磷硼加合物n-Pr3P和I3P的晶体结构分析
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"这篇学术论文详细探讨了磷-硼加合物n-Pr3P[BBr3]和I3P[BBr3]的晶体结构。通过X射线晶体学方法，作者们确定了这两个化合物的精确几何参数。"
在文章中，n-Pr3P[BBr3]的晶体结构被描述为三棱形，属于空间群P4c1，其晶格常数为a = 11.5423(6) Å，b = 11.5423(6) Å，c = 13.8066(7) Å，Z值为4，表明每个单元晶胞中有4个分子。而I3P[BBr3]的结构则呈现正交，属于空间群Pnma，晶格常数为a = 12.761(2) Å，b = 11.427(1) Å，c = 7.3728(7) Å，同样Z值为4。
研究的重点在于磷-硼(P-B)键的性质。在n-Pr3P[BBr3]中，P-B键的长度测量为1.95(1) Å，而在I3P[BBr3]中，该距离显著增加到2.01(1) Å。这种差异可能与磷卤化物(PX3，X = Cl, Br, I)和烷基膦的不同路易斯碱性有关。作者们推测，磷卤化物和烷基膦之间的电荷转移和键合情况在这些供体-受体复合物中可能有所不同。
为了进一步理解这些化合物的电子结构，论文进行了自然键轨道(NBO)分析，这是一种常用的理论工具，用于研究分子内的电子分布和键合特性。此外，通过拉曼光谱和红外光谱获得了n-Pr3P[BBr3]的部分频率，并与I3P[BBr3]的正常模振动进行了比较，这有助于识别和解析这两种化合物的振动模式，从而揭示它们的化学行为。
关键词涵盖了晶体结构、NBO分析以及路易斯碱性，显示了本文的核心研究领域。这些发现对于理解磷-硼化合物的化学性质，特别是在材料科学、无机化学和合成化学等领域，具有重要的理论和实际意义。通过深入研究这些复杂的化学键合和电子结构，科学家们可以设计出新的功能材料或改进现有的化学反应路径。
Crystal Structures of the Phosphorus-Boron Adducts n-Pr
3
P ´ BBr
3
and I
3
P ´ BBr
3
Christoph Aubauer, Katherine Davidge
1)
, Thomas M. Klapo
È
tke*, Peter Mayer, Holger Piotrowski,
and Axel Schulz
Munich, Ludwig-Maximilians-UniversitaÈt, Department of Chemistry
Received June 7
th
2000.
Abstract. The structures of the phosphorus-boron adducts n-
Pr
3
P ´ BBr
3
(trigonal, space group P 4 c1, Z =4,
a = 11.5423(6), b = 11.5423(6) and c = 13.8066(7) A
Ê
) and
I
3
P ´ BBr
3
(orthorhombic, space group Pnma, Z =4,
a = 12.761(2), b = 11.427(1), c = 7.3728(7) A
Ê
) were deter-
mined by X-ray crystallography. The P±B distance of
2.01(1) A
Ê
in I
3
P ´ BBr
3
is significantly longer than the P±B
bond in n-Pr
3
P ´ BBr
3
(1.95(1) A
Ê
). The different Lewis basi-
city of phosphorus halides, PX
3
(X = Cl, Br, I), and alkylpho-
sphines is discussed. The charge transfer and the bond situa-
tion in these donor-acceptor complexes is studied on the
basis of NBO analysis. Selected frequencies of n-Pr
3
P ´ BBr
3
obtained by Raman and infrared spectroscopy are assigned
and compared with the normal modes of I
3
P ´ BBr
3
.
Keywords: Crystal structure; NBO analysis; Lewis basicity;
Phosphorus boron halide complexes; Vibrational spectro-
scopy
Kristallstrukturen der Phosphor-Bor Addukte n-Pr
3
P ´ BBr
3
und I
3
P ´ BBr
3
Inhaltsu
È
bersicht. Die Strukturen der Phosphor-Bor-Addukte
n-Pr
3
P ´ BBr
3
(trigonal, Raumgruppe P 3 c1, Z =4,
a = 11.5423(6), b = 11.5423(6) and c = 13.8066(7) A
Ê
) und
I
3
P ´ BBr
3
(orthorhombisch, Raumgruppe Pnma, Z =4,
a = 12.761(2), b = 11.427(1), c = 7.3728(7) A
Ê
) wurden durch
RoÈntgenstrukturanalyse aufgeklaÈrt. Der P±B-Abstand in
I
3
P ´ BBr
3
ist mit 2.01(1) A
Ê
bedeutend laÈnger als in
n-Pr
3
P ´ BBr
3
(1.95(1) A
Ê
). Die unterschiedliche Lewis-Basizi-
taÈt von Phosphorhalogeniden, PX
3
(X = Cl, Br, I), und Al-
kylphosphinen wird diskutiert. Der Ladungstransfer und die
chemische Bindung in diesen Donor-Akzeptor-Komplexen
werden auf der Basis von NBO-Analysen erklaÈrt. Raman-
und Infrarot-Spektren von n-Pr
3
P ´ BBr
3
werden mit den
Normalschwingungen von I
3
P ´ BBr
3
verglichen.
Introduction
Boron trihalides are widely used in chemical synthesis
as Lewis acids and alkyl phosphines as Lewis bases.
Both species are of great importance in modern chem-
istry [1]. The central boron atom has only six valence
electrons and therefore, it represents an electron defi-
cient species which shows a strong affinity for electron
density especially from lone pairs of a donor molecule.
PX
3
(X = Cl, Br, I) molecules represent only weak do-
nor molecules whereas alkyl phosphines form stronger
Lewis acid-base complexes. Although Lewis acid-base
complexes of phospines with boron halides have been
known for over four decades, only a few X-ray data of
these species are available [2±5].
Recently, we have been interested in the calculation
of Raman and IR spectra of phosphorus halide com-
pounds and phosphorus boron halide adducts. Vibra-
tional assignments of the normal modes for these Le-
wis acid-base adducts have been made on the basis of
comparison between theoretically obtained and ex-
perimentally observed Raman and IR data. Moreover
we have investigated the bonding and electron trans-
fer within these species [6±8].
Previous work has shown that the donor behavior
of phosphorus trihalides depends on the electronega-
tivity of the halogen substituents [9, 10]. For the phos-
phorus trihalides, the order of stability for the 1 : 1 do-
nor-acceptor complexes with boron trihalides is
PCl
3
< PBr
3
< PI
3
[11].
In this paper we want to report on the structural
and electronic properties of n-Pr
3
P ´ BBr
3
and
I
3
P ´ Br
3
.
Results and Discussion
The Lewis acid-base adduct n-Pr
3
P ´ BBr
3
(1) was pre-
pared from the reaction of tri-n-propylphosphine with
boron tribromide in pentane in a 1 : 1 molar ratio
under nitrogen and recrystallized from toluene.
I
3
P ´ BBr
3
(2) was prepared according to the literature
[2]. Crystals of 2 were obtained by recrystallization
from CS
2
.
Z. Anorg. Allg. Chem. 2000, 626, 2373±2378 Ó WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2000 0044±2313/00/6262373±2378 $ 17.50+.50/0 2373
1)
present address: Department of Chemistry, University of
Glasgow, Glasgow G12 8QQ, Scotland (U.K.)
* Prof. Dr. Thomas M. KlapoÈtke,
Department of Chemistry, Ludwig-Maximilians-UniversitaÈt,
Butenandtstr. 5±13 (Haus D), D-81377 Munich, Germany
e-mail:tmk@cup.uni-muenchen.de
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