The enantioselective intramolecular cyclopropanation of cis-substituted allylic diazoacetates catalyzed by the chiral ruthenium Schiff base complexes [Ru(Schiff base)(PPh 3 ) 2 ] (1) is described. Among this class of complexes examined, [Ru(2-Br-salen)(PPh 3 ) 2 ] (1a) is the most effective, catalyzing intramolecular cyclopropanation of cis-allylic diazoacetates cis-(CRHdCH)CH 2 OC(O)CHN 2 (R ) alkyl, aryl) in CHCl 3 solution to give [3.1.0]-bicyclic lactones with yields and ee values up to 71 and 90%, respectively. The analogous reactions of cis-alkenyl diazoacetates using [Ru(Schiff base)(CO)] (2) as catalyst gave comparable enantioselectivities (up to 91% ee) but lower product yields of 20-38%. Treatment of [Ru-(2,4-X-salen)(PPh 3 ) 2 ] (1d, X ) Br; 1e, X ) Cl; 1f, X ) I) with N 2 C(p-YC 6 H 4 ) 2 (Y ) H, MeO) and N-methylimidazole (MeIm) or pyridine (py) gave the monocarbene complexes [Ru(2,4-X-salen)(C(p-and [Ru(2,4-Br-salen)(CPh 2 )(py)] (4, H 2 (2,4-Br-salen) ) bis(3,5-dibromosalicylidene)-(1R,2R)-cyclohexanediamine), respectively. X-ray crystal structure determinations revealed RudC(carbene) distances of 1.921(12) Å for 3a, 1.913(5) Å for 3b, 1.919(14) Å for 3c, 1.910(2) Å for 3d, and 1.917(4) Å for 4. A comparison of the structures and electrochemistry of 1, [Ru(Schiff base)(CO)(MeIm)], 3, and 4 with those of the porphyrin analogues is presented.