Alexander N. Kornev

FERROUS TRIS( TRIMETHYLSILYL) SILANOLATES : SYNTHESIS, STRUCTURE, REACTIVITY AND THERMAL DECOMPOSITION

Abstract Reaction of FeBr2 with 3 equiv. of sodium tris(trimethylsilyl)silanolate (1) in DME affords the ate-complex {(Me3Si)3SiOFe[μ-OSi(SiMe3)]2Na(DME)} (2). X-ray studies have shown the Fe atom in 2 is bonded to three O atoms of OSi(SiMe3)3 groups, two O atoms are connecting as a μ-bridge the Fe[OSi(SiMe3)3]3] unit with the Na(DME) group. The FeO3 core is slightly non-planar: the deviation of the Fe atom from the O3 plane is 0.08A. The four-member Fe(μ-O)2Na cycle is also non-planar: the dihedral angle between the Fe(μ-O)2 and the (μ-O)2Na planes is 31.0°. The bridging and terminal FeO distances are 1.840(2) and 1.894(2), 1.910(2) A, respectively. The average SiSi and SiC distances are 2.358(8) A and 1.873(8) A. Interaction of FeBr2 with two equiv. of 1 in THF followed by treatment with pyridine yields the adduct, [(Me3Si)3SiO]2Fe(Py)2 (3). The Mossbauer spectrum of complex 2 at 295 K consists of a single doublet with isomer shift 0.60(1) mm/s and quadrupole splitting 0.90(3) mm/s. The corresponding parameters of 3 are as follows: isomer shift, 1.08(1) mm/s, and quadrupole splitting, 2.12(2) mm/s. Molecular oxygen is easily incorporated into the SiSi bonds of compounds 2 and 3 by activation at the iron (II) center. Reaction of 2 with 1 equiv. of tetracyanoethylene leads to iron (III) silanolate, [(Me3Si)3SiO]3Fe (4) and the anion-radical salt, Na +TCNE−. Slow thermolysis of 2 and 3 yields (Me3Si)2SiOSiMe3 and (Me3Si)4Si as well as polyferrsiloxane with MW ∼ 3500. Fast thermolysis results in formation of α-Fe and a complicated mixture of oligosiloxanes.

Migratory Insertion of the R2P Group into a Nitrogen-Nitrogen Bond : A Novel Type of Rearrangement in Phosphorus-Nitrogen Ligand Chemistry. 3. The Rearrangement of Triphosphinohydrazide Ligand -N(PPh2)-N(PPh2)2 to Triphosphazenide Anion {[(Ph2P-N]2PPh2}-in the Coordination Sphere of Divalent Cobalt and Nickel

Hydrazine dihydrochloride reacts with 3 equiv of Ph2PCl in tetrahydrofuran in the presence of triethylamine to give tris(diphenylphosphino)hydrazine (1) in 70% yield. Each nitrogen atom in 1 has a trigonal-planar environment according to X-ray analysis. Thermolysis of 1 at 130 degrees C results in the formation of two products: bis(diphenylphosphino)amine and octaphenylcyclotetraphosphazene. The interaction of free ligand 1 with NiBr2 affords a simple adduct [(Ph2P)2N-NH-PPh2]NiBr2, while its anionic (hydrazide) form undergoes rearrangement in a coordination sphere of divalent cobalt and nickel involving migratory insertion of the Ph2P group into a nitrogen-nitrogen bond. The reaction of 1 with cobalt bis(trimethylsilyl)amide, [(Me3Si)2N]2Co, yields the complex of phosphazenide-type (Me3Si)2N-Co[(Ph2PN)2PPh2] (2) in 86% yield. A similar reaction of 1 with nikelocene proceeds with substitution of one Cp ring to form durable 18-electron complex CpNi[(Ph2PN)2PPh2] (3).

Nickel(II) and nickel(0) derivatives of bis(diphenylphosphino)amine: [N(PPh2)2]2Ni, (Ph3P)2Ni[(Ph2P)2NH]. Synthesis, characterization, and some properties

Disproportionation of nickel(I) bis(triphenylphosphino)bis(trimethylsilyl)amide, (Ph 3 P) 2 NiN(SiMe 3 ) 2 , in the presence of bis(diphenylphosphino)amine, (Ph 2 P) 2 NH, yields Ni(II) and Ni(0) phosphinoamide complexes: [N(Ph 2 P) 2 ] 2 Ni ( 1 ), (Ph 3 P) 2 Ni[(Ph 2 P) 2 NH] ( 2 ). Ether solution, containing 2 and Ph 3 P (1:2) reacts with dioxygen (one equivalent) to form triphenylphosphinoxide adduct (Ph 3 P) 2 Ni[(Ph 2 P) 2 NH⋯OPPh 3 ] ( 3 ) in high yield. The crystal structures of compounds 1 and 3 have been determined by X-ray diffraction method.

TRIS(TRIMETHYLSILYL)SILOXIDES OF GADOLINIUM AND LANTHANUM : SYNTHESIS, STRUCTURE AND SOME PROPERTIES

A series of gadolinium and lanthanum siloxide complexes of empirical formula [(Me 3 Si) 3 SiO] 3 Ln(L n ) {Ln=Gd, L n =(THF) 2 ( 1 ), (MeCN) 2 ( 2 ), [N(C 2 H 4 ) 3 N] 2 ( 3 ), (4,4′-dipyridyl) 2 ( 4 ), (4,4′-dipyridyl) 1 ( 5 ); Ln=La, L n =(THF) 4 ( 6 )} have been prepared by the reaction of [(Me 3 Si) 2 N] 3 Ln (Ln=Gd, La) with (Me 3 Si) 3 SiOH or LnCl 3 (Ln=Gd) with (Me 3 Si) 3 SiONa in various solvents. Both [(Me 3 Si) 3 SiO] 3 Gd(THF) 2 ( 1 ) and [(Me 3 Si) 3 SiO] 3 Gd[N(C 2 H 4 ) 3 N] 2 ( 3 ) have been characterized by X-ray crystallography. The Gd in both 1 and 3 has a trigonal-bipyramidal environment with three O atoms in equatorial and two B atoms (B=O in 1 and N in 3 ) in axial positions. The symmetries of molecules of 1 and 3 are C 3 i and C 3 h , respectively. The GdOSi angles and the GdO distances are 161.2(3)°, 2.142(7) A in 1 and 165.4(2)°, 2.161(4) A in 3 . The GdO(THF) distances in 1 are 2.448(9), 2.314(18) and the GdN distance in 3 is 2.520(6) A. Gadolinium complex ( 1 ) and the lanthanum complex ( 6 ) readily absorb one and three moles of CO 2 , respectively to form the corresponding carbonates. Compounds 1 and 6 sublime at 205°C in vacuo to form homoleptic siloxides. A subsequent rise in temperature results in their decomposition to give polylanthanosiloxanes, and (Me 3 Si) 3 SiOH as the only volatile product up to 300°C.

New type of coordination of phosphorus to carbene analogs. p(π)-Complex of 3a,6a-diaza-1,4-diphosphapentalene with germanium dichloride

Abstract3a,6a-Diaza-1,4-diphosphapentalene (1), as a neutral ligand, displays a new type of complexation, such that the lone pair at the phosphorus atom is not involved in the coordination; instead, the 10π-electron system provides two electrons for the coordination bond formation between the phosphorus atom and the metal. The p(π)-type complex–a molecular adduct of 1 with germanium dichloride — was synthesized and completely characterized. This complex is a coordination polymer with short intermolecular Ge—Ge, Ge—P, P—P, P—Cl, and Ge—C contacts.

Chemistry of the phosphorus-nitrogen ligands. Multiple isomeric transformations of the diphosphinohydrazine bearing 8-quinolyl substituent: P→C, P→N, and P→P migrations caused by different factors.

The reaction of 8-quinolylhydrazine with 2 equiv of Ph(2)PCl in the presence of Et(3)N gives 8-[(Ph(2)P)(2)NNH]-Quin (1) (Quin = quinolyl) in 84% yield. The heating of 1 at 130 °C for 1 h in toluene results in migration of the [Ph(2)PNPPh(2)] group to a carbon atom of the quinolyl fragment to form an isomer, 7-(Ph(2)P-N═PPh(2))-8-NH(2)-Quin (2). The same migration is caused by the addition of LiN(SiMe(3))(2) to 1. On the contrary, lithiation of 1 with n-BuLi followed by the addition of ZnI(2) (1:1) affords the aminoquinolyl-phosphazenide dinuclear complex [ZnI(8-Quin-NPPh(2)═N-PPh(2))-κ(3)N,N,P](2) (4), which is a result of P→N migration. Compound 1 itself reacts with ZnI(2) in THF to form 4 and protonated molecule 1·HI, which rearranges to the more stable iminobiphosphine salt (Ph(2)P-PPh(2)═N-NH-Quin-8)·HI. Zinc iodide reacts with 2 equiv of the lithium salt of 1 without rearrangement, to form homoleptic aminoquinolyl zinc complex Zn[{(Ph(2)P)(2)NN-Quin-8}-κ(2)N,N](2) (6). Solutions of 4 and 2 in dichloromethane show luminescence at 510 and 460 nm (quantum yields are 45% and 7%, respectively). DFT calculations were provided for possible isomers and their complexes.

Synthesis, structure, and reactivity of siloxides and germyloxides of iron(ii) and cobalt(ii)

Iron and cobalt siloxides and germyloxides [(Me3Si)3SiO]2M (M = Fe (1), Co (2)), (Me5Si2O)2Fe (3), (Pri3SiO)2M (M = Fe (4), Co (5)), (Pri3GeO)2Fe (6), (Ph3SiO)2Fe (7), (Me3SiO)2Fe (8), (Pri3GeO)2Fe(bpy) (9), and [(Me3Si)2NFe(μ-OSi2Me5)2]2Fe·C6H6 (10) were synthesized by the reactions of metal silylamides [(Me3Si)2N]2M (M = Fe, Co) with the corresponding silanols or triisopropylgermanol. The reaction of pentamethyldisilanol with iron(ii) silylamide affords either polymeric complex 3 or coordination oligomer 10, depending on the ratio of the reactants. The structures of complexes 9 and 10 were established by X-ray diffraction analysis. The interaction of the prepared compounds with carbon oxides was studied. Low-coordination cobalt siloxide is the only among all prepared compounds that absorbs CO (2 mol) at room temperature and under 1 atm to form an unstable cluster. Compounds 1, 2, and 4—8 react with CO2 to form carbonate complexes, and their reactivity decreases with a decrease in the electron-donating ability of the substituents at the central atom: (Me3Si)3SiO > Pri3GeO ≈ Pri3SiO > Me3SiO ≫ Ph3SiO.

Cobalt(II) and iron(II) tris(trimethylsilyl)siloxides: synthesis, structure and reactivity

Abstract A series of cobalt(II) and iron(II) siloxide complexes, [(Me3Si)3SiO]2M(Ln) {M=Co, Ln=none (1), (THF) (3), (THF)2 (4), (DME) (5), (MeCN)2 (6), (PhCN)2 (7), (2,2′-dipyridyl) (8), 4,4′-dipyridyl (9), (Ph3P)2 (10); M=Fe, Ln=none (2), (2,2′-dipyridyl) (11) were prepared by the reaction of metal silylamides [(Me3Si)2N]2M (M=Co, Fe) with tris(trimethylsilyl)silanol. The crystal structures of compounds 1 and 11 have been determined by the X-ray diffraction method. Complex 1 has a dimeric structure with two [(Me3Si)3SiO]2Co units bonded via the two μ2-O atoms. The central [Co(μ2-O)]2 cycle has a ‘butterfly shape’ being bent along the bridging oxygen atoms. The dihedral angle between the Co(1)O(4)Co(2) and Co(1)O(3)Co(2) planes is 143.1°. The μ2-bridging and terminal CoO distances are 1.945(7)–1.963(7) and 1.781(8), 1.793(7) A, respectively. The Co⋯Co distance in 1 is relatively short, 2.735(2) A. However, the high value of magnetic moment (6.0 μB) of compound 1 indicates the absence of a direct interaction between the Co atoms in 1. The molecule of 11 is monomeric. The Fe atom is bonded to 2,2′-dipyridyl and two terminal OSi(SiMe3)3 groups and has a distorted tetrahedral environment. The FeN(1), FeN(2) and FeO(1), FeO(2) distances in 11 are 2.148(1), 2.164(1) and 1.863(1), 1.900(1) A, respectively. Addition of one equivalent of PhCCH to 7 results in the substitution of one tris(trimethylsilyl)siloxy-group with the formation of the diamagnetic dimer {(PhCN)(PhC2)CoOSi(SiMe3)3}2. Subsequent addition of PhC2H causes its oligomerisation. Complexes 1, 3 and 10 absorb carbon monoxide at ambient temperature and pressure while the others remain unreactive. Electronic spectra show fluxional behavior of complexes 1, 3 and 4 in solution.

Lithium and sodiumtris(trimethylsilyl)silanolates. Synthesis and reactivity

Lithium and sodium tris(trimethylsilyl)silanolates were obtained by the reaction of tris(trimethylsilyl)silanol with BunLi or PriONa in hexane. The degree of association of silanolates in benzene solution was found to be 2 and 4 for the sodium and lithium derivatives, respectively. (Me3Si)3SiONa is noticeably more active than the lithium derivative in the reaction with Me3SiCl. Tris(trimethylsilyl)silanol reacts with trimethylchlorosilane to give (Me3Si)3SiCl. The hydrolysis of (Me3Si)3SiONa (Li) in benzene and hexane yields the corresponding silanol, whereas in HMPA the splitting of Si-Si bonds and hydrogen evolution were observed.

Chemical properties of 3a,6a-diaza-1,4-diphosphapentalene. Addition of polyhalohydrocarbons

Abstract3a,6a-Diaza-1,4-diphosphapentalene (DDP, 1), in contrast to common azaphospholes, readily reacts with polyhalohydrocarbons with the formation of 1,1- or 1,4-addition products at the phosphorus atoms. Dibromomethane gives the substitution product of two bromine atoms [CH2(DDP)2]Br2 (2) and diphosphine (DDP-DDP)Br2 (3) containing a bridging bromine atom. In the course of the reaction of DDP with CF2Br2, two products of sequential substitution of the bromine atoms were isolated, which are 1,4-Br2(DDP) (6) and [CF2(DDP)2]Br2 (7). Tris(pentafluorophenyl)phosphine reacts with DDP at the C—F bond with the formation of 1,1-addition product 8. Compounds 2, 3, 7, and 8 contain hypervalent (tervalent 4-coordinated) phosphorus atoms. X-ray diffraction data indicate that the mutual arrangement of the DDP fragments in compounds 2, 3, and 7 is determined by the non-covalent interaction of one of the bromine atoms simultaneously with two phosphorus atoms of different DDP fragments in such a way that the lines of the N—P bonds converge at this bromine atom.