Diazo complexes of rhenium: Preparations and crystal structures of the bis(dinitrogen), [Re(N-2)(2){PPh(OEt)(2)}(4)][BPh4] and methyldiazenido [ReCl(CH3N2)(CH3NHNH2){PPh(OEt)(2)}(3)][BPh4] derivatives

Depending on experimental conditions and the nature of the hydrazine, the r eactions of ReCl3P3 [P = PPh(OEt)(2)] with RNHNH2 (R = H, CH3, Bu-t) afford the bis(dinitrogen) [Re(N-2)(2)P-4](+) (2(+)), dinitrogen ReClN2P4 (3), an d methyldiazenido [ReCl(CH3N2)(CH3NHNH2)P-3](+) (1(+)) derivatives. In cont rast, reactions of ReCl3P3 [P = PPh(OEt)(2), PPh2OEt] with arylhydrazines A rNHNH2 (Ar = Ph, p-tolyl) give the aryldiazenido cations [ReCl(ArN2)(ArNHNH 2)P-3](+) (4(+)) and [ReCl(ArN2)P-4](+) (7(+)) and the bis(aryldiazenido) c ations [Re(ArN2)(2)P-3](+) (5(+), 6(+)). These complexes were characterized spectroscopically (IR; H-1 and P-31 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 gro up P (1) over bar: with a = 15.396(5) Angstrom, b = 16.986(5) Angstrom, c = 11.560(5) Angstrom, 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 bonde d 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(N-2)(2){PPh(OEt)(2)}(4)][BPh4] (2) crystallizes in space group Pbaa with a = 23.008(5) Angstrom, b = 23.367(5) Angstrom, c = 12.863(3) An gstrom, and Z = 4. The structure displays octahedral coordination with two end-on N-2 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) Angstrom , b = 20.101(5) Angstrom, c = 19.918(5) Angstrom, 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 ReClN2 P4 (3) reacts with CF3SO3CH3 to give the unstable methyldiazenido derivativ e [ReCl(CH3N2)P-4][BPh4]. Reaction of the methylhydrazine complex [ReCl(CH3 N2)(CH3NHNH2)P-3][BPh4] (1) with Pb(OAc)(4) at -30 degrees C results in sel ective oxidation of the hydrazine, affording the corresponding methyldiazen e derivative [ReCl(CH3N= NH)(CH3N2)P-3][BPh4] (8). In contrast, treatment w ith Pb(OAc)(4) of the related arylhydrazines [ReCl(ArN2)(ArNHNH2)P-3][BPh4] (4) [P = PPh(OEt)(2)] gives the bis(aryldiazenido) complexes [Re(ArN2)(2)P -3][BPh4] (5). Possible protonation reactions of Bronsted acids HX with all diazenides, 1, 4, 5, 6, and 8, were investigated and found to proceed only in the cases o f the bis(aryldiazenido) complexes 5 and 6, affording, with HCl, the octahe dral [ReCl(ArN=NH)(ArN2)P-3][BPh4] or [ReCl{Ar(H)NN}(ArN2)P-3][BPh4] (10) ( Ar = Ph; P = PPh2OEt) derivative.