Coordination Chemistry from Trigonally Coordinated Iron Platforms: Chemistry Relevant to Dinitrogen Reduction.

摘要

The synthesis for a sterically encumbered, strong-field tris(diisopropylphosphino)borate ligand, [PhBPiPr3] ([PhBPiPr3] = [PhB(CH 2PiPr2)3] -), is reported to probe aspects of its conformational and electronic characteristics within a host of complexes. To this end, the Tl(I) complex, [PhBPiPr3]Tl, was synthesized, characterized, and used to install the [PhBPi Pr3] ligand onto complexes of Fe, Co, and Ru. The spectroscopic, electrochemical, magnetic, and structural features of these complexes are compared with similar examples.;Trigonally coordinated "[PhBPi Pr3]M" platforms (M = Fe, Co) support both pi-acidic (N 2) and pi-basic (NR2-) ligands at a fourth binding site. Methylation of monomeric [M0(N2)-] species successfully derivatizes the beta-N atom of the N2 ligand and affords the diazenido product [MII(N2Me)]. Addition of RN3 to MI(N2)MI results in oxidative nitrene transfer to generate [PhBPi Pr3]M≡NR with concomitant N2 release.;A tetrahedrally coordinated L3Fe-Nx platform that accommodates both terminal nitride (L3FeIV≡N) and dinitrogen (L3FeI-N2-FeIL 3) functionalities is described. The diamagnetic L3Fe IV≡N species featured has been characterized in solution under ambient conditions by multinuclear NMR (1H, 31P, and 15N) and infrared spectroscopy. The terminal nitride complex oxidatively couples to generate the previously reported L3Fe I-N2-FeIL3 species.;The [PhBPiPr3] ligand can support a single iron or cobalt center in a pseudo-tetrahedral environment in which dinitrogen is bound in the fourth coordination site. Zero-valent metal-dinitrogen complexes have the general formula, [[PhBP iPr3]M(mu-N2)] 2[Mg2+], while bridging structures can also be obtained as neutral [MI]---N2---[MI] or as anionic [(M)2(N2)]- species. The nature of the structural distortions observed in both [M(mu-N2)] 2[Mg2+] and [Mn]---N2---[M n] complexes are described. Magnetic characterization of the neutral and mixed-valence dimeric complexes reveal the complexes remain ferromagnetically coupled over all temperatures investigated.;The coordination chemistry of group VIII metals featuring the bis(8-quinolinyl)amine (HBQA) ligand is presented. The electrochemical behavior of Fe, Ru, and Os complexes bearing the BQA ligand is reported and compared to related ligand platforms. Halide and phosphine ligand exchange reactions are examined from complexes of the type (BQA)MX(PR3)2 (M = Ru, Os). Carbonyl and dinitrogen complexes of Ru and Os are prepared from halide abstraction from divalent Ru and Os precursors. The spectroscopic and structural features of these complexes are compared with similar examples.