“…437 The 1:2 reaction between the phosphaalkene 686 and the substituted o-quinones 77 (R 1 ) R 2 ) Cl, Br; R 1 ) t-Bu, R 2 ) H) proceeds via [4 + 2]-cycloadducts to give the phosphoranes 687. 438 The very reactive phosphorus-metal complexes 688 4 ] in dichloromethane solution to yield the diamagnetic complex 689. 431,432 The molecular structure of 689 (R 1 ) R 2 ) Cl, M ) Pd) has been determined from X-ray analysis.…”