CHROMIUM(0) TRICARBONYL COMPLEXES OF 1,3,5-TRIAZACYCLOHEXANES

Three 1,3,5-trialkyl-1,3,5-triazacyclohexane chromium tricarbonyl comp lexes fac-[Cr(CO)(3)(C3H6N3R3)] (R = Me, Et or Bu-t) have been prepare d and their reactivities investigated. Both the kinetic and the thermo dynamic stabilities of the complexes increase as the size of the R gro up increases. When R = Me or Et, the ligand is susceptible to displace ment to produce [Cr(CO)(3)L-3] [L = pyridine or P(OMe)(3)]. Room-tempe rature single crystal X-ray studies were carried out on the R = Me and Bu-t complexes. Both molecules adopt the expected 'piano-stool' confi guration with putative 3m symmetry; a crystallographic mirror plane pa sses through the methyl adduct. The Cr-N distances in the R = Me compl ex [2.153(3), 2 x 2.181(2) Angstrom] are shorter than in the Bu-t case [2.202(5) - 2.216(4) Angstrom]; in both the substituents are obligate equatorial relative to the triazacyclohexane ring.