Pt羰基簇合物在NaY内的合成机理

利用IR，EXAFS, ~(13)CO同位素交换反应及与NO作用等手段研究了Pt羰基簇合物[Pt_3(CO)_6]~(2-)_n(n＝3,4)在NaY分子筛超笼内的合成机理．在氧化样品Pt~(2+)/NaY上300－373 K的还愿羰基化过程中，首先Pt~(2+)与CO反应生成PtO(CO)物种(波数σ_(CO)＝2110 cm~(-1))，然后聚集成“Pt_3(CO)_6”(σ_(CO)＝2112，1896和1841 cm~(-1))，最后生成深绿色的Pt羰基簇合物Pt_(12)(CO)_(24)]~(2-)/NaY(σ_(CO)＝2080，1824 cm~(-1))．“Pt_3(CO)_6”的羰基在室温下能迅速地与~(13)CO发生交换，而[Pt_3(CO)_6]~(2-)_n(n＝3,4)的羰基与~(13)CO的同位素交换即使在343 K也进行得很慢，室温下，NO能逐步破坏Pt羰基簇合物的层间和层内Pt－Pt键，得到中间物种“Pt_3(CO)_6”和PtO(CO)，同时在气相产生CO_2和N_2O．而由上述两中间物种出发，300－353 K温度下，在CO气氛中的还原羰基化又能可逆地得到原羰基簇合物．

Mechanismic Study of the Synthesis of Intrazeolite Pt Carbonyl Clusters

The mechanism of the synthesis of platinum carbonyl clusters [Pt_3(CO)_6]~(2-)_n(n=3,4) in cages of NaY was studied by IR, EXAFS ~(13)CO exchange reaction and No interaction. The results suggest that oaldized Pt species in NaY cages reacts with CO at 300-373 K to form PtO(CO) (σ_(CO)=2110 cm~(-1)) which aggregates into "Pt_3(CO)_6"(σ_(CO)=2112, 1896 and 1841 cm~(-1)) and eventually converts into dark-green carbonyl cluster [Pt_(12)(CO)_(24)]~(2-). The carbonyl "Pt_3(CO)_6" can exchange with ~(13)CO very quickly at 298 K but the exchange reaction between ~(13)CO and intrazeolite Pt carbonyl clusters [Pt_3(CO)_6]~(2-)_n (n=3,4) proceeds slowly even at enhanced temperature such as 343 K. It is interesting to find that NO breaks successively the intra and inter-trigonal Pt-Pt bonds of the Pt_(12) carbonyl clusters (even at 298 K) and the "Pt_3(C)_6" formed is further reacted to give PtO(CO) with the formation of N_2O and CO_2 in the gas phase. Pt_(12)(CO)_(24)]~(2-) can be reversibly regenerated from the Pt subcarbonyls such as PtO(CO) and "Pt_3(CO)_6" inside NaY by reacting wich CO at 300-353 K.