Metal Complexes of Benzene Derivatives. Germanium in the Periphery of Bis(benzene)vanadium and Bis(benzene)chromium. Synthesis and Str
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- 作者：Christoph Elschenbroich ; Eckhardt Schmidt ; Rolf Gondrum ; Bernhard Metz ; Olaf Burghaus ; Werner Massa ; and S. Wocadlo
- 刊名：Organometallics
- 出版年：1997
- 出版时间：October 14, 1997
- 年：1997
- 卷：16
- 期：21
- 页码：4589 - 4596
- 全文大小：315K
- 年卷期：v.16,no.21(October 14, 1997)
- ISSN：1520-6041
文摘
Mono- and digerma[n]metallocyclophanes(n = 1, 2)[(
6,6'-dimethyldiphenylgermane)M](M = Cr, 17; V, 18
),[(6,6'-tetraphenylgermane)M](M = Cr, 20; V, 21), and[(1,1,2,2-tetramethyl-1,2-di-6,6'-phenyldigermane)Cr](24) were synthesized by means of lithiationand subsequent reaction with dichlorodimethylgermane ordichlorodiphenylgermane. Metal-ligand cocondensation of bromodimethylphenylgermane with chromium atomsfollowed byreductive coupling with lithium naphthalide gave the digermane complex24. Additionally,the nonbridged derivatives[bis(trimethylgermyl-6-benzene)M] (M = Cr,10d; V, 11),[(trimethylgermyl-6-benzene)(6-benzene)Cr](10m), and[bis(triphenylgermyl-6-benzene)M](M = Cr, 14; V, 15) wereprepared and characterized by 1H- and 13C-NMR(10m, 10d, 14,17, 20), cyclic voltammetry (CV) (10d,11, 14,15, 18,21, 24), and EPR spectroscopy(10d+,11,14+,15, 18,21,24+). Crystals of20 were subjected to a structure determinationbyX-ray diffraction, which disclosed a bending of the sandwich axis fromlinearity by 14.4
.The strain exerted on the coordinated benzene ring forces apyramidal structure on the ipso-Cleading to a markedly shielded 13C-NMR resonance. AnEPR spectroscopic investigation ofthe vanadium derivatives reveals an increasing metal to ligand spindelocalization and theappearance of orthorhombic g and A tensors onbending the sandwich axis. While the redoxpotentials are virtually unaffected, when passing from the unstrainedvanadium complexes11 and 15 to thegerma[1]vanadocyclophanes 18 and21, the transient monocationicspeciesof the latter are destabilized dramatically. No evidence ofring-opening polymerization wasobserved on heating 18 to 165 C.Instead, metal-ligand cleavage occurs.
6,6'-dimethyldiphenylgermane)M](M = Cr, 17; V, 18),[(6,6'-tetraphenylgermane)M](M = Cr, 20; V, 21), and[(1,1,2,2-tetramethyl-1,2-di-6,6'-phenyldigermane)Cr](24) were synthesized by means of lithiationand subsequent reaction with dichlorodimethylgermane ordichlorodiphenylgermane. Metal-ligand cocondensation of bromodimethylphenylgermane with chromium atomsfollowed byreductive coupling with lithium naphthalide gave the digermane complex24. Additionally,the nonbridged derivatives[bis(trimethylgermyl-6-benzene)M] (M = Cr,10d; V, 11),[(trimethylgermyl-6-benzene)(6-benzene)Cr](10m), and[bis(triphenylgermyl-6-benzene)M](M = Cr, 14; V, 15) wereprepared and characterized by 1H- and 13C-NMR(10m, 10d, 14,17, 20), cyclic voltammetry (CV) (10d,11, 14,15, 18,21, 24), and EPR spectroscopy(10d+,11,14+,15, 18,21,24+). Crystals of20 were subjected to a structure determinationbyX-ray diffraction, which disclosed a bending of the sandwich axis fromlinearity by 14.4.The strain exerted on the coordinated benzene ring forces apyramidal structure on the ipso-Cleading to a markedly shielded 13C-NMR resonance. AnEPR spectroscopic investigation ofthe vanadium derivatives reveals an increasing metal to ligand spindelocalization and theappearance of orthorhombic g and A tensors onbending the sandwich axis. While the redoxpotentials are virtually unaffected, when passing from the unstrainedvanadium complexes11 and 15 to thegerma[1]vanadocyclophanes 18 and21, the transient monocationicspeciesof the latter are destabilized dramatically. No evidence ofring-opening polymerization wasobserved on heating 18 to 165 C.Instead, metal-ligand cleavage occurs.