TY - JOUR
T1 - Transition-Metal Methylene Complexes. 57.1The Unusual Structure and Reactivity of the Paramagnetic Trinuclear Cluster Compound (η5-C5Me5) Ir (μ-CO)2Co2(η5-C5H5)2
AU - Herrmann, Wolfgang A.
AU - Barnes, Craig E.
AU - Zahn, Thomas
AU - Ziegler, Manfred L.
PY - 1985/1
Y1 - 1985/1
N2 - The trinuclear cluster compound of composition (η5-C5Me5) Ir (μ-CO)2Co2(η5-C5H5)2(3, Me = CH3) has been synthesized in high yield by treatment of the unsaturated dinuclear precursor (η5-C5Me5)Ir(μ-CO)2Co(η5-C5H5) (1) with the mononuclear bis(ethylene) complex (775-C5H5)Co(' ‘n'-C2H4)2 (2). The bis(ethylene) complex acts as a convenient source of the (η5-C5H5)Co fragment by virtue of the extreme lability of both ethylene ligands. The molecular structure of the paramagnetic complex 3, as established by X-ray diffraction techniques, may be broken down formally into the planar Ir(μ-CO)2Co core of the precursor molecule 1 to which a (η5-C5H6)Co fragment has been added. One intriguing structural feature of the cluster ensemble Co2Ir(μ-CO)2is the coordination mode of the two carbonyl ligands that occupy primarily edge-bridging geometries along the cobalt-iridium bond of the original precursor building block 1; the addition of the extremely electron-deficient (η5-C5H5)Co fragment to the electronically and coordinatively unsaturated complex 1 causes only a minor out-of-plane distortion of the Co(μ-CO)2Ir moiety in the solid state with the interplanar angle between the Co(1), C(1), Ir and Co(l), C(2), Ir planes amounting to 169.8°. The triangular Co2Ir framework exhibits two ordinary metal-metal bonds (d[Co(1)-Co(2)] = 2.359 (1) A and d[Co(1)-Ir] = 2.527 (1) A) and one fairly short, unbridged metal-metal bond (d[Co(2)-Ir] = 2.473 (1) A). The distances between the added (η5-C5H5)Co fragment and the carbonyl carbon atoms are considerably longer (2.435 (6) and 2.393 (5) A) than expected for conventional CO bridges (e.g., d[Co(1)-C(1)] = 1.896 (5) A and d[Co(1)-C(2)] = 1.901 (5) A). The paramagnetism of the 46-electron molecule 3 corresponds to a triplet ground state as proven by an 1H NMR study in the temperature range -93 to +100 °C. Structural degradation of the unsaturated 46-electron cluster occurs when 3 is exposed to oxygen, ethylene, or (η5-C5Me5)Ir(CO)2under mild conditions; the dinuclear precursor molecule (η5-C5Me5)Ir(μ-CO)2Co(η5-C5H5) (1) is cleanly formed in these cases. In contrast, two-electron ligands such as CO and the CH2fragment are incorporated into the trinuclear cluster assembly without degradation of the latter. When 3 is treated with carbon monoxide or diazomethane, respectively, the 48-electron complexes (η5-C5Me5)Ir(CO)[Co(μ-co)(η5-C5H5)]2(4) and (η5-C5Me)Ir(μ-CO2)(μ-CH2)[Co(η5-C5H5)]2(5) are obtained in quantitative yields. In these latter reactions, the Co2Ir core remains intact, with the added ligands assuming either terminal (CO, 4) or edge-bridging (CH2, 5) geometries.
AB - The trinuclear cluster compound of composition (η5-C5Me5) Ir (μ-CO)2Co2(η5-C5H5)2(3, Me = CH3) has been synthesized in high yield by treatment of the unsaturated dinuclear precursor (η5-C5Me5)Ir(μ-CO)2Co(η5-C5H5) (1) with the mononuclear bis(ethylene) complex (775-C5H5)Co(' ‘n'-C2H4)2 (2). The bis(ethylene) complex acts as a convenient source of the (η5-C5H5)Co fragment by virtue of the extreme lability of both ethylene ligands. The molecular structure of the paramagnetic complex 3, as established by X-ray diffraction techniques, may be broken down formally into the planar Ir(μ-CO)2Co core of the precursor molecule 1 to which a (η5-C5H6)Co fragment has been added. One intriguing structural feature of the cluster ensemble Co2Ir(μ-CO)2is the coordination mode of the two carbonyl ligands that occupy primarily edge-bridging geometries along the cobalt-iridium bond of the original precursor building block 1; the addition of the extremely electron-deficient (η5-C5H5)Co fragment to the electronically and coordinatively unsaturated complex 1 causes only a minor out-of-plane distortion of the Co(μ-CO)2Ir moiety in the solid state with the interplanar angle between the Co(1), C(1), Ir and Co(l), C(2), Ir planes amounting to 169.8°. The triangular Co2Ir framework exhibits two ordinary metal-metal bonds (d[Co(1)-Co(2)] = 2.359 (1) A and d[Co(1)-Ir] = 2.527 (1) A) and one fairly short, unbridged metal-metal bond (d[Co(2)-Ir] = 2.473 (1) A). The distances between the added (η5-C5H5)Co fragment and the carbonyl carbon atoms are considerably longer (2.435 (6) and 2.393 (5) A) than expected for conventional CO bridges (e.g., d[Co(1)-C(1)] = 1.896 (5) A and d[Co(1)-C(2)] = 1.901 (5) A). The paramagnetism of the 46-electron molecule 3 corresponds to a triplet ground state as proven by an 1H NMR study in the temperature range -93 to +100 °C. Structural degradation of the unsaturated 46-electron cluster occurs when 3 is exposed to oxygen, ethylene, or (η5-C5Me5)Ir(CO)2under mild conditions; the dinuclear precursor molecule (η5-C5Me5)Ir(μ-CO)2Co(η5-C5H5) (1) is cleanly formed in these cases. In contrast, two-electron ligands such as CO and the CH2fragment are incorporated into the trinuclear cluster assembly without degradation of the latter. When 3 is treated with carbon monoxide or diazomethane, respectively, the 48-electron complexes (η5-C5Me5)Ir(CO)[Co(μ-co)(η5-C5H5)]2(4) and (η5-C5Me)Ir(μ-CO2)(μ-CH2)[Co(η5-C5H5)]2(5) are obtained in quantitative yields. In these latter reactions, the Co2Ir core remains intact, with the added ligands assuming either terminal (CO, 4) or edge-bridging (CH2, 5) geometries.
UR - http://www.scopus.com/inward/record.url?scp=0347572620&partnerID=8YFLogxK
U2 - 10.1021/om00120a028
DO - 10.1021/om00120a028
M3 - Article
AN - SCOPUS:0347572620
SN - 0276-7333
VL - 4
SP - 172
EP - 180
JO - Organometallics
JF - Organometallics
IS - 1
ER -