Inorganic Chemistry p. 319 - 329 (1982)
Update date:2022-08-04
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Reactions of the (norbornadiene)metal tetracarbonyls C7H8M(CO)4 (M = Cr, Mo, and W) with the ligands RN(PF2)2 (R = CH3 and C6H5) give either the chelates RN(PF2)2M(CO)4 or the monoligate monometallic complexes [RN(PF2)2]2M(CO)4 (M = Cr, trans isomer; M = Mo and W, cis isomer) depending on the reaction conditions. Reaction of CH3N(PF2)2Cr(CO)4 with C6H5N(PF2)2 results in opening of the four-membered chelate ring to give trans-[CH3N-(PF2)2][C6H 5N(PF2)2]Cr(CO)4 containing two different monoligate monometallic RN(PF2)2 ligands. Reactions of the cycloheptatriene derivative C7H8Cr(CO)3 with the ligands RN(PF2)2 (R = CH3 and C6H5) give mer-[RN(PF2)2]2Cr(CO)3 containing one monodentate and one bidentate ligand and the binuclear complex mer-[C6H5N(PF2)2]3Cr 2(CO)6. Pyrolysis of the molybdenum complexes RN(PF2)2Mo(CO)4 at 100-120°C results in extensive rearrangement to give the binuclear complexes [RN(PF2)2]3Mo2(CO)5 (R = CH3 and C6H5) containing three biligate bimetallic RN(PF2)2 ligands. The chromium and tungsten analogues [CH3N(PF2)2]3M2(CO) 5 (M = Cr and W) can be obtained by photolysis of the corresponding metal hexacarbonyls with CH3N(PF2)2 in a 1-1.5/1 ligand/metal mole ratio. Pyrolysis or photolysis of mixtures of the RN(PF2)2 ligands and the metal carbonyls in a 2-2.5/1 ligand/metal mole ratio gives mixtures of the binuclear complexes [CH3N(PF2)2]4M2(CO) 3 and [CH3N(PF2)2]5M2CO in the case of CH3N(PF2)2 (M = Mo and W) and the binuclear complexes [C6H5N(PF2)2]4Mo 2(CO)3 and [C6H5N(PF2)2]5Mo 2(CO)2 in the case of C6H5N(PF2)2 (M = Mo). The infrared v(CO) frequencies in the [RN(PF2)2]4M2(CO)3 complexes indicate one bridging and two terminal CO groups. However, the infrared spectra of the complexes [CH3N(PF2)2]5M2CO (M = Mo and W) and [C6H5N(PF2)2]5Mo 2(CO)2 indicate the presence of only terminal CO groups. The proton and carbon-13 NMR spectra of the CH3N(PF2)2 complexes reported in this paper clearly distinguish between monodentate and bidentate CH3N(PF2]2 ligands. The phosphorus-31 and fluorine-19 NMR spectra of the RN(PF2)2 complexes have been used to estimate the coupling constants |1J(PF)|, |2J(PP)|, |3J(PF)|, and in a few cases |4J(FF)|. Calculation of approximate CO stretching force constants from the combined infrared and Raman v(CO) frequencies of the trans-[RN(PF2)2]2Cr(CO)4 complexes suggests that the ratio between the trans and cis CO stretch-stretch interaction constants is approximately 3 in contrast to the value of 2 usually assumed for this ratio in the standard Cotton-Kraihanzel treatment. With use of this value of 3 the various approximate CO stretching force constants have been calculated for the complexes RN(PF2)2M(CO)4, cis-[RN(PF2)2]2M(CO)4, and mer-[RN(PF2)2]2M(CO)3 reported in this paper.
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Doi:10.1021/jm50001a013
(1985)Doi:10.1007/BF00580035
(1984)Doi:10.1021/ja00368a026
(1982)Doi:10.1021/tx9701743
(1998)Doi:10.1039/jr9350001847
(1935)Doi:10.1021/jo00347a008
(1982)
