Reaction of 2 equiv of K[1,3-(SiMe3)2C3H3] with NiBr2(dme) in THF at -78 degrees C produces the orange pi-allyl complex [1,3-(SiMe3)2C3H3]2Ni (1). Unlike the pyrophoric (C3H5)2Ni, the trimethylsilylated derivative only slowly decomposes in air (from hours to days). Both eclipsed (1a) and staggered (1b) conformations are found in solution; the eclipsed form irreversibly converts to the thermodynamically more stable staggered conformation when heated above 85 degrees C. Single-crystal X-ray structures obtained for both 1a and 1b confirm that the allyl ligands are bound in a trihapto manner to the metals and that trimethylsilyl substituents are in syn, anti arrangements. Density functional theory calculations performed on the bis(allyl)nickel complexes indicate that the substituents exert little effect on the basic metal-ligand geometries. Trimethylphosphine is converted to tetramethyltetraphosphane, (MeP)4, on reaction with 1. In toluene, 3-bromo-1,3-bis(trimethylsilyl)propene reacts with (COD)2Ni to produce the dimeric purple complex {[1,3-(SiMe3)2C3H3]NiBr}2 (2a). Both NMR and X-ray crystallographic data establish that the allyl ligands are staggered and that the trimethylsilyl substituents are in a syn, syn conformation. NMR data indicate that the reaction of one equivalent of 1 with Br2 in benzene produces an analogous complex (2b) with the allyl ligand substituents in a syn, anti configuration. When 1 equiv of 1 is treated with I2 in hexanes, the dark red dimeric complex {[1,3-(SiMe3)2C3H3]NiI}2 (3) is formed. Its X-ray crystal structure demonstrates that both eclipsed (3a) and staggered (3b) allyl conformation are present. The trimethylsilyl groups on the allyl ligands are in syn, anti arrangements in the two forms.
The title compound, bis[(1,2,3-)-(2E)-1,3-bis(trimethylsilyl)prop-2-enyl]cobalt(II), [Co(C 9 H 21 Si 2 ) 2 ], is a homoleptic allyl complex with 3 -bound ligands. The CoÐC distances range from 1.996 (3) to 2.096 (3) A Ê and the allyl ligands adopt staggered, nearly parallel, arrangements around the Co atom. The trimethylsilyl groups are in syn±anti conformations; the steric shielding they provide to the metal is probably responsible for the thermal stability of the compound.
ExperimentalUnder a nitrogen atmosphere, CoCl 2 (0.500 g) was dissolved in tetrahydrofuran (THF; 10 ml) and cooled to 195 K. A solution of metal-organic compoundsThe molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
The N2 analogue phosphorus nitride (PN) was the first phosphorus containing compound to be detected in the interstellar medium, however this thermodynamically unstable compound has a fleeting existence on Earth. Here, we show that reductive coupling of iron(IV) nitride and molybdenum(VI) phosphide complexes assembles PN as a bridging ligand in a structurally-characterized bimetallic complex. Reaction with C≡N<sup>t</sup>Bu releases the mononuclear complex [(N<sub>3</sub>N)Mo-PN]<sup>−</sup>, N<sub>3</sub>N = [(Me<sub>3</sub>SiNCH<sub>2</sub>CH<sub>2</sub>)<sub>3</sub>N]<sup>3−</sup>), which undergoes light-induced linkage isomerization to provide [(N<sub>3</sub>N)Mo-NP]<sup>−</sup>, as revealed by photocrystallography. While structural and spectroscopic characterization, supported by electronic structure calculations reveal PN multiple bond character, coordination to molybdenum creates nucleophilic character at the terminal atom of the PN/NP ligands. Indeed, the linkage isomers can be trapped in solution by reaction with a Rh(I) electrophile.
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