Carlo Guastini

Decamethylvanadocene chemistry: synthesis, structure, and reactions of vanadium(II) and vanadium(III) derivatives with carbon monoxide and isocyanides

Determination des structures cristallines des composes (cp*) 2 V (avec cp*=η 5 -C 5 Me 5 ), (cp*) 2 V(CO), (cp*) 2 V(CN)(CNC 6 H 11 ) et (cp*) 2 V(CN). Spectres IR et moments magnetiques

cis- and trans-Dichloro-derivatives of six- and seven-co-ordinate zirconium and hafnium bonded to quadridentate Schiff-base ligands. Crystal structures of [Zr(acen)Cl2(thf)], [M(salphen)Cl2(thf)]·0.5thf, [M(acen)Cl2], (M = Zr or Hf), and [Zr(msal)Cl2][acen =N,N′-ethylenebis(acetylacetoneiminate), salphen =N,N′-o-phenylenebis(salicylideneiminate), msal =N-methylsalicylideneiminate, and thf = tetrahydrofuran]

The reaction of MCl4·2thf (thf = tetrahydrofuran) with the sodium salt of quadridentate Schiff bases [L =N,N′-ethylenebis(acetylacetoneiminate)(acen), N,N′-ethylenebis(salicylideneiminate)(salen), N,N′-ethylenebis(α-methylsalicylideneiminate)(dmsalen), or N,N′-o-phenylenebis(salicylideneiminate)(salphen)] yields the complexes [MLCl2(thf)]. X-Ray analyses showed for all of them that the metal ion is seven-co-ordinate with a pseudo-pentagonal bipyramidal geometry. Details of the structures of [Zr(acen)Cl2(thf)](5), [Zr(salphen)Cl2(thf)]·0.5thf (10), and of the corresponding isostructural hafnium complex [Hf(salphen) Cl2(thf)]·0.5thf (11) are reported. The equatorial plane of the bipyramid is defined by the N2O2 donor atoms and by the oxygen atom from thf, while the two chlorine atoms are trans to each other [Cl–Zr–Cl 169.1 (1), (5); 165.2(1), (10); Cl–Hf–Cl 166.3(1)°, (11)]. Recrystallization of the seven-co-ordinate complexes from toluene removed the thf leading to six-co-ordinate complexes. The structural determination of the isostructural [Zr(acen)Cl2](12) and [Hf(acen)Cl2](13) showed the six-co-ordination of the metal with the two chlorines assuming a cis arrangement [Cl–Zr–Cl 87.2(1), (12); Cl–Hf–Cl 87.4(1)°, (13)]. Bond lengths within the co-ordination sphere are significantly shorter in the six-co-ordinate complexes. The cis and trans isomers do not interconvert in solutions of non-co-ordinating solvents, i.e. C6H6 or CH2Cl2, as shown by their distinctive 1H n.m.r. spectra. In the absence of geometrical constraints zirconium(IV) prefers six-co-ordination and a cis arrangement of the chloride ligands. This was confirmed by synthesizing [Zr(msal)2Cl2](15)(msal =N-methylsalicylideneiminate), [Cl–Zr–Cl 97.9(1)°] containing a bidentate Schiff-base ligand. Its crystallization from thf gave the unsolvated six-co-ordinated form. Crystallographic details: complex (5), space group P, a= 8.401 (1), b= 15.987 (2), c= 7.805(1)A, α= 98.41 (1), β= 90.32(1), γ= 76.65(1)°, Z= 2, and R 0.042 for 3 713 observed reflections; (10), space group P, a= 12.759(2), b= 13.332(2), c= 7.587(1)A, α= 91.60(2), β= 98.45(1), γ= 85.30(1)°, Z= 2, and R 0.033 for 3 813 observed reflections; (11), space group P, a= 12.737(7), b= 13.269(7), c= 7.564(4)A, α= 91.48(1), β= 98.56(1), γ= 85.26(1)°Z= 2, and R 0.027 for 4 227 observed reflections; (12), space group P21/n, a= 24.150(5), b= 9.160(2), c= 7.282(1)A, β= 90.90(1)°, Z= 4, and R 0.034 for 1 894 observed reflections; (13), space group P21/n, a= 24.096(10), b= 9.161 (4), c= 7.262(3)A, β= 90.87(1)°, Z= 4, and R 0.024 for 2 124 observed reflections; (15), space group P, a= 13.024(3), b= 14.522(3), c= 9.797(2)A, α= 90.10(1), β= 93.14(1), γ= 96.09(1)°, Z= 4, and R 0.044 for 3 294 observed reflections.

Polydentate ligand exchange via formation of a dimetallic complex. Crystal structures of [(thf)Fe(acen)MCl2](M = Fe or Zn), [ClFe(salphen)FeCl(thf)2], [Ti(acen)(thf)2][CoCl3(thf)], and [Ti(acen)(thf)2]2[Fe3Cl8(thf)2][acen =N,N′-ethylenebis(acetylacetoneiminate), salphen =N,N′-o-phenylenebis(salicylideneiminate), and thf = tetrahydrofuran]

Complexation of metal halides M′Cln by square-planar Schiff-base complexes, i.e. ML [M = Fe, Co, Ni, or Cu; L = acen =N,N′-ethylenebis(acetylacetoneiminate), salen =N,N′-ethylenebis(salicylideneiminate), or salphen =N,N′-o-phenylenebis(salicylideneiminate)] led to adducts which are intermediates in the exchange of the quadridentate ligand between M and M′. Exchange occurs if M′ is in an higher oxidation state than M. Concomitant redox and ionization reactions are observed. Reaction of [Fe(acen)], (1) with MCl2·nthf (M = Fe or Zn) led to the bimetallic adducts [(thf)Fe(acen)MCl2[M = Fe, (2); Zn, (3)] containing a square-pyramidal iron, while M has a tetrahedral co-ordination geometry. A complex analogous to (2), [ClFe(salphen)FeCl(thf)2](4)(thf = tetrahydrofuran), was obtained by treating FeCl2·1.5 thf with H2 salphen in a 2:1 molar ratio in the presence of Na(OMe). This reaction gave some insight into the ligand-exchange pathway. The reaction of [M(acen)](M = Fe, Co, or Ni) complexes with TiCl4·2thf in thf led to migration of the acen ligand to titanium and formation of [Ti(acen)Cl2], (7) and the corresponding metal halide MCl2·nthf. Related results have been obtained in the reaction of [M(acen)] and TiCl3·3thf. When M = Ni or Cu complex (7) was obtained by exchange of the acen ligand and oxidation of titanium(III) by the corresponding metal halides. In the absence of a redox reaction, complexes of titanium (III) have been obtained: [Ti(acen)(thf)2][CoCl3(thf)], (10), and [Ti(acen)(thf)2]2[Fe3Cl8(thf)2], (11), respectively. The structures of complexes (2)–(4), (10), and (11) have been determined by X-ray analysis: (2) space group P, a= 14.029(2), b= 9.854(1), c= 8.092(1)A; α= 98.48(1), β= 90.96(1), γ= 107.44(1)°, Z= 2, and R= 0.065 for 1 360 observed reflections; (3), space group P, a= 14.006(3), b= 9.823(2), c= 8.077(2)A, α= 98.49(1), β= 90.90(1), γ= 107.57(1)°Z= 2, and R= 0.072 for 2 347 observed reflections; (4), space group P21/c, a= 12.882(2), b= 11.940(2), c= 21.701 (3)A, β= 95.40(1)°, Z= 4, R= 0.054 for 1991 observed reflections; (10), space group P, α= 12.735(3), b= 15.105(3), c= 8.935(2)A, α= 95.30(2), β= 94.26(2), γ= 67.91 (2)°, Z= 2, and R= 0.055 for 2 576 observed reflections; (11), space group P, α= 14.109(3), b= 14.713(3), c= 9.203(2)A, α= 99.98(2), β= 104.76(2), γ= 63.08(2)°Z= 1 for C48H84Cl8Fe3N4O10Ti2 formula unit, and R= 0.050 for 2 685 observed reflections.

Synthesis of cis-[Pt(CCr)2(PPh3)2] and trans-[PtCl(CCR)(PPh3)2] complexes. Crystal and molecular structures of cis-[Pt{CCC(OH)Me2}2(PPh3)2]·H2O, trans-[PtCl{CCC(OH)Me2}(PPh3)2]·0.5PhMe, and trans-[PtCl{CCC(OH)MeEt}(PPh3)2]·Me2CO. Influence of bases and their concentration on the reactivity of cis-[PtCl2(PPh3)2]

Complexes cis-[Pt(CCR)2(PPh3)2][R = C(OH)Me2, C(OH)MeEt, CH(OH)Ph, or Ph] can be obtained from cis-[PtCl2(PPh3)2] and HCCR in 30% aqueous ammonia as solvent. Complexes trans-[PtCl(CCR)(PPh3)2][R = CH2OH, CH(OH)Me, C(OH)Me2, C(OH)MeEt, C6H10OH, or CH2NEt2] are obtained by using chloroform (or dichloromethane)–diethylamine as solvent. No dehydration reactions of the acetylenic alcohols are observed. X-Ray analyses on cis-[Pt{CCC(OH)Me2}2(PPh3)2]·H2O, trans-[PtCl{CCC(OH)Me2}(PPh3)2]·0.5PhMe, and trans-[PtCl{CCC(OH)MeEt}(PPh3)2]·Me2CO revealed in the, cis complex the presence of a water molecule forming two strong hydrogen bonds with the two cis-oriented hydroxy-groups of the acetylide ligands. In all the complexes the co-ordination around platinum is distorted square planar with the acetylide ligands σ-bonded to platinum. Crystallographic details: cis-[Pt{CCC(OH)Me2}2(PPh3)2]·H2O, monoclinic, space group P21/c, with a= 15.473(5), b= 21.725(6), c= 13.439(4)A, β= 113.95(3)°, and Z= 4; R= 0.052 for 3 110 observed reflections; trans-[PtCl{CCC(OH)Me2}(PPh3)2]·0.5PhMe, triclinic, space group P, with a= 11.695(3), b= 19.690(6), c= 9.214(2)A, α= 101.88(3), β= 104.26(3), γ= 85.55(3)°, and Z= 2; R= 0.053 for 3 961 observed reflections; [PtCl{CCC(OH)MeEt}(PPh3)2]·Me2CO, triclinic, space group P, with a= 15.544(6), b= 12.567(4), c= 11.719(3)A, α= 91.12(3), β= 105.36(3), γ= 111.39(3)°, and Z= 2; R= 0.046 for 4 704 observed reflections. The influence of NH3, NHEt2, and H2NNH2 on the reactivity of cis-[PtCl2(PPh3)2] with monosubstituted acetylenes is discussed.

Synthesis, X-ray structure and reactions of phenylimidodecamethylvanadocene

The synthesis and X-ray structure of phenylimidodecamethylvanadocene are described. Its reactions with electrophiles, including isocyanides, which lead to loss of one pentamethylcyclopentadienyl ring (Cp★) are reported.

Functionalizable Schiff base complexes of lanthanum. Synthesis and crystal structures of [La2L4(thf)2(µ-Cl)2] and [La(L′)2(HL′)Cl][HL =N-(2,4,6-trimethylphenyl)salicylideneimine, HL′=N-(2-dimethylaminoethyl)-salicylideneimine, and thf = tetrahydrofuran]

The reaction of [{LaCl3(thf)}n](thf = tetrahydrofuran) under anhydrous conditions with the sodium salt of a bi- or tri-dentate Schiff base derived from salicylaldehyde and 2,4,6-trimethylaniline [HL =N-(2,4,6-trimethylphenyl)salicylideneimine] or N,N-dimethylethylenediamine [HL′=N-(2-dimethylaminoethyl)salicylideneimine] led to the isolation of the corresponding monochloro derivatives, [La2L4(thf)2(µ-Cl)2] and [La(L′)2(HL′)Cl]. Their structures have been elucidated by X-ray crystallography.

Titanium tetrachloride binding and making arenes from acetylenes: the synthesis and X-ray crystal structure of a titanium(IV)–hexamethylbenzene complex

Concentrated solutions of TiCl4 in CH2Cl2, o-C6H4Cl2, and n-hexane reacted with hexamethylbenzene producing [(η6-C6Me6)TiCl3]+[Ti2 Cl9]–, which can equally well be obtained from the same TiCl4 solutions and but-2-yne.

N,N'-ethylenebis(acetylacetoneiminato)titanium complexes: synthesis, crystal structures, and properties of titanium(III) and titanium(IV) derivatives

The reaction of TiCl4·2thf and TiCl3·3thf (thf = tetrahydrofuran) with the Na2acen [acen =N,N′-ethylenebis(acetylacetoneiminate) dianion] gave the corresponding titanium (IV), [Ti(acen)Cl2](1), and titanium(III), [Ti(acen)Cl(thf)](2), derivatives in good yield. Complex (2) has a d1 configuration and is easily oxidized to titanium (IV) derivatives. Reaction with oxygen afforded a µ-oxo complex [Cl(acen)TiOTi(acen)Cl], (3), having a linear Ti–O–Ti skeleton [Ti–O 1.813(1)A; ν(Ti–O) 750 cm–1]. The structures of complexes (1)–(3) have been determined by X-ray analysis: (1) space group P21/n(monoclinic), a= 27.510(9), b= 14.347(5), c= 7.839(3)A, β= 94.52(1)°, Z= 8, and R= 0.050 for 1 737 observed reflections; (2), space group P212121(orthorhombic), a=15.403(2), b= 14.883(2), c= 8.180(l)A, Z= 4, and R= 0.043 for 2 085 observed reflections; (3), space group P21/n(monoclinic), a= 10.599(2), b= 18.392(5), c= 7.551(2)A, β= 101.90(2°), Z= 2, and R= 0.031 for 1 961 observed reflections.

A mixed valence µ-oxo iron(III)–iron(II) complex: a polynuclear iron–sodium–oxo aggregate from the chemical reduction of a µ-oxo di-iron(III) complex

Reduction of {[Fe(acacen)]2O}{acacen =[MeC(O–)CHCMeNCH2]2}[Fe–O, 1.77(1)A Fe–O–Fe, 150.7(13)°] with sodium metal to give an iron–sodium–oxo aggregate {[Fe(acacen)]2ONa}2, containing the monoanionic µ-oxo iron(II)–iron(III) moiety, [Fe–O–Fe]– occurs with a significant lengthening of the Fe–O bonds, and contraction of the Fe–O–Fe angle [Fe–O, 1.999(6) and 2.069(6)A Fe–O–Fe, 134.9(4)°], as shown by a crystal structure determination.

Carbon–carbon bond formation and cleavage resulting from a long-range metal-promoted redox process in the reactions of nickel(II) complexes of N,N′-o-phenylenebis(salicylideneamine)

Alkali metals (Li or Na) promote the dimerization of N,N′-o-phenylenebis(salicylideneaminato)nickel(II)[Ni(salophen)], causing the reductive coupling of two imino functional groups between two units, which are joined by a rather long C–C bond [1.58(2)A] in the dimer [Ni(salophen)Na(tetrahydrofuran)3]2; the dimer is able to transfer two electrons to various substrates by a process cleaving the C–C bond and restoring the original [Ni(salophen)] structure.