Synthesis, Structure, and Preparative Transamination of Tetrazinc Carbamato Complexes Having the Basic Zinc Carboxylate Structure

Abstract

The series of tetranuclear zinc(II) carbamato complexes (Zn(4)O)(O(2)CR)(6), (1, R = diethylamino; 2, R = piperidino; 3, R = pyrrolidino) was prepared. Complexes 2 and 3 were crystallographically characterized and shown to have the same tetrahedral Zn(4)O(6+) core. Complex 2 crystallizes in the cubic space group I(-)43d, a = 24.0131(5) A, V = 13846.6(5) A(3), R(1976 observed reflections) = 0.0194, and GOF = 1.013. Complex 3 crystallizes in the triclinic space group P(-)1, a = 10.3178(6) A, b = 10.6962(6) A, c = 19.5130(11) A, alpha = 81.9070(10), beta = 75.4880(10), gamma = 81.6540(10), V = 2050.4(2) A(3), R(6141 observed reflections) = 0.0334, and GOF = 0.979. NMR spectroscopy was used to show that the (Zn(4)O)L(6) structure was maintained in nonpolar solvents. The complexes reacted with free amine in nonpolar solvents, which resulted in facile conversion of one member of the series to another. For example, reacting 1 with a stoichiometric amount of pyrrolidine in tetrahydrofuran followed by workup resulted in the quantitative formation of 3 with liberation of diethylamine. Formally, this is a transamination metathesis reaction between the diethylcarbamate ligand and pyrrolidine. The reaction is complete within 3 min at room temperature, in marked contrast to the extreme conditions required to effect transamination on organic carbamates. The complexes also undergo a facile transcarboxylation reaction with carbon dioxide which results in scrambling of the carboxyl group of the carbamate ligand with free CO(2), also complete in about 3 min. Both transamination and transcarboxylation reactions are consistent with the intermediacy of free CO(2). However, because of the propensity for the complexes to hydrolyze to liberate CO(2), the role of adventitious moisture in facilitating the reaction cannot presently be rejected.

N,N‐Dialkylcarbamato Lanthanide Complexes, a Series of Isotypical Coordination Compounds

“…[5,21] The IR spectra of these derivatives show intense and broad bands in the 1650Ϫ1350 cm Ϫ1 region due to the stretching vibrations of the O 2 CN moieties (see Table 1, and the Exp. Sect.).…”

“…[17] Synthesis of [Ln 4 (O 2 CNiPr 2 ) 12 ] (Ln ‫؍‬ Pr, Nd, Eu, Gd, Ho, Er, Yb, Lu): The syntheses were carried out by treating the solvated chlorides [LnCl 3 (ether) x ] (ether ϭ DME, x ϭ 0.5, Ln ϭ Nd; x ϭ 1, Ln ϭ Pr; x ϭ 2, Ln ϭ Eu, Gd, Ho, Yb; ether ϭ THF, x ϭ 1.5, Ln ϭ Nd; x ϭ 0, Ln ϭ Lu) with NHiPr 2 and CO 2 in toluene. Analysis for C 21 Two typical experiments are described below. a) Europium: A solution of NHiPr 2 (16.0 mL, 114.2 mmol) was stirred in a flask under CO 2 until gas absorption was complete.…”

Structures and Sorption Properties of 2-Methylbenzimidazolate-Based Zn(II) Frameworks

“…The in-situ formation of dimethyl carbamate, formate, and hydroxide has been reported in the literature under solvothermal reactions. [15][16][17][18][19][20][21] The dimethyl carbamate 19-21 and formate [16][17][18] ligands were suggested to be generated from the decomposition pathways of DMF molecules under vigorous conditions. The dimethyl carbamate and formate ligands connect Zn1 and Zn2 in the syn-syn mode of carbamate oxygens, and Zn3 and Zn4 in the anti-anti mode of formate oxygens, respectively.…”

Metal Ions Play Different Roles in the Third‐Order Nonlinear Optical Properties of d10 Metal–Organic Clusters

“…[9] The arrangement of the zinc ions and the bridging modes of the dcapp 2À ligands are shown in Figure 6+ core is an almost perfect tetrahedron, with Zn···Zn separations ranging from 3.117 to 3.240 , which is consistent with tetrazinc carbamato complexes having a Zn 4 O 6+ core. [11] Wiberg bond orders of ZnÀZn are about 0.01, thus showing the presence of a weak Zn À Zn metal bond. The corresponding Wiberg bond orders of ZnÀO and ZnÀN are about 0.38 and 0.26, respectively.…”

“…The two tetrahedrons and the octahedron are connected by the two edges Ag2-Ag2A and Ag2B-Ag2C. The edge lengths of the tetrahedra are in the range 2.8329(16)-3.0259 (9) , and in the octahedron the closest Ag···Ag contacts are found and range from 2.6521(9) to 2.9345 (11) . The Ag2···Ag3 distance (2.6521 (9) ) is much shorter than that in elemental silver (2.88 ).…”