A series of mononuclear ruthenium(II) complexes with sterically demanding bis(phosphino)methanes and arsino(phosphino)methanes as ligands

The bis(η3-2-methylallyl)ruthenium(II) complexes [Ru(η3-2-MeC3H4)2(κ2-R2PCH2PPh2)] (R=iPr 2, Cy 3) were prepared from the cycloocta-1.5-diene derivative [Ru(η3-2-MeC3H4)2(η4-C8H12)] (1) and the unsymmetrical bis(phosphino)methanes R2PCH2PPh2 (R=iPr, Cy). Treatment of 2 with benzoic acid and with acetic acid in the presence of iPr2PCH2PPh2 led, after proton-assisted cleavage of the allylmetal bond, to the formation of the bis(carboxylato)ruthenium(II) compounds 4 and 5a/5b, respectively. Similarly, the bis(trifluoroacetate) [Ru(η1-O2CCF3)2(κ2-iPr2PCH2PiPr2)2] (7) was prepared and the molecular structure determined by X-ray crystallography. The reaction of 2 and 3 with hexafluoroacetone afforded the chelate complexes [Ru(η2-acac-f6)2(κ2-R2PCH2PPh2)] (R=iPr 8, Cy 9) which were also accessible from [Ru(η2-OC6Cl5)2(κ2-R2PCH2PPh2)] (R=iPr 10, Cy 11) by treatment with Hacac-f6. The preparation of the non-fluorinated bis(acac) compound [Ru(η2-acac)2(κ2-iPr2PCH2PPh2)] (12), which could not be obtained from 2 and Hacac, was achieved by ligand exchange from 10 and acetylacetone in the presence of Na2CO3. The reaction of 10 with CO and CNtBu gave by partial opening of the chelate rings the substitution products [Ru(OC6Cl5)2(CO)(κ2-iPr2PCH2PPh2)] (13) and [Ru(OC6Cl5)2(CNtBu)3(κ1-Ph2PCH2PiPr2)] (14), the latter containing the unsymmetrical bis(phosphino)methane as a monodentate ligand. With the dimer [RuCl(μ-Cl)(η3:η3-C10H16)]2 (15) as the starting material, the mononuclear ruthenium(IV) complexes [RuCl(η3:η3-C10H16)(κ2-iPr2PCH2PiPr2)]BF4 (16) and [RuCl2(η3:η3-C10H16)(κ-P-iPr2PCH2AstBu2)] (17) were prepared.