| 1. |
- Rahaman, Ahibur, et al.
(författare)
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Generation of sigma,pi-furyl and thienyl ligands at di-iron centers via facile phosphorus-carbon bond cleavage: Synthesis and molecular structures of [Fe-2(CO)(6)(mu-eta(1),eta(2)-C4H3E){mu-P(C4H3E)(2)}] (E = O, S)
- 2013
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 730, s. 123-131
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Tidskriftsartikel (refereegranskat)abstract
- Treatment of [Fe-3(CO)(12)] with tri(2-furyl)phosphine (PFu(3)) or tri(2-thienyl)phosphine (PTh3) in dichloromethane at 40 degrees C leads to facile phosphorus carbon bond scission affording di-iron furyl- and thienyl-bridged complexes [Fe-2(CO)(6)(mu-eta(1),eta(2)-C4H3E)(mu-P(C4H3E)(2))] (1 E = O, Fu; 3 E = S, Th) in good yields, together with smaller amounts of the phosphine-substituted [Fe-2(CO)(5)(mu-eta(1),eta(2)-C4H3E){mu-P(C4H3E)(2)}[P(C4H3E)(3)}] (2E= O,4 E= S). When the same reactions were carried out at room temperature, small amounts of the tri-iron clusters [Fe-3(CO)(11){P(C4H3E)(3)}] (5 E= O, 6 E = S) were isolated in which the coordinated phosphine(s) remain intact Thermolysis of [Fe-3(CO)(11){P(C4H3E)(3)}] at 40 degrees C in dichloromethane gave [Fe-2(CO)(6)(mu-eta(1),eta(2)-C4H3E){mu-P(C4H3E)(2)}], which also undergo phosphine substitution under similar conditions. However, both of these processes are too slow to account for the reaction product ratios and yields observed in the room temperature reactions. In contrast, addition of catalytic amounts of Na+[Ph2CO](center dot) to 5 resulted in the rapid formation of 1. We therefore propose that these reactions may occur via a radical-initiated mechanism proceeding through the initial formation of the 49-electron radical anions [Fe-3(CO)(11){P(C4H3E)(3)}]center dot. The crystal structures of [Fe-2(CO)(6)(mu-eta(1),eta(2)-Fu)(mu-PFu(2))] (1), [Fe-2(CO)(5)(mu-eta(1),eta(2)-Fu)(mu-PFu(2))(PFu(3))] (2), [Fe-2(CO)(6)(mu-eta(1),eta(2)-Th)(mu-PTh2)] (3) and [Fe-3(CO)(11)(PFu(3))] (5) have been determined. The di-iron complexes all show the expected cis arrangement of three-electron donor ligands, short iron-iron distances consistent with a 34-valence electron count, and, in 2, the phosphine is coordinated to the pi-bound iron atom and lies trans to the metal-metal bond. Close inspection of the bonding parameters within the Fe2C2E core reveals that these alkenyl species are quite different to those without electron-withdrawing substituents. The tri-iron cluster 5 has two independent molecules in the asymmetric unit. Each contains two bridging carbonyls and the molecules differ in the relative positions of these carbonyls and the coordinated phosphine ligand, the latter lying in the equatorial plane in both molecules. (C) 2012 Elsevier B.V. All rights reserved.
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| 2. |
- Rahaman, Ahibur, et al.
(författare)
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Phosphine addition to the sigma,pi-thienyl complex [Fe-2(CO)(6)(mu-Th)(mu-PTh2)] (Th = C4H3S): Carbonyl substitution and migratory carbonyl insertion to give the thienyl-acyl complexes [Fe-2(CO)(4)(diphosphine)(mu-O=C-Th)(mu-PTh2)]
- 2015
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Ingår i: Inorganica Chimica Acta. - : Elsevier BV. - 0020-1693. ; 430, s. 208-215
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Tidskriftsartikel (refereegranskat)abstract
- The reactivity of the sigma,pi-thienyl complex [Fe-2(CO)(6)(mu-Th)(mu-PTh2)] (1) towards a range of phosphines has been studied. With PR3 (R = Ph, Th) carbonyl substitution affords [Fe-2(CO)(5)(PR3)(mu-Th)(mu-PTh2)] (2ab) as the major product, with smaller amounts of the thienylacyl complexes [Fe-2(CO)(5)(PR3)(mu-O=C-Th)(mu-PTh2)] (3ab) resulting from a migratory carbonyl insertion into the thienyl ligand. With diphosphines, thienylacyl complexes are the major products in all cases. With dppm, [Fe-2(CO)(4)(mu-dppm)(mu-O=C-Th)(mu-PTh2)] (4) results in which the diphosphine bridges the ironiron bond, while with other diphosphines the chelate complexes [Fe-2(CO)(4)(kappa(2)-diphosphine)(mu-O=C-Th)(mu-PTh2)] (59) are isolated, as established through crystallographic studies on [Fe-2(CO)(4)(kappa(2)-dppe)(mu-O=C-Th)(mu-PTh2)] (5) and [Fe-2(CO)(4)(kappa(2)-dppb)(mu-O=C-Th)(mu-PTh2)] (9), both of which show that the diphosphine binds selectively to the oxygen-bound metal centre with phosphorus atoms lying trans to the metalmetal bond and mu-PTh2 bridge. With 1,2-bis(diphenylphosphino)benzene (dppb), [Fe-2(CO)(5){mu,kappa(2)-C6H4PPh(C6H4)PPh2}(mu-PTh2)] (10) is isolated in low yields and results from cyclometalation of a phenyl ring and putative elimination of thiophene. In a separate experiment, it has been shown that heating 9 results in the slow formation of 10. (C) 2015 Elsevier B.V. All rights reserved.
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| 3. |
- Rahaman, Ahibur, et al.
(författare)
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Reactions of the sigma,pi-furyl complex [Fe-2(CO)(6)(mu-Fu)(mu-PFu(2))] (Fu = C4H3O) with phosphines: Carbonyl substitution, migratory carbonyl insertion and cyclometallation-induced furan elimination
- 2014
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Ingår i: Journal of Organometallic Chemistry. - : Elsevier BV. - 0022-328X. ; 751, s. 326-335
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Tidskriftsartikel (refereegranskat)abstract
- The reactivity of the sigma,pi-furyl complex [Fe-2(CO)(6)(mu-Fu)(mu-PFu(2))] (1) towards PPh3 and a range of bidentate phosphines has been studied and a number of different reaction products have been identified. With PPh3, carbonyl substitution affords [Fe-2(CO)(5)(PPh3)(mu-Fu)(mu-PFu(2))] (2) in which the new phosphine is coordinated to the iron center that is sigma-coordinated by the bridging furyl moiety. With small bite-angle diphosphines - bis(diphenylphosphino) methane (dppm) and 1,8-bis(diphenylphosphino) naphthalene (dppn) - carbonyl substitution and migratory carbonyl insertion result to give the furyl-acyl complexes with bridging, [Fe-2(CO)(4)(mu-dppm)(mu-O]CeFu)(mu-PFu(2))] (3), or chelating, [Fe-2(CO)(4)(kappa(2)-dppn)(mu-O]CeFu)(mu-PFu(2))] (4), diphosphines, respectively. With the more flexible diphosphines Ph2P(CH2)(n)PPh2 (n = 2, dppe, n = 3, dppp), the cyclometallated products [Fe-2(CO)(5){mu,kappa(2)-C6H4PPh(CH2)(n)PPh2}(mu-PFu(2))] (n = 2, 5; n = 3, 6) are isolated as a result of carbonyl substitution and furan elimination, and a similar complex [Fe-2(CO)(5){mu,kappa(2)-C6H4PPh(C6H4)PPh2}(mu-PFu(2))] (7) is generated from the more rigid diphosphine bis(diphenylphosphino) benzene (dppb). With bis(diphenylphosphino)-1,1-binaphthalene (1,1-BINAP) the novel tridentate phosphine complex [Fe-2(CO)(5){mu,kappa(3)-C6H4P(C20H12PPh2)C(6)H(4)PFu}] (8) results from the putative coupling of cyclometallated diphosphine and difurylphosphido ligands, following elimination of two equivalents of furan. The crystal structures of 2, 3, 5 and 8 have been determined and allow a detailed insight into the overall reaction profile. (C) 2013 Elsevier B.V. All rights reserved.
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