Mono-and digerma[n]metallocyclophanes (n ) 1, 2) [(η 6 ,η 6′ -dimethyldiphenylgermane)M] (M ) Cr, 17; V, 18 • ), [(η 6 ,η 6′ -tetraphenylgermane)M] (M ) Cr, 20; V, 21 • ), and [(1,1,2,2tetramethyl-1,2-di-η 6 ,η 6′ -phenyldigermane)Cr] (24) were synthesized by means of lithiation and subsequent reaction with dichlorodimethylgermane or dichlorodiphenylgermane. Metalligand cocondensation of bromodimethylphenylgermane with chromium atoms followed by reductive coupling with lithium naphthalide gave the digermane complex 24. Additionally, the nonbridged derivatives [bis(trimethylgermyl-η 6 -benzene)M] (M ) Cr, 10d; V, 11 • ), [(trimethylgermyl-η 6 -benzene)(η 6 -benzene)Cr] (10m), and [bis(triphenylgermyl-η 6 -benzene)M] (M ) Cr, 14; V, 15 • ) were prepared and characterized by 1 H-and 13 C-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 of 20 were subjected to a structure determination by X-ray diffraction, which disclosed a bending of the sandwich axis from linearity by 14.4°. The strain exerted on the coordinated benzene ring forces a pyramidal structure on the ipso-C leading to a markedly shielded 13 C-NMR resonance. An EPR spectroscopic investigation of the vanadium derivatives reveals an increasing metal to ligand spin delocalization and the appearance of orthorhombic g and A tensors on bending the sandwich axis. While the redox potentials are virtually unaffected, when passing from the unstrained vanadium complexes 11 • and 15 • to the germa[1]vanadocyclophanes 18 • and 21 • , the transient monocationic species of the latter are destabilized dramatically. No evidence of ring-opening polymerization was observed on heating 18 • to 165 °C. Instead, metal-ligand cleavage occurs.
