPh3)] 10 and [(μ-H)Os3(CO)8{μ-1,2-η2-C9H5(CH3)N}(PPh3)2] 11, respectively. Similarly the reaction of 9 with P(OMe)3 gives [(μ-H)Os3(CO)9{μ-1,2-η2-C9H5(CH3)N}{P(OMe)3}] 14 and [(μ-H)Os3(CO)8{μ-1,2-η2-C9H5(CH3)N}{P(OMe)3}2] 15. Compound 10 exists as a mixture of three isomers in solution with the major (60%) having the PPh3 ligand on the rear Osmium Atom and the hydride, which initially bridged the same edge as the 4-methylquinoline ligand, migrating to the carbon bound Osmium and the phosphine bearing Osmium edge. In contrast compound 14, in which the P(OMe)3 resides on the unbridged Osmium Atom and the hydride bridges the same edge as the 4-methylquinoline ligand, exists as two isomers in solution. The structures of 10 and 14 have been ascertained by X-ray crystal structure determination. Compound 11 exists as four isomers in solution and 15 as two isomers.

  • TriOsmium clusters derived from the reactions of thioureas with dodecacarbonyltriOsmium: Crystal structures of [Os_3(CO)_11{η ^1-SC(NMe_2)_2}], [Os_3(CO)_9(μ-OH)(μ-OMeOCO){η ^1-SC(NMe_2)_2}] and [(μ-H)Os_3(CO)_9{μ _3-NHC(S)NH_2}]
    Journal of Cluster Science, 1996
    Co-Authors: Kazi A. Azam, Michael B. Hursthouse, Shariff E. Kabir, Edward Rosenberg, Rahima Dilshad, Rashid Miah, Mohammad Shahiduzzaman, Kenneth I. Hardcastle, K. M. Abdul Malik
    Abstract:

    The reaction of [Os_3(CO)_12] with tetramethylthiourea in the presence of a methanolic solution of Me_3NO·2H_2O at 60° yields the compounds [Os_3(CO)_11{ η ^1-SC(NMe_2)_2}] ( 1 ) in 56% yield and [Os_3(CO)_9( μ -OH)( μ -MeOCO){ η ^1-SC(NMe_2)_2}] ( 2 ) in 10% yield in which the tetramethylthiourea ligand is coordinated via the sulfur Atom at an equatorial position. Compound 2 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 [Os_3(CO)_12] with thiourea gives the compounts [( μ -H)Os_3(CO)_10{ μ -NHC(S)NH_2}] ( 3 ) in 8% yield and [( μ -H)Os_3(CO)_9{_3-NHC(S)NH_2}] ( 4 ) in 30% yield. In 3 , the thioureato ligand bridges two Osmium Atoms via the sulfur Atom, whereas in 4 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 [Os_3(CO)_10(MeCN)_2] with thiourea at ambient temperature. Compound 3 converts to 4 (65%) photochemically. Compound 1 reacts with PPh_3 and acetonitrile at ambient temperature to give the simple substitution products [Os_3(CO)_11(PPh_3)] and [Os_3(CO)_11(MeCN)], respectively, while with pyridine, the oxidative addition product [( μ -H)Os_3(CO)_10( μ -NC_5H_4] 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 of 1 , 2 and 4 . Compound 1 crystallizes in the triclinic space group P $$P\bar 1$$ with unit cell parameters a = 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) Å^3, and Z = 2. Least-squares refinement of 4585 reflections gave a final agreement factor of R = 0.0766 ( R _ w = 0.0823). Compound 2 crystallizes in the monoclinic space group P2_1/ n with unit cell parameters a = 9.149(5) Å, b = 17.483(5) Å, c = 15.094(4) Å, β = 91.75(2)°, V = 2413(2) Å^3, and Z = 4. Least-squares refinement of 3632 reflections gave a final agreement factor of R = 0.0603 ( R _ w = 0.0802). Compound 4 crystallizes in the monoclinic space group C2/ c with unit cell parameters a = 13.915(7) Å, b = 14.718(6) Å, c = 17.109(6) Å, β = 100.44(3)°, V = 3446(5) Å^3, and Z = 8. Least-squares refinement of 2910 reflections gave a final agreement factor of R = 0.0763 ( R _ w = 0.0863).