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

Dalton Transactions Pub Date: 2014-04-02 DOI: 10.1039/C4DT00394B

Abstract

Bis(diethylcyanamide) [Fe(N[triple bond, length as m-dash]CNEt2)2L4](BPh4)21a and bis(cyanoguanidine) [Fe{N[triple bond, length as m-dash]CN(H)C(NH2)[double bond, length as m-dash]NH}2L4](BPh4)21b [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[triple bond, length as m-dash]CNEt2)2L4](BPh4)22a, 3a and [M{N[triple bond, length as m-dash]CN(H)C(NH2)[double bond, length as m-dash]NH}2L4](BPh4)22b, 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. Hydride-diethylcyanamide [MH(N[triple bond, length as m-dash]CNEt2)L4]BPh44a, 5a and hydride-cyanoguanidine complexes [MH{N[triple bond, length as m-dash]CN(H)C(NH2)[double bond, length as m-dash]NH}L4](BPh4)24b, 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{η2-N(H)[double bond, length as m-dash]C(NEt2)N(R)NH2}L4](BPh4)26a–12a and [M{η2-N(H)[double bond, length as m-dash]C[N[double bond, length as m-dash]C(NH2)2]N(R)NH2}L4](BPh4)26b–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{η2-NH[double bond, length as m-dash]C[N[double bond, length as m-dash]C(NH2)2]N(CH3)NH2}{P(OEt)3}4](BPh4)212b.

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