Synthesis and Structure of Self‐Complementary {2}‐Metallacryptates and Their Linear or Meandering Infinite Arrangements in the Solid State

Reaction of bis(1,3‐diketone) H 2 L 1 in the presence of cesium acetate with magnesium acetate yielded crystalline one‐dimensional coordination polymer rac ‐( 2 ) n . The {2}‐metallacryptand core [Mg 2 (L 1 ) 3 ] 2– is composed of two magnesium centres linked through three bis(1,3‐diketo) dianions (L 1 ) 2– . These {2}‐metallacryptands are homochiral with either (Δ,Δ)‐ fac or (Λ,Λ)‐ fac stereochemistry at the magnesium centres, and they are capable to host a cesium ion in the cavity. Charge compensation of the thus formed {2}‐metallacryptates {Cs⊂[Mg 2 (L 1 ) 3 ]} – is achieved through extra external cesium ions to give the neutral self‐complementary building blocks [{Cs⊂[(Δ,Δ)/(Λ,Λ)‐Mg 2 (L 1 ) 3 ]}Cs], which aggregate end‐on across the external cesium ions to give the homochiral one‐dimensional strings [{Cs⊂[(Δ,Δ)‐Mg 2 (L 1 ) 3 ]}Cs] n [Δ‐( 2 ) n ] and [{Cs⊂[(Λ,Λ)‐Mg 2 (L 1 ) 3 ]}Cs] n [Λ‐( 2 ) n ], which are packed in the crystal in alternating homochiral layers. However, reaction of bulkier phenyl‐substituted bis(1,3‐diketone) H 2 L 2 instead of methyl‐substituted H 2 L 1 with cesium or rubidium acetate and magnesium, cobalt or zinc acetate yielded the meandering polymer meso ‐{[({M 1 ⊂[(Δ,Δ)‐M 2 2 (L 2 ) 3 ]}M 1 end )({M 1 ⊂[(Λ,Λ)‐M 2 2 (L 2 ) 3 ]}M 1 side )][({M 1 ⊂[(Λ,Λ)‐M 2 2 (L 2 ) 3 ]}M 1 end )({M 1 ⊂[(Δ,Δ)‐M 2 2 (L 2 ) 3 ]}M 1 side )]} n [ meso ‐( 3 ) n ] (M 1 = Cs + , Rb + ; M 2 = Mg 2+ , Co 2+ , Zn 2+ ). In this case, the {2}‐metallacryptates {M 1 ⊂[(Δ,Δ/Λ,Λ)‐M 2 2 (L 2 ) 3 ]} – are linked by only one cesium ion end‐on to give the fragments meso ‐[({M 1 ⊂[(Δ,Δ)‐M 2 2 (L 2 ) 3 ]}M 1 end )({M 1 ⊂[(Λ,Λ)‐M 2 2 (L 2 ) 3 ]}M 1 side )], which are connected by the second cesium ions side‐on. The one‐dimensional meander strands of isostructural meso ‐( 3 ) n are packed in the crystal in parallel. Reaction of 4 equiv. of zinc acetate and 1 equiv. of cesium or rubidium acetate with 2 equiv. of H 2 L 2 afforded the {M 1 ⊂[Zn 2 (L 2 ) 2 OAc]} cryptates 4a , b (M 1 = Cs + , Rb + ). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)