Reaction of nitrogen chelates with the [Rh-2](4+) core: Bis-chelate products and demonstration of reversible, chelate-based reduction processes
Reaction of nitrogen chelates with the [Rh-2](4+) core: Bis-chelate products and demonstration of reversible, chelate-based reduction processes
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DOI：
10.1021/ic9610288
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发表时间：
1997-05-21
影响因子：
4.6
通讯作者：
Christou, G
中科院分区：
文献类型：
--
作者：
Crawford, CA;Matonic, JH;Christou, G
介绍了一系列以羧酸盐和n基螯合物为配体的[Rh-2]（4+）配合物的制备及其性质。Rh-2(O2CR)(4)(MeOH)(2) (R = Me (1), Et (2), Ph（3)或CF3(4)）用2等量的2,2'-联吡啶（bpy）在回流MeCN中处理可得到[Rh-2(O2CR)(2)(bpy)(2)]（2+）阳离子（在配合物5-9中）。1与1,10-菲罗啉（phen）、4,4'-二甲基-2,2'-联吡啶（Me(2)bpy）、4,4'-二苯基-2,2'-联吡啶（Ph(2)bpy）和4,7-二苯基-1,10-菲罗啉（Ph(2)phen）反应得到类似阳离子的配合物10-13。复杂的6,[Rh-2 (OAc) (2) (bpy) (2) (MeCN) (2)] PF6(2)。2MeCN在单斜空间群P2(1)/a中结晶，晶胞参数为：a = 14.433(2)埃，b = 12.810(1)埃，C = 22.78(3)埃，β = 104.42(3)度，Z = 4, V = 3971.2埃(3)。配合物9，[Rh-2(O2CCF3)(4)(bpy)(2)]。在20℃条件下，Me2CO在三斜空间群中结晶，晶胞参数为：a = 14.260(4)埃，b = 15.375(4)埃，C = 9.709(2)埃，alpha = 105.98(2)度，beta = 97.49(2)度，gamma = 70.32(2)度，Z = 2, V = 1925.2埃(3)。6a和9都含有一个单键[Rh-2]（4+）单元，其中两个顺式桥接RCO2-基团和两个synbpy螯合基团在Rh-Rh载体上呈近重叠构象。反应(Rh-2 (tpy) (2) (MeCN) (4)] (BF4) (4) (15) (tpy = 2, 2 ': 6 ', 2”-terpyridine) NBu4n (O2CPh)给(Rh-2 (O2CPh) (tpy) (2) (MeCN) (2)] (BF4)(3)。MeCN(16)。配合物16在三斜空间群中结晶，晶胞参数为：a = 11.684(4)埃，b = 20.373(8)埃，C = 10.451(3)埃，alpha = 93.47(2)度，beta = 110.53(1)度，gamma = 100.03(2)度，Z = 2, V = 2274.1埃(3)。16的阳离子由一个[Rh-2]（4+）单元和一个桥接的PhCO2-基团和两个螯合的tpy基团组成。配合物6-13和16的溶液H-1 NMR性质表明配合物在溶解时仍保持固态结构。采用循环伏安法（CV）和差分脉冲伏安法（DPV）研究了6-13和16在MeCN中的电化学性能。双（bpy）和-(phen)配合物6-8、10和11对二茂铁在-0.83 ~ -0.91 V范围内发生可逆单电子还原，并发生不可逆还原和不可逆氧化；Ph(2)bpy（12）和Ph(2)phen（13）配合物在-0.61 ~ -0.76电压下发生双电子可逆还原，在0.68 ~ 0.89 V电压下发生可逆单电子氧化。考虑作为羧酸盐和螯合物同一性函数的电位可以得出结论，还原是基于配体（螯合物）的。对模型化合物[Rh-2(O2CH)(2)(bpy)(2)(HCN)(2)]（2+）的扩展Huckel计算支持了这一点，表明LUMO是一个基于bpy的轨道，由两个bpy π *轨道的同相sigma重叠组成，每个synbpy基团上都有一个轨道。而配合物16则没有可逆还原过程。配合物6b [Rh-2(OAc)(2)(bpy)(2)(MeCN)(2)]（BF4)(2)）在四氢呋喃中可被四氢呋喃钠还原得到高产的深蓝[Rh-2(OAc)(2)(bpy)(2)(MeCN)(2)](BF4)（14）。在-0.99 V下控制6a在MeCN中的电位电解，以及在酒精中加热6a或6b的溶液，也可以产生14的阳离子。
The preparations and properties are described of a series of [Rh-2](4+) complexes possessing carboxylates and N-based chelates as ligands. Treatment of Rh-2(O2CR)(4)(MeOH)(2) (R = Me (1), Et (2), Ph (3) or CF3 (4)) with 2 equiv of 2,2'-bipyridine (bpy) in refluxing MeCN leads to the [Rh-2(O2CR)(2)(bpy)(2)](2+) cation (in complexes 5-9). Reaction of 1 with 1,10-phenanthroline (phen), 4,4'-dimethyl-2,2'-bipyridine (Me(2)bpy), 4,4'-diphenyl-2,2'-bipyridine (Ph(2)bpy), and 4,7-diphenyl-1,10-phenanthroline (Ph(2)phen) leads to the analogous cations of complexes 10-13. Complex 6a, [Rh-2(OAc)(2)(bpy)(2)(MeCN)(2)](PF6)(2) . 2MeCN, crystallizes in monoclinic space group P2(1)/a with the following cell parameters at -172 degrees C: a = 14.433(2) Angstrom, b = 12.810(1) Angstrom, c = 22.78(3) Angstrom, beta = 104.42(3)degrees, Z = 4, and V = 3971.2 Angstrom(3). Complex 9, [Rh-2(O2CCF3)(4)(bpy)(2)]. Me2CO crystallizes in triclinic space group with the following cell parameters at 20 degrees C: a = 14.260(4) Angstrom, b = 15.375(4) Angstrom, c = 9.709(2) Angstrom, alpha = 105.98(2)degrees, beta = 97.49(2)degrees, gamma = 70.32(2)degrees, Z = 2, and V = 1925.2 Angstrom(3). Both 6a and 9 contain a singly-bonded [Rh-2](4+) unit with two cis bridging RCO2- groups and two syn-bpy chelate groups in a near-eclipsed conformation about the Rh-Rh vector. Reaction of [Rh-2(tpy)(2)(MeCN)(4)](BF4)(4) (15) (tpy = 2,2':6',2 ''-terpyridine) with NBu4n(O2CPh) gives [Rh-2(O2CPh)(tpy)(2)(MeCN)(2)](BF4)(3) . MeCN (16). Complex 16 crystallizes in triclinic space group with the following cell parameters at -168 degrees C: a = 11.684(4) Angstrom, b = 20.373(8) Angstrom, c = 10.451(3) Angstrom, alpha = 93.47(2)degrees, beta = 110.53(1)degrees, gamma = 100.03(2)degrees, Z = 2, and V = 2274.1 Angstrom(3). The cation of 16 consists of a [Rh-2](4+) unit with a bridging PhCO2- group and two chelating tpy groups. The solution H-1 NMR properties of complexes 6-13 and 16 show the complexes to retain their solid-state structures on dissolution. The electrochemical properties of 6-13 and 16 were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) in MeCN. The bis(bpy) and -(phen) complexes 6-8, 10, and 11 show a reversible, one-electron reduction in the range -0.83 to -0.91 V vs ferrocene and an additional, irreversible reduction and an irreversible oxidation; the Ph(2)bpy (12) and Ph(2)phen (13) complexes show a two-electron reversible reduction at -0.61 to -0.76 and a reversible one-electron oxidation at 0.68-0.89 V. Consideration of the potentials as a function of carboxylate and chelate identity leads to the conclusion that the reductions are ligand (chelate)-based. This is supported by an extended Huckel calculation on the model compound [Rh-2(O2CH)(2)(bpy)(2)(HCN)(2)](2+), which shows the LUMO to be a bpy based orbital comprising in-phase, sigma overlap of two bpy pi* orbitals, one on each of the syn-bpy groups. In contrast, complex 16 shows no reversible reduction processes.Complex 6b, [Rh-2(OAc)(2)(bpy)(2)(MeCN)(2)](BF4)(2), in MeCN may be reduced with sodium acenaphthylenide in THF to give deep blue [Rh-2(OAc)(2)(bpy)(2)(MeCN)(2)](BF4) (14) in high yield. The cation of 14 may also be generated by controlled potential electrolysis of 6a in MeCN at -0.99 V and by heating of a solution of 6a or 6b in alcohol.