Five- and Six-Coordinate Group 4 Compounds Stabilized by β-Ketiminate and Diketiminate Ligands:  Syntheses and Comparisons between Solid-State and Solution Structures

Abstract

The preparation and reaction chemistry of beta-diketiminate titanium and zirconium complexes is described. Amine elimination reactions work well for introducing Tolnacnac or Tolnacac to the metal centers (TolnacnacH = 2-(p-tolylamino)-4-(p-tolylimino)-2-pentene; TolnacacH = 4-p-toluidinopent-3-en-2-one). In certain cases, the iminium salt of the diketimine can be used to circumvent the unfavorable reaction kinetics. Salt elimination reactions starting from group 4 metal halides and beta-diketiminate lithium reagents are the most versatile method for introducing beta-diketiminate ligands to the metal. For (beta-diketiminate)MCl(3) compounds (M = Ti, Zr) eta(5)- and eta(2)-coordination modes can be controlled by modifying the diketiminate ligands. Several structures of five- and six-coordinate metal complexes were solved by X-ray diffraction methods. Five-coordinate metal complexes adopt both trigonal bipyramidal and square pyramidal geometries, and the six-coordinate metal complexes possess pseudooctahedral metal centers. For (Tolnacnac)(2)ZrX(2) (X = Cl, OR, NMe(2)) the activation parameters for Lambda/Delta conversion have been probed by dynamic NMR and are consistent with a Bailar-twist mechanism. At a common temperature, the isomerization rates follow the order Cl > OR > NMe(2).

The Synthesis, Structure and Reactivity of B(C6F5)3‐Stabilised Amide (MNH2) Complexes of the Group 4 Metals

“…These in turn are similar to those found in other structurally characterised dialkylamido complexes including VII. [32][33][34][35] Despite the poor solubility of 4, very small crystals were obtained at the interface between solutions of [ZrA C H T U N G T R E N N U N G (NMe 2 ) 4 ] and 1 in toluene and the solid state structure was determined by diffraction methods using synchrotron radiation. [22] Compound 4 adopts a distorted trigonal-bipyramidal geometry in which the amidoborate and amino ligands are coordinated trans to one another (N1-Zr1-N5 = 173.45(13)8; Figure 3).…”

Genuine Heteroleptic Complexes of Early Rare‐Earth Metals: Synthesis, X‐ray Structure, and Their Use for Stereospecific Isoprene Polymerization Catalysis

“…[21,50] (p-tol)NNK was prepared by treatment of the corresponding diketimine with KH in THF. The syntheses of the monocyclopentadienyllanthanide precursors [Cp*'LnX 2 (thf) n ] (Ln = Nd, Sm; X = BH 4 , Cl; n = 0, 1), [33] as well as the ansa-samarocene catalysts [10] have been described elsewhere.…”

A Tetranuclear Hydroxo‐Bridged Copper(II) Complex with PrimaryN‐Acylamidines as Ligands: Preparation, Structural, and Magnetic Characterisation

“…They resemble β-dialkylamino-acroleine derivatives which have found various applications in coordination chemistry. [16] The nitrogen atom in the 3-position of N-acylamidines (1) has a distinct influence on the electronic properties and on the reactivity of these ligands towards metal ions. A major advantage of the Nacylamidines (1) is that they are easily prepared by simple acylation of the corresponding amidines with acyl chlorides in yields of up to 97 %.…”