Synthesis and characterization of 1′-(diphenylphosphino)-1-isocyanoferrocene, an organometallic ligand combining two different soft donor moieties, and its Group 11 metal complexes

The development of a practical synthesis of 1'-(diphenylphosphino)-1-aminoferrocene (2) and its P-borane adduct (2B) allowed the facile preparation of 1'-(diphenylphosphino)-1-isocyanoferrocene (1). This compound combining two specific soft-donor moieties was studied as a ligand for univalent Group 11 metal ions. The reactions of 1 with AgCl at 1 : 1 and 2 : 1 molar ratios only led to the coordination polymer [Ag-2(mu-Cl)(2)(mu(P,C)-1)](n) (6), while those with Ag[SbF6] provided the dimer [Ag-2(Me2CO-kappa O)(2)(mu(P,C)-1)(2)][SbF6](2) and the quadruply-bridged disilver complex [Ag-2(mu(P,C)-1)(4)][SbF6](2) (8), respectively. Addition of 1 to [AuCl(tht)] (tht = tetrahydrothiophene) afforded the mono-and the digold complex, [AuCl(1-kappa P)] (9) and [(mu(P,C)-1)(AuCl)(2)] (10), depending on the reaction stoichiometry. Finally, the reaction of 1 with [Au(tht)(2)][SbF6] or halogenide removal from 9 with AgNTf2 led to cationic dimers [Au-2(mu(P,C)-1)(2)]X-2 (11, X = SbF6 (a) or NTf2 (b)). Catalytic tests in the Au-mediated isomerization of (Z)-3-methylpent-2-en-4-yn-1-ol to 2,3-dimethylfuran revealed that 11a and 11b are substantially less catalytically active than their analogues containing 1'-(diphenylphosphino)-1-cyanoferrocene as the ligand, most likely due to a stronger coordination of the isonitrile moiety, which prevents dissociation of the dimeric complexes into catalytically active monomeric species.