Aminotroponiminate calcium and strontium complexes

Abstract

Heteroleptic aminotroponiminate complexes of calcium and strontium have been prepared. The monomeric calcium complex [((iPr)2ATI)CaI(THF)3] 1 ((iPr)2ATI = N-isopropyl-2-(isopropylamino)troponiminate) and the corresponding dimeric strontium compound [( (iPr)2ATI)SrI(THF)2]2 2 were obtained by reaction of [((iPr)2ATI)K] and MI2. Whereas the mixed ligand compound of composition [((iPr)2ATI)Ca(iPrAT)]2 3 (iPrAT = 2-(isopropylamino)troponate) was not obtained via a salt metathesis but by reaction of [Ca(N(SiMe3)2)2(THF)2] with ( (iPr)2ATI)H and (iPrAT)H, the diphosphanylamido complex [( (iPr)2ATI)Ca((Ph2P)2N)(THF)2] was obtained by reaction of CaI2 with the potassium compounds [( (iPr)2ATI)K] and [K(THF)n][N(PPh2)2]. The single crystal X-ray structures of all compounds were established and the latter compound shows a eta2-coordination mode of the ligand via the nitrogen and one phosphorus atom.

New Perspectives for Aminotroponiminates: Coordination Chemistry, Redox Behavior, Cooperativity, and Catalysis

“…ATI complexes [M(ATI i Pr/ i Pr ){N(SiMe 3 ) 2 (thf) 2 }] ( 25‐M ) of the heavier alkaline earth metals Ca and Sr have been tested as catalysts in intramolecular hydroamination reactions and compared to their Yb II analogs (Scheme ) . The ATI ligand presumably serves as a spectator ligand in these transformations, while the {N(SiMe 3 ) 2 } – group undergoes transamination with the substrate 23 .…”

Heterofunctionalization catalysis with organometallic complexes of calcium, strontium and barium

“…In line with the findings of Hultzsch and coworkers for lanthanide(III) systems ( Gribkov et al 2006), it was suggested that both substrate and product inhibit the reaction to similar extents; hence, reaction-rate constants are dependent upon the substrate concentration at t o . While Crimmin et al refrained from application of heavier analogues of 1 and 2 (M = Sr, Ba; Avent et al 2005b) in hydroamination catalysis owing to their propensity to undergo Schlenk-like redistribution under the reaction conditions, Datta et al (2007Datta et al ( , 2008a reported aminotroponoate and aminotroponiminate supported calcium and strontium amide complexes 3-5 as competent catalysts for the intramolecular hydroamination of aminoalkenes (figure 9). Although, in most instances, selectivities and catalyst activities were commensurate with those reported for the b-diketiminato-stabilized calcium amide 1, it is noteworthy that Datta et al reported not only that 4 mol% 4 was effective for the intramolecular hydroamination of an aminoalkyne to the corresponding imine in more than 90 per cent after 22 h at room temperature, but also that both 4 and 5 affect the cyclization of the internal (activated) alkene trans-1-amino-2,2-dimethyl-5-phenyl-4-pentene to the corresponding pyrrolidine in 80 per cent yield after 10 min at room temperature (figure 10).…”

Benz–amidinato Stabilized a Monomeric Calcium Iodide and a Lithium Calciate(II) Cluster featuring Group 1 and Group 2 Elements

“…Three oxygen molecules from THF occupy the three sites, two N atoms from the amidinato ligand occupy two sites, and the I ligand fills the remaining coordination site. The Ca–I bond length is of 3.084(3) Å, which is shorter than those in G (3.1365(8) Å and 3.1533(8) Å), Westerhausen′s [(thp) 4 Ca(I)(CH 2 SiMe 3 )] (thp=tetrahydropyrran) (3.191(3) Å), and the average Ca–I bond distances in A (3.144 Å), and C (3.106 Å) . The decrease in the bond length is most likely a result of slightly increased donor ability of the amidinates relative to the β ‐diketiminates as well as a weak steric shielding of the calcium center by the ligands.…”