Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2013. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references. / The niobium-phosphorus triple bond in [P=-Nb(N[Np]Ar)3]- (Np = CH2tBu; Ar = 3,5-Me2C6H3) has produced the first case of P4 activation by a metal-ligand multiple bond. Treatment of P4 with the sodium salt of the niobium phosphide complex in weakly-coordinating solvents led to the formation of the C3-symmetric cyclo-P3 anion, while in THF, it led to the formation of the cyclo-P5 anion [(Ar[Np]N)([eta]4-P5)Nb(N[Np]Ar)2]-. The latter represents a rare example of a substituted pentaphospha-cyclopentadienyl ligand and may be interpreted as the product of trapping an intermediate h5-P5 structure through the migration of one anilide ligand. A search for methods of activating P4 that avoid tedious metal-mediated steps led to the discovery of an incredibly simple procedure involving only commercial reagents. Irradiation of solutions containing P4 and readily available 1,3-dienes produced bicyclic organic diphosphanes in an atom-economical, one-step protocol. Use of 2,3-dimethylbutadiene allowed the isolation of the bicyclic diphosphane P2(C6H10)2 in gram-quantities, but other dienes such as 1,3-butadiene, isoprene, 1,3-pentadiene, and 1,3-cyclohexadiene also provided evidence for incorporation of P2 units via double Diels-Alder reactions. Theoretical investigations provided support for the formation of P2 molecules from photo-excited P4. Investigations into the physical and chemical characteristics of P2(C6H10)2 uncovered an unprecedented stability towards cleavage of the P-P bond relative to other diphosphanes. P2(C6H10)2 exhibits a flexible, yet robust bicyclic framework containing lone pairs disposed at an angle of ca. 45°, and proved to be ideally suited to form multiple bridges between two metal centers. Dinuclear complexes containing tetrahedral, zero-valent group 10 metals bridged by three diphosphane ligands were investigated in detail. These contain D3h-symmetric {M2P6} barrelene cages with metal-metal distances of 4 Å , and exhibited substitution reactions where the cages remain intact. Alternatively, diphosphane P2(C6H10)2 allowed for unprecedented selectivity towards functionalization of a single phosphorus lone pair. Additional functionalization proceeds at a significantly slower rate, thus enabling the selective isolation of various phosphoranes (EP2(C6H10)2 and E2P2(C6H10)2; E = O, S, N-R). Metalation reactions with the bulky diiminodiphosphorane ligand (MesN)2P2(C6H10)2 allowed for multiple metal complexes, showing that such ligands provide an attractive pre-organized binding pocket for transition metals, as well as post-transition metals. / by Daniel Tofan. / Ph.D.
| Identifer | oai:union.ndltd.org:MIT/oai:dspace.mit.edu:1721.1/82170 |
| Date | January 2013 |
| Creators | Tofan, Daniel |
| Contributors | Christopher C. Cummins., Massachusetts Institute of Technology. Department of Chemistry., Massachusetts Institute of Technology. Department of Chemistry. |
| Publisher | Massachusetts Institute of Technology |
| Source Sets | M.I.T. Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 4, [1], ii-xviii, 189 p., application/pdf |
| Rights | M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission., http://dspace.mit.edu/handle/1721.1/7582 |
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