3-(biphenyl-2,2'-diyl)-1-diphenylphosphino-1-(trimethylsilyl)allene, 15, by treatment of 3,3-(biphenyl-2,2'-diyl)-1-lithio-1-(trimethylsilyl)allene with chlorodiphenylphosphine led instead to 3,3-(biphenyl-2,2'-diyl)-1,1-bis(diphenylphosphino)allene, 14.  The proposed mechanism invokes attack on the trimethylsilyl group in 15 by liberated chloride to form a stabilized anion that reacts with a 2nd mol. of the chlorophosphine.  The diphosphine, 14, reacts with di-Fe nonacarbonyl to form monodentate 14-Fe(CO)4 and the chelate 14-Fe(CO)3.  9-Ethynyl-9H-fluoren-9-ol and chlorodiphenylphosphine form 3,3-(biphenyl-2,2'-diyl)-1-diphenylphosphinylallene, which is readily deprotonated by NEt3 to generate a stabilized fluorenyl anion, which reacts with a 2nd mol. of the chlorophosphine to furnish 3,3-(biphenyl-2,2'-diyl)-1-diphenylphosphino-1-diphenylphosphinylallene, 26.  This bis-phosphine-monoxide (BPMO) reacts with di-Fe nonacarbonyl to form initially monodentate P-bonded 26-Fe(CO)4, which loses a carbonyl, allowing the adjacent allene double bond in 26-Fe(CO)3 to coordinate to Fe and leave the phosphine oxide uncoordinated.  In contrast, the BPMO, 26, and (PhCN)2PdCl2 yield the phosphine-coordinated, Cl-bridged dimer 34 and also the chelate 35, in which the Pd is linked to both the diphenylphosphino and diphenylphosphinyl groups via P and O, resp.  Surprisingly, chlorodiphenylphosphine and 1,4-bis(9-hydroxy-9H-fluorenyl)buta-1,3-diyne, 37, do not yield the expected 3,4-bis(phosphinyl)hexa-1,2,4,5-tetraene, 33, but rather the 1-chloro-2-diphenylphosphinocyclobutene, 38, bearing a spiro-bonded fluorenylidene and a fluorenylidene-allene.  All new compds. were characterized by 31P NMR spectroscopy and x-ray crystallog.