Salah S. Massoud

Three new dinuclear copper(II) complexes with [Cu(μ1,3-N3)2Cu]2+ and [Cu(μ1,1-N3)2Cu]2+ asymmetrical cores: syntheses, structures and magnetic behaviour

Three new dinuclear copper(II) complexes, derived from end-to-end and end-on azido bridging ligands and triamine derivatives, have been synthesized and their crystal structures have been determined by X-ray diffraction methods. These are the dinuclear end-to-end compounds, [Cu2(μ1,3-N3)2(Et3dien)2](ClO4)2 (1) and [Cu2(μ1,3-N3)2(Medpt)2](ClO4)2 (2), and the dinuclear end-on compound [Cu2(μ1,1-N3)2(Medien)2](ClO4)2 (3) (Et3dien is triethyldiethylenetriamine, Medpt is methyldipropylenetriamine and Medien is methyldiethylenetriamine). The [Cu(μ-N3)2Cu]2+ cores are asymmetrical in all 3 compounds. Variable temperature magnetic susceptibility data were collected and fitted to the appropriate equation derived from the Hamiltonian H = −JS1S2. 1 shows unusual ferromagnetic interactions with J = 9 cm−1 through the end-to-end azido bridges while 2 shows an antiferromagnetic interaction through the end-to-end azido bridges with the highest reported absolute magnitude of J = −105 cm−1. The magnetic data of 1 and 2 have been correlated with the Addison parameter, τ, and mainly with the Cu–N3–Cu torsion angle, Δ. 3 shows an unusual antiferromagnetic interaction with J = −16.8 cm−1 through the end-on azido bridges.

Synthesis and characterization of binuclear and polymeric five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn): Crystal structure of [Cu(trpn)(N3)]ClO4 (I) and [Cu2(trpn)(tren)(NO2)(H2O)](ClO4)3 (II)

Abstract The synthesis and characterization of five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn) are described. The X-ray diffraction studies have established the structures [Cu(trpn)(N3)]ClO4 (I) and [Cu2(trpn)(tren)(NO2)(H2O)](ClO4)3 (II). Compound (I) consists of a polymeric cation chain and ClO4− counter ions. The coordination geometry of the Cu(II) centers may be described as distorted square pyramidal (SP) with the azido group at the apical site and three nitrogen donors of the trpn molecule occupy the basal sites. The CuN5 chromophore is completed by a bridging aminopropyl group of neighboring trpn ligand. Compound (II) is a dinuclear complex cation with two different cation geometries in the unit cell. The geometry of the Cu(II) binding tren ligand is close to trigonal bipyramidal (TBP), with the basal and apical sites are occupied by the four nitrogen atoms of the tren ligand. The fifth coordination site is bridged to one of the aminopropyl arms of the trpn ligand. The geometry of the second Cu(II) center may be described as close to distorted SP, where the trpn ligand is binding the Cu(II) ion via the two primary aminopropyl groups and the tertiary nitrogen. The remaining two sites are occupied by oxygen atoms of a water molecule and nitrite ion. The intramolecular Cu…Cu distance in I and II ranges from 7.55 A to 7.94 A. The visible spectra of the complexes in DMSO are consistent with the X-ray results found for I and II and show a greater tendency toward SP geometry.

Squarato-metal(II) complexes. 2. unusual bonding mode for a squarato-bridged trinuclear copper(II) complex.

Herein, we report the structural characterization and magnetic properties of the unique squarato-bridged-tricopper(II) complex, [Cu3(pmap)3(micro1,2,3-C4O4)](ClO4)(4).2H 2O (1), based on the tripod tripyridylamine ligand bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine (pmap). Each of the three copper centers is penta-coordinated by four N atoms of a pmap ligand and one bridging O atom of the central squarato dianion. This complex is the first example of a non-polymeric X-ray structurally characterized trimeric transition metal complex with the three metal cations being bridged by a single squarato ligand in a micro1,2,3 coordination mode. The magnetic properties of the complex were measured over the temperature range 2-300 K. The complex exhibits moderate bulk antiferromagnetic interaction. The three magnetic exchange pathways have J values of -27.8, -20.8, and -31.9 cm(-1). The DFT calculations corroborate the relatively strong antiferromagnetic couplings obtained from the fitting of the experimental magnetic susceptibility data and allow an assignment of the fitted J values. Several geometrical parameters have been analyzed using theoretical calculations to establish magnetostructural correlations for complex 1.

Azido-amine-cobalt(III) complexes

Abstract The structures of the two complexes cis-[Co(tren)(N3)2]ClO4 (I) and trans-[Co(3,2,3-tet)(N3)2]ClO4 (II) (tren=2,2′,2″-triaminotriethylamine; 3,2,3-tet=1,10-diamino-4,7-diazadecane) have been determined by X-ray crystallography. The compounds consist of isolated complex cations [Co(tren)(N3)2]+ and [Co(3,2,3-tet)(N3)2]+ with distorted octahedral geometry and ClO4− counter ions. The two single coordinated azido ligands are arranged cis and trans in the cations of I and II, respectively. The Co–N(azido) distances vary from 1.946(3) to 1.964(3) A. The configurational geometry for these complexes were previously reported based on the position of the asymmetric stretching mode of vibration of the coordinated azido ligands, νa(N3) in the 2000–2065 cm−1 region. The results of X-ray studies are consistent with the previous assigned geometry based on the IR of νa(N3) and strongly support its use as a valuable tool for elucidating the geometrical isomerism in octahedral diazido metal complexes.

Spectroscopic characterization for the geometrical isomers of azido-amine-cobalt(III) complexes

Abstract A series of pseudo octahedral monoazido-, diazido- and triazido-amine-cobalt(III) complexes was synthesized. The IR spectra for the CH2 rocking in the range 800–900 cm−1 was used to distinguish between the geometrical configuration of the complexes. The asymmetric stretching mode of vibration of the coordinated azide, νa(N3) in the range 2000–2065 cm−1 was employed to confirm the previous prediction ; the cis-diazido and fac-triazido species exhibit two strong absorption bands, whereas their corresponding trans and mer complexes show only one band. The 13C NMR spectra of the complexes in (CD3)SO were in complete agreement with the assigned geometry. The UV-vis spectra of the synthesized compounds are also reported.

THE PHENOMENON OF KRYPTORACEMIC CRYSTALLIZATION. PART 1. COUNTERION CONTROL OF CRYSTALLIZATION PATHWAY SELECTION. PART 4. THE CRYSTALLIZATION BEHAVIOR OF (+/−)-[Co(tren)(NO2)2]Br(I), (+/−)-[Co(tren)(NO2)2]2Br(ClO4) · H2O(II), (+/(−)-[Co(tren)(NO2)2]ClO4(III) AND ATTEMPTS TO SOLVE THE STRUCTURE OF (+/−)-[Co(tren)(NO2)2]NO3(IV)

Abstract Racemic aqueous solutions of (+/−)-[Co(tren)(NO2)2]Br (I), (+/−)-[Co(tren)(NO2)2]ClO4 (III) and [Co(tren)(NO2)2]NO3(IV) crystallize as racemates. By contrast, the double salt, (+/−)-[Co(tren)(NO2)2]2Br(ClO4) · H2O(II), produces kryptoracemic crystals belonging to the enantiomorphic space group P212121 (No. 19). The former three species crystallize with one molecule in the asymmetric unit; in the latter, a racemic pair is the asymmetric unit, a fact which is hidden by the enantiomorphic nature of its space group – thus the name of the crystallization phenomenon reported. In (II) pairs of cations are related by an approximate, non-crystallographic, inversion center. The crystal structure and polarity of (I) and the absolute configuration of (II) were determined by refinement. The crystalline contents of (I) to (III) consist of infinite strings of hydrogen bonded cations, the counter ions and (where relevant) waters of crystallization acting as a hydrogen-bonding glue linking the spiral strings In (...

THE PHENOMENON OF CONGLOMERATE CRYSTALLIZATION. XXVII. THE EFFECT OF CHARGE COMPENSATING ANION ON THE CRYSTALLIZATION BEHAVIOUR OF [Co(en)2ox]-Cl·4H2O, [Co(en)2ox]Br·H2O, [Co(en)2ox]PF6 AND [Co(en)2ox]I

Abstract [Co(en)2ox]Cl·4H2O (I) and [Co(en)2ox]Br·H2O (II), crustallize from water at 21°C as conglomerates, space group P212121. Their structures and absolute configurations were determined by refinement of data using both enantiomeric configurations. [Co(en)2ox]PF6 (III) crystallizes as a racemate, space group P21/c. [Co(en)2ox]I (IV) crystallizes in both of the monoclinic space groups C2 and C2/c, in agreement with the phase diagram studies of Yamanari, et al. (see ref. 4). However, we have not been successful in crystallographic studies of this substance since in neither case was it possible to obtain ordered crystals. The conglomerate crystallization pathway selected by (I) and (II), and probably (IV), is shown to be the result of inter-cationic, three-point attachments reminiscent of that postulated as the origin of enzymatic chiral recognition. In this process, spiral strings are formed which resemble polypeptide helices, and which are stitched together by the counternions (and/or waters of crystal...

Adenosine 5′-triphosphate (ATP) hydrolysis promoted by aqua-amine-cobalt(III) complexes. Patterns of reactivity

Abstract The 1:1 complexes tn 2 CoATP − and trpnCoATP − , existing predominantly as the β, γ-chelates, were prepared in solution. The initial dephosphorylation rates for these preformed N 4 CoATP − chelates (1 mM) have been determined in the presence of added aqua-amine-cobalt(III) complexes N n Co III (aq) (N n = trpn, dpt, cyclen, tn 2 ) over the pH range 4–9 (25°C, I = 0.1 M (NaClO 4 ), [aqua complex = 1 mM). The effectiveness of these aqua-amine complexes in promoting ATP dephosphorylation (ATP → ADP + P i ) decreases in the order trpn > dpt ≥ cyclen > tn 2 , when the rates at the pH of maximum promotion are compared. An enhancement in the rate of ≈ 2 × 10 6 was estimated over the uncatalyzed ATP, hydrolysis when trpnCo III (aq) was added to tn 2 CoATP − or trpnCoATP − . The observed rates are highly sensitive to the identity of N 4 in the added aqua-amine-cobalt(III) complex, and relatively insensitive to the nature of the tetraamine in the preformed N 4 CoATP − . The rates of dephosphorylation of N 4 CoATP − maximize at pHs where the hydroxo-aqua species added predominate. The results also reflect the general requirement for OH − ion in the coordination sphere of the second cobalt for intramolecular nucleophilic attack at the adjacent phosphorus atom and PO bond cleavage, leading to the hydrolysis of ATP.

Spectroscopic investigation of cobalt(III) complexes of 1,10-diamino-4,7-diazadecane (3,2,3-tet)

Abstract A series of cis and trans octahedral cobalt(III) complexes of the general formula [Co(3,2,3-tet)XY] +/3+ have been synthesized, together with some other new members, where XY = Cl 2 , Br 2 , (NO 2 ) 2 , (N 3 ) 2 , (CN) 2 , (OCN) 2 , (SCN) 2 , (NH 3 ) 2 , (NO 2 )Cl, (NO 2 )Br, (NO 2 )SCN), (CH 3 COO) 2 , (C 6 H 5 COO) 2 , CO 3 2− , C 2 O 4 2− and en. The spectroscopic properties of these complexes are recorded. The IR and UV-vis spectra were employed to characterize the synthesized complexes and to confirm the cis -geometry for the carbonato, oxalato and ethylenediamine series, and the trans -geometry for the rest. In general the IR spectra for the CH 2 rocking in the 800-910 cm −1 region exhibit four weak absorption bands for the cis complexes and only two or three more intense bands for the trans complexes. The average ligand field strength Dq av for a number of quadridentate amines increases in the order; trpn

The preparation of [Cotn2PO4] and [CotrpnPO4] and kinetics of phosphato complex formation from the highly reactive [Cotn2(OH)(H2O)]2+ and [Cotrpn(OH)(H2O)]2+ cations

Abstract The complexes [Cotn 2 PO4]·2H 2 0 and [CotrpnPO 4 ]·5H 2 O have been prepared and characterized. The kinetics of the anation reactions of [Co(N 4 )(OH)(H 2 0)] 2+ by phosphate was studied for the two systems (N 4 )=tn 2 and trpn, at pH 6.5, 25 °C and μ=1.0 M. The results are consistent with S N l IP mechanism involving rapid preequilibrium ion-pair formation, followed by a slow substitution step. The reactivity of [Co(N 4 )(OH)H 2 0)] 2+ for phosphate complex formation decreases in the order trpn>tn 2 >en 2 .