Manipulation of Molecular and Supramolecular Structure in Nickel(II) Complexes through the Orientation of Dicarboxylate Hydrogen Bonding Faces

The reactions of the bis(thiosemicarbazide)nickel(II) nitrates [NiL2](NO3)2 [1a, L = tsc, NH2C(S)NHNH2; 1b, L = Metsc, MeNHC(S)NHNH2; 1c, L = Ettsc, EtNHC(S)NHNH2; 1d, L = Me2tsc, NH2C(S)NHNMe2;
and 1e, L = Me3tsc, MeNHC(S)NHNMe2] with a range of sodium dicarboxylates led to crystalline products in 19
cases. The reaction with dicarboxylates containing an angle θ of 180° between the carboxylate groups generally led
to compounds in which the cations and anions are linked into tapes through hydrogen bonding, and the crystal
structures of [Ni(tsc)2(OH2)2][fumarate] (2), [Ni(Me2tsc)2(OH2)2][fumarate]·H2O (3), [Ni(Me3tsc)2(OH2)2][fumarate]
(4), and [Ni(tsc)2][4,4‘-biphenyldicarboxylate]·5H2O (5) are reported. A similar tape structure is observed in the
crystal structure of [Ni(Me3tsc)2(OH2)2][isophthalate]·3.2H2O (6) in which the isophthalate anion has an angle θ of
120° between the carboxylate groups. However, such tape structures are not seen with dicarboxylates in which θ is
less than 90°, and instead, one of three structural types is observed. These are tris(thiosemicarbazide)nickel(II)
dicarboxylates, witnessed by the crystal structures of [Ni(tsc)3][maleate]·H2O (7) and [Ni(Ettsc)3][phthalate]·4H2O
(8), neutral compounds containing coordinated dicarboxylates, epitomized by the crystal structures of [Ni(Me3tsc)2(phthalate)]·2H2O (9), [Ni(Me2tsc)2(itaconate)]·6H2O (10), and [Ni(Me3tsc)2(homophthalate)]·4H2O (11) and neutral
bis(thiosemicarbazidato)nickel(II) complexes in which the dicarboxylate has acted as a base. Thermogravimetric
analyses for the hydrogen-bonded tape structures 2−6 and the coordinated dicarboxylate compounds 9−11 are
reported.