Synthesis and structural variations of mixed, hydronium, ammonium salts of indium carboxylates

Abstract

The reaction of indium bis(trimethylsilyl)amide with a series of sterically varied carboxylic acids in toluene followed by the addition of methanol led to the isolation of a series of hydronium-ammonium indium carboxylates (([H3O] x [NH4] y )In(ORc) z ). These derivatives were structurally characterized as 3([H3O]0.20[NH4]0.80)[In(OFc)6] (1), ([H3O]0.45[NH4]0.55)[In(OAc)4] (2), ([H3O]0.35[NH4]0.65)[In(OBc)4]·3H-OBc (3) and ([H3O]0.70[NH4]0.30)[In(ONc)4]·2H-ONc (4), where OFc = O2CH, OAc = O2CCH3, OPc = O2CCH(CH3)2, OBc = O2CC(CH3)3, ONc = O2CCH2C(CH3)3 and py = pyridine. For 1, an octahedral arrangement of six OFc ligands coordinated to the In metal center was solved, with three counter cations located in the lattice to balance the charge. Based on population refinements that yielded values larger than unity for NH4 + only, a mixed [H3O]:[NH4] cation ratio was proposed, evaluated, and found to yield a better structure for 1 with an approximate 20:80 ratio. For 2–4, the distorted dodecahedral metal centers are chelated by four ORc moieties and charge balanced by a single, mixed [H3O]:[NH4] cation (see formulas above for ratios) in the lattice. For 3 and 4, H-ORc ligands were also located in the lattice with extensive H-bonding to the parent molecule. The OPc derivatives were only isolable in the presence of pyridine forming crystals of [In(OPc)3]·NH3 (5) and [In(k 2-OPc)2(µ-OPc)(py)]n (5a).