Donald C. Bradley

Synthesis and chemistry of the bis(trimethylsilyl)amido bis-tetrahydrofuranates of the group 2 metals magnesium, calcium, strontium and barium. X-ray crystal structures of Mg[N(SiMe3)2]2·2THF and related Mn[N(SiMe3)2]2·2THF

Abstract Transamination reactions utilizing the compound mercuric bis(trimethylsilyl)amide, Hg{N(SiMe3)2}2, in tetrahydrofuran (THF), and the metals Na, Mg, Ca, Sr, Ba and Al have been investigated. Thus the THF solvated compounds Na[N(SiMe3)2]·THF and M[N(SiMe3)2]2·2THF, M = Mg, Ca, Sr and Ba (1–4), have been prepared. The X-ray crystal structures of 1 and the related manganese compound Mn[N(SiMe3)2]2·2THF (5) are reported. Interaction of the silylamides, 2–4, with a range of crown ethers apparently proceeded with elimination of silylamine, (Me3Si)2NH, and novel ring opening of the crown ethers, generating species containing a donor alkoxide ligand with a vinyl ether function, presumably, ue5f8O(CH2CH2O)nCHue5fbCH2 (n = 3−5). The silylamides 2–4 were also cleanly converted to the corresponding alkoxides (from 1H NMR data) in reactions with stoichiometric quantities of 3-ethyl-3-pentanol.

Pentanuclear oxoalkoxide clusters of scandium, yttrium, indium and ytterbium, X-ray crystal structures of [M5(μ5-O)(μ3-OPri)4(μ2-OPri)4(OPri)5] (M = In, Yb)

Abstract Attempts to prepare the metal tri-isopropoxides M(OPri)3 (M = Sc, Y, In, Yb) by various methods always produced the pentanuclear oxoalkoxide clusters [M5(μ5-O)(μ3-OPri)4(μ2-OPri)4(OPri)5] as the stable products. X-ray single crystal diffraction showed (M = In, Yb) the presence of the μ5-oxygen atom bonded in a square pyramidal configuration to five metal atoms which had terminal isopropoxo groups trans to the oxo atom. The μ3- and μ2-isopropoxo groups contribute to the distorted octahedral coordination of each metal atom. The scandium, yttrium and ytterbium clusters could be sublimed in vacuo and gave mass spectra containing pentanuclear cluster ions.The 1H NMR spectra for each compound was consistent with the X-ray crystal structure and variable-temperature studies showed fluxionality in the indium complex.

Volatile tris-tertiary-alkoxides of yttrium and lanthanum. The x-ray crystal structure of [La3(OBut)9(ButOH)2]

Abstract Tertiary alkoxides of yttrium and lanthanum have been prepared by addition of excess tertiary alcohol to the metal tris-(bis-trimethylsilylamides), M{N(SiMe3)2}3 (M = Y, La), and characterized by elemental analyses, NMR, IR and mass spectroscopy. With t-butanol and t-amyl alcohol the alcoholates [Y3(OBut)9(ButOH)2] (1), [Y3(OAmt)9 (AmtOH)2] (2) and [La3(OBut)9(ButOH)2] (3) were isolated. With higher tertiary alcohols the tris-t-alkoxides [M(OR)3] were obtained [M = Y, R = CMe2Pri (4), CMeEtPri (5), CEt3 (6); M = La, R = CMe2Pri (7), CMeEtPri (8)] as dimers. The coordinated ButOH in 1 could be replaced by THF or pyridine but not by trimethylamine. The X-ray crystal structure of 3 showed that the La3 triangle is capped by two μ3-OBut groups with three μ2-OBut bridges as in [La3(μ3-OBut)2(μ-OBut)3(OBut)4(ButOH)2]. The variable temperature NMR data suggest that compounds 1 and 2 have the same structure in solution as compound 3.

Volatile metallo-organic precursors for depositing inorganic electronic materials

these materials are highly refractory and their conventional synthesis entails high temperatures, a highly undesirable feature. In particular the need to deposit thin films of multilayer devices posed a major problem for materials scientists. Whilst molecular beam epitaxy (MBE) is probably the ultimate technique for the controlled epitaxial deposition of very thin multilayers (10-100 A) under UHV conditions for research purposes, there is little doubt that metallo-organic chemical vapour deposition (MOCVD) has the advantage for rapid deposition covering large areas of substrate. The essence of the MOCVD process is the therrnolysis of volatile molecular precursors containing the requisite elements to deposit the desired compound (or element) on a suitable substrate at a convenient temperature. Thus a suitable precursor needs to be sufficiently stable to generate a substantial vapour pressure (e.g. 10 Torr) at a moderate temperature (e.g. 20-SOOC) and yet break down cleanly at a higher temperature. Photolytic decomposrtion is an alternative method of breakdown of the metallo-organic precursor. An added requirement in many cases is extremely high purity and from the industrial point of view non-toxic non-hazardous compounds are preferred. In recent years inorganic chemists have responded to the challenge of synthesizing suitable metallo-organic molecular precursors both by improving on the synthesis and purification of some

The preparation and characterization of volatile derivatives of trivalent metals using fluorinated alkoxide ligands. X-ray structures of [Sc{OCH(CF3)2}3(NH3)2]2, [Pr{OCMe(CF3)2}3(NH3)2]2, [Y{OCMe(CF3)2}3(thf)3] and [Pr{OCMe2(CF3}3]3

Abstract From the reaction of fluorinated alcohols ROH [Rue5fb (CF 3 ) 2 CH, (CF 3 )Me 2 C or (CF 3 ) 2 MeC] with metal tri-(bis-trimethylsilylamides) [M{N(SiMe 3 ) 2 } 3 ] (M ue5fb Sc, Y, La or Pr) in benzene, thf or diethyl ether, volatile compounds of formulae [M(OR) 3 (NH 3 ) x ] (X = 0-3), M(OR) 3 (thf) 3 and M(OR) 3 (Et 2 O) x ( x = 0.33 or 0.5) have been isolated. X-ray crystal structures were determined for [SC{ 2 OCH(CF 3 ) 2 } 6 (NH 3 ) 4 ], [Pr 2 {OCMe (CF 3 ) 2 } 6 (NH 3 ) 4 ], [Y{OCMe(CF 3 ) 2 } 3 (thf) 3 ], [La{OCMe(CF 3 ) 2 } 3 (thf) 3 ] and [Pr 3 {OCMe 2 (CF 3 ) 2 } 9 ].

Dimethylindium dialkylamides and organylphosphides, X-ray crystal structure of (Me2InNR2)2 (R = Et, Pri, SiMe3) and (Me2InPBut2)2

The compounds (Me2InNR2)2 (R = Et, Pri, SiMe3 and (Me2InPR2 (R = But, have been prepared. the X-ray crystal structures of all but the diphenylphosphide have been determined, and show them to be pnictido-bridged dimers; the mass spectra of all the compounds indicate that they are dimeric in the vapour phase. The stability of the dialkylamide dimers in the vapour as determined from the mass spectra appears to be in the order NMe2 > NEt2 > NPr2i > N(SiMe3)2, in line with steric effects; the crystal structures showed a slight lengthening of the Iue5f8N bond in the same order, but the most marked structural variation was shown to be the Cue5f8C angle which had values of 131, 126, 119 and 109°, respectively. The corresponding value for (Me2InPBu2t)2 was 109°.

Adducts of trimethylindium with amine and phosphine ligands; X-ray crystal structure of Me3InNHCMe2(CH2)3CMe2, Me3InN(CH2CH2)3N and Me3InNHMe(CH2)2NHMeInMe3

Abstract Treatment of trimethylindium diethyletherate separately with a number of amines and a phosphine has given the products Me3InL where L ue5fb NH(C6H11)2 (1), NHCHMe(CH 2 ) 3 C HMe (2), NHCMe 2 (CH 2 ) 3 C Me2 (3), N(CH2CH2)3CH (4), N(CH2CH2)3N (5), (CH2NEt)3 (6) and P(NMe2)3 (7). The complexes Me3In-NHMe(CH2)2NHMeInMe3 (8) and Me2InCl[MeNH C(CH) 4 N ] (9) have also been made by direct reaction of Lewis acid etherate and Lewis base. The X-ray crystal structure of 3 shows a longer Inue5f8N bond (2.50 A) than that found in the crystal structure of 8 (2.38 A); both possess distorted tetrahedral metal environments. The X-ray crystal structure of 5 shows a linear polymer of alternating Me3In and N(CH2CH2)3N units; the Me3In unit is planar and the indium is almost perfectly trigonal bipyramidal and the Inue5f8N bonds are very long (2.62 A) compared with 3 and 8. Variable temperature 1H NMR studies of 6 show the adduct bond is very labile: rapid exchange between adduct components is occurring even at −70°C.

The synthesis and characterization of volatile complexes of fluorinated alkoxides of yttrium. X-ray structures of [Y{OCMe(CF3)2}3(thf)3] and [Y{OCMe(CF3)2}3(diglyme)]

Abstract From the reactions of (CF3)2CHOH (hfip.H), (CF3)Me2COH (tftb.H) and (CF3)2MeCOH (hftb.H) with Y{N(SiMe3)2}3 in benzene, thf or diethyl ether as solvents the following compounds have been isolated and characterized by elemental analysis, IR, NMR and mass spectroscopy : [Y{OCMe2(CF3)}3]n (1), [Y{OCMe2(CF3)}3(thf)2.5] (2), [Y{OCMe(CF3)2}3]n, (3), [Y{OCMe(CF3)2}3(NH3)0.5] (4), [Y{OCMe(CF3)2}3(NH3)3] (5), [Y{OCMe(CF3)2}3(thf)3] (6), [Y{OCMe(CF3)2}3(Et2O)0.33] (7), [Y{OCMe(CF3)2}3 (diglyme)] (8), [Y{OCMe(CF3)2}3(ButOH)3] (9), [Y{OCH(CF3)2}3(NH3)0.5] (10) and [Y{OCH(CF3)2}3(thf)3] (11). Sublimation in vacuo is usually accompanied by loss of some of the neutral ligand, but 8 sublimes intact. Single-crystal X-ray structures of 6 and 8 showed that these mononuclear octahedral complexes have the facial configuration. 89Y NMR chemical shifts were obtained for 2, δ 93.66; 6, 66.44; 8, 78.63; and 11, 82.78.

Volatile fluorinated tertiary alkoxides of some lanthanides, tris-hexafluoro-tertiary butoxides of lanthanum, praseodymium and europium

Abstract From reactions involving M{N(SiMe3)2}3 (M = La, Pr, Eu) and hexafluoro-tert-butanol [(CF3)2MeCOH, hftb.H) the following compounds have been isolated: [La(hftb)3]n (1), [La(hftb)3(NH3)]n (2), [La2(hftb)6(NH3)4] (3), [La(hftb)3(Et2O)0.33]n (4), [Pr(hftb)3]n (5), [Pr2(hftb)6(NH3)4], (6), [Eu(hftb)3]n (7) and [Eu2(hftb)6(NH3)2] (8). These compounds were characterized by elemental analyses and spectroscopic studies. The structure of [Pr2(hftb)6(NH3)4] (6) was determined by single-crystal X-ray diffraction. The molecule is a centrosymmetric dimer with the praseodymium atoms in a distorted octahedral configuration. The ammonia ligands are cis to each other, one is trans to a terminal hftb group and the other is trans to a bridging hftb group.

Synthesis, photochemistry and X-ray crystal structures of the methyltris[bis(trimethylsilyl)amido] compounds MeTi[N(SiMe3)2]3 and MeZr[N(SiMe3)2]3

Abstract The synthesis and characterization of the compound methyltris[bis(trimethylsilyl)amido]titanium, MeTi[N(SiMe3)2]3 (1), is reported. In the presence of UV radiation or sunlight, 1 decomposed rapidly to the titanium(III) species Ti[N(SiMe3)2]3 (2). The X-ray crystal structures of the compounds MeM[N(SiMe3)2]3, M = Ti and Zr (3), are reported. Compound 3 was stable in sunlight, but the cyclometallated product [(Me3Si)2N]2 ZrN(SiMe 3 )SiMe 2 C H2 (4) was apparently formed (from 1H and 13C NMR data) when solutions of 3 were exposed to a source of UV radiation.