Three 1,3,5-trialkyl-1,3,5-triazacyclohexane chromium tricarbonyl complexes fac-[Cr(CO) 3 (C 3 H 6 N 3 R 3 )] (R = Me, Et or Bu t ) have been prepared and their reactivities investigated. Both the kinetic and the thermodynamic stabilities of the complexes increase as the size of the R group increases. When R = Me or Et, the ligand is susceptible to displacement to produce [Cr(CO) 3 L 3 ] [L = pyridine or P(OMe) 3 ]. Room-temperature single crystal X-ray studies were carried out on the R = Me and Bu t complexes. Both molecules adopt the expected 'piano-stool' configuration with putative 3m symmetry; a crystallographic mirror plane passes through the methyl adduct. The Cr᎐N distances in the R = Me complex [2.153(3), 2 × 2.181(2) Å] are shorter than in the Bu t case [2.202(5) Ϫ 2.216(4) Å]; in both the substituents are obligate equatorial relative to the triazacyclohexane ring.

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