Imide Ligands Research Articles

Anionic and cationic Bi- and tri-nuclear tert-butylimido complexes of manganese-(V) and -(VI)

Dimeric anionic complexes have been obtained by reduction of MnCl(NBut)3 or [Mn(NBut)2(µ-NBut)]21 with lithium powder in 1,2-dimethoxyethane (dme) to give [Li(dme)]2[{Mn(NBut)2(µ-NBut)}2]2, or with sodium amalgam in tetrahydrofuran (thf) to give [Na(thf)][{Mn(NBut)2(µ-NBut)}2]3 which have oxidation states V,V and V,VI respectively. Interaction of 1 with iodine gave a mixed-valence (VI,V,VI) compound, [{Mn(NBut)2(µ-NBut)2}2Mn]I34. Interaction of 3 with HgCl2 gave [{Mn(NBut)2(µ-NBut)2}2Mn]2[Hg2Cl6]·2CHCl35a and [(ButN)2Mn(µ-NBut)2Mn(NHBut)(NBut)]2[Hg3Cl8]5b. Oxidation of 1 by silver trifluoromethanesulfonate resulted in an unisolable cation in CH2Cl2, presumably [{Mn(NBut)2(µ-NBut)}2]+, the EPR spectrum of which suggests that the single electron is located on one N atom of the terminal imide groups. The interaction of this cation with thf resulted in abstraction of H to give the manganese(VI) amido species [(ButN)(ButNH)Mn(µ-NBut)2Mn(NBut)2]+ which is also formed on protonation of 1 with stoichiometric amounts of CF3SO3H. The amido cation has been isolated with the anions CF3SO3–6 and [B(C6F5)4]–7, but use of [B{C6H3(CF3)2-3,5}4]– produces, after crystallisation from toluene, the salts of the amido cation 8 and of an oxo species [Mn3(µ-O)(µ-NBut)4]+9. Interaction of [{Mn(NBut)2(µ-NBut)}2]+in situ with dry O2 gave a mixture 10 of [{(ButN)2Mn(µ-NBut)2}2Mn]+ and [{(ButN)2Mn(µ-O)(µ-NBut)}2Mn]+ which cocrystallise and cannot be separated. Thermal decomposition of the alkoxide Mn(NBut)3[OCH(CF3)2] gave the manganese(V) dimer [Mn(NBut)(NHBut)(µ-NBut)]2. The structures of compounds 3, 4, 5a, 5b, 7, 9 and the mixture 10 have been confirmed by single-crystal X-ray studies. In all cases the Mn atoms have distorted-tetrahedral geometry. The Mn–N bonds to terminal imide ligands lie in the range 1.554–1.674 A, whilst bridging distances vary considerably from 1.724 to 1.872 A, reflecting differences for Mn atoms which are co-ordinated only by bridging imides and those which are also bonded to terminal ligands. The Mn–O bonds in the oxo-bridged species are slightly longer than the analogous Mn–N (bridging) distances, indicating less multiple bonding. The structure of the [Hg3Cl8]2– ion in 5b shows it to conform quite closely to the ‘composite’ species [(Cl2Hg)(Cl2HgCl2)(HgCl2)]2–

Synthesis and characterization of organoimido- and organoamido-rhenium(V) complexes. Crystal structures of [ReCl2(NC6H4PPh2-2)(HNC6H4PPh2-2)], [Re(8-HNC9H6N)2O(PPh3)][BPh4] and [Re(NPh)(NC5H3S-2-SiMe3-3)2(PPh3)][BPh4

The reaction of [ReCl3O(PPh3)2] in toluene with 2-diphenylphosphinoaniline yielded the brown rhenium(V) amido/imido-complex [ReCl2(NC6H4PPh2-2)(HNC6H4PPh2-2)]1. This represents the first example of a metal complex where a 2-aminophenylphosphine is fully deprotonated to give an N,P chelated imido-complex. The crystal structure of 1 shows a distorted-octahedral geometry with the imido-nitrogen trans to chloride whereas the amido-nitrogen is disposed trans to a phosphorus. The Re–N length of 1.988(4)A for the amido nitrogen is consistent with protonation of the nitrogen in the chelated ligand. A Re–N bond length of 1.757(4)A and a Re–N–C angle of 137.8(3)° for the deprotonated imide nitrogen imply substantial multiple bonding. The oxo-complex [Re(8-HNC9H6N)2O(PPh3)][BPh4]2 was the unexpected product in the reaction of [ReCl3O(PPh3)2] with 8-aminoquinoline in ethanol. It has a distorted-octahedral structure with two chelated amide ligands. The two quinoline-ring nitrogens as well as the two amido-nitrogens are arranged in a mutually cis configuration. The oxo and triphenylphosphine ligands occupy the remaining co-ordination sites. Reaction of [ReCl3(NPh)(PPh3)2] in ethanol with the sterically hindered 3-trimethylsilylpyridine-2-thiol (Htspyt) yielded the green rhenium(V) phenylimido-complex [Re(NPh)(PPh3)(tspyt)2][BPh4]3. Reaction of the unsubstituted pyridine-2-thiol (Hpyt) with the parent imido-complex yielded the analogous complex [Re(NPh)(PPh3)(pyt)2][BPh4]4. The crystal structure of 3 reveals a distortedoctahedral configuration of the ligands about the central rhenium atom. The imide and phosphine ligands are cis with the remaining sites being occupied by the S,N chelated pyridinethiolate ligands. A ReN bond length of 1.725(8)A and a Re–N–C bond angle of 166.0(6)° are indicative of the imide ligand functioning as a four-electron donor.

Metallcarbonyl-Komplexe mit Anionen von cyclischen Imiden / Metal Carbonyl Complexes with Anions of Cyclic Imides

A large series of metal carbonyl complexes with N -bonded anions of various cyclic imidates (X-) has been prepared: [M(CO)5X]-, [M(CO)4(PPh3)X], [M(CO)3(en)X]- (M = Cr, Mo, W), Re(CO)5X , [π-CH3C5H4Mn(CO)2X]-, [Mn(CO)4X2]-. Also pyromellitdiimidate and cyclopentanebis(dicarboximidate) bridged complexes [(OC)5MXM(CO)5]2- (M = Cr, Mo, W) and the dicyanamide complex [π-(C5H5)Mn(CO)2NCNCN]- have been obtained. Reactions at the coordinated imidate ligands and the spectroscopic data of the complexes are reported.