Preparation and reactivity towards hydrazines of bis(cyanamide) and bis(cyanoguanidine) complexes of the iron triad

Bis(diethylcyanamide) [Fe(N CNEt2)(2)L-4](BPh4)(2) 1a and bis(cyanoguanidine) [Fe{N CN(H)C(NH2)- NH}(2)L-4](BPh4)(2) 1b [ L = P(OEt)(3)] complexes were prepared by allowing iron(II) chloride to react first with an excess of P(OEt) 3 and then of the appropriate cyanamide, followed by addition of an excess of NaBPh4. Instead, bis(complexes) of ruthenium and osmium [ M(N=CNEt2)(2)L-4](BPh4) (2) 2a, 3a and [M{N=CN(H)C-NH2) =NH}(2)L-4](BPh4)(2) 2b, 3b (M = Ru 2, Os 3) were prepared by reacting hydrides MH2L4 first with either triflic acid HOTf or methyltriflate MeOTf and then with an excess of the appropriate cyanamide. Hydridediethylcyanamide [MH(N=CNEt2)L-4] BPh4 4a, 5a and hydride-cyanoguanidine complexes [MH{N=CN(H)-C(NH2) -NH} L-4](BPh4)(2) 4b, 5b (M = Ru 4, Os 5) were also obtained by reacting MH2L4 first with one equivalent of HOTf or MeOTf and then with the appropriate cyanamide. Treatment of bis(cyanamide) and bis(cyanoguanidine) complexes 1-3 with hydrazines RNHNH2 afforded hydrazinecarboximidamide derivatives [ M{ eta(2)-N(H) =C(NEt2) N(R) NH2}L-4](BPh4)(2) 6a-12a and [M{. eta(2)-N(H) =C[ N=C(NH2)(2)] N(R) NH2} L-4](BPh4)(2) 6b-12b (M = Fe 6-8, Ru 9, 10, Os 11, 12; R = H 6, 9, 11, Me 7, 10, 12, Ph 8). A reaction path involving nucleophilic attack by hydrazine on the cyanamide carbon atom is proposed. All the complexes were characterised by spectroscopy and X-ray crystal structure determination of [Os{eta(2)-NH=C[NC(NH2)(2)]N(CH3) NH2}{P(OEt)(3)} (4)](BPh4)(2) 12b.