Frank J. Iaconianni

Nicotinic and isonicotinic acid n-oxide interactions with 3d metal perchlorates[1]

Interactions of nicotinic or isonicotinic acid N-oxides (N-nicOH and N-inicOH, respectively) with 3d metal (II) perchlorates in ethanol-triethyl orthoformate lead, in most cases, to partial substitution of perchlorate with nicotinate (N-nicO) or isonicotinate(N-inicO) N-oxide anionic groups. These reactions led to the isolation of the following new metal complexes: Ni(N-inicOH)3(ClO4)2·3H2O: the only true adduct of the series, apparently polynuclear, with both unidentate terminal and bidentate bridging N-inicOH, bridging O2ClO2 ligands, ionic ClO4− and lattice water. Complexes with exclusively anionic ligands of the type (ClO4) (MMn, Cu for LN-nicO; MCu for LN-inicO), with both terminal and bridging L, ionic and unidentate coordinated perchlorate, and aqua ligands. The rest of the complexes are of the mixed ligand type, i.e.: [H2O)2(O3ClO)M(N-nic)2M(N-nicOH)(OH2)2] (ClO4) (MCo, Ni), with bridging N-nicO, terminal N-nicOH,-OClO3 and aqua ligands, and ionic ClO4−; M4(N-inicOH) (N-inicO)5 (ClO4)3. 4H2O (MMn, Co, Zn), polynuclear with exclusively bridging organic ligands, terminal aqua and bidentate perchlorato groups, and ionic ClO4−; and, Zn4(N-nicOH)N-nicO)5(ClO4)3. 10H2O, probably tetrameric, with four bridging and one terminal N-nicO groups, and terminal N-nicOH, aqua and =O2ClO2 ligands, as well as ionic ClO4−. With the exception of the latter complex, which is hexacoordinated, the new metal complexes appear to be pentacoordinated. The likely structural types proposed for these compounds were based on the overall spectral and magnetic evidence obtained.

Characterization studies of adenine complexes with 3d metal perchlorates

A series of adenine (LH) complexes with 3d metal perchlorates were prepared by refluxing solutions of the metal salts in ethanol-triethyl orthoformate with the ligand for 2–5 days. Our studies indicate that, depending on the ligand to metal molar ratio employed and the duration of the refluxing step, complexes with either neutral LH or anionic L− can be obtained. Among the new complexes, Cu(LH)2(ClO4)2·C2H5OH appears to be of the familiar dimeric type with quadruple bridges of N(3), N(9)-bonded LH, one terminal -OClO3 ligand per Cu2+ ion and lattice ethanol (μeff = 1.66 μB at 298K.). The Fe3+ complex (μeff = 2.39 μB) seems to be also a dimer of the [(O2ClO2)(LH)2FeL2Fe(LH)2(O2ClO2)] type, with N(9)-bonded terminal and N(y), N(9)-bonded (y = 1, 3 or 7) bridging adenine. A similar type of bridging (N(y), N(9)-bonded) adenine is also present in the probably double-bridged dimeric FeL(ClO4)·C2H5OH·2H2O complex (μeff = 4.86 μB), and a number of presumably linear, single-bridged polymers of the M(LH)2(ClO4)2·χC2H5OH (x=2 for M = Mn; x=3 for M = Co) and ZnL(ClO4)·C2H5OH·3H2O types. However, the two remaining complexes of the ML(ClO4)·C2H5OH·2H2O (M = Co, Ni) type, involve adenine apparently coordinated through the NH2 nitrogen. For these compounds, linear polymeric single-bridged structures with N(6), N(z)-bonded (z is most probably 9) bridging L, were considered as likely. The ambient temperature magnetic moments of the complexes considered as linear polymers range from slightly below normal to normal, but it is anticipated that studies at 300-80K. will reveal magnetic exchange interactions in general, in view of the established spin-spin coupling in the corresponding purine complexes.

Purine complexes with divalent 3d metal chlorides

Abstract A series of purine (puH) complexes with 3d metal(II) chlorides were prepared by interaction of ligand and metal salt in ethanoltriethyl orthoformate. 1:1 complexes of the general type M(puH)Cl 2 ·nH 2 O (n = O for M = Zn; n = 1 for M = Fe, Co, Cu; n = 2 for M = Mn, Ni) were isolated. Spectral evidence favors a tetrahedral configuration for Zn(puH)Cl 2 , and coordination numbers five for M(puH)Cl 2 ·H 2 O (M = Fe, Co, Cu) and six for M(puH)Cl 2 ·2H 2 O (M = Mn, Ni). The new paramagnetic metal ion complexes are characterized by normal ambient temperature magnetic moments for high-spin 3d 5 –3d 8 compounds or the 3d 9 configuration. A linear oligomeric structural type, involving single-bridged MpuHMpuHsequences and exclusively terminal chloro, and wherever applicable, aqua ligands was considered as most likely for the new complexes. Probable bonding sites of the bidentate bridging puH ligands are the N(3) and N(9) nitrogens.

Adennine N(1)-oxide complexes with first row transition metal perchlorates

Abstract A series fo adenine N(1)-oxide (LH) complexes with 3d metal perchlorates were prepared by refluxing mixtures of ligand and salt in ethanol-triethyl orthoformate. Charaterization studies revealed significant differences in ligand binding sites and probable complex structural types, with metal ion variation. Thus, [Cr(LH)2(OClO3)2(EtOH)2(ClO4) and [M(LH)2(OClO3)(EtOH)2](ClO4) (M = Mn, Zn) seem to be monomeric with unidentate, imidazole nitrogen-bonded (most porbably N(7) LH, while the Co2+ analogue of the latter two complexes is apparently a linear polymer, with single bridges of bidentate O(1), N(7)-bonded LH, as well as terminal unidentate imidazole introgen-bonded ligand groups. The rest of the complexes involve both neutral LH and anionic L− ligands. The subnormal room temperature magnetic moment of the Cu2+ complex (1.68 μB) favours a triple ligand-briged structure of the [(O3ClO)Cu(LH)L2Cu(OClO3)] type, with O(1), N(7)-bonded bridging ligands. Ni(LH)L(ClO4)·2EtOH and Fe(LH)2L(ClO4)2 were considered as linear polymers, with single bridges of O(1) N(7)-bonded adenine N(1)-oxide ligands; the rest of the ligands present seem to be terminal, unidentate imidazole nitroten-bonded for M = Ni2+ and bidentate chelating, O(1), N(6)-bonded for M = Fe3+.

Picolinic acid N-oxide interactions with 3d metal perchlorates [1]

Abstract Interactions of picolinci acid N-oxide(LH) with 3d metal perchlorated in ethanol-triethyl orthoformate lead to the partial or complete substitution of perchlorate with anionic picolinate N-oxide(L) groups. Complexes of the following types were isolated and characterized: [ML(LH)(OH 2 ) 2 ](ClO 4 ) (M = Mn, Zn), with both L and LH functioning as bidentate chelating O,O-ligands, coordinating through the NO and one of the COO oxygens; [CrL 2 (LH)(OH 2 )] (ClO 4 )·4H 2 O, [FeL(LH) 2 (OH 2 ) 2 ](ClO 4 )·2H 2 O, [ML(LH)(OH 2 ) 3 ](ClO 4 ·H 2 O (M = Co, Ni; x = 0 for M = Co; x = 2 for M = Ni), with bidentate chelating L and unidentate NO oxygen-bonded LH ligands; [FeL 2 (OH 2 ) 3 ](ClO 4 )·H 2 O, with one bidentate chelating and one unidentate NO oxygen-bonded L ligand (all the preceding new complexes are low symmetry hexacoordinated); and the previously reported square-planar [CuL 2 ] bis-chelate.

Metal(II) methylphenylphosphinates

Abstract A series of methylphenylphosphinate (mpp; [OP(CH 3 )(C 6 H 5 )O] − complexes with M 2+ ions (Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn, Cd, Sn) were prepared by reaction of the appropriate metal chlorides with a large excess of methyl methylphenylphosphinate ([(CH 3 O)C 6 H 5 (CH 3 )PO]) at elevated temperatures. The overall properties of the new complexes, and especially the subnormal ambient temperature magnetic moments of most of the paramagnetic M(mpp) 2 compounds, favor polymeric structures, involving bidentate bridging mpp O,O-ligands. A number of M(mpp) 2 complexes (M  Mg, Ca, Co, Ni, Cu, Zn, Cd, Sn) are tetracoordinated linear chainlike polymers of the [-M(mpp) 2 -] x or [-M(mpp) 3 M(mpp)-] x type; [Ca(mpp) 2 ·2H 2 O is of the same type, containing exclusively lattice water. For M(mpp) 2 (M  Mn, Fe), which are obviously hexacoordinated, highly cross-linked polymeric structures are proposed. Finally, Ni(mpp) 2 (OH 2 ) 2 is also hexacoordinated and apparently a linear chainlike polymer, involving two aqua ligands per Ni 2+ ion.

Characterization of polymeric metal complexes formed by reaction of excess diethyl acetyl- or diethyl benzoyl-phosphonate with metal chlorides at elevated temperatures

Abstract Reactions of some metal chlorides with diethyl acetyl- or diethyl benzoyl-phosphonate at elevated temperatures lead to products of varying types, i.e. Al(eap) 3 , M(ebp) 3 (M = Al, Cr), V(ehp) 3 , M(ehp) 4 (M = Th, U) (eap: ethyl acetylphosphonate; ebp: ethyl benzoylphosphonate; ehp: ethyl hydrogenphosphonate), as well as several mixed ligand complexes of the Ti(eap) 2 (ehp), M(eap)(ehp) 2 (M = Dy, Cr, Fe), M(ebp) 2 (ehp) (M = Dy, Ti, V, Fe) and U(ebp) 3 (ehp). Characterization studies suggest that the new metal complexes are linear chainlike polymers, involving triple- or quadruple-bridges of the anionic phosphonate ligands between adjacent metal ions. Among the ligands under study, ehp acts as bidentate bridging, coordinating through its two POO oxygens. In the cases of eap and ebp complexes, two different fashions of bridging were established. In most occasions, these ligands act as bidentate bridging, coordinating through the CO and one of the POO oxygens, but in a few cases, bridging through the two POO oxygens occurs instead.

2-benzylpyridine N-oxide complexes with transition metal perchlorates[1]

Abstract 3 d metal perchlorate complexes with 2-benzylpyridine N-oxide(L) were prepared and characterized by means of spectral, magnetic and conductance studies. Interaction of ligand and salt in ethanol-triethyl orthoformate at a 4:1 or a 6:1 molar ratio led to the formation of the following complexes: M 2+ perchlorates yielded solid complexes of the types [ML 5 ](ClO 4 ) 2 (M = Mn, Fe, Co, Ni, Zn) and [CuL 4 ](ClO 4 ) 2 , regardless of the ligand to metal ratio employed. Cr 3+ and Fe 3+ perchlorates formed oily or gummy precipitates, at the 4:1 L to salt ratio; although these products were not sufficiently pure for characterization studies, it was established that they involve between four and five L molecules per metal ion (analytical results). A complex of the type [FeL 6 ](ClO 4 ) 3 was obtained in small yields, when L and Fe(ClO 4 ) 3 were allowed to interact at a 6:1 molar ratio. The benzyl substituent of the ligand obviously introduces significant steric hindrance during coordination, as demonstrated by the fact that 5:1 complexes of L with M 2+ (M = Mn, Fe, Co, Ni, Zn) perchlorates are readily obtained, whilst Cr 3+ and Fe 3+ perchlorates also yield complex species clearly involving L to M 3+ ratios of less than six; furthermore, the isolation of a 6:1 L to Fe 3+ cationic complex is difficult, as suggested by poor yields.

3-Methylisoquinoline N-oxide complexes with 3d metal perchlorates [1]

Abstract The methyl substituent in 3-methylisoquinoline N-oxide (L) exerts significant steric hindrance as to stabilize complexes involving L to metal ratios of less than six with 3d metal(II) perchlorates, as follows: [ML 5 (OClO 3 )](ClO 4 ) (M = Mn, Ni); [CoL 5 (OClO 3 )](ClO 4 )· H 2 O; [ML 4 (OClO 3 )](ClO 4 ) (M = Fe, Cu); and [ZnL 3 (OClO 3 )](ClO 4 )· 3H 2 O (tetrahedral). In the case of Cr 3+ and Fe 3+ perchlorates, complexes of the [ML 6 ](ClO 4 ) 3 type have been isolated; however, [CrL 4 (OClO 3 )(OH 2 )](ClO 4 ) 2 ,[FeL 4 (OClO 3 ) 2 ](ClO 4 ) and [FeL 3 (OClO 3 (OH 2 ) 2 ](ClO 4 ) complexes can be also stabilized, under the influence of the steric affects of L. Finally, during interaction of L with Fe(ClO 4 ) 3 , a mixture of approximately 9 parts of the perchloric acid adduct of L([L 2 H](ClO 4 )) and 1 part of [FeL 6 ](ClO 4 ) 3 was recovered from the filtrate, after separation of the precipitate of the latter complex.

Transition metal perchlorate complexes with 4-phenylpyridine N-oxide[1]

Abstract The bulky p -phenyl substituent in 4-phenylpyridine N-oxide(L) was shown to exert some steric influence during complex formation between this ligand and 3 d metal perchlorates. The steric hindrance introduced by L is not sufficiently severe as to impede the formation of [ML 6 ] n + cationic species. However, it is significant enough as to cause the stabilization of 4:1 or 5:1 complexes of L with M(ClO 4 ) n ( n = 2 or 3) in certain cases. These effects were best illustrated by the fact that, by variation of the synthetic conditions, three different solid Fe(ClO 4 ) 2 complexes with L were obtained, namely: [FeL 6 ](ClO 4 ) 2 and [FeL 5 (OClO 3 )](ClO 4 ). In the rest of the cases investigated, a single solid complex could be isolated with each metal perchlorate. These complexes are of the following types: [ML 6 ](ClO 4 ) 2 (MCo, Ni); [ML 5 (OClO 3 )](ClO 4 ) 2 (MCr, Fe); [ZnL 5 (OClO 3 )](ClO 4 ); [MnL 4 (OClO 3 )](ClO 4 ); and [CuL 4 ](ClO 4 ) 2 . The preceding formulations of the new metal complexes were based on spectral, magnetic and conductance studies.