Synthesis Structures And Spectroscopy Of Pentadienyl Ruthenium Phosphine Complexes

Author : Wipark Anutrasakda
Publisher :
ISBN 13 :
Total Pages : 928 pages
Book Rating : 4.:/5 (866 download)

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Download or read book Synthesis, Structure, Spectroscopy, and Reactivity of Azapentadienyl-M-phosphine Complexes (M written by Wipark Anutrasakda and published by . This book was released on 2013 with total page 928 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation focuses on the systematic synthesis of azapentadienyl-M-phosphine complexes (M = Co, Rh, Ir). The key synthetic approach involves the treatment of chloro-Mphosphine precursors with potassium tert-butylazapentadienide reagent. The reactivity of the parent azapentadienyl compounds with triflic acid and 2e- donor ligands are also investigated. Treatment of (Cl)Co(PMe3)3 with potassium tert-butylazapentadienide produces ((1,2,3- [eta]3)-5-tert-butylazapentadienyl)Co(PMe3)3 (1). Compound 1 undergoes ligand substitution reactions with trimethyl phosphite and carbon monoxide, generating ((1,2,3-[eta]3)-5-tertbutylazapentadienyl) Co(PMe3)2L (2, L = P(OMe)3; 3, L = CO). Compounds 1-3 react readily with 1 equiv of triflic acid (HO3SCF3) at the azapentadienyl nitrogen, producing the corresponding [eta]4-(tert-butylamino)butadiene-cobalt complexes (4-6). One of the key features of these monoprotonated complexes is the very long Co-C4 bond distances, indicating that [eta]3- resonance structures are contributing to the overall bonding picture. Treatment of compound 4 with P(OMe)3 or CO leads to formation of Co(PMe3)2[P(OMe)3]3 +O3SCF3 - (7) or Co(PMe3)3(CO)2 +O3SCF3 - (8), respectively, and both cases lead to displacement of (tertbutylamino)butadiene (rather than PMe3 ligand exchange). Further addition of triflic acid to 5 leads to a second protonation at nitrogen, yielding the corresponding ammonium salt 9. Compound 9 possesses an [eta]4-(tert-butylammonium)butadiene ligand with a strong Co-C4 interaction. Treatment of [(cyclooctene)2Rh([mu]-Cl)]2 with 4 equiv of PR3 (R = Me, Et), followed by potassium tert-butylazapentadienide, produces 16e- ((1,2,3-[eta]3)-5-tertbutylazapentadienyl) Rh(PR3)2 (10, R = Me; 16, R = Et). Similarly, the reaction of [(cyclooctene)2Rh([mu]-Cl)]2 with 6 equiv of PMe3, followed by potassium tertbutylazapentadienide, generates 18e- ((1,2,3-[eta]3)-5-tert-butylazapentadienyl)Rh(PMe3)3 (13). These neutral compounds react cleanly with 1 equiv of triflic acid. In each case, the primary site of reactivity is the nitrogen atom, leading to the formation of monoprotonation products (11, 14, and 17). When the monoprotonated compounds are treated with additional triflic acid, the second protonation occurs at the rhodium center, producing unstable metal-hydrides. These species reductively eliminate protonated tert-butylcrotonaldimine and ultimately produce isolable octahedral Rh(III) complexes (12, 15 and 18) after addition of a third equiv of triflic acid. The reaction of [(cyclooctene)2Ir([mu]-Cl)]2 with 4 or 6 equiv of PEt3, followed by potassium tert-butylazapentadienide, leads to the formation of ((1,2,3-[eta]3)-5-tertbutylazapentadienyl) Ir(PEt3)x (20, x = 2; 24, x = 3). Iridium compound 20 reacts with triflic acid at the metal center, producing an iridium-hydride product, 21, in which the azapentadienyl ligand coordinates in an unusual [eta]3, [eta]1-fashion, while iridium compound 24 reacts at nitrogen to produce the corresponding [eta]4-butadiene product, 25. The monoprotonated iridium compounds react with additional acid at nitrogen. In the case of monoprotonated compound 21, treatmentwith chloride (to release N from Ir), followed by addition of acid, produces the N-protonated [eta]3- tert-butylazapentadienyl product (23). Similarly, treatment of monoprotonated compound 25 with additional acid leads to a second protonation at nitrogen and production of the [eta]4-(tertbutylammonium) butadiene product (26).