Insertion Reactions of Heterocumulenes into Zn−C Bonds: Synthesis and Structural Characterization of Multinuclear Zinc Amidate Complexes

Abstract

Reactions of ZnMe2 with isocyanates RNCO proceeded with insertion of the isocyanate into the Zn-Me bond, yielding the corresponding heteroleptic amidate complexes [MeZnOC(Me)NR]x (R = i-Pr 1, t-Bu 2) and [{MeZn}4Zn{OC(Me)NC6F5}6] 3 in high yields. In contrast, ZnCp*2 reacts with isocyanates and isothiocyanates with formation of the homoleptic complexes of the type [Zn{OC(Cp*)NR}2]2 (R = Et 4, i-Pr 5) and [Zn{SC(Cp*)Ni-Pr}2]2 6. 1 -6 were characterized by elemental analyses, multinuclear NMR( 1 H, 13 C, 19 F) and IR spectroscopy and by single-crystal X-ray diffraction (1, 2, 5).

Insertion Reactions of Heterocumulenes with Zincocene Cp*2Zn

“…Simultaneously, three new singlet signals with a relative intensity of 1:2:2 steadily increases, indicating the formation of σ ‐bonded Cp* groups. Moreover, the 13 C NMR spectra of 1 – 3 each show an additional signal at 170.6 ( 1 ), 167.9 ( 2 ), and 167.8 ( 3 ) ppm, respectively, due to the amidinate backbone as was previously observed by us for amidinate and amidate zinc complexes16,17 (Scheme ).…”

“…Since Cp* 2 Zn was found to react readily with CO 2 ,9 isocyanates CNXyl,14 R NCO,17 and R NCN R with insertion into the Zn–Cp* bond, we became interested in the reaction of zincocene with CS 2 . Compared to CO 2 , CS 2 was reported to show an enhanced chemical reactivity.…”

Zinc, cadmium and mercury

“…This reaction proceeds with loss of Cp*H and is attributed to a partial hydrolysis/condensation process, optimal yields (80%) being achieved through use of non-dried solvent. 6 In contrast, A undergoes a simple double-insertion of isocyanates and isothiocyanates to afford the homoleptic species [Zn{EC(Cp*)NR} 2 ] 2 (E = O, S; R = Et, i Pr), 7 which incorporate chelating and bridging amidate ligands, though these appear equivalent on the NMR timescale. Comparable reactions of ZnMe 2 and isocyanates afford exclusively heteroleptic oligomers [MeZnOC(Me)NR] x (R = i Pr, t Bu), though with C 6 F 5 NCO the unusual cluster [{MeZn} 4 Zn{OC(Me)NC 6 F 5 } 6 ] is obtained instead.…”

Syntheses, Solid-state Structures and Catalytic Activity of Zinc Carboxylate Complexes in Lactide Polymerization

“…We have a long-standing interest in N,Nand N,Ochelating zinc complexes containing β -diketiminate [36 -40], amidinate [41 -46], and amidate ligands [47]. Only recently, we became interested in the polymerization catalysis of cyclic esters and reported on the use of cationic β -diketiminate zinc complexes as well as of neutral tridentate [NNO] zinc complexes containing donor-functionalized β -ketiminate ligands (L 2 ) in the ROP of lactide [48,49].…”