Regarding the complex NiCO4, false statement is

It is a diamagnetic, tetrahedral complex;Back bonding occurs due to the donation of an electron pair from metal to anti bonding pi molecular orbital of CO;M-C bond acquires double bond character;C-O bond length will be intermediate of 2 and 3.Thus the C-O bond in  NiCO4 is longer than in carbon monoxide (bond order 3);