Institute of Inorganic Chemistry, Academy of Sciences of the Czech Republic, v.v.i., 250 68 Husinec-Řež, Czech Republic.
Inorg Chem. 2011 Aug 15;50(16):7511-23. doi: 10.1021/ic200374k. Epub 2011 Jul 21.
Metallaborane compounds containing two adjacent metal atoms, [(PMe(2)Ph)(4)MM'B(10)H(10)] (where MM' = Pt(2), 1; PtPd, 7; Pd(2), 8), have been synthesized, and their propensity to sequester O(2), CO, and SO(2) and to then release them under pulsed and continuous irradiation are described. Only [(PMe(2)Ph)(4)Pt(2)B(10)H(10)], 1, undergoes reversible binding of O(2) to form [(PMe(2)Ph)(4)(O(2))Pt(2)B(10)H(10)] 3, but solutions of 1, 7, and 8 all quantitatively take up CO across their metal-metal vectors to form [(PMe(2)Ph)(4)(CO)Pt(2)B(10)H(10)] 4, [(PMe(2)Ph)(4)(CO)PtPdB(10)H(10)] 10, and [(PMe(2)Ph)(4)(CO)Pd(2)B(10)H(10)] 11, respectively. Crystallographically determined interatomic M-M distances and infrared CO stretching frequencies show that the CO molecule is bound progressively more weakly in the sequence {PtPt} > {PtPd} > {PdPd}. Similarly, SO(2) forms [(PMe(2)Ph)(4)(SO(2))Pt(2)B(10)H(10)] 5, [(PMe(2)Ph)(4)(SO(2))PtPdB(10)H(10)] 12, and [(PMe(2)Ph)(4)(SO(2))Pd(2)B(10)H(10)] 13 with progressively weaker binding of the SO(2) molecule. The uptake and release of gas molecules are accompanied by changes in their absorption spectra. Nanosecond transient absorption spectroscopy clearly shows that the O(2) and CO molecules are liberated from the bimetallic binding site with high quantum yields of about 0.6. For 3, in addition to dioxygen release in the triplet ground state, singlet oxygen O(2)((1)Δ(g)) was also detected with a quantum yield <0.01. In most cases, the release and rebinding of the gas molecules can be cycled with little photodegradation of the compounds. Femtosecond transient absorption spectroscopy further reveals that the photorelease of the O(2) and CO molecules, from 3 and 4 respectively, is an ultrafast process taking place on a time scale of tens of picoseconds. For SO(2), the release is even faster (<1 ps), but only in the case of mixed metal PtPd adducts, most probably because of the metal-metal bonding asymmetry in the mixed metal clusters; for the corresponding symmetric Pt(2) and Pd(2) adducts, 5 and 13, the release of SO(2) is significantly slower (>1 ns). All these compounds may have potential to serve as light-triggered local and instantaneous sources of the studied gases.
含有两个相邻金属原子的金属硼烷化合物，[(PMe(2)Ph)(4)MM'B(10)H(10)]（其中 MM'=Pt(2)，1；PtPd，7；Pd(2)，8），已经被合成，并且描述了它们捕获 O(2)、CO 和 SO(2)的倾向以及在脉冲和连续照射下释放它们的能力。只有 [(PMe(2)Ph)(4)Pt(2)B(10)H(10)]，1，经历了 O(2)的可逆结合，形成[(PMe(2)Ph)(4)(O(2))Pt(2)B(10)H(10)]3，但 1、7 和 8 的溶液都通过它们的金属-金属矢量定量地吸收 CO，形成[(PMe(2)Ph)(4)(CO)Pt(2)B(10)H(10)]4、[(PMe(2)Ph)(4)(CO)PtPdB(10)H(10)]10 和[(PMe(2)Ph)(4)(CO)Pd(2)B(10)H(10)]11。晶体学确定的原子间 M-M 距离和红外 CO 伸缩频率表明，CO 分子在 {PtPt} > {PtPd} > {PdPd} 序列中结合强度逐渐减弱。同样，SO(2)形成[(PMe(2)Ph)(4)(SO(2))Pt(2)B(10)H(10)]5、[(PMe(2)Ph)(4)(SO(2))PtPdB(10)H(10)]12 和[(PMe(2)Ph)(4)(SO(2))Pd(2)B(10)H(10)]13，SO(2)分子的结合强度逐渐减弱。气体分子的吸收和释放伴随着它们吸收光谱的变化。纳秒瞬态吸收光谱清楚地表明，O(2)和 CO 分子从双金属结合位点以约 0.6 的高量子产率释放。对于 3，除了三重态基态中的氧气释放外，还检测到单线态氧 O(2)((1)Δ(g))，其量子产率<0.01。在大多数情况下，气体分子的释放和再结合可以循环进行，化合物的光降解很少。飞秒瞬态吸收光谱进一步表明，O(2)和 CO 分子分别从 3 和 4 的光释放是一个在几十皮秒时间尺度上发生的超快过程。对于 SO(2)，释放甚至更快(<1 ps)，但仅在混合金属 PtPd 加合物的情况下，可能是因为混合金属团簇中的金属-金属键不对称；对于相应的对称 Pt(2)和 Pd(2)加合物 5 和 13，SO(2)的释放明显较慢(>1 ns)。所有这些化合物都有可能成为所研究气体的光触发局部和瞬时源。
