Carbene complexes. Part 16. Synthesis and properties of NN′N″N‴-tetra-aryl-substituted electron-rich olefin-derived carbeneruthenium(II) complexes containing a spontaneously formed ortho-metallated-N-arylcarbene ligand; the crystal and molecular structures of [RuCl{CN(C6H4Me-4)CH2CH2NC6H3Me-4}(PEt3)2](6) and [Ru(CO)Cl{CN(C6H4Me-4)CH2CH2NC6H3Me-4}(PEt3)2](16)
Abstract
The complex [RuCl2(PPh3)3] reacts thermally with the electron-rich olefin [[graphic omitted]R′]2(R′= Ph, C6H4Me-4, C6H4OMe-4, or C6H4OMe-2), LR′2′ with elimination of PPh3 and HCl, forming the five-co-ordinate carbeneruthenium(II) complex containing an ortho-metallated N-arylcarbene ligand [[graphic omitted]″}(PPh3)2], abbreviated as [[graphic omitted]R′)(PPh3)2]. One of these complexes (R′= C6H4Me-4) is also formed from [RuCl(NO)(PPh3)2] and LR′2. The five-co-ordinate ruthenium(II) complexes readily undergo PR3 exchange [R3= Et3, Bun3, Bun2Ph, Et2Ph, Me2Ph, but not (C6H11)3]; with [[graphic omitted]Et]2(LEt2), the unusual bis-(carbene) complex [[graphic omitted]R′)(LEt)(PPh3)](R′= C6H4Me-4) is formed. Small ligands [e.g. CO, PF3, P(OMe)3, or NCMe] generally add to form six-co-ordinate complexes of variable thermal stability. The complex [RuCl3(NO)(PPh3)2] with LR′2, also affords an ortho-metallated complex [[graphic omitted]R′)(NO)(PPh3)]; this, like the other six-co-ordinate ruthenium(II) derivatives, does not undergo PR3 exchange, but with LEt2 NOCl is lost and [[graphic omitted]R′)(LEt)(PPh3)](R′= C8H4Me-4) is formed. Spectroscopic data provide information on the nature and stereochemistry of the complexes, the magnitude of 2J(13C–31P) being especially useful, with 2Jtrans2Jcis. The five- and six-co-ordinate complexes are stereochemically rigid in solution. X-Ray analyses of the two title compounds have been refined to R and R′ of 0.054 and 0.093 for [[graphic omitted]R′)(PEt3)2](R′= C6H4Me-4)(6), and 0.045 and 0.053 for [[graphic omitted]R′)(PEt3)2](R′= C6H4Me-4)(16), respectively. In overall pseudo-octahedral geometry about ruthenium, complexes (6) and (16) differ only in the replacement of a weak Ru ⋯ HC contact (2.23 Å) in the former for a CO ligand in the latter. The bond lengths within the co-ordination sphere of (6) are slightly greater in (16), the smallest increase (0.011 Å) being for the Ru–P bonds and the largest (0.119 Å) for the Ru–C(6) bond [C(6) is the C of the metallated phenyl ring]. In complex (6) the two Ru–C(sp2) distances are 2.006(8)[Ru–C(6)] and 1.911(6)Å(Ru–Ccarb.).