Silver(I) complexes with 1'-(diphenylphosphino)-1-cyanoferrocene: The art of improvisation in coordination
Abstract
1'-(Diphenylphosphino)-1-cyanoferrocene (1) reacts with silver(I) halides at a 1:1 metal-to-ligand ratio to afford the heterocubane complexes [Ag(mu(3)-X)(1-kappaP)]4, where X = Cl (2), Br (4), and I (5). In addition, the reaction with AgCl with 2 equiv. of 1 leads to chloride-bridged dimer [(mu-Cl)2{Ag(1-kappaP)2}2] (3) and, presumably, also to [(mu(P,N)-1){AgCl(1-kappaP)}]2 (3').
While similar reactions with AgCN furnished only the insoluble coordination polymer [(1-kappaP)2Ag(NC)Ag(CN)]n (6), those with AgSCN afforded the heterocubane [Ag(1-kappaP)(mu-SCN-S,S,N)]4 (7) and the thiocyanato-bridged disilver(I) complex [Ag(1-kappaP)2(mu-SCN-S,N)]2 (8), thereby resembling reactions in the AgCl-1 system. Attempted reactions with AgF led to ill-defined products, among which [Ag(1-kappaP)(2)(mu-HF2)]2 (9) and [(mu-SiF6){Ag(1-kappaP)2}2] (10) could be identified.
The latter compound was prepared also from Ag2[SiF6] and 1. Reactions between 1 and AgClO4 or Ag[BF4] afforded disilver complexes [(mu(P,N)-1)Ag(ClO4-kappaO)]2 (11) and [(mu(P,N)-1)Ag(BF4-kappaF)]2 (12) featuring pseudolinear Ag(I) centers that are weakly coordinated by the counter anions.
A similar reaction with Ag[SbF6] followed by crystallization from ethyl acetate produced an analogous complex, albeit with coordinated solvent, [(mu(P,N)-1)Ag(AcOEt-kappaO)]2[SbF6]2 (13). Ultimately, a compound devoid of any additional ligands at the Ag(I) centers, [(mu(P,N)-1)Ag]2[B(C6H3(CF3)2-3,5)4]2 (14), was obtained from the reaction of 1 with silver(I) tetrakis[3,5-bis(trifluoromethyl) phenyl] borate.
The reaction of Ag[BF4] with two equivalents of 1 produced unique coordination polymer [Ag(1-kappaP)(mu(P,N)-1)]n[BF4] n (15), the structure of which contained one of the phos-phinoferrocene ligands coordinated as a P, N-chelate and the other forming a bridge to an adjacent Ag(I) center.