Open Collections

Reactivity and coordination chemistry of ruthenium(II) aminophosphine complexes with H2S,thiols,H2O and other small molecules

University of British Columbia

The coordination of small molecules (H₂S, RSH, H₂0, ROH, H₂ , NH₃ , N₂ and N₂0; R = alkyl) to the coordinatively unsaturated complexes RuX₂ (P-N)(PR₃) (X = CL Br, I; P-N = [o-(7Y,A/-dimethylamino)phenyl]diphenylphosphine; R = Ph, /7-tolyl), themselves prepared from RuX₂ (PR₃)₃ and P-N, was investigated (see figure). The species containing the Ru(P-N) moiety were characterized spectroscopically, particularly by *H and 31P{1H} NMR and in some cases in conjunction with X-ray crystallography. [picture of chemical structues] Cis-RuX₂ (P-N)(PPh₃)(L) species (X = CI, L = H₂S, MeSH, EtSH; X = Br, L = H₂S) were isolated from the reaction of RuX₂ (P-N)(PPh₃) with excess L in acetone, and characterized crystallographically. The geometry of these complexes is pseudo-octahedral with the halogen atoms in mutual cis positions with the coordinated S-ligand cis to the P-atom of the P-N ligand and trans to a halogen atom; all H-atoms on the coordinated S-ligands were refined isotropically. The S-H bond lengths are of equal or shorter distances (1.20 - 1.34 Å) than those of free gaseous ligands (1.33 - 1.40 Å); in particular, the bond length of 1.03 Å for the coordinated MeSH complex is the shortest S-H distance yet reported. Of interest, the ^NMR spectrum of c/s-RuX₂ (P-N)(PPh₃)(SH₂) shows three-bond coupling of only one proton of the coordinated H₂S to the P-atom of the P-N ligand (X = C1, 3JHP= 3.5 HZ; X = Br, 3JHP = 4.3 Hz) at -50°C, and this represents an extension of the Karplus relationship to vicinal coupling within a P-Ru-S-H system. The reaction of RuCl₂ (P-N)(PR₃) with H20 gave /raws-RuCl₂ (P-N)(PR3XOH₂), which was crystallographically characterized. The geometry is pseudo-octahedral with mutually trans Cl-atoms; the H₂0 ligand is trans to the P-atom of the P-N ligand. The orientation of incoming monodentate ligand L in either cis or trans positions (see figure) is affected by the mutual trans influence of L and of the apical phosphine of RuX₂ (P-N)(PR₃). The thermodynamics for the reversible binding of H2S, thiols, H 2 and H20 to RuCl₂ (P-N)(PPh₃), in solution, were determined using UV-Vis and NMR spectroscopies. The low AH0 values (-22 to -54 kJ/mol) imply relatively weak Ru-L bond energies and the negative AS° values (-32 to -140 J/mol K) are consistent with binding of a small molecule at a metal site. Differential scanning calorimetry on solid state samples also allowed for determination of AH° values, and estimation of enthalpy changes for a cis- to transrearrangement in solution. Cw-RuX₂ (P-N)(PPh3)(SH₂) (X = CI, Br) reacted with NaSH or proton sponge (in the presence of added H2S) to give initially Ru(SH)Cl(P-N)(PPh3) and then Ru(SH)₂ (P-N)(PPh₃). The mercapto species, however, are thermally unstable and were only observed by NMR spectroscopy at -78°C. Reaction of 1 atm NH3 with RuX₂ (P-N)(PPh₃) (X = CI, Br) in the solid state led to the formation of frans-RuX₂ (P-N)(PPh3)(NH₃) which, when dissolved in solution, subsequently isomerized to cw-RuX₂ (P-N)(PPh3)(NH₃). Evidence for bis- and tris-arnmine species, as well as for [RuX(P-N)(PPh₃)(NH₃) ₂—X] with a 'strongly associated' halide, is also presented. The formation of cis-RuCl₂ (P-]S0(PPh₃)(N₂O) was observed by NMR spectroscopy at -40°C when RuCl₂ (P-N)(PPh₃) was subjected to 6 atm N₂0 in CD₂Cl₂. The coordination of N₂0 is of particular interest because of the rarity of such a reaction and because of the potential of discovering an effective catalytic oxidation system using N₂0 as an O-atom donor. In fact, c/5-RuCl₂ (P-N)(PPh₃)(N₂0) appears to form c/s-RuCl₂ (P-]S0(PPh₃)(V-N₂) and 02 at T > -40°C. When the system was warmed to room temperature, 0=PPh₃ and (u,-0)(n-Cl)₂[RuCl(P-N)]₂ were formed. The crystallographically characterized u>oxo complex was also formed when RuCl₂(P-N)(PPh₃) was reacted with 0₂. RuCl₂(P-N)(PPh₃) also reacted with HOCPh to give the crystallographically characterized cw-RuCl₂{TJ-N)(PPh₃)(=C=CHPh). The carbene complex reacted with H2S and H₂0 to give c/j-RuCl₂(P-N)(PPh₃)(S=C(H)CH₂Ph) and a mixture containing RuCl(P-N)(PPh₃)(CH₂Ph)(CO) and RuCl₂(P-N)(PPh₃)(CO), respectively. The formulations of the products were based on 31P{1H} NMR and IR spectroscopic data. The reactions of RuCl₂(PR₃) ₃ with aminophosphine ligands other than P-N were also explored: RuCl₂(BPN)(PR₃) (BPN = bis[o-N,N-dimethylammo)phenyl]phenylphosphine) and RuCl₂(PAN)(PR₃) (PAN = l-(N,N-dimethylamino)-8-(diphenylphosphino)naphthalene) were isolated and characterized; RuCl₂(AMPHOS)(PPh₃) (AMPHOS = (R)-(+)-N,N-dimethyl-l-[o- (dimethylphosphino)phenyl]ethylamine) was observed in situ, and an impure sample of RuCl₂(ALAPHOS)₂ (ALAPHOS = [(S)-2-(dimethylamino)propyl]diphenylphosphine) was isolated. PTN (tris[o-(N,N-dimethylamino)phenyl]phenylphosphine) did not react with RuCl₂(PR₃)₃.

Thesis/Dissertation

application/pdf

2009-07-02

For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.

http://hdl.handle.net/2429/10011

Chemistry

University of British Columbia

UBCV

DSpace