625857-62-7Relevant articles and documents
Reactions of diphosphine-stabilized tetracobalt carbonyl clusters with -Si(OR)3-functionalized alkynes
Choualeb, Aldjia,Braunstein, Pierre,Rose, Jacky,Bouaoud, Salah-Eddine,Welter, Richard
, p. 4405 - 4417 (2008/10/08)
Short-bite ligand cluster stabilization is achieved in the tetrahedral clusters [Co4(μ-CO)3 (CO)7(μ-dppy)] (1a-c), obtained in high yields by reactions of [Co4(CO)12] with 1 equiv of the diphosphine ligands dppy, Ph2PCH2PPh2 (dppm), Ph2PNHPPh2 (dppa), or (Ph2P)2N-(CH2)3Si(OEt)3 (dppaSi), respectively. The structure of 1a has been determined by X-ray diffraction, and the P atoms occupy axial positions on the basal face, transoid to a Co-Co bond. Clusters 1a-c were reacted with phenylacetylene to afford the corresponding butterfly clusters [Co4(μ-CO)2(CO)6(μ-dppy)(μ4 -η2-PhC2H)] (2a-c) by insertion of the alkyne into a Co-Co bond of the precursor. This was established by an X-ray diffraction study of [Co4(μ-CO)2-(CO)6(μ-dppm) (μ4-η2-PhC2H)] (2a). In an alternative synthetic procedure, the alkyne cluster [Co4(CO)10 (μ4-η2-PhC2H)] (3), prepared from [Co4(CO)12] and phenylacetylene, was reacted with the diphosphines dppy. This led in good yields to butterfly clusters, isomeric with 2a-c in terms of the position of the bridging carbonyls, as revealed by an X-ray diffraction study of the dppa derivative 2′b·0.5CH2Cl2. To obtain suitable cluster precursors to sol-gel materials, we have reacted 1a,b with the new trialkoxysilyl alkyne PhC≡CC(O)NH(CH2)3-Si(OMe)3 (L1) and isolated the corresponding functionalized butterfly clusters [Co4(μ-CO)2-(CO)6(μ-dppy) {μ4-η2-PhC2C(O)NH (CH2)3Si(OMe)3}] (4a,b), respectively. Similar reactions between 1a,b and the alkyne HC≡CCH2NHC(O)NH(CH2)3Si(OEt)3 (L2) afforded the related clusters [Co4(μ-CO)2(CO)6(μ-dppy){μ4 -η2-HC2CH2NHC(O)NH (CH2)3Si(OEt)3}] (5a,b). The cluster [Co4(μ-CO)2(CO)6(μ-dppm){μ4 -η2-HC2(CH2)2 OC(O)NH(CH2)3Si(OEt)3}] (6a) was obtained by reaction of 1a with HC≡C(CH2)2OC(O)NH(CH2)3Si(OEt) 3 (L3). Reaction of [Co4-(CO)12] with L1 led to the formation of the dinuclear complex [Co2(CO)6{μ-η2-PhC2C(O)NH-(CH 2)3Si(OMe)3}] (7), which was also prepared by reaction of [Co2(CO)8] with L1. Reaction of 1a with dppaSi afforded the mixed-diphosphine cluster [Co4(μ-CO)3(CO)5(μ-dppm)(μ-dppaSi)] (8), which was characterized by X-ray diffraction. In the course of attempts at linking two molecules of 2a with 1,4-diodobenzene under Sonogashira conditions, the dinuclear complex [Co2(CO)4(μ-dppm) {μ-η2-PhC2H}] (9) was isolated instead. Reaction of 1,4-bis-(trimethylsilyl)butadiyne (L4) with [Co4(CO)12] afforded the known complex [{Co2 (CO)6(μ2-η2-Me3 SiC2-)}2] (10) and with 1a yielded the desired product [Co4(CO)8(μ-dppm)(μ4-η2-Me 3SiC2C≡CSiMe3)] (12), in addition to the known complex [Co2(CO)4(μ-dppm)(μ-η2-Me3 SiC2C≡CSiMe3)] (13). Proto-desilylation of 12 using TBAF/THF-H2O occurred unexpectedly at the cluster core-bound alkyne carbon to afford [Co4(μ-CO)2(CO)6(μ-dppm)(μ4 -η2-HC2-C≡CSiMe3)] (16), instead of the anticipated cluster [Co4(μ-CO)2(CO)6(μ-dppm)(μ4 -η2-Me3-SiC2C≡CH)]. The crystal structure of 16 has been determined by X-ray diffraction.
