PREPARATION OF NOVEL ALKYLATED RUTHENIUM ALPHA-DIIMINE COMPLEXES - REACTIVITY TOWARD CARBON-MONOXIDE AND PHOSPHINES

Ru2(CO)5((i)Pr-DAB) (1) reacts with Mel at room temperature to give Ru2(Me)(I)(CO)4((i)Pr-DAB) (2a), and a single-crystal X-ray structure determination of 2a has been obtained. Crystals of 2a are orthorhombic, space group Pbca, with unit-cell dimensions a = 16.2510 (10) angstrom, b = 13.2660 (10) angstrom, and c = 17.2410 (10) angstrom. The molecular structure consists of a Ru(Me)(CO)2 fragment and a Ru(CO)2 fragment, held together by an iodide bridge and a bridging alpha-diimine ligand. The DAB ligand is coordinated to the Ru(Me)(CO)2 fragment via both nitrogen atoms and to the Ru(CO)2 fragment via an eta2 coordination of both imine bonds. Treatment of 2a with CO leads to substitution of the iodide bridge and the two coordinated imine bonds with the formation of Ru(Me)(I)(CO)2((i)Pr-DAB) (3a) and Ru(CO)5. This reaction, which is reversible, provides a new synthetic route for the preparation of monomeric methylated alpha-diimine complexes. Several other reaction routes for the formation of the complexes Ru(X)(Y)(CO)2(alpha-diimine) (X = Me, Y = I, alpha-diimine = (i)Pr-DAB (3a); X = Me, Y = I, alpha-diimine = (i)Pr-Pyca (3b); X = Y = I, alpha-diimine = (i)Pr-DAB (3c); X = Y = I, alpha-diimine = (i)Pr-Pyca (3d); X = Cl, Y = benzyl, alpha-diimine = (i)Pr-DAB (3e)) are presented. Treatment of 2a with phosphines leads to substitution of only one coordinated imine bond, with the formation of Ru2(Me)(I)(CO)4(PR3)((i)Pr-DAB) (PR3 = PPh3 (4a), PMe2Ph (4b), P(OMe)3 (4c)). A single-crystal X-ray structure determination of 4b bas been obtained, and crystal of 4b are monoclinic, space group P2(1)/c, with unit-cell dimensions a = 7.2030 (10) angstrom, b = 21.907 (2) angstrom, c = 16.813 (3) angstrom, and beta = 94.352 (13)-degrees. The molecular structure of 4b consists of a Ru(Me)(CO)2 fragment and a Ru(CO)2(PMe2Ph) fragment which are bridged by an iodide atom and a 6e-donating sigma(N)-mu2(N')-eta2(C=N)-bonded DAB ligand. Complexes 4a-c easily lose a carbonyl ligand to form Ru2(Me)(I)(CO)3(PR3)((i)Pr-DAB) (PP-3 = PPh3 (5a), PMe2Ph (5b), P(OMe)3 (5c)), and this reaction is shown to be reversible. Upon treatment of 3a with Ru(CO)4 fragments complex 2a is formed in good yield. Furthermore, reaction of 3a with Fe(CO)4 fragments leads to the formation of the heteronuclear complex FeRu(Me)(I)(CO)4((i)Pr-DAB) (2b). In the presence of traces of water HFeRu(Me)(CO)5((i)Pr-DAB) (6) is produced as a side product. A single-crystal X-ray structure determination of 6 has been obtained and crystals of 6 are monoclinic, space group C2/c, with unit-cell dimensions a = 18.102 (4) angstrom, b = 8.2761 (6) angstrom, c = 25.131 (4) angstrom, and beta = 90.627 (16)-degrees. As in 4b the DAB ligand in 6 is sigma(N)-mu2(N')-eta2(C=N)-coordinated to the bimetallic core, with the sigma(N) coordination to the Ru center and the eta2(C=N) coordination to the Fe center. The hydride ligand of 6 was found to be bridging the metal-metal bond. Finally, the monomeric diiodide complex 3c was reacted with Ru(CO)4 fragments to form Ru2(I)2(CO)4((i)Pr-DAB) (7).