| Summary: | 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.
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