Synthesis,9Be NMR Spectroscopy, and Structural Characterization of Sterically Encumbered Beryllium Compounds

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Abstract
The use of the terphenyl substituent −C6H3-2,6-Mes2 (abbreviated Ar) has permitted the synthesis of several new low-coordinate beryllium compounds. Reaction of 1 equiv of LiAr with BeCl2(OEt2)2 or BeBr2(OEt2)2 (1) gives the monomeric complexes ArBeX(OEt2) (X = Cl (2); Br (3) featuring three-coordinate berylliums. Treatment of 2 with 1 equiv of LiSMes* (Mes* = −C6H2-2,4,6-t-Bu3) affords the three-coordinate thiolate derivative ArBeSMes*(OEt2) (4). The reaction of 2 with LiNHPh, LiNHSiPh3, or LiN(SiMe3)2 affords the unstable dimer (ArBeNHPh)2 (5) or the monomers ArBeNHSiPh3(OEt2) (6) and ArBeN(SiMe3)2 (7). The last is the first example of a two-coordinate beryllium center in the solid state. The addition of 1 equiv of 2 to NaMo(η5-C5H5)(CO)3 gives the isocarbonyl complex Ar(THF)2Be(OC)3Mo(η5-C5H5) (8), which features four-coordinate beryllium bound to Ar, two THF ligands, and an oxygen from one of the molybdenum-bound carbonyls. Reaction of 2 with a 1:1 mixture of LiN(SiMe3)2 and PhCN affords the six-membered-ring compound PhC(NSiMe3)2(BeCl)2N(SiMe3)2 (9) and the four-coordinate monomer Be{(NSiMe3)2CPh}2 (10). Compounds 1−10 were characterized by X-ray crystallography, and 1 and 4 and 6−10 were also characterized by 1H, 9Be, and 13C NMR spectroscopy. X-ray data at 130 K (1−9) or 185 K (10) with Mo Kα (λ = 0.710 73 Å) (1, 2a, 3, 7, 8) or Cu Kα (λ = 1.541 78 Å) (2b, 4−6, 9, 10). BeBr2(OEt2)2 (1), a = 11.690(5) Å, b = 10.191(3) Å, c = 12.131(5) Å, β = 114.67(3)°, V = 1313.3(9) Å3, space group P21/n, Z = 4, R1 = 0.062; ArBeCl(OEt2) (2a), a = 13.136(3) Å, b = 13.877(3) Å, c = 28.092(6) Å, V = 5121(2) Å3, space group Pbca, Z = 8, R1 = 0.058; ArBeCl(OEt2) (2b), a = 8.857(1) Å, b = 8.8977(9) Å, c = 18.198(7) Å, α = 86.437(8)°, β = 82.677(8)°, γ = 62.405(7)°, V = 1260.5(2) Å3, space group P1̄, Z = 2, R1 = 0.048; ArBeBr(OEt2) (3), a = 8.873(5) Å, b = 8.847(5) Å, c = 18.251(7) Å, α = 86.54(4)°, β = 83.17(4)°, γ = 64.14(4)°, V = 1280(1) Å3, space group P1̄, Z = 2, R1 = 0.071; ArBeSMes*(OEt2)·0.5C6H14 (4·0.5C6H14), a = 9.732(1) Å, b = 11.190(1) Å, c = 21.841(2) Å, α = 75.225(7)°, β = 81.137(8)°, γ = 73.382(8)°, V = 2195.3(4) Å3, space group P1̄, Z = 2, R1 = 0.062; (ArBeNHPh)2·C4H10O (5·C4H10O), a = 11.894(2) Å, b = 12.212(2) Å, c = 18.709(3) Å, β = 99.24(1)°, V = 2682.4(7) Å3, space group P21, Z = 2, R1 = 0.045; ArBeNHSiPh3(OEt2) (6), a = 11.959(2) Å, b = 16.655(2) Å, c = 19.718(2) Å, β = 105.368(9)°, V = 3786.9(8) Å3, space group P21/c, Z = 4, R1 = 0.047; ArBeN(SiMe3)2 (7), a = 12.623(3) Å, b = 15.404(4) Å, c = 15.502(3) Å, V = 3014(1) Å3, space group Pbcn, Z = 4, R1 = 0.046; Ar(THF)2Be(OC)3Mo(η5-C5H5)·2C7H8 (8·2C7H8), a = 19.111(4) Å, b = 11.976(3) Å, b = 21.241(5) Å, β = 103.47(2)°, V = 4728(2) Å3, space group P21/c, Z = 4, R1 = 0.049; PhC(NSiMe3)2(BeCl)2N(SiMe3)2 (9), a = 19.996(4) Å, b = 14.816(2) Å, c = 20.183(4) Å, V = 5979(2)Å3, space group Pbca, Z = 8, R1 = 0.043; Be{(NSiMe3)2CPh}2 (10), a = 20.022(2) Å, b = 9.7161(9) Å, c = 19.456(2) Å, β = 11.392(8)°, V = 3524.1(6) Å3, space group P21/c, Z = 4, R1 = 0.075.