Azo Complexes of Osmium(II): Preparation and Reactivity of Organic Azide and Hydrazine Derivatives

Abstract

Mixed-ligand hydride complexes OsHCl(CO)-(PPh 3 ) 2 L (2) [L = P(OMe) 3 , P(OEt) 3 ] were prepared by allowing OsHCl(CO)(PPh 3 ) 3 (1) to react with an excess of phosphite P(OR) 3 in refluxing toluene. Dichloro compounds OsCl 2 (CO)(PPh 3 ) 2 L (3, 4) were also prepared by reacting 1, 2 with HCl.

Ruthenium Complexes for Catalytic Dehydrogenation of Hydrazine and Transfer Hydrogenation Reactions

“…Similarly, hydrazine coordinated Ru‐arene and analogous Os‐arene complexes [( η 6 ‐ p ‐cymene)M{PPh(OEt) 2 }Cl ( κ 1 ‐N 2 H 4 )] + (M=Ru and Os) were also reported to be transformed into corresponding diazene complexes upon treatment with Pb(OAc) 4 at −30 °C . In similar fashion, Os–hydrazine complex [Os(PPh 3 ) 2 {P(OMe) 3 }(CO)Cl(N 2 H 4 )] + was also reported to be synthesized by direct treatment of N 2 H 4 with [OsHCl(CO)(PPh 3 ) 2 {P(OMe) 3 }] in the presence of triflic acid, which can be further oxidized to form corresponding Os‐diazene complex . Interesting to note, that these important intermediates, including those containing N 2 H 4 and N 2 H 2 coordinated Fe complexes provided substantial mechanistic insights on the role of these species in several reactions, such as dehydrogenation reactions.…”

Preparation and reactivity of half-sandwich organic azide complexes of osmium

“…In addition to the resonances of the substituents of the organic azides RN 3 , the 1 H NMR spectra of 1, 2 show the characteristic signals of the ancillary ligands η 5 -C 5 H 5 , PPh 3 , and P(OR1) 3 and of the BPh 4 − anion, in agreement with the half-sandwich geometry shown in Scheme 1. Transition metal complexes containing organic azides RN 3 as ligands are rare [5][6][7][8][9] and only one example is known for osmium, 12 [OsCl(η 1 -N 3 CH 2 Ar)(CO)(PPh 3 ) 2 {P(OR) 3 }]BPh 4 , involving carbonyl and phosphines as the supporting ligands. The use of the half-sandwich fragment [Os(η 5 -C 5 H 5 )(PPh 3 ){P(OR1) 3 }] + Scheme 1 R = CH 2 C 6 H 5 (a), CH 2 C 6 H 4 -4-CH 3 (b), CH(CH 3 )C 6 H 5 (c), C 6 H 5 (d); R1 = Me (1), Et (2).…”

“…9 We have a long-standing interest in the chemistry of diazo and triazo complexes of transition metals and have previously reported on the synthesis and reactivity of the hydrazine, diazene, diazenide, triazene and diazoalkane derivatives of Mn 10 and Fe 11 triads. More recently, we have also given an account of the first benzylazide complexes of iridium(III) 7 and osmium(II) 12 stabilised by phosphites P(OR) 3 or mixed-ligand PPh 3 -P(OR) 3 as the supporting ligands. These studies have now been extended to half-sandwich fragments to test whether stable organic azide complexes can be prepared.…”

Preparation and Reactivity of Mixed‐Ligands Hydride Complexes [RuHCl(CO)(PPh3)2{P(OR)3}]

“…In fact, treatment of the triflate complexes formed by protonation of 2 with an excess of hydrazine afforded the cationic complexes [RuCl(CO)(κ 1 -NH 2 NHR1)(PPh 3 ) 2 {P(OR) 3 quickly reacted with organic azides to give azide derivatives [OsCl(CO)(κ 1 -N 3 R2)(PPh 3 ) 2 {P(OR) 3 }]BPh 4 , which are stable and isolable. [1] The ruthenium fragment, instead, is not able to stabilize azide as a ligand. However, both hydrazine and diethylcyanamide can be stabilized by the carbonyl fragments [RuCl(CO)(PPh 3 ) 2 {P(OR) 3 }] + allowing the preparation of new derivatives.…”

“…Previous reports from our laboratories dealt with studies on the synthesis and reactivity of hydride-carbonyl complexes of osmium [OsHCl(CO)(PPh 3 )L] [L = P(OMe) 3 and P(OEt) 3 ], which allowed the preparation of new organic azide and hydrazine derivatives [OsCl(κ 1 -N 3 R)(CO)(PPh 3 ) 2 L]BPh 4 and [OsCl(CO)(κ 1 -NH 2 NHR)(PPh 3 ) 2 L]BPh 4 . [1] The interesting properties shown by these mixed-ligands carbonyl complexes prompted us to extend study to ruthenium [2] with the aim of testing whether related hydride-carbonyl complexes may be prepared and how they properties change. The results of these studies, which involve the preparation of mixed-ligands hydrazine and diethylcyanamide complexes of ruthenium and the crystallographic structure determination of [RuHCl(CO)-(PPh 3 ) 2 {P(OEt) 3 }], are reported herein.…”