Andreas A. Danopoulos

Amido, imido and carbene complexes of chromium

Abstract Interaction of CrCl2 with LiNHAr∗, Ar ∗ = 2,6- Pr i 2 C 6 H 3 , in thf gave the homoleptic amide CrII (NHAr∗)4 [Li(thf)]2, 1 which resisted further deprotonation by strong bases. Interaction of Cr(Nmes)2Cl2mes = 2,4,6-Me3C6H2, with LiNHmes gave the mesitylimido complex [CrVI(Nmes)3(NHmes)]Li(Et2O)2 (2), which also resisted further deprotonation. Pentamethylcyclopentadienyl chromium(V) complexes Cp ∗ Cr(NAr ′) X 2 , X = SC 6 H 5 , Ar ′ = 2- Pr i C 6 H 4 , (3); 4-Me-C6H4 (4); 2-ButC6H4 (5), have been prepared by interaction of (Cp∗CrBr2)2 with Li(Ar′NSPh). Reaction of (Cp∗CrBr2)2 with mesitylnitrene, generated from mesN3 in situ, gave the ionic CrIII species [Cp∗CrBr3][mesNH3], (6). (3) and (5) as well as the previously reported Cp∗Cr(NBut)X2 can be transformed to the corresponding chlorides (7)–(9), by reaction with BCl3. Finally, interactions of Cr(mes)2(thf)3 with the carbene gave Cr(mes)2L2 (10). The X-ray crystal structures of compounds (1)–(3), (6), (7), (9) and (10) have been determined. (1) is a molecular cluster with square planar CrII and with two [Li(thf)]+ ions bridging the nitrogen atoms of pairs of amide ligands on opposite sides of the square. (2) has a distorted tetrahedral metal geometry with one [Li(Et2O)2]+ ion bridging the nitrogen atoms of two imido ligands. (3) has a monomeric pseudo tetrahedral structure, as do (7) and (9) and the anion in (6). (10) has a trans square planar structure in which the Crue5f8C distances to the mesityl and carbene ligands are equal within error.

t-Butylimido compounds of rhenium. X-ray crystal structures of [(ButN)2Re(μ-NBut)]2, (ButN)2ReCl3, (ButN)2ReCl2C6H5, (ButN)3Re(OSiMe3) and (ButN)3ReCl ☆

Abstract Previous studies on t-butylimido aryls of rhenium have been extended and the compounds (ButN)2RevVII(o-tol)3, (ButN)2ReVIICl2Ph and (BUtN)2ReVI(mes)2 synthesized. Electrochemical studies of the latter show reversible one-electron oxidation and reduction, and chemical oxidation leads to the cation [(ButN)2RevVII(mes)2]+ isolated as PF6− and CF3SO3− salts. Although the neutral complex does not undergo insertion with isocyanides, the cation does so to give η2-iminoacyls, {(ButN)2Re(mes)[η2-RNue5fbC(mes)]}+, R = 2,6-xylyl, t-Bu. Reduction of (ButN)3Re(OSiMe3) in hexane by sodium gives the bridged homoleptic compound (ButN)2Re(μ-NBut)2Re(NBut)2. The homoleptic anion [Re(NBut)4]− as the Li(tmed)+ complex has been synthesized via the new intermediates (ButN)3ReCl and (ButN)3Re(NHBut). X-ray crystal structures of the compounds listed in the title have been determined. The homoleptic rhenium(VI) t-butylimide is dimeric with four-coordinate rhenium and almost symmetrical imido bridges; the terminal imido groups have near linear geometry. The diamagnetism is consistent with a Reue5f8Re bond, although the Reue5f8Re distance of ca 2.7 A indicates this to be weak. The rhenium(VII) siloxide is also four-coordinate distorted tetrahedral; and the geometries of the Re-imido and Re-siloxide units indicate involvement of all ligands in π-interactions. The (ButN)3ReCl is also tetrahedral. The two bis-imido chloro compounds are five-coordinate with a geometry that can be conveniently described as trigonal bipyramidal where the imido groups occupy equatorial sites with unusually small inter-ligand angles of ca 110°.

Synthesis and X-ray crystal structure of trans-bis(2,6-diisopropylphenylimido) bis-(trimethylphosphino)ruthenium(IV): The first structural determination of a terminal imido ruthenium compound

Abstract Interaction of trans -RuCl 2 (PMe 3 ) 4 and Li(2,6-Pr i 2 C 6 H 3 NH) in THF gives an orange solution which, on oxidation by O 2 , gives blue trans -(2,6-Pr i 2 C 6 H 3 N) 2 Ru(PMe 3 ) 2 which has been shown to have a planar structure by X-ray diffraction study.

t-Butylimido complexes of chromium. X-ray crystal structures of Cr(NBut) 2(PMe2Ph)Cl2 and [Cr(NBut)2(C5H4N)2(η1- O3SCF3)]O3SCF3

Abstract The compound Cr(NBut)2Cl2 has been synthesized and converted to Cr(NBut)2(NHBut)Cl, Cr(NBut)2(NHBut)2 and Li2 Cr(NBut)4, the latter completing the series of Group 6 compounds, Li2 M(NBut)4, M = Cr, Mo, W. The five-coordinate adducts, Cr(NBut)2Cl 2L, L = PMe3, PMe2Ph and ButNC, have been characterized as well as [Cr(NBut)2Cl2]2(μ-Ph2PCH2CH2PPh2) and the six-coordinate Cr(NBut)2Cl2(2,2′-bipyridyl). Chloride substitution reactions of Cr(NBut)2Cl2 lead to the compounds, Cr(NBut)2(η1-O 2CMe)2, [Cr(NBut)2(PMe3)2](O3SCF3)2·0.5MeCN, [Cr(NBut) 2py2(η1-O3SCF3)]SO3CF3 and [Cr(NBut)2(bpy)2](PF6) 2. The isocyanide, [Cr(NBut)2Cl2(ButNC)], with MeLi gives the η2-iminoacyl Cr(NBut)2[η2-(ButNue5fbCMe)]Cl. Interaction of Cr(NBut)2Cl2 with alkylating agents at low temperatures gives the chromium(V) dimer [Cl(ButN)Cr(μ-NBut)] 2 in a one-electron per chromium reduction and the same product is obtained by reduction of the dihalide with (η5-C5H5)2Co. X-ray structures of compounds listed in the title have been determined.

Organoimido complexes of tungsten. X-ray crystal structures of W(NC6H11)Cl2(PMe3)3, [W(NC6H11)Cl2(PMe3)3]O3SCF3, [W(NC6H11)Cl(PMe3)4]BPh4, W[NSi(o-MeC6H4)3]Cl2(PMe3)3, W[NB(mes2)]2Cl2(PMe3)2, {W(NPh)Cl[O2C2(CF3)4]2}Li and WCl4(PMe2Ph)3

Abstract The cyclohexylimido complex of tungsten(VI), [W(NCy)Cl4]2 (1), is reduced by Na/Hg in the presence of PMe3 to give cis,mer-WIV(NCy)Cl2(PMe3)3 (2). Interaction of 2 with AgO3SCF3 in THF gives the tungsten(V) complex [W(NCy)Cl2(PMe3)3]O3SCF3(3); with NaBPh4 in the presence of PMe3 [W(NCy)Cl(PMe3)4]BPh4 (4) is obtained. Interaction of WCl2(PMe3)4 with the new organoazide (o-tolyl)3Si(N3) produced W[NSi(o-tolyl)3] Cl2(PMe3)3 (5), while with (mesityl)2B(N3), cis,cis,trans-W[NB(mes)2]2Cl2(PMe3)2 (6) is obtained. Interaction of [W(NPh)Cl4]2 with dilithium perfluoropinacolate gives Li{W (NPh)Cl[O2C2(CF3)4]2} (7). The structures listed in the title have been determined by X-ray crystallographic study. In complexes 2–7 the metal has octahedral geometry. The Wue5f8N(imido) distances vary from 1.69(1) A in complex 4, a tungsten(IV) species, to 1.78(1) A in the tungsten(VI) bis-imido complex 6, with no simple correlation with the oxidation state of the metal. The trans-lengthening effect of the imido function also varies, with the greatest effect generally in the tungsten(V) complex 3. No lengthening seems to occur in the tungsten(IV) complexes 2 and 4, but there is a slight effect in complex 5. The complex WCl4(PMe2Ph)3 has a capped octahedral geometry.

Synthesis and reactions of tert-butylimido complexes of rhenium. X-ray crystal structures of [(ReNBut)2(OSiMe3)]2(μ-O)(μ-OSiMe3)(μ-O2CCF3), Re(NBut)3PPh2 and [Re(NBut)3(NH2But]O3SCF3

Abstract The reactions of Re(NBut)3Cl with NaC5H5, AgX (X = BF4, PF, and CF3CO2) and with SbCl5, lead to the loss of an NButgroup, and the formation of his tert-butylimido compounds, respectively, [Re(NBut)2(η1-C5H5)]2(μ-O)(μ-C5H4), [(ButN)2(Cl)Re(μ-F) (μ-NBut)Re(NBut)(μ-F)]2X (X = BF4 and PF6), [Re(NBut)2]2(μ-OSiMe3)(μ-O2CCF3) and [Re(NBut)2Cl2(MeCN)2]SbCl6. The interaction between Re3(NBut)4(O)5(OSiMe3)3 and AgO2CCF3 produces a species, [Re(NBut)2(OSiMe3)]2(μ-O)(μ-OSiMe3)(μ-O2CCF3), in which the μ-OReO3 group in the starting material is replaced by μ-O2CCF3. Protonation of Re(NBut)3(NHBut) by CF3SO3H produces the cation [Re(NBut)3(NH2Bu)]+ in which the amine can be replaced by PPh3. Reactions of Re(NBut)3X, where X = Cl or OSiMe3 are replaced by NR2, PR2, NPPh3 and C4H3N2, are described. Deprotonation of Re(NBut)3 PH(mes), mes = 2,4,6-Me3C6H2, by ButLi gives the known compound [Re(NBut)2 (μ-NBut)]2 and a new cyclotriphosphane, (Pmes)3. The structures of compounds listed in the title have been determined by X-ray diffraction. The [Re(NBut)2(OSiMe3)]2(μ-O)(μ-OSiMe3)(μ-O2CCF3) structure has crystallographic Cs symmetry with a planar Re2O2 ring; Re … Re separation is 3.25 A. The bridging acetate has a significantly enlarged Oue5f8Cue5f8O angle of 134°. The [Re(NBut)3(NH2But)]O3SCF3 structure has tetrahedral geometry at rhenium with noticeably differing Reue5f8N distances which correlate to the Reue5f8Nue5f8C angles. The Re(NBut)3PPh2 compound has tetrahedral geometry at rhenium and a pyramidal geometry at phosphorus. The Rue5f8P distance is 2.445(2) A.

Imido complexes of molybdenum and tungsten(VI); X-ray crystal structure of cis-(η1-CF3SO3)2 W(NBut)2(NH2But)2

Abstract The synthesis of the homoleptic molybdenum imido compound Li2Mo(NBut)4 is reported. The complexes M (NBut)2(NHBut)2 (M = Mo, W) can be protonated with various strong acids giving neutral species. The X-ray crystal structure of the tungsten complex W (NBut)2(NH2But)2 (SO3CF3)2 confirms the presence of O-coordinated cis- CF3SO3 groups.

Synthesis and X-ray crystal structures of imido and isodiazene complexes of vanadium, niobium and tantalum

Abstract Interaction of [M(NBut)(NHBut)(H2NBut)Cl2]2, M ue5fb Nb, Ta, with five equiv. of ButNHLi gave {[M(NBut)3(NHBut)]Li2}2, M ue5fb Nb (2a), M = Ta (2b), which showed the presence of three different tert-butylimido groups and resisted further metallation. Interaction of MCl5, M ue5fb Nb, Ta, with 1-amino-2,2,6,6-tetramethylpiperidine, C9H18NNH2, in the presence of Me3SiClue5f8Et3N gave (Et3NH)[M(C9H18N2)2Cl4], M ue5fb Nb (3a), M ue5fb Ta (3b). A similar interaction with NH4VO3 gave low yields of [(C9H18N2)2(OSiMe3)2 V(μ-O)V(O)(OsiMe3)2] (4). The X-ray crystal structures of (2a), (3b) and (4) have been determined.

Reactions of bis(mesitylimido)bis(arylthiolato)chromium(VI) compounds

The chromium(VI) imidothiolato complex, Cr(Nmes)2(Smes)2 (1), mes = 2,4,6-Me3C6H2, reacts with 2,6-xylylisocyanide (xylNC) to form the five-coordinate chromium(IV) complex Cr(Nmes)(Smes)2(xylNC)2(2). A similar interaction of Cr(Nmes)2 (SC6H2-2,4,6-Pi3)2 gives only the disulfide adduct Cr(Nmes)2(SC6H2-2,4,6-Pri3)2 · (2,4,6-Pri3C6H2S)2(3). Interaction of 1 and PMePh2 gives Cr4(Nmes)2(μ-Nmes)4(Smes)2(O)2(μ-O)2(4), where the oxygen atoms arise from adventious oxygen during work up. The X-ray crystal structures of 2–4 have been determined. In 2 the CrIV centre has trigonal bipyramidal geometry with axial isocyanides. The CrVI centre in 3 is tetrahedral and 4 is a centro-symmetric tetramer in which the outer CrV centres are tetrahedral and the inner CrIV centres are square-pyramidal.

Homoleptic t-butylimido compounds of osmium(VIII) and chromium(VI)

The homoleptic imido compounds Os(NBut)4 and Li2Cr(NBut)4 have been synthesized, the former by interaction of OsO4 and ButNH(SiMe3) where a tetrameric oxoimido compound Os4(NBut)6(μ-But)4(μ-O)2 is also formed, and the latter by methyllithium deprotonation of Cr(NBut)2(NHBut)2.