Synthesis and crystal structure of uranium(IV) complexes with calix[n]arenes (n = 4, 6 and 8): mononuclear, polynuclear and 1D polymeric species

Reactions of UCl₄ with calix[n]arenes (n = 4, 6) in THF gave the mononuclear [UCl₂(calix[4]arene − 2H)(THF)₂]·2THF (1·2THF) and the bis-dinuclear [U₂Cl₂(calix[6]arene − 6H)(THF)₃]₂·6THF (2·6THF) complexes, respectively, while the mono-, di- and trinuclear compounds [Hpy]₂[UCl₃(calix[4]arene − 3H)]·py (4·py), [Hpy]₄[U₂Cl₆(calix[6]arene − 6H)]·3py (5·3py), [Hpy]₃[U₂Cl₅(calix[6]arene − 6H)(py)]·py (6·py) and [Hpy]₆[U₃Cl₁₁(calix[8]arene − 7H)]·3py (3·3py) were obtained by treatment of UCl₄ with calix[n]arenes (n = 4, 6, 8) in pyridine. The sodium salt of calix[8]arene reacted with UCl₄ to give the pentanuclear complex [U{U₂Cl₃(calix[8]arene − 7H)(py)₅}₂]·8py (7·8py). Reaction of U(acac)₄ (acac = MeCOCHCOMe) with calix[4]arene in pyridine afforded the mononuclear complex [U(acac)₂(calix[4]arene − 2H)]·4py (8·4py) and its treatment with the sodium salt of calix[8]arene led to the formation of the 1D polymer [U₂(acac)₆(calix[8]arene − 6H)(py)₄Na₄]_n (9). The sandwich complex [Hpy]₂[U(calix[4]arene − 3H)₂][OTf]·4py (10·4py) was obtained by treatment of U(OTf)₄ (OTf = OSO₂CF₃) with calix[4]arene in pyridine. All the complexes have been characterized by X-ray diffraction analysis.