Nitrosyls, chromium, molybdenum, and

CYCLOPENTADIENYL)NITROSYL chromium, MOLYBDENUM, AND TUNGSTEN COMPLEXES... 

This effect is unusual and, for instance, in the carbonyl and nitrosyl derivatives of chromium, molybdenum, and tungsten there is no shift of the CO or NO stretching bands in the isostructural derivatives with an increasing atomic number. 

The chemistry of the dicarbonyl(7 -cyclopentadienyl)nitrosyl and the chloro-(i7 -cyclopentadienyl)dinitrosyl complexes of chromium, molybdenum, and tungsten [i.e., fT -CsHs)M(CO)j(NO)] and [(i7 -CsHs)M(NO)2Cl] has not been studied extensively, partly because of the various difficulties associated with their preparation. The procedures described below are of general applicability to all three metals and lead to the desired compounds in high yields. The carbonyl nitrosyl complexes are the synthetic precursors of the chloro nitrosyl complexes and so their preparation is described first. 

Dicarbonyl Nitrosyl Complexes Chromium, Molybdenum, and Tungsten 197... 

Chromium, Molybdenum, and Tungsten. Neutron diffraction studies on [Crj-(CO)io(a -D)] at 17 K provide evidence for a four-fold site distribution of the deuterium. A more simple preparation of homo- and hetero-dinuclear complexes from the combination of 17-e species [M(CO)3Cp, (M=Cr, Mo, W) Mn(CO)s Fe(CO)2Cp Co(CO)4 Ni(CO)Cp] has been described. Heating [Cr(CO)2( -C6He)(NCMe)] results in the formation of the Cr Cr complex, [Cr2( -C6H6)2(/M-CO)3], and the antiferromagnetic complexes, [CraCpgCw-S)-(jM-EPh)2], (E = S, Se), have been reported. The preparation of a variety of nitrosyl dimers of chromium, molybdenum, and tungsten has been reported ... 

NO, Nitrosyls, molybdenum and tungsten, 26 132, 133 NOC, Cyanate tungsten complex, 26 42 NOC4H7, 3-Butenamide nickel complex, 26 206 NOC4H , 2-Propenamide, 2-methyl-nickel complex, 26 205 NOC H, Benzoyl isocyanide chromium complex, 26 32, 34, 35 N04ReC16H, Perrhenate, tetrabutylam-monium, 26 391... 

Monomeric species M OR-tert)x have been characterized for titanium, vanadium, chromium, zirconium, and hafnium (x = 4) and for niobium and tantalum (x == 5). With chromium it was found that limiting Cr(III) to coordination number 4 in the dimeric Cr2(OBu )e caused instability and a remarkable facility toward valency disproportionation or oxidation to the stable quadricovalent Cr(OBu )4 (8, 9). In contrast, molybdenum formed a stable dimeric tri-tert-butoxide (Bu O)3Mo=Mo-(OBu )3 which is diamagnetic and presumably bound by a metal-metal triple bond (10, II). Yet another interesting feature of chromium is the synthesis of a stable diamagnetic nitrosyl Cr(NO) (OBu )3 in which the nitric oxide is believed to act as a three-electron donor with formation of a four-coordinated low spin chromium (II) compound (12). The insta-bihty of Cr2(OBu )e and the stability of both Cr(NO) (OBu )3 and Cr(OBu )4 must result from the steric effects of the tertiary butoxo groups since the less bulky normal alkoxo groups form very stable polymeric [Cr(OR)3]a. compounds in which the Cr(III) has its usual coordination number of 6 (octahedral). 

Chromium nitrosyl complexes, [Cr(S2CNR2)3(NO)], are somewhat less thermally stable than their molybdenum and tungsten counterparts heating [Cr(S2CNMc2)3(NO)] in toluene for 3 h leads to the formation of cis-[Cr(NO)2(S2CNMe2)2] and [Cr(S2CNMe2)3] (752). Somewhat contradictory reports siuround the electrochemical behavior of [Cr(S2CNR2)3(NO)]. Connelly and co-workers (752) report that they show no redox chemistry between 1.5 V,... 

O3NSC7HS, l,2-Benzisothiazol-3(2//)-one, 1,1-dioxide, chromium and vanadium complex, 27 307, 309 O3NWC7H5, Tungsten, dicarbonyl(i -cyclopentadienyl)nitrosyl-, 28 196 03N3MoC,2H, Molybdenum,... 

Figures 7,8 shows plots of data for chromium and molybdenum nitrosyl species the slope with El(L) is essentially the same as for non-NO species. Thus, in Figure 7,8 [data from 10,31,32], a value for El(NO) is used which will cause the nitrosyl complexes to fit the correlation line. This yields El(NO + ) = 2.55 - 2.57 for both metal ions. Values in the range 1.2 -1.8, for El(NO" "), have been described by Clarke [33] for some technetium nitrosyl derivatives. This area would benefit from a detailed analysis.

The nitrosyl carbonyls CpM(NO)(CO)2 [M=Cr (21, 7S), Mo (57), W (19)) can be made by the action of nitric oxide on [CpCr(CO)3]2, [CpMo(CO)3] , or [CpW(CO)3] , respectively. The chromium complex undergoes a Friedel-Crafts acetylation to give (CsH4COCH3)Cr(NO)(CO)2 (21). A series of molybdenum complexes CpMo(NO)l2L [L = PPh3, P(OPh)3, py, and bipy] has been made from L and [CpMo(NO)l2]2 (57). The cationic manganese species [CpMn(NO)(CO)2], obtained by the action of nitrite and acid on CpMn(CO)3, can be precipitated as the yellow hexafluorophosphate salt (51). With sodium borohydride this affords [CpMn(NO)(CO)]2 which probably contains bridging NO groups (see below) (58). The complex [CpMn(NO)S2] is probably similar in structure... 

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