Further chemistry of tris(µ-methylene)-hexakis(trimethylphosphine)diruthenium(III). Synthesis and X-ray crystal structures of bis[bis(µ-methylene)-tetrakis(trimethylphosphine)ruthenium(III)]ruthenium(IV)-(Ru–Ru–Ru) bis(tetrafluoroborate), tris(µ-hydroxo)-hexakis(trimethylphosphine)diruthenium(II) tetrafluoroborate, and tricarbonylbis(trimethylphosphine)ruthenium(0)

Abstract

Further chemistry of the triple methylene (–CH₂–) bridged compound Ru₂(µ-CH₂)₃(PMe₃)₆ and its derivatives is described. The compounds [(Me₃P)₄Ru(µ-CH₂)₂Ru(µ-CH₂)₂Ru(PMe₃)₄][BF₄]₂, (1), and [Ru₂(µ-OH)₃(PMe₃)₆][BF₄], (2), have been isolated from the interaction of aqueous fluoroboric acid with a red oil obtained during the synthesis of Ru₂(µ-CH₂)₃(PMe₃)₆. Interaction of carbon monoxide (5 atm) with Ru₂(µ-CH₂)₃(PMe₃)₆ gives trans-Ru(PMe₃)₂(CO)₃, (3). The compounds have been studied by i.r. and n.m.r. (¹H and ³¹P) spectroscopy and their X-ray structures have been determined.

Compound (1) is monoclinic, space group C2/c, with a= 32.793, b= 9.578, c= 19.821 Å, β= 123.36°, and Z= 4. The structure was solved via the heavy-atom method and refined to an R of 0.055 using 4 036 diffractometer data with F_o > 3σ(F_o). The cation is a linear trinuclear species with the Ru atoms linked by bridging methylenes and Ru–Ru bonds [Ru–Ru = 2.637(1)Å]. The central Ru^IV atom is tetrahedral with Ru–C bond lengths of 1.98(1)Å whilst the terminal Ru^III atoms are octahedral with two Ru–C distances of 2.09(1)Å, two Ru–P distances at 2.391, 2.402(3)Å and two at 2.424, 2.427(3)Å. Compound (2) is monoclinic, space group P2/n, with a= 15.075, b= 9.771, c= 12.709 Å, β= 109.9°, and Z= 2. The structure was refined to an R of 0.052 using 2 583 data with F_o > 4σ(F_o). The cation is dinuclear with three Ru(µ-OH)Ru bridges [Ru–O 2.134–2.144(3)Å] and no metal–metal bond [Ru ⋯ Ru = 3.004(1)Å]. The Ru–P distances are short, at 2.231–2.234(2)Å, and imply strong Ru → P π back bonding. Compound (3) is a monomeric Ru⁰ species with trans axial phosphines [Ru–P = 2.334, 2.345(1)Å] and equatorial carbonyls [Ru–C = 1.877, 1.905(4)Å]. Crystals are orthorhombic, space group Pnma, with a= 10.253, b= 10.650, c= 14.045 Å, and Z= 4. The structure was solved by heavy-atom methods and refined to an R of 0.043 using 1 757 data with F_o > 3σ(F_o).