(a) In 1956, it was concluded on the basis of dipole moment measurements that Cp₂Pb did not contain coparallel C₅-rings. Explain how this conclusion follows from such measurements.

(b) X-ray diffraction studies at 113K show that two cyclopentadienyl complexes of beryllium can be formulated as (η⁵-C₅HMe₄)(kC¹-C₅HMe₄)Be and (η⁵-C₅Me₅)₂Be respectively. The solution¹H NMR spectrum at 298K of (C₅HMe₄)₂Be exhibits singlets at δ 1.80, 1.83 and 4.39 ppm (relative integrals 6 :6 : 1), whereas that of (C₅Me₅)₂Be shows one singlet at δ 1.83 ppm. Draw diagrams to represent the solid state structures of the compounds and rationalize the solution NMR spectroscopic data.