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VK Landry Thesis

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VK Landry Thesis

  1. 1. Preparation and Computational Analysis of s and p Lewis Acid Adducts of Transition Metals<br />Victoria K. Landry<br />Columbia University <br />Department of Chemistry<br />April 9, 2009<br />
  2. 2. The family of L2X ligands is widely used in organometallic chemistry<br />Covalent Bond Classification Method (Green, 1995):L = 2 electron donorX = 1 electron donor/1 electron acceptorZ = 2 electron acceptor<br />The [TpR,R’] and [TmR] ligands have found wide applicability: - Stability of complexes with a wide variety of metals - Facile tailoring of steric and electronic properties - Relevance of donor arrays to modeling of biological coordination environments<br />See Green, M.L.H. J. Organomet. Chem.1995, 500, 127 for description of the MLX formalism.<br />
  3. 3. Selenium-rich tripodal ligands are rare<br />Only previous examples of tripodal <br />selenium donors are neutral selenoethers. <br />Selenium analog of the [TmR] ligand would:Extend the series of widely used L2X type ligands.Provide an [Se3] donor array relevant to modeling of selenoproteins.<br />(R = Me, Ph)<br />Gulliver, D.J. J. Chem. Soc. Perkin Trans. 2, 1984, 429.<br />Barton, A.J. Heteroat. Chem.2002, 13, 550.<br />Levason, W. Coord. Chem. Rev., 2002, 225, 159.<br />
  4. 4. Bi- and tripodal derivatives, [BseR] and [TseR], may be prepared<br />Landry, V. K.; Buccella, D.; Pang, K.; Parkin, G. Dalton Trans.2007, 866-870.<br />Minoura, M.; Landry, V. K.; Melnick, J. G.; Pang, K.; Marchio, L.; Parkin, G. Chem. Comm. 2006, 3990-3992.<br />Prof. Mao Minoura<br />
  5. 5. [TseR] is a stronger electron donor than [TmR], [TpR,R’] and [Cp]<br />Molecular structure of [TseMe]Re(CO)3<br />a. Tellers, D.M.; Skoog, S.J.; Bergman, R.G.; Gunnoe, T.B.; Chem. Comm. 2000, 3990 - 3992.<br />b. Minoura, M.; Landry, V. K.; Melnick, J. G.; Pang, K.; Marchio, L.; Parkin, G. Chem. Comm. 2006, 3990 - 3992.<br />c. Landry, V. K.; Buccella, D.; Pang, K.; Parkin, G. Dalton Trans.2007, 866 - 870.<br />
  6. 6. [TseMes] is less sterically hindering than [TmMes]<br />Average Re-Se bond length (2.64 Å) is longer than average Re-S bond length (2.53 Å).<br />a. Tellers, D.M.; Skoog, S.J.; Bergman, R.G.; Gunnoe, T.B.; Chem. Comm. 2000, 3990 - 3992.<br />b. Minoura, M.; Landry, V. K.; Melnick, J. G.; Pang, K.; Marchio, L.; Parkin, G. Chem. Comm. 2006, 3990 - 3992.<br />c. Landry, V. K.; Buccella, D.; Pang, K.; Parkin, G. Dalton Trans.2007, 866 - 870.<br />
  7. 7. Bi- and tripodal derivatives, [BseR] and [TseR], may be prepared<br />Landry, V. K.; Buccella, D.; Pang, K.; Parkin, G. Dalton Trans.2007, 866-870.<br />Minoura, M.; Landry, V. K.; Melnick, J. G.; Pang, K.; Marchio, L.; Parkin, G. Chem. Comm. 2006, 3990-3992.<br />
  8. 8. Descriptions of (seimMe)H in the literature are inconsistent<br /><ul><li> The sulfur analog (mimR)H is known to exist as the thione tautomer
  9. 9. F. Guziec et al. (1994):
  10. 10. Isolated orange compound (1JSe-C = 220 Hz)
  11. 11. Reported isolation of (seimMe)H as the selone tautomer
  12. 12. G. Mugesh et al. (2004):
  13. 13. Reported isolation of (seimMe)H as the selenol tautomer
  14. 14. Asserted that selone tautomer could not be isolated</li></li></ul><li>(seimR)H (R = Me, Mes) were isolated at the selone tautomers<br />d(C-Se)avg = 1.849 Å<br />d(N…Se)avg = 3.400 Å<br />Preparation was carried out under rigorously anaerobic conditions.Hydrogen attached to nitrogen was located and refined, supporting the selone structure.<br />
  15. 15. Zwitterionic resonance structure of (seimR)H is a major contributor<br />Delocalization of electrons in imidazole ring.Minimal p overlap of Se p-orbital and p-orbital of the adjacent carbon.<br />
  16. 16. Selone tautomer is thermodynamically more stable than selenol<br />Single-point energy calculations on geometry optimized structures of the selone and selenol tautomers confirm that the selone is the thermodynamically more stable tautomer.<br />
  17. 17. Diselenide forms with exposure to air during workup<br />d(Se1-Se2) = 2.3298(4)<br />d(Se1-C11) = 1.896(3)<br />d(Se2-C21) = 1.901(3)<br />
  18. 18. Selone/diselenide exchange observed in 77Se NMR spectrum<br />mixture<br />mixture<br />Exchange rate ≈ 250,000 s-1<br />
  19. 19. Exchange mechanism involves selenolate intermediate<br />
  20. 20. Conclusions<br />(seimR)H (R = Me, Mes) exist as the selone tautomer in the solid state.The zwitterionic resonance structure of the selone tautomer of (seimR)H (R = Me, Mes) is an important contributor.The selone tautomer of (seimMes)H is thermodynamically more stable than the selenol tautomer.The selone (seimR)H and diselenide (seim)2 undergo rapid exchange on the 77Se NMR time scale.<br />
  21. 21. Preparation and Computational Analysis ofs Lewis Acid Adducts of Transition Metals<br />
  22. 22. Simple transition metal borane adducts have not been characterized<br />Since 1960’s, simple adducts suggested, but never structurally characterized:Transition metal adducts to other Lewis acids are known:<br />G.W. Parshall (1963)<br />D.F. Shriver (1963)<br />R.E. Hughes (1979)<br />G. Parkin (2002)<br />
  23. 23. Metallaboratrane frameworks support MB interactions<br />d(Ru-B) = 2.161(5) Å<br />Verkade, J.G. Coord. Chem. Rev.1994, 137, 233-395.<br />
  24. 24. Borane is a Z ligand.Metal must use 2 electrons in bonding of borane moiety.[k4-B(mimMe)3]Pt(PPh3) isdivalent, d8.<br />Description of dn count of metallaboratranes is inaccurate in literature<br />valence:number of electrons an atom uses in bondingdn configuration: number of metal d electrons not involved in ligand bonding<br />
  25. 25. Rhodium and iridium boratranes were prepared from the [Tmt-Bu] ligand<br />[k4-B(mimBut)3]M(PPh3)Cl (M = Rh, Ir)<br />[TmR]K = <br />
  26. 26. Rhodium and iridium boratranes were prepared from the [Tmt-Bu] ligand<br />a. Two crystallographically independent molecules<br />
  27. 27. DFT calculations were used to analyze the IrB interaction <br />Derived from experimentally determined atomic coordinates<br />Modified to eliminate Ir-B bonding interaction<br />
  28. 28. MO diagram of [k4-B(mimH)3]Ir(PH3)Cl shows d6 configuration at iridium<br />
  29. 29. 3-center-4-electron interaction develops upon borane coordination<br />
  30. 30. dn to dn-2 transformation upon borane coordination may be generalized<br />Upon borane coordination:(a) valence increases by 2 (b) dn becomes dn-2<br />
  31. 31. Conclusions<br />Rhodium and iridium complexes featuring MB interactions have been prepared.The dn configuration of a metal center becomes dn-2 upon borane coordination.The dn configuration of a metal center is determined by:n = number of valence electrons on neutral atom - valence <br />
  32. 32. Preparation and Computational Analysis ofp Lewis Acid Adducts of Transition Metals<br />
  33. 33. Transition metal nitrosyl complexes have been widely studied <br />Transition metal nitrosyl complexes have been studied for over a century.<br />NO is a biologically relevant signaling molecule, binding heme iron and other metals in vivo.<br />Lee, D.-H.; Mondal, B.; Karlin, K.D. in Activation of Small Molecules; Tolman, W.B., Ed. Wiley-VCH:Weinheim, 2006; p. 48.<br />
  34. 34. NO has been described as a “suspect” ligand<br />NO can bind to metals in a linear or bent conformation: Bent NO- Linear NO+<br />NO- and NO+ formalism leads to unusual <br />oxidation number assignments:<br />“The formal oxidation states in Co(CO)3(NO), Fe(CO)2(NO)2, Mn(CO)(NO)3, and Cr(NO)4 have the unrealistic values of <br />-1, -2, -3, and -4 respectively!”<br />- Richter-Addo & Legzdins<br />Enemark-Feltham Notation:{MNO}nn = number of d electrons on metal <br />when nitrosyl is considered NO+<br />Richter-Addo, G.B.; Legzdins, G.B. Metal Nitrosyls, Oxford University Press, New York, 1992.<br />Jørgensen, C.K. Coord. Chem. Rev.1966, 1, 164.<br />Enemark, J.H.; Feltham, R.D. J. Am. Chem. Soc.1974, 15, 5002.<br />
  35. 35. Nickel nitrosyl complexes have been prepared <br />First examples of nickel nitrosyl complexes supported by [N3] and [Se3] ancillary donor arrays.<br />
  36. 36. Crystal structures of [TseMes]NiNO and [TpMe,Me]NiNO reveal linear NO <br />a. Two crystallographically independent molecules<br />b. Two bands may be due to splitting or an unknown impurity<br />
  37. 37. Crystal structures of [TseMes]NiNO and [TpMe,Me]NiNO reveal linear NO <br />Ni (group 10 metal)<br />[TpMe,Me]-<br />NO+<br />Ni (group 10 metal)<br />[TseMes]-<br />NO+<br />Traditional analysis predicts d10 configuration at nickel.<br />
  38. 38. MO diagram of [TpMe2]NiNO reveals d6 configuration at nickel <br />Linear NO is X3,<br />requires 3 metal electrons.<br />NO+ formalism for linear NO does not accurately depict electronics of system.<br />
  39. 39. Linear nitrosyl ligands have metal-nitrogen triple bond character <br />Schematic depiction of linear nitrosyl may be clarified from:to:<br />Akin to hypothetical nitride:<br />d(Ni-N)= 1.622 Å<br />
  40. 40. Linear nitrosyl ligand may be described as a “nitride oxide” <br />Observed reactivity of linear nitrosyls and nitrides support X3 depiction: - Deoxygenation of linear nitrosyl to give nitride - Oxygenation of nitride to give nitrosyl - Protonation, methylation of oxygen of linear nitrosyl<br />Gray has described analogy of nitrosyl and nitride: <br />“Assigning Mn(V) to the nitrido complex and Mn(I) to the nitrosyl makes little sense.” <br />
  41. 41. ScNO is a simple model system for a linear nitrosyl <br />
  42. 42. Conclusions<br />Linear nickel nitrosyl complexes supported by [N3] and [Se3] ancillary ligands have been prepared.Linear transition metal nitrosyl ligands exhibit metal-nitrogen triple bond character and may be treated as an X3 ligand (akin to a nitride oxide) for electron counting purposes.<br />
  43. 43. Acknowledgements<br />Research AdvisorProf. Gerard ParkinDefense CommitteeProf. Jack NortonProf. Nick TurroProf. Joe TanskiProf. John MagyarPast Group MembersProf. Mao MinouraProf. Daniel RabinovichDr. Guang ZhuProf. Josh FigueroaDr. Jon MelnickDr. Bryte KellyDr. Daniela BuccellaDr. Keliang PangJoseph UlichnyStephanie QuanCurrent Group MembersKevin YurkerwichAaron SattlerWes SattlerYi RongAhmed Al-HarbiDepartmental StaffDr. John DecaturDr. Yasuhiro ItagakiFamilyLarry KosillaMom and DadJimmy, Mary Ellen, and JimmyFundingNDSEG<br />
  44. 44. Ni-N-O / ° = 149.1(3) / 153.1(3)<br />B-H…Ni / Å = 2.70 / 2.77 <br />A bent nickel nitrosyl may be prepared from the [BseMe] ligand <br />CSD contains Ni-N-O angles ranging from 151.8° - 179.2°. Distorted trigonal bipyramidal coordination about nickel.<br />
  45. 45. The B-H…Ni interaction does not cause the bent nitrosyl<br />
  46. 46. The B-H…Ni interaction does not cause the bent nitrosyl (con’t)<br />
  47. 47. [BseMe]Ni(PPh3)(NO) gains stabilization upon bending<br />Unfavorable Ni dz2 - NO sp overlap relieved. Favorable Ni dz2 - NO p* overlap engaged.<br />Mingos, D.M.P. Inorg. Chem.1973, 12, 1209.<br />
  48. 48. [BseMe]Ni(PPh3)(NO) has an analogous donor set<br />[BseMe]Ni(PPh3)(NO) is lower symmetry than [TpMe,Me]NiNO and [TseMes]NiNO.<br />
  49. 49. Mingos has shown that {MNO}10 with C3v symmetry do not gain stabilization upon NO bending because the <dz2, p*(NO)> antibonding combination is occupied.<br />Relative energies of molecular orbitals determine NO bending<br />Order of molecular orbitals in lower symmetry four-coordinate complexes is such that the <dz2, p*(NO)> antibonding combination is not occupied, and therefore bending of the nitrosyl affords stabilization. <br />Mingos, D.M.P. Inorg. Chem.1973, 12, 1209.<br />
  50. 50. {MNO}10 with C3v symmetry do not gain stabilization upon NO bending<br />
  51. 51. Resonance structures of the [TmR] ligand<br />

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