INFLUENCE OF HETERONUCLEARITY ON THE DIMERIZATION OF HFERU(CO)5(RC=C(H)C(H)=N-IPR)AND THE SYNTHESIS OF HETEROTETRANUCLEAR CHAIN COMPLEXES

The directed synthesis of heterodinuclear Fe-Ru and of heterotetranuclear Fe(m)Ru(n) (m = 1, 2; n = 4 - m) chain complexes is described. The thermal reaction of HFeRu(CO)5{RC=C-(H)C(H)=N-iPr} (1a, R = Ph; 1b, R = Me) leads to decomposition in the case of 1b and to C-H activation within the N-iPr group of la, affording FeRu(CO)6{PhCC(H)C(H)N=C(Me)2} (2) and FeRu3(CO)10{PhC=C(H)C(H)=N-iPr}2 (3) as a byproduct. When styrene is used as an additive in this reaction, 2 is formed selectively. When styrene is applied in the thermal reaction of 1b, smooth conversion into the heterotetranuclear chain complex Fe2Ru2(CO)10{MeC=C-(H)C(H)=N-iPr)2 (5) takes place. Complex 5 is formed as a mixture of four noninterconverting isomers (at 293 K on the NMR time scale), which are assigned on the basis of H-1 and C-13 NMR spectra as the cis and trans isomers of two diastereomers. The expected product of the reaction of lb with styrene, i.e. FeRu(CO)6{C(H)2CC(H)C(H)=N-iPr} (7), is shown to be formed by the conversion of [FeRu(CO)6{MeC=C(H)C(H)=N-iPr}][BF4] (6b) on silica. Complex 7 reacts with H2 to give lb. In the reaction of la with 3,3-dimethyl-1-butene, alkene insertion into the Fe-H bond and a subsequent alkyl shift from Fe to C(beta) of the monoazadienyl (MAD-yl) ligand occurs. Complex la is shown to be a precatalyst for the homogeneous hydrogenation of styrene and alpha-methylstyrene. As the remaining organometallic species, FeRu(CO)6{PhCC(H)C(H)N-(H)-iPr} (9aII) has been isolated. Besides the Fe2RU2 chain complex 5, also the chain complex FeRu3(CO)10{PhC=C(H)C(H)=N-iPr}{MeC=C(H)C(H)=N-iPr} (8), containing two differently substituted MAD-yl ligands, is prepared by the reaction of la with Ru2(CO)6{C(H)(H)=N-iPr} (13). The X-ray crystal structures of 7 and 8 have been determined. Crystals of 7 are triclinic, space group P1BAR, with a = 8.533(2) angstrom, b = 9.125(2) angstrom, c = 11.082(2) angstrom, alpha = 69.74(2)-degrees, beta = 82.48(2)-degrees, gamma = 73.41(2)-degrees, V = 775.3(3) angstrom3, Z = 2, and final R = 0.0224 for 3207 reflections with I > 2.5sigma(I) and 212 parameters. Crystals of 81 are monoclinic, space group P2,/n, with a = 12.088(2) angstrom, b = 19.314(3) angstrom, c = 15.016(2) angstrom, beta = 111.48(1)-degrees, V = 3262.3(9) angstrom3, Z = 4, and final R = 0.0377 for 4953 reflections with I > 2.5sigma(I) and 422 parameters. The structure of 8 shows the presence of a FeRu3-chain metal skeleton, in which, unexpectedly, the Fe atom is situated at a terminal site.