No abstract

Copper (I) guanidinate dimers were generated by a salt metathesis route and structurally characterized. The guanidinates differed from the known amidinate dimers because of a large torsion of the dimer ring. This had a direct effect on their thermal chemistry. The thermal reactivity was investigated by several methods, including a novel temperature-resolved, gas-phase method that was monitored by mass spectrometry. The copper guanidinates underwent carbodiimide deinsertion to produce copper metal at temperatures between 225 -and 250 degrees C in the gas phase and at 125 degrees C in solution. The amidinate investigated also showed copper deposition at 190 degrees C in the gas phase, and 135 degrees C in solution, but without carbodiimide deinsertion. The guanidinate compounds deposited crystalline copper at 225 degrees C in a simple chemical vapor deposition experiment.

Keywords: Thermal reaction mechanism / Gold / Silver / Copper / N ligands / Chemical vapor deposition Several guanidinates of copper and silver, as well as amidinates and guanidinates of gold were synthesized as potential precursors for vapour deposition methods. These compounds were found to be dimers in the case of copper and gold, and trimers in the case of silver. The copper compounds showed good thermal and photostability, and were isolable by sublimation. The silver compounds proved to be very reactive to both heat and light, and were found to deposit silver metal when heated, suggesting that these sensitive compounds might be used as single source precursors. The gold compounds were found to exhibit some heat and light sensitivity,

Stable alkyl (or aryl) hydrides of first-row transition metals are rare, presumably because the reductive elimination of alkane (or arene) is both thermodynamically favorable and kinetically facile. [1] Exceptions to this empirical rule are of considerable interest, [2] especially when both sides of the CÀH activation equilibrium are directly observable. Herein, we describe a pair of such molecules and the unusual magnetic behavior of one of them.Reaction of [{({iPr 2 (C 6 H 3 )} 2 nacnac)Cr} 2 (m-Cl) 2 ] [3] with PhMgCl in THF produced the mononuclear phenyl complex [({iPr 2 (C 6 H 3 )} 2 nacnac)CrPh(thf)] (1; {iPr 2 (C 6 H 3 )} 2 nacnac = 2,4-pentane-N,N'-bis(2,6-diisopropylphenyl)ketiminate). Complex 1 adopts a slightly distorted square-planar coordination about the Cr II center (see the Supporting Information), and its effective magnetic moment (m eff = 4.8(1) m B at 295 K) is consistent with the four unpaired electrons of a high-spin d 4 configuration. Exposure of 1 to H 2 gas (1 atm) yielded two metal complexes. The major product was identified spectroscopically as the previously described hydride [{({iPr 2 -(C 6 H 3 )} 2 nacnac)Cr} 2 (m-H) 2 ] (2), which is the product of a straightforward hydrogenolysis of 1 with subsequent dimerization. The minor product (17 %) was a new compound, and it was revealed by X-ray structure determination (Figure 1 a) to be [{({iPr 2 (C 6 H 3 )} 2 nacnac)Cr} 2 (m-Ph)(m-H)] (3).[4] The binuclear chromium complex is held together by a bridging hydride (which was clearly located in the difference map) and a bridging phenyl ligand. The presence of the hydride ligand was confirmed by spectroscopic methods. Most importantly, the LIFDI mass spectrum of 3 (LIFDI = liquid injection field desorption ionization) showed the molecular ion (m/z 1016) as the base peak, with excellent agreement between the experimental and calculated isotope patterns.[ (10) is consistent with some degree of metal-metal bonding; however, the potential-energy surface of Cr II -Cr II interactions is notoriously flat, and any CrÀCr bond in 3 would probably not be strong.[6] At m eff = 2.4(1) m B (293 K), the magnetic moment of 3 at the very least indicates relatively strong antiferromagnetic coupling between the Cr II ions, which was confirmed by variable-temperature magnetic susceptibility measurements (see the Supporting Information). Thus, the spin ground state of 3 is S = 0. The formation of 3 most likely involves trapping of a mononuclear hydride formed in situ by remaining 1. We note that 2, once formed, does not react with 1 to produce 3.