Diazo Complexes of Rhenium:  Preparations and Crystal Structures of the Bis(dinitrogen), [Re(N₂)₂{PPh(OEt)₂}₄][BPh₄] and Methyldiazenido [ReCl(CH₃N₂)(CH₃NHNH₂){PPh(OEt)₂}₃][BPh₄] Derivatives

Abstract

Depending on experimental conditions and the nature of the hydrazine, the reactions of ReCl3P3 [P = PPh(OEt)2] with RNHNH2 (R = H, CH3, tBu) afford the bis(dinitrogen) [Re(N2)2P4]+ (2+), dinitrogen ReClN2P4 (3), and methyldiazenido [ReCl(CH3N2)(CH3NHNH2)P3]+ (1+) derivatives. In contrast, reactions of ReCl3P3 [P = PPh(OEt)2, PPh2OEt] with arylhydrazines ArNHNH2 (Ar = Ph, p-tolyl) give the aryldiazenido cations [ReCl(ArN2)(ArNHNH2)P3]+ (4+) and [ReCl(ArN2)P4]+ (7+) and the bis(aryldiazenido) cations [Re(ArN2)2P3]+ (5+, 6+). These complexes were characterized spectroscopically (IR; 1H and 31P NMR), and the BPh4 complexes 1, 2, and 7 were characterized crystallographically. The methyldiazenido derivative [ReCl(CH3N2)(CH3NHNH2)(PPh(OEt)2)3][BPh4] (1) crystallizes in space group P1 with a = 15.396(5) A, b = 16.986(5) A, c = 11.560(5) A, alpha = 93.96(5) degrees, beta = 93.99(5) degrees, gamma = 93.09(5) degrees, and Z = 2 and contains a singly bent CH3N2, group bonded to an octahedral central metal. One methylhydrazine ligand, one Cl- trans to the CH3N2, and three PPh(OEt)2 ligands complete the coordination. The complex [Re(N2)2(PPh(OEt)2)4][BPh4] (2) crystallizes in space group Pbaa with a = 23.008(5) A, b = 23.367(5) A, c = 12.863(3) A, and Z = 4. The structure displays octahedral coordination with two end-on N2 ligands in mutually trans positions. [ReCl(PhN2)(PPh(OEt)2)4][BPh4] (7) crystallizes in space group P2(1)/n with a = 19.613(5) A, b = 20.101(5) A, c = 19.918(5) A, beta = 115.12(2) degrees, and Z = 4. The structure shows a singly bent phenyldiazenido group trans to the Cl- ligand in an octahedral environment. The dinitrogen complex ReClN2P4 (3) reacts with CF3SO3CH3 to give the unstable methyldiazenido derivative [ReCl(CH3N2)P4][BPh4]. Reaction of the methylhydrazine complex [ReCl(CH3N2)(CH3NHNH2)P3][BPh4] (1) with Pb(OAc)4 at -30 degrees C results in selective oxidation of the hydrazine, affording the corresponding methyldiazene derivative [ReCl(CH3N=NH)(CH3N2)P3][BPh4] (8). In contrast, treatment with Pb(OAc)4 of the related arylhydrazines [ReCl(ArN2)(ArNHNH2)P3][BPh4] (4) [P = PPh(OEt)2] gives the bis(aryldiazenido) complexes [Re(ArN2)2P3][BPh4] (5). Possible protonation reactions of Brønsted acids HX with all diazenides, 1, 4, 5, 6, and 8, were investigated and found to proceed only in the cases of the bis(aryldiazenido) complexes 5 and 6, affording, with HCl, the octahedral [ReCl(ArN=NH)(ArN2)P3][BPh4] or [ReCl(Ar(H)NN)(ArN2)P3][BPh4] (10) (Ar = Ph; P = PPh2OEt) derivative.

Preparation and Reactivity of Hydridorhenium Complexes with Polypyridine and Phosphonite Ligands

“…The Re–N [2.172(10) and 2.180(9) Å] and Re–Cl [2.450(3) Å] bond lengths are slightly longer than those found for other octahedrally coordinated complexes,13 as expected due to the increase in coordination number. The Re–P bond lengths range from 2.286(3) to 2.365(3) Å and are slightly shorter than those found in the cationic complex [ReCl(PhN 2 ){PPh(OEt) 2 } 4 ]BPh 4 ,14 the only example of a complex containing both Re III and a phosphonite PPh(OEt) 2 ligand found in the CCDC (version 5.27, update August 2006) 15. This shortening is due to the pseudo trans effect exerted by the nitrogen or chlorine atoms in the heptacoordinate complex when compared with the cited octahedral cation, which has the phosphonite ligands mutually trans .…”

Preparation and reactivity of diazoalkane complexes of ruthenium stabilised by an indenyl ligand

“…18 Coordination of the diazoalkane ligand in 3c shows a severely "bent" configuration, with a N(2)-N(1)-Ru bond angle of 150.5(2)°. Note that this angle is more acute than that found in Cp diaryldiazoalkane Ru complex [Ru(Cp)P 1 P 2 {NNC(Ph)-Tol}] [156.0(1)°], 13a or even in the 9-diazofluorene one [RuCl 2 {NNC (C 12 21 It should be noted that the N(1)-N(2)-C(11) bond angle is 171.2(3)°, revealing a sp character on the N(2) atom, quite different from the usual sp 2 geometry [about 120°] around this atom found in aryldiazenido compounds, 22 The bond distances at the diazenido moiety, Ru-N(1) of 1.990(2), N(1)-N(2) of 1.154(3) and N(2)-C(11) of 1.299(3) Å, are virtually the same values as those found in the abovementioned 9-diazofluorene ruthenium complex [RuCl 2 {NNC- (C 12 H 8 )}(PNP)], or in [Ru(Cp)P 1 P 2 {NNC(Ph)Tol}] + , in such a way that a double bond between the nitrogen atoms and also between N(2) and C(11) may be proposed. Due the multiple character of the Ru-N bond, its length is shorter than that found in nitrile complexes, like [Ru(Cp)(NCPh)P 1 P 2 ], 23 2.029(2) Å, or in other ruthenium benzonitrile complexes, average 2.033 Å.…”

Synthesis, characterization and solid‐phase extraction properties of novel bis(diazo‐azomethine) ligands supported on mesoporous silica

“…A modified method from the literature was applied for the synthesis of bis (diazo‐carbonyl) compounds, A1 and A2. For the characterization of these compounds, 1 H‐ and 13 C–NMR, FT‐IR, TG/DTA, elemental analysis, UV–Vis and LC–MS (ESI) techniques were used.…”

“…The carbonyl carbons signals were at about 190 ppm. The resonances of the phenolic carbons were recorded at about 132 ppm and 130 ppm for A1 and A2, respectively …”

“…Because of the excellent electrophilic properties of diazonium cations, which are the substantial coupling intermediates, they can be used in the obtaining of compounds . Numerous studies have been published about mono‐aryldiazonium salts ArN 2 + ; however, novel synthetic derivatives and applications of bis (aryldiazo) compounds have not been sufficiently reported . Chemically modified mesoporous solids such as silica‐gel have been widely used in catalysis, solid‐phase extraction, optical and electronic applications.…”