三嗪吡唑类铜配合物的合成、结构及光谱研究

以三齿吡唑-三嗪(类蝎型)化合物2,4-二(3,5-二甲基吡唑)-6-二乙基胺-1,3,5-三嗪(bpz^*eaT)为配体,在无水乙醇和甲醇溶剂中,合成了2个配合物Cu₂(mpz^*eaT-EtO)₂(N₃)₂Cl₂(1)和Cu₂(mpz^*eaT-MeO)₂(N₃)₄(2)(mpz^*eaT-EtO：2-(3,5-二甲基吡唑)-4-乙醇-6-二乙基胺-1,3,5-三嗪;mpz^*eaT-MeO：2-(3,5-二甲基吡唑)-4-甲醇-6-二乙基胺-1,3,5-三嗪)。通过元素分析、红外光谱、紫外光谱、热重分析以及X-ray单晶衍射方法对配合物进行了表征,并分析了其光谱及结构特征。晶体结构表明,配合物1属于三斜晶系,P1空间群,a=0.9949(2)nm,b=1.0216(2)nm,c=1.1480(2)nm,α=115.11(3)°,β=106.99(3)°,γ=100.39(3)°,V=0.9460(3)nm³,Z=1;配合物2属于单斜晶系,P2₁/c空间群,a=1.5464(5)nm,b=1.4008(5)nm,c=0.8905(3)nm,β=103.227(5)°,V=1.8779(10)nm³,Z=2。配合物1和2中的中心铜原子均为五配位,形成扭曲的四角锥构型。     

阴离子调控的含反式-双(苯甲酰丙酮)-1,4-环己二胺银配位聚合物的合成、晶体结构及其荧光性质

将配体反式-双(苯甲酰丙酮)-1,4-环己二胺(L)与AgX(X=NO₃^-,BF₄^-,SbF₆^-,ClO₄^-)进行反应得到4个配合物{[Ag(L)]NO₃}_n(1),{[Ag(L)(H₂O)]BF₄}_n(2),{[Ag₂(L)₃](SbF₆)₂}_n(3),{[Ag(L)]ClO₄}_n(4),并用元素分析,红外和X-射线单晶衍射表征了4个配合物的结构。在固体状态下,配合物1和2都形成2D网状结构的配位聚合物,都有2个不同配位类型的配体,不同的是,配合物1中桥连配体的1,4-环己二胺1,4位的C-N键在直立键上,而配合物2中桥连配体的1,4-环己二胺中1,4位的C-N键在平伏键上;配合物3也有2种不同配位类型的配体,但是与配合物1和2不同,配合物3形成1D配位聚合物;配合物4中的配体只有一种配位类型,配合物4形成2D网状结构。4个配合物中,配合物2,3的阴离子未参与Ag(Ⅰ)配位,配合物1和1的阴离子与Ag(Ⅰ)配位。同时,研究了配体和配合物在室温下的固态荧光性质。     

2-氨甲基-1H-苯并咪唑钴（Ⅱ）和镍（Ⅱ）配合物的合成、晶体结构和抑菌活性

利用双齿配体2-氨甲基-1H-苯并咪唑（AMBI）和硫氰酸钾以及硝酸钴或硝酸镍在甲醇-水中反应制备了2个新的异质同晶配合物trans-[M（AMBI）₂（NCS）₂]（1：M=Co²⁺,2：M=Ni²⁺）。X-射线衍射单晶结构表明：2个配合物属于单斜晶系,C2/2空间群,M（Ⅱ）与来自AMBI的4个氮原子和异硫氰酸根的2个氮原子配位,形成八面体结构。配合物中的N-H…S氢键和π-π相互作用将配合物连接成三维网络结构。用红外光谱、紫外-可见光谱对配合物1和配合物2进行了表征,并对配合物的热稳定性做了研究。选取金黄色葡萄球菌和大肠杆菌作为抑菌菌种,研究了配体AMBI和2个配合物的抑菌能力。     

(1，2-(1H-1，2，4-三唑))乙烷的一维双链Cu(Ⅱ)配合物合成与表征

利用高度柔性的双三唑配体(1,2-(1H-1,2,4-三唑))乙烷(L)和铜盐反应合成了1个新的具有一维双链结构的铜(Ⅱ)配合物{[Cu(cis-L)₂Br]Br·2H₂O}_n(1)。单晶结构表明：配合物1的晶体属于三斜晶系,P1 空间群。在配合物1中双三唑配体采用反式构型,桥联相邻的中心铜离子形成一维双链结构,晶格中游离的Br原子同配位水分子形成了四元环状的Br…O超分子环。测定了配合物1在2~300 K的变温磁化率,结果表明相邻铜离子间存在弱的反铁磁相互作用。     

吡啶-2-羧酸的Dy(Ⅲ)和Tm(Ⅲ)配合物及其与牛血清白蛋白结合性能

以5-(三氟甲基)吡啶-2-羧酸(Htpc)与DyCl₃·6H₂O、TmCl₃·3H₂O构筑了2种异质同晶的单核配合物[M(tpc)₃(H₂O)₃]·H₂O,其中 M=Dy (1)、Tm (2)。配合物 1 和 2 均为单斜晶系,P2₁/c 空间群,中心金属离子为八配位且形成了轻微扭曲的十二面体构型。温度梯度下的荧光和紫外测试表明,2 种配合物均能与牛血清白蛋白(BSA)发生静态猝灭作用,猝灭常数(K_sv)为 10⁵~10⁶ L·mol^-1。配合物与BSA结合过程的ΔH和ΔS均为正值,说明疏水作用在其中扮演重要的角色。25℃时,2种配合物与BSA结合常数约为10⁴ L·mol^-1,表明二者与BSA的具有中等强度的结合力。     

吡啶-2-羧酸的Dy（Ⅲ）和Tm（Ⅲ）配合物及其与牛血清白蛋白结合性能

以5-(三氟甲基)吡啶-2-羧酸(Htpc)与DyCl₃·6H₂O、TmCl₃·3H₂O构筑了2种异质同晶的单核配合物[M(tpc)₃(H₂O)₃]·H₂O,其中M=Dy(1)、Tm(2)。配合物1和2均为单斜晶系,P2₁/c空间群,中心金属离子为八配位且形成了轻微扭曲的十二面体构型。温度梯度下的荧光和紫外测试表明,2种配合物均能与牛血清白蛋白(BSA)发生静态猝灭作用,猝灭常数(K_sv)为105~10⁶ L·mol^-1。配合物与BSA结合过程的ΔH和ΔS均为正值,说明疏水作用在其中扮演重要的角色。25℃时,2种配合物与BSA结合常数约为10⁴ L·mol^-1,表明二者与BSA的具有中等强度的结合力。     

Ru(Ⅱ)和Ru(Ⅲ)配合物[Ru(bpy)(PH3)(-C≡CC6H4NO2-p)Cl]m(m=0，+1)的光谱性质的密度泛函-含时密度泛函理论研究

我们利用DFT中的B3LYP方法优化了Ru(Ⅱ)配合物和氧化的Ru(Ⅲ)配合物[Ru(bpy)(PH₃)(-C≡CC₆H₄NO₂-p)Cl]^m[bpy=2，2′-bipyridine;m=0 (1)，+1 (1⁺)]的基态几何结构，得到的几何参数与实验结果吻合的很好。采用TDDFT方法，得到了配合物1和1⁺的激发态电子结构和电子吸收光谱。研究结果表明，配合物1和1⁺随着氧化过程的发生，光谱性质也发生变化，Ru(Ⅱ)配合物的低能吸收被指认为MLCT/LLCT混合跃迁，而氧化的Ru(Ⅲ)配合物1⁺的低能吸收具有LMCT跃迁性质。     

基于两个取代四甲基环戊二烯基配体的金属羰基化合物的合成及晶体结构

配体[C₅Me₄HR][R=4-BrPh(1),(MeC₅H₃N)CH₂(2)]分别与Mo(CO)₆,Ru₃(CO)₁₂和Fe(CO)₅在二甲苯中加热回流,得到了6个双核配合物trans-[η⁵-C₅Me₄R]₂Mo₂(CO)₆(3,4),trans-[(η⁵-C₅Me₄R)Ru(CO)(μ-CO)]₂(5,6)和trans-[η⁵-(C₅Me₄R)Fe(CO)(μ-CO)]₂(7,8,).通过元素分析、红外光谱、核磁共振氢谱对配合物的结构进行了表征,并用X-射线单晶衍射法测定了配合物3,5,6和8的结构.     

阴离子调控的含反式-双(苯甲酰丙酮)-1,4-环己二胺银配位聚合物的合成、晶体结构及其荧光性质

将配体反式-双(苯甲酰丙酮)-1,4-环己二胺(L)与AgX(X=NO₃^-, BF₄^-, SbF₆^-, ClO₄^-)进行反应得到4个配合物{[Ag(L)]NO₃}_n(1), {[Ag(L)(H₂O)]BF₄}_n(2), {[Ag₂(L)₃](SbF₆)₂}_n(3), {[Ag(L)]ClO₄}_n(4),并用元素分析,红外和X-射线单晶衍射表征了4个配合物的结构。在固体状态下,配合物1和2都形成2D网状结构的配位聚合物,都有2个不同配位类型的配体,不同的是,配合物1中桥连配体的1,4-环己二胺1,4位的C-N键在直立键上,而配合物2中桥连配体的1,4-环己二胺中1,4位的C-N键在平伏键上;配合物3也有2种不同配位类型的配体,但是与配合物1和2不同,配合物3形成1D配位聚合物;配合物4中的配体只有一种配位类型,配合物4形成2D网状结构。4个配合物中,配合物2,3的阴离子未参与Ag(Ⅰ)配位,配合物1和4的阴离子与Ag(Ⅰ)配位。同时,研究了配体和配合物在室温下的固态荧光性质。     

二氰氨根[N(CN)2-]/三氰甲根[C(CN)3-]桥联双核钌RuⅡRuⅢ混合价配合物的设计合成、表征和电子传递行为

trans-[XRu(py)₄(NO)]²⁺(X=Cl，Br)与等物质的量的NaN₃在甲醇中反应后生成中间体trans-[XRu(py)₄(CH₃OH)]⁺，它再与过量的Na[N(CN)₂]或K[C(CN)₃]反应后生成单核配合物trans-XRu(py)₃L(X=Cl，Br，L=N(CN)₂^-，C(CN)₃^-)。单核配合物XRu(py)₄L与[X′Ru(py)₄(CH₃OH)]⁺进行分子组装，生成了一系列双核钌配合物trans-[X(py)₄Ru(μ-L)Ru(py)₄X′]⁺。用等物质的量的NOBF₄或(NH₄)₂[Ce(NO₃)₆]氧化这些Ru^ⅡRu^Ⅱ双核钌配合物，得到了一系列Ru^ⅡRu^Ⅲ混合价配合物trans-[X(py)₄Ru(μ-L)Ru(py)₄X′]²⁺。N(CN)₂-桥联的Ru^ⅡRu^Ⅲ混合价配合物在近红外区存在中等强度的吸收，起源于混合价态间的电荷跃迁(Intervalence Charge Transfer，简称为IVCT)，且其最大吸收波长随着溶剂极性的改变而发生变化，它们属于Class Ⅱ类型的混合价化合物；而C(CN)₃-桥联的Ru^ⅡRu^Ⅲ混合价配合物在近红外的吸收要强得多，且溶剂极性的改变对IVCT最大吸收波长基本无影响，它们属于介于价态定域与离域之间的混合价配合物。     

具有C2对称的氮磷-氧磷配体双噁唑啉磷乙烷的合成及在不对称催化加氢中的应用

利用易得的光学纯N-甲基氨基醇与1,2-双(二氯磷)乙烷缩合合成了一类新的具有C₂对称轴的氮磷-氧磷配体(R,R)-双噁唑啉磷乙烷(BOAPE) 1～4. 该类配体不仅具有C₂对称结构和刚性五元环, 还具有富电子特性, 利用500 MHz进行了¹H NMR, ³¹P NMR, ¹³C NMR表征. 与这些配体配位形成的Rh配合物用于N-苯甲酰基脱氢丙氨酸衍生物和α-功能化酮不对称加氢, 分别可以得到99%和98%的ee. 这类配体比它们相对应的非C₂对称的氮磷-氧磷化合物(AMPP)配体具有更高的对映选择性. 在这四个新的配体中配体(R,R)-Ph-BOAPE (2)的催化性能最优. 催化剂[Rh(COD)(R,R)-Ph-BOAPE]BF₄的半反应周期t_1/2和周转频率(TOF)在N-苯甲酰基肉桂酸甲酯的不对称加氢反应中分别为12 min和6.5 min^－1.     

Synthesis,spectroscopy and structure of cis,cis,trans:N,N;P,P;S,S-[bis(triphenylphosphine)] [bis(pyrimidine-2-thiolato)]ruthenium(II)

Reaction of RuCl₂(PPh₃)₃with pyrimidine-2-thione (HpymS) in a 1:2?mol ratio in dry benzene in the presence of triethylamine as base yielded a complex of stoichiometry [Ru(pymS)₂(PPh₃)₂] (1). This has been characterized using analytical data and IR, ¹H, ¹³C and ³¹P NMR spectroscopy. ¹H NMR confirmed the deprotonation of HpymS. ³¹P NMR spectra showed a single peak confirming equivalent P atoms. Complex 1 crystallizes in space group Pī and HpymS acts as a η²-N,S-deprotonated bidentate anionic ligand. The coordination geometry around the Ru center is distorted octahedral with cis dispositions of P atoms, as well as two N atoms of pymS^– and trans S atoms of pymS^–. Important bond distances and angles are: Ru–N, 2.119(2), 2.106(2); Ru–S, 2.4256(8), 2.4413(8); and Ru–P, 2.3266(7), 2.3167(7)?Å; P(2)–Ru(1)–P(1), 96.07(3); N(21)–Ru(1)–N(11), 83.46(9); and S(1)–Ru(1)–S(2), 153.02(3)°.     

On the behaviour of Ru(I) and Ru(II) carbonyl acetates in the presence of H2 and/or acetic acid and their role in the catalytic hydrogenation of acetic acid

The reactivity of phosphine substituted ruthenium carbonyl carboxylates Ru(CO)₂(MeCOO)₂(PBu₃)₂, Ru₂(CO)₄(μ-MeCOO)₂(PBu₃)₂, Ru₄(CO)₈(μ-MeCOO)₄(PBu₃)₂ with H₂ and/or acetic acid was investigated by IR and NMR spectroscopy to clarify their role in the catalytic hydrogenation of acetic acid. Evidences were collected to suggest hydride ruthenium complexes as the catalytically active species. Equilibria among ruthenium hydrides and carboxylato complexes take place in the presence of hydrogen and acetic acid, that is in the conditions of the catalytic reaction. Nevertheless the presence of acetic acid reduces the rate of the formation of hydrides. Working at a very high temperature (180°C) polynuclear phosphido hydrides such as [Ru₆(μ-H)₆(CO)₁₀(μ-PHBu)(μ-PBu₂)₂(PBu₃)₂(μ₆-P)] were formed. These phosphido clusters are suggested as the resting state of the catalytic system.Furthermore the bi- or tetranuclear Ru(I) carboxylato complexes react with acetic acid giving a mononuclear ruthenium complex Ru(CO)₂(MeCOO)(μ-MeCOO)(PBu₃), containing a monodentate and a chelato acetato ligands. This complex was spectroscopically characterised. Its identity and structure were confirmed by its reactivity with stoichiometric amount of PPh₃ to give Ru(CO)₂(MeCOO)₂(PBu₃)(PPh₃), a new mononuclear ruthenium carbonyl carboxylate containing two different phosphines, that was fully characterised.     

Ruthenium(II) complexes of aroylhydrazones: structural,electrochemical and electrostatic interactions with DNA

Four Ru(II) complexes with tridentate ligands viz. (4-hydroxy-N′-(pyridin-2-yl-ethylene) benzohydrazide [Ru(L¹)(PPh₃)₂(Cl)] (1), N′-(pyridin-2-yl-methylene) nicotinohydrazide [Ru(L²)(PPh₃)₂(Cl)] (2), N′-(1H-imidazol-2-yl-methylene)-4-hydroxybenzohydrazide [Ru(L³)(PPh₃)₂(Cl)] (3), and N′-(1H-imidazol-2-yl-methylene) nicotinohydrazide [Ru(L⁴)(PPh₃)₂(Cl)] (4) have been synthesized and characterized. The methoxy-derivative of L³H (abbreviated as L³H*) exists in E configuration with torsional angle of 179.4° around C₇-N₈-N₉-C₁₀ linkage. Single crystal structures of acetonitrile coordinated ruthenium complexes of 1 and 3 having compositins as [Ru(L¹)(PPh₃)₂(CH₃CN)]Cl (1a) and [Ru(L³)(PPh₃)₂(CH₃CN)]Cl (3a) revealed coordination of tridentate ligands with significantly distorted octahedral geometry constructed by imine nitrogen, heterocyclic nitrogen, and enolate amide oxygen, forming a cis-planar ring with trans-placement of two PPh₃ groups and a coordinated acetonitrile. Ligands (L¹H-L⁴H) and their ruthenium complexes (1–4) are characterized by ¹H, ¹³C, ³¹P NMR, and IR spectral analysis. Ru(II) complexes have reversible to quasi-reversible redox behavior having Ru(II)/Ru(III) oxidation potentials in the range of 0.40–0.71 V. The DNA binding constants determined by absorption spectral titrations with Herring Sperm DNA (HS-DNA) reveal that L⁴H and 1 interact more strongly than other ligands and Ru(II) complexes. Complexes 1–3 exhibit DNA cleaving activity possibly due to strong electrostatic interactions while 4 displays intercalation.     

The lewis acidic ruthenium-complex-catalyzed addition of beta-diketones to alcohols and styrenes is in fact Brønsted acid catalyzed

The perchlorate salt of the dicationic bipy–ruthenium complex cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂]²⁺ effectively catalyzes addition of β‐diketones to secondary alcohols and styrenes to yield the α‐alkylated β‐diketones. In a catalytic addition reaction of acetylacetone to 1‐phenylethanol, the κ²‐acetylacetonate complex [Ru(6,6′‐Cl₂bipy)₂(κ²‐acac)]ClO₄ was isolated after the catalysis; this complex is readily synthesized by reacting cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂](ClO₄)₂ with acetylacetone. [Ru(6,6′‐Cl₂bipy)₂(κ²‐acac)]ClO₄ is unreactive toward 1‐phenylethanol in the presence of HClO₄; it also fails to catalyze the addition of acetylacetone to 1‐phenylethanol. On the basis of these observations, it is proposed and confirmed by independent experiments that the catalytic addition of β‐diketones to the secondary alcohols is in fact catalyzed by the Brønsted acid HClO₄, which is generated by the reaction of cis‐[Ru(6,6′‐Cl₂bipy)₂(H₂O)₂](ClO₄)₂ with the β‐diketone.     

Platinum–Ruthenium Cluster Complexes from the Reaction of Ru<Subscript>3</Subscript>(CO)<Subscript>12</Subscript> with Pt(PBu<Superscript>t</Superscript><Subscript>3</Subscript>)<Subscript>2</Subscript>

Three new platinum–ruthenium complexes: Pt₃Ru₃(PBu^t ₃)₃(CO)₁₂, 8, Pt₅Ru₃(PBu^t ₃)₃(CO)₁₂, 9 and PtRu₃(PBu^t ₃)₂(CO)₈(μ₃-PBu^t)(μ-H)₂, 10 were obtained from the reaction of Ru₃(CO)₁₂ with Pt(PBu^t ₃)₂. Compound 8 was obtained from this reaction when conducted at 25 °C. Compounds 9 and 10 were obtained when the reaction was conducted at 68 °C. The structure of 8 consists of a central triangular cluster of three ruthenium atoms with one Pt(PBu^t ₃) group bridging each of the three Ru–Ru bonds. The structure of 9 consists of a capped pentagonal bipyramidal cluster of eight metal atoms that is formed formally by the addition of two platinum atoms to 8. The structure of 10 contains a triangular cluster of three ruthenium atoms with a Pt(PBu^t ₃) group bridging one of the Ru–Ru bonds. A t-butyl phosphido ligand formed by degradation of a molecule of PBu^t ₃ bridges the three ruthenium atoms. This report is dedicated to the memory of Professor F. A. Cotton for his many pioneering contributions to inorganic and metal cluster chemistry.     

含能富勒烯吡咯烷衍生物的合成及工艺研究

利用Prato反应合成分离出了新型含硝基富勒烯吡咯烷衍生物1, 并对其工艺条件进行了研究, 探讨了反应物计量比、温度及时间对产物1产率的影响, 得到了合成产物1的最佳工艺条件: C₆₀, 间硝基苯甲醛和N-甲基甘氨酸的物质的量比为1∶1∶2, 温度为100 ℃, 反应时间为16 h, 此时产物1产率达到94.8%(以消耗的C₆₀计). 同时用UV-Vis, FT-IR, ¹H NMR, ¹³C NMR and MS spectra等光谱手段确定了产物1的分子结构.     

2-取代硫醚-5-(3,4,5-三甲氧基苯基)-1,3,4-噻二唑类化合物的合成、结构与体外抗癌活性

以天然产物没食子酸为原料经醚化、酯化、酰肼化、成盐、闭环、硫醚化六步反应合成了6个2-取代硫醚-5-(3,4,5-三甲氧基苯基)-1,3,4-噻二唑类衍生物, 釆用铟催化下水相合成目标化合物8, 具有反应条件温和, 合成收率高的特点; 用IR, ¹H NMR, ¹³C NMR和元素分析对各化合物进行了表征及结构确证, 并用X射线单晶衍射法测定了化合物8a [2-(2-氯-5-吡啶甲基)硫醚-5-(3,4,5-三甲氧基苯基)-1,3,4-噻二唑]的晶体结构, 采用MTT法进行了新化合物抑制PC3和BGC-823癌细胞体外试验, 结果表明在5μmol•L^－1浓度下化合物8e对PC3的抑制活性为55.71%. 化合物8b对BGC-823细胞抑制活性为66.21%.     

Synthesis,spectroscopic characterization and antibacterial sensitivity of some chloro dimethylsulfoxide/tetramethylenesulfoxide ruthenium(II) and ruthenium(III) complexes with 2-aminobenzothiazole

Synthesis and characterization of seven ruthenium(II) and ruthenium(III) complexes of sulfoxide with 2-aminobenzothiazole are reported. Three different formulations exist: [cis,cis,cis-RuCl₂(SO)₂(2-abtz)₂] and [trans,trans,trans-RuCl₂(SO)₂(2-abtz)₂] and [trans-RuCl₄(SO)(2-abtz)] ^? [X]⁺ (where SO?=?dimethyl sulfoxide (dmso) or tetramethylenesulfoxide (tmso); 2-abtz?=?2-aminobenzothiazole and [X]⁺?=?[H(abtz)]⁺, [Na⁺]. These complexes were characterized by elemental analyses, conductivity measurements, magnetic susceptibility, FTIR, ¹H NMR, ¹³C{¹H} NMR and electronic spectroscopy. Some of the complexes were screened for their antibacterial activity and are found to be potent against the gram negative bacteria Escherichia coli.     

High Nuclearity Bimetallic Rhodium–Palladium Carbonyl Cluster Complexes. Synthesis and Characterization of Rh6(CO)16[Pd(PBu t 3)]3 and Rh6(CO)16[Pd(PBu t 3)]4

The reaction of Rh₄(CO)₁₂ with Pd(PBu ^t ₃)₂ yielded the high nuclearity bimetallic hexarhodium-tripalladium cluster complex Rh₆(CO)₁₆[Pd(PBu ^t ₃)]₃, 10, in 11% yield. Compound 10 was converted to the hexarhodium-tetrapalladium cluster Rh₆(CO)₁₆[Pd(PBu ^t ₃)]₄, 11, in 62% yield by reaction with an additional quantity of Pd(PBu ^t ₃)₂. Both compounds were characterized crystallographically. Structurally, both compounds consist of an octahedral cluster of six rhodium atoms with sixteen carbonyl ligands analogous to that of the known compound Rh₆(CO)₁₆. Compound 10 also contains three Pd(PBu ^t ₃) groups that bridge three Rh–Rh bonds along edges of the Rh₆ octahedron to give an overall D₃ symmetry to the Rh₆Pd₃ cluster. Compound 11 contains four edge bridging Pd(PBu ^t ₃) groups distributed across the Rh₆ octahedron to give an overall D_2d symmetry to the Rh₆Pd₄ cluster. Each Rh–Pd connection in both compounds contains a bridging carbonyl ligand that helps to stabilize the bond between the Pd(PBu ^t ₃) groups and the Rh atoms. Both compounds can be regarded as Pd(PBu ^t ₃) adducts of Rh₆(CO)₁₆.