SYNTHESIS, BE-9 NMR-SPECTROSCOPY, AND STRUCTURAL CHARACTERIZATION OF STERICALLY ENCUMBERED BERYLLIUM COMPOUNDS

The use of the terphenyl substituent -C6H3-2,6-Mes(2) (abbreviated Ar) has permitted the synthesis of several new low-coordinate beryllium c ompounds. Reaction of 1 equiv of LiAr with BeCl2(OEt2)(2) or BeBr2(OEt 2)(2) (1) gives the monomeric complexes ArBeX(OE2) (X=Cl (2); Br(3) fe aturing three-coordinate berylliums. Treatment of 2 with 1 equiv of Li SMes (Mes*=-C6H2-2,4,6-t-Bu-2) affords the three-coordinate thiolate derivative ArBeSMes (OEt2) (4). The reaction of 2 with LiNHPh, LiNHSi Ph3, or LiN(SiMe3)(2) affords the unstable dimer (ArBeNHPh)(2) (5) or the monomers ArBeNHSiPh3(OEt2) (6) and ArBeN(SiMe3)(2) (7). The last i s the first example of a two-coordinate beryllium center in the solid state. The addition of 1 equiv of 2 to NaMo(eta(5)-C5H5)CO)(3) gives t he isocarbonyl complex Ar(THF)(2)Be(OC)(3)Mo(eta(5)H(5)) (8), which fe atures 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)(2)N(SiMe3)(2) (9) and the four-coordinat e monomer Bd{(NSiMe3)(2)CPh}(2) (10). Compounds 1-10 were characterize d by X-ray crystallography, and 1 and 4 and 6-10 were also characteriz ed by H-1, Be-9, and C-13 NMR spectroscopy. X-ray data at 130 K(1-9) o r 185 K (10) with Mo K alpha(lambda=0.710 73 Angstrom (1, 2a, 3, 7, 8) or Cu K alpha(lambda=1.541 78 Angstrom) (2b, 4-6, 9, 10). BeBr2(OEt2) (2) (1), a=11.690(5) Angstrom, b=10.191(3) Angstrom, c=12.131(5) Angst rom, beta=114.67(e)degrees, V=1313.3(9) Angstrom(3), space group P2(1) /n, Z=4, R-1=0.062; ArBeCl(OEt2) (2a), a=13.136(3) Angstrom, b=13.877( 3) Angstrom, c=28.092(6) Angstrom, V=5121(2) Angstrom(3), space group Pbca, Z=8, R-1=0.058; ArBeCl(OEt2) (2b), a=8.857(1) Angstrom, b=8.8977 (9) Angstrom, c=18.198(7) Angstrom, alpha=86.437(8)degrees, <beta<=82. 677(8)degrees, gamma=62.405(7)degrees, V=1260.5(2) Angstrom(3), space group P (1) over bar, Z=2, R-1=0.048; ArBeBr(OEt2) (3), a=8.873(5) Ang strom, b=8.847(5) Angstrom, c=18.251(7) Angstrom, alpha=86.54(4)degree s, beta=83.17(4)degrees, gamma=73.382(8)degrees, V=2195.3(4) Angstrom( 3), space group P (1) over bar, Z=2, R-1=0.062; (ArBeNHPh)(2) . C1H10O (5 . C4H10O), a=11.894(2) Angstrom, b=12.212(2) Angstrom, c=18.709(3) Angstrom, beta=99.24(1)degrees, V=2682.4(7) Angstrom(3), space group Pw(1), Z=2, R-1=0.045; ArBeNHSiPh3(OEt2) (6), a=11.959(2) Angstrom, b= 16.655(2) Angstrom, c=19.718(2) Angstrom, beta=105.368(9)degrees, V=37 86.9(8) Angstrom(3), space group P2(1)/c, Z=4, R-1=0.047; ArBeN(SiMe3) (2) (7), a=12.623(3) Angstrom, b=15.404(4) Angstrom, c=15.502(3) Angst rom, V=3014(1) Angstrom(3), space group Pbcn, Z=4, R-1=0.046; Ar(THF)( 2)Be(OC)(3)Mo-(eta(5)-C5H5). 2C(7)H(8) (8 . 2C(7)H(8)), a=19.111(4) An gstrom, b=11.976(3) Angstrom, b=21.241(5) Angstrom, beta=103. 47(2)deg rees, V=4728(2) Angstrom(3), space group P2(1)/c, Z=4, R-1=0.049; PhC( NSiMe3)(2)(BeCl)(2)N(SiMe3)(2) (9), a=19.996(4) Angstrom, b=14.816(2) Angstrom, c=20.183(4) Angstrom, V=5979(2) Angstrom(3), space group Pbc a, Z=8, R-1=0l043; Be{NSiMe3)(2)CPh}(2) (10), a=20.022(2) Angstrom, b= 9.716(9) Angstrom, c=19.456(2) Angstrom, beta=11.392(8)degrees, V=3524 .1(6) Angstrom(3), space group P2(1)/c, Z=4, R-1=0.075.