Synthesis of heterodinuclear FeRu(CO)6(R-DAB)(6e)) (R-DAB=RN=C(H) C(H)=NR).Comparison of the reactivities of heterodinuclear FeRu(CO)6(R-DAB(6e)) and homodinuclear analogues M2(CO)6(R-DAB(6e)) (M =Fe, Ru). Single crystal X-ray structures of FeRu(CO)6(i-Pr-DAB(6e)) and FeRu(CO)5(i-Pr-DAB(4e))(C3H4),

Abstract

The reactions of Fe(CO)3(R-DAB; R1, H(4e)) (1a: R = i-Pr, R1 = H; 1b: R = t-Bu, R1 = H; 1c: R = c-Hex, R1 = H; 1e: R = p-Tol, R1 = H; 1f: R = i-Pr, R1 = Me) with Ru3(CO)12 and of Ru(CO)3(R-DAB; R1, H(4e)) (2a: R = i-Pr, R1 = H; 2d: R = CH(i-Pr)2, R1 = H) with Fe2(CO)9 in refluxing heptane both afforded FeRu(CO)6(R-DAB; R1, H(6e)) (3) in yields between 50 and 65%.The coordination mode of the ligand has been studied by a single crystal X-ray structure determination of FeRu(CO)6(i-Pr-DAB(6e)) (3a). Crystals of 3a are monoclinic, space group P21/a, with four molecules in a unit cell of dimensions: a = 22.436(3), b = 8.136(3), c = 10.266(1) Å and = 99.57(1)o. The structure was refined to R = 0.049 and Rw = 0.052 using 3045 reflections above the 2.5(I) level. The molecule contains an FeRu bond of 2.6602(9) Å, three terminally bonded carbonyls to Fe, three terminally bonded carbonyls to Ru and bridging 6e donating i-Pr-DAB ligand. The i-Pr-DAB ligand is coordinated to Ru via N(1) and N(2) occupying an apical and equatorial site respectively (RuN(1) = 2.138(4) RuN(2) = 2.102(3) Å). The C(2)N(2) moiety of the ligand is 2-coordinated to Fe with C(2) in an apical and N(2) in an equatorial site (FeC(2) = 2.070(5) and FeN(2) = 1.942(3) Å).The 1H and 13C NMR data indicate that in all FeRu(CO)6(R-DAB(6e)) complexes (3a to 3f) exclusively 2-CN coordination to the Fe atom and not to the Ru atom is present irrespective of whether 3 was prepared by reaction of Fe(CO)3(R-DAB(4e)) (1) with Ru3(CO)12 or by reaction of Ru(CO)3(R-DAB(4e)) (2) with Fe2(CO)9. In the case of FeRu(CO)6(i-Pr-DAB; Me, H(6e)) (3f) the NMR data show that only the complex with the C(Me)N moiety of the ligand -N coordinated to the Ru atom and the C(H)N moiety 2-coordinated to the Fe atom was formed. Variable temperature NMR experiments up to 140 oC showed that the -diimine ligand in 3a is stereochemically rigid bonded.FeRu(CO)6(R-DAB(6e)) (3a and 3e) reacted with allene to give FeRu(CO)5(R-DAB(4e))(C3H4) (4a and 4e). A single crystal X-ray structure determination of FeRu(CO)5(i-Pr-DAB(4e))(C3H4) (4a) was performed. Crystals of 4a are triclinic, space group P1, with two molecules in a unit cell of dimensions: a = 9.7882(7), b = 12.2609(9), c = 8.3343(7) Å, = 99.77(1)o, = 91.47(1)o and = 86.00(1)o. The structure was refined to R = 0.028 and Rw = 0.043 using 4598 reflections above the 2(I) level. The molecule contains an FeRu bond of 2.7405(7) Å and three terminally bonded carbonyls to iron. Two carbonyls are terminally bonded to the Ru atom together with a chelating 4e donating i-Pr-DAB ligand [RuN = 2.110(1) (mean)]. The allene ligand is coordinated in an 3-allylic fashion to the Fe atom while the central carbon of the allene moiety is -bonded to the Ru atom (FeC(14) = 2.166(3), FeC(15) = 1.970(2), FeC(16) = 2.127(3) and RuC(15) = 2.075(2) Å). The 1H and 13C NMR data show that in solution the coordination modes of the R-DAB and the allene ligands are the same as in the solid state.Thermolysis reactions of 3a with R-DAB or carbodiimides gave decomposition and did not afford C(imine)C(reactant) coupling products. Thermolysis reactions of 3a with M3(CO)12 (M = Ru, Os) and Me3NO gave decomposition. When the reaction of 3a with Me3NO was performed in the presence of dimethylacetylenedicarboxylate (DMADC) the known complex FeRu(CO)4(i-Pr-DAB(8e))(DMADC) (5a) was formed in low yield. In 5a the R-DAB ligand is in the 8e coordination mode with both the imine bonds 2-coordinated to iron. The acetylene ligand is coordinated in a bridging fashion, parallel with the FeRu bond