Self-Assembly of Reactive Linear Cu3 Building Blocks for Supramolecular Coordination Chemistry and Their Reactivity toward E(n) Ligand Complexes

Abstract

This study describes the selective synthesis of linear, trinuclear, halide-bridged Cu(I) complexes [Cu3(μ-X)2(μ-dpmp)2(MeCN)2](+) (1a: X = Cl; 1b: X = Br; 1c: X = I) stabilized by the tridentate dpmp ligand obtained by self-assembly reactions in THF/MeCN. Upon drying, the MeCN ligands can be removed and the complexes are transformed to the reactive parent trinuclear [Cu3(μ-X)2(μ-dpmp)2](+) (2a-c) building blocks with two vacant coordination sites on the terminal Cu atoms. Another synthesis in CH2Cl2 directly yields 2a-c. Additionally, two related isomeric compounds, 2a* and 2c*, and two CH2Cl2-ligated complexes, [Cu3(μ-X)2(μ-dpmp)2(CH2Cl2)2](+) (X = Br (3b), I (3c)), were structurally characterized. The frameworks of the cationic [Cu3(μ-X)2(μ-dpmp)2](+) complexes are stable in solution at low temperatures and show dynamic coordination behavior at elevated temperatures, indicated by new signals arising in the (31)P{(1)H} NMR spectra. This evolution cannot be shifted back by decreasing the temperature again. However, cationic [Cu3(μ-X)2(μ-dpmp)2](+) (X = Cl, Br, I) complexes can be obtained selectively in the solid state upon crystallization. Although reactions of 2a-c with complexes [{CpMo(CO)2}2(μ,η(2):η(2)-E2)] (E = P (A1), As (A2)) led to unsymmetrically substituted [Cu3(μ-X)2(μ-dpmp)2(η(1)-L)](+) (4a-c: X = Cl-I, L = A1; 5: X = Cl, L = A2) complexes, reactions with the cyclo-P3 complex [CpMo(CO)2(η(3)-P3)] (B) afforded zigzag chain polymers [Cu3(μ-X)2(μ-dpmp)2(μ,η(1):η(1)-B)]n[BF4]n (6a: X = Cl; 6b: X = Br) and symmetrically substituted complex [Cu3(μ-I)2(μ-dpmp)2(η(1)-B)2](+) (7). Reactions of 2a-c with cyclo-E5 complexes [Cp*Fe(η(5)-E5)] (E = P (C1), As (C2)) led to the isolation of one-dimensional coordination polymers [Cu3(μ-X)2(μ-dpmp)2(μ,η(1):η(1)-L)]n[BF4]n (8a-b: X = Cl-Br, L = C1; 9: X = Cl, L = C2) and symmetrically substituted complex [Cu3(μ-I)2(μ-dpmp)2(η(1)-C1)2](+) (10). All products exhibit a trinuclear, cationic [Cu3(μ-X)2(μ-dpmp)2](+) complex as the central structural motif. Variation of the intramolecular Cu-Cu distances inside the Cu3 complexes is discussed, and supporting DFT computations for the model complex [Cu3(μ-Cl)2(dmmp)2{(η(1)-A1)}](+) (4a') are presented.