Synthesis and molecular structure of the trinuclear mixed-metal complex [{(Me2NCH2CH2CH2) 2Cr(?-Cl)2}2Mg] and of the tetranuclear Grignard reagent [(Me2NCH2CH2CH2)Mg 2Cl3(THF)2]2

CrCl3·3THF reacts with [(Me2NCH2CH2-CH2)Mg 2Cl3(THF)2]2 (1) in THF at room temperature to form the complex [{(Me2NCH2CH2CH2) 2Cr(?Cl)2}2Mg] (2). The solid-state structures of 1 and 2 have been determined by X-ray crystal analysis. 1 is triclinic, space group P1 (No. 2), with a = 10.035(8) Å, b = 10.393(8) Å, c = 10.707(8) Å, ? = 75.59(6)°, ? = 68.61(6)°, ? = 75.28-(7)°, and Z = 1 (the asymmetric unit is half of the molecule); the structure was refined to a conventional R factor of 0.079. In this tetranuclear Grignard reagent 1 Mg and Cl atoms form a system of five four-membered bridging units, where the Mg atoms exhibit five and six coordination and are connected by doubly (?) or triply (?3) bridging chloro ligands. 2 is triclinic, space group P1 (No. 2), with a = 8.514(8) Å, b = 12.471(9) Å, c = 14.976(9) Å, ? = 81.54(5)°, ? = 92.52(6)°, ? = 95.32(6)°, and Z = 2; the structure was refined to R = 0.064. 2 is a trinuclear complex with two (Me2NCH2CH2CH2)Cr-(?-Cl) 2 fragments attached either side of a central Mg atom through four Cr-Cl-Mg bridges.