Synthesis, Structures and Dynamic Properties of Trimethylene- And Tetramethylene-Bis(CIS-Stilbene-1,2-Dithiolato)Nickel(II)

Abstract

The unusual, structurally dynamic behaviour of the Ni(II) dialkyldithiolene Ni[(CH₃)₂S₄Ph₄], 1, in solution prompted a study of the related macrocyclic complexes, Ni[(CH₂)₃S₄C₄Ph₄], 2, and Ni[(CH₂)₄S₄C₄Ph₄], 3, whose synthesis, structures and dynamic properties in solution are described. Complex 2, isolated as a CHCl₃ inclusion compound, crystallizes in space group C2/c with 8 molecules per unit cell, a=29.26(2), b = 8.170(4), c = 30.76(2)Å, β = 116.69(6)[ddot]. The complex has the cis-syn configuration with respect to the Ni-S(CH₂)- bonds and the coordination geometry of Ni is essentially square planar, with mean Ni-S and Ni-S(CH₂) bond lengths of 2.174(4) and 2.162(5)Å, respectively. Complex 3 crystallizes in space group P2₁/n, with 4 molecules per unit cell, a=10.07(1), b=18.22(2) Å, c=15.36(2) Å, β = 94.56(8)[ddot], and the Ni-S(CH₂)- bonds are in the cis-anti-configuration. The mean Ni-S-and Ni-S(CH₂) bond lengths are 2.156(5) and 2.153(9) Å, respectively. The coordination geometry of Ni is slightly tetrahedrally distorted from planar, with bond angles S-Ni-S of 87.6(1)[ddot], (CH₂)S-Ni-S(CH₂), 97.7(1)[ddot] and the mean of S-Ni-S(CH₂) bond angles 162(2)[ddot]. The ¹H NMR spectrum of 2 in CD₂Cl₂ shows the presence only of the one isomer and is temperature independent between—50[ddot] and + 50[ddot]C. The ¹H NMR spectrum of 3 is temperature dependent due to dynamic equilibrium between the cis-anti- and cis-syn-isomers.

Key Words:

• Trimethylene-bis(cis-stilbene-1,2-dithiolato)nickel(II)
• tetramethylene-bis(cis-stilbene-1,2-dithiolato)nickel(II)
• dithiolene complexes
• dialkyldithiolene complexes
• X-ray structures