Dinuclear site adduct

Love and coworkers have reported a series of dinuclear cobalt complexes derived from a rigid binucleating macrocycle H4L 18 as shown in Fig. 26 (150). The synthesis of the dicobalt complex [Co2(L18)] (36) was achieved by an anaerobic transamination reaction between H4L18 and [Co(thf) N(SiMe3)2 2] in THF. The unsaturated species 36 forms a bis(pyridine) adduct, 36 py2 (py — pyridine), which has a cleft-like structure reminiscent of pacman diporphyrin complexes (151,152). Both cobalt ions are square pyramidal, with Col and Co2 displaced out of the N4-basal planes by 0.17 and 0.18 A, respectively. The apical sites are occupied by pyridine nitrogen atoms that are exo and endo to the cleft. Interestingly the endo pyridine is canted and reflects the... 

Tyrosinase is the oldest known monooxygenase that catalyzes monophenol oxidation to quinone [34, 109]. It contains a dinuclear copper site which is very similar to that found in hemocyanin, a ubiquitous oxygen carrier for invertebrates [110-112]. The dioxygen adduct of tyrosinase is known to exhibit unusual spectral characteristics which are similar to those of the dioxygen adduct of hemocyanin (1) unusually low v(O-O) assignable to a symmetric peroxide ascertained by resonance Raman spectroscopy [113], (2) unique intense absorption bands seen at 350 nm ( , -20000 cm M ) / 2Cu and ca. 580 nm... 

Last but not least, a carbene adduct of SiBr4 (175) with pentacoordinated Si atom (with carbene ligand in equatorial position and Si-Br bond lengths of 2.24 and 2.38/2.41 A for equatorial and axial sites, respectively) [108] and a dinuclear pentacoordinated bromosiUcon compound (176) with a central Si2N2 four-membered cycle and rather short axial Si—Br bonds (ca. 2.28 A) [340] have been reported. 

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