Synthesis and Ligand Substitution Reactions of a Mesitylphosphido-Bridged Platinum(II) Dimer

The stable primary phosphine complexes
trans-M(PH2Mes*)2Cl2
(1, M = Pd; 2, M = Pt; Mes* =
2,4,6-(t-Bu)3C6H2) were prepared from
Pd(PhCN)2Cl2 and
K2PtCl4, respectively. Reaction of
Pt(COD)Cl2 (COD = 1,5-cyclooctadiene) with less bulky arylphosphines gives the unstable
cis-Pt(PH2Ar)2Cl2
(3, Ar = Is = 2,4,6-(i-Pr)3C6H2; 4, Ar = Mes
= 2,4,6-Me3C6H2).
Spontaneous dehydrochlorination of 4 or direct reaction
of K2PtCl4
with 2 equiv of PH2Mes gives the insoluble primary
phosphido-bridged dimer
[Pt(PH2Mes)(μ-PHMes)Cl]2
(5),
which was characterized spectroscopically, including solid-state
31P NMR studies. The reversible reaction of
5
with PH2Mes gives
[Pt(PH2Mes)2(μ-PHMes)]2[Cl]2
(6), while PEt3 yields
[Pt(PEt3)2(μ-PHMes)]2[Cl]2
(7), which
on recrystallization forms
[Pt(PEt3)(μ-PHMes)Cl]2
(8). Complex 5 and PPh3 afford
[Pt(PPh3)(μ-PHMes)Cl]2
(9).
Addition of 1,2-bis(diphenylphosphino)ethane (dppe) to
5 gives the dicationic
[Pt(dppe)(μ-PHMes)]2[Cl]2
(10-Cl), which was also obtained as the tetrafluoroborate salt
10-BF4 by deprotonation of
[Pt(dppe)(PH2Mes)Cl][BF4] (11) with Et3N or by reaction
of
[Pt(dppe)(μ-OH)]2[BF4]2
with 2 equiv of PH2Mes. Complexes
8, 9, and
10-Cl·2CH2Cl2·2H2O
were characterized crystallographically.

本研究以二(苯甲腈)二氯化钯[Pd(PhCN)₂Cl₂]和氯铂酸钾(K₂PtCl₄)为原料，分别合成了稳定的一级膦配合物反式-M(PH₂Mes*)₂Cl₂（1：M=Pd；2：M=Pt；其中Mes*=2,4,6-三叔丁基苯基(2,4,6-(t-Bu)₃C₆H₂)）。以1,5-环辛二烯合二氯化铂[Pt(COD)Cl₂，COD=1,5-环辛二烯]与位阻更小的芳基膦反应，得到了不稳定的顺式-Pt(PH₂Ar)₂Cl₂（3：Ar=Is=2,4,6-三异丙基苯基(2,4,6-(i-Pr)₃C₆H₂)；4：Ar=Mes=2,4,6-三甲基苯基(2,4,6-Me₃C₆H₂)）。配合物4可发生自发脱氯化氢反应，氯铂酸钾与2当量的PH₂Mes直接反应也可得到不溶性的一级膦基桥联二聚体[Pt(PH₂Mes)(μ-PHMes)Cl]₂（5），通过包括固态³¹P核磁共振(NMR)在内的波谱学手段对该二聚体进行了表征。配合物5与PH₂Mes发生可逆反应，生成[Pt(PH₂Mes)₂(μ-PHMes)]₂[Cl]₂（6）；而三乙基膦(PEt₃)与5反应则得到[Pt(PEt₃)₂(μ-PHMes)]₂[Cl]₂（7），该产物经重结晶后转化为[Pt(PEt₃)(μ-PHMes)Cl]₂（8）。配合物5与三苯基膦(PPh₃)反应生成[Pt(PPh₃)(μ-PHMes)Cl]₂（9）。向5中加入1,2-双(二苯基膦)乙烷(dppe)，得到二阳离子型配合物[Pt(dppe)(μ-PHMes)]₂[Cl]₂（10-Cl）；该产物也可通过两种路径制备：一是用三乙胺(Et₃N)对[Pt(dppe)(PH₂Mes)Cl][BF₄]（11）进行脱质子化，二是使[Pt(dppe)(μ-OH)]₂[BF₄]₂与2当量的PH₂Mes发生反应，由此得到四氟硼酸盐形式的10-BF₄。对配合物8、9以及10-Cl·2CH₂Cl₂·2H₂O进行了单晶X射线衍射晶体学表征。