Derivatives of the Dimethylbis(2-pyridyl)borate(1−) Ion: Synthesis and Structure

The syntheses and structures of derivatives of a novel uninegative
bidentate ligand, the dimethylbis(2-pyridyl)borate anion, (py)2BMe2-, are
reported. Lithium dimethylbis(2-pyridyl)borate,
Li(py)2BMe2, was prepared by
adding a solution of bromodimethylborane to a solution of
2-lithiopyridine in a 1:2 molar ratio, respectively;
subsequent hydrolysis afforded hydrogen
dimethylbis(2-pyridyl)borate,
H(py)2BMe2, in 44% yield. Reaction
of
Li(py)2BMe2 with either
bromodimethylborane or bromodiphenylborane afforded the corresponding
tricyclic bis(organo)boronium dimethylbis(2-pyridyl)borate species
R2B(μ-py)2BMe2 (R =
CH3, C6H5) in approximately
90%
yields. Reaction of H(py)2BMe2 with
anhydrous zinc(II) chloride or nickel(II) chloride
hexahydrate in a 4:1
molar ratio gave the tetrahedral complex
bis[dimethylbis(2-pyridyl)borato-N,N ‘]zinc(II),
Zn{(μ-py)2BMe2}2,
or
the square planar complex
bis[dimethylbis(2-pyridyl)borato-N,N ‘]nickel(II),
Ni{(μ-py)2BMe2}2,
respectively.
H(py)2BMe2 is monoclinic,
P21/m, with a =
8.836(2) Å, b = 7.1825(5) Å, c =
9.2789(11) Å, β = 99.81(2)°, V
= 580.29(13) Å3, and Z = 2.
Ph2B(μ-py)2BMe2 is
monoclinic, P21/n, a =
8.0334(12) Å, b = 10.9169(9) Å,
c
= 22.981(2) Å, β = 94.653(9)°, V =
2008.8(4) Å3, and Z = 4.
Zn{(μ-py)2BMe2}2 is
monoclinic, Cc, with a =
8.010(2) Å, b = 31.256(3) Å, c =
18.753(3) Å, β = 90.83(2)°, V =
4694.8(13) Å3, and Z = 8.
Ni{(μ-py)2BMe2}2 is triclinic, P1̄, with
a = 7.675(2) Å, b = 8.819(2) Å,
c = 9.459(2) Å, α = 115.72(3)°, β =
96.89(3)°,
γ = 94.02(3)°, and Z = 1.