Structural Studies of Bis-Catecholate, Bis-Dithiocatecholate, and Tetraalkoxy Diborane(4) Compounds

X-ray structures are described for the bis-catecholate, bis-dithiocatecholate, and tetraalkoxy diborane(4) compounds B₂(1,2-O₂C₆H₄)₂ (1), B₂(1,2-O₂-4-Bu^tC₆H₃) ₂ (2), B₂(1,2-O₂-3,5-Bu^t₂C ₆H₂)₂ (3), B₂(1,2-S₂C₆H₄)₂ (4), B₂(1,2-S₂-4-MeC₆H₃)₂ (5), and B₂(OCH₂CMe₂CH₂O)₂ (6). All the compounds adopt structures in the solid-state in which the B₂O₄ or B₂S₄ units are planar or very nearly so. In compounds 2 and 3, the dihedral angles between the two BO₂C₂ planes are 17.3 and 31.8° respectively whereas in 1, 4 and 5 these angles are exactly 0°. In 6, a 3-fold disorder precluded our obtaining accurate positions for the two boron atoms, yet a dihedral angle of 0° is required by the 3̄ site symmetry. The structure of the bis(Lewis base) adduct of B₂Cl₄ [B₂Cl₄(NHMe₂)₂] (7), is also described and structures of the salt [NH₂Me₂][B(1,2-O₂C₆H ₄)₂] (8)and the NMe₂-bridged dimer [{BCl₂(μ-NMe₂}₂] (9) are available in the Supporting Information. Compound 1 crystallized in the monoclinic space group P2√c with a = 4.746(1) Å, b = 16.427(3) Å, c = 7.053(2) Å, β= 98.59(2)°, and Z = 2. Crystals of 2 were monoclinic, space group P2√c with a = 6.847(1) Å, b = 18.871(5) Å, c = 15.270(2) Å, β = 93.16(2)°, and Z = 4. Crystals of 3 were triclinic, space group P1̄ with a = 9,478(4) Å, b = 10,355(4) Å, c = 15.082(7) Å, α = 105.71(3)°, β = 100.31(4)°. γ = 94.58(3)°, and Z = 2. Crystals of 4 were monoclinic, space group P2√c with a = 15.364(3) Å, b = 4.0502(4) Å, c = 21.532(3) Å, β= 99.320(7)°, and Z = 4. Crystals of 5 were monoclinic, space group P2√c with a = 6.0458(9) Å, b = 7.5319(11) Å, c = 16.552(2) Å, β= 96.291(3)° and Z = 2. Compound 6 crystallized in the rhombohedral space group R3̄m with a = 8.876(2) Å, c = 13.821(3) Å and Z = 3. Crystals of 7 were monoclinic, space group P2√c with a = 11.831(3) Å, b = 19.458(5) Å, c = 14.823(5) Å, β= 96.63-(4)°, and Z = 12.