Routes to Ruthenium–Fluoro Cations of the Type [RuL2(CO)nF]+ (n = 2,3; L = PR3, NHC): A Play‐Off between Solvent, L and Weakly Coordinating Anion

Abstract

AbstractInteraction of cis,cis,trans‐[RuF2(CO)2(PPh3)2] (1a) with BF3 in acetonitrile affords the dicationic adduct [Ru(NCMe)2(CO)2(PPh3)2](BF4)(B2F7) (2), which can be readily carbonylated to form [Ru(CO)4(PPh3)2](BF4)2 (3). In contrast, reaction of 1a with BF3 in dichloromethane leads to the neutral ruthenium–fluoro species [RuF(FBF3)(CO)2(PPh3)2] (4); facile displacement of the bound FBF3 ligand in 4 occurs on treatment with CO or PPh3 to afford cationic [RuF(CO)2(L)(PPh3)2](BF4) [L = CO (5a), PPh3 (5b)]. On the other hand, reaction of 1a with PF5 in dichloromethane furnishes the coordinatively unsaturated 16‐electron salt [RuF(CO)2(PPh3)2](PF6) (6). Metathesis of the PF6 anion in 6 with KB(ArF)4 [ArF = 3,5‐(CF3)2C6H3] in dichloromethane results in rapid decomposition, while in the presence of CO solvent exchange (CH2Cl2) takes place to yield chloride‐containing [RuCl(CO)3(PPh3)2][B(ArF)4] (7). Unexpectedly, 1a proved unreactive towards tris(pentafluorophenyl)borane in dichloromethane. However, by substituting the triphenylphosphane ligands in 1a with better donor phosphanes or with an N‐heterocyclic carbene (NHC) [to give cis,cis,trans‐[RuF2(CO)2(L)2] [L = PEt2Ph (1b), P(CCPh)Ph2 (1c), IPr (1,3‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) (1d)], fluoride abstraction could be achieved using B(C6F5)3 to give 16‐electron [RuF(CO)2(L)2][FB(C6F5)3] (L = PEt2Ph (8b), P(CCPh)Ph2 (8c), IPr (8d)]. Carbonylation of 8d proceeds smoothly to generate the coordinatively saturated species [RuF(CO)3(IPr)2][FB(C6F5)3] (9) in high yield. Single crystal X‐ray structures are presented for 2, 3, 5a/3, 7 and 9.