Structural studies of bridged lanthanide(III) complexes. Diaquotri(nicotinic acid)holmium(III) hexa(isothiocyanato)chromate(III) dihydrate and diaquotris(isonicotinato)lanthanum(III)

Abstract

The structures of the crystalline neutral complex of the isonicotinate ion with lanthanum(III) and of the crystalline salt of the cationic complex of nicotinic acid with holmium(III) have been determined by three-dimensional X-ray diffraction techniques. The complexes crystallize in P2l/c. The crystal parameters for Ho(C5H4NCOOH)3(H20)2Cr(NCS)6-2H20 are a = 9.578 (5) A, b = 25.954 (13) Á, c = 15.784 (7) Á, ß = 108.48 (2)°, deM = 1.797, dmtmi = 1.78 (2) g/cm3. The conventional discrepancy factor for this structure is 0.048 for 2989 diffractometer data. The crystal parameters for La-(C5H4NC00)3(H20)2 are a = 9.744 (3) Á, b = 19.908 (9) Á, c = 11.607 (4) A, ß = 68.20 (2)°, ¿caicd = 1.72, dmeasd = 1.70 (2) g/cm3. The discrepancy factor for this structure is 0.038 for 2554 diffractometer data. The primary structural units in both compounds are polymer chains made up of lanthanide(III) ions alternately linked by four and two bridging carboxylate groups. The eight coordination about each metal is completed by two water molecules. In the add complex, two additional waters and one hexaisothiocyanatochromate ion are also present. The acid ligand appears to be present as a zwitterion with the hydrogen attached to the nitrogen. These linear polymeric structures are compared with the dimeric structures found in the complexes of the rare earth metals with the nicotinate ion.Contribution prom the Department op Chemistry,

The Polymeric Structure of Aquacadmium Bisnicotinate

“…A number of hydrated metal nicotinate structures have been reported. In the case of lanthanide complexes (with La, Pr, Sm, Ho or Tm) these are dinuclear, with both chelating and bridging nicotinate ligands (Moore, Glick & Baker, 1972;Aslanov, Abdul'minev & Porai-Koshits, 1972;Prout, Matin & Hutchinson, 1985), except for a polymeric lanthanum complex containing only bridging nicotinates (Kay, Moore & Glick, 1972); the N atom of the ligand is not involved in binding to the metals. Complexes of Cr, Co and Zn are mononuclear, and involve binding only to the N atom, with no coordination by the carboxylate group (Cotton, Falvello, Ohlhausen, Murillo & Quesada, 1991;Anagnostopoulos, Drew & Walton, 1969).…”

New thallium(III) chloride complexes with pyridine carboxylic acids: from molecular compounds to supramolecular associations

“…A survey of the reported molecular structure determinations for metal complexes reveals that the O,Nmonometallic biconnective (bidentate) (Scheme 1, structures I and II) is the most usual coordination pattern for the deprotonated form of the picolinic (Hpic) and 3-hydroxypicolinic (H3hpic) acids [1,2,3,4]. Nicotinic (Hnic) and isonicotinic (Hinic) acids were found to coordinate: (i) as unidentate, neutral ligands only through the pyridyl nitrogen atom (Scheme 1, structures IIIa and IVa) [5,6], (ii ) as O,O-bimetallic biconnective (bridging) ligands (Scheme 1, structures IIIb and IVb) [7,8], and (iii ) as O,O; N -bimetallic triconnective (tridentate) groups (Scheme 1, structures IIIc and IVc) [9,10]. The presence of the carboxylate group as substituent in position 2 of the pyridine ring usually leads to O,N -monometallic biconnective (chelate) coordination, while substitution in position 3 or 4 promotes the formation of supramolecular associations through bridging ligands.…”

Synthesis and crystal structure of [Nd(C6NO2H5)3(H2O)2] n n[ZnCl4]·nCl·2.5nH2O with novel poly-cationic chain

“…1 (3) Cl (1) bidentate ligands to bridge two neighbouring neodymium atoms and the nitrogen atoms of the nicotinic acid ligands should be protonated, as the case found in many other references [17][18][19][20][21]. The neodymium atoms are alternately bridged by two or four 2 -nicotinic acid ligands in a 2-4-2 (the number indicates the number of the bridging nicotinic acid ligands) mode to construct a 1D chain with the Nd…Nd distances being ca.…”