Deprotonation reactions of zirconium and hafnium amide complexes H2N-M[N(SiMe3)2]3 and subsequent silyl migration from amide -N(SiMe3)2 to imide =NH ligands

Ammonolysis of previously reported Cl-M[N(SiMe3)2]3 (M = Zr, 1a; Hf, 1b) leads to the formation of peramides H2N-M[N(SiMe3)2]3 (M = Zr, 2a; Hf, 2b) which upon deprotonation by LiN(SiMe3)2 or Li(THF)3SiPh2But yields imides Li+(THF)n{HN(-)-M[N(SiMe3)2]3} (M = Zr, 3a; Hf, 3b). One -SiMe3 group in 3a-b undergoes silyl migration from a -N(SiMe3)2 ligand to the imide =NH ligand to give Li+(THF)2{Me3SiN(-)-M[NH(SiMe3)][N(SiMe3)2]2} (M = Zr, 4a; Hf, 4b) containing an imide =N(SiMe3) ligand. The kinetics of the 3a --> 4a conversion was investigated between 290 and 315 K and was first-order with respect to 3a. The activation parameters for this silyl migration are DeltaH++ = 13.3(1.3) kcal/mol and DeltaS++ = -34(3) eu in solutions of 3a (in toluene-d8 with 1.07 M THF) prepared in situ. THF in the mixed solvent promoted the 3a --> 4a reaction. The effect of THF on the rate constants of the conversion has been studied, and the kinetics of the reaction was 3.4(0.6)th order with respect to THF. Crystal and molecular structures of H2N-Zr[N(SiMe3)2]3 (2a) and 4a-b have been determined.     

A novel group of alkaline earth metal amides: syntheses and characterization of M[N(2,6-(i)Pr(2)C(6)H(3))(SiMe(3))](2)(THF)(2) (M = Mg,Ca, Sr,Ba) and the linear,two-coordinate Mg[N(2,6-(i)Pr(2)C(6)H(3))(SiMe(3))](2)

Novel alkaline earth metal aryl-substituted silylamides were prepared using alkane (Mg) and salt elimination reactions (Mg, Ca, Sr, and Ba). The salt elimination regime involved the treatment of the alkaline earth metal iodides with 2 equiv of the respective potassium amide KNDiip(SiMe(3)), (Diip = 2,6-i-Pr(2)C(6)H(3)). The organomagnesium source for the alkane elimination was ((n)()Bu/(s)()Bu)(2)Mg. All compounds were characterized using (1)H, (13)C NMR, and IR spectroscopy, in addition to X-ray crystallography (except Mg[NDiip(SiMe(3))](2)THF(2)). Crystal data with Mo Kalpha (lambda = 0.710 73 A) are as follows: Mg[NDiip(SiMe(3))](2), 1, a = 9.4687(6) A, b = 9.6818(6) A, c = 17.9296(1) A, alpha = 96.487(1) degrees, beta = 94.537(1) degrees, gamma = 89.222(1) degrees, V = 1608.8(2) A(3), Z = 2 (two independent molecules), triclinic, space group P(-)1, R1 (all data) = 0.0508; (n)()BuMg[NDiip(SiMe(3))]THF(2), 2, a = 9.5413(1) A, b = 16.493(2) A, c = 9.8218(1) A, beta = 108.149(2) degrees, V = 1468.7(4) A(3), Z = 2, monoclinic, space group P2(1), R1(all data) = 0.1232; Ca[NDiip(SiMe(3))](2)THF(2), 4, a = 9.7074(1) A, b = 20.9466(4) A, c = 21.6242(3) A, alpha = 73.573(1) degrees, beta = 78.632(1) degrees, gamma = 89.621(1) degrees, V = 4129.1(1) A(3), Z = 4 (two independent molecules), triclinic, space group P(-)1, R1 (all data) = 0.0902; Sr[NDiip(SiMe(3))](2)THF(2), 5, a = 20.5874(5) A, b = 9.8785(2) A, c = 20.8522(5) A, beta = 102.035(2) degrees, V = 4147.6(2) A(3), Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0756; Ba[NDiip(SiMe(3))](2)THF(2), 6, a = 20.5476(2) A, b = 10.0353(2) A, c = 20.9020(4) A, beta = 101.657(1) degrees, V = 4221.0(1) A(3), Z = 4 (two independent molecules), monoclinic, space group P2/n, R1 (all data) = 0.0573.     

Mechanism of single metal exchange in the reactions of [M4(SPh)10]2- (M = Zn or Fe) with CoX2 (X = Cl or NO3) or FeCl2

The kinetics of the reactions between [Zn4(SPh)10](2-) and an excess of MX2 (M = Co, X = NO3 or Cl; M = Fe, X = Cl), in which a Zn(II) is replaced by M(II), have been studied in MeCN at 25.0 degrees C. (1)H NMR spectroscopy shows that the ultimate product of the reactions is an equilibrium mixture of clusters of composition [Zn(n)M(4-n)(SPh)10](2-), and this is reflected in the multiphasic absorbance-time curves observed over protracted times (several minutes) using stopped-flow spectrophotometry to study the reactions. The kinetics of only the first phase have been determined, corresponding to the equilibrium formation of [Zn3M(SPh)10](2-). The effects of varying the concentrations of cluster, MX2, and ZnCl2 on the kinetics have been investigated. The rate law is consistent with the equilibrium nature of the metal exchange process and indicates a mechanism for the formation of [Zn3M(SPh)10](2-) involving two coupled equilibria. In the initial step binding of MX2 to a bridging thiolate in [Zn4(SPh)10](2-) results in breaking of a Zn-bridging thiolate bond. In the second step replacement of the cluster Zn involves transfer of the bridging thiolates from the Zn to M, with breaking of a Zn-bridged thiolate bond being rate-limiting. The kinetics for the reaction of ZnCl2 with [Zn3M(SPh)10](2-) (M = Fe or Co)} depends on the identity of M. This behavior indicates attack of ZnCl2 at a M-mu-SPh-Zn bridged thiolate. Similar studies on the analogous reactions between [Fe4(SPh)10](2-) and an excess of CoX2 (X = NO3 or Cl) in MeCN exhibit simpler kinetics but these are also consistent with the same mechanism.     

The particular sensitivity of silyl ethers of D-glucal toward two Vilsmeier-Haack reagents POCl3.DMF and (CF3SO2)2O.DMF. Their unique and selective conversion to the corresponding C(6)-O-formates.

The two electrophilic Vilsmeier-Haack reagents POCl3.DMF 2 or (CF3SO2)2O.DMF 3 mediate the one-step and selective conversion of O-triethylsilyl (O-TES), O-tert-butyldimethylsilyl (O-TBDMS), O-tert-butyldiphenylsilyl (O-TBDPS), and O-triisopropylsilyl (O-TIPS) ethers of D-glucal to the corresponding C(6)-O-formates.     

Photochemical reactions of metal carbonyls [M(CO)6 (M = Cr,Mo and W), Re(CO)5Br,Mn(CO)3Cp] with 2-hydroxyacetophenone methanesulfonylhydrazone (apmsh)

Five new complexes, [M(CO)₅(apmsh)] [M = Cr; (1), Mo; (2), W; (3)], [Re(CO)₄Br(apmsh)] (4) and [Mn(CO)₃(apmsh)] (5) have been synthesized by the photochemical reaction of metal carbonyls [M(CO)₆] (M = Cr, Mo and W), [Re(CO)₅Br], and [Mn(CO)₃Cp] with 2-hydroxyacetophenone methanesulfonylhydrazone (apmsh). The complexes have been characterized by elemental analysis, mass spectrometry, f.t.-i.r. and ¹H spectroscopy. Spectroscopic studies show that apmsh behaves as a monodentate ligand coordinating via the imine N donor atom in [M(CO)₅(apmsh)] (1–4) and as a tridentate ligand in (5).     

New triosmium metal clusters derived from the reactions between [Os3(CO)10(NCMe)2] and amides

Triosmium clusters of the type [Os₃(CO)₁₀(μ-H)(NHCOR)] (1; R = H, Me, Ph, Et or Pr) are formed in high yields form the reaction of [Os₃(CO)₁₀(NCMe)₂] (2) with amides. The nature of the products formed from thermolysis of 1 depend on the group, R.     

The reactions of [MI2(CO)3(NCMe)2] (M=Mo or W) with one equivalent of L(L-phosphorus,arsenic and antimony donor ligands) to afford [MI2(CO)3(NCMe)L] and [M(μ-I)I(CO)3L]2

Summary The complexes [MI₂(CO)₃(NCMe)₂] (M=Mo or W) react with one molar equivalent of L in CH₂Cl₂ at room temperature initially to afford the mononuclear sevencoordinate complexes [MI₂(CO)₃(NCMe)L] which have been isolated for L-PPh₃, AsPh₃, SbPh₃, PPh₂Cy or P(OPh₃)₃. Many of these complexes dimerise to give the iodide bridged compounds [{M(–I)I(CO)₃L}₂]via displacement of acetonitrile. When L=PPhCy₂, PCy₃, PEt₃ or P(OMe)₃ only the dimeric complexes have been isolated. The ease of dimerisation of the mononuclear complexes [MI₂(CO)₃(NCMe)L] is discussed in terms of the electronic and steric effects of the ligands, L. Low temperature¹³C n.m.r. spectroscopy of the mononuclear [Wl₂(CO)₃(NCMe)(EPh₃)](E=P or As) complexes are interpreted as suggesting the likely stereochemistry of these seven-coordinate complexes.     

Quasi-isomeric gallium amides and imides GaNR2 and RGaNR (R = organic group): reactions of the digallene, Ar'GaGaAr' (Ar' = C6H3-2,6-(C6H3-2,6-Pri2)2) with unsaturated nitrogen compounds

Reactions of the "digallene" Ar'GaGaAr'(1) (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-Pr(i)(2))(2)), which dissociates to green :GaAr' monomers in solution, with unsaturated N-N-bonded molecules are described. Treatment of solutions of :GaAr' with the bulky azide N(3)Ar(#) (Ar(#) = C(6)H(3)-2,6-(C(6)H(2)-2,6-Me(2)-4-Bu(t))(2)), afforded the red imide Ar'GaNAr(#) (2). Addition of the azobenzenes, ArylNNAryl (Aryl = C(6)H(4)-4-Me (p-tolyl), mesityl, and C(6)H(3)-2,6-Et(2)) yielded the 1,2-Ga(2)N(2) ring compound Ar'GaN(p-tolyl)N(p-tolyl)GaA' (3) or the products MesN=NC(6)H(2)-2,4-Me(2)-6-Ga(Me)Ar' (4) and 2,6-Et(2)C(6)H(3)N=NC(6)H(3)-2-Et-6-Ga(Et)Ar' (5). Reaction of GaAr' with N(2)CPh(2) yielded the 1,3-Ga(2)N(2) ring compound Ar'Ga(mu:eta(1)-N(2)CPh(2))(2)GaAr' (6), which is quasi-isomeric to 3. Calculations on simple model isomers showed that the Ga(I) amide GaNR(2) (R = Me) is much more stable than the isomeric Ga(III) imide RGaNR. This led to the synthesis of the first stable monomeric Ga(I) amide, GaN(SiMe(3))Ar' ' (8) (Ar' ' = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2) from the reaction of LiN(SiMe(3))Ar' ' (7) and "GaI". Compound 8 is also the first one-coordinate gallium species to be characterized in the solid state. The reaction of 8 with N(3)Ar' ' afforded the amido-imide derivative Ar' 'NGaN(SiMe(3))Ar' ' (9), a gallium nitrogen analogue of an allyl anion. All compounds were spectroscopically and structurally characterized. In addition, DFT calculations were performed on model compounds of the amide, imide, and cyclic 1,2- and 1,3-species to better understand their bonding. The pairs of compounds 2 and 8 as well as 3 and 6 are rare examples of quasi-isomeric heavier main group element compounds.