Synthesis, Structural Characterization, and Bonding Analysis of (η⁴-1-azadiene)Fe(CO)₃ Complexes:  Consequences of the Electronic Structure on Molecular and Crystal Properties

Abstract

A series of 1-azadiene ligands as well as the corresponding (η4-azadiene)Fe(CO)3 complexes have been synthesized and structurally characterized by means of single-crystal X-ray diffraction. At the molecular level, the 1-azadiene assumes a trans conformation as free ligand, while a cis coordination is found in the organometallic complexes. In the coordinated ligand the H(C3) hydrogen is found nonplanar with respect to the C−C−C−N plane. A molecular orbital analysis has been carried out by means of extended Hückel calculations. The electronic origin of the out-of-plane position of the 1-azadiene hydrogen atom H(C3) has been justified in terms of a better π*-back-bonding between the 1-azadiene and Fe(CO)3 molecular fragments. A comparison of cis and trans conformations of the ligand has also been performed. The organometallic crystals show the presence of a large number of hydrogen bond interactions of the C−H- - -O type involving CO-ligand acceptors. Hydrogen bonding of the azadiene moiety is always realized by the hydrogen atom at the C−N double bond and the hydrogen atom in α-position with respect to the imine group.

Tricarbonyl[η4-2-phenyl-4-(3-phenylallylidene)-4H-oxazol-5-one]iron(0)

“…The substituents at C9 and C12 are not coplanar with the butadiene ligand systems for steric as well as for electronic reasons, as has frequently been observed for butadiene and 1azabutadiene irontricarbonyl complexes, and in accordance with theoretical investigations on several derivatives (Marr & Rockett, 1982;Adams et al, 1988;Imhof et al, 1999;Gonzalez-Blanco & Branchadell 1997;Gonzalez-Blanco et al 1999;Mills & Robinson, 1963). The butadiene system C9 C10-C11 C12 shows a Z,E configuration together with an s-cis configuration with respect to the C10-C11 bond.…”

Crystal Structure of .BETA.-Phenylcinnamaldehyde-4-bromoaniline

“…The C(6)-N(1)-C(7) bond angle of 120.7(3)˚ is consistent with the sp 2 hybrid character for the N atom. 5 In the crystal, molecules of 1 form inversion generated pairs via weak C-H•N interactions. Then, a near linear C-H•π interaction helps to link the dimeric pairs into chains propagating in [010] ( Fig.…”

α,β-Unsaturated diimines as substrates in catalytic C–H activation reactions and as ligands in iron carbonyl complexes

“…The iron carbon bond lengths in 2 are not identical. As it has been pointed out before [6,7], the bond of Fe1 with C3 is about 7-10 pm longer than Fe1-C2, which again is about 2-3 pm shorter compared to Fe1-C1. There are three molecules in the asymmetric unit of the unit cell, which are linked by C-HÁ Á ÁO interactions (Fig.…”

“…The reaction of acyclic a,b-unsaturated imines with Fe 2 (CO) 9 yields mononuclear iron tricarbonyl complexes [1][2][3][4][5][6][7]. On the other hand, the same imine substrates are converted into c-lactams in the reaction with carbon monoxide and a-olefins catalyzed by Ru 3 (CO) 12 [8][9][10][11][12][13].…”