Dinitrogen Coordination and Cleavage Promoted by a Vanadium Complex of a σ,π,σ-Donor Ligand

Abstract

The deprotonation of the tripyrrole MeTPH(2) [MeTPH(2) = 2,5-[(2-pyrrolyl)(C(6)H(5))2C](2)(MeNC(4)H(2))], containing one N-methylated pyrrolyl ring, was carried out with 2 equiv of KH. The corresponding dipotassium salt reacted with VCl(3)(THF)(3) to afford the complex [(MeTP)VCl(THF)].THF (1). While the two lateral pyrrolide rings are sigma-bonded, the central one is perpendicularly oriented in a sort of pi-fashion. However, the bond distances clearly indicated that only the quaternized N atom is forming a bonding contact. Subsequent reduction of 1 with Na yielded the corresponding divalent complex [(MeTP)V(THF)].(C(7)H(8))(0.5) (2) where the central N-methylated ring adopted a more regular pi-orientation. When treated with a strong Lewis acid (AlMe(3)), THF was extracted from the vanadium coordination sphere, forming the dinuclear dinitrogen complex [(MeTP)V(mu-N(2))](2).(C(7)H(8))(2.9) (3). Reduction of 3 with potassium graphite gave cleavage of dinitrogen, affording the mixed-valent nitride-bridged complex [(MeTP)V(mu-N)](2).(THF) (4).

Experimental and computational studies on the formation of cyanate from early metal terminal nitrido ligands and carbon monoxide

“…Since two of the examples of Step 2 involve a vanadium supported nitride, 6,7 we sought to prepare a low-valent V complex with the requisite number of electrons such that two equivalents can reduce N 2 by 6 electrons. [32][33][34][35] There is precedent for N 2 activation by low valent V II complexes included in the work from the groups of Gambarotta, [32][33][34] Cloke, 36 and Mindiola. 35 (12) was prepared by treating VCl 3 (THF) 3 with two equivalents of the ligand in a frozen Et 2 O slurry.…”

Synthesis and characterization of complexes imparting N-pyridyl bonded meso-pyridyl substituted dipyrromethanes

“…The dipyrromethanes can be oxidatively converted to dipyrromethenes which are fully conjugated flat bipyrrolic moieties, and as such, are useful ligands for chelation to transition metals [11][12][13][14]. Although, numerous homo-/heteroleptic complexes based on dipyrrins are reported in the literature, use of dipyrromethanes as ligand has scarcely been reported [15][16][17][18][19][20]. Furthermore, there has been growing interest in the synthesis of complexes containing g 6 -arene ruthenium, and g 5 -C 5 Me 5 rhodium/iridium complexes because of their catalytic potential and use as precursors in the synthesis of other Ru(II), Rh(III), and Ir(III) complexes [21][22][23][24][25][26][27].…”

Titanium‐Promoted Dinitrogen Cleavage, Partial Hydrogenation, and Silylation

“…In some instances, these ligands may act as electron storage units effectively permitting dinitrogen partial reduction,12 cleavage, and even partial hydrogenation 6b. We have therefore designed a ligand system based on pyrrolide anions containing an additional hemilabile π unit 6c. In fact, the pyrrolide anions are isoelectronic with the cyclopentadienyl anions that have produced a number of dinitrogen complexes,1c,d,e,h,m,l,p, 13 including examples that facilitate dinitrogen reduction 1c,d,e,h,m,l,p.…”