Mark A. Petrie

Synthesis and characterization of the monomeric phosphinogallanes But2GaPR′R″(R′, R″= bulky aryl or silyl groups) and related compounds

The use of bulky substituent groups has allowed the isolation and spectroscopic and structural characterization of several monomeric phosphinogallanes wherein gallium and phosphorus are three-co-ordinate. These new compounds have the formula But2GaP(R)(SiPh3)(R = C6H2But3-2,4,6 1, C6H2Pri3-2,4,6 2, C6H2Me3-2,4,6 3 or SiMe34). Variable-temperature 1H NMR studies indicate that there is a rotational barrier of ca. 12.7 kcal mol–1 around the Ga–P bond in 1 which has been attributed to weak Ga–P π bonding. The synthesis and structures of the related aluminium–phosphorus species But2Al(Et2O)-P(C6H2Pri3-2,4,6)(SiPh3)5 and the gallium–arsenic species But2GaAs[CH(SiMe3)2](SiPh3)6 are also reported. In addition, variable-temperature 1H NMR studies of the precursor asymmetric phosphines (Ph3Si)P(R)H (R = C6H2But3-2,4,6 7, C6H2Pri3-2,4,6 8 or C6H2Me3-2,4,6 9) as well as the X-ray structures of (Ph3Si)P(C6H2But3-2,4,6)H 7 and (Ph3Si)P(SiMe3)210 are discussed. Crystal data with Mo-Kα radiation (λ= 0.710 69 A) at 130 K: 2, monoclinic, space group P21/c, a= 18.499(5), b= 10.028(4), c= 20.746(6)A, β= 90.45(1)°, Z= 4, R= 0.043; 5, triclinic, space group P, a= 9.488(3), b= 11.416(5), c= 20.383(6)A, α= 92.07(3), β= 96.80(2), γ= 103.17(3)°, Z= 2, R= 0.079; 6, triclinic, space group P, a= 12.219(3), b= 14.174(3), c= 21.831(5)A, α= 92.95(2), β= 99.73(2), γ= 99.47(2)°, Z= 4, R= 0.053; 7, monoclinic, space group P21/c, a= 17.710(6), b= 16.635(5), c= 10.838(4)A, β= 97.43(3)°, Z= 4, R= 0.044; 10, orthorhombic, space group Pbca, a= 16.092(5), b= 16.841(5), c= 18.778(5)A, Z= 8 and R= 0.050.

Multiple bonding, π-bonding contributions and aromatic character in isoelectronic boron-phosphorus, boron-arsenic, aluminum-nitrogen and zinc-sulfur compounds

Variable temperature 1H NMR studies of various boron-phosphorus (B-P) and boron-arsenic (B-As) compounds have afforded data on the strength of B-P and B-As x- bonds. For (RPBMes2)- and (RAsBMeszl- ions the energy of the x-bond can be as high as 24 kcal mol-1 and 21 kcal mol-1, respectively. Inversion barriers near 10 kcal mol-1 were determined for the pnictide center in simple monomeric phosphino or arsino boranes. The effects of substituent size and type on the B-P or B-As multiple bonds were also investigated. Compounds with extended linear arrays of up to five boron or phosphorus atoms were also synthesized and characterized both structurally and spectroscopically. In addition, the aromaticity of six-membered rings comprised of (B- Ph arrays was investigated. Structural spectroscopic and theoretical data support the view that the unsaturated B3P3 ring system has greater aromatic character than borazine. The range of quasi aromatic rings was also extended to include the isoelectronic and isolobal rings comprised of the arrays (Al-N)3 (alumazene) (:GeN)3, and (ZnS)3. The bonding and the relative aromatic character of these rings is also discussed.

Preparation and vibrational spectra of N(CH3)4+IF2− and electronic structure calculations of IF2−, BrF2−, ClF2−, XeF2 and KrF2

Abstract The new IF 2 salt, N(CH 3 ) 4 IF 2 , was prepared in quantitative yield and high purity from commercially available N(CH 3 ) 4 I and XeF 2 at −31°C in CH 3 CN solution. Its vibrational spectra were recorded and, combined with correlated ab initio calculations at the MP2/SBK + (D) and CCSD(T) /SBK + (D) levels of theory for IF 2 − , BrF 2 − , ClF 2 − , XeF 2 , and KrF 2 , show that the infrared spectrum previously reported for IF 2 − is in error. The antisymmetric stretching modes in IF 2 − and BrF 2 − have lower frequencies than the symmetric ones. This highly unusual fact can be explained by mass effects and the enhancement of semi-ionic, 3 center-4 electron bonding by the antisymmetric stretching motion.

Evidence for π bonding in the boron–thiolate compounds (2,4,6-Me3C6H2)2B(SPh) and (2,4,6-Pri3C6H2)B(SPh)2

The use of the bulky aryl substituent groups 2,4,6-Me3C6H2 and 2,4,6-Pri3C6H2 has allowed the structural characterization of two monomeric boron-sulfur compounds (2,4,6-Me3C6H2)2B(SPh)1 and (2,4,6-Pri3C6H2)B(SPh)22. The crystal structures of 1 and 2 show a close alignment between the boron and sulfur p orbitals that is consistent with a π interaction. Furthermore, the B–S distances in 1[1.790(6)] and 2[1.801(6)A] are slightly shorter than the sum of the covalent radii (with allowance made for ionic effects) of boron and sulfur. Variable-temperature 1H and 13C NMR data for 2 indicate an average barrier to rotation around the B–S bond of ca. 12 kcal mol–1. This value is significantly less than the 18.4 kcal mol–1 reported earlier for 1. The lower rotational barrier observed in 2 is consistent with the delocalization of the B–S π bond over the three atom BS2π system which has a similar electronic arrangement to that of an allyl anion. Crystal data at 130 K: 1, triclinic, space group P, a= 7.851(5), b= 11.685(6), c= 13.096(7)A, α= 63.52(2), β= 73.93(2), γ= 74.54(2)°, Z= 2, R= 0.073; 2, monoclinic, space group P21/c, a= 18.373(3), b= 12.713(2), c= 10.844(2)A, β= 99.96(1)°, Z= 4, R= 0.072.