ABSTRACT
A new series of heteroleptic complexes of cobalt were synthesized using aminoalkoxide and ß-diketonate ligands. The complexes, [Co(dmamp)(acac)]2 (3), [Co(dmamp)(tfac)]2 (4), [Co(dmamp)(hfac)]2 (5), [Co(dmamp)(tmhd)]2 (6), and [Co(dmamb)(tmhd)]2 (7), were prepared by two-step substitution reactions and studied using Fourier transform infrared spectroscopy, mass spectrometry, elemental analysis, and thermogravimetric analysis (TGA). Complexes 3-7 displayed dimeric molecular structures for all of the complexes with cobalt metal centers interconnected by µ2-O bonding by the alkoxy oxygen atom. TGA and a thermal study of the complexes displayed high volatilities and stabilities for complexes 6 and 7, with sublimation temperatures of 120 °C/0.5 Torr and 130 °C/0.5 Torr, respectively.
ABSTRACT
Heteroleptic complexes of strontium () were prepared by employing ß-diketonates and donor-functionalized alkoxides as coordinating ligands. The results illustrate the effect of alkoxide substituent groups on the overall structures of the complexes. The presence of a terminal methoxy group in the alkoxide ligands leads to the formation of trimeric complexes , whereas the substituents on the amine nitrogen prove to have less influence in determining the structure. The attempts to increase steric bulkiness of the aminoalkoxide ligands by introducing ethyl groups on the amine nitrogen and to the alkoxy carbon did not lead to a structural change from the dimeric form in but resulted in structurally interesting strontium complexes. In trimeric complexes , the three strontium atoms were held together by two µ3-O bonds using alkoxide oxygen atoms and two µ2-O bonds using a combination of alkoxide and ß-diketonate ligand oxygens. The strontium metal centers in these complexes exhibit seven-coordination states in and , whereas exhibits one six-coordinated and two seven-coordinated strontium metals in its structure. All of the complexes were characterized using FT-NMR, FT-IR, elemental analyses, and thermogravimetric (TG) analyses.
ABSTRACT
Novel heteroleptic magnesium complexes, [Mg(dmamp)(acac)]2 (), [Mg(dmamp)(tmhd)]2 (), [Mg(dmamp)(tfac)]2 (), and [Mg(dmamp)(hfac)]2 (), were successfully synthesized using dmamp and ß-diketonate as ligands. The thermogravimetric analyses and volatile studies of the complexes showed that the complexes and display high volatility and thermal stability. The single crystal X-ray study of the complexes reveals that both the complexes and were crystalized in the triclinic space group and as dimers, where magnesium atoms are in the pentacoordinate state with distorted trigonal bipyramidal geometry.
ABSTRACT
A series of heteroleptic strontium complexes (1-9) using a combination of different aminoalkoxides and 2,2,6,6-tetramethyl-3,5-heptanedionate (tmhd) were prepared to examine the effect of the bulkiness and coordination ability of the aminoalkoxide ligand in these complexes as well as potential strontium precursors. All complexes were characterized by FT-IR, FT-NMR, elemental analyses, and thermo-gravimetric (TG) analyses. The crystal structure analyses of 1, 2, 4, and 5 demonstrate their stability in the dimer form and the unwillingness of the strontium atom to form more than six coordination bonds in these complexes. The complex 5 shows an unusual picture: the existence of one hexa-coordinated and one penta-coordinated strontium atom side by side in its dimer structure. The introduction of ether groups as coordination sites in complexes 6-9 led to a decrease in steric hindrance which resulted in the formation of the complex 7 as a tetramer. The complex 7 shows a unique Sr4O4 cubane core where oxygen atoms undergo µ3-bridging between strontium atoms. The TG analyses show that the complexes exhibit a step-wise decomposition character, with the major mass losses in the region 150-400 °C.
