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(H-2)(CNBF3)-(dppp)(2)]BF4 [dppp = Ph2P(CH2)(3)PPh2]

Complexes trans-[MH(CN)L-2] 1 {L = PPh2(CH2)(n)PPh2, 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)L-2], X = Br or Cl, or dihydrogen from trans-[Ru(H-2)H(dppe)(2)]BPh4. Systematic trends in the IR and H-1, P-31 an d C-13 NMR and electrochemical properties are noted. The addition of one eq uivalent of HOTf (HO3SCF3) or [HPPh3]OTf to trans-[MH(CN)L-2] 1 with n = 1, 2 or 3 usually produces the hydrogen isocyanide complexes trans-[MH(CNH)L- 2]OTf 2. The use of (CN-)-C-13 or (CN-)-N-15 in compounds 1 provides eviden ce for the MCNH coordination mode over MNCH. Protonation at the M-H bond to give dihydrogen complexes trans-[M(H-2)(CN)L-2](+) occurs to a small degre e for M = Ru, n = 1 or 3, in CH2Cl2 and completely for M = Os, L = depe. Th e use of HBF4. Et2O results in a variety of products including trans-[MH(CN H)L-2]BF4 2*, trans-[MH(CNBF3)L-2] and trans-[M(H-2)(CNBF3)L-2](+). The dih ydrogen ligand in the last compound with M = Ru, L = dppp, is readily repla ced by eta(1)-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 liga nd is a good hydrogen-bond donor so that NH ... O or NH ... F hydrogen bond s with the counter ion are formed. The reaction of BPh4- with the CNH ligan d of 2 (M = Ru, L = dppe) produces trans-[Ru(H)(CNBPh3)(dppe)(2)], the stru cture of which is reported. Therefore the CNH ligand reacts readily with BX 4- (X = F or Ph) to produce CNBX3- ligands and HX.