Synthesis and structure of transition-metal-bound Phosphazenes derived from phosphazene anions

Article abstract of DOI:10.1021/om00142a012

A synthetic procedure has been developed for the preparation of 1-phenyl-1-(carbonylcyclopentadienylmetallo)-3,3,5,5- tetrachlorocyclotriphosphazenes (7). These are prepared by the interaction of lithium (1-phenyl-3,3,5,5-tetrachlorocyclotriphosphazen-1-yl)triethylborate (1b) with MCp(CO)_nI (Cp = η⁵-C₅H₅; M = Cr, Mo, W, n = 3; M = Fe, Ru, n = 2) in tetrahydrofuran in yields ranging from 15% to 100%. Species 1b is in equilibrium with lithium 1-phenyl-3,3,5,5-tetrachlorocyclotriphosphazene (5), a reactive species, with a phosphorus(III) center. The phosphorus (III) center in 5 reacts with CrCp(CO)₃I, MoCp(CO)₃I, WCp(CO)₃I, and RuCp(CO)₂I by a carbonyl substitution pathway to give a thermally unstable anionic metallophosphazene, 6, in competition with the formation of 7. The structural features of 7 were examined by means of X-ray crystal and molecular structures of N₃P₃Cl₄PhMCp(CO)_n (M = Cr (7a), Mo (7b) W (7c) n = 3; M = Fe (7d), Ru (7e), n = 2). Crystals of 7a are monoclinic of space group P2₁/n with a = 14.911 (1) A?, b = 8.618 (2) A?, c = 16.544 (3) A?, β = 93.78 (1)°, V = 2121 (1) A?³, and Z = 4. Crystals of 7b are triclinic of space groups P1 with a = 8.447 (3) A?, b = 9.084 (4) A?, c = 14.682 (2) A?, α = 75.54 (2)° β = 76 15 (2)° γ = 75.87 (4)°, V = 1038.8 (7) A?³, and Z = 2. Crystals of 7c are triclinic of space group P1 with a = 8.425 (3) A?, b = 9.086 (3) A?, c = 14.628 (5) A?, α = 75.40 (3)°, β = 76.05 (3)°, γ = 75.81 (3)°, V = 1031 (2) A?³, and Z = 2. The structure of 7c was found to be analogous to that of 7b and thus was not fully solved. Crystals of 7d are monoclinic of space group P2₁/n with a = 8.113 (1) A?, b = 17.503 (3) A?, c = 14 215 (2) A?, β = 92.45 (1)°, V = 2016.6 (9) A?³, and Z = 4. Crystals of 7e are monoclinic of space group P2₁/n, a = 8.056 (1) A?, b = 17.624 (4) A?, c = 14.417 (5) A?, β = 91.63 (2)°, V = 2046 (1) A?³, and Z = 4.