COORDINATION CHEMISTRY OF CYCLAMPHOSPHORANE. ACCESS TO TRANSITION-METAL CYCLAMPHOSPHORANIDES. CRYSTAL AND MOLECULAR STRUCTURE OF CpMo(CO)2(CYCLAMPHOSPHORANIDE)

Article abstract of DOI:10.1021/ja00266a009

In solution, cyclamphosphorane 1a is in equilibrium with ca. 20percent of the open cyclamphosphine form 1b.This equilibrium can be shifted under the action of transition-metal derivatives to yield adducts of 1b.Three situations were encountered: (i) With Fe(NO)2(CO)2, only phophorus-bound adducts were formed; both Fe(NO)2(CO)(1b) and Fe(NO)2(1b)2 were isolated. (ii) The phosphorus- and nitrogen-bound chelates 6 were obtained under the action of 2. (iii) With CpM(CO)3Cl, a more complex situation was found: with M = W, one CO was substituted to yield a mixture of diastereoisomeric neutral P-bound cis adducts, 8; under the action of NaBPh4, the NH site quantitatively displaced the chloride ion to give a mixture of phosphorus- and nitrogen-bound diastereoisomeric salts, 10; when M = Mo, the reaction yielded a 3:1 mixture of the neutral P-bound only and of the ionic P- and N-bound diastereoisomers; this mixture can also be quantitatively converted to the ionic diastereoisomeric chelates, 9.Complexes 3 and 4, which formally contain the cyclamphosphoranide ligand 13, i.e., a 10-electron valence-shell, monoanionic, 4-coordinated phosphorus (III) species, were isolated in over 90percent yields from the reaction of the cationic chelates 9 and 10 after abstraction of the N-borane proton by LiMe.Only one diastereoisomer (an enantiomeric pair) appears to form.The phosphoranides could not be obtained directly from LiMe and the neutral adducts 7a or 8, in which the NH site is not coordinated.The phosphoranides are thermally fairly stable (dec 150 and 200 deg C) and only moderately air-sensitive.They are characterized by high-field 31P chemical shifts, ca. 173 ppm upfield from those of their precursors 9 and 10.Adduct 3, (C5H5)Mo(CO)2(C10H20N4P), crystallized in the monoclinic space group P2₁/n with a = 13.736(1) Angstroem, b = 9.354(2) Angstroem, c = 15.577(2) Angstroem, β = 113.05(1) deg, and Z = 4.Its most notable features are the 5-connected character (i.e.,phophoranide nature of the metal-bound phosphorus atom, with a short (2.44 Angstroem) Mo-P bond), the coordination of a P-bound nitrogen atom to the same molybdenum (2.22 Angstroem) to form a cycle, the long P-N bond within this cycle (1.85 Angstroem) contrasting with the shortness of the other apical P-N bond (1.70 Angstroem), which compares in length with the equatorial P-N bonds (1.67 and 1.70 Angstroem), the close to planar configuration of the uncoordinated apical nitrogen atom, the close to bipyramidal arrangement of bonds around phosphorus in spite of the five cycles to which this phosphorus belongs, and the unusual negative distortion of this bipyramid on Berry's ideal trigonal-bipyramid/square-pyramid low-energy path.