A New Family of Trinuclear Complexes (CH 3 ) 4 N[M 3 (µ 3 -F)(TFA) 6 (py) 3 ] (M = Mn, Co, Ni, Cu, Zn): Synthesis, Crystal Structure, and Thermal Stability

Trinuclear complexes Me 4 N[Ni 3 (µ 3 -F)(TFA) 6 (MeOH) 2 (H 2 O)] ( 1 ) and Me 4 N[M 3 (μ 3 -F)(TFA) 6 (py) 3 ] (M = Mn ( 2 ), Co ( 3 ), Ni ( 4 ), Cu ( 5 ), Zn ( 6 )) have been synthesized by crystallization from methanol solutions. Single-crystal X-ray diffraction shows that compounds 1 – 6 are composed of tetramethylammonium cations Me 4 N + and trinuclear triangular anions [Ni 3 (µ 3 -F)(TFA) 6 (MeOH) 2 (H 2 O)] – ( 1 ) or [M 3 (μ 3 -F)(TFA) 6 (py) 3 ] – ( 2 – 6 ) centered by the μ 3 -F atom. The bridging trifluoroacetate anions (TFA – ) located along the triangle edges link pairs of M 2+ cations, and the axial positions are occupied by MeOH, H 2 O, or pyridine (py) molecules. In 2 , the pyridine molecules are nearly coplanar with the [M 3 F] triangle, while in the other structures they are turned almost perpendicularly. The different orientations of py molecules lead to different packing motifs: columns of alternating trinuclear anions and Me 4 N + cations are formed in 2 , while in 3 – 6 anions and cations form neutral layers. A significant role in the organization of structures 1 – 6 is played by non-covalent interactions, such as hydrogen bonds and stacking and CH···π interactions. Heating complexes 2 – 4 above 200°С turns out to lead to a stepwise thermal decomposition, which begins with the elimination of py and ends with the formation of d -metal fluoride above 300°С.