Formation of a Stable Complex, RuCl₂(S₂CPPh₃)(PPh₃)₂, Containing an Unstable Zwitterion from the Reaction of RuCl₂(PPh₃)₃ with Carbon Disulfide

Abstract

New insight into the complexity of the reaction of the prominent catalyst RuCl2(PPh3)3 with carbon disulfide has been obtained from a combination of X-ray diffraction and (31)P NMR studies. The red-violet compound originally formulated as a cationic π-CS2 complex, [RuCl(π-CS2)(PPh3)3]Cl, has been identified as a neutral molecule, RuCl2(S2CPPh3)(PPh3)2, which contains the unstable zwitterion S2CPPh3. In the absence of RuCl2(PPh3)3, there is no sign of a reaction between triphenylphosphine and carbon disulfide, although more basic trialkylphosphines form red adducts, S2CPR3. Despite the presence of an unstable ligand, RuCl2(S2CPPh3)(PPh3)2 is remarkably stable. It survives melting at 173-174 °C intact, is stable to air, and undergoes reversible electrochemical oxidation to form a monocation. When the reaction of RuCl2(PPh3)3 with carbon disulfide is conducted in the presence of methanol, crystals of orange [RuCl(S2CPPh3)(CS)(PPh3)2]Cl·2MeOH and yellow RuCl2(CS)(MeOH)(PPh3)2 also form. (31)P NMR studies indicate that the unsymmetrical dinuclear complex (SC)(Ph3P)2Ru(μ-Cl)3Ru(PPh3)2Cl is the initial product of the reaction of RuCl2(PPh3)3 with carbon disulfide. A path connecting the isolated products is presented.

Biological Thiols and Carbon Disulfide: The Formation and Decay of Trithiocarbonates under Physiologically Relevant Conditions

“…Another could be a metal center because it is well established that transition-metal ions activate CS 2 toward reaction with coordinated nucleophiles and insertion into metal–ligand bonds, owing to the strong bonding of the 1,1-dithiolate (−CS 2 – ) functionality as a ligand. Such reactivity has been reported for metal–sulfur bonds 25 , 26 as well as with alkoxide, 27 amine, 28 , 29 and (even) phosphine 30 ligands. Given the relatively high cytosolic concentrations of GSH 31 and plasma-based protein sulfhydryls, 32 the reversible formation of unstabilized TTCs may play a role in CS 2 transport.…”

Cleavage of Carbon Disulfide by n‐Propyldiphenylphosphine and Nickel(II) Bromide

“…The process begins with the formation of the zwitterionic n ‐propyldiphenylphosphine/carbon disulfide adduct coordinated to NiBr 2 shown as a . Such adducts can, in some cases, for example, Et 3 PSC 2 , be isolated and are well known to coordinate to metal centers . Formation of the nickel(II) bromide adduct ( a ) renders the central carbon atom of the adduct susceptible to nucleophilic attack by either P n PrPh 2 and CS.…”

“…with the formation of the zwitterionic n-propyldiphenylphosphine/carbon disulfidea dduct coordinated to NiBr 2 shown as a.S uch adducts can, in somec ases, for example, Et 3 PSC 2 , [21,34] be isolated and are well known to coordinate to metal centers. [23,24] Formation of the nickel(II) bromide adduct (a)r enders the central carbon atom of the adduct susceptible to nucleophilic attack by either P n PrPh 2 and CS. (We suggest that CS is formed by reactiono fP n PrPh 2 and carbon disulfide, since it has been establishedt hat many metal complexes of CS are formed in reactions involvingt ertiaryp hosphine ligandsa nd carbon disulfide.)…”

“…When reacted with a transition metal, carbon disulfide can coordinate directly to the metal center to form a π‐CS 2 complex as seen in reaction (2) . In another case shown in reaction (3), carbon disulfide can insert into the metal phosphine bond to form a zwitterion (R 3 P + ‐CS 2 − ) as a bidentate ligand . Additionally, carbon disulfide can also react with a phosphine to cleave the carbon–sulfur bond to form a terminally bound CS ligand and a phosphine sulphide as depicted in reaction (4) .…”

“…[22] In another case shown in reaction(3), carbon disulfide can insert into the metal phosphine bond to form az witterion (R 3 P + -CS 2 À )a sabidentate ligand. [23,24] Additionally,c arbon disulfide can also react with a phosphine to cleave the carbon-sulfur bond to form at erminally bound CS ligand and ap hosphine sulphide as depicted in reaction (4). [25,26] Some nickel-phosphine complexese xhibit unusualr eactivity with carbon disulfide.…”