1'-(Diphenylphosphino)-1-cyanoferrocene: a simple ligand with complicated coordination behavior toward copper(I).

1'-(Diphenylphosphino)-1-cyanoferrocene (3), a new donor-asymmetric ferrocene ligand obtained in two steps from 1'-(diphenylphosphino)ferrocene-1-carboxaldehyde, reacts with CuCl at a Cu/3 molar ratio of 1:1 to give the heterocubane complex [Cu(μ3-Cl)(3-κP)]4 (4). When the Cu/3 ratio is changed to 1:2 or 1:3, the reaction takes a different course, producing the P,N-bridged dimer [CuCl(3-κP)(μ(P,N)-3)]2 (5) after crystallization. Notably, CuBr and CuI behave differently, affording the corresponding 2D coordination polymers [CuX(μ(P,N)-3)]n [X = I (7), and Br (8)], regardless of the Cu/3 ratio. Reaction of 3 with sources of naked Cu(+), such as Cu(MeCN)4 salts or their synthetic equivalents, provides the 1D coordination polymer [Cu(MeCN-κN)(μ(P,N)-3)][BF4] (9) or salts of a quadruply bridged dicopper(I) cation, [Cu2(μ(P,N)-3)4]X2 ([10]X2), depending on the Cu/3 molar ratio (1:1 vs 1:2 and 1:3). Except for 4, in which 3 binds as a simple P-monodentate ligand, the complexes reported here represent the first structurally characterized compounds in which a phosphinonitrile ligand coordinates through both of its soft donor moieties, thereby extending the coordination chemistry of these ligands.