Synthesis and properties of iron-group hydrido-cyano complexes trans-[MH(CN)(L)2], M = Fe, Ru or Os, L = diphosphine, and their hydrogen, trifluoroboron and triphenylboron isocyanide derivatives of the type trans-[MH(CNH)(L)2]O3SCF3, trans-[MH(CNBX3)(L)2], X = F or Ph, and trans-[M(H2)(CNBF3)(dppp)2]BF4 [dppp = Ph2P(CH2)3PPh2]

Complexes trans-[MH(CN)L2] 1 {L = PPh2(CH2)nPPh2, n = 1 (dppm), 2 (dppe) or 3 (dppp), and PR2CH2CH2PR2, R = Et (depe) or para-tolyl (dtpe), M = Fe (for dppe, depe and dtpe only), Ru or Os} were prepared by displacing with cyanide the halide from trans-[MH(X)L2], X = Br or Cl, or dihydrogen from trans-[Ru(H2)H(dppe)2]BPh4. Systematic trends in the IR and 1H, 31P and 13C NMR and electrochemical properties are noted. The addition of one equivalent of HOTf (HO3SCF3) or [HPPh3]OTf to trans-[MH(CN)L2] 1 with n = 1, 2 or 3 usually produces the hydrogen isocyanide complexes trans-[MH(CNH)L2]OTf 2. The use of 13CN− or C15N− in compounds 1 provides evidence for the MCNH coordination mode over MNCH. Protonation at the M–H bond to give dihydrogen complexes trans-[M(H2)(CN)L2]+ occurs to a small degree for M = Ru, n = 1 or 3, in CH2Cl2 and completely for M = Os, L = depe. The use of HBF4· Et2O results in a variety of products including trans-[MH(CNH)L2]BF42*, trans-[MH(CNBF3)L2] and trans-[M(H2)(CNBF3)L2]+. The dihydrogen ligand in the last compound with M = Ru, L = dppp, is readily replaced by η1-BF4−. Structures of the compounds 2 (M = Ru, L = dppe), trans-[RuH(CNBF3)(dppe)2] and 2* (M = Os, L = dppe) are reported. The CNH ligand is a good hydrogen-bond donor so that NH⋯O or NH⋯F hydrogen bonds with the counter ion are formed. The reaction of BPh4− with the CNH ligand of 2 (M = Ru, L = dppe) produces trans-[Ru(H)(CNBPh3)(dppe)2], the structure of which is reported. Therefore the CNH ligand reacts readily with BX4− (X = F or Ph) to produce CNBX3− ligands and HX.