Preparation and reactivity of half-sandwich hydrazine complexes of ruthenium and osmium
Graphical abstract
The preparation of hydrazine complexes of ruthenium and osmium stabilised by the p-cymene fragment [MCl(η6-p-cymene)L]+ is described. Oxidation with Pb(OAc)4 at −30 °C of [OsCl(η6-p-cymene)(CH3NHNH2)L]BPh4, leading to the methyldiazenido derivative [Os(CH3N2)(η6-p-cymene)L]BPh4, is also reported.
Highlights
► Facile synthesis of half-sandwich hydrazine complexes of Ru and Os. ► Oxidation with Pb(OAc)4 leads to both Ru-acetate and Os-methyldiazenido complexes. ► Reaction of Os-methyldiazenido complexes with HCl affords methyldiazene cations.
Introduction
The chemistry of transition metal complexes containing hydrazine NH2NH2 or substituted hydrazine RNHNH2 as ligands continues to be studied, not only due to interest in the differing coordination modes and interesting reactivity shown by these ligands [1](a), [1](b), [1], [2](a), [2](b), [2], [3], [4](a), [4](b), [4](c), [4](d), [4], but also due to the relationship of hydrazine with the nitrogen fixation process [5](a), [5](b), [5](c), [5](d), [5](e), [5](f), [5], [6](a), [6](b), [6](c), [6](d), [6](e), [6], [7].
Hydrazine is reported to coordinate both η1- and η2- to a metal centre, and may also behave as a bridging μ–η2 ligand [1](a), [1](b), [1], [2](a), [2](b), [2], [3], [4](a), [4](b), [4](c), [4](d), [4]. Coordinated NH2NH2 can either give stable 1,2-diazene complexes [M]–NHNH, by both oxidation [5](a), [5](b), [5](c), [5](d), [5](e), [5](f), [5] and deprotonation with a strong base [4](a), [4](b), [4](c), [4](d), [4], or undergo reduction to ammonia [5](b), [6](a), [6](b), [6](c), [6](d), [6](e), [6], [7](a), [8](a), [8](b), [8]. Hydrazine has also been shown to be a substrate of nitrogenase and has been trapped as an intermediate during enzyme turnover [9], [9](a), [9](b).
A number of hydrazine RNHNH2 complexes of several transition metals have been reported in the past 30 years, mainly with π-acceptors such as carbonyl, phosphine and cyclopentadienyl as ancillary ligands [1](a), [1](b), [1], [2](a), [2](b), [2], [3], [4](a), [4](b), [4](c), [4](d), [4]. Less attention has been devoted to arene ligands and, for the iron triad, only a few examples of hydrazine complexes containing arene as supporting ligand have been reported [10], [10](a), [10](b), [10](c).
We are interested in the chemistry of diazo complexes and have reported the synthesis and reactivity of hydrazine complexes of the iron triad stabilised by phosphite, carbonyl or tris(pyrazolyl)borate ligands, of the type [MH(RNHNH2)L4]+, [M(RNHNH2)2L4]2+, [M(CO)(RNHNH2)L4]2+, [M(Tp)(RNHNH2)L(PPh3)]+ [M = Fe, Ru, Os; Tp = tris(pyrazolyl)borate; L = P(OEt)3, PPh(OEt)2] [11](a), [11](b), [11](c), [11](d), [11](e), [11](f), [11](g), [11](h), [11].
We have now extended these studies with the aim of introducing the arene ligands into the diazo chemistry of the iron triad. In this paper, we report the synthesis and reactivity of new hydrazine complexes of ruthenium and osmium stabilised by the p-cymene ligand.
Section snippets
General comments
All synthetic work was carried out in an appropriate atmosphere (Ar, N2) using standard Schlenk techniques or a vacuum atmosphere dry-box. Once isolated, the complexes were found to be relatively stable in air, but were stored in an inert atmosphere at −25 °C. All solvents were dried over appropriate drying agents, degassed on a vacuum line, and distilled into vacuum-tight storage flasks. RuCl3·3H2O and OsO4 were Pressure Chemical Co. (USA) products, used as received. Phosphites PPh(OEt)2 and
Results and discussion
Half-sandwich dichloro complexes [15] of ruthenium and osmium MCl2(η6-p-cymene)L react with hydrazine NH2NH2 or monosubstituted hydrazines RNHNH2 in the presence of NaBPh4 to give hydrazine derivatives [MCl(η6-p-cymene)(RNHNH2)L]BPh4 (1–6), which were isolated in good yields and characterised (Scheme 1).
Crucial for the separation of compounds 1–6 as solids was the use of equimolar amounts of reagents and starting the reaction at a low temperature. The addition of an excess of hydrazine to the
Conclusions
A facile method for the synthesis of hydrazine complexes of ruthenium and osmium, stabilised by the p-cymene ligand, is reported. Oxidation with Pb(OAc)4 allowed acetate [Ru(κ2–O2CCH3)(η6-p-cymene)L]BPh4 and methyldiazenido complexes [Os(CH3N2)(η6-p-cymene)L}]BPh4 to be prepared. Half-sandwich methyldiazene cations [OsCl(CH3NNH)(η6-p-cymene)L}]+ were also obtained from the reaction of methyldiazenido complexes with HCl.
Acknowledgement
The financial support of MIUR (Rome)-PRIN 2009 is gratefully acknowledge. We thank Mrs. Daniela Baldan, from the Università Ca’ Foscari Venezia, for her technical assistance.
References (42)
Diazo Chemistry II
(1995)et al.- et al.
Angew. Chem. Int. Ed. Engl.
(1989)et al.Inorg. Chem.
(1993)et al.J. Am. Chem. Soc.
(1993)et al.J. Am. Chem. Soc.
(1994)et al.Inorg. Chem.
(1997)et al.Eur. J. Inorg. Chem.
(2000) Data Integration Software Package
(1997)- et al.
J. Organomet. Chem.
(2010) - et al.
Polyhedron
(1989) - et al.
J. Chem. Soc. Chem. Commun.
(1972)et al.J. Organomet. Chem.
(1977)et al.J. Chem. Soc. Dalton Trans.
(1978)et al.J. Chem. Soc. Dalton Trans.
(1978)et al.Inorg. Chim. Acta
(1982) - et al.
Dalton Trans.
(2003)et al.Inorg. Chim. Acta
(2006) Chem. Rev.
(1993)et al.Adv. Organomet. Chem.
(1992)- et al.
Coord. Chem. Rev.
(1996) - et al.
Inorg. Chem.
(2007)et al.Chem. Eur. J.
(2008)et al.Inorg. Chem.
(2009)et al.Inorg. Chem.
(2010)
Chem. Rev.
Acc. Chem. Res.
Coord. Chem. Rev.
Prog. Inorg. Chem.
Chem. Rev.
Chem. Rev.
Chem. Rev.
Crit. Rev. Biochem. Mol. Biol.
Dalton Trans.
Coord. Chem. Rev.
Inorg. Chem.
J. Am. Chem. Soc.
Biochemistry
J. Am. Chem. Soc.
J. Organomet. Chem.
J. Organomet. Chem.
Eur. J. Inorg. Chem.
J. Chem. Soc. Dalton Trans.
J. Chem. Soc. Dalton Trans.
Inorg. Chem.
Inorg. Chem. Commun.
J. Chem. Soc. Dalton Trans.
Inorg. Chem.
Inorg. Chem.
Inorg. Chem.
J. Org. Chem.
Monatsh. Chem.
J. Organomet. Chem.
J. Chem. Soc. Dalton Trans.
Cited by (17)
Synthesis, characterization and behavior in water/DMSO solution of Ru(II) arene complexes with bioactive carboxylates
2018, Journal of Organometallic ChemistryCitation Excerpt :1H NMR: δ/ppm = 7.12–7.03 (m, 4H), 2.80 (hept, J = 6.9 Hz, 1H), 2.23 (s, 3H), 1.15 (d, J = 6.9 Hz, 6H). [ RuCl2(κS-DMSO)(η6-p-cymene)], 7 [16,31,40]. 1H NMR: δ/ppm = 5.79 (d, J = 6.3 Hz, 2H), 5.74 (d, J = 6.3 Hz, 2H), 2.79 (hept, J = 6.9 Hz, 1H), 2.07 (s, 3H), 1.17 (d, J = 6.9 Hz, 6H). [
Half-sandwich hydrazine complexes of iridium: Preparation and reactivity
2018, Inorganica Chimica ActaCitation Excerpt :The IrN distance, 2.1174(16) Å, is shorter than that trans to a phosphine ligand found in the compound [IrCl{PPh2(o-C6H4CO)}2(NH2NHCH3)], 2.150(2) Å [34]. The Ir-N-N angle, 114.96(11)°, is larger than that in 2b, but more acute than that in the last-mentioned compound, 117.46(15) [34], whereas the N-N-C angle, 110.05(16)° is more acute than that expected for a sp2 atom, but is a common value for methylhydrazine, e.g., 110.6(2)°, in the above-mentioned iridium compound and other complexes with differing metals such as [RuCl(NH2NHCH3)(PP3Ph)]+, 110.66(14)° [35], [RuTp(NH2NHCH3){P(OEt)3}(PPh3)]+, 110.8(4)° [36] or [ReCl(N2CH3)(NH2NHCH3){PPh(OEt)2}3]+, 108.8(3)° [37]. Once again, [IrCl{PPh2(o-C6H4CO)}2(NH2NHCH3)], 2.150(2) Å [34] is, to the best of our knowledge [33], the only methylhydrazine iridium compound which has been characterised crystallographically.
Preparation of half-sandwich azine complexes of osmium
2017, PolyhedronThe dominant steric effect in the synthesis of ammine hydrido- and chlorido-Ru(II)-N,N-dimethylhydrazine and mixed alkyl-aryl phosphine complexes: Novel methyldiazene reduction intermediates
2015, Inorganica Chimica ActaCitation Excerpt :An extensive range of stable cationic and neutral ruthenium(II) species containing the hydrazine ligands NH2NHR (R = H, Me) have been reported, and primarily includes complexes with carbonyl [1e,6b], phosphine and phosphite [1e,2a,6,14,10,15,16a], 1,5-cyclooctadiene [2b,16], cyclopentadienyl [17d,18], and p-cymene ancillary ligands [6a]. The pioneering work of Singleton et al. throughout 1977–1987, who reported the synthetic and catalytically active complexes [CpRuX(cod)] (X = H, Cl, Br) [18c] and the first metallacyclopentatriene complex [CpRu(C4Ph2H2)] [18a,18b], all emanated from the use of the Ru(II) complexes of [RuH(1,5-cod)(NH2NHR)3](X) (R = H, Me; X = PF6, BPh4) as precursors [16,17d,19]. These catalytically important Ru–H complexes were found to be reactive precursors to a range of allyl- and cyclooctadiene ruthenium(II) species which has significance in hydride transfer reactions [16,17,20–21].
Hydrazine complexes of ruthenium with cyclopentadienyl and indenyl ligands: Preparation and reactivity
2014, Journal of Organometallic ChemistryPreparation of diethylcyanamide and cyanoguanidine complexes of manganese and rhenium
2014, Journal of Organometallic ChemistryCitation Excerpt :Complex 7a shows two Re–N(cyanamide) bond lengths of 2.142(3) and 2.138(3) Å, trans to a carbonyl ligand. Although these values are longer than that of the Re(II) complex mer-ReCl2(NCNEt2)P3, they are comparable to other trans carbonyl-nitrile Re(I) complexes, like the values of 2.145(7) Å in [Re(N,N′-terpy)(CO)3(CH3CN)]PF6 [34] or 2.151(7) Å in [Re(CO)3(CH3CN){H(pzAnMe)}]PF6 [35]. As in 2a (see above) or other N,N-diethylcyanamide complexes [1,] these ligands have average C–N–Re bond angles of 172.7(3)° and a N–C–N bond angles of 177.5(4)°.